# Oral-History:John C. Chato

Chato was born in Budapest, Hungary, in 1929, and moved to the US in 1948. He went to the University of Cincinnati undergrad 1949-54, received his masters at the University of Illinois, and his PhD at MIT. His career has been in heat transfer research of various sorts—he was originally inspired to work in this field by Prof. B. T. Chao at the University of Illinois. His PhD thesis was on convective condensation in horizontal and inclined tubes. He stayed at MIT as an assistant professor till 1964, then returned to the University of Illinois, where he spent the rest of his career.

His research interests have included a way of building a cryosurgical probe, a way of freezing tissue, first used on brain tissue to alleviate Parkinson’s Disease, but then also in eye and cancer surgery. He later figured out the thermal conductivity of biological tissues, such as brains and blood vessel; figured out the thermal regulation and control of astronauts’ spacesuits; figured out where in blood vessels heat transfer occurs (arterioles and venules, not capillaries, as scientists had thought); tried to model blood flow; used heat flow to destroy toe fungus; figured out how long one can sit in a Jacuzzi safely; examined heat exchange in cryogenic systems; researched electrohydrodynamics with Joe Crowley; and researched electron spin resonance imaging. He has spent the last ten years of his career working on condensation again, working at the Air Conditioning and Refrigeration Center here in Illinois. He comments on the effects of computers on engineering, and worries about the damage our modern civilization inflicts on the environment.

JOHN C. CHATO: An Interview Conducted by Frederik Nebeker, IEEE History Center, 11 October 2000

Interview #407 for the IEEE History Center, the Institute of Electrical and Electronics Engineers, Inc.

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It is recommended that this oral history be cited as follows:

John Chato, an oral history conducted in 2000 by Frederik Nebeker, IEEE History Center, Piscataway, NJ, USA.

## Interview

Interview: John Chato

Interviewer: Frederik Nebeker

Date: 11 October 2000

Place: John Chato’s Office at the University of Illinois

### Childhood, family, and educational background

Nebeker:

Where and when were you born?

Chato:

I was born in Budapest, Hungary at the end of 1929 and came to the United States in 1948 right after I graduated from high school.

Nebeker:

Chato:

My father was a civil engineer and architect. I had two uncles who were mechanical engineers. That established my fate very early. From the time I was ten or twelve years of age there was no question but that I was going to become an engineer. The only question was what kind.

Nebeker:

Was that a matter of choice or was it your father’s decision?

Chato:

No, no, no. It was my own choice. I was interested in mathematics and gadgets. I still am, as a matter of fact. I like to fix and work with things. I was lucky compared to many of the students today who come to college without knowing what they want to do. I feel fortunate that I was stubborn enough to stick with engineering. I have never regretted it. I think it’s a great profession. Unfortunately it is a profession that is somewhat undervalued in the United States. It is different in Europe. For instance, in Hungary doctors of medicine were considered the number one profession and lawyers were number two, but engineers were third; determined primarily on the basis of being a desirable son-in-law. We don’t have that perception in this country. I think athletes are number one in the U.S.

Nebeker:

Yes, and lawyers.

### World War II and daily life, education

Nebeker:

Born in ’29, you must remember World War II.

Chato:

Oh yes. I lived through it as a teenager.

Nebeker:

Were there hard times? Were you in Budapest?

Chato:

If one considers two months of street fighting all around as hard times, then yes, definitely. We weren’t doing too badly until 1944 when the Germans finally got tired of Hungarian government’s lack of support. It did not really support Hitler’s desires and efforts to the extent that was expected of it. Therefore German troops were sent into Hungary to kick out the old government and replace it with a real Nazi government under the Hungarian Nazi Party. Things got pretty tough then because we started getting bombed at that time too. We never had any bombing in Hungary before that.

Nebeker:

Was Hungary a German ally?

Chato:

Yes, but it really had no choice.

Nebeker:

Did that make daily life more difficult?

Chato:

Yes. If for instance one was Jewish or had Jewish relatives, it became very nasty. Not that things were good up to that point for Jews or Communists, but when the Germans came in they clamped down and collected the Jews. They transported them to Auschwitz and other places for extermination. In Hungary, because it started quite late – in 1944 – and Budapest was liberated in February of ’45, they didn’t have enough time to carry out all their plans. I think that most of the Jews in the countryside were exterminated or at least taken away, but there were so many Jews in Budapest that many of them survived though many had a pretty rough time.

Nebeker:

Did you have access to outside information? Did you listen to the BBC?

Chato:

Yes. That was illegal of course, but it didn’t stop people with radios. I remember listening to the BBC. I was about fourteen years old at the time.

Nebeker:

Had you learned English at that point?

Chato:

Oh yes. English is my third language. First was Hungarian, German was my second language and English my third. The reason I learned English was to some extent due to the history of my family. My father spent the First World War in the United States – which is an interesting story in itself. He returned home to Hungary and married. In the mid-twenties he brought a coal gasification patent from Hungary and worked with a company in Dayton, Ohio for about two and a half years. My brother was born in the United States at that time. Then they came back to Hungary and I was born there. Consequently, we had a strong connection to the United States. I began learning English around the age of eight. I also took English as my required third language in high school. The BBC always had an English language quiz, and I remember trying to answer the questions. One question that I still remember had to do with the saying, “You can’t make a silk purse out of a sow’s ear.” I couldn’t figure it out, because I didn’t know the word “sow.”

Nebeker:

That was one that stumped you.

Chato:

That’s right.

Nebeker:

Did the war interrupt your schooling?

Chato:

Yes. I stopped going to the gymnasium – which is the classical eight-year high school – sometime in December 1944. Budapest was surrounded on Christmas Eve. At that time we were living on the second floor of a church. We were having a sort of Christmas Eve service with a minister when all of a sudden we heard this boom-boom-boom-boom. The last one blew out the windows. That was the beginning of the Russians’ siege of Budapest that lasted about two months. The Danube runs north-south through the middle of Budapest. The portion in which we lived was the east side, Pest, that surrendered to or was taken over by the Russians on January 18th. Particularly at the small mountain on the west side, Buda, with the royal castle on it, German and Hungarian troops fought until February 13 before also surrendering. Fortunately, it was a very cold winter.

Nebeker:

What was fortunate about a cold winter?

Chato:

It was fortunate because there were so many dead bodies lying out on the street – horses, people, you name it. Had it been a mild winter there would have been a tremendous problem with epidemics. I remember people cutting up the horses for food. Probably the best meat I ever ate in my life was at the end of that February. Things were already settled down and a friend of my father’s gave us a meal with horsemeat. That was after two months with no meat and without much food of any kind.

Nebeker:

Did schooling continue through those couple of months?

Chato:

Oh no, it didn’t. As a matter of fact much of the school was bombed out. I went to the Calvinist (Reformed) High School, which was church-run, and had its own building. When they finally reopened the school, around April, it had one room and one of the windows was still broken. Only a handful of students were there. One funny thing was that I have never seen so many students happy to be back at school again. It was phenomenal. There was no juvenile crime. People didn’t have time to be criminals; they were too busy trying to get food. I remember one student apologizing that he would not be able to come to school the next day because he had to walk to one of the suburbs – because there was no public transportation – and get some food. He was very apologetic because he really wanted to be at school.

### Family move to the U.S.; University studies

Nebeker:

Did you complete gymnasium?

Chato:

Yes. I also entered the Technical University in Budapest in September of 1948, but then left Hungary in November to go to the United States.

Nebeker:

You had just started at the university.

Chato:

Yes.

Nebeker:

How did you come to the United States? Was it a family connection?

Chato:

As I said before my brother was born in the United States, so he was officially able to choose American citizenship. He chose to be an American citizen and went there in ’46. U.S. immigration laws allowed him to bring our parents to the U.S., but not me. Therefore my parents went next, and I was the last installment. I just barely made it. I may not have been able to leave had we waited another month or two. The Communist government was taking over very strongly at that time and didn’t allow young people, particularly professional types, to leave the country. When I got the permit to cross the border – a one-day permit that had to be obtained before leaving the country – the officials thought I wanted a passport. They said, “You can apply for a passport, but you won’t get it.” Fortunately I already had a passport and they were still willing to give me the permit to cross the border. I am certain I was one of the very last young people to leave Hungary legally before the Communists clamped down in 1949.

Nebeker:

Chato:

In Dayton, Ohio. They went back to where my father had worked back in the twenties.

Nebeker:

Did you manage to get into a university right away?

Chato:

Soon after I arrived in the States I started looking for a university. For various reasons, I chose to go to the University of Cincinnati. It was reasonably close to my parents, was reasonably affordable, but it was a co-op school. Therefore, from the sophomore year on the engineering students basically had income. However, the school was so organized that it would only accept new students in September. What I did was, for one term I went to the University of Dayton.

Nebeker:

I see.

Chato:

I started the co-op program at the University of Cincinnati in 1949 and finished in ’54.

### Corporate engineering employment, graduate studies, research lab employment

Chato:

Then I married and came to the University of Illinois with a fellowship.

Nebeker:

I see you received a Masters degree at Illinois.

Chato:

Yes. I got that in 1955. After that I went to MIT with another fellowship.

Nebeker:

Was there a professor at MIT with whom you wanted to work, or was it the reputation of the school that attracted you?

Chato:

It was the school itself. At that time I started working for what eventually became Draper Labs. I think at that time it was called Instrumentation Lab. They were developing and manufacturing gyroscopes. Dr. Draper invented the gyroscopic navigation system in World War II. They offered me a job there and I was working with that.

Nebeker:

How did that job come about?

Chato:

Someone from MIT interviewed me here at the University of Illinois.

Nebeker:

What was your main interest at that point?

Chato:

At that point my interest was in mechanical engineering in a rather vague form. I was co-oping with General Motors at the time. Then Frigidaire Division was still a part of General Motors.

Nebeker:

Was that in Dayton?

Chato:

It was just south of Dayton in Moraine City. They had a huge plant down there that manufactured air conditioners, refrigerators, electric stoves and other big household appliances. I think they had 24,000 people working for them with two shifts a day. When they eventually let go of Frigidaire, General Motors became pretty much automotive and not much else. Frigidaire probably did not make enough profit for them.

Nebeker:

Chato:

Yes. I also worked for them during the summer of ’54 after I graduated from the University of Cincinnati.

Nebeker:

Were you called a refrigeration engineer?

Chato:

I was called a process engineer. I worked on the production line, making different household appliances. At one point I was involved in the manufacture of artillery shells. That was due to a contract Frigidaire acquired from the Army (and regretted from the beginning). It was a big mistake. They should never have done that.

Nebeker:

Did they start doing that during the war?

Chato:

No. This was started maybe in 1953. It was not a good choice, but I wasn’t a manager in those days so it didn’t bother me in the least. It was an interesting job since this was an unusual thing for them. As a co-op I was actually doing whatever a graduate process engineer would be doing – in this case equipment acquisition for the new plant. I was in charge of purchasing firefighting equipment and all that sort of thing for the new plant. In the summer of ’54 I requested a leave of absence to go to graduate school. I decided that at least a year of graduate school would be useful.

### Graduate studies at the University of Illinois; introduction to heat transfer

Nebeker:

Were you still thinking at that point of being a practicing rather than research engineer?

Chato:

Yes. However the University of Illinois “ruined” me for life. I compare my going to graduate school to a guy who lived all his life in a deep well and looked up and there was a little blue circle and that was the world; then when he got to graduate school he climbed out and looked around and sad, “My God, there’s a big world out there I didn’t know anything about.” It really broadened my perspective. I thought I had learned all of what was supposed to be done in mechanical engineering in those days, and one sort of got the feeling, “Gee, I know just about everything there is. Maybe a few more equations I have to go look up in some handbook or something, and that’s it.” I didn’t really get the idea that there is so little that we know and so much more to learn until graduate school.

It also affected me in another way. We had a lot of good professors here, and one of them was Professor B.T. Chao, who was in heat transfer. He and I just clicked from the beginning. I started out in heat transfer – although I hadn’t known much about it before – on the top graduate level. I took a course in heat conduction at the very top that B.T. Chao taught. He was an excellent teacher and very enthusiastic. I loved it: it was full of mathematics, which I liked. I said, “Okay, here it is. Heat transfer is my future.”

I’ve worked in heat transfer pretty much all my life – although what I’d call oddball heat transfer – such as biological heat transfer and electrohydrodynamics with heat transfer. However my Ph.D. thesis was on condensation. Ten years ago we started working in the Air Conditioning and Refrigeration Center here in Illinois. I was asked to join the group that was working with heat exchangers because of the work I had done thirty years previously. So for the past ten years I was back in condensation and evaporation. As a matter of fact I am writing a chapter now on condensation for a Handbook of Heat Transfer.

Nebeker:

That is closely related to heat transfer, isn’t it?

Chato:

It is heat transfer, but it is what I call conventional heat transfer; not the oddball kind.

Nebeker:

I see.

Chato:

“Oddball” heat transfer is where you really have to work with another field, such as biology, physiology or electrical engineering, as with electrohydrodynamics, so that another discipline must be combined with heat transfer in order to do the work well. That’s why I call it “oddball” heat transfer.

Nebeker:

Was it that course at Illinois that made you aware of the field and your interest in it?

Chato:

Yes, both the course and the instructor.

Nebeker:

At that point were you thinking you might want to be a researcher?

Chato:

Yes. I started getting the idea that perhaps this field of research was interesting. There is always something new. I tend to get bored doing the same thing. If I had done nothing but condensation or evaporation, I think I would have been sick and tired of it in twenty years. When I got into bioengineering I had to start worrying about physiology, yet there wasn’t anything engineers learned about physiology. When I got interested in electrohydrodynamics I figured I would have to learn it, but also felt I would be better off finding someone to work with me who already knew it well. I worked with a professor of electrical engineering who wrote a book on electrohydrodynamics and was quite knowledgeable.

Nebeker:

I’d like to get that story.

Chato:

That may be more along your lines.

Nebeker:

Yes. I’ve seen IEEE conferences on that topic.

### MIT and Instrumentation Lab; aerothermopressors research

Nebeker:

You went to MIT in ’55.

Chato:

Yes.

Nebeker:

Tell me a little about the work you did there.

Chato:

I stayed there nine years. I started out in the Instrumentation Lab doing gyroscopic work. That had very little to do with heat transfer. There is some thermal control, stability and all that, but it’s really not the basic part of it. When I got a fellowship from MIT I started taking other courses.

Nebeker:

Did you have a job at the Instrumentation Lab?

Chato:

It was an assistantship. Really all of the students were assistants.

Nebeker:

I see. Was that the form of financial support you received from MIT?

Chato:

Right. I also got a fellowship for a year. Then I started out working for the Ph.D. I started to work on a project that had to do with “aerothermopressors,” a combination of fluid dynamics and thermodynamics. It has to do with the idea that a cold fluid injected into a stream of gas will tend to increase the pressure and therefore could be made into a pump. I believe the Army or Air Force supported that project. I started working on that partly because I always felt that I wanted to do a Ph.D. in something where I had some idea of my own. In those days I was interested in using optical means of measuring droplets. Of course nowadays it’s no problem, but in those days that wasn’t yet well understood.

Nebeker:

You were interested in getting the size of the drop?

Chato:

Yes, size, number, and velocity if possible – general characteristics of droplets in conjunction with this pump using cold fluid injected into a stream of gas. I started working on it, but unfortunately President Eisenhower came around and said we were spending too much money. He cut the Defense Department’s budget, and we were one of the those who were cut off. Thus, I had to scramble to look for something else.

### Convective condensation

Chato:

There was a very small project in the refrigeration lab that had to do with condensation. That project had been running for several years on a very low level with some money for equipment and not much else. It sounded interesting, so I switched to that and eventually that became my Ph.D. thesis.

Nebeker:

Chato:

My chief advisor was Warren Rohsenow, but I also worked very closely with Hesselschwerdt who was in air conditioning and refrigeration.

Nebeker:

What was the topic of your thesis?

Chato:

Condensation in horizontal and inclined tubes.

Nebeker:

Is that a mathematical theory?

Chato:

It was experimental, but also mathematical.

Nebeker:

Did you propose an explanation and then test the proposal?

Chato:

It was a very satisfactory thesis after the fact. I had a lot of trouble with it because at MIT in those days the professors got half of their salaries from research grants. I think they may still be doing it that way. My research grant had no money for anyone, and as a result no one was very interested in what I was doing. That’s how it was. Every time I met with my committee they said something like, “Well, this is interesting. Why don’t you try something else?” Then I would try something else and go back again; then they’d want me to try something else. That went on and on until I got sick and tired of it. Finally I said, “The hell with that committee. I’m going to do what I wanted to do originally –build a condensation setup.”

The original setup was a simulation, an open channel with water added along the side to simulate the condensation added to the tube, in order to look at the hydrodynamics of it. However, I wanted look at the full picture so finally I did that. I squeaked through and got my Ph.D. thesis. Now that condensation work is in textbooks under my name. I think it was one of the first good studies on condensation inside tubes – convective condensation.

### Applications of Ph.D. thesis on convective condensation

Nebeker:

Why is that an important topic?

Chato:

Nearly all heat exchangers in condensers are forced convective units. Of course some have condensation on the outside of tubes, but there are many with condensation inside tubes. Then there’s the fact of vapor shear. That’s not just condensation of vapor on the surface, but is also influenced significantly by the moving vapor. That changes the characteristics of the liquid film on the wall of the tube.

Nebeker:

Was it a better account of the dynamics than existed before?

Chato:

Yes. In fact it’s still about the most accurate model. About fifteen or twenty years after I published, someone sent me a paper for review that was basically the same thing. The summary suggested changing my constant from .555 to .553. I said, “The best contribution of this paper is to show that I did pretty good work.” Now we are doing the condensation and evaporation work with modern means. I always tell my students that when I did my initial work I never had any problem with data acquisition. I had a potentiometer and wrote down the numbers by hand. However now we consistently have trouble with computerized systems. Occasionally a computer will screw up due to a glitch in the software or an electronic disturbance. We have to be very careful checking over our numbers to make sure that the numbers we get from the computer are correct. That amuses me.

Nebeker:

What practical consequence came from having an adequate theory for this process?

Chato:

Better design for condensers. Obviously this was good for condensers where the condensation occurs inside tubes. Large refrigerators frequently have condensation outside of the tubes. There is a cooling medium in the tubes and condensation occurs in a big container or vessel on the outside of the tubes, so that’s a different story. Smaller condensers, like smaller air conditioners, have condensation inside tubes with air cooling on the outside.

Nebeker:

Were those who were designing these air conditioners and other heat exchangers actually working from mathematical descriptions of the process?

Chato:

They had a correlation I gave them, which is a very simple correlation.

Nebeker:

I see. It was easy to use.

Chato:

Yes. The Nusselt number (a dimensionless heat transfer parameter) is a function of one parameter. Period. That’s it. And that made it very easy to estimate the performance. It did not require a great deal of sophistication.

Nebeker:

It was a very useful design tool.

Chato:

Yes. The first confirmation I had that it was something really permanent rather than just a Ph.D. thesis was about ten years later. I was at a heat transfer conference in Versailles, France and we had our reception in the Eiffel Tower. I was going up in the elevator in the Eiffel Tower when a guy came in, looked at my nametag and said, “Professor Chato, I’m glad to meet you.” I think he was from a research institute in the southwest. He said, “We’re using your correlation for our calculations for condensation.” I said, “You made my day.” For a Ph.D. thesis to still be remembered ten years later is out of the ordinary. Now it is quoted in nearly every heat transfer textbook as a fundamental correlation, though it’s not complete. It’s restricted to a particular flow regime, called stratified flow. One thing we have developed here in the last ten years – on condensation and evaporation both – is a calculation process in which knowing a number of the flow patterns is necessary. Correlations have to be made differently for each flow pattern because it’s a much more complicated process. However, it turns out that a limiting case is my correlation. If one goes to very low mass fluxes and low qualities, the results converge right to that solution.

### Employment at MIT and the University of Illinois

Nebeker:

Did you stay at MIT for long?

Chato:

I was promoted to instructor and then assistant professor at MIT. Then in the early sixties all the universities started building up their graduate programs, and young assistant professors at MIT got offers from all over. I decided to look for greener pastures than MIT, and decided on the University of Illinois because of the respect I had for some of the people here, including Professor Chao – my original seducer to heat transfer. I have never regretted that decision. It’s been a great institution for which to work. I found that if I ever felt like complaining about this university, all I had to do was talk to colleagues from other universities. There are patches of green on the other side of the fence, but there are a lot of mud holes too. We have all the green patches in this campus too, and I have no regrets.

### Bioengineering research; invention of cryosurgical probe

Nebeker:

How did your research evolve after the Ph.D. work?

Chato:

Two major changes in direction I took occurred due to happy coincidences. I could call it luck, but maybe serendipity is a better word in that I saw something that I recognized as an interesting opportunity. In 1960 I took a phone call that came in from a doctor at Massachusetts General Hospital who was looking for a heat transfer expert. He wanted to have a brain probe – used for surgery – insulated so that he could cool the tip. The probes were typically about 20-30 cm long and 2 mm in diameter.

Nebeker:

Why did he want to cool the tip?

Chato:

He was working with cerebral palsy, which is somewhat similar to Parkinson’s Disease. The hypothalamus is deep in the brain, and it has been found that if a small part of it is destroyed, the uncontrollable shaking of the patient ceases. It doesn’t cure the disease, but stops the shaking typical of both cerebral palsy and Parkinson’s Disease. He was trying to get to that little particular spot in the brain. When the temperature of the nerves is reduced to below 27°C, they essentially stop functioning – as when fingers exposed to cold get numb. He wanted to insert the probe, turn on the cooling, and see whether or not this would stop the shaking. If it did stop then he could apply rf (radio frequency) current to permanently destroy the tissue.

Nebeker:

I see. This was a way of inactivating it.

Chato:

Yes, temporarily. When that call came in, it was around May and most of the MIT faculty were out, probably consulting. Being a young assistant professor with very little consulting work, I just happened to be in the office and the call came to me. The doctor explained that he wanted to insulate a long tube 2 mm in diameter so that only the tip would be cold. I didn’t think it could be done. When he explained to me why he wanted this, I said, “I think what you really need is a new refrigeration system.” I went on to develop for him what I call “the smallest refrigerator ever built,” and it worked out very well. The cooling tip was 2 mm in diameter and 5 mm in length. That was the evaporator. That’s how I got started in bioengineering.

Nebeker:

The idea was to actually generate the coldness in the brain?

Chato:

Yes. Basically it was an evaporator. I got a patent on that invention. Contrary to what had been done before, I took the warm fluid and sent it down in the annulus between two concentric tubes, which acted as an insulator to the cold vapor that was generated at the tip. The cold vapor came back in the center tube. That was the basic concept. It was eventually converted into a rather successful commercial device, but I didn’t make any money on it. The manufacturer and I usually argued about patent rights.

Nebeker:

What is the name of that device?

Chato:

We call it the cryosurgical probe. Interestingly, I had been primed for such work (bioengineering). I had a friend who graduated in electrical engineering at the University of Cincinnati at the same time I graduated there in mechanical engineering. He went on to Harvard Medical School and we were in Cambridge, Massachusetts at the same time and occasionally we would talk. I always said, “There must be something engineers could do for all these medical doctors who don’t know a damned thing about engineering but are using all these gadgets.” My friend and I talked about bioengineering and whether it could be made into a separate field of engineering. He thought there was a danger of it becoming “a valley between two big mountains.” However, I thought it would be interesting to work as an engineer in the medical field.

Nebeker:

Chato:

No, this was years before that in the fifties. That is why I was primed for it when this telephone call came through.

Nebeker:

I see.

Chato:

That’s how I started, and one thing led to another. Have you heard of the existential pleasures of engineering?

Nebeker:

Yes.

Chato:

The greatest existential pleasure I experienced in engineering was when the doctor showed me a film of a cerebral palsy patient. The patient was conscious during the operation. They have to be conscious in order to see whether or not they are shaking. This film was of a 16-year-old girl who had my probe in her head. When they turned on the probe the shaking stopped; when they turned off the probe the shaking began again. I felt very good about that. I still kick myself that I didn’t ask him for a copy of that film. I would love to have a copy. As medicine progressed cryosurgical probes were eventually replaced by L-dopa, which is a chemical means of accomplishing similar results.

Nebeker:

Was cryosurgery used for that purpose for a time?

Chato:

Yes. Cryosurgery was also used in eye operations, such as in retinal reattachment.

Nebeker:

Is it ever used to destroy tissue?

Chato:

Yes. There were two schools of thought. The doctor with whom I worked liked rf current because it had been used before. However a doctor in New York – who became extremely famous for treating Parkinson’s Disease – used a liquid nitrogen probe and used cold to destroy the tissue. It worked either way. The trouble is that tissue must be brought to very low temperatures in order to be destroyed, and that is not an easy thing to do. It can be done with my probe using a special refrigerant, but usually one must consider going to liquid nitrogen.

Nebeker:

And then you couldn’t go deep enough with a thin probe.

Chato:

Thicker probes were necessary because a vacuum insulation had to be put on the outside. Starting out with cold liquid nitrogen, it couldn’t be used as an insulation to keep the rest of the brain from freezing. Since vacuum insulation was needed, the probes tended to be a little bit thicker – but they worked.

My probe has been used more frequently in eye surgery. For example, in cataract operations one application was to remove the lens very easily by actually freezing it to the probe. The probe would be applied, the lens would freeze and then the frost will actually attach it to the probe so that it could be removed very easily. In its original state the lens is like jelly and very difficult to manipulate. That method was used for a while, but I don’t think it is used much anymore.

Probably the most commonly used cryosurgical protocol is in cancer surgery. For instance, the liver cannot be cut but can be frozen. Therefore when there is cancer in the liver, if it’s in one area the tumor can be frozen with some rather clever techniques. The frozen volume is followed, on line, and when the frozen ball is big enough one can be sure that the cancerous tissue inside has been destroyed.

Nebeker:

I see.

Chato:

It is also used to freeze the prostate for cancer treatment.

### Measuring thermal properties of biological tissues

Nebeker:

After you got that telephone call and worked on that probe, did you continue to work along the same lines?

Chato:

Yes. As a matter fact, it got me started in bioengineering. The next question the doctor asked me was, “If I make the tip 0°C so that it is as cold as it can be without freezing the tissue” – because he wanted to use rf current to create the lesion, not freezing – “where is the 27°C surface going to be?” My first reaction was to ask myself, “What is the thermal conductivity of brain?” – and of course there was no answer to that. That led me to measuring thermal properties of biological tissues.

Nebeker:

Had no one investigated that before?

Chato:

Up to that time there was no way of measuring it accurately.

Nebeker:

Was that because of the big difference between living and dead brain tissue?

Chato:

Yes. It can’t just be sliced and put it into the usual calorimeter type thermal conductivity device. It just doesn’t work. The characteristics of the tissue change very rapidly after “death,” so in vivo studies are much preferred. What happened was, I remembered a final examination in Professor Chao’s course on conduction in which he suggested to use a spherical probe to measure the thermal properties of earth. It didn’t really work too well there, because a hole has to be dug and then filled in again and that hole has different properties than the rest of the earth. I thought of that and said, “When a hypodermic needle goes into the human body, because of its elasticity the tissue will contract around it. Therefore if a small spherical bead is introduced with a needle and the needle is removed from around it, the tissue will close down. Thus the technique could be used to measure the thermal properties of the tissue.”

Nebeker:

Chato:

There are different things the bead can do, but the one I used was the simple concept that if a spherical source is introduced into an “infinite” medium – which essentially it is – and then heat is generated in that spherical bead at such a rate that the temperature is raised to a constant level, and then automatically adjust the power input so that the bead is always kept at the same temperature level; then the process can be modeled with a fairly simple mathematical model. This means that with uniform temperature initially the boundary condition is a step function in temperature that has a very simple solution – and that solution can be obtained for spherical geometry.

Nebeker:

Does that give the thermal conductivity?

Chato:

If the energy input is followed, it doesn’t really give thermal conductivity but gives the equivalent of the thermal diffusivity. It’s really the thermal conductivity and the product of thermal conductivity × density × specific heat that comes out of the theoretical equations. The thermal diffusivity can be obtained separately from the same set of data. The way I was doing it, I got the thermal conductivity well but the diffusivity was too sensitive. There was too much scatter in the data. Then some other people started working on it and improved it. They basically used the same idea except that they corrected for the internal temperature distribution in the bead. I used a thermistor bead, and of course thermistor beads generally are semiconductors with usually a thin glass cover so that they are not really at uniform temperature. What they did was to account for changes in temperature in the bead itself. That gave them better results. The idea of using a bead came from me.

Nebeker:

That question from the brain surgeon got you going on this whole line of research?

Chato:

Yes, that question led me to the research on thermal properties.

### Bioheat transfer research for NASA; spacesuit design

Chato:

Then later, through one of the NASA faculty grants I spent a couple of summers out at NASA Ames in California and got into the thermal regulation and thermal control for astronauts – the cooling of astronauts in the Apollo spacesuits. One thing led to another and I did more bioheat transfer work.

A good example of obtaining important information with simple but effective analysis occurred when I started looking at the heat transfer effectiveness of various blood vessels. The early bioheat transfer models assumed that the most significant heat transfer occurred in the capillaries. I applied well-known heat exchanger analysis to the various kinds of blood vessels in the human body and found that virtually all the heat transfer should occur in the small arterioles and venules; the capillaries should be essentially at the surrounding tissue temperature with no significant heat transfer. That was an important discovery.

Nebeker:

I’m very interested in the engineering science part of this story. Certainly there were heated aviator’s suits in World War II for high altitude flying, for instance.

Chato:

The suits were cooled, actually.

Nebeker:

I think they had an electrically heated suit for some things.

Chato:

Yes, depending on what they were doing. The human body generates heat that has to be removed, and therefore a lot of the pilots needed cooling suits. The first spacesuits on which NASA worked were based on the cooling suits of the Royal Air Force of Britain. A fellow who came from Britain was head of the Biotechnology Division at NASA Ames Research Center.

Nebeker:

I didn’t realize there were also cooling suits at that time. I imagine in the early days people weren’t using much theory in designing these suits for the flyers.

Chato:

They did what they could, but it wasn’t easy. There is no really good analytical mathematical expression to be found that conforms to the human body, though we did a lot of analytical work after we got involved. They already had the concept of cooling the astronauts using liquid cooling through fine tubes directly in contact with the skin’s surface rather than using air, and eventually that was rather successful. The typical Apollo spacesuit was of that type. We did a lot of work here with NASA, analyzing this heat transfer. It is mostly a conduction issue, but with human biological systems one little bugaboo always exists, and that is blood flow. A piece of copper has no blood flow, but humans do. The real difference between a conduction problem in ordinary engineering and a conduction problem in human bioengineering is blood flow. There have been arguments for decades about the best way of going about it – really big arguments.

Nebeker:

Was analyzing what is happening in physical terms a very important thing in designing the NASA spacesuits?

Chato:

I certainly hope so. Here at the University of Illinois we had actually prototypes built that were like NASA spacesuit. I have always bragged about the fact that our “spacesuits” usually cost on the order of $200 whereas the spacesuit made at NASA cost a million and a half. Nebeker: The fact that they want to talk to you suggests that they think your analysis is useful. Chato: They tried some things that I don’t think were ever used. One thing we were looking at for quite some time was whether there would be any advantage in non-uniform cooling, for instance, having the legs and arms cooled more than the torso rather than cooling all parts of the body uniformly with a single cooling source. After all, if one does a lot of work then a lot of heat is generated in the muscles. After further analysis it seemed too complicated in that doing it that way was too heavy. Though it had its advantages, the spacesuit would have weighed too much. I was at a NASA panel a couple of weeks ago and they were saying sending anything into space, regardless of what it is, costs approximately$10,000 per pound. Therefore, saving one pound is equivalent to saving $10,000. And of course that does not include the cost of making the thing, but is just the price of the fuel and machinery necessary to accommodate it. We did a lot of interesting work. One of the basic things we learned through the years was how to model blood flow properly. However that problem is not 100 percent solved. ### Blood flow modeling; measuring high temperature exposure Nebeker: Did you get into that yourself, modeling blood flow? Chato: Yes I did, although the more recent work was done in other places. Nebeker: Was that specifically tied in with this spacesuit problem? Chato: No, it became a sort of general problem in medicine and related to anything from burn studies to cancer treatment using heat. Cancer treatment with heat – hyperthermia - was particularly a big stimulus of research efforts in bioheat transfer, trying to estimate how much heat must be applied to the various parts of the tumor and the associated problem of how best to aim the ultrasonic beam. For instance, in using an ultrasonic generator, the question was how to aim properly and how move it so that it would heat the tissue properly. I’m giving a paper in November titled “Thermal Treatment of Toe Nail Fungus.” I did this with really no money and did it because I had it and got tired of looking at it on my toe nails. My doctor had advised, “I can give you a very expensive pill for which the insurance company will not reimburse you or you can have a very painful operation that entails taking off the toe nail and treating the tissue underneath.” I didn’t want either one and he said, “If it doesn’t bother you, just forget it.” When I was bicycling back from his office I thought, “Well, if the fungus is a living thing, then it must be temperature-sensitive.” I am currently making up a slide that shows my thermal treatment for toenail fungus by simply using hot water. And it works. I don’t have toenail fungus anymore. Nebeker: Amazing. And that’s because you were sort of prepared for this. Chato: Just thinking in terms of the problem and knowing heat transfer. The secret of the treatment is that the fungus must be heated with a minimum of damage to the toe tissue underneath. I looked at it and said, “Well, this geometry is really fairly simple.” As a matter of fact the model is basically one-dimensional heat conduction. I knew that if I did a steady state process it would not work because the temperatures would be too similar. However, a sudden, transient heat application can get the heat transfer looking like curves rather than straight lines. That means that the temperature distribution in the fungus is above the damage temperature level of the fungus, however the temperature of the toe tissue will be lower. A very large temperature gradient is created so that the fungus can be exposed to enough heat to destroy the fungus without destroying tissue in the toe underneath. And apparently it works. One only needs to know and understand the fundamentals. Similarly I did some work to determine what amount of time is safe to spend in a Jacuzzi. That was a nice experiment, by the way. About six subjects including myself sat in a Jacuzzi measuring temperatures. Nebeker: Tell me a little more about that. Chato: That was due to a lawsuit where a baby had been born with cerebral palsy. The parents sued the hotel where the mother stayed at about sixteen weeks of pregnancy. She got in a Jacuzzi when it was rather cool but while it was being filled up with hot water. The parents alleged that the water was too hot and damaged the fetus, because that period of gestation is about the time when the nervous system is developing. The legal counsel asked me what I could say on the matter and I told them I didn’t know; that I would have to look at it and do some analysis. There again the method of analysis was very simple. If one knows the physiology, the analytical work is not trivial but very simple. Therefore I did some experiments with that. Nebeker: Had experiments of that sort been done before on exposure to a high temperature and how it diffuses into the physiology? Chato: Yes, there had been some work but it had never been analyzed. Basically what I did was to analyze it, and was able to show that people can withstand the heat in a Jacuzzi without damage for fifteen minutes maximum, independent whether the individual is big and fat or small and scrawny. Pregnant women should not go in Jacuzzis. Nebeker: Would a fetus be damaged? Chato: We didn’t do that analysis. However it is not good to expose the fetus to any undue temperature rise. The limit of about 2°C is tolerable to people of normal health, but diabetics or those with certain medical problems such as heart problems should not be exposed to it. Nebeker: Fifteen minutes for a person in normal health will not damage tissues or any part of the body? Chato: Right. Nebeker: Has that resulted in Jacuzzi manufacturers adding warning labels or anything like that? Chato: In some states it is mandatory. I think in Florida a sign must be posted. Nebeker: So that anyone who would use it would see the sign. That’s fascinating. Being in the field of heat transfer, you have encountered various medical problems that have benefited from that kind of analysis, and you have done consulting for a lot of different companies. ### Consultant work on multi-stream heat exchangers Chato: Yes. Some consulting was more or less regarding normal heat exchangers. I did some work in heat exchangers that I consider very nice in cryogenics, and that has become somewhat of a standard. Nebeker: Are you referring to heat exchangers for a building? Chato: No, this had to do with cryogenic systems where quite frequently the heat exchangers have more than two fluids. I developed a method to predict the performance of multi-stream heat exchangers, and it worked. I did that as a consultant for Chicago Bridge & Iron Company. If I remember correctly, I was told that the first year they put that into operation they saved phenomenal amounts of money. The problem was when they had bids on big heat exchangers, say twenty feet in length, with three to six streams going through them. The general practice had been to buy the biggest one that suppliers recommended. That didn’t work too well in cryogenics, because in cryogenics quite frequently the fluids need to be separated. A multi-component gas is refrigerated and then separated. If the heat exchanger is too big some of the separations won’t occur where needed because it is going to be either too cold or too warm. One has to be much more careful of the temperature distributions in the heat exchanger. With my system they could better predict performance. Therefore, rather than buying the biggest one they bought one according to calculations based on data manufacturers gave them that indicated a particular heat exchanger would do the job. It was not necessarily the biggest one. When working with an ordinary two-fluid heat exchanger one could get away with saying, “Okay, I’ll make it 25 percent bigger just to be on the safe side.” With the really big heat exchangers, that just doesn’t work. Much more accuracy is needed. Nebeker: That’s very interesting. ### Electro-hydrodynamics; oil pump development Chato: Another field I worked in that was “oddball,” as I told you, was electro-hydrodynamics. Nebeker: How did you get into that? Chato: The Electric Power Research Institute (EPRI) was formed while we worked with its predecessor. The project on which I worked had to do with underground electric cables using oil as a cooling medium. We were looking at the heat transfer, flow characteristics and all that. I took some courses in electrical fields, magneto- and electro-hydrodynamics at MIT. I had some time for extra courses, and even then I was willing to go up to strangers like electrical engineers and ask questions. What happened was that I looked at that project and said, “Here is oil, which is a dielectric fluid. Pumping is not possible with magneto-hydrodynamics, but maybe we could pump with electro-hydrodynamics. Dielectric fluids would be ideal for that.” Nebeker: When was this? Chato: It was in the mid-seventies. I started talking to a professor here named Joe Crowley who actually was working in electro-hydrodynamics, and he was very much interested in this. He was one of two professors in electrical engineering who worked with this, and he wrote a book which I have here. He and I got together and asked the EPRI people to give us some support in development, and we worked on that for several years. Nebeker: Were you working on a pump for oil? Chato: Yes. Essentially we tried to develop a traveling electric field in the oil that would drag whatever electrical “dirt” - so to speak - was in the oil – ions or electrons. And we actually did pump with that. However in the long run it did not work out because it didn’t pump fast enough. Nebeker: Did you have a prototype that worked? Chato: We developed pumps that worked. Nebeker: Did this relate to the heat transfer work? Chato: Yes, very definitely, because ions have to be generated in the system. There are several ways of doing it. One way is to change the temperature dependent properties of the fluid perpendicular to the flow and one way of doing it is to have heat transfer. I said, “Everything is here. It’s an oil and it’s cooling the cable. Therefore it has a temperature gradient, and therefore it must have an electric gradient in it that we need. All we have to do is apply a traveling wave to it and it will work.” The biggest problem, to some extent, is dealing with the 25 kV needed in this electro-hydrodynamics. It’s not a 110-volt job. Nebeker: I see. Chato: Very high voltages. One reason electro-hydrodynamics was never as popular as magneto-hydrodynamics is because the forces are much smaller by comparison. The force per unit volume is much smaller, therefore, high voltages are necessary. One must go as close as possible to the level where the device is going to start arcing. Nebeker: Has this found any applications? Chato: It’s finding applications in other ways, interestingly enough. One of the applications people work on now has to do with a NASA panel I was on, and it has to do with enhancement of condensation and evaporation. The electric field enhances the heat transfer rate in the system. So some researchers are still active in electro-hydrodynamics but not with the underground, oil-filled cable systems. Nebeker: Not as a pump? Chato: That didn’t seem to work out. I think there had been too much potential for breakdowns, because it’s a pretty nasty job pulling those cables through. Three electrodes are kept running in the spiral form around the cable and they must not touch each other because of the high voltage. I think the practical aspects turned out to be a little too difficult to surmount from an economic standpoint as well. Nebeker: Would you also say that the electric field changes thermal conductivity? Chato: No. The change of temperature changes the electric properties of the fluid. That’s what allows the variation and essentially the diffusion of ions into the fluid in order to balance the differences of the electrical properties of the system. Nebeker: Have there been other applications of that effect? Chato: It’s not quite the same, but I wonder if for instance some of inkjet printers operate with some sort of electric field control. I’m not really up on it. We worked a little bit on droplet control on jets to see what could be done with it. What actually stopped our research was Joe Crowley’s decision to go into consulting. He left the university, and that kind of stopped our cooperation. ### Research collaborations; diversity of heat transfer applications Nebeker: It’s interesting that you have worked with people in other fields. Chato: I find it interesting. One learns a lot of new things. Nebeker: I hadn’t through about it before, but heat transfer is involved in an amazing number of things. Chato: You are not kidding. In everyday life we sweat, become uncomfortable and turn on the air conditioner. We do these things to have thermal comfort and to accomplish that transfer needed for our bodies. Of course the basic problem is that we are generating heat no matter what we do, even when sitting still. However in the case of a Jacuzzi the heat has nowhere to go, so the body temperature begins to rise. It is the fact that we generate heat ourselves and not really the fact that we are in a hot environment that causes the body temperature to rise. Nebeker: I read once that getting rid of generated heat is in fact a serious constraint on distance runners. Chato: Oh yes. A person in good condition could outrun a deer, however. The reason is that deer don’t have as good temperature control. They don’t sweat and evaporate it. They can run very fast, but not for very long because they start to overheat and have to stop. If a human can locate a deer, he can run him down. Nebeker: Humans have a much better heat regulation then. Chato: Yes, we do. Some other animals have it, such as dogs. They do most of their cooling with their tongues. Horses sweat, and they can run long distances. I am not familiar with all the physiology of these things, but we have a very good thermal control system and the sweat evaporation is fantastic. It’s a really beautiful cooling medium. For instance I can play tennis in 95 °F weather provided I wear only shorts and shoes. However if I put on a t-shirt I get overheated. If there is a little wind to enhance the mass transfer so that one can get evaporative cooling, it makes a big difference. Temperature is one of the parameters involved in every physical process. One of the biggest problems electrical engineers have in building a chip, for instance, is that it burns out. Then they give it to a mechanical engineer and tell him: “Cool it.” Nebeker: Yes. Chato: That took many years. Nebeker: Have you been involved with heat diffusion in microelectronics? Chato: Sure – until I discovered that everyone else was in it too. I’m serious. I went to a conference on electronic cooling in Hawaii. I was one of many speakers and all the top heat transfer people were there. I said to myself, “This place is full. I’m going to do something else.” Bioheat transfer was certainly an area without that many people in it. Nebeker: Evidently that was such a hot area that it attracted a lot of people. Chato: Bioheat transfer is still a relatively small arena. Even in bioengineering the bioheat transfer area is relatively small compared to bio-fluid-dynamics for instance or biomechanics in general. However I think it is a very important field. ### Electron spin resonance imaging to measure human body temperatures Nebeker: Would you tell me about this other accident that got you interested in biological applications? Chato: Yes. Again that was a question of measuring temperatures in the human body. One nice way would be to use magnetic resonance imaging (MRI). The problem, when I started looking at it, was that there was no thermal signal coming off the magnetic resonance imaging in the big units. It involves cryogenic cooling, with liquid nitrogen cooling a huge superconducting magnet with very large magnetic fields and so on. No useable thermal signals were coming off of that because, although they were temperature-dependent, they could not be separated out from other effects. Nebeker: I see. Chato: At that point it was not good enough for measuring temperatures. I was thinking, “Well, maybe we could do something about it.” One advantage of MRI was that was in a sense developed. Imaging in the human body had been going on for several years at that time. It was very expensive, with equipment that cost maybe four million bucks and the building needed in which to put it costing another five million bucks. It cost over ten million dollars just to put the thing together. I was talking to a colleague of mine who was in the medical school and also had a degree in biophysics. He was working in the area of electron spin resonance (ESR), otherwise called electron paramagnetic resonance (EPR), techniques. We talked about various things, and I told him I wanted to see one of our experts on magnetic resonance imaging so we could look at this temperature measuring problem. And he said, “Why not ESR?” I said, “What the hell is ESR?” He said, “electron spin resonance.” He explained to me that it was similar to magnetic resonance imaging but that instead of looking at the nucleus one looks at the electron. Nebeker: Do electrons respond to magnetic fields? Chato: Yes. The thing is, the momentum of the electron is huge compared to that of a tiny nucleus. I think the ratio – if I remember correctly – is about 600:1. Therefore big superconducting magnets are not needed; rather, just a good electromagnet. Instead of costing five million bucks it would cost$50,000. That was important then. We discussed it and decided, “Yes, this may work. Why don’t we try that?”

Our local bioengineering program had some monies available to hire a graduate assistant part time and we did an exploratory study. We discovered that there is indeed a temperature dependence there that would make this process worth pursuing. Then we applied to NSF, got a grant and got started on it.

That eventually came to the same fate as the other experiment in that the professor with whom I was working left. He went off to Dartmouth this time. People say that people can work together from long distances, but I don’t think that’s really good. I like to be able to get to the guy, go down to the lab and looking at things together. Thus, that experiment just kind of died.

Nebeker:

Why were you interested in a way of determining temperature?

Chato:

If this had worked it would have given a temperature distribution on a continuous basis rather than local. The bead we worked on before that was a fundamental way of measuring temperatures in the human body. We were putting beads in various places so that they gave local temperature measurements. With ESR we would have a complete temperature field.

Nebeker:

Is there currently a good way of mapping the temperature?

Chato:

Not really, no. A very complicated way of doing it had had some development in magnetic resonance imaging. I don’t think it’s practical yet. In other words, the golden fleece has not really been found. Very involved systems are being done. For instance one system has been tried, where there have been implications that it may work, looking at the diffusivity of water in a tissue – which is a function of temperature. That can be measured, because magnetic resonance imaging usually deals with a hydrogen atom and hydrogen has a response that has been used for imaging. That imaging concept is there. The other advantage of magnetic resonance imaging as opposed to electron spin resonance is that it can penetrate the body without trouble. With the current technology it seems apparent that the deepest we can go with the electron spin resonance techniques may be on the order of 3 cm.

Nebeker:

I see.

Chato:

That is not too bad, but it is limited.

Nebeker:

Has electron spin resonance been developed as an imaging technique?

Chato:

No, not to a practical extent yet. However I can say that it was fun working with it.

Nebeker:

Probably an important application will come along.

Chato:

You never know. There are ups and downs. For instance, for various reasons, cryosurgery almost disappeared in the early eighties. One reason was that there was no good way of determining the presence of the ice front in a tissue.

Nebeker:

You couldn’t monitor what you were doing?

Chato:

The way it was, we could not monitor online, and that was a big concern. One of my friends at Berkeley (who happens to be my spiritual grandson – a student of a student of mine) came up with the idea of using ultrasonics based on radar techniques, of getting the reflection from the ice front to monitor it online. That revolutionized the whole concept. First they tried working on liver cancers, and that was successful. Most of the freezing techniques used today are I think still employing this ultrasonic radar technique.

Nebeker:

Cryosurgery has been shown to be worthwhile after all.

Chato:

It made a comeback. Just because something is not working today does not mean it will not be working tomorrow. Someone has a good idea, we have some information on how the thing works, and things can come back into play.

### Heat destruction of tissue

Nebeker:

Have you been involved with the heat destruction of tissue for surgical purposes?

Chato:

Not as such. I was involved in burn damage, but mostly in terms of legal problems.

Nebeker:

What was that work?

Chato:

There were things like, for instance, someone worrying if a certain piece of equipment that has hot air going through it may actually cause a burn on a human body in the case of a patient who is exposed to it.

Nebeker:

This sounds a little bit like your toenail fungus question. You have heat and the question is, “When is it going to damage the tissue?”

Chato:

Right. This was part of a legal case in which I was involved. Eventually it was settled out of court. The question was, “If a certain device with a certain temperature level, with a certain heated fluid going through it gets exposed to the bare skin, is it going to cause burns?” This sort of problem became very important. There is a lot of work being done in the area of burn injuries. I don’t do much consulting in that area, but some of my friends do.

Nebeker:

That’s very interesting.

### Research engineering strategies; computers as research tools

Chato:

My mind tends to jump frequently from one topic to another but I think that is very good for research engineering. I am connecting things with other things very rapidly.

Nebeker:

Your career illustrates bringing together ideas from different areas.

Chato:

One looks at a problem and says, “Wait a minute. This is very similar to another, already solved problem. Maybe the same thing could be used.” Another aspect of it is this business of heat conduction in the human body and various geometries. Electrical engineering has a set of solutions for the electric field equation, which is the same as the heat conduction equation.

Nebeker:

I think that historically a lot of the mathematics was developed for heat diffusion and then taken into electromagnetic theory.

Chato:

Yes. I remember looking at an electrical engineering paper that had to do with a question of the field distribution around buried cable. It was the same problem as the temperature distribution around the buried pipe – same geometry, same everything. For instance, in conjunction with this cooling of underground electric cables, I used the solutions from an electrical engineering paper that was from the twenties. As a matter of fact I modified the same solution to estimate the heat transfer from a blood vessel near the skin surface.

Nebeker:

That’s very interesting.

Chato:

I applied it to the cables with a little bit of modification, and it was the solution. I didn’t have to do anything but apply it.

Nebeker:

That’s very nice.

Chato:

There is one thing I actually worry about with the use of computers. Engineers tend to look at everything from computer-oriented perspective. They forget about the fact that fifty years ago people did some beautiful work without the computer that is still applicable today. Some years ago I did some studies on applications of computers to finite element techniques in fluid mechanics. I discovered that most of mathematics was at least fifty years old. The basic mathematics wasn’t new at all. The only difference is that now we have the little gadget that can use the mathematics and get out the numbers.

Nebeker:

You lived through the period when the computer became an ordinary tool in engineering. How did that influence your area of studies?

Chato:

In many respects it made it easier because more complicated problems could be done. Even the old time analyses in heat conduction had to calculate sometime an infinite series. That sounds very simple, but eighty terms may be needed in order to converge. With a computer it was much easier than by hand. One respect in which it became a little more difficult than before was is in that our experimental techniques now depend on computers. Computers include a lot of possible errors. I think that a lot of people are not aware of that. They look at the computer output and say, “Yeah, that’s it,” but it may not be. We have learned this from experience. Once we tried to find the electrical disturbance in a system for two months because it wasn’t giving the right output. It was obvious that something was wrong. It turned out to be a glitch in the software.

Nebeker:

There certainly is a greater distance between the measurements in the old days and the computer measurements of today. You knew what you were measuring and it was very direct.

Chato:

Right. Of course I didn’t take as many data, but it wasn’t necessary. That data was quite accurate.

Nebeker:

Are there other areas in which you have worked that we haven’t mentioned?

Chato:

I mentioned condensation and evaporation. The multi-flow heat exchanger analysis could not have been done without a computer. That was a very involved system. I had to dig up a great deal of old mathematics that I forgotten in order to make it into a viable system.

Nebeker:

It’s interesting to me that even though you have done a great deal of work in bioengineering you are also working with problems that are completely outside that area.

Chato:

I’ll tell you what. You have to make a choice based on your interests. To achieve a pinnacle in our profession one tends to concentrate in one area and become the expert in that area. Some wag said, “Eventually you know everything about nothing.” I never liked that. Maybe I could have had more fame if I had stuck with condensation and evaporation all my life, since I had a thirty-year hole where I was doing something totally different.

One other thing I did that was very interesting was in natural circulation systems. I may have been one of the very first people to ask the question, “If you have three parallel tubes connected by headers, you heat one and cool a second but have a third one in between that is heated at various levels, which way will the flow go?” I discovered that at low heat inputs it was metastable, that is it could go either way. This means that there is an external determination on the direction of flow. The flow can be reversed if the fluid is pumped in the other direction. Then if the fluid is squirted through the other way, it will go the other way. It will be a totally different flow, but stable. I did that and I published that work around 1964. In the eighties I heard a speaker talk about the analysis of the Three Mile Island accident. A lot of parallel channels were essentially working in natural circulation because the pumps broke down.

Nebeker:

I see.

Chato:

I casually inquired if they saw my paper of 1964. After an embarrassed silence the guy said, “Well, our computers only go back to 1975.” I will be giving a talk in November entitled “Bioengineering B.C. (Before Computers)" that is related to this ignorance of “old” things.”

### Evolution of biomedical heat transfer research

Nebeker:

How has the field of heat transfer in biomedicine grown over the last decades?

Chato:

It has grown considerably. It has never been as big as biomechanics, but has grown very well.

Nebeker:

You did some early papers with such titles.

Chato:

Yes. Certainly with the spacesuit NASA was one of the supporters of this kind of work. Deep sea divers have problems in that area, so that originally some work was done in that area. One of the big drivers of this work has been hyperthermia for cancer treatment. That was supported very strongly, primarily through the National Institutes of Health (NIH).

Nebeker:

Have the people who contributed to this by and large been mechanical engineers? Are they the ones most attracted to these problems?

Chato:

Let me think. Most of the ones I know, probably yes. However some very brilliant medical people worked with it too. They tended to work with an engineer. And of course since then people have been coming out with degrees in bioengineering – though I don’t think bioheat transfer is taught very much. It’s not considered one of the core areas, so that area is still relatively small. I think it’s very important.

One new area is bioengineering that has been going very heavily is on the molecular level. I don’t know where that is going to lead. This is on a molecular and nanoscale level where one worries about the individual cell or even a subcellular size component of the cell. That seems to be a hot issue nowadays and requires a totally different concept of temperature. This is because it is getting into quantum things such as quantum mechanics.

Nebeker:

There are huge molecules such as in polymers.

Chato:

Yes. What is the temperature of one molecule? That has to be interpreted. There is no question that it has an effect. We know that chemical reactions change with temperature, but how is this going to affect a biological system? That’s totally new. I don’t know. I still like to do experiments in the Jacuzzi.

Nebeker:

It sounds really nice to have to subject yourself to that. Is there anything else on which you would like to comment that we didn’t cover?

### Engineering and environmental consciousness

Chato:

A general comment. I hope that engineering is going to continue to be a very interesting field of developing new things that are not screwing up the environment. Pardon me. I worry about how all that we do to the environment is going to eventually demolish our civilization. My favorite scenario for an end to our current technical civilization is that we will discover the ultimate energy source that is just perfect. It’s going to be some form of safe energy in almost infinite supply. Then we find we don’t have enough oil to build the first generator.

I think we ought to be concerned about the environment, because quite frankly – maybe a lot of people don’t realize it – we can destroy our environment for humans. I think life will go on, but it may not be human life. It may be the cockroaches. And I’m not joking. Cockroaches have been around for a long time and have survived a lot of changes. In a sense humans have not adapted as well. We must be very careful what we do, and keep in mind that there is more at stake than simply solving a current problem. We have to look at the overall picture and environmental impact – though I hate to use that term. We must ask ourselves how it is going to influence the place in which we live.

Nebeker:

Yes. Do you think it’s a good thing for engineers to have training in regard to the larger consequences?

Chato:

Yes, engineers and managers. Managers have to realize that there is more involved than profit to a business. A lot of things can be destroyed. I realize that in business there is always the argument that the next quarterly report should be great, but in another year you may be down in a hole because of what you do today. Engineers have to have some understanding of what happens so they can at least say, “Wait a minute. If we do this, we can solve this problem but we are going to run into a helluva lot of big problems somewhere else.”

Nebeker:

Thank you very much.