Bret Kugelmass [00:00:59] We're here today with Bahman Zohuri, who is a professor at Golden Gate University and has also written about... I don't know, what is it? Two dozen books on topics that I'm curious about around nuclear energy, but also a variety of other topics. Bahman, welcome to Titans of Nuclear. 

Bahman Zohuri [00:01:14] Thank you very much for inviting me to your broadcast here. 

Bret Kugelmass [00:01:20] Yeah, absolutely. I came across you because there were a few books that I was just reading in my offtime that you had written, a couple textbooks. It started off with reading a book on compact heat exchangers. But then, very quickly I'm looking through the citations and also found that you had written a whole bunch of other books as well, and so I started devouring those too. Your topics include everything from thermohydraulic analysis of nuclear reactors, thermodynamics, combined cycle efficiency, advanced small reactors, compact heat exchangers... That was the area that got me in, a couple books on that. And you also do heat pipe design, you do some fusion. And that's all just within the nuclear section, but you also cover a few other topics as well. 

Bahman Zohuri [00:02:11] Yeah, pretty much. I covered most of the A to Z related subjects to nuclear engineering and the nuclear industry, which includes both fission and fusion. Originally, my background and education... It was fusion, but I got interested into the fission as well because fusion for a while went to a halt. That's why you better switch and move on. 

Bret Kugelmass [00:02:38] Actually, can we talk about your background a little bit? Let's start off with where did you grow up to begin with? 

Bahman Zohuri [00:02:43] I grew up in Iran and left that country around 1970. I came to United States for my education under the previous regime. We were selected by our previous government to specifically come to certain universities in the United States to get our education and get back to our old country. Because Iran at that time was very ambitious to get its hand on nuclear weapons, so we were particularly selected to come and get educated in that arena. 

Bret Kugelmass [00:03:17] Okay, so they send you out here and then what happened? 

Bahman Zohuri [00:03:20] Then of course, once I almost finished my second PhD at the University of Illinois, revolution happened there. Without your consent; nobody asked my opinion. Yet, I got a letter from a new government that they were not interested in having us back because the statement was we were too Americanized. And I said, "Fine, I'll stay where I am."

Bret Kugelmass [00:03:44] Wow, wow. And does that mean you weren't able to see your family anymore? What was the ability to to least travel back and forth like?

Bahman Zohuri [00:03:51] I never left the US when I came here because after that episode that happened... We ended up staying, a few of us ended up staying, including me. We got absorbed by the US government into certain sectors of government. I got involved in a lot of classified stuff so naturally, I couldn't go back anymore, nor do I have any desire to go back. 

Bret Kugelmass [00:04:16] Yeah, yeah, yeah. Well, we're glad that we got the genius imported here. Sometimes it doesn't always go that way. Sometimes we send our best and brightest back, but at least we got to keep you. 

Bahman Zohuri [00:04:28] You know, a lot of folks are leaving. An exodus of brains is in process of leaving that country, which is a huge asset they are losing. But if that's their feeling, so be it. 

Bret Kugelmass [00:04:39] Yeah, yeah, yeah. Okay, so the topic of your studies... Actually, first let me ask... You write a lot of books. Why write so many books as opposed to writing papers or as opposed to just teaching? Where does the drive to publish these comprehensive textbooks come from? What are you trying to accomplish on top of the existing literature? 

Bahman Zohuri [00:05:04] When I was growing up in Iran, I went to my high school there and first year of college before they decided to send me to the US to go to the best of the best schools here at that time. The Shah of Iran had a lot of contracts with universities such as MIT, U of I, Caltech and all those. I decided to go to the University of Illinois because when I was growing up, I saw a big protégé of Oppenheimer in that university, a picture of it back home. And I thought, "He is teaching in that school," and I said, "Okay, I want to go to the University of Illinois." And it happen to be one of the top schools when it comes to physics and nuclear engineering particularly. 

Bahman Zohuri [00:05:54] Growing up, I noticed that we need a lot of resources, that we don't have the capability of also translating English to Farsi. And naturally, English was our second language, and I tried to do my best to learn as much as possible to be able to read these books. But then, I found out that some of the books existing in the market at that time were good, but they are very complex, and you need to grow up into it and build up your foundations. So, I had some interest to publish books, particularly when I was working on combined cycle. And as a result, I needed the compact heat exchanger understanding. I decided, "Okay, I'd like to start writing."

Bahman Zohuri [00:06:41] Once I started writing, particularly my first book, which was advanced heat pipe technology that I learned at Westinghouse when I was working for them on a project... I noticed there are a lot of papers, but they are not all combined under one roof. So, that's how I got interested and started writing books. Once I wrote, then publishers see the positive reaction to it and asked me am I interested to write another subject, another subject. So, one comes out and another one. The next thing you know, you wrote a bunch of them. 

Bret Kugelmass [00:07:14] Do you know how many you've written total? 

Bahman Zohuri [00:07:17] Yes, I do. About 64 of them.

Bret Kugelmass [00:07:22] 64? I've got a list of like 20 or 30 here. I didn't realize it was that many. 

Bahman Zohuri [00:07:26] Yes, 64 of them on different subjects, of course. Because my interests got changed going into technology, going into this science. And I know at least 5 of them are being translated in different languages. I know for a fact at least 2 or 3 of them in certain areas have been translated to Chinese and Russians. 

Bret Kugelmass [00:07:51] Wow, wow. Okay, so how long does it take you to write a book? And what's your process? Obviously, you've got it down to a science doing so many. So, what is it? How did you do it? 

Bahman Zohuri [00:08:03] Well, it's just you think about it. And one of my hobbies is bicycling. When I bicycle for a long distance, my brain just goes and I don't feel the distance. That's why I write, because by the time I finish that cycling I do, I come up with ideas and then sit down and put it together. And I start doing research. On average, to answer your question, it takes about a year and a half to possibly two years to go from studying the idea, conceptual idea, put it into production... By the time it goes to peer review and goes back and forth and a selection a publisher... 

Bahman Zohuri [00:08:38] Of course, these days a lot of publishers approach me; I don't approach them. Springer was particular insisting that I write more books for them because few of my books are top sellers for them, although personally I don't like to support them anymore. Elsevier is another one who is continuously approaching me to write books. I wrote at least 10 books for them on different subjects. And another one is Wiley; they are also reaching out. So, I haven't published anything with Wiley. I don't think so. Most of them are Springer, CRC and also, Elsevier. 

Bret Kugelmass [00:09:22] Okay, so if it takes two years from start to finish, but you've written 64, then certainly you must be overlapping how you're doing them. So at any point in time, you've got 3 or 4... 

Bahman Zohuri [00:09:31] Yes, on different subjects. Considering that I'm an old man, my kids are grown up, gone, so I have plenty time on my hands. So, my best friend is my computer, and when I do research my mind really goes. And it keeps me busy because besides watching the news, I don't watch anything else on TV, so I spend my time in front of my screen. 

Bret Kugelmass [00:09:57] Yeah, yeah. And do you have any favorites authors from previous generations maybe who are no longer with us, but who are good for foundational information on this? One I can think of is Sam Glasstone. I've read everything from him.

Bahman Zohuri [00:10:12] Exactly. I was going to say that. I've learned a great deal from his books. And also, a person who I admire and gets a lot of inspiration from Hans Bethe. I love that guy. I went to a lot of his lectures when he was giving them in New York and at his university, Columbia. I think he was there. I was in Rochester doing my post-doc there with the University of Rochester and the Laser Laboratory. I had the opportunity go to listen to him. He really fascinated me at that time, I should say, because he passed away, I think in 2005 or something. He's one of my favorite guys. I love listening to him. I don't know if you know him or not. 

Bret Kugelmass [00:11:05] Not off the top of my head, but I've begun to build my own library over the last six or seven years. I have a few hundred textbooks, almost all on nuclear, so I might have some of his work. You know, Sam Glasstone, I'm just obsessed with his work because I think he's just such a clear writer. And it was at the dawn of the industry, too. I just can't help but transport myself back and pretend I'm a 1950s, 20-something engineer. 

Bahman Zohuri [00:11:38] He was an amazing author. And also, Hans Bethe, if you recall... They always said Oppenheimer is the father of the atomic bomb and Edward Teller is the mother of the hydrogen bomb. And Hans Bethe said, "In that case, I am the child of the atomic bomb." Because he was in the Manhattan Project and he was one of the leaders of that project, and most of the advanced innovation that was created was done by him. Mathematically, he was genius and a strong person. And what a memory he had. I was always amazed with his memory. 

Bret Kugelmass [00:12:18] Amazing. I've just searched him; I've got his name. I'm going to start trying to collect his works. 

Bahman Zohuri [00:12:25] Yeah, he won the 1964 Nobel Prize, I think. A very well-known German scientist who came to the US during the Manhattan Project, one of those Jewish folks who left Europe. 

Bret Kugelmass [00:12:43] Amazing. Okay, let me let me... Out of these topics that you've explored... Let's start with the ones in the nuclear space specifically. Because there are so many others; we could have many other conversations. As a matter of fact, we could probably do three or four conversations just in the nuclear section, so we'll stick there for now and make this at least an overview podcast. Which topic did you learn the most in researching where it wasn't just like a regurgitation of previous ideas in a better, more concise format, but you actually uncovered something that you hadn't learned in your studies when you were putting together the books?

Bahman Zohuri [00:13:18] Well, a lot of my books that I wrote... Certainly, I didn't learn about them during my education. Because most of our classic books were not going to the granule level that I went to in my books because my books are very specific. And when I started writing, I remember the first publisher who approached me was CRC, and then next to them was Springer. And I made a deal with that editor at that time, which was Springer, saying, "Let me write the sequence of the book so we cover from A to Z of the nuclear industry," because there is a lot in the nuclear industry. And even today, when folks graduate from nuclear engineering, even as far as a PhD is concerned, they are not really highly educated, per se, for industrial application. 

Bret Kugelmass [00:14:11] I've noticed that. I've noticed that. So, what's going on there? 

Bahman Zohuri [00:14:18] Sorry I have to jump on some of my colleagues at university, particularly UNM was very disappointing for me. When I was teaching there, I noticed a lot of professors are old and they have no clue what's going on in the industry and they don't want to update themselves as a result. They keep feeding the same old-fashioned stuff that no longer applies, so we might as well get on with it. So, I noticed I have to cover those vacuum areas and be able to feed the books that really helps you to grow up in the industry. If you go to Westinghouse, for example, General Electric, or for that matter, any nuclear and commercial industry, you've got to be up to speed very quick. So, classical books don't bring you to that point. They are particularly disappointed if you have a PhD and you go there and you don't know. 

Bret Kugelmass [00:15:13] Yeah, I mean, I have to say the thing that upsets me the most when I talk to even other nuclear entrepreneurs who maybe have some sort of advanced reactor prototype or advanced reactor concept is that their understanding of materials are as if they're in its purest form at all times. As if you can actually order pure boron or pure lead or pure bismuth or even pure water. And you could just magically put it in your paper reactor and it'll behave according to the perfect physics of that perfect molecule. And they don't understand that in reality, nothing is pure. And that leads to corrosion or all sorts of other challenges. And even the smallest amount of things can... I say this literally and figuratively... Bubble up in your system and become a real problem. Is that one of the challenges that you've seen as well? 

Bahman Zohuri [00:16:10] Yes, exactly. For example, when I got involved with my first job with Westinghouse... They hired me out of my school and put me into connection with a project, which was a liquid metal fast breeder reactor that we were working on. And unfortunately, the Carter administration killed that project. We had no clue what was going on when Three Mile Island took place. And we had no inherent shut down system as a backup to be able to recover from such events. So as a result, the ideal heat pipe came about. How can we use it as a secondary loop for a cooling system to prevent any incident of that nature and be able to recover from it before melting events take place? And as a result, I look at the first idea of the heat pipe, and I came across a paper by a guy named Cotter at Los Alamos, and that's how I saw it as an application to the nuclear industry. 

Bahman Zohuri [00:17:10] And when I started digging in, I couldn't find anything really exactly related to that subject. So. I had to develop my own conceptual ideas and understanding of it. That's why I ended up writing my first book. Although it was not a good publication at that time... I was learning how to publish a book, so I had a lot of errors here and there. But when the second edition of it got published by Springer, my goodness, a lot of it hit. Because it was exactly hitting the same issue I faced myself as an engineer where I didn't have that knowledge. And a lot of folks apparently were in the same boat. 

Bret Kugelmass [00:17:51] Let's focus on heat pipes for a second. What are the main points and concepts about heat pipes that can provide both opportunities for the nuclear sector, but also that are hidden challenges that need to have engineered solutions around some of the things introduced as well?

Bahman Zohuri [00:18:12] Challenges were good at the beginning, but a lot of solution was offered around it. And today, there are no challenges for it. As a matter of fact, it is perfect innovation that you can easily put it into application of the nuclear industry. It doesn't matter whether it's fission or fusion, particular now that you can launch it into space, four percent cooling system. It's a very passive and a closed system that does not need any outside resources in order to be able to function properly so long as you are within an envelope of that design for that particular application. Perfectly, it works. 

Bret Kugelmass [00:18:50] So, heat pipes. A heat pipe is a way to move heat from Point A to Point B. Essentially, you have some sort of coolant... 

Bahman Zohuri [00:19:01] To condenser and vice versa. 

Bret Kugelmass [00:19:03] Exactly. Okay, so you have a heat source and you have a heat sink and you have natural circulation through some sort of piping system. Or, could it even be in a giant pool? What's considered a heat pipe? 

Bahman Zohuri [00:19:14] Basically, think about a cylinder that is capped off on both sides, both ends, and one side is sink, the other one, of course, is dumping the heat and bringing the natural circulation back to circulating. There are four parameters you have to take under consideration when designing a heat pipe to match your particular application. On those four parameters that you have to look at, one is sonic limit, they call it. Your liquid that goes from liquid phase to vapor phase should not reach to that limit. Otherwise, you have choking in within that heat pipe. 

Bret Kugelmass [00:20:04] And does a heat pipe necessitate a phase change, or can you circulate fluid in a single phase? 

Bahman Zohuri [00:20:11] That's where those parameters play. The other one besides sonic limit is entrainment limit, the breaking limit. Those are sort of the things that prevents changing the phase and being able to have natural circulation going on. And then, of course, you have to know which type of a medium you're going to use, whether it's mercury, whether it's sodium, potassium, alcohol. Even in your computer that is sitting in front of you, the laptop or whatever you're using, the heat pump exists there and is not using mercury or sodium. Yet in a reactor, particularly a liquid metal fast breeder reactor, you prefer to use sodium and potassium or sometimes mercury for that matter. So in the computer, you can see acetone or alcohol for that matter. 

Bret Kugelmass [00:21:05] And do the same principles that you would use to analyze a heat pipe system apply if the media is water, like in these naturally circulating reactors? Is that a kind of heat pipe of sorts?

Bahman Zohuri [00:21:17] You could use that. Yes, of course. You want to use the media that is not hazardous into the core of the reactor and causes the core to be contaminated. You need to be, as much as possible, close to what that natural circulation media is. Natural for boiling or light-water reactors that consider boiling, and a pressurized water reactor with water. So, you prefer to use something near that. 

Bret Kugelmass [00:21:47] And have we seen the successful application of heat pipe technology in nuclear reactors? 

Bahman Zohuri [00:21:55] A lot.

Bret Kugelmass [00:21:55] Let's walk through some of that. 

Bahman Zohuri [00:21:58] For fact, the Phénix Project, the French use it after our withdrawl from the liquid metal fast breeder reactor project that Westinghouse was leading. They use heat piping, this technology. And in space, they are using heat pipes. In, of course, industry, a lot of folks are using heat pipes. The computer that is in front of us is a good example of it. 

Bret Kugelmass [00:22:25] Totally. I guess maybe let me ask that question in a little bit different way. Have we seen this applied to any commercial power nuclear power plant designs? Not just research reactors, but let's say, intended for power production? 

Bahman Zohuri [00:22:37] Not that I have seen, except what I've seen in Phénix 2. The French, I heard, used it, yes.

Bret Kugelmass [00:22:45] And given the advantages... And I assume part of the advantage is just eliminating complexity, eliminating pumps in your system for forced convection...

Bahman Zohuri [00:22:54] Any dynamic movement, the less degree of freedom, the better situation you have. 

Bret Kugelmass [00:23:00] Okay, so I guess I'm wondering how come we don't see more? And by the way, I'm a fan of this and I've been fascinated and curious by this technology. How come we don't see it more? There are like 50 new startups for nuclear technology. There have been dozens in the last 20 or 30 years of different reactor designs, even by the big incumbents. How come we don't see a bigger push towards this just as a drive to simplification? 

Bahman Zohuri [00:23:29] My personal opinion is because folks are involved in the new generation... Even going from Gen-III to Gen-IV, the SMRs falling into these categories, you see old timers designing these things. All they do is take the old generation and scale it down and call it an SMR. That bothers me; it does. Because you haven't changed anything. You've got to start a new generation with a new idea of not taking old ideas and massaging it into the new one. That's why a lot of these folks commercially fail. If you look at all pioneering SMRs, such as NuScale, for example. I don't know if you follow the news on them. They've recently been sued because they cannot deliver what they promised they can deliver. 

Bahman Zohuri [00:24:17] For that matter, if you look at companies like even Westinghouse, that AP1000... The AP1000 which is Gen-III, an old pumping system, cooling system... They don't even march to their own drum that we generated and got a patent for a heat pipe at Westinghouse for commercial purposes. I was the pioneer on it. And that they never put it into work. 

Bret Kugelmass [00:24:44] But what about students who might read your books in university and then they grow up to become engineers? 

Bahman Zohuri [00:24:50] If they become leaders, yes. But unfortunately... 

Bret Kugelmass [00:24:55] Have you had any anyone reach out to you and say, "I read your book and I'm trying to start a nuclear company now?"

Bahman Zohuri [00:24:59] For space purposes, yes. I've had a lot of startup companies coming in, but unfortunately they don't have the funding to do it. And any new startup companies I have seen that are less than the size of the General Electric, Westinghouse, X-energy and all those guys, it seems to me they are not following, again, new ideas, new innovative ideas. For example, if we refer to my company cycle book, which is pioneering in that idea of bringing efficiency of producing electricity driven by nuclear sources which is the most efficient way of designing reactors, nobody pays attention. When you're telling them, either they don't understand it or they refuse to accept it. Yet, I had a very good, overwhelming interest from MIT, for example. I don't know if you have heard of Doctor Charles Forsberg?

Bret Kugelmass [00:25:58] Yes, of course, of course. He's quite famous in the sector. 

Bahman Zohuri [00:26:02] Yeah. He referenced my book. And I have had at least 10 citations by him made. "Bahman wrote this book on combined cycle, and that brings efficiency..." 

Bret Kugelmass [00:26:12] Tell us about that. Can you describe the combined cycle system in relation to nuclear power plants, specifically? 

Bahman Zohuri [00:26:18] Yes. Combined is a system that uses... In my case, I am suggesting an open air combined cycle using the Brayton Rankine cycle in order to bring them as far as pinch point is concerned, near each other, to be able to operate within an environment where I don't need to have access to fresh water for the purpose of cooling and so forth, so on and yet using it to be able to produce electricity. And I calculate some analysis based on that. Charles Forsberg, he keeps telling me, "Bahman, I I love what you wrote. Can you massage this thing?" Because originally I did my calculation based on a steadier state approach, and he wants me to go ahead and put a go for transient type analysis, which I don't have time for and the resources. 

Bret Kugelmass [00:27:15] Okay. Yeah, let some PhD student do that for their thesis. Tell me more about this system. Can you describe the fuel, the coolant, the moderator, the extra technologies that need to be added to it? The turbines? Can you just walk through what that looks like? 

Bahman Zohuri [00:27:34] Basically, combined cycle can be used in external aspects of a reactor rather than inside the core. When steam comes out of the reactor going to the turbine and comes back to the heat exchanger and then converts to liquid, goes back to the core, that's the outside where I am interested in using this combined cycle to be able to really do this circulation much faster so you don't need all those cooling towers, fresh water, huge heat exchangers using shell-and-tube technology. That's where the compact heat exchange plays into my... 

Bret Kugelmass [00:28:15] And we'll get to that in a minute. I see the thread of how you got there, but I want to stay on combined cycle for a second. So, you're telling me that we have a reactor and you're circulating water from heat source to heat sink, but that's a closed loop. And what's the coolant in that closed loop typically?

Bahman Zohuri [00:28:31] Cooling is a compact heat exchanger that you're using. It depends on how you're going to use it. 

Bret Kugelmass [00:28:35] Sorry, I meant the coolant. Which fluid are you circulating in this system?

Bahman Zohuri [00:28:39] The steam that gets produced by the reactor and comes to the turbine. 

Bret Kugelmass [00:28:46] Okay, so it can be a normal boiling water reactor. Okay, got it. 

Bahman Zohuri [00:28:51] Either pressurized or boiling. As long as it's a light-water reactor, in this case. 

Bret Kugelmass [00:28:56] Okay, so you have a steam turbine and that produces electricity like normal. Okay. And now you're trying to capture another element of...

Bahman Zohuri [00:29:10] Of the steam. 

Bret Kugelmass [00:29:11] Yeah. So basically, the most you can get in that typical cycle would be, let's say, 35% out of the direct conversion of thermal energy to electrical energy in. How much extra percent can you capture? And walk us through what's the physical equipment in that cycle and how does it make electricity? 

Bahman Zohuri [00:29:31] Depends on the design, how many turbines you want to use and compressors you want to use. Whether you want to use one of them, two of them. My calculations went up to five and I wrote the computer code around it and got better efficiency out of it. And it depends on the wattage of the reactor, whether you're looking at 10 megawatt or 25 megawatt. It depends on also, the nature of the SMR that you're designing. 

Bret Kugelmass [00:29:59] Beautiful, so let's start with an example. Let's say 25 megawatt... 

Bahman Zohuri [00:30:02] 25 megawatt, which originally NuScale was very interested in. And they approached me and they asked me could I come and work for them? In that case, I suggested for a combined turbine and also a heat exchanger for it, compressor and heat exchanger, and put it in a somewhat artistic drawing and wrote the code around it and showed I can jump from 35% as as you mentioned. Typically, a nuclear reactor produces going from nuclear energy to electrical output. Based on the calculation that I did... And as a result, believe it or not, sometimes I deviate to explain... I ended up writing the table of contents for steam, because what I found in thermodynamic books was wrong at the temperature I was interested in. So, I had to generate my own numbers and wrote the code. 

Bret Kugelmass [00:31:00] Okay, I'm going to come back to that point, because I also think that there's a fundamental flaw in thermodynamics textbooks themselves. 

Bahman Zohuri [00:31:08] Exactly. 

Bret Kugelmass [00:31:09] I've always found it insane that they cap the amount of energy that can be captured between a hot well and a cold well to anything except 99% of whatever that energy is. To me, it makes no sense that you're imposing these artificial limitations. Who was this... Was it Carnot? Who limited this and used entropy as an excuse? 

Bahman Zohuri [00:31:34] I think it was Carnot. 

Bret Kugelmass [00:31:36] Yeah, I don't like the Carnot limit. I don't think it makes sense. And I think combined cycle in the oil and gas industry proved that it doesn't make any sense. So, what's going on here? 

Bahman Zohuri [00:31:46] I don't know.

Bret Kugelmass [00:31:48] But it's every textbook. It's every single textbook on thermodynamics, and it makes no sense. 

Bahman Zohuri [00:31:52] That's why one of the driving factors behind me writing that application of thermodynamics in nuclear engineering was exactly because of that. Because I didn't see any thermodynamic book that really deviated from old-fashioned thermodynamics and they didn't fix those numbers. 

Bret Kugelmass [00:32:09] It's like classics. It's like we're even pre-Newton in our understanding of thermodynamics when we stick to this Carnot limit. 

Bahman Zohuri [00:32:16] Yeah. 

Bret Kugelmass [00:32:18] Okay, well I'm glad I found someone. I thought I was crazy. 

Bahman Zohuri [00:32:20] No, no, no. I found out, particular around 650 C to 750 C. I was interested about those steam numbers, and I found them wrong. I thought, "My calculation is wrong." But after I really paid more attention and ran it by a colleague of mine, and we both ended up writing these computer codes and generated them, all of a sudden, boom, everything was coming right on target as far as numbers were concerned. That's why Charles jumped on it right away. 

Bret Kugelmass [00:32:53] Yeah, it's so funny. I feel like I'm looking in a mirror right now. Because I've read these textbooks; I've built my own Excel models. Nothing even too sophisticated, but then I was coming up with theoretical efficiencies even at 300 C that you could get of over 60%. And I'm like, "Where is everyone losing all this energy and just pretending that it's a law of nature?" 

Bahman Zohuri [00:33:12] Yeah. And that's how we found out. When originally I saw Forsberg at Berkeley, for example, under Per Peterson. Some of his students were producing those numbers, and he asked me could I do something about it? I was trying to work with him, but it didn't work out. 

Bahman Zohuri [00:33:37] I did an Excel calculation based on the scenario approach. But then, when you get more sophisticated, you need a code. So, we started writing old-fashioned FORTRAN code. You know, you grew up in that arena. 

Bret Kugelmass [00:33:53] FORTRAN was before my time, unfortunately. 

Bahman Zohuri [00:33:56] Yeah. A lot of my students, when you're talking to them about it, they say, "What language is that? We never heard of it. We'd like a modern language language today."

Bret Kugelmass [00:34:05] In high school, they taught us BASIC first. Basic, then Visual Basic. But then, you go to C, and it's like, you skip over FORTRAN. 

Bahman Zohuri [00:34:11] Yeah, I grew up with FORTRAN and I think I'm a guru of FORTRAN language. To this point, even some defense companies are calling me up and I go consult with them to explain those existing code in those days and say how it works. It's hard to read the code. I mean, Northrop is one of my big clients that continuously asks me to come and work on this particular classified code. And the minute I look at it, "Oh, it's my favorite language. I can understand what this is."

Bahman Zohuri [00:34:46] So anyway, we jumped the efficiency for that particular design that we use, the combination of compressor and heat exchanger as a combined cycle. And by going to a compact heat exchanger, we reduce the pinch point between Rankine and Brayton cycle, we reached efficiency of almost 60%, at least theoretically. That was awesome.

Bret Kugelmass [00:35:16] Real quick, do you need extraction stages from your main turbine in order to run it through these compact heat exchangers, or is it at the very bottom of the cycle that you're doing this? 

Bahman Zohuri [00:35:25] The very bottom of the cycle? 

Bret Kugelmass [00:35:26] Okay, got it. 

Bahman Zohuri [00:35:27] So, that's why it can be either bottom of cycle or top of the cycle. Either way. 

Bret Kugelmass [00:35:32] Got it, got it. And you need compact heat exchangers just because of the amount of fluid that you're going to flow through? You don't want to have a huge array of systems?

Bahman Zohuri [00:35:41] Yes. 

Bret Kugelmass [00:35:42] So, that comes down to a cost. So, you wouldn't need compact if steel was free and machining steel is free, but because you want to make it realistic... 

Bahman Zohuri [00:35:52] Realistic and ROI and total cost of ownership gets reused. 

Bret Kugelmass [00:35:56] Exactly, exactly. 

Bahman Zohuri [00:35:57] That's how we looked at the compact. And when I looked at the first book by London and some other guy out of Stanford, that wasn't giving me enough knowledge and information, yet I learned enough to write my own version. That's how I use my compact heat exchanger there. 

Bret Kugelmass [00:36:16] Yeah. And compact heat exchangers, these are made in production today for all sorts of interesting... 

Bahman Zohuri [00:36:23] A lot of them. A lot of them.

Bret Kugelmass [00:36:25] Which industry uses it the most, would you say? 

Bahman Zohuri [00:36:28] I would say oil companies are using it. Now, they're looking at the space technology to use it, but preferably, they'd rather use heat pipes for that purpose.

Bret Kugelmass [00:36:43] From what I understand about compact heat exchangers, for the same power density, it can be five times as small, maybe even ten times as small. How come all shell-and-tube heat exchangers, given just the weight and all of the welding complexities, why is it not immediately advantageous to replace all shell-and-tubes with some sort of compact heat exchanger? 

Bahman Zohuri [00:37:06] Because a lot of folks grew up into it, and the compact heat exchanger is another innovative approach to it. And for an old timer to really get accustomed to these new technologies, it takes time. 

Bret Kugelmass [00:37:19] Okay, so it's just a matter of inertia. There's no fundamental flaw of the technology itself. 

Bahman Zohuri [00:37:25] No. 

Bret Kugelmass [00:37:27] Compact heat exchanges, are there subcategories of this that we could walk through as well? Are there different techniques to make it a compact exchanger? One I know about is printed circuit heat exchanger. That's one type, right? 

Bahman Zohuri [00:37:37] One type. 

Bret Kugelmass [00:37:37] But are there other types as well? Is there a form of plate and frame that might also... 

Bahman Zohuri [00:37:42] There are at least four or five of them, technologically, that you can design. On top of my head, I don't remember all the technology, but my book has classified them nicely. If you look at my book. I wrote it almost six years ago, seven years ago, something like that. Since I deviated from that technology, my mind went somewhere else, so pretty much, a lot of those details are not at the top of my head, but there are a couple of classifications for compact heat exchangers. Printed one is one of them; that is most common one. And they are very good to do it. 

Bret Kugelmass [00:38:24] Any challenges with boiling inside of a compact heat exchanger? Just a few of these micro channels, could that create some sort of problem in terms of erosion on the channels? 

Bahman Zohuri [00:38:34] As far as erosion, the possibility is there. But going from single phase to dual phase is not there. You try to design it so you don't get into a one-dimensional, two-phase airflow scenario, because that causes choking and things like that you cannot afford. 

Bret Kugelmass [00:38:54] I see. And so, that's maybe a limitation of compact versus shell-and-tube?

Bahman Zohuri [00:38:58] Shell-and-tube even has that problem as well. Then, it depends on what application, what temperature you're trying to use. 

Bret Kugelmass [00:39:05] Yeah. The thing that fascinates me, especially about the printed circuit, is that if you can etch whatever shapes that you want into your channels, perhaps all of these things such as two-phase, you can almost direct how you want it to bubble on a microscopic basis... 

Bahman Zohuri [00:39:25] You can have controllers, yes. 

Bret Kugelmass [00:39:27] Yeah, yeah. I mean, I'm fascinated by it. And it seems to me like it's a new frontier that could be as powerful as any new technology frontier. Because so many of the systems in our daily life are all about just moving heat. Heat exchangers are in every part of our daily life, like everything. So it's like, how are we not investing more in the fundamental engineering of this burgeoning... Not burgeoning; it should be burgeoning. A new industry, a new topic. 

Bahman Zohuri [00:39:59] That's what I'm talking about when we go into SMRs and new generations of these reactors, rather than taking old and trying to scale it down.

Bahman Zohuri [00:40:09] Yeah, I get it. But the nuclear industry has a hard enough time with innovation because the regulators and the governments, they don't want you to be innovative, right? Like,everyone makes innovation hard. But for compact heat exchangers specifically and for printed circuit exchangers, I'm just surprised that the automotive industry or like a million others such as the computer industry, aren't just like embedding tiny little heat exchanger circuits in the structural framing... 

Bret Kugelmass [00:40:31] I have a computer that I'm looking at right now. And it's like a metal surface exterior. And I know it's just a flat aluminum plate. Maybe it's got some holes poked in it for the speaker sound to come out. But why isn't the entire thing a form of compact heat exchanger used to efficiently channel airflow to the circuitry? 

Bahman Zohuri [00:40:54] Eventually, we're going to get there, particularly if you're moving from the classical-type computation to a quantum computing system that we are getting pushed toward. 

Bret Kugelmass [00:41:05] That's going to take so long to get to quantum computing. 

Bahman Zohuri [00:41:07] No, I think we are there, believe it or not. 

Bret Kugelmass [00:41:10] With quantum? 

Bahman Zohuri [00:41:10] Yeah. We're going there because we have no choice. 

Bret Kugelmass [00:41:16] Just because you think because we got down to the three nanometer level? 

Bahman Zohuri [00:41:20] That, and also autonomy that we are looking for and computation that we want to do real-time with all this information coming at you, you have no choice. You've got to get pushed there. 

Bret Kugelmass [00:41:30] You see, I think it's going to be a while for quantum, but I do think artificial intelligence is going to either design it for us or it'll make our current chips so much more powerful by re-architecting them and rewriting a new software layer so you're not re-computing hard things, you're more just like pattern matching and quickly finding solutions.

Bahman Zohuri [00:41:52] Of course, because the old technology of CPUs is not there to match the demand for processing purposes. You've got to go from CPU and GPU and all of those things that it goes. 

Bret Kugelmass [00:42:05] Yeah. Okay, so we've already touched upon at least two of my favorite. So, these are the books that I own of yours. All the ones on compact heat exchangers, heat pipes, and the basic thermohydraulics, thermodynamic analysis, combined cycle. 

Bahman Zohuri [00:42:21] Yeah, that thermodynamic book of mine is one of the books I'm very proud of, at least up to my knowledge and information from Springer. I saw a statistic given to me that it was the number one book sale for them. And today I know Cambridge uses it for teaching, MIT uses it for teaching purposes, that textbook. I'd love to see somebody take my compact heat exchanger book and expand upon it and be able to write further around it. 

Bret Kugelmass [00:42:55] That might be a project that I take on at some point. Right now I'm too busy, but that would be my passion, to expand upon your work for compact heat exchangers. 

Bahman Zohuri [00:43:03] Yeah, let me know because I lost my interest in it because my interest now has gone to a lot of other things. Basically, I write a book around it, particularly when I'm dealing with... My passionate subject these days, dealing with depression and using artificial intelligence to do that and that sort of thing. 

Bret Kugelmass [00:43:25] Like, psychology?

Bahman Zohuri [00:43:27] Human psychology. Because to me, that's a deadlier disease, even worse than COVID that we are facing, depression in this country. And we are losing almost 30,000 folks per year due to the depression. 

Bret Kugelmass [00:43:44] It's way more than that. It's way more than that. Because if you look at the fentanyl crisis and the 100,000 deaths there, you could classify those as depression as well. 

Bahman Zohuri [00:43:53] As well, yeah. Particularly between ages of 14 to 26. And that bothers me a lot because I think I lost my son due to that and I couldn't see it. And I said, "I've got to put my education and knowledge into it." Because when you talking to psychiatrists and psychologists, they don't understand the nature of these things from a physicist's perspective. But for me, learning from them is easier for them to learn my language. So, I'd rather go myself into it and do it because I try to explain to them using technologies and transcranial magnetic stimulation and that sort of thing. When you're talking these sorts of things to them, they say, "Hey, what the hell are you talking about?"

Bret Kugelmass [00:44:36] I know, I know. Yeah, and people tend to forget their passion for learning after they get out of university and then they just... 

Bahman Zohuri [00:44:44] Exactly what's happening to a lot of these old professors.

Bret Kugelmass [00:44:49] Doctors are the worst. They don't change their mind ever. 

Bahman Zohuri [00:44:53] Talking to those old guys, they don't want to learn new technology. I mean, innovation of combined cycle was not easy to push. And still, there is a lot of resistance from industry to it. 

Bret Kugelmass [00:45:06] I know it drives me crazy. But you know what? Actually, it's also kind of cool because that's that's opportunity. Whenever the old school industry stops wanting to investigate or invent or look into something, that's opportunity for some young entrepreneurial, enterprising individual to create great wealth for themselves and for society by really pushing past the old school way of thinking. 

Bahman Zohuri [00:45:35] And by the way, don't hesitate if you come across any errors in any of my books in your journey, I'll be more than happy to hear from you. Because I never get time to go back and see where I missed the ball. 

Bret Kugelmass [00:45:47] Okay, well, I think if you're up for it... I know it took a while for us to get to this. I would love to maybe do a deep dive. Maybe I'll pick a book... This would have to be over the course of several months. Maybe I'll pick a book, I'll read it through, and then we can talk about it just like this, over a podcast, as a way to explore some of the concepts. 

Bahman Zohuri [00:46:04] Sure, absolutely. I am hoping to see that. By leaving a university, particularly something like UNM where I was involved with the nuclear engineering department there... Not seeing a lot of compassion there from professors to support you rather than being an a obstacle in front of you. I said, "The heck with it," and left because you can't fight the entire... If they don't want to learn and they have a shield in front of their brain, there's nothing you can do. I mean, to be honest with you, I'll take a bunch of them and send them back to school and say, "Go get your PhD again. Come back when you're done." 

Bret Kugelmass [00:46:49] Maybe we should do that. Just like with driving licenses, we should send people back every five or ten years. 

Bahman Zohuri [00:46:54] Honestly, that's what I mean. That's what I think. That's what I think. 

Bret Kugelmass [00:46:59] That's great. Well, we're running out of time here, but I want to give you the final word. Are there any high-level thoughts you want to leave our audience? Just because you've looked at so much and I'm just so impressed with the body of work that you've accumulated. Also, how focused it is to my interest area is kind of suspicious. Any final thoughts you want to leave with our audience? Please. 

Bahman Zohuri [00:47:19] Just be open-minded to learn new technology; don't resist. Because you don't want to come to speed, accept folks who are offering better solutions. At least give them a chance and analyze it yourself before challenging ideas. 

Bret Kugelmass [00:47:35] For example, one of the technologies I'm trying to push to industry is using advanced in-core instrumentation to measure power level and water level using fiber optic bragging or FPG, fiber-based grading there. I get a lot of resistance. "Fiber won't work in harsh environment reactors." "Hey, buddy, look at all these studies being done by NASA on exactly the same subject and they're sending the satellite above the atmosphere." That harsh environment is worse than nuclear and the fiber optics can survive such a harsh environment. 

Bahman Zohuri [00:48:17] So, be open minded about it because you can get real-time information without losing any collapse. If any events happening to the reactor as far as power density is concerned, water density is concerned, it gives you the health of the reactor moment by moment without losing any second of information. Particularly with AI behind it, you can process these data much faster. It amazes me. 

Bret Kugelmass [00:48:45] Yeah, yeah, yeah. No, there are so many interesting topics to explore. Okay, then we'll call it a wrap on that. I just want to thank you again for your time. And hopefully, this is the beginning of many conversations. 

Bahman Zohuri [00:48:55] Absolutely. Keep in touch.

‍