Dr. Klaus D. Timmerhaus, who passed away February 11, 2011, was well-known in the cryogenics community for a number of accomplishments, including his involvement in the Cryogenic Engineering Conference and for serving as founding editor of the publication “Advances in Cryogenic Engineering,” which he edited from 1954 to 1980. He also co-authored the monograph “Cryogenic Process Engineering,” which is one of the most valuable texts in the field of cryogenics. In recognition of these efforts, Timmerhaus was awarded the Samuel Collins Award in 1967 by the CEC board for outstanding contributions to the field, and was also made a Fellow of the Cryogenic Society of America in 2005.

In addition to his leadership with the CEC, Timmerhaus was very active in the International Institute of Refrigeration and the American Institute of Chemical Engineers. He is the recipient of the IIR Penzer award in 1989 and conference chair of the 2003 IIR World Congress. He has also held leadership posts within the AIChE and received numerous service awards from that organization.

Timmerhaus worked part-time at the National Bureau of Standards and was the author of many data sheets on low temperature properties. He taught courses on cryogenics at the University of Colorado at Boulder for 43 years and served as Associate Dean of Engineering for Research for over 20 years.

Following are tributes to Dr. Timmerhaus from those who knew him or were touched by his legacy.

From Dr. Howard Snyder, University of Colorado at Boulder:
Klaus joined the faculty of the University of Colorado at Boulder in 1953 and spent his entire career here. I was hired, at his urging, in 1968 to augment the reputation of Cryogenics in Boulder established by the National Bureau of Standards and the University.

Klaus was very generous in spending his time helping others. He had many responsibilities. For about 20 years he was the Associate Dean of Engineering for Research, editor of Advances in Cryogenic Engineering from 1954 to 1980, departmental chair, lecturer for two sections of undergraduate courses, consultant/researcher at the National Bureau of Standards one day a week, and held high-level positions in 10 professional societies.
He was instrumental in requiring that all engineering students take a semester of thermodynamics. This was his course. He usually taught two sections, even when he was an associate dean. This is twice the teaching load of most deans. The course is not popular with students, especially with civil and electrical engineers; they do not understand the utility of the material and there were many homework problems each week. I taught a section for five years. The instructors other than Klaus had graders to evaluate the homework. We posted the answers and held several office hours to help students with questions. However, Klaus went a step further. He did not use a grader, corrected all the homework and wrote an explanation of why he considered an answer wrong. During 43 years of teaching he accumulated 48 student-originated teaching awards.

Klaus was the founding editor of “Advances in Cryogenic Engineering” and edited the first 25 volumes single-handedly. This was before personal computers, and any changes required a retyping of the entire manuscript. He requested submissions to be spaced three lines. He edited every line, improving the presentation with handwritten changes between the lines. Sometimes this was an entire rewrite. Klaus’s wife Jean retyped each submission and returned it to the author for approval. Many authors whose native language was not English submitted nearly unintelligible texts. Klaus would ask me, as the other cryogenicist most readily available, to rewrite, if possible, those difficult submissions. Most present-day editors would not spend this much effort and would merely return the manuscript. Klaus took great pride in making all the articles appearing in the journal grammatically correct and readable. He also edited all the proposals for research funds from the College of Engineering when he was associate dean. We often rewrote (retyped) them two or three times.

All Klaus’ graduate students that I have known were unanimous in praising his help in their research. He spent a large amount of time and effort working with his graduate students. He was the chair of my department in the early 1970s during a difficult time. Many of the faculty who were in the department then say that he was the most just and thorough chair that they remember.

Klaus had an intense sense of responsibility. He was associate dean when the present engineering complex at CU was planned and built. He worked with the architects and contractors to ensure that the needs of the various researchers were met. He oversaw the construction with an eye to detail.

At that time we were in the cold war and new public buildings had nuclear shelters. There was a large shelter in the sub-basement of the building. It was stocked with canned food and water and had battery operated lighting. Klaus was in charge of the shelter. My helium liquefier was located here. Klaus visited the shelter once a month, tested the lighting, and drank and ate some canned water and food. He could have delegated this responsibility, but chose to do it himself.

Klaus spent his noon hour in the fieldhouse running with a group of faculty and staff. He won many races. He was the faculty advisor and helped coach the runners of the University field team. He was very generous with his time. Klaus Timmerhaus was an outstanding professor.

From Dr. Glen McIntosh:
The adjectives that define the life of Klaus Timmerhaus are many and include honesty, kindness, generosity, intelligence, thoroughness, intensity, energetic, reliability, frugality and always in a hurry. The only time (that I know of) he fudged just a little bit was his claim to have attended all of the Cryogenic Engineering Conferences. It’s true he was at the first CEC in 1954, but he was not a registered participant. (The name and affiliation of each registered attendee was published in the Proceedings of the 1954 CEC and this list is effectively a historical cryogenic Who’s Who of the times.) But Klaus made up for an unrecognized start by being the mainstay, more than any other person, of the CEC for the rest of his life.

Klaus’ frugality in the affairs of the CEC was legendary. For many years, he insisted on university venues so that those with limited travel budgets could stay in college dorms. But the real kicker occurred in 1956. Arrangements had been made to have the conference banquet in scenic Estes Park, Colorado, but the cost of a wet bar was deemed excessive. So Klaus personally bought all of the booze, beer and wine and arranged to have it served at a nominal cost. I never found out if he broke even on the deal.

Klaus could push, too. The conference committee review of submitted papers and setting up the CEC program was an exercise in endurance with Klaus as task master. He came into his own as the long-time editor of the Proceedings. In 1957, I made the mistake of presenting a paper that hadn’t yet been written. A couple of weeks later, Klaus started hammering on me and didn’t stop until I carried the paper up to his office at the University of Colorado. The paper, on hydrogen liquefier cycles, did get published.

His kindness and efforts to help people showed up dramatically on another occasion. We were doing a design study on removing trace radioactive elements from nuclear power plant off gas streams. Our approach was to feed the air into a miniature air separation plant and then concentrate the radioactive output in the liquid oxygen stream. I called Klaus and asked him about the number of plates required and the recommended operating pressure. Klaus said that he would send a few notes on the subject. Several days later, he sent a fat envelope with the complete process design of the air separation plant. My payback a short while later was to hire one of his outstanding students, the late Dr. Rich Reinker.

Klaus’ crowning CEC achievement was organizing the 50th anniversary of the CEC in 2005. This included a special Old Timers recognition reception, preparation of display posters for each of approximately 50 Old Timers, a special reception limited to these individuals and their spouses and an invited review of The First Cryogenic Engineering Conference by Old Timer Dr. Richard Kropschot.

Dick concluded his remarks with the following statement published in Volume 51A of Advances: “The very existence of the published papers in ‘Advances in Cryogenic Engineering’ (ACE) provided ready access to a wealth of data and design information. We are deeply indebted to Klaus D. Timmerhaus for his almost lifelong contribution as the editor of that publication.”

We are all better for having known Klaus. Flourishing of the CEC and, perhaps, its very survival is substantially due to his efforts.

From Dr. Thomas Flynn, Cryoco, Inc.:
I was Timmerhaus’ first graduate student. When I showed up, he had been there only a couple of years and hadn’t attracted any graduate students. I signed up with him and that’s probably one of the best things I’ve ever done, get him as my advisor. He was really great at it.

We remained partners after that. He and I taught for AIChE for a number of years, teaching cryogenics at their professional development courses. We did that for several years, and it was a very good relationship.

We went skiing together—he was an expert skier—and we went up to Winter Park together. His father had a ski lounge up there called “Timber House.” I stayed at Timber House and Klaus came up and we skied together for a couple of days. We hung together for years after that. I taught some at CU occasionally and never was a professor over there, and I would teach for him when he couldn’t make the classes. I would take them for him, so we hung out together pretty close. I enjoyed his company. He was a good friend and we did a lot of things together for many years.

Klaus’ passing is the end of an era. He edited the proceedings of the cryogenic conference superbly, he really did a good job of it. He must have done that for 25 years, and we had a hard time replacing him when he finally decided to do something else. So he was very instrumental in putting the cryogenic conferences on the map. He arranged to have the proceedings published with a good publisher. He attended all the cryogenic conference board meetings, and was a big contributor to them, adding good ideas to discuss. He did a lot to make cryogenics what it is today by pulling it all together.

It’s hard to overestimate what Klaus did for the field of cryogenics. Too, he was a superb teacher. He really concentrated on teaching when that was not very popular in the university. You were supposed to go get some grants and make some money for the school. He concentrated on undergraduate education. He devoted his life to it—he was a very devoted teacher. He influenced so many people.

Timm was never very good at raising money because he was too bashful to ask for it. I’ve never had that problem. One of his graduate students arrived in Colorado with no financial support and no way to pay for his thesis or anything. I called some friends at NASA about getting a grant for Timmerhaus and the student. Timmerhaus’ reputation, of course, did it. When I said who it was for, they just said sure, they’d do anything to help out Klaus. That was certainly true.

From Laurie Huget, CSA Executive Director:
Klaus Timmerhaus was a long-time member and supporter of CSA. In 2005, CSA bestowed the Fellow Grade on him.
Then-CSA Chairman Joel Fuerst commented thus when presenting the award at the 2005 CEC/ICMC Awards Luncheon: “Professor Timmerhaus has been the recipient of a great number of awards over his many years of service to the cryogenics community as a researcher, teacher and author. His membership in CSA honors the society more than we can hope to honor him; nevertheless we are proud to bestow on him the rank of Fellow of the Society.”

I would like to add that Klaus Timmerhaus was always supportive of CSA and of me personally. He was a fine person as well as a renowned colleague and leader in the cryo community.

From Michael Capers:
I had the privilege of serving on the Board of Directors for the Cryogenic Engineering Conference. One of the first things that I learned after joining the Board was that the holder of all knowledge and history of the organization was Dr. Timmerhaus. Klaus had been there at the beginning, he had devoted hundreds of hours to the success of the organization, and at the critical time in the “early days” when it was not certain if the organization would survive, Klaus and others infused personal funds to the CEC to assure its continued existence.

In my capacity on the CEC Board I was asked to explore the possibilities of establishing a Graduate Scholarship for promising students in advanced cryogenic studies. As this Scholarship did not exist, the process of understanding the legal and financial aspects took approximately two years. The timing for the first award of this CEC Scholarship could not have been more opportune as the 50th Anniversary Cryogenic Engineering Conference meeting was scheduled for Keystone in Colorado. When I and others on the Board contemplated the official name of the CEC Scholarship, it was immediately apparent that it should be named for the person who had given the most to the organization through the years. Although slightly embarrassed by the recognition, Dr. Timmerhaus consented to our idea and the name “The Jean and Klaus Timmerhaus Cryogenic Scholarship.” It was a great honor for me to stand before the CEC organization and award the first Timmerhaus Scholarship award. In a private moment after the award, Klaus expressed to me their appreciation for this honor in their name. It was a privilege to have known him and to know that through this scholarship his good work and deeds will be perpetuated.

From Dr. Ralph Scurlock, Kryos Associates:
I am so sorry to hear that Klaus Timmerhaus has died. He will be greatly missed as a great strength in cryogenics. Back in 1954, he was a major figure in helping keep the NBS Cryogenic Engineering Laboratory from being closed down when the AEC support was being withdrawn. CEL’s immediate response to its predicament was to organize the world’s first Cryogenic Engineering Conference in September 1954 in close collaboration with the University of Colorado. Timmerhaus was, I believe, the Conference Chairman and went on to become Editor of the ACE series for many years thereafter. The consequence of his action was to help turn around the funding and activities of the CEL into an enormous benefit for everyone who followed him into the world of cryogenics. I’m sure many have similar stories of him to tell.

From Dr. John Weisend, FRIB-MSU, CSA Chairman:
My outstanding memory of Klaus Timmerhaus was his dedication to the education of students and to the general advancement of the field of cryogenics. He clearly enjoyed teaching and always felt that it was vital that we continue to attract talented students into the field of cryogenics. Klaus was always interested in answering questions and was willing to help out in any way that he could. He played a major role in the Cryogenic Engineering Conference Board and was the institutional memory of both the CEC and of cryogenics more broadly. Klaus was one of the editors of “Cryogenic Engineering: Fifty Years of Progress.” This book serves as a vital record of US cryogenic engineering over the last half of the 20th century and illustrates both Klaus’ dedication to the field and his belief that we should remember how we arrived at where we are today. This book, along with Klaus’ technical books and all the students he trained over the years, are an important part of his legacy.

From Professor Alexey Arkharov and Nina Komarova, on behalf of the Russian National Committee for the IIR:
It is with deep regret that we received the grievous message that Dr. Klaus Timmerhaus was no more. We have known him for a long time as an active member of the International Institute of Refrigeration. We know him as a first-grade specialist in cryogenics. We know him as a first-grade author of the monograph “Cryogenic Process Engineering.” We know him as a first-grade lecturer at the University of Colorado at Boulder. We have lost one of the most eminent members of the refrigeration community. We miss him very much. We give our condolences to his family and to all our colleagues at the Cryogenic Society of America.

From Professors Guobang Chen and Guangming Chen, Zeijiang University/IIR:
We are distressed to learn of the passing away of Professor Klaus D. Timmerhaus. Please let us express our strong condolences on his death.

More than 30 years ago, Professor Timmerhaus invited me (Guobang Chen) of Zhejiang University, China to study with him at University of Colorado and the National Bureau of Standards at Boulder as a visiting scholar for more than two years. Professor Timmerhaus then made a donation of the publication “Advances in Cryogenic Engineering,” Vol. 1 to Vol. 25, to Zhejiang University. He strongly supported organizing the International Conference on Cryogenics and Refrigeration (ICCR 1989, 1998 and 2003) by the Cryogenics Laboratory of Zhejiang University, which became the real bridge for scientific exchange between Chinese researchers and students and foreign scientists. We are very grateful to Professor Timmerhaus for the spirit of internationalism. We believe that his great spirit and contributions to the Cryogenic Society will be present in our minds forever.

From John Panek, NASA Goddard Space Flight Center:
I’m very sad to hear of Dr. Timmerhaus’ passing. You are sure to hear many, many wonderful stories from people who knew and loved him. He spoke at a CEC luncheon where I got a small award, and his kind words meant so much to me then. I felt like I was walking a foot off the ground! He was a class act all the way.

From William “Irby” Moore, ASRC Aerospace:
We received your “CSA Newsflash” and appreciated the honor you gave him there. He was a major figure in establishing cryogenics as a specific science. I participated in some of the conferences in Boulder and enjoyed working with the early Cryogenic Division of NBS.

From Gerald Groff, Groff Associates/IIR:
He was a wonderful person and great role model for organizational participation. As President of the General Assembly and as a regular attendee at our USNC meetings, he was always most helpful and provided the glue for many years in holding the USNC together.

From Mark Menzer, Intertek/IIR:
Klaus was also a race walker. During an ASHRAE meeting, I was out running and I saw him speed walking. I tried to do what he was doing, but found it impossible. Then I started running next to him and still had trouble keeping up. And he was 30 years older than me!

From Dr. Piotr Domanski, NIST:
I remember Klaus as a very direct, energetic, and friendly person. I never worked with him directly but he seemed to me to have a great passion for what he was doing. I have friendly memories of Klaus from our USNC meetings and from several Purdue Conferences where he chaired different technical sessions in an exemplary way.

From V. Narasimham, ret., Indian Institute of Technology, Kharagpur:
While in service I read some volumes of “Advances in Cryogenics” and the monograph on “Cryogenic Process Engineering” which were very useful in my day-to-day work. The subject was so exciting it was hard to put down—the book was like a suspense thriller novel.

I felt the genius and wisdom of this great personality and his contributions to this exciting new field. I pray God for the peace of this great soul and offer my condolences to his family and other colleagues who adored him.