Editorial: My Personal Thermal Management Project

June 21st, 2012

It can be an amusing thing to notice how sometimes things come full-circle in our lives. My involvement with heat transfer began in college and continued through grad school and a post doc, as I conducted experiments involving liquid helium, both as a refrigerant and the object of study. Since liquid helium was such a precious refrigerant, a key strategy for achieving these temperatures was to minimize the flow of heat into the coldest part of the apparatus.

Fast forward twenty years to 2001. By that time I had been involved in electronics cooling for ten years, and my wife and I were relocating to San Diego. My previous companies in this field were in Connecticut and Arizona. We were moving to the land of near perfect weather, ocean breezes and palm trees. We knew that we would never again have to live among the weather extremes of heat and cold that we had in our previous locales.

As I was settling into my new job, we began looking for a home in our new location.  This was a painful process that took 6 months, due to the well-publicized challenges in the California housing market.

Imagine our delight when, due to my wife’s detective work, we found a house that was a well maintained, mid-century-modern design, with vaulted ceilings, large exposed wood beams, and a wall of glass providing a panoramic view of Mission Bay from its perch on Mt. Soledad. The doors were all wide open and, thanks to the mild spring day and an ocean breeze, it was very comfortable inside the house, without the assistance of air conditioning— which was a good thing because it had none.

As we were moving into the house in July, we came to the startling realization that our dream home became an oven in the summer months. My inner thermal engineer instantly realized that those very features that attracted us to the house made it very unpleasant during those months with long days of intense sunshine, despite the quite comfortable outside air temperatures. The vaulted ceiling was made possible by not having an attic over most of the house. Hence, a mere 5 cm of wooden boards and asphalt shingles was all that stood between us and the summer sunshine. The wall of single-pane glass allowed the sunlight to pass nearly undiminished into the main living area.

My first impulse was to do what any data center manager would do— throw more fans at the problem. In time, I located three advanced whole house fan units and installed them. All were mounted near the roofline to exhaust the hottest air in the house.

The level of success that I had was comparable to that of our imaginary data center manager— it cooled the house down, but at a cost of a 2x increase in our electrical bill and near deafening noise from the most powerful fan when it was running at high speed.

At this point, my inner cryogenic physicist entered the conversation and suggested that the source of my problem was thermal radiation that was heating our living space. If I dealt with that well enough, then the fans would not have to work as hard.

Since then, we have installed a new roof over our old one with a thick layer of rigid foam insulation between them and retractable sun screens on all the windows. Our house is now comfortable without air conditioning, except on the very hottest days. The fans have been demoted to a supporting (and quieter) role.

The end result is satisfying both personally and professionally. We’ve achieved an acceptable level of comfort in a manner that is economical and environmentally friendly. I even hear that data center managers are beginning to think in those terms as well.

 

Following up on Jim Wilson’s editorial in the last issue. I’d like to acknowledge all of Bob Simon’s contributions to this publication. It was a particular pleasure for me to collaborate with him on the Calculation Corner column. I’m happy to welcome Bob’s successor, Madhu Iyengar, who has published his first Calculation Corner in this issue.

 

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