Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
(OP)
I work at an airport with a large chilled water system, 2.2 million gallons of chilled water storage, 5 chillers @1150 tons, and a design water temperature rise of 18 F (starting with 42 F water). We've learned some valuable things about achieving a high water temperature rise. I'm interested in knowing if anyone else has ideas that they would like to share on this.





RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
These coils are basically similar to coils for more conventional air handling equipment. To achieve the higher temperature rise, the aluminum fins are spaced tighter (say 12 or more fins per inch), and there are a greater number of rows (say at least six) of copper tubes that carry the aluminum fins. The only tricky part about this is that the high water temperature rise means more heat per gallon, and lower GPM. This means that the water velocity in the tube gets lower. When we first got into this, there was concern about laminar flow and poor heat transfer. For the 18 F temperature rise in this system, we haven't seen this as a problem.
Thanks for your interest.
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
I am a student in mechanical engineering and I am looking into starting my own business when I get out of school. Most of my classes were thermodynamics and fluid mechanics classes. I did a lot of cycle analysis with numerical simulations. If you have any advice for me I would greatly appreciate it.
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
I have seen problems with loss of dehumidification control on large chiller systems when the chilled water temperature is reset up only a couple of degrees.
I also am wondering how much supply temperature loss there is. I assume there is a lot of distribution pipe, and 42 degrees at the ahu coil might require 40 degrees at the chiller?
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
It's hard to offer career advice. People have different constraints with family, children, etc. Many engineers today have higher degrees, and it seems to me that the people who have higher degrees have a better chance of doing real engineering work as opposed to project management or similar. I recently obtained my professional engineering license, and I think that this also opens the door to better work. But you have to weigh all things against your family constraints, etc.
One area that I'm interested in that may have some future is magnetic refrigeration. Do you know anything about it? Some people say that someday it may replace vapor compression refrigeration widely. But not all of these things actually work out.
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
The first step in achieving high water temperature rise in a chilled water system is selecting cooling coils that will give a high water temperature rise.
Back to dehumidification, our facility is not the one with the highest water temperature rise that dehumidifies acceptably well. Dallas Fort Worth airport is reported to have a chilled water system with a water temperature rise well above 20 F. However, their climate may be drier, and dehumidification may not be as much of an issue.
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
I've been collecting technical articles on this subject for several years. If you'd like me to send them to you, please advise.
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
My experience has been that it's not particularly difficult to design a chilled water system that achieves good water temperature rise if you follow some basic principles. But to get the piping built without mistakes and to get the controls doing what they should do is more difficult. My main interest was in practical aspects of getting a system working and keeping it working. But I'd be happy to share what I've picked up r.e. design.
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise
I would like to have a simple digram of the system if possible.
I also appriciate to get more inforamtion, may be web sites, on the thermal storage system (TES)
address
Projacs
P.O box 93401 Riyadh 11673
Riyadh, Ra
Saudi Arabia
Regards
Jasem
RE: Chilled Water Systems for Building HVAC - Achieving High Temp. Rise