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Could any one advise how temperature and humidity is controlled in an operating room with 100% fresh air?A chilled water AHU is being used.
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Preheat coil - freeze protection
Chilled water cooling coil - cool air to 54F
Reheat coil - for humidity control
Chilled water cooling coil - cool air to 49F
Fan - motor heat
Final Filters - hepa type
Doctors want it cold in the room so be ready to drive the temperature down. You may need glycol in the chilled water system to get 40F water temperature. the alternate is to have a DX coil to drive the temp. down.
Chilled water cooling coil - cool air to 54F
Reheat coil - for humidity control
Chilled water cooling coil - cool air to 49F
Fan - motor heat
Final Filters - hepa type
Doctors want it cold in the room so be ready to drive the temperature down. You may need glycol in the chilled water system to get 40F water temperature. the alternate is to have a DX coil to drive the temp. down.
This is a common configuration and is an energy hog. The chilled water wrings out the air by using a lower discharge temp setpoint. On hot, humid days, the 100% outside air unit can be set to discharge at a real low temp (say 50°F, as long as it's sufficiently designed) - means the exiting air dewpoint can't be any higher than 50°F, which reduces high humidity in the OR. Air is then re-heated as needed by the space, either at the terminal box in the duct work or at the central unit, after the chilled water coil before entering the space to control temperature so as not to freeze people. In the winter when it's dry, a humidifier either in the duct work or in the central unit should maintain space humidity. Hope that helps. -Chas
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- #4
it is better to use run-round coil around
the main cooling coil, this is two coils,
one in front and one behind the main coil.
water is pumped around the coils transferring
heat from the front of the coil to the rear
thus reheating the air for "free". also
it is possible to reclaim some coolth or
heat from the exhaust again using cooling
coil, to transfer wasted energy.
the final touch up is from heating coil
which can be hot water etc.
the preheat coil is necessary in winter,
depending on design temperature.
there is no need for glycol, a properly
sized coil can take fresh air at wetbulb
of 82degF down to dewpoint of 50degF with
chilled water at 44degF.
rgds
leelock
I use a two stages of cooling for control.
The first coil will be at least 6-8 rows. It will do the bulk of the work. In the summer the control valve is running wide open. The second coil is for fine tune the leaving air temperature.
Also when a coil starts to leak you have a back-up that can handel most of the load.
Electric heat is my prefered option. Typically hospitals have a boiler, steam and hot water storage so i use what is available.
Wrap around coils do work and i have specified them on other jobs with lots of outside air.
The first coil will be at least 6-8 rows. It will do the bulk of the work. In the summer the control valve is running wide open. The second coil is for fine tune the leaving air temperature.
Also when a coil starts to leak you have a back-up that can handel most of the load.
Electric heat is my prefered option. Typically hospitals have a boiler, steam and hot water storage so i use what is available.
Wrap around coils do work and i have specified them on other jobs with lots of outside air.
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