[labnetwork] Thermal load in cleanrooms ISO 5/6

[Paul, Jack]

Hello Loïk,
I am an architect with HDR Architecture, Inc. and engineering and architectural firm who design cleanrooms.  We have a few comments on your notes below:

-        As you have already done, start with your equipment list.  It is safe to assume that all power consumed by equipment is converted to heat (very little "mechanical" energy).  However, your 75% simultaneity factor is probably high.  We tend to see it much closer to 25% (we usually call this "diversity") which assumes that at any point in a working day, about 25% of the equipment is actually running.

-        If you have data from manufacturers for how much heat is dissipated to cooling water, then you can subtract that heat load from your total equipment load.

-        We would normally account for the load for lighting.  If you do not have data on the lighting fixtures, it is safe to assume about 10 watts per m2.  This load would not have any diversity.

-        We would also account for the heat load for the fan filter units.  It can be significant.  The fan-filter unit manufacturer should be able to provide data, but if not you can use as a placeholder roughly 50% of the power consumed by the unit, and again this load would not have any diversity applied to it.

-        Each person is a relatively small load (100 - 125 watts/person)

·        The sum of these items is a good estimate for your cooling load in the cleanroom.


-        A central cooling water loop is generally most energy efficient.  A series of separate smaller chillers consume power and reject the heat into the cleanroom airstream where it then must be removed by the ACS.  Water is a better thermal energy conductor than air.

o   A recirculating loop with a heat exchanger and pumps, dedicated to the equipment will typically provide the best performance.

o   The primary side of the heat exchanger can be chilled water from your ACS or a central plant (whatever you have available in your new cleanroom facility)

o   The secondary side would feed the loop and be routed through the cleanroom to individual tools.  It can be a closed loop so you have complete control of the quality of the water.

Hope this helps.  Let us know if you have additional questions.
Regards,
Jack Paul

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Loïk GENCE
Sent: Monday, March 16, 2015 7:36 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Thermal load in cleanrooms ISO 5/6

Hi Everyone,

I am working on the design of a small cleanroom facility (70m2) ISO 5/6. Right now, I am dealing with the problem of thermal load,
Which is crucial here in Rio, where the average outside temperature is of 30 deg C with a relative humidity of  75-80 %.

I would like to have your help and/or comments on several points:

Most of the manufacturers do not provide a value for the thermal load (why?). Assuming 2 or max 3 people working simultaneously in the cleanrooms, and usual cleanroom value: 22 deg C - 55% humidity. The main issue is: how can I estimate the cooling power required for the Air Conditioning System (ACS)?

I have the list of equipments we'll have and the corresponding electrical power. I assumed the heat generated by 2 users and added the total electrical power dissipated as heat inside of the cleanroom, using a simultaneity factor of 0.75 (all equipments won't be turned on at the same time) and neglected the heat produced by the filter fan and lightning.

        - Is it reasonable for dimensioning the ACS cooling power ?

Also most of the equipments have a cooling water circuit. But the cooling power needed is well described in the installation manual provided with the equipments.

        - Should I subtract from the ACS cooling power value,  the cooling power from the chillers?

        - Do you think a central and unique chiller (placed outside of the building) is preferred to several smaller chillers placed closer to the equipment?


I thank you very much for your kind help or comments.


regards,

Loïk.



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