[labnetwork] Thermal load in cleanrooms ISO 5/6

[Michael Khbeis]

Loik 

I think that having the electrical load converted to heat load and having the diversity factor is sufficient. You can subtract the heat load dissipated through chilled water but that is presumably also being fed by your primary chiller. I would err on the side of being conservative since cleanrooms always end up being packed to a maximum density of equipment and people during their lifespans - give yourself a 20% margin at the least. I also would not discount the impact of the filter fan unit heat dissipation.  Since you are recycling most of the air several times the joule heating from the FFUs will cause a noticeable temperature rise. Given the class of your Cleanroom the FFU density will not be as high but I would add them into the load calc. 

Finally, regarding central chiller vs multiple point of use units - much easier to keep spare parts on hand and do PMs on a central chiller unit as these are usually handled by the building facilities folks. In my opinion, multiple point of use chillers are a maintenance nightmare and you often end up buying something quickly to replace or augment a failing unit. It is nearly impossible to keep multiple point of use units running consistently if you don't have dedicated maintenance staff. The exception to this is if your tools all required different or special temperatures and you end up needing multiple water-to-water heat exchangers then point of use chillers may make sense. 

Best,

Dr. Michael Khbeis
Washington Nanofab Facility
University of Washington
Fluke Hall, Box 352143
(O) 206.543.5101
(C) 443.254.5192
khbeis at uw.edu

> On Mar 16, 2015, at 7:36 AM, Loïk GENCE <Loik.gence at cetuc.puc-rio.br> wrote:
> 
> 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.
>   
> -- 
> __________________________________________
> Dr. Loïk Gence      
> 
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> 
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