100% Outside Air

[ChipFuller]

I'm designing an air conditioning system for 100% outside air. The area is a small lab room approximately 950 ft3. My heating loads are 6600 Btuh sensible and 1500 Btuh latent. I trying to design the cfm required. I'm working in a dry climate so I've neglected the latent. Some people suggest that I should:

6600/(1.08*(97-55)) where 97 is the outside air requirements and 55 is the leaving temperature off the coil. This delivers about 152 cfm. The reason I've been given is because that temperature of the air I want to deliver and am making up for the 6600 heat gain. This gives me about 10 Air Changes/Hour

Other people suggest that I should use:

6600/(1.08*(75-55)) where 75 is the temperature inside the room. This delivers about 305 cfm. I will size the coil from this formula: 1.08*(97-55)*305. I have also been told if I use this method that I will freeze up the coil because the air flow is too great.

Which method is right? Can I buy this system as a packaged unit? Also where can I find a psychometric chart for 4500 feet elevation?

Thanks

 

[VSSriram]

This seems to be an interesting heat load which I used to do manually at the start of my career. 100% outside air application cooling load calculations are normally done by iteration.

First assume a particular outside air quantity and do the load calculations, find out what the dehumidifed air quantity is. If it matches the assumed outside air quantity, then the initial assumption is right. Otherwise, do another load calculation absed on the dehumidified air quantity obtained and keep doing this (iteration !!!) till you get the same figure.

Alternatively, if you have a software like E20-II of Carrier, you can just input all the relevant data and put 100% outside air and the program gives an output which will be 100% outside air.

 

[greenaire]

Hi

Here is web address for mentioned article and complete article name. If you still can not get it, give my your email address. Then send it to u by email. My email: naymo@greenaire.com.sg

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Design tips for effective, efficient dedicated ventilation systems by Dennis Stanke, 2001, volume 30-3. PDF or HTML