# Thread: air traveling from different spaces

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## air traveling from different spaces

Here is my problem

I have a supermarket connected to a mall (common area) entrance 16'x8'.

Temp in the mall 72°F
Temp in my supermarket: 65°F

I'm eitheir loosing cool air or gaining warm air. How would I go about approximating surch a value??

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Here is my dumb question(s):
Is the Mall supposed to be at 72* ?

Is the Market supposed to be at 65* ?

I will be glad to try to help but I am afraid I don't completely understand the question ! A little more info please.

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The mall is at 72°F and 50% HR

The supermarket needs to be at 65°F and 50% HR

The customer wants it like that.

I have to calculate the gain or loss on the supermarket side due to the air exchange

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Since the laws of thermodynamics (can't remember which one, think it's the 2nd) state that heat transfer is always from warmer to cooler then I would say you are getting a 5* "Gain" from the Mall side to the market side. What you need to do is measure the volume of air (cfm) that is passing from the mall to the market. That assumes that there is a pressure difference between the 2 spaces. If there is no pressure difference ( I would expect the market to be lower than the Mall) then you are simply dealing with natural convection, I would guess. That is hard to quantify with out lots of test equipment.

You have your work cut out for you. Hopefully smarter people than I will contribute
Last edited by Cagey57; 09-04-2009 at 06:50 PM.

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That's a big size opening... this approximation needs to be as accurate as possible.
Should the market be in positive pressure? Wouldn't it be better to avoid hot air coming in?

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It would be easier to Cool, Dehumidify, and Filter the mall air, verses outside air. But; you need to have the supermarket legal department look at their lease contract, it's probably written in the contract, that they must be positive to the mall side.

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Originally Posted by guitarboyled
The mall is at 72°F and 50% HR

The supermarket needs to be at 65°F and 50% HR

The customer wants it like that.

I have to calculate the gain or loss on the supermarket side due to the air exchange
WOW!

We had a customer try that 65 degree store thing for a while. Then they started getting the bills. Funny how that changes their minds.

There is absolutely no need for a market to run at 65 degrees. I keep mine between 71 and 74 with a 48-55 degree DP (we don't often control on RH)

I would seriously talk to the customer about the un-needed energy usage to over cool the space and how much they could save on utilities by raising the temp 5-7 degrees.

If they insist, try selling them an air curtain type unit or two to to keep the air out. They annoy customers, but they do work.

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It's the customers demands... They understand the cost. Have to go with it

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