# Design experiment to test air conditioner performance at different ambient temps

1. Jan 10, 2013

### chelcers

1. The problem statement, all variables and given/known data
I have access to a test facility for window type air conditioners that has a small room that is used to simulate the outdoors. I need to use the facility to test the effect of temperature on the performance of one of our window type AC units. The performance must e done as a function of temperature at the different air conditioner settings.

2. Relevant equations
COP = Q/W = 1/ (T_outside/T_inside - 1)

3. The attempt at a solution

I think finding the COP at different temps would give a good representation of the AC performance but I'm not sure how to experimentally determine this. Any help would be greatly appreciated.

2. Jan 11, 2013

### rude man

Your formula is for a reversible process and so is all but useless for what you're trying to do, except to see how much lower your COP is compared to that of a reversible (e.g. Carnot) process.

You say you have a room set aside to simulate the outdoors. I hope you also have a room set aside for the indoors. The "outdoors" room should be temperature-controlled, call it To. The "indoor" room should be thermally insulated and its dimensions known, so you can determine the heat capacity of the air C. Record the "indoor" temperature = Ti. You then run the a/c until Ti has decreased by ΔTi deg C. Meanwhile you have a wattmeter or power meter hooked up so you know the energy E used to raise Ti by ΔTi deg.

The performance (efficiency) of the unit at each set temperature To is then COP = CΔTi/E. I would use ΔTi = 2 or 3 deg C.

You can get handy plug-in power meters from companies like Belkin.