# Average Rate of Heat Gain in Fridge

1. ### Jacob87411

171
Just curious if anyone knows an approximate for the average rate of heat gain for a common fridge? Im going to do an experiment to calculate the average rate of heat gain in my fridge and want to know if my numbers in the ballpark

2. ### Artman

An average household fairly efficient refrigerator will use about 50 kWh per month.

According to this cost guide:

Energy Cost Guide

That will maybe give you a starting point.

3. ### tward

1
Did you ever find out? I'm trying to find out. Of course, the answer depends on the refrigerator (set point) temperature and the ambient temperature. Still, there should be a rule of thumb that requires only a) the temperature difference between the refrigerator and exterior and b) the refrigerator surface area.

4. ### Mech_Engineer

2,299
All you need is the average power consumption of the refrigerator, the temperature of the refrigeration compartment, and ambient temp. If you approximate the refrigerator as a Carnot Vapor Refigeration Cycle, you can calculate the coefficient of performance using just the temps:

$$\beta_{max}=\frac{T_{c}}{T_{h}-T_{c}}$$

and using the coefficient of performance and the power input (with an efficiency for the the compressor, maybe 80%), the heat gain is calculated as:

$$\dot{Q}_{in}=\beta_{max}*\frac{\dot{W}_{c}}{\eta}$$

So for a refrigerator holding at 35 degrees fahrenheit (275 K) and ambient of 75 degrees fahrenheit (297 K), with an average power consumption of 70 watts (50kWh per month), and assuming the power consumption is mainly from the compressor, the average heat gain would be about 1000 watts if I did the calcs right...

Last edited: Apr 26, 2011