Thermodynamics fridge problem

[NaOH]

This is my prompt:

"Using a timer (or watch) and a thermometer, conduct the following experiment to determine the rate of heat gain of your refrigerator. First make sure that the door of the refrigerator is not opened for at least a few hours so that steady operating conditions are established. Start the timer when the refrigerator stops running and measure the time Dt1 it stays off before it kicks in. Then measure the time Dt2 it stays on. Noting that the heat removed during Dt2 is equal to the heat gain of the refrigerator during Dt1 + Dt2 and using the power consumed by the refrigerator when it is running, determine the average rate of heat gain for your refrigerator, in W. Take the COP (coefficient of performance) of your refrigerator to be 1.3 if it is not available."


I know that i will need the wattage of the refrigerator (work in, in order to remove heat). Also, I get that I need to measure the time that the motor is on and the time that it isn't. I'm just kind of stuck on what to do after that. I figured, I would multiply the wattage by COP in order to determine the rate of heat power rejected. Not sure what to do after that......Can someone help me!?

 

[silverpig]

You then take that rate of heat power thrown out and multiply it by Dt2 to get the amount of heat removed. Heat out = heat in, so divide that number by dt1 to get a rate of heat in.

 

[dighn]

well COP*workDone would be the amount of heat pumped out by the refrigerator which by the assumption stated in the question would be equal to the amount of heat gained through the off cycle, divide that by Dt1 and you have the rate of heat gain

 

[NaOH]

So I have COP*Wattage = Q (heat rejected, kW or kJ/s) I multiply that by Dt2 (time on) to get the amount of heat rejected (so it becomes kJ), then divide that by Dt1 (time off) to determine how long it took to gain that amount of heat. Making it kJ/s or Watts again? Units end up correct. Trying to see if I get the logic.



edit: wouldn't I have to divide by Dt1+Dt2? It states that the heat rejected during Dt2 is the equal to the amount of heat gained during Dt1 + Dt2.

 

[NaOH]

??

 

[dighn]

I think you are right. oops

 

[unsped]

is the fridge on a conveyer belt?

 

[NaOH]

Originally posted by: unsped
is the fridge on a conveyer belt?

 

[NaOH]

So does my answer seem cool?