Refrigerator efficiency

daudaudaudau

Hi.

I need to write up an expression for the efficiency of a refrigerator(coefficient of performance). The general formula is

K=|QC|/|W| = |QC|/(|QH|-|QC|)

But how do I write up expressions for QH and QC? So far I have this

QH=m*Lv (Lv: heat of vaporization)
QC=p*m*Lv

where 0<p<1 because not all of the coolant vaporizes inside the refrigerator. But I don't like this expression, because it don't know p.

So my question is: Can anyone help me with an expression for the coefficient of performance, preferably in terms of the refrigerator temperatures and some coolant constant?

Here is the PV-diagram im using: http://www.phy.ntnu.edu.tw/~chiact/i...s/img00469.gif