Heatpump from number of old refrigerators?

[Zwerius]

I was thinking about building a heatpump consisting of a number of old refrigerators. So actually a number of small heatpumps in parallel. By switching on a larger number by colder weather, you have a kind of modulating system.
If the outside temperature rises again, more compressors can be switched off.
Of course the order in which compressors start, must be random, so that they wear out evenly.
Advantage: Old refrigerators can mostly be had for free...
However I have no idea of the COP when using an old refrigerator as heatpump.
The idea was, to exchange the evaporators for copper pipe coils. Getting the heat from ground water (to be pumped from a well).
Anyone who used refrigerators as heatpumps?
And any idea about the COP's that can be achieved. Probably not so good because there's no control valve, but only the fixed restriction (capilarry pipe)?