Hello all, I have an idea for a winter holiday project and I'd welcome any comments or criticisms. I am an engineer but not familiar with heat pump systems, other than the basic principles.

What I'd like to do:
Couple a salvaged car air-conditioner system to a small air-cooled diesel stationary engine that I already have.
The cooling air (and possibly exhaust) from the engine is ducted through the heat exchanger (the alloy radiator from the car), hopefully eliminating the problems of icing and poor COP during cold weather.
The condenser would be replaced with a simple tube-in-tube heat exchanger to transfer heat to a domestic hot water system.

Questions: Will this work at all, or have I made a fundamental mistake? Is there any hope of the performance being reasonable?

What (UK) car has a system that would lend itself well to this application? What about recharging it?

Thanks!