I purchased an evaporator holding the following specifications: Cooling Capacity = 2 kW Size = 66 X 53 X 43 What I need to know is how to choose a compressor just to gain this full cooling capacity?
When designing a refrigeration system, the first thing you need to know is the temperature you wish to heat/cool something to and the temperature of the source/sink you are pumping to or from.
You can use the Carnot Equation to solve for your theoretical best efficiency.
Once you know that, you deturmine what capacity you need. Like 2kW for example if I know I need to cool a 2kW laser, or 100W if I know I need to cool a 100W processor. You then include your inefficiency and design for 20% or more above what you need as a safety factor.
From that point, you can go on to sizing your compressor, working fluid, operating pressure, condenser, evaporator, air flow rates, etc. Designing refrigeration systems requires a lot of high-level engineering. I recommend investigating your original objective, researching refrigeration systems, and posting back here with a new question if you need help at that point.