Expansion noise - capillary tube into evaporator

[desA]

Thats the point about a cat tube in a heat pump - it is not a fixed pressure drop - quite the opposite.

When the water is 10C there will be a lot of SC available and so even if the pressure is less the flow through the cap tube will increase over the value assumed if it was just related to Dx and Sx. As the temperature of the water rises the SC is less but the pressure is higher so the flow is roughly the same and when its hot then lets assume we get to no SC and much higher pressure which gives a similar flow. So in this arrangement a cap might be good in a heat pump.

Excellent points.

Take the point about ambient rangeing from -10 to 45C would cause problems in the evap area but are these temps really common?

Seasonal variation - yes - daily variation - unlikely, except in a desert. Add into the mix the RH%...