You have a single pipe - let's say 1/2" - and you use this as an evaporator, submerged in water.
Tc = 40°C, Te= 0°C, let's say R134a
At the inlet a TEV, inlet SC liquid with 3K, outlet SH of 5K.
Second situation: SC of 20K.
I'm a little bit confused: in the 1st situation, we will have refrigerant with a lower quality than the situation with 20K. If we have 20K SC, and we used the outlet conditions to calculate the needed diameter of this coil (1/2"), will we then not have very high liquid speeds in the first parts of the tube, provoking a large DP in the first meters of the coil?