From my research: Propane (R290) performs best with very high Superheat (33-35*C) at the compressor input.
Attaining this much Superheat without a (SLHX, IHX, LSHX) many names, would require that the TXV throttle down the refrigerant flow so that the last section of the Evaporator would not be evaporating any more refrigerant, but just be adding sensible heat.
This throttling down of refrigerant reduces Mass-flow in system, thus capicity drops.
It seems that attaining this much superheat at the compressor input should be accomplished with a SLHX.
Another great benifit in performance, is increasing Sub-cooling at the TXV, so bubbles are elemonated.
Finding SLHX optimum size testing has been difficult, I have seen examples from 1/3 as big as the condenser on down. ?
http://inpressco.com/wp-content/uplo...r48226-229.pdf
" Use of liquid-suction heat exchanger in the VCRS reduces the possibility of liquid
carry-over from the evaporator which could harm the
compressor, by superheating the refrigerant vapours after
evaporator, by the heat of hot liquid refrigerant available
after condensation. The refrigeration capacity of the
system is increased by 9% to 32% for different flow rates
of the refrigerant in the range of 12 to 16 LPH, which is
obtained due to the sub cooling of the liquid refrigerant in
the LSHX, leading to the efficient throttling. For lower
flow rates of the refrigerant the effectiveness of the LSHX
is maximum as compared to higher flow rates, because the
time available to exchange heat is more in case of the low
flow rate. The optimum effectiveness (0.65) is obtained at
40 °C of initial water temperature. Use of LSHX in the
vapour compression refrigeration system, increases the
COP of the refrigeration unit for different initial
temperatures of water by 10 % to 40 % . The compressor
work gets reduced by 3% to 11%, by using the liquid
suction heat exchanger in the vapour compression
refrigeration system that means less power consumption
by the refrigeration unit has been observed. The LSHX
sub-cools the liquid refrigerant before passing to the
expansion valve which leads to the rise in evaporator
capacity which is much more than the heat rejected in sub-cooling.
Thus the LSHX is found to be a device which is
useful for avoiding flashing of refrigerant in expansion
device that raises the amount of liquid refrigerant in
evaporator. Ultimately, it increases the refrigeration effect
and COP of the system (10 % to 40 %). The optimum
effect of the LSHX is seen at different flow rates of the
refrigerant for lower initial temperature of water (30 to 35
°C)."