Numerical investigation on two-phase fluid flow characteristics of evaporator distributor with R404A and R744 refrigerants.

Evaporators play a key role in refrigeration units and they are typically determined in accordance with the size of cooling systems. While evaporators can have multiple circuits for refrigerant to flow through, each circuit is designed to have equal amount of liquid refrigerant so that desired heat can be absorbed from the surrounding efficiently and ensuring that all the refrigerant is completely evaporated into gaseous phase. However, when evaporator's circuits receive non-uniform refrigerant from a distributor placed between the expansion valve and the evaporator, this non-uniform flow can yield reduction in capacity and COP of refrigeration system. In the present study, an evaporator distributor will be numerically studied by using two different refrigerants, R744 and R404A, for the purpose of identifying the difference in behavior of these refrigerants. The quality of mixture for refrigerants will be varied by taking corresponding qualities for evaporation temperatures -8°C, -18°C and -25°C to identify the relation between refrigerant's quality and mass distribution of refrigerant in each tube of the distributor. In addition to use of two different refrigerants, nozzle position of the distributor was changed from 0.01 mm to 2.01 mm and 4.01 mm to evaluate the effect of nozzle placement on mass flow rate uniformity at the distributor exits for an evaporation of -8°C.It was realized that the effect of evaporation temperature was only significant for R404A study since -8°C evaporation temperature provided most uniform mass uniformity at the distributor exit. It was also noticed that nozzle positions of 0.01, 2.01 and 4.01 mm were only significant for R404A fluid flow simulations since both 2.01 and 4.01 mm nozzle locations resulted in nearly 40% deviation in mass flow rate at distributor exits.