Parametric Study and Computational Two-Phase Flow Simulation of the Refrigerant Distributor in a Spray Type Evaporator

This manuscript presents a simplified model for the simulation of liquid-vapor flow in a spray type evaporator of a chiller unit. In the present study, the liquid and vapor phases are considered as two separate fluids and simulated by the commercial code, FLUENT. Two types of distributors were investigated: (1) a miniature tubular distributor, and (2) a full scale distributor. The tubular distributors consists of two tubes, the pore size (1.0 mm or 1.5 mm) of the inner tube and the gap size (1.0, 2.0 or 3.0 mm) of the outer tube were varied for comparisons of the velocity and pressure distributions. Three different flow rates: 1.6, 3.2 and 6.4 g/s, were set in the simulations of miniature distributor. The full scale distributor consists of a 30 mm diameter tube having 4.0 mm pores in 18 mm pitch, and a 2400 mm × 226 mm perforated plate having 3.0 mm pores. The Volume of Fluid model and the Continuum Surface Force model were used in the two-phase simulation of the full scale distributor. From the present study, we found that the 3.0 mm gap width yields the most uniform flow distribution for 1.6 ∼ 6.4 kg/s for the miniature distributor. Based on the simulation of the miniature distributor, a falling film evaporation test apparatus is designed, and uniform fluid distribution in the evaporator is found. The fluid distribution observed in the test of an 80 ton chiller is more uniform than that shown in the preliminary result of the full scale simulation.