Characterization of liquid behavior in distributor of falling-film evaporator

Abstract

Recently, the development of environmentally friendly refrigerants has emerged as a major issue in industry. Owing to the high cost of developing new refrigerants, falling-film evaporators are attracting increasing interest, given their reduced refrigerant usage compared with flooded evaporators. In falling–film evaporators, the distributor at the top of the evaporator uniformly delivers refrigerant through multiple holes over heat transfer tubes. We focus on the liquid (refrigerant) behavior in the distributor of a falling-film evaporator. To understand the underlying mechanism, we perform experiments on single hole as well as multiple holes in the distributor. For both cases, we have derived theories that predict the refrigerant height in the distributor, according to the flow rate. They show good agreement with the experimental measurements. By changing the hole diameter, number of holes, and flow rate, we quantitatively characterize parametric dependencies that determine the liquid behavior. In addition, we unveil a negative effect of the supply stream from the upper distributor that locally mitigates the outflow rate from the distributor.