Effect of evaporator numbers on water production of a free convection air-water harvester

Abstract

An experimental study was performed to determine the effect of the number of evaporators on the water production and coefficient of performance of an air-water harvester. Water was obtained on the evaporator walls in free convection and condensation heat transfer modes. The evaporator dimension was 480 mm × 285 mm × 6.25 mm, and it was made of copper pipes. The evaporators were installed in a parallel arrangement in an open box (top and bottom open) with a size of 500 mm × 500 mm × 500 mm. The refrigerant R134a was used as the working fluid. The experiments were performed at a low pressure of 40 psi and a high pressure of 180 psi. In the outside evaporator walls, air flowed naturally and part of the water vapour in the air condensed. Three evaporator variations were tested: Case A (one evaporator), Case B (two evaporators), and Case C (three evaporators). Each evaporator contained 25 copper pipes and the length of each pipe was 285 mm. The maximum water production and the evaporator efficiency attained were 0.51 L a day and 13 % respectively. The COP of the machine was ranging from 5.2 to 13.3. Increasing the evaporator number elevated the water production.