Steady-State Analysis of Dew Point Evaporative Cooling System

Abstract

This study focuses on learning the principle of dew point evaporative cooling system. A single-stage dew-point evaporative cooling system with counter-flow configuration was developed in this study by building numerical simulation model and experimental setup. The evaporative cooling system was firstly designed by numerical simulation in terms of geometrical sizes and operating condition. The finite method was applied to make a solver in order to calculate the system equations, which can solve not only ordinary differential equations, but also partial differential equations. Python was the selected computer langrage to finish the whole calculation.A small-scale dew point evaporative cooling system prototype was made in the laboratory which includes four main components: main m-cycle unit, water supply system, air supply system and measurement devices. The first purpose of building the experimental bench is to understand and learn the actual operation of the dew point evaporative cooler, and the second is to test the accuracy of the simulation model through actual experimental data. The results show that the error between the experimental data and the simulation results is about 15%. Which indicated that the current model was able to simulate the heat and mass transfer process in m-cycle cooling system.Several operation conditions were carried with this validated numerical model and the system performance was manifested by wet-bulb and dew-point effectiveness. The numerical results indicate that the inlet condition (inlet air velocity and working ratio) and geometrical size (channel length and height) can have a significant effect on system performance. By changing the velocity from 1 m/s to 3 m/s, the wet bulb effectiveness can be changed from 1.38 to 0.96, while dew point effectiveness is from 0.88 to 0.62. Similarly, in the working ratio case, the wet bulb effectiveness is from 1.03 to 1.42, while dew point is from 0.66 to 0.91. For the geometrical case, increasing channel length brings the increasing of wet-bulb and dew-point effectiveness, when the channel length varies from 0.2 to 1.5m, the wet-bule effectiveness and dew-point effectiveness varies from 0.59 to 1.39 and 0.38 to 0.90.