Numerical Simulation And Analysis Of Heat And Mass Transfer In An Indirect Evaporative Cooler

Nowadays, the problems of energy and environment are becoming very seriously. It is very important to make an effort to limit energy consumption and to use non-polluting refrigeration technologies in the field of air-conditioning. Evaporative cooling technologies make use of cooling by water evaporation in unsaturated moist air. This method has attracted a lot of attention. Indirect evaporative cooler is a special type of evaporative cooling equipments used in air-conditioning. Since the heat and mass transfer occur simultaneously in an indirect evaporative cooler, the mechanisms of heat and mass transfer processes are more complex compared with that in a sensible heat exchanger. In this paper, these were analyzed and studied from the point of view of Computational Fluid Dynamics (CFD).In the first, the state of the applications and technologies of evaporative cooling was analyzed comprehensively. The structure of indirect evaporative cooler and the heat transfer characteristic were also analyzed. The mathematical models with laminar and turbulent flow conditions were developed for the fluid flow and the heat and mass transfer processes with simplifying assumptions. The numerical method was discussed briefly. The problems of coupled heat and mass transfer processes are solved numerically.A comparative study was presented of the results from laminar and turbulent models, and some available experimental data. Results indicate that laminar model is appropriate for Re number less than 2000, while the RNG k-e model is appropriate for higher Re numbers. The characteristics of velocity, temperature and concentration distributions were discussed based on results of numerical simulation. Nusselt and Sherwood numbers were calculated using temperature and concentration profiles. The effects of variable parameters on average Nusselt and Sherwood numbers were investigated. Correlations for average Nusselt and Sherwood numbers were developed in terms of Re numbers and a new dimensionless parameter 9, which takes into account the effects of the inlet dry-bulb and wet-bulb temperatures of the secondary air stream and the inlet dry-bulb temperature of the primary stream. The variation of exergy of moist air was analyzed, and the conversion of energy and irreversible exergy destructions were also discussed. Lastly, the effects of a wide variety of parameters such as the velocity, the temperature, the relative humidity and the channel width on...