Numerical Study Of The Thermal Performances Of A Counter Flow Dew-point Indirect Evaporative Air Cooler

The research and applications of evaporative cooling air-conditioning technology have achieved great development in recent years in China. A number of successful cases of air-conditioning engineering based on evaporative cooling technology(ECT)have been achieved, especially in dry Midwestern regions in China. However, the driving force for the traditional ECT is the difference between dry and wet bulb temperature. Its disadvantage is that the temperature drop of supply air is severely limited,leading to the large-sized ducts of the supply air and the limitation of its widespread use. Although the supply air temperature is lower than the wet bulb temperature by means of the methods of multistage direct or indirect evaporative cooling, the cooling efficiency is not high enough and the corresponding structure is complex.Aiming at the above problems, this paper presents a counter flow indirect evaporative air-conditioning pattern(CFDIEACP), and its driving force is the difference between dry bulb and dew-point temperature. The air-conditioning systems using CFDIEACP can obviously depress the temperature of supply air and reduce the size of supply air ducts. Moreover, this air-conditioning process can be easily realized and applied to the air conditioning condition in summer in the middle and eastern and regions with high humidity and dry Midwestern regions in China. The main research results in this paper are as follows.1. Based on ECT and CFDIEACP, the corresponding heat and moisture transfer model of counter flow dew-point indirect evaporative air cooler(CFDIEAC) is set up.According to i-d chart, its working mechanism is studied and analyzed in detail.2. Each component of a CFDIEAC is mechanically analyzed on the basis of the heat and moisture transfer model of CFDIEAC. In addition, a comparison of this CFDIEAC with the single-stage and multistage direct or indirect evaporative air cooler using the traditional ECT is carried out.3. By CFD software, a thermodynamic simulation for the heat and moisture transfer model of CFDIEAC is executed and the proposed CFDIEAC is feasible in theory in terms of the simulation results. Moreover, another simulation of the influence of the structure and operation parameters of this CFDIEAC on its thermal performances including supply air temperature, wet bulb and dew-point efficiency is carried out as well.4. As for the air-conditioning requirement in summer in a building, the proposed CFDIEAC is adopted as the cold source for an air-conditioning system with the complete fresh air. Based on the annual cost method, a comparison of economy andenergy conservation of this air-conditioning using CFDIEAC with the traditional air-conditioning with return air is executed. The results indicate that the former is superior to the latter, and the effects of energy conservation and consumption reducing are remarkable.