The entransy analysis in the wet channel of dew point evaporative cooler

Abstract

A method to calculate entransy change (ΔE) and thermal resistance (R) was proposed firstly in this paper. The experimental results showed that in the wet channel the R was decreased and the total heat exchange capacity (Qt) was increased gradually along the air flow at the condition of Turpan and Shanghai, but showed a different trend in Lanzhou. Meanwhile, in the dry channel the cooling capacity (Q) and temperature drop (ΔT) were decreased along the air flow in all three regions. As inlet temperature increased, the R was decreased and Qt was increased in wet channel, thus the Q and the cooling rate in dry channel were increased. With inlet humidity ratio and air velocity decreased in dry channel, the R in wet channel was increased firstly and then decreased. The lowest inlet humidity ratio was, the smallest R in wet channel was, the highest Q and temperature drop rate in dry channel were. At the velocity 1.8 m/s, the R dropped to the lowest point, after that, Q was increased slowly and the temperature drop rate was reduced in the dry channel, therefore, high air velocity would only make Q increased but attribute to poor cooling effect. Then, some improved methods of the experimental device were proposed by the theory and experiment. Finally, some comparisons were made between conventional evaluation indicators and the new one proposed in this paper, it can be concluded that each indicator has its own strength and shortages, in the practical application, the proper indicator should be selected according to the demand.