Theoretical Analysis of Geometrically Modified Dew Point Evaporative Cooler

Abstract

Human thermal comfort being one of major aspect of increasing demand of energy consumption for heating, ventilation and air conditioning (HVAC) sector. The vapor compression refrigeration systems are predominantly used in the conditioning of the air. Such systems are energy intensive on account of the mechanically driven compressor, hence, not to be considered as a long-term option. It is the need of an hour to propose alternative and sustainable method for the cooling requirements. The evaporative cooling is considered one of alternative cooling method. Such technique helps to cool the incoming air only up to the wet bulb temperature of the air. The continuous development in the past have proposed the indirect cooling methods to achieve the purpose. This method helps to achieve the temperature closer to the dew point temperature of the incoming air. Dew point evaporative cooler is an indirect evaporative cooling (IEC) technique to lower temperature of incoming air below its wet bulb temperature and near to dew point temperature. Performance parameters of dew point evaporative cooler are significantly influenced by configuration and structural arrangement of heat exchanger. The different arrangements of heat exchangers commonly used are counterflow, cross flow and counter-cross flow. This work presents performance analysis of geometrically modified dew point evaporative cooler. The commonly used geometries for the construction of heat and mass exchangers are flat plates, corrugated plates, plates with the perforations etc. In this work, the plate geometry shape is modified to corrugated trapezoidal plates for the theoretical analysis. The modified geometry helps to provide more heat exchange area for the same heat exchanger volume. The cooling efficiencies and temperatures at the outlet of the cooler were investigated for different intake air temperatures and moisture content. The incoming air temperatures are varied from 25°C to 45°C and moisture content from 7 g/kg to 26g/kg for the fixed inlet velocity of 2.5 m/s. The wet bulb and dew point efficiencies ranged from 80% to 131% and 58% to 89% respectively. The trapezoidal corrugated plates predict 17.5 % and 8.5% higher wet bulb efficiency as compared to flat plates and corrugated plate, while the dew point efficiency remains almost same.