Correlation of cooling efficiency and media porosity & transport phenomena of direct evaporative cooler
Abstract
Direct evaporative cooling (DEC) uses evaporating water, combined with a wetted medium to cool the temperature of air as it passes through. Evaporative cooling devices can reduce the energy consumption of HVAC&R (Heating, Ventilating, Air Conditioning, and Refrigeration Equipment). Heat is absorbed whenever water is evaporated and converted to water vapor. By passing through or around a wetted surface, heat is removed from the surrounding air in the vaporization of the water. The process approximates the adiabatic-saturation process and the path lies on a constant wet-bulb temperature which is a constant enthalpy line. This thesis consists of two major researches; one is the study of correlation of Direct Evaporative Cooling efficiency with media porosity. The wetted surface area in DEC depends on porosity and absorptivity of the media. The thesis evaluates the effect of media porosity on performance of a Direct Evaporative Cooling system. In this experimental work, the porosity is varied by changing the packing density and volume of media. The packing material allows air and water to come in direct contact. Holding all other variables like mass flow rates and inlet dry-bulb temperature constant, the effect Porosity on DEC performance is studied. The performance of DEC system is a function of porosity, dry- and wet-bulb temperatures and relative humidity. Efficiency increases with porosity. The other research is focusing on relationship between system parameters and cooling efficiency. Effects of three system parameters on cooling performance were evaluated. The three parameters selected for focus were the speed of frontal air, the dry-bulb temperature of frontal air, and the temperature of the incoming water. Each parameter was varied while holding all other variables like air, water mass flow rates and so on constant respectively, and data was collected using several different levels of each parameter. The general relationship between each parameter and efficiency was determined by graphing the data collected and observing trends. The empirical correlation between supply frontal air velocity and cooling efficiency for DEC system in a typical applied environment was established and verified by experiment data. Within certain ranges, DEC cooling efficiency increases with frontal air dry-bulb temperature; decreases with frontal air velocity and incoming water temperature correspondingly.
Degree
M.S.E.
Advisors
Nnanna, Purdue University.
Subject Area
Civil engineering|Mechanical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.