Abstract
The purpose of this study is to improve microbial air quality by improving water quality, particularly concerning microbiological aspects, by applying an ultraviolet water purifier system to a direct evaporative cooling (DEC) system. A direct evaporative cooler is an air cooling technique that uses the evaporation of water. Most DECs recirculate water to reduce water use. Evaporative cooling pads and water are biologically contaminated by recirculating water. This contamination can develop into air contamination and cause respiratory illnesses in occupants. It is necessary to use sterilized water in a DEC to prevent respiratory diseases and maintain air quality. In this study, we examine whether improvements in water quality in a DEC affect air quality by dividing experiments into a control group (Control) and a treated group (UV-treated). In the control group, the degree of contamination was measured when a DEC operated for four weeks without ultraviolet water treatment. In UV-treated, the degree of contamination was measured when UV water treatment was applied to a DEC for four weeks. In both Control and UV-treated, microbes were sampled from the water, the evaporative cooling pad surface, and the DEC inlet and outlet air samples in order to compare the levels of contamination. The surface was measured once at four points, and the air was measured four times at two points. A comparison of the two experiments indicated that the degree of microbial contamination of water and air was significantly reduced in the UV-treated group when compared to that in the control group. When the pollution degree of the evaporative cooling pad was compared to the degree of air pollution, it was difficult to obtain a correlation between the two factors, although the results confirmed that the contamination of the evaporative cooling pad caused water pollution. Therefore, it is necessary to operate a water treatment system to maintain the clean air in DECs.
Highlights
Evaporative cooling technology is a non-vapor compression heating, ventilating, and air conditioning (HVAC) technology that is used as to simultaneously induce the adiabatic cooling of process air with the evaporation of water by performing a heat exchange with water and process air [1]
The study empirically evaluated the improvement of microbial air qualityo on a direct evaporation cooling system
Experiments were performed for four weeks, and each divided into a control group (Control case corresponding to direct evaporative cooler (DEC) that did not recycle water by bypassing the ultraviolet reactor) and experimental groups (UV-treated cases corresponding to DEC that involved recycled water treatment through an ultraviolet reactor)
Summary
Evaporative cooling technology is a non-vapor compression heating, ventilating, and air conditioning (HVAC) technology that is used as to simultaneously induce the adiabatic cooling of process air with the evaporation of water by performing a heat exchange with water and process air [1]. Several studies focus on environmentally-friendly technology that cools the air without using refrigerants [2,3,4,5] One of these evaporative cooling technologies is an indirect evaporative cooler (IEC), which consists of two channels of plastic material: On the secondary air channel, adiabatically cooled air exchanges sensible heat with process air and on the primary air channel, cools the process air. Another one of these technologies is a direct evaporative cooler (DEC), which is a device that induces adiabatic cooling by passing air through an evaporative cooling pad of wet cellulosic material. Legionella bacteria were observed in a dehumidification system by using a lithium chloride solution, according to a principle similar to that of a direct evaporative cooling system [10]
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