EXPERIMENTAL INVESTIGATION OF A TWO-STAGE INDIRECT/DIRECT EVAPORATIVE COOLING SYSTEM IN DIFFERENT CLIMATIC CONDITIONS

Abstract

Low-energy systems are currently of considerable interest, with the increasing realization of the limits of available energy resources. So, there are many types of research about cooling know-hows which cause a weighty decrease in energy utilization in the HVAC domain. For this reason, an investigation of one of these promising technologies called Indirect evaporative cooling was conducted. The IEC is well suited to arid areas to attenuate the peak demand for electricity, largely attributed to the operation of DX air conditioners during summer afternoon hours. The indirect evaporative heat exchanger is the most important of the components in an IEC-based cooler, since it is the main source of cooling. The main components of the indirect evaporative cooler are two ventilators, a plastic plate heat exchanger and a cold-water pump. The heat exchanger is of the crossflow design with air in the primary flow (room air supply) passages traveling in a horizontal direction, and in the secondary (exhaust air) passages in a downward vertical direction. Cooling is obtained by a ventilator that blows hot outside air through the primary passages, while cold water is sprayed over the secondary airway on top of the heat exchanger. The supply air is cooled with no pick- up of moisture as it passes through the main flow passages. The exhaust air is drawn through the secondary flow passages and discharged with water evaporating to the atmosphere. The main problem with using evaporative coolers is that they are limited to the inlet wet bulb temperature so there are many kinds of research on the types of the indirect evaporative coolers that go below the WBT like the regenerative IEC, The dew point IEC, The M-cycle (which is the most complicated one) and the hybrid system (IEC/DEC). In our factory Volta Egypt, we already produce the direct type so we find it is more interesting to test the hybrid system as it is the easiest to conduct, has the highest effectiveness (based on many types of research), and will enable us to improve the efficiency of our direct evaporative cooler. To achieve this purpose a two-stage Indirect/Direct evaporative cooling system was constructed to test its cooling performance under different climatic conditions. The two-stage Indirect/Direct evaporative experimental test rig consists of two stages. the first one is an indirect evaporative cooling stage then the direct evaporative one. To provide the selected outdoor conditions of primary and secondary air in different Egyptian cities two air simulators are used. Outcomes demonstrate that the efficiency of IEC/DEC element differs over a variety of 95–118%. While the efficiency of IEC stage differs over a variety of 50– 80%. Characteristics of attaining power saving and comfort circumstances have been examined. With respect to the evaporative relief region, this arrangement can deliver relief condition in an enormous area in Egypt wherever direct evaporative without help is not capable of providing summer relief condition. Further than 50% of energy saving could be attained by this arrangement in contrast with Traditional cooling technologies like mechanical vapor compression systems. While water consumption in this system is bigger than the direct one only but the total power saving covers this demerit. As a naturally clean and energy effective system, it is capable of filling the gap between mechanical vapor compression systems and the direct evaporative cooling.