Abstract
The aim of this study is to determine which of the heat exchangers is characterized by the highest efficiency in different applications. Various types of evaporative air coolers were compared: a typical counter-flow unit, the same unit operating as a heat recovery exchanger, a regenerative unit and a novel, modified regenerative exchanger. The analysis includes comparing the work of evaporative heat exchangers during summer and winter season. The analysis is based on the original mathematical models. The numerical models are based on the modified ε-NTU (number of heat transfer units) method. It was established that selected arrangements of the presented exchangers are characterized by the different efficiency in different air-conditioning applications. The analysis faces the main construction aspects of those evaporative coolers and also compares two above-mentioned devices with modified regenerative air cooler, which can partly operate on cooled outdoor airflow and on the exhaust air from conditioned spaces. This solution can be applied in any climate and it is less dependent on the outdoor conditions. The second part of the study focuses on winter season and the potential of recovering heat with the same exchangers, but with dry working air channels. This allows establishing their total potential of generating energy savings during the annual operation.
Highlights
The rise in living standards is leading to increased air-conditioning demand, especially in the summer time in high temperature areas
Comparison between the counter-flow and the regenerative exchanger. (a) Operation ambient air- outlet air temperatures; (b) operation on ambient air- obtained cooling capacity; (c) on ambient air- outlet air temperatures; (b) operation onchannels) ambientand airobtained cooling capacity; counter-flow exchanger operating on exhaust airflow (wet ambient air, (c) counter-flow on exhaust airflow and ambient, regenerativeexchanger exchanger operating operating only on ambient air- outlet air temperatures; and (d)air counter-flow regenerative exchanger on(wet ambient air- outlet air temperatures; and (d) counter-flow exchanger operating operating on exhaust only airflow channels) and ambient air, regenerative exchanger operating on ambient obtained cooling exchanger operating on only exhaust airflowair(wet channels) ambient air, regenerative exchanger operating only on ambient air- obtained cooling capacity
Comparison of the novel exchanger with counter-flow and regenerative unit. (a) Comparison with the counter-flow exchanger operating on exhaust airflow; (b) Comparison with the with the counter-flow exchanger operating on exhaust (b) Comparison with the regenerative air regenerative air cooler operating on ambient air; (c)airflow; Comparison with the regenerative air cooler cooler with operating on ambient air; (c)
Summary
The rise in living standards is leading to increased air-conditioning demand, especially in the summer time in high temperature areas. One of the most effective cooling solutions for indirect evaporative air-cooling are the counter-flow cycles [1,2,3]. The counter-flow exchanger can operate as a heat recovery unit in conjunction with a standard cooling coil from mechanical compression system. This solution can be applied in any climate and it is less dependent on the outdoor conditions. The last system is a novel combination of heat recovery counter-flow exchanger operating with cooling coil and a regenerative heat exchanger. The novel solution is a compromise between a regenerative exchanger and a counter-flow exchanger operating with a cooling coil.
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