بررسی کارآیی مبدل گرمایی کلی احیاشده با جریان دوره ای Performance investigation of regenerative total heat exchanger with periodic flow

1. Introduction As quality of life increases, indoor air quality has received more attention. For a comfortable and healthy indoor environment, ventilation is essential, but large amounts of energy must be consumed to condition outdoor air. Thus, total heat exchangers that recover energy from exhaust air have been designed to reduce the energy needs of buildings and improve indoor air quality. There are two types of classifications for total heat exchangers: the recovery type and the regenerative type. The recovery type exchanges heat at the same time, but the regenerative type exchanges heat at a different time, as shown in Figures 1(a) and 1(b). Most studies have focused on correlations or the materials used for the total heat exchanger [1–10]. Zhang [11] proposed total heat exchangers under uncertainties are optimized by reliability-based single-loop genetic algorithm. Sabek [12] presented total heat exchanger is experimentally investigated, and numerically validated. The variation of membrane surface and/or flow velocity has an important impact on the activation and clogging times. Min [13] discussed four methods to evaluate the performance of a membrane-type total heat exchanger. They are the numerical method with consideration of moisture adsorption heat, the numerical method with no consideration of that heat, the effectiveness-NTU method with consideration of that heat, and the effectiveness-NTU method with no consideration of that heat. Yang [14] first proposed the periodic total heat exchanger, composed of a fixed-plate heat exchanger, two flow passages, and four centrifugal fans. This recovery-type total heat exchanger has a double flow circuit heat exchange device. By the control of four fans, the device can pump fluids in different flowing directions, so that the heat exchange device possesses a double flow circuit for periodic positive and reverse directional pumping. Chang [15] and colleagues investigated the usage of different energy storage materials in the recovery type of periodic total heat exchanger to enhance the device’s performance. Three types of energy storage materials were installed and investigated: activated carbon, aluminum, and a mixture of activated carbon and aluminum. The results showed that adding activated carbon to the device increases latent heat effectiveness by 17.3%. Installing aluminum results in an increase of 15.1% in sensible heat effectiveness. Finally, among the three types of energy storage materials, the device with activated carbon had the best performance, increasing the total heat effectiveness up to 11.7%. For this study, a periodic total heat exchanger based on a regenerative and rotary-type concept was constructed. Fixed wheels were made of the heat and moisture storage materials of aluminum and silica gel, which can store and release energy alternately. These wheels were installed at the center of each flow passage to enhance the thermal performance of the device.