A thermoacoustic heat pump was constructed and tested. It was composed of a looped tube, a straight tube, and a regenerator. The looped tube contained the regenerator and was connected to the straight tube. The tubes were filled with nitrogen. When an acoustic wave was input to the tubes, a temperature difference formed along the regenerator. Our experiments showed that this heat pump could work as both a cooler and a heater. This heat pump achieved −39 °C as a cooler and 270 °C as a heater. Using antifreeze liquid and oil as heat media, the cooling and heating performance of the heat pump was measured within the temperature range from −3 to 160 °C.
A prototype thermoacoustic heat pump working as a heater was demonstrated. The heat pump was composed of an acoustic driver, a branched tube, and a looped tube containing a regenerator; the looped tube was connected to the acoustic driver via the branched tube, and the regenerator consisted of many narrow flow channels. The measurement results of the acoustic impedance inside the looped tube indicated that the energy conversion of the acoustic power flow into the acoustic heat flow in the regenerator occurred through the inherently efficient Stirling cycle. Moreover, the heat pump generated a hot temperature of 370 °C, corresponding to a temperature lift along the regenerator of 340 °C.
The paper reports the results of pilot test on the cooling performance of a direct cross flow mechanical cooling tower located in the Kebili region in the southern part of Tunisia. In this study heat and mass transfer data are measured within the tower over a period of one year and compared with external weather data collected over the same period. The data enabled the influence of different weather conditions on the performance of the cooling tower to be analyzed. The results obtained show that ambient humidity has a greater influence on performance than external temperature. In fact, significantly better cooling performance of about 80% was obtained during the high temperature, low humidity summer months than during the winter period, less than 40%, with relatively low external temperature and high humidity. These results indicate the relative importance of evaporative cooling as compared to convective cooling. The effect of wind on cooling performance was found to be considerable but was confined to those periods when wind direction coincided with the orientation of the louvers of the tower. This was observed to occur only during the summer period when compared to winter period, thus attesting the benefits of the use of proper cooling tower design for improving efficiency and conserve energy.
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