日本機械学会論文集
Online ISSN : 2187-9761
ISSN-L : 2187-9761
熱工学,内燃機関,動力エネルギーシステム
プレート式熱交換器における超臨界圧HFO1234ze(E)の冷却熱伝達特性
宮田 一司森 英夫谷口 隆寛梅沢 修一杉田 勝彦
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2017 年 83 巻 855 号 p. 17-00280

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For the development of industrial heat pump systems supplying high-temperature heat source over 130 °C, experiments were carried out on cooling heat transfer of supercritical pressure HFO1234ze(E) flowing in a plate-type heat exchanger (PHE). HFO1234ze(E) with low Global Warming Potential (GWP) is expected as an alternative to refrigerant HFC134a. In the experiment, heat transfer coefficient data were obtained at different pressures including a near-critical pressure condition. To obtain the heat transfer coefficient, an integral method was used for evaluating the mean temperature difference between the refrigerant and cooling water in the PHE. Based on the measurements, characteristics of cooling heat transfer of supercritical pressure HFO1234ze(E) in the PHE were clarified. Generally, heat transfer coefficient showed considerably large values compared with tube flow, attributed to strong turbulence or agitation promoted by corrugated geometry of the PHE plate, and reached a maximum in the vicinity of the pseudocritical point. As the pressure approached the critical pressure, the peak of heat transfer coefficient became higher at lower bulk enthalpy, reflecting the pressure dependence of isobaric specific heat of the refrigerant. These results mean, even in the pseudocritical region where strong temperature dependency of physical properties appears, properties change in the flow cross section was small compared to the tube flow, although not negligible. The correlation developed in the previous study overestimated the measured heat transfer coefficient in the pseudocritical region for the pressure of the reduced pressure 1.01 very close to the critical pressure and also in the enthalpy region near to and lower than the pseudocritical point for the pressures of the reduced pressure about 1.1 or higher. For the better prediction, the necessity to consider the small but non-negligible properties change in the flow channel cross section was recognized.

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