期刊名称：Bulletin of the Institute of Heat Engineering
印刷版ISSN：2083-4187
出版年度：1995
卷号：80
页码：29-52
语种：Polish
出版社：Warsaw University of Technology
摘要：The application of storage tank with double medium (water and phase change material - PCM) can significantly improve Solar Domestic Hot Water (SDHW) system performance. In the considered construction of SDHW system, storage tank is filled up with thin-walled polyethylene spheres enclosing stearine. The tank with vertical tubes containing stearine was also built and experimentally tested. The stearine was chosen as a PCM material due to its commercial availability and comparatively low price. The thermal properties of employed material were obtained from calorimetric Differential Thermal Analyser (DTA). The stearine shows phase change spread over temperature range from 35 to 48°C with accompanying heat effect 160 kJ*kg-1. The paper presents mathematical model of main system components. The mathematical model of overall storage tank is modified mixing multi-zone model. The thermal stratification, heat transfer from water to PCM elements and tank heat losses have been taken into account. Therefore, the mathematical model of transient heat transfer with simultaneous phase change in single spherical and tube element filled up with PCM was worked out. An own enthalpy method for this problem solution has been carried out. Presented results of numerical calculations were compared with experimental data showing satisfactory agreement. The included calculations for such system working under Polish climatic conditions show a major influence of PCM material inside the storage tank on instantaneous heater efficiency. The storage tank with water and PCM can more successfully collect energy when working in the sequence of several sunny days in comparison with traditional water tank.
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