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Effect of Heat Transfer among Adsorbent Particles on the Performance of a Multi-Bed Adsorption Heat Pump with Finned-Tube Adsorbers
|作者:||沈君洋||關鍵字:||應用研究;adsorption heat pump;能源工程, 機械工程類;吸附式熱泵;冷卻能力;COP;鰭管;矽膠;specific cooling power;COP;fin tube;silica gel||摘要:||
此計畫擬針對一個由此研究單位設計組裝之多床吸附式熱泵(圖1)進行詳細之模擬分析，此系統中包含四個吸附器、一個冷凝器、一個蒸發器與一個膨脹裝置(圖2) 。在一個週期循環中，每一個吸附器均歷經吸附、預熱、再生與預冷等四個過程(圖3 與4)，吸附器由鋁合金鰭管(圖5)組成，鰭片間放置矽膠，並以金屬網套包覆。先前之研究乃使用一個具固體側質傳擴散阻力之模式，以分析吸附器中之熱質傳，平均之矽膠顆粒溫度與水份濃度乃被採用，此模式雖然適用於分析任何型式吸附器中之熱質傳，但無法知悉矽膠顆粒間之溫度與水份濃度之梯度對整體熱質傳之影響。此計畫乃提出一個較為複雜之模式進行分析，在此模式中，每一對鰭片間之矽膠均分析其徑向與軸向溫度與含水濃度之差異，以了解其對整體熱質傳之影響，此資料之獲得有助於鰭片節距與高度之設計，因此對此熱泵之發展是極為重要之工作。此研究亦將對原有之實驗系統進行改良，原有系統中之四個吸附器乃由共通管分別連結至蒸發器與冷凝器(圖1)，而在操作過程中，因為會有兩個吸附器同時進行吸附或再生之時段，此可能造成蒸氣在兩個吸附器間互流，而影響系統性能，故研究中將直接銜接每個吸附器至蒸發器與冷凝器，同時進行系統性能量測，量測資料並將與分析結果進行比較。
A detailed analysis of the COP and specific cooling power of a multi-bed adsorptionheat pump (Fig. 1), designed and assembled by the Mechanical Engineering Department ofNational Chung Hsing University, is proposed. The adsorption heat pump contains fouradsorbers, one condenser, one evaporator and one expansion device (Fig. 2). During a cyclicoperation, the adsorbers consecutively and orderly proceed to four different modes -adsorption, preheating, regeneration and precooling (Figs. 3 and 4). The adsorber iscomposed of aluminum fin tubes (Fig. 5). Silica gel is filled between the fins which arecovered by metal wire mesh. In previous work, a solid-side mass-diffusion resistance modelwas adopted to analyze the overall heat and mass transfer in the adsorber. This model can beapplied to any type of adsorbers. But using this model, the result of the analysis can notprovide any information on the effect of temperature gradient and water content gradient inthe packed silica gel particles on the overall heat and mass transfer. In this work, a morecomplicate model than the previous one is proposed. In the model, the deviation of theradial-direction and axial-direction temperature and water content of the silical gel particlespacked between two neighboring fins will be considered. The effect of the temperaturegradient and water content gradient on the overall heat and mass transfer in the adsorber willbe analyzed. The acquired data will be useful to designing fin pitch and fin height of the fintube and thus it is crucial to the development of this adsorption heat pump. An experimentalwork on the improvement of the multi-bed adsorption heat pump is also proposed. In thepresent system, the four adsorption heat pumps are connected to the evaporator through acommon connector, as well as they are connected to the condenser through another commonconnector. In the operation of the adsorption heat pump, during a certain time period, twoadsorbers would undergo the adsorption mode and another two adsorbers would undergo theregeneration mode. In this time period, due to the deviation of the vapor pressures, a commonconnector could result in a vapor flow between the two adsorbers operating at the same mode.Consequently, it could deteriorate the specific cooling power of the adsorption heat pump. Inthe proposed work, each adsorber will be individually connected to the evaporator andcondenser. The performance of the improved system will be measured and the measured datawill be compared to the result obtained from the computer analysis.
|Appears in Collections:||機械工程學系所|
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