電子膨脹閥應用於跨臨界CO2熱泵熱水系統之最佳控制策略的研究

Optimal control strategies for electronic expansion valve applied to trans-critical CO2 heat pump systems

黎偉程(Wei-Cheng Lee)

指導教授 ： 李宗興

國立臺北科技大學/機電學院/能源與冷凍空調工程系碩士班/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00501

摘要

熱泵因具有效率佳、省能等優點，近年來已愈來愈引起人們重視及廣泛的利用。傳統熱泵系統的冷媒選用上，仍以HCFCs/HFCs為主，由於地球暖化與溫室氣體效應關係，低GWP冷媒的選用，勢必是未來的趨勢。CO2冷媒為自然冷媒，具有低GWP的特性，且無毒、取得容易等優勢，適合當下一代的冷媒。由於冷媒CO2在跨臨界區循環流動，所以其節流機構的進出口壓力和壓差比常規熱泵系统冷媒的節流装置的要高的多，而電子膨脹閥具有體積小、精確控制的優點，適合應用於跨臨界CO2熱泵熱水系統。
本研究以理論分析及實驗驗證方式探討電子膨脹閥開度控制對跨臨界CO2熱泵熱水系統性能之影響。研究發現氣冷器出口溫度與氣冷器出口高壓有特定關係：在溫度低於CO2臨界溫度，最佳性能係數存在在壓力74.8bar；氣冷器出口溫度高於CO2臨界溫度，氣冷器出口溫度與氣冷器出口高壓為線性關係。依此關係本研究以電子膨脹閥為對象，氣冷器出口溫度和出口壓力為控制參數，應用在跨臨界CO2熱泵熱水系統得到最佳控制策略。當CO2熱泵熱水系統在熱水出水需求條件保持不變下，依此電子膨脹閥控制策略操作隨負載變動下均可達CO2熱泵熱水系統性能最佳化之要求，達成節約能源的目的。

關鍵字

CO2熱泵 ； 電子膨脹閥 ； 性能係數 ； 最佳控制策略

並列摘要

Heat pump with high efficiency and energy-saving advantages in recent years has become more and more a source of attention and a wide range of uses. Traditional heat pump system with refrigerant selection, still dominated by HCFCs/HFCs, due to the relationship between global warming and the effects of greenhouse gases, selection of low GWP refrigerant, is bound to be the trend of the future. As a natural refrigerant CO2 refrigerant, have characteristics of low GWP, and advantages in non-toxic, made easy, fit to be the next generation of refrigerants. Due to the refrigerant CO2 flow in trans-critical cycle, so its import and export pressure and differential pressure than conventional throttle body throttle device of heat pump system with refrigerant to be much higher, and electronic expansion valve with the advantages of small size, precise control, suitable for application in trans-critical CO2 heat pump hot water system. This research to theory analysis and the experimental validation way discussion electronic expansion valve opened degrees control on trans-critical CO2 heat pump hot water system performance of effects, research found gas cooler export temperature and gas cooler export high pressure has specific relationship, and according to gas cooler export temperature and gas cooler export pressure for control parameter implementation electronic expansion valve on trans-critical CO2 heat pump hot water system of best control policy. To develop electronic expansion valve control strategies to meet the condition of CO2 heat pump hot water system for a variety of actions, under the hot water demand conditions remain unchanged, and so on electronic expansion valve control strategy under the operation, with the load requirements up to performance optimization under change, for energy-saving purposes.

並列關鍵字

CO2 Heat Pump ； Trans-critical CO2 Cycle ； Electronic Expansion Valve ； COP

參考文獻

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