氣冷式冰水熱泵暖房模式運轉之性能測試與分析

Laboratory Examination of Frosting and Defrosting for an Air-to-Water Heat Pump

古瑞成(Jui-Cheng Ku)

指導教授 ： 蘇艾

元智大學/工程學院/機械工程學系/碩士(2000年)

摘要

本論文係對一公稱5冷凍噸之系統進行實機測試，依據中國國家標準進行冷房及暖房運轉之實驗。在實驗過程中，記錄標準條件及結霜過程之暖房能力及性能係數（COP）的變化。文中亦特別探討系統在除霜過程中之動態變化。
研究之測試條件涵蓋—4℃ 至 7℃之室外環境溫度及60％至90％之相對濕度。研究結果提供了暖房模式運轉在結霜及除霜過程中之詳細特性。
實驗結果顯示，在控制策略上，除霜過程中需使低壓保護開關短暫失效，系統才能正常連續運轉。當室外環境溫度降至-4℃時，暖房平均加熱能力為額定加熱能力之62%，而暖房平均性能係數COPh為額定值之71%。入口空氣乾球溫度1.5℃時，相對濕度較高之條件，在暖房模式運轉初期，暖房能力及性能係數COPh高於入口空氣相對濕度較低之運轉條件;但隨運轉時間之增加，霜層亦增加較快，變成熱阻後，暖房能力及性能係數COPh便大幅降低。相對濕度較低之條件，霜層增加較慢，亦延長了除霜間隔時間。

關鍵字

氣冷式熱泵主機 ； 性能係數 ； 相對濕度 ； 除霜 ； 暖房能力 ； 感溫式膨脹閥

並列摘要

An air-to-water heat pump of nominal 5-ton capacity was instrumented and tested in the heating mode under laboratory conditions. The coefficient of performance (COP) and heating capacity of the system were measured during standard and frosting/defrosting conditions, with major emphasis placed on the dynamic frosting operation of the system.
The study encompassed an evaluation of system performance for ambient temperature levels between -4℃ and 7℃ and for discrete relative humidity levels ranging from 60% to 90%. A detailed description of the physical processes that occur during defrost is provided.
The results indicate that low-pressure cutout needs to be overridden during defrosting thus system could run continually without trip. At an ambient temperature of -4℃, the average heating capacity was 71% of the nominal value and the average coefficient of performance was 62% of the nominal COP. With a —1.5℃ ambient air temperature, system COP and capacity improved slightly under condition of higher humidity in the non-frosting period. The frost accumulation on the outdoor heat exchanger increased the resistance thus reduced both system COP and capacity. Ice formation increased more slowly with lower humidity. It results an extended defrost interval.

並列關鍵字

Air-to-Water Heat Pump ； COP ； Relative Humidity ； Defrost ； Heating Capacity ； Thermostatic Expansion Valve

參考文獻

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