螺旋式壓縮機轉速對效率之影響

Variable Speed Effect on Performance of Screw Chiller

洪國書 ； 劉中哲

《冷凍空調與能源科技雜誌》 79期 (2013/02) Pp. 17-27

摘要

本研究以兩實驗案例配合冰水機性能模擬軟體，分析變頻螺旋式壓縮機轉速與壓縮機容積效率之關係式，預測冷媒質量流率，並以冷媒的多變壓縮過程之壓力、溫度與比容關係式，預測可變轉速螺旋式壓縮機的輸入功與冷媒出口狀態。搭配水冷式冷凝器與滿液式蒸發器的熱傳模型，將三元件建構為一循環後，可於不同運轉條件下，依序計算各元件之質量流率與熱傳量，重複計算直至壓縮機、冷凝器及蒸發器三者之能量平衡收斂，而得到冰水機的最終性能。可變轉速螺旋式壓縮機容積效率模型之參數包括吸氣與排氣壓力、轉子尖端速度等三個，本研究先以壓縮機單體實驗得出此經驗模型，並將其導入性能分析軟體之中。為驗證整合後之性能分析軟體準確度，本研究以一台100 USRT R-134a變頻螺旋式冰水機為對象，由分析軟體預測冰水機全機於四個不同負載、不同運轉條件下之製冷能力與效率，並於實驗室驗證其準確度。模擬與實測比對結果顯示其準確度為95%。最後，再以另一較小排氣量約45 USRT之變頻螺旋式冰水機案例，實測比較在定頻與變頻控制不同操作下之性能，供進一步進行中的研究作為有力的參考。

關鍵字

可變轉速螺旋式壓縮機 ； 冰水機模擬軟體 ； 冰水機

並列摘要

In this study, two variable speed screw chillers and a screw compressor performance model has been used. It predicted the refrigerant mass flow rate by volumetric efficiency model and predicted the compressor input power and the refrigerant outlet status by the relationship of pressure, temperature and specific volume of polytropic process. It was integrated with the heat transfer models of a water-cooled condenser and flooded evaporator to become a chiller cycle simulation software. There were three main parameters in variable speed screw compressor volumetric efficiency model which were the suction pressure, discharge pressure and the male rotor tip speed. In this study, this model was derived by a compressor monomer experiment, and then was imported to the performance software. To verify its accuracy, a 100 USRT R-134a variable speed screw water chiller was tested at four different loads and three different operating conditions in the laboratory. The test results of cooling capacity and efficiency were be compared with the predicted results. The results showed an accuracy of about 95%.Finally, a 45 USRT VFD screw chiller was measured to compare with the performance of constant speed chiller under different operating conditions, as a strong reference for further study.

並列關鍵字

variable speed screw compressor ； chiller simulation ； chiller