含油冷媒R-245fa應用於滴淋式蒸發器之熱傳性能研究

A Heat Transfer Study of Oil-R-245fa Mixture In Spray Type Evaporator

蔡岳霖(Yueh-Lin Tsai)

指導教授 ： 簡良翰

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(2010年)

https://doi.org/10.6841/NTUT.2010.00542

摘要

本研究主旨探討含油濃度及低壓冷媒R-245fa應用於滿液式、滴淋式兩種蒸發器之熱傳性能分析。工作流體為R-245fa，使用圓管打孔進行滴淋蒸發實驗，測試飽和溫度為20oC與5oC，使用之潤滑油為EMKARATE RL -150S，含油濃度為1%、2%與5％，測試管分別為光滑管及60FPI的鰭片管，鰭片高為0.4mm，改變熱通量範圍為6~50kW/m2，流量範圍為0.012~0.04kg/ms。
結果顯示，在純冷媒實驗中，鰭片管在任一飽和溫度下，滴淋蒸發的熱傳性能較池沸騰高。R-245fa之池沸騰性能與R-123冷媒相近，為極佳的冰水機替代冷媒。在含油冷媒實驗中，光滑管應用於池沸騰時，熱傳性能隨著含油量的增加而下降，而應用於滴淋蒸發時，則是在低熱通量時熱傳性能佳，而高熱通量則是略為下降；鰭片管則是無論何種機制，熱傳性能皆是呈現隨含油率增加而上升。因此，含油率對於熱傳性能之影響隨測試管的表面結構不同而異，而在滴淋蒸發時，測試管的位置可影響滴淋狀態而成為主要因素之一。本實驗之薄膜蒸發熱傳係數之預測值其誤差皆在±20%以內；含油冷媒熱傳係數修正公式之預測值誤差在±35%以內。

關鍵字

含油濃度 ； 滴淋式蒸發器 ； 薄膜蒸發

並列摘要

This study investigates the evaporation heat transfer performance of R-245fa and R-245fa with lubricant RL -150S mixture (1%, 2% and 5% lubricant mass fraction) in pool boiling and falling film. Two kinds of tubes, a smooth tube and a fin tube of 0.4mm fin height, 60FPI(Fins Per Inch) were tested. Experiments were performed at saturation temperatures of 5, 10 and 20oC. The liquid flowed through a liquid feeder with a row of circular holes at a rate of 0.012 ~ 0.04kg/ms, and heat fluxes varied from 6 to 50kW/m2.
For pure refrigerant, the results show that falling film heat transfer coefficient is better than pool boiling with fin tube. The heat transfer coefficient of R-245fa is similar to R-123. Hence, R-245fa is a good refrigerant to replace R-123. For pool boiling in R-245fa-oil mixtures, different results are shown in smooth and fin tube. The heat transfer coefficient of smooth tube decreases with increasing oil concentration. The smooth tube has a greater heat transfer coefficient at low heat flux than in falling film, but the performance slightly decreases at high heat flux. The fin tube has the same tend in pool boiling and falling film, the heat transfer coefficient increases with increasing oil concentration. The performance of refrigerant-oil mixtures depends on the tube surface structure. For falling film evaporation, the falling fluid flow pattern depends on tube location. Hence, the tube location is an additional factor on performance. A heat transfer correlation of falling film evaporation on smooth tube, which predicts the data in this study within

並列關鍵字

refrigerant-oil mixtures ； falling film evaporation ； falling film

參考文獻

[12] 陳榮鴻、簡良翰，“鰭片構造之滴淋蒸發熱傳性能研究“，國立台北科技大學碩士學位論文，台北，2009。

[22] 吳忠駿、簡良翰，“網格式鰭片尺寸與含油冷媒物性之沸騰性能參數研究”，國立台北科技大學碩士論文，台北，2009。

[35] Chien, L. H., and Cheng, C. H., 2006, "A Predictive Model of Falling Film

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