| 题名 |
冷媒R1234yf與R134a在扁平管與光滑圓管之管內壓損實驗分析 |
| 并列篇名 |
An experimental and analytical study on pressure drop of R1234yf and R134a inside flattened tube and circular tube |
| DOI |
10.29911/JEHVACE_NEW.202201_(131).0004 |
| 作者 |
簡良翰(Liang-Han Chien)；蔡維仁(Wei-Jen Tsai)；蔡牧安(Mu-An Tsai) |
| 关键词 |
冷凝熱傳 ； 扁平管 ； 壓損 ； 流場觀測 ； Condensation heat transfer ； Pressure drop ； R134a ； R1234yf |
| 期刊名称 |
冷凍空調&能源科技 |
| 卷期/出版年月 |
131期（2022 / 01 / 10） |
| 页次 |
40 - 46 |
| 内容语文 |
繁體中文 |
| 中文摘要 |
本研究主要在探討純冷媒於扁平管內的冷凝熱傳性能以及管內壓損。工作流體為R134a與其替代冷媒R1234yf，測試段分為圓雙套管熱交換器與橢圓雙套管熱交換器。橢圓雙套管熱交換器之長軸採垂直放置，內管為長寬比1.87的扁平管。測試飽和溫度為28°C 與38°C，質量速度為100～500 kg/m^2s，乾度為0.1～0.9，出入口乾度差為0.1～0.2根據質量速度而有所不同。實驗結果顯示隨著乾度與質量速度的增加熱傳係數也會隨之上升。兩種冷媒在扁平管的管內冷凝熱傳係數皆高於圓管，平均高出3.3～6.7%。R134a的管內冷凝熱傳係數皆高於R1234yf，平均高出8.1%～16%。冷凝熱傳係數隨著飽和溫度的降低而升高，壓損部分也是隨著飽和溫度的降低而上升。扁平管的摩擦壓損較圓管高15.7～25.6%。扁平管冷凝熱傳實驗數據與文獻中之圓管冷凝經驗公式比較後，發現以扁平管水力直徑為特徵長度可利用圓管冷凝經驗公式準確預測（均方根誤差8.21%以內）；而預測壓損時，因兩側長邊壁面剪應力受重力影響較為顯著，則需以長軸為特徵長度較為準確，實驗與文獻中圓管壓損經驗公式比較之誤差均方根約25.19%，本研究提出可適用於扁平管與圓管壓損預測的修正經驗公式，其預測誤差均方根可降至13.45%。 |
| 英文摘要 |
This study mainly discusses the condensation heat transfer performance and pressure drop of pure refrigerants in flattened tubes. The working fluid is R134a and its substitute refrigerants R1234yf. The test sections are a circular double pipe heat exchanger and an elliptical double pipe heat exchanger. The long axis of elliptical double pipe heat exchanger is in vertical direction in this experiment. The aspect ratio of the flattened tube in the elliptical double pipe heat exchanger is 1.87. The saturated temperature in the tests is either 28 degrees Celsius or 38 degrees Celsius, and the mass velocity is 100~500 kg/m^2s. The quality varies between 0.1 and 0.9, and the difference of quality between the inlet and the outlet is 0.1 to 0.2, depending on the mass velocity. The experimental results show that the heat transfer coefficient increases with the increase of the mass velocity and quality. The condensation heat transfer coefficient of both refrigerants in the flattened tube is higher than that in the circular tube by 3.3~6.7%. The condensation heat transfer coefficient in the tube of R134a is higher than R1234yf by 8.1%~16%. The condensation heat transfer coefficient increases with the decrease of saturated temperature, and the pressure drop also increases as the saturation temperature decreases. The frictional pressure loss of a flat tube is higher than that of a circular tube by 15.7~25.6%. The experimental data of the flattened tube is compared with the correlations of circular tubes, and found that the condensation heat transfer coefficient is well predicted within 8.21% by the circular tube correlations using hydraulic diameter as the characteristic length. However, the long axis should be used as the characteristic length in the prediction of pressure drop because the gravity effect on the vertical wall of the long sides is more significant. The mean square error of the prediction of correlations for pressure drop of circular tube are about 25.19%. A modified correlation of pressure drop for both flat tube and circular tube is proposed. The mean square error of the prediction by the modified correlation is 13.45%. |
| 主题分类 |
工程學 >
電機工程 |
| 参考文献 |
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