冷媒R-22與R-410A在U型平滑與微鰭片管內之冷凝熱傳研究

Condensation heat transfer of R-22 and R-410A in U-bend smooth and microfin tubes

劉政昇(Cheng-Sheng Liu)

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(2012年)

摘要

本研究主旨在探討純冷媒應用在U型平滑與內螺紋鰭片管之冷凝熱傳性能。工作流體為R-22與R-410A，測試區U型彎管位在垂直平面上，上下直管部份為水平，冷媒由上往下流，管外冷卻水與冷媒呈逆向流。測試飽和溫度為30℃與40℃，質量通量50~200 kg/ m2s，入口乾度範圍0.2~0.9，測試區入出口乾度差固定為0.2。管內冷凝熱傳係數由管壁外量測之壁溫計算，共量測七個軸向位置，每個位置量測三點。
實驗結果顯示，冷凝熱傳係數隨著乾度與質量通量增加而上升。R-22在平滑管與內螺紋鰭片管之冷凝熱傳係數皆大於R-410A。使用內螺紋鰭片管可有效提升熱傳效率；相較於平滑管，R-22之冷凝熱傳係數提升63%~120%、R-410A則可提升50%~97%之熱傳效率。在U型管彎管區之熱傳係數平均比上直管提升21%(平滑管)與12%(內螺紋鰭片管)，而整個U型管熱傳係數最佳位置為彎曲段中點(90o)位置。本研究修改文獻水平直管經驗式，修正後之經驗式與實驗數據均方根誤差為9.68%(平滑管)與5.49%(內螺紋鰭片管)。另外，本研究以直管熱傳性能為基準而提出彎管熱傳經驗公式；此經驗公式與實驗數據均方根誤差為9.16%(平滑管)與5.8%(內螺紋鰭片管)。

關鍵字

冷凝熱傳 ； 微鰭片管 ； U型彎管 ； R-22 ； R-410A

並列摘要

This study investigates the condensation heat transfer experiments for two pure refrigerants, R-410A and R-22, in the U-bend smooth and micro-fin tubes. U-bend situated in a vertical plane, including two straight and a bend section. Refrigerants flow from the upper horizontal straight section to the lower horizontal straight section. Experiments were performed at saturation temperatures of 30℃ and 40℃. The mass flux varied from 50 to 200 kg/m2s, and the inlet quality varied from 0.2 to 0.9. The heat transfer rate of the test section was controlled to a decrease of vapor quality of 0.2 in the present experiment.
The test results showed that heat transfer coefficient increased as mass flux and quality increased. Condensation heat transfer coefficient of R-22 was higher than R-410A in both the smooth and microfin tubes. The average condensation heat transfer coefficient of the microfin tubes for R-22 and R-410A were 1.63-2.2 and 1.5-1.97 times larger than those of the smooth tube, respectively. In average, the local heat transfer coefficients of R-22 and R-410A in the bend section were, 1.21 and 1.12 times larger than those in the upper straight section, respectively. The maximum local heat transfer coefficient occurs at the midle (90° position) of the bend. Heat transfer correlations of straight horizontal condensation on smooth and microfin tubes predict the data in this study with r.m.s. 9.68% and 5.49% respectively. A correlation of local heat transfer coefficient of the U-bend section based on the straight tube is provided. It predicts the present data of smooth and finned tubes with r.m.s. 9.16% and 5.8%.

並列關鍵字

Condensation heat transfer ； U-bend ； Microfin tube ； R-410A ； R-22

參考文獻

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