介電液於梯形狀微流道熱沉之冷凝熱傳增強研究

Enhanced Condensation Heat Transfer for Dielectric Fluid within Trapezoid Micro-Channel Heat Sink

陳建佑(Chuan-Yu Chen)

指導教授 ： 廖英皓 ； 王啟川

國立交通大學/工學院/機械工程系所/碩士(2018年)

摘要

本研究以實驗的方法探討介電液體HFE-7100在微流道熱沉內之冷凝熱傳特性，其水力直徑為1200 μm，並固定出口壓力為140 kPa，冷凝熱通量為120W；而實驗參數有質量通率(150 – 250 kg/m2s)、蒸汽乾度(0.1 – 0.8)和不同的擺放方式(-90°垂直往下流動至90°垂直往上流動)。除此之外，本研究提出排水流道概念，在原本流道中間再加工出一梯形排水流道，透過排水流道之表面張力的影響，使得冷凝液體往排水流道移動，進而讓微流道中冷凝液膜厚度變薄提升熱傳效率。研究結果顯示，在質量通率100 kg/m2s時，具排水流道之微流道熱沉，除了可以增加兩相冷凝熱傳外，亦可以降低摩擦壓降；其熱傳係數增加約17%，摩擦壓降降低約30%，而質量通率150 kg/m2s時，熱傳係數增加約20%，摩擦壓降降低約25%，隨著質量通率的增加，當質量通率來到200kg/m2s時熱傳增益開始降低，熱傳係數增加約5%，而質量通率250kg/m2s時熱傳效果反而變得更差。

關鍵字

冷凝熱傳增強 ； 角度效應 ； 微流道熱沉 ； HFE-7100

並列摘要

This study experimentally investigates the condensation performance of the HFE-7100 within a multiport micro-channel heat sink with a hydraulic diameter of 1200 μm. The experiment is conducted at a fixed outlet pressure of 140 kPa with condensation heat flux of 120W. The condensation tests are carried out with mass fluxes ranging from 150 to 250 kg/m^2 s, vapor mass quality from 0.1 to 0.8 and inclined arrangement from -90° (vertical downward) to 90° (vertical upward). In addition, the present study proposes enhanced condensation design via a micro-drainage cavity sitting in the middle of the conventional microchannel. Through this design, the condensate drainage is improved and condensation heat transfer is improved with additional benefit of lower pressure drop. The results show that the micro-channel heat sink with drainage channels is especially effective at lower mass flux like 100 kg/m^2 s, yielding 17% augmentation in heat transfer coefficient and a reduction of frictional pressure gradient by 30%. Similar results prevail when the mass flux is 150 kg/m^2 s, and 20% improvement of heat transfer coefficient and 25% lower pressure gradient can be achieved. However, the design offers negligible improvements with higher mass flux higher than 200 kg/m^2 s. This is because flow inertia takes control, and the effect of surface drainage is significantly impaired.

並列關鍵字

enhancement of condensation heat transfer ； the effect of inclination ； mini-channel heat sink ； dielectric fluid

參考文獻

[1] Serizawa, A., Feng, Z., and Kawara, Z., 2002, "Two-phase flow in microchannels," Experimental Thermal and Fluid Science, 26(6-7), pp. 703-714.

[2] Coleman, J. W., and Garimella, S., 2003, "Two-phase flow regimes in round, square and rectangular tubes during condensation of refrigerant R134a," International Journal of Refrigeration, 26(1), pp. 117-128.

[3] Shin, J. S., and Kim, M. H., 2004, "An experimental study of condensation heat transfer inside a mini-channel with a new measurement technique," International Journal of Multiphase Flow, 30(3), pp. 311-325.

[4] Shah, M. M., 1979, "A general correlation for heat transfer during film condensation inside pipes," International Journal of heat and mass transfer, 22(4), pp. 547-556.

[5] Akers, W., "Condensation inside horizontal tubes," Proc. Chem. Engg. Prog. Symp. Ser., pp. 145.