探討渦流管能量傳遞與提升冷卻效率之研究

Parameters Optimizing and Investigation of Thermal Separation in Vortex Tube Using CFD Method

俞木凱(Mu-Kai Yu)

指導教授 ： 蔡國隆

國立臺北科技大學/機電學院/車輛工程系所/碩士(2014年)

摘要

本文使用計算流體力學商用軟體ANSYS CFD/Fluent，以穩態流場數值模擬的方式，探討渦流管內部能量分離的因素及外型參數對於渦流管冷卻效率之特性影響。渦流管為一個單純的機械部件，將高壓空氣注入渦流管內後，能分離兩道不同溫度之氣流，且具有體積小，結構簡單，啟動時間短等優點，可應用於特殊冷卻或製熱需求的領域。本文將分為兩部分，其一由速度、壓力與密度層面推論因流體在內部高速旋轉，流體剪應力以及氣體膨脹使得能量分離產生溫度的變化。
其二為改變冷卻管道之幾何，提升渦流管冷卻的效率。數值模擬探討之參數包括性能係數(COP)、等熵效率(η_is)、冷熱端之能量分離功率(Q ̇)、渦流管入口質量流率與冷端出口質量流率之比值(CF)、冷端出口溫度(Tc)、熱端出口溫度(Th) 、與冷熱端出口溫度之差(ΔT)、噴嘴夾角θ。研究結果顯示，能量分離可分為兩區段，冷端溫度主要受到氣體膨脹的影響，而熱端溫度主要受流體剪應力影響，而由於渦流管內流體角速度極大，影響程度以切線剪應力為主；當噴嘴夾角θ為5°時，能產生最低溫度，發生於CF為0.2至0.3的區間，而最大溫度差異則發生於CF為0.7左右，與傳統切線型態之渦流管能夠提升約5%的冷卻性能，而超過5°後因流體的旋轉速度將低，冷卻性能逐漸下降。

關鍵字

計算流體力學 ； 渦流管 ； 渦漩流

並列摘要

Vortex tube is a simple mechanical for energy separation. Vortex tube can produce two separate high pressure flow and low-pressure flow by compressed air. The tube can output two different temperature cold outlet and hot outlet without any media or power drive. It is Very comply with environmental requirements. Changing the geometry, the minimum temperature can be drop to forty below zero.
In this research, use the CFD to find the effect to vortex tube by change the geometry. Two types of vortex tube is determined. One is counter-flow vortex tube the other is uni-flow or parallel flow vortex tube. Counter-flow vortex efficient is more than parallel flow vortex tube. So in the study, we choose counter-flow vortex, it can called normal type vortex tube. When the compressible into the vortex tube. A vortex will be created in tube wall, it called force vortex. In center of tube, the other vortex will be created, it called free vortex. Because the high speed spin in the tube, the compressible flow influence by gravity and fluid viscosity, the density cause the air endothermic and the temperature will be separated. Can be observed at the stagnation point flow, when the system in steady state. It is disclosed that the inlet pressure and the cold fraction are the important parameters influencing the performance.
For this study, when angle of nozzle is 5 degree, it cause the minimum temperature will show at CF=0.2.And it have the best performance.

並列關鍵字

CFD ； vortex tube ； vortex flow

參考文獻

[6] J. Hartnett and E. Eckert, "Experimental study of the velocity and temperature distribution in a high-velocity vortex-type flow," Trans. ASME, vol. 79, pp. 751-758, 1957.

[1] S. Eiamsa-ard and P. Promvonge, "Review of Ranque–Hilsch effects in vortex tubes," Renewable and sustainable energy reviews, vol. 12, pp. 1822-1842, 2008.

[2] K. Stephan, S. Lin, M. Durst, F. Huang, and D. Seher, "An investigation of energy separation in a vortex tube," International Journal of Heat and Mass Transfer, vol. 26, pp. 341-348, 1983.

[3] M. Kurosaka, "Acoustic streaming in swirling flow and the Ranque—Hilsch (vortex-tube) effect," Journal of Fluid Mechanics, vol. 124, pp. 139-172, 1982.

[4] C. Linderstrom-Lang, "Gas separation in the Ranque-Hilsch vortex tube," International Journal of Heat and Mass Transfer, vol. 7, pp. 1195-1206, 1964.