Flow Patterns and Heat Transfer Characteristic of Two-Phase Closed Rectangular Cross Sectional Area Thermosyphon

Abstract

This study investigates types of two-phase flow patterns that affect the heat transfer rate. Occurring within two-phase closed rectangular cross sectional area thermosyphon (RTPCT) and circle cross sectional area thermosyphon (TPCT) made of heat-resistant glass tube inner diameters of 7 and 25.2 mm. Aspect ratio were 5 and 20, the inclination angles were 0, 80 and 90°, the evaporator temperature were 50, 70 and 90 °C, the filling ration was 50% with respect to evaporator section and temperature water of the condenser section was 20 °C. From the test results, the RTPCT inner diameter 25.2 mm, the inclination angle was 90° and using water as working fluids.There are four types of flow pattern including bubble flow pattern, slug flow pattern, churn flow pattern and annular flow pattern for case aspect ratio was 20. By churn flow pattern and the annular flow pattern affect the heat transfer rate. Also found bubble flow pattern, slug flow pattern and churn flow pattern for case aspect ratio was 5. By slug flow pattern and churn flow pattern affects the heat transfer rate. And the heat flux obtained from the RTPCT within the diameter of 25.2 mm, aspect ratio was 5 is the heat transfer rate per unit area is 2.60 kW/m2 at the evaporation temperature of 90 °C.

When considering the TPCT diameters of 7 and 25.2 mm. Aspect ratio was 5, the inclination angles were 0, 80 and 90°, using silver nanoparticles and adding oleic acid to reduce surface tension as working fluids. From the test results, the TPCT inner diameter 7 mm, the inclination angles were 80 and 90°. There are four types of flow pattern including bubble flow pattern, slug flow pattern, churn flow pattern and annular flow pattern. By churn flow pattern and the annular flow pattern affects the heat transfer rate of the TPCT with inner diameter of 7 mm the inclination angles were 80 and 90° respectively. In the TPCT test, the inner diameter of 25.2 mm at the inclination angle was 80°. There are four types of flow patterns, including the bubble flow pattern, slug flow pattern, churn flow pattern and stratified flow pattern respectively. By the churn flow pattern and stratified flow patterns affects the heat transfer rate for this test case. And the TPCT inner diameter of 25.2 mm at the inclination angle was 90°. There are four flow patterns, including the bubble pattern, slug flow pattern, churn flow pattern and the vortex flow pattern. The vertex flow pattern is a flow pattern that occurs and when flowing, the temperature in the evaporator section starts to rise from 70 to 90 °C. By the churn flow pattern and the vortex flow pattern affects the heat transfer rate for this test case. Also found the heat flux obtained from TPCT both inner diameter of 7 and 25.2 mm showed the highest heat transfer rate per unit area at evaporation temperature of 90 °C, the inclination angle was 80°, ie 32.33 and 5.25 kW/m2, respectively.

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