🏛️國立陽明交通大學機構典藏

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Investigation of the evacuation pressure on the performance of pulsating heat pipe
(2017-07-01)
Sun, Chien-Hung
;
Tseng, Chih-Yung
;
Yang, Kai-Shing
;
Wu, Shih-Kuo
;
Wang, Chi-Chuan
This study examines the influence of evacuation pressure on the startup and overall performance of pulsating heat pipes (PHP). The outer diameter of the copper tube is 3 mm and 2 mm (double tube design) having a wall thickness of 0.3 mm and 0.2 mm, respectively. The working fluids in this study include water and HFE-7000 with filling ratios around 50%, and the evacuation pressure ranging from 0.01 Torr to atmosphere pressure. For an evacuation pressure of 0.01 Torr at a supplied power of 80 W, the thermal resistance of the PHP filling with water is 0.928 K/W while it is 1.161 K/W for HFE-7000. However, the trend is reversed and the thermal resistance for HFE-7000 is lower than water when the evacuation pressure is increased over 100 Torr. The corresponding effective thermal conductivity of waterfilling PHP reaches 51,448 W/m K in comparison with 12,692 W/m K for HFE-7000. However, the effective thermal conductivity for waterfilling PHP drops appreciably with rising evacuation pressure, and the PHP is not functional at the atmosphere pressure. Conversely, although the effective thermal conductivity for HFE-7000 PHP still drops with the rise of evacuation pressure, the HFE-7000 PHP is still in operation even without any evacuation. The gigantic difference in the startup and performance of PHP is related to the solubility of noncondensable gas amid water and HFE-7000.
A novel double pipe pulsating heat pipe design to tackle inverted heat source arrangement
(2016-08-05)
Tseng, Chih-Yung
;
Yang, Kai-Shing
;
Chien, Kuo-Hsiang
;
Wu, Shih-Kuo
;
Wang, Chi-Chuan
Traditional pulsating heat pipe with fewer turns is functional only when the heat source is placed at the bottom while the heat sink is on top. This study proposes a novel design having alternative double-pipe tube diameter with some extra open connections of these double-pipes. By introducing extra un-balanced pressure force, capillary force and gravity force, the PHP can be easily starting up even for an opposite heat source/sink arrangement while the conventional single tube design fails to start up with this opposite arrangement. The thermal resistance of double pipe PHP can be lowered to 0.0729 W/K with an effective thermal conductivity of 12,603 W/m.K when the heat source is placed on top. Yet the thermal resistance for the proposed double pipe design is only half of the single tube design. (C) 2016 Elsevier Ltd. All rights reserved.
Performance and two-phase flow pattern for micro flat heat pipes
(2014-10-01)
Yang, Kai-Shing
;
Lin, Chen-Chuan
;
Shyu, Jin-Cherng
;
Tseng, Chih-Yung
;
Wang, Chi-Chuan
In this study, thermal performance and flow visualization of a double layer flat micro vapor chamber are reported. Two micro vapor chambers having pin fin and pin fin array support structure are fabricated and tested. The micro vapor chambers are composed of silicon and glass wafers having an overall size of 35 x 40 x 1.525 mm. Test results show that both the pin fin and pin fin array vapor chambers show an appreciably lower thermal resistance as compared to the solid silicon counterpart, the thermal resistance of the pin fin vapor chamber is about 52-60% of the solid silicon whereas the corresponding thermal resistance of pin fin array is only 17-20% of the solid silicon. The thermal resistance of the pin fin vapor chamber is moderately increased subject to the increase of supplied power whereas opposite trend is encountered for the pin fin array. The phenomenon is associated with the influence of dry-out phenomenon. It is found that the pin fin array vapor chamber is still in function even for an upside-down arrangement. The thermal resistance, however, is reduced with the rise of tilt angle, and the vertical arrangement gives the lowest thermal resistance. However, the thermal resistance is considerably increased if the heat source is placed upwards, and the corresponding thermal resistance for an upside-down heat source can be threefold higher than that of the vertical arrangement. (C) 2014 Elsevier Ltd. All rights reserved.
A novel design of pulsating heat pipe with fewer turns applicable to all orientations
(2012-10-01)
Chien, Kuo-Hsiang
;
Lin, Yur-Tsai
;
Chen, Yi-Rong
;
Yang, Kai-Shing
;
Wang, Chi-Chuan
This study presents a novel pulsating heat pipe (PHP) concept that is functional even when PHP is with fewer turns and is operated horizontally. Two heat pipes were made of copper capillary tubes with an overall size of 122 mm x 57 mm x 5.5 mm is investigated, one had 16 parallel square channels having a uniform cross-section of 2 mm x 2 mm (uniform CLPHP), and the other had 16 alternative size of parallel square channels (non-uniform CLPHP; a cross-section 2 mm x 2 mm and a cross-section of 1 mm x 2 mm in alternating sequence). Test results showed that the performance of PHP rises with the inclination but the uniform channel CLPHP is not functional at horizontal configuration whereas the proposed non-uniform design is still functional even at horizontal arrangement. The thermal resistance for uniform PHP is relative insensitive to change of inclination when the inclination angle exceeds certain threshold value. (c) 2012 Elsevier Ltd. All rights reserved.

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🏛️國立陽明交通大學機構典藏

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