Understanding the self-sustained oscillating two-phase flow motion in a closed loop pulsating heat pipe

A pulsating heat pipe (PHP) is a passive device with a good heat transport capability compared to other heat pipes. This paper describes an experimental investigation of a PHP with a serpentine channel fabricated by using a 3-D printer. The configuration of the flow channels in the PHP was close to that of commercially available PHPs made entirely of aluminum. To improve the heat transport capability and enable flow visualization, an aluminum plate was used on one side as the heat-transfer surface, on which transparent flow channels were fabricated by a 3-D printer and a polycarbonate filament. The interface between the aluminum plate and polycarbonate flow channel was cemented with a heat-resistant glue to ensure long term sealing. HFE-7000 was used as a working fluid. Oscillating two-phase flow in the PHP was observed with a high-speed digital video camera and transient surface temperatures at evaporator, insulator and condenser sections were measured by fine diameter thermocouples. The two-phase flow and thermal characteristics of the PHP at different heater power levels are presented.

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Visual study on two-phase flow in a horizontal closed-loop oscillating heat pipe

Thermal Science ◽

10.2298/tsci170514232c ◽

2019 ◽

Vol 23 (2 Part B) ◽

pp. 1055-1065

Author(s):

Piyanun Charoensawan ◽

Pradit Terdtoon

Keyword(s):

Heat Pipe ◽

Closed Loop ◽

Two Phase Flow ◽

Phase Flow ◽

Two Phase ◽

Oscillating Heat Pipe ◽

Visual Study

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Flow and heat transfer in a closed loop thermosyphon. Part I – theoretical simulation

Journal of Energy in Southern Africa ◽

10.17159/2413-3051/2007/v18i4a3389 ◽

2007 ◽

Vol 18 (4) ◽

pp. 32-40 ◽

Cited By ~ 8

Author(s):

R.T. Dobson ◽

J.C. Ruppersberg

Keyword(s):

Heat Transfer ◽

Heat Pipe ◽

Closed Loop ◽

Two Phase Flow ◽

Working Fluid ◽

Phase Flow ◽

Two Phase ◽

Operating Modes ◽

Flow And Heat Transfer ◽

Control Volumes

A natural circulation, closed loop thermosyphon can transfer heat over relatively large distances without any moving parts such as pumps and active controls. Such loops are thus considered suitable for nuclear reactor cooling applications where safety and high reliability are of paramount importance. A theoretical basis from which to predict the flow and heat transfer performance of such a loop is present-ed. A literature survey of the background theory is undertaken and the theoretical equations describing the single and two-phase flow as well as heat trans-fer behaviour are given. The major assumptions made in deriving these equations are that the work-ing fluid flow is quasi-static and that its single, two-phase flow and heat transfer behaviour may be cap-tured by dividing the working fluid in the loop into a number of one dimensional control volumes and then applying the equations of change to each of these control volumes. Theoretical simulations are conducted for single phase, single and two-phase and heat pipe operating modes, and a sensitivity analysis of the various variables is undertaken. It is seen that the theoretical results capture the single and two-phase flow operating modes well for a loop that includes an expansion tank, but not for the heat pipe operating mode. It is concluded that the theo-retical model may be used to study transient and dynamic non-linear effects for single and two-phase modes of operation. To more accurately predict the heat transfer rate of the loop however, loop specific heat transfer coefficients need to be determined experimentally and incorporated into the theoretical model.

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Performance of a Pulsating Heat Pipe Fabricated With a 3-D Printer

Volume 2: Heat Transfer Equipment; Heat Transfer in Multiphase Systems; Heat Transfer Under Extreme Conditions; Nanoscale Transport Phenomena; Theory and Fundamental Research in Heat Transfer; Thermophysical Properties; Transport Phenomena in Materials Processing and Manufacturing ◽

10.1115/ht2017-4816 ◽

2017 ◽

Author(s):

Yasushi Koito ◽

Masahiro Kawaji

Keyword(s):

Heat Pipe ◽

Two Phase Flow ◽

Imaging System ◽

Cooling Water ◽

Working Fluid ◽

Transient Temperature ◽

Phase Flow ◽

Pulsating Heat Pipe ◽

Two Phase ◽

Condenser Section

A pulsating heat pipe (PHP) was fabricated by a 3-D printer, and its heat transfer characteristics were investigated by experiments. A graphene-laden PLA (PolyLactic Acid) filament was used as a 3-D printing material. Ten square channels having a cross section of 1.5 mm × 1.5 mm and a length of 80 mm were made inside the PHP and the ends of channels were connected. Since the graphene-laden PLA filament allows electric currents to pass through, the 3-D printed PHP was electroplated by copper to maintain its airtightness. Ethanol was used as the working fluid. The filling ratio of the working fluid was 50 %. In experiments, an evaporator section of the PHP was heated by a heater and a condenser section was cooled using a water-cooling jacket. The heater power was changed from 2.0 W to 8.0 W while the cooling water temperature and its flow rate were kept at 4.0 °C and 0.25 LPM, respectively. The transient temperature distribution of the PHP was measured by thermocouples. Moreover, because the graphene-laden PLA is nontransparent, an X-ray imaging system was also employed to observe the two-phase flow phenomena occurring in channels of the PHP. From the experimental results, the continuous heat transport from the evaporator to the condenser section of the PHP was confirmed with vapor-liquid two-phase flow characteristics observed inside the channels.

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