scholarly journals Effect of working fluids and internal diameters on thermal performance of vertical and horizontal closed-loop pulsating heat pipes with multiple heat sources

2016 ◽  
Vol 20 (1) ◽  
pp. 77-87 ◽  
Author(s):  
Niti Kammuang-Lue ◽  
Phrut Sakulchangsatjatai ◽  
Pradit Terdtoon
Keyword(s):  
Thermal Performance ◽  
Closed Loop ◽  
Capillary Tube ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Internal Diameter ◽  
Heat Sources ◽  
Pulsating Heat Pipe ◽  
Working Fluids ◽  
Fundamental Information

Some electrical applications have a number of heat sources. The closed-loop pulsating heat pipe (CLPHP) is applied to transfer heat from these devices. Since the CLPHP primarily transfers heat by means of the working fluid?s phase change in a capillary tube, the thermal performance of the CLPHP significantly depends on the working fluid type and the tube?s internal diameter. In order to provide the fundamental information for manufacturers of heat exchangers, this study on the effect of working fluids and internal diameters has been conducted. Three electrical plate heaters were installed on the CLPHP as the heat sources. The experiments were conducted by varying the working fluid to be R123, ethanol, and water, and the internal diameter to be 1.0 mm, 1.5 mm, and 2.0 mm. For each set of the same working fluid and internal diameter, the input heat fluxes of the heat sources were also made to vary within six different patterns. It can be concluded that when the latent heat of evaporation increases - in the case of vertical CLPHP - and when the dynamic viscosity of the liquid increases - in the case of horizontal CLPHP - the thermal performance decreases. Moreover, when the internal diameter increases, the thermal performance increases for both of vertical and horizontal CLPHPs.

scholarly journals Effect of Internal Diameter and Working Fluids on Thermal Performance of a Vertical Closed-Loop Oscillating Heat Pipe with Double Heat Sources

2021 ◽  
Vol 82 (2) ◽  
pp. 120-126
Author(s):  
Poomin Krisangsri ◽  
Teerasak Hudakorn ◽  
Noppong Sritrakul
Keyword(s):  
Heat Pipe ◽  
Thermal Performance ◽  
Closed Loop ◽  
Capillary Tube ◽  
Ambient Air ◽  
Internal Diameter ◽  
Heat Sources ◽  
Condenser Section ◽  
Working Fluids ◽  
Oscillating Heat Pipe

This research investigates the effects of internal diameter and working fluids on the thermal performance of a vertical closed-loop oscillating heat pipe with double heat sources (VCLOHP w/DHS). The closed-loop oscillating heat pipe (CLOHP) tested was made of a copper capillary tube with various inner diameters and working fluids. Two evaporator sections in the outer end of CLOHP were heated by a Ni-Cr alloy resistance wire heater. The heat was removed from the condenser section in the middle of CLOHP by forced convection heat transfer of ambient air blowing the section. The results showed that, for the inner diameters of 1.5 and 2.0 mm, the thermal resistance decreased when the inner diameter and the latent heat of evaporation increased.

Operating Activity Visualization and Thermal Performance Measurement of Pulsating Heat Pipe

2016 ◽  
Vol 369 ◽  
pp. 42-47 ◽  
Author(s):  
Patrik Nemec ◽  
Zuzana Kolková ◽  
Milan Malcho
Keyword(s):  
Heat Transfer ◽  
Performance Measurement ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Vapour Phase ◽  
Working Fluid ◽  
Internal Diameter ◽  
Pulsating Heat Pipe ◽  
Inner Diameter ◽  
Thermo Physical Properties

Heat pipe is well known device which is used to heat transfer phase-change of working fluid. Pulsating heat pipe (PHP) is special type of heat pipe which heat transfer by pulsating movement of working fluid. Article deals about operating activity and thermal performance measurement of this special heat pipe. Operating activity visualization of PHP was performed with PHP made from glass. The two types of PHPs were made. The first PHP has internal diameter of tube 1 mm, second PHP has internal diameter of tube 1.5 mm and both PHPs have eleven meanders. The working fluids used in PHP were water and Fluorinert FC-72. These fluids were chose for their different thermo-physical properties and the visualization observe formation of liquid and vapour phase working fluid during filling process and working operation.Next, the article describes thermal performance measurement of PHP depending on working fluid amount and heat source temperature. Measurement was performed with PHP made from copper tube with inner diameter 1.5 mm curved to the twenty one meanders and filled with water. The results give us image about formation and distribution of working fluid in pulsating heat pipe and about influence of working fluid amount on the heat transfer ability of pulsating heat pipe.

Effect of Inclination Angle on the Closed Loop Pulsating Heat Pipe Thermal Performance

2013 ◽  
Author(s):  
Pramod R. Pachghare ◽  
Ashish M. Mahalle
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Inclination Angle ◽  
Heat Input ◽  
Closed Loop ◽  
Pulsating Heat Pipe ◽  
Working Fluids ◽  
Inclination Angles ◽  
R 134A

The closed loop pulsating heat pipe (CLPHP) is a passive two-phase heat transfer device, patented by Akachi (1990). Due to its excellent features, PHP has been considered as one of the promising technologies for electronic cooling, heat exchanger, etc. This paper presents an experimental study shows the effect of inclination angle on the thermal performance of CLPHP, which consist of 10 turns of copper tubes having inner and outer diameter 2 mm and 3.6 mm respectively. The equal lengths of evaporator, condenser and adiabatic sections are 50 mm each. Different working fluids are used as R-134a, Methanol and Water. For all experimentations, an optimum filling ratio was maintained 50% by volume. The thermal performance have been investigated with different inclination angles (viz. 0°, 20°, 40°, 60° and 90°) at various heat input from 5 to 50W in the steps of 5W. The thermal resistance (which is inversely proportional to thermal performance) of CLPHP at various heat input are plotted for different working fluids. The result shows that, the thermal resistance decreases as heat input increases. But at low heat input i.e. upto 25W, the thermal resistance decreases rapidly and the PHP performance is more sensitive to the inclination angle whereas high heat input i.e. above 25W, the thermal resistance decreases smoothly and less independent to the inclination angle. In all inclination angles, vertical bottom heat position (at 90°) of CLPHP gives best thermal performance due to presence of gravity force. At all inclination angles, the working fluid R-134a show best thermal performance followed by methanol and water.

Experimental Investigation and Performance Evaluation of a Multi Turn Closed Loop Pulsating Heat Pipe

2014 ◽  
Vol 592-594 ◽  
pp. 1554-1558 ◽  
Author(s):  
N. Narendra Babu ◽  
Rudra Naik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Closed Loop ◽  
Experimental Result ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Working Fluids

Pulsating heat pipe (PHP) is a passive heat transfer device, which transfers heat from one region to another with exceptional heat transfer capacity. It utilizes the latent heat of vaporization of the working fluid as well as the sensible heat. As a result, the effective thermal conductivity is higher than that of the conductors. An experimental study on three turn closed loop pulsating heat pipe with three different working fluids viz., Acetone, Methanol, Heptane and distilled water were employed. The PHP is made up of brass material with an inner diameter of 1.95mm, with a total length of 1150 mm for different fill ratios (FR) was employed .The PHP is tested for the thermal resistance and the heat transfer coefficient. The experimental result strongly demonstrates that acetone is a better working fluid among the working fluids considered in terms of higher heat transfer coefficient and lower thermal resistance.

scholarly journals Nonlinear Analysis of Chaotic Flow in a Three-Dimensional Closed-Loop Pulsating Heat Pipe

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
S. M. Pouryoussefi ◽  
Yuwen Zhang
Keyword(s):  
Lyapunov Exponent ◽  
Heat Pipe ◽  
Closed Loop ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Periodic Behavior ◽  
Working Fluids ◽  
Chaotic Flow ◽  
Temperature Oscillations

Numerical simulation has been conducted for the chaotic flow in a 3D closed-loop pulsating heat pipe (PHP). Heat flux and constant temperature boundary conditions were applied for evaporator and condenser sections, respectively. Water and ethanol were used as working fluids. Volume of fluid (VOF) method has been employed for two-phase flow simulation. Spectral analysis of temperature time series was carried out using power spectrum density (PSD) method. Existence of dominant peak in PSD diagram indicated periodic or quasi-periodic behavior in temperature oscillations at particular frequencies. Correlation dimension values for ethanol as working fluid were found to be higher than that for water under the same operating conditions. Similar range of Lyapunov exponent values for the PHP with water and ethanol as working fluids indicated strong dependency of Lyapunov exponent on the structure and dimensions of the PHP. An O-ring structure pattern was obtained for reconstructed 3D attractor at periodic or quasi-periodic behavior of temperature oscillations. Minimum thermal resistance of 0.85 °C/W and 0.88 °C/W were obtained for PHP with water and ethanol, respectively. Simulation results showed good agreement with the experimental results from other work under the same operating conditions.

scholarly journals Numerical Study on the Effects of using Nanofluids in Pulsating Heat Pipe

2018 ◽  
Vol 7 (4.35) ◽  
pp. 204
Author(s):  
M. Zufar ◽  
P. Gunnasegaran ◽  
Ng K. Ching
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Working Fluids ◽  
Resistance Value

Pulsating Heat Pipe (PHP) is the next generation heat pipe that has a prospect in improving the heat transfer performance. The type of working fluid use in the PHP has a direct influence on the thermal performance. Incorporating nanofluid in PHP may greatly increase its thermal performance as compared to using base fluid (water). The current work focuses on the simulations of 2-dimensional flows in PHP using working fluids such as diamond, silver (Ag), silica oxide (SiO2) nanofluids and water. Constant heat flux and filling ratio of 50% were used throughout the study. From the results, it was found out that diamond nanofluid has the lowest thermal resistance value as compared to other working fluids. The effect of the number of PHP turns was studied and it was discovered that higher number of turns would produce lower thermal resistance value.

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