Performance Of Closed Loop Pulsating Heat Pipe Research Articles

Investigation of wettability on performance of pulsating heat pipe

A three-dimensional closed-loop pulsating heat pipe (CLPHP), with different wettability and charged with deionized water is numerically investigated in present work. The thermal performance and bubble dynamics of CLPHP are obtained under the condition of various input heat loads. It's found that the performance of CLPHP is affected by both surface wettability and input heat load. Under lower input heat load, CLPHP with hydrophobic surface (including superhydrophobic surface) has lower thermal resistance than that with hydrophilic surface. Conversely, CLPHP with hydrophilic surface starts up earlier, and has better thermal performance under higher input heat load. Specially, compared with the CLPHP with superhydrophobic surface, the thermal resistance of CLPHP with superhydrophilic reduces by 10.8% under the input heat load of 20 W. Moreover, the reversal of flow direction is observed in CLPHP with hydrophobic surface, while the stable directional circulation is always maintained in CLPHP with hydrophilic surface. The results indicate that the difference between advancing and receding angles (dynamic contact angle hysteresis) leads to various capillary resistance. Furthermore, due to lower flow resistance and the effect of liquid film, CLPHP with hydrophilic surface can effectively raise the dry-out input heat load.

Investigation on the performance of closed-loop pulsating heat pipe with surfactant

A three-dimensional closed-loop pulsating heat pipe (CLPHP) charged with deionized water and surfactant is numerically investigated in present work. The surfactant used in present work is hexadecyl trimethyl ammonium chloride (CTAC). The start-up performance and heat transfer characteristics of CLPHP with deionized water and surfactant are compared by changing the initial pressure (0.1 MPa, 0.07 MPa, 0.05 MPa) and input heat load (10 W, 20 W, 30 W, 40 W). It’s found that the performance of CLPHP is affected by the initial pressure, surfactant concentration and input heat load jointly. Under the condition of high initial pressure, the performance of CLPHP with surfactant is not as good as that with deionized water. However, under the condition of low initial pressure, especially at higher input heat load, the superiority of the surfactant begins to appear. Compared with the CLPHP with deionized water, the thermal resistance could be decreased by 4.78% when the initial pressure, the input heat load and the surfactant concentration is 0.05 MPa, 40 W and 50 ppm, respectively. It is also found that the CLPHP with 2000 ppm CTAC has a much lower heat transfer performance than that with deionized water under any conditions. Finally, surfactant can improve the wettability of the CLPHP wall, reduce the contact angle, and absolutely prevent the occurrence of “dry-out”.

Effect of Inclination Angles on Heat Transfer Characteristics of a Closed Loop Pulsating Heat Pipe (CLPHP)

Abstract At present Closed Loop Pulsating Heat Pipe (CLPHP) is a novel cooling strategy for successful thermal management though it is a complex heat transfer device having a strong thermo-hydrodynamic coupling to govern the thermal performance. This research is to study the effect of inclination angle and working fluid on the heat transfer characteristics and performance of CLPHP. The performance characterization has been done using two different working fluids of water and ethanol with inclination angle of 0˚ (vertical), 30˚, 45˚, 60˚, 75˚ and 90˚ (horizontal). The experiment is conducted on a CLPHP made of 148 cm long copper capillary tube of 3.0 mm outer diameter and 2.0 mm inner diameter creating a total of 13 turns. The total length of evaporator section is 39.5 cm and condenser section is 31.5 cm; while the rest is assumed to be adiabatic. The evaporator section is heated by electrical heat input, while the condenser section is cooled by atmospheric air flow. Since a PHP is recognized as a two phase heat transfer device, for comparative studies it is operated as a double-phase system by filling it 70% with the working fluid. The comparative study results in a better understanding of the underlying physics of the PHP operation. The experimental results indicate a strong influence of gravity and thermo physical properties of the working fluid on the performance of the CLPHP. The results demonstrate the effect of the input heat flux, inclination angle and physiochemical properties of the working fluid on the thermal performance of the device.

Experimental Investigations on Thermal Performance of a Multi-Turn Closed Loop Pulsating Heat Pipe

Closed loop pulsating heat pipe (CLPHP) is a relatively new two-phase passive heat transfer device to suit present requirement of high heat flux dissipation in modern electronic components. The operating mechanism of CLPHP is not well understood and the present state of the technology cannot predict required design parameters for a given task. The aim of research work presented in this paper is to better understand thermal performance of CLPHP. A series of experimental investigation were conducted on a multi-turn CLPHP made of copper capillary tube of 2-mm inner diameter. Two kinds of working fluids viz. ethanol and acetone were employed. The influence characterization has been studied for the variation of heat input and filling ratio (FR) of the tested CLPHP. Thermal performance of the CLPHP is evaluated by heat transfer and thermal resistance. The results strongly demonstrate the effect of heat input and FR of the working fluid on thermal performance of the device.