Gravity-Assisted Heat Pipe With Strong Marangoni Fluid for Waste Heat Management of Single and Dual-Junction Solar Cells

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Kenneth M. Armijo ◽  
Van P. Carey
Keyword(s):  
Heat Flux ◽  
Solar Cells ◽  
Heat Pipe ◽  
Waste Heat ◽  
Working Fluid ◽  
Water Mixture ◽  
Heat Management ◽  
Strong Concentration ◽  
Electrical Efficiency ◽  
Pipe System

This study investigates the cooling of single and multijunction solar cells with an inclined, gravity-assisted heat pipe, containing a 0.05 M 2-propanol/water mixture that exhibits strong concentration Marangoni effects. Heat pipe solar collector system thermal behavior was investigated theoretically and semi-empirically through experimentation of varying input heat loads from attached strip-heaters to simulate waste heat generation of single-junction monocrystalline silicon (Si), and dual-junction GaInP/GaAs photovoltaic (PV) solar cells. Several liquid charge ratios were investigated to determine an optimal working fluid volume that reduces the evaporator superheat while enhancing the vaporization transport heat flux. Results showed that a 45% liquid charge, with a critical heat flux of 114.8 W/cm2, was capable of achieving the lowest superheat levels, with a system inclination of 37 deg. Solar cell semiconductor theory was used to evaluate the effects of increasing temperature and solar concentration on cell performance. Results showed that a combined PV/heat pipe system had a 1.7% higher electrical efficiency, with a concentration ratio 132 suns higher than the stand-alone system. The dual-junction system also exhibited enhanced performance at elevated system temperatures with a 2.1% greater electrical efficiency, at an operational concentration level 560 suns higher than a stand-alone system.

An Experimental Study of Heat Pipe Performance Using Binary Mixture Fluids That Exhibit Strong Concentration Marangoni Effects

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Kenneth M. Armijo ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Pipe ◽  
Pure Water ◽  
Working Fluid ◽  
Strong Concentration ◽  
Alcohol Mixtures ◽  
Marangoni Effects ◽  
Water Alcohol

This paper summarizes the results of an experimental investigation of the performance characteristics of a gravity/capillary driven heat pipe using water/alcohol mixtures as a working fluid. This investigation specifically explored the use of water/alcohol mixtures that exhibit strong concentration-based Marangoni effects. Experiments to determine heat pipe performance were conducted for pure water and water/alcohol solutions with increasing concentrations of alcohol. Initial tests with pure water determined the optimal working fluid charge for the heat pipe; subsequent performance tests over a wide range of heat input levels were then conducted for each working fluid at this optimum value. The results indicate that some mixtures can significantly enhance the heat transfer coefficient and heat flux capability of the heat pipe evaporator. For the best mixture tested, the maximum evaporator heat flux carried by the coolant without dryout was found to be 52% higher than the value for the same heat pipe using pure water as a coolant under comparable conditions. Peak evaporator heat flux values above 100 W/cm2 were achieved with some mixtures. Evaporator and condenser heat transfer coefficient data are presented, and the trends are examined in the context of the expected effect of the Marangoni mechanisms on heat transfer.

An Experimental Study of Heat Pipe Performance Using Binary Mixture Fluids That Exhibit Strong Concentration Marangoni Effects

2010 ◽  
Author(s):  
Kenneth M. Armijo ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Pipe ◽  
Pure Water ◽  
Working Fluid ◽  
Strong Concentration ◽  
Alcohol Mixtures ◽  
Marangoni Effects ◽  
Water Alcohol

This paper summarizes the results of an experimental investigation of the performance characteristics of a gravity/capillary driven heat pipe using water/alcohol mixtures as a working fluid. This investigation specifically explored the use of water/alcohol mixtures that exhibit strong concentration-based Marangoni effects. Experiments to determine heat pipe performance were conducted for pure water and water/alcohol solutions with increasing concentrations of alcohol. Initial tests with pure water determined the optimal working fluid charge for the heat pipe; subsequent performance tests over a wide range of heat input rates were then conducted for each working fluid at this optimum value. The results indicate that some mixtures can significantly enhance the heat transfer coefficient and heat flux capability of the heat pipe evaporator. For the best mixture tested, the maximum evaporator heat flux carried by the coolant without dryout was found to be 52% higher than the value for the same heat pipe using pure water as a coolant under comparable conditions. Peak evaporator heat fluxes above 100 W/cm2 were achieved with some mixtures. Evaporator and condenser heat transfer coefficient data are presented and the trends are examined in the context of the expected effect of the Marangoni mechanisms on heat transfer. Heat pipe design features that take maximum advantage of Marangoni effects are described and the application of these types of heat pipes to electronics cooling and heat removal from concentrating photovoltaic systems is discussed.

Novel Combined Power and Cooling Thermodynamic Cycle for Low Temperature Heat Sources, Part II: Experimental Investigation

2003 ◽  
Vol 125 (2) ◽  
pp. 223-229 ◽  
Author(s):  
Gunnar Tamm ◽  
D. Yogi Goswami
Keyword(s):  
Low Temperature ◽  
System Analysis ◽  
Waste Heat ◽  
Thermal Power ◽  
Experimental System ◽  
Thermodynamic Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Water Mixture ◽  
Theoretical Simulation

A combined thermal power and cooling cycle proposed by Goswami is under intensive investigation, both theoretically and experimentally. The proposed cycle combines the Rankine and absorption refrigeration cycles, producing refrigeration while power is the primary goal. A binary ammonia-water mixture is used as the working fluid. This cycle can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low temperature sources such as geothermal and solar energy. An experimental system was constructed to demonstrate the feasibility of the cycle and to compare the experimental results with the theoretical simulation. Results showed that the vapor generation and absorption condensation processes work experimentally, exhibiting expected trends, but with deviations from ideal and equilibrium modeling. The potential for combined turbine work and refrigeration output was evidenced in operating the system. Analysis of losses showed where improvements could be made, in preparation for further testing over a broader range of operating conditions.

scholarly journals Distribution of heat flux by working fluid in loop heat pipe

2016 ◽  
Vol 114 ◽  
pp. 02081
Author(s):  
Patrik Nemec ◽  
Milan Malcho
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Working Fluid ◽  
Loop Heat Pipe

scholarly journals The effect of operating parameters on the heat transfer in the heat pipe

2021 ◽  
Vol 2119 (1) ◽  
pp. 012088
Author(s):  
A. A. Litvintceva ◽  
N. I. Volkov ◽  
N. I. Vorogushina ◽  
V. A. Moskovskikh ◽  
V. V. Cheverda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Heat Pipes ◽  
Working Fluid ◽  
Operating Parameters ◽  
Temperature Stabilization ◽  
Ir Camera ◽  
Fluid Properties

Abstract Heat pipes are a good solution for temperature stabilization, for example, of microelectronics, because these kinds of systems are without any moving parts. Experimental research of the effect of operating parameters on the heat transfer in a cylindrical heat pipe has been conducted. The effect of the working fluid properties and the porous layer thickness on the heat flux and temperature difference in the heat pipe has been investigated. The temperature field of the heat pipe has been investigated using the IR-camera and K-type thermocouples. The data obtained by IR-camera and K-type thermocouples have been compared. It is demonstrated the power transferred from the evaporator to the condenser is a linear function of the temperature difference between them.

A Novel Combined Power and Cooling Thermodynamic Cycle for Low Temperature Heat Sources: Part II — Experimental Investigation

Solar Energy ◽  
2002 ◽  
Author(s):  
Gunmar Tamm ◽  
D. Yogi Goswami
Keyword(s):  
Low Temperature ◽  
System Analysis ◽  
Waste Heat ◽  
Thermal Power ◽  
Experimental System ◽  
Thermodynamic Cycle ◽  
Working Fluid ◽  
Water Mixture ◽  
Theoretical Simulation ◽  
Intensive Investigation

A combined thermal power and cooling cycle proposed by Goswami is under intensive investigation, both theoretically and experimentally. The proposed cycle combines the Rankine and absorption refrigeration cycles, producing refrigeration while power is the primary goal. A binary ammonia-water mixture is used as the working fluid. This cycle can be used as a bottoming cycle using waste heat from a conventional power cycle or an independent cycle using low temperature sources such as geothermal and solar energy. An experimental system was constructed to demonstrate the feasibility of the cycle and to compare the experimental results with the theoretical simulation. Results showed that the vapor generation and absorption condensation processes work experimentally, exhibiting expected trends, but with deviations from ideal and equilibrium modeling. The potential for combined turbine work and refrigeration output was evidenced in operating the system. Analysis of losses showed where improvements could be made, in preparation for further testing over a broader range of operating parameters.

Effect of Fluid Loading on the Performance of Wicked Heat Pipes

Volume 3 ◽  
2004 ◽  
Author(s):  
R. Kempers ◽  
A. Robinson ◽  
C. Ching ◽  
D. Ewing
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Working Fluid ◽  
Fluid Loading ◽  
Maximum Heat ◽  
Horizontal Orientation ◽  
Maximum Heat Flux ◽  
Dry Out

A study was performed to experimentally characterize the effect of fluid loading on the heat transport performance of wicked heat pipes. In particular, experiments were performed to characterize the performance of heat pipes with insufficient fluid to saturate the wick and excess fluid for a variety of orientations. It was found that excess working fluid in the heat pipe increased the thermal resistance of the heat pipe, but increased maximum heat flux through the pipe in a horizontal orientation. The thermal performance of the heat pipe was reduced when the amount of working fluid was less than required to saturate the wick, but the maximum heat flux through the heat pipe was significantly reduced at all orientations. It was also found in this case the performance of this heat pipe deteriorated once dry-out occurred.

Nano Heat Pipe: Nonequilibrium Molecular Dynamics Simulation

2016 ◽  
Author(s):  
Mohammad Moulod ◽  
Gisuk Hwang
Keyword(s):  
Molecular Dynamics ◽  
Heat Flux ◽  
Heat Pipe ◽  
Thermal Management ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Management Systems ◽  
Working Fluid ◽  
Maximum Heat

A heat pipe has been known as a thermal superconductor utilizing a liquid-vapor phase change, and it has drawn significant attentions for advanced thermal management systems. However, a challenge is the size limitation, i.e., the heat pipe cannot be smaller than the evaporator/condenser wick structures, typically an order of micron, and a new operating mechanism is required to meet the needs for the nanoscale thermal management systems. In this study, we design the nanoscale heat pipe employing the gas-filled nanostructure, while transferring heat via ballistic fluid-particle motions with a possible returning working fluid via surface diffusions along the nanostructure. The enhanced heat flux for the nano heat pipe is demonstrated using the nonequilibrium molecular dynamics simulations (NEMDS) for the argon gas confined by the 20 nm-long Pt nanogap with a post wall with the temperature difference between the hot and cold surfaces of 20 K. The predicted results show that the maximum heat flux through the gas-filled nanostructure (heat pipe) nearly doubles that of the nanogap without the post wall at 100 < T < 140 K. The optimal operating conditions/material selections are discussed. The results for the nanogap agree with those obtained from the kinetic theory, and provide insights into the design of advanced thermal management systems.

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