Development of the Loop Heat Pipe (LHP)

2008 ◽  
Author(s):  
K. Tanaka
Keyword(s):  
Heat Transfer ◽  
Physical Development ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Transfer Capability ◽  
Heat Transfer Capability ◽  
Basic Equations ◽  
Test Result

First, I describe the basic equations that resolve the physical development of the LHP and how to estimate the maximum heat transfer capability of the LHP. Second, I describe the outline of experimental manufacture of the LHP. This LHP is made from copper. The evaporator is φ19×95mm, the vapor tube is φ5×300mm, the condenser is φ3.5×600mm and the liquid tube is φ3.5×300mm. The wick is made from the sintering cupper. The working fluid is methanol. Finally, I briefly describe the test result of heat transfer capability of this LHP.

Thermal Performance of the Mini-Loop Heat Pipe (LHP)

2009 ◽  
Author(s):  
K. Tanaka ◽  
M. Katsuta ◽  
Y. Ohuchi ◽  
K. Saitho
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Physical Development ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Transfer Capability ◽  
Heat Transfer Capability ◽  
Basic Equations ◽  
Test Result

In this paper, we describe the outline of experimental manufacture of the LHP. This LHP is made of a copper. The evaporator is φ19×95mm, the vapor tube is φ5×300mm, the condenser is φ3.5×600mm and the liquid tube is φ 3.5×300mm. The wick is made of the sintering copper. The working fluid is methanol. Second, we describe the test result of heat transfer capability of this LHP. Finally, I describe the basic equations that resolve the physical development of the LHP and how to estimate the each temperatures of the LHP.

Optimization of Wettability Gradient for Enhancement of Thermal Performance of Micro Heat Pipes

2018 ◽  
Author(s):  
Manjinder Singh ◽  
Naresh Varma Datla ◽  
Supreet Singh Bahga ◽  
Sasidhar Kondaraju
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Variable Mass ◽  
Working Fluid ◽  
Maximum Heat ◽  
Continuous Increase ◽  
Maximum Heat Transfer ◽  
Integration Density ◽  
Heat Transfer Capacity ◽  
Micro Heat Pipes

Continuous increase in the integration density of microelectronic units necessitates the use of MHPs with enhanced thermal performance. Recently, the use of wettability gradients have been shown to enhance the heat transfer capacity of MHPs. In this paper, we present an optimization of axial wettability gradient to maximize the heat transfer capacity of the MHP. We use an experimentally validated mathematical model and interior point method to optimize the wettability gradient. For our analysis, we consider two cases wherein (i) the mass of working fluid is constrained, (ii) mass of working fluid is a design variable. Compared to MHP with uniform high wettability and filled with a fixed mass of working fluid, optimization of the wettability gradient leads to 65% enhancement in heat transfer capacity. Similar comparisons for MHP filled with variable mass of working fluid shows more than 90% increase in the maximum heat transfer capacity due to optimization of wettability gradient.

Numerical Analysis of Natural Convective Heat Transfer over a Vertical Cylinder Using External Fins

2015 ◽  
Vol 813-814 ◽  
pp. 707-712
Author(s):  
Anwesha Panigrahi ◽  
D.P. Mishra ◽  
Deepak Kumar
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Vertical Cylinder ◽  
Working Fluid ◽  
Natural Convection Heat Transfer ◽  
Maximum Heat ◽  
Optimum Parameters ◽  
Maximum Heat Transfer

The present numerical study deals with the natural convection heat transfer on the surface of a vertical cylinder with external longitudinal fins. The aim of the study was to determine the effects of geometric parameters like fin height, fin number and fin shape on the heat transfer and thus obtain the optimum parameters that will maximize the rate of heat transfer have been discussed. The numerical investigation consists of an aluminium cylinder of length 1m and diameter 0.07m with air as the working fluid. It has been seen from the numerical investigation that the heat transfer increases with fin height. It is also observed that there exists optimum fin number for maximum heat transfer. Keeping the fin number, fin height and volume fixed, it was found that the heat transfer is maximum for rectangular shaped fin.

Metallic Nanoemulsion for Microchannel Heat-Sink

2016 ◽  
Author(s):  
Yoshikazu Hayashi ◽  
Gordon Yip ◽  
Yoon Jo Kim ◽  
Jong-Hoon Kim
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Specific Heat ◽  
Heat Sink ◽  
Effective Medium Theory ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Viscosity Change ◽  
Transfer Capability ◽  
Heat Transfer Capability

Galinstan is a eutectic alloy of gallium, indium, and tin, of which thermal conductivity is ∼27 times higher than that of water, while the dynamic viscosity is only twice. Thus, heat transfer coefficient can be remarkably enhanced with a small penalty of pumping power. However, the direct use of galinstan can suffer from practical issues such as oxidation and low specific heat. Therefore, galinstan is mixed with a coolant as an additive to form a colloidal fluid; i.e., dispersion of nanoscale galinstan droplets in a coolant to enhance the thermal conductivity. It is expected that this “metallic nanoemulsion” can contribute to substantial improvement in heat transfer capability. Also, the common issues with colloidal fluids such as rapid sedimentation, erosion, and clogging, can be minimized by the “fluidity” of the liquid metal. It was shown that ultrasonic emulsification can yield few hundreds scale nanodroplets. However, the long exposure of galinstan to oxygen in water inevitably results in severe oxidation of the droplets. Theoretical analysis was also conducted to examine the feasibility of the metallic nanoemulsion as a microchannel heat-sink working fluid. Effective medium theory was used to evaluate the thermal conductivity of the mixture. The viscosity change was also predicted considering both the viscosity of dispersed phase and interaction between the droplets. Under one-dimensional laminar flow assumption, mass, momentum, and energy conservation equations were analytically solved. The effect of high thermal conductivity of galinstan was evident; the convection heat transfer capability was greatly enhanced, while the viscosity increase due to the nanoscale blending and the low specific heat of galinstan counteracts and reduce the flow rate and thus increase the caloric thermal resistance.

Numerical Analysis of Water-Based Nanofluid Coolant for Small Modular Reactor

2011 ◽  
Author(s):  
Mohammad Nazififard ◽  
Mohammadreza Nematollahi ◽  
Kune Y. Suh
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Pure Water ◽  
Working Fluid ◽  
Particle Volume ◽  
Maximum Heat ◽  
Small Modular Reactors ◽  
Maximum Heat Transfer ◽  
Small Modular Reactor ◽  
Flow Features

This paper is aimed at understanding thermohydrodynamic and neutronic characteristics of nanofluids for prospective application to water cooled small modular reactors. Numerical analysis is performed to investigate turbulent convective heat transfer and flow features of Al2O3 nanofluids as working fluid. The Al2O3-water nanofluids of 1%, 4% and 6% by volume have been employed for the numerical simulation resorting to the homogenous fluid assumptions with modified thermophysical properties. Results indicate that the heat transfer increases with nanoparticle volume concentrations by 4.2%–31% as compared against that for pure water. The maximum heat transfer increase at the center of a subchannel formed by fuel rods is 31.29% for the particle volume concentration of 6% corresponding to the Reynolds number of 65,000. It consequently appears promising enough to use nanofluids in small modular reactors. Neutronic and thermohydrodynamic investigations are further needed to streamline the nanoparticles and to optimize their concentration during the normal and abnormal operations.

A Review on Nanofluid Heat Pipe

2014 ◽  
Author(s):  
Maryam Shafahi ◽  
Kevin Anderson ◽  
Ali Borna ◽  
Michael Lee ◽  
Alex Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Working Fluid ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Medical Instruments ◽  
Thermo Physical Properties

This paper reviews the improvement in the heat pipe’s performance using nanofluid as the working fluid. The use of nanofluid enhances heat transfer in the heat pipe due to its improved thermo-physical properties, such as a higher thermal conductivity. Nanofluids proved to be the innovative approach to a variety of applications, such as electronics, medical instruments, and heat exchangers. The influence of different nanoparticles on heat pipe’s performance has been studied. Utilizing nanofluid as the working fluid leads to a significant reduction in heat pipe thermal resistance, an increase in maximum heat transfer, and an improvement of heat pipe thermal performance.

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