Steady-State Network Thermofluid Models of Loop Heat Pipes

2007 ◽  
Author(s):  
Nima Atabaki ◽  
Nirmalakanth Jesuthasan ◽  
B. Rabi Baliga
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Steady State ◽  
Phase Region ◽  
Vapor Transport ◽  
Two Phase ◽  
Liquid Transport ◽  
One Dimensional ◽  
Flow And Heat Transfer ◽  
Transport Line

A loop heat pipe (LHP) with one evaporator, a vapor-transport line, a single condenser, a liquid-transport line, and a compensation chamber is considered. The evaporator is an internally grooved circular pipe, with an annular wick installed on its inner surface. The wick is made of sintered powder metal. The condenser is a horizontal tube that is fitted with excellent thermal contact inside a metallic sleeve that is immersed in a constant-temperature bath maintained at a fixed sink temperature. Two different network thermofluid models of this LHP operating under steady-state conditions are presented. In the first (basic) model, quasi one-dimensional mathematical models of the fluid flow and heat transfer in each of the elements of the LHP are used; the pressure drop in the two-phase region of the condenser is ignored; and a relatively simple correlation is used to model the heat transfer in the two-phase region of the condenser. In the second (segmented) model, quasi one-dimensional control volumes or cells are used for the simulation of fluid flow and heat transfer in the vapor-transport line, the condenser, and the liquid-transport line, in order to better account for the variation of fluid properties and the quality (in two-phase regions); and the pressure drops in the two-phase regions are accounted for. The working fluid considered in this investigation is ammonia, but the proposed models can be used with any suitable fluid. Results pertaining to the LHP performance for a range of operating conditions are presented. Some of these results are compared to corresponding results of an earlier experimental investigation in the literature: good agreement is obtained with both models.

Steady-State Segmented Thermofluid Network Simulations of a Loop Heat Pipe Operating With Four Different Working Fluids

2009 ◽  
Author(s):  
Nirmalakanth Jesuthasan ◽  
B. Rabi Baliga
Keyword(s):  
Stainless Steel ◽  
Steady State ◽  
Steel Plate ◽  
Rectangular Cross Section ◽  
Vapor Transport ◽  
Loop Heat Pipe ◽  
Stainless Steel Plate ◽  
Liquid Transport ◽  
One Dimensional ◽  
Transport Line

A segmented network thermofluid model for the simulation of a loop heat pipe (LHP) operating under steady-state conditions is presented, with special emphasis on quasi one-dimensional models and semi-empirical correlations for the related multiphase phenomena. Attention is focused on an LHP with one flat-evaporator, a vapor transport line, one condenser, a liquid transport line, and a compensation chamber. The evaporator consists of the following parts: An upper piece, machined out of a stainless steel plate, with vapor-transport grooves of rectangular cross section on its bottom face; a lower piece, also machined out of a stainless steel plate, with a cavity of rectangular cross section that serves as the liquid pool in the evaporator during the operation of the LHP; and a rectangular wick sandwiched between the upper and lower pieces. The wick is a sintered powder metal plate made of stainless steel. The condenser is a horizontal tube that is fitted with excellent thermal contact inside a large high thermal conductivity metallic sleeve that is maintained at a fixed sink temperature. The vapor-transport line, the condenser, and the liquid-transport line are divided into control volumes or cells. Quasi one-dimensional models are used to impose balances of mass, momentum, and energy on each of these cells. The variation of fluid thermophysical properties and multiphase phenomena, such as the change in quality and pressure drops in the two-phase regions, are suitably accounted for in this model. Four different working fluids, ammonia, distilled water, ethanol and isopropanol, are considered, and the results obtained for a representative range of steady-state operating conditions of the LHP are presented and comparatively discussed.

scholarly journals The Influence of Different Types of Nanofluid on Thermal and Fluid Flow Performance of Liquid Cold Plate

2018 ◽  
Vol 7 (4.35) ◽  
pp. 148 ◽  
Author(s):  
Nur Irmawati Om ◽  
Rozli Zulkifli ◽  
P. Gunnasegaran
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Steady State ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Cold Plate ◽  
Governing Equations ◽  
Flow And Heat Transfer ◽  
Different Types ◽  
Volume Method

The influence of utilizing different nanofluids types on the liquid cold plate (LCP) is numerically investigated. The thermal and fluid flow performance of LCP is examined by using pure ethylene glycol (EG), Al2O3-EG and CuO-EG. The volume fraction of the nanoparticle for both nanofluid is 2%. The finite volume method (FVM) has been used to solved 3-D steady state, laminar flow and heat transfer governing equations. The presented results indicate that Al2O3-EG able to provide the lowest surface temperature of the heater block followed by CuO-EG and EG, respectively. It is also found that the pressure drop and friction factor are higher for Al2O3-EG and CuO-EG compared to the pure EG.

Verification of Finite Volume Computations on Steady-State Fluid Flow and Heat Transfer

2001 ◽  
Vol 124 (1) ◽  
pp. 11-21 ◽  
Author(s):  
J. Cadafalch ◽  
C. D. Pe´rez-Segarra ◽  
R. Co`nsul ◽  
A. Oliva
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Steady State ◽  
Finite Volume ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Independent Solution ◽  
Post Processing ◽  
Square Duct ◽  
Flow And Heat Transfer

This work presents a post-processing tool for the verification of steady-state fluid flow and heat transfer finite volume computations. It is based both on the generalized Richardson extrapolation and the Grid Convergence Index GCI. The observed order of accuracy and a error band where the grid independent solution is expected to be contained are estimated. The results corresponding to the following two and three-dimensional steady-state simulations are post-processed: a flow inside a cavity with moving top wall, an axisymmetric turbulent flow through a compressor valve, a premixed methane/air laminar flat flame on a perforated burner, and the heat transfer from an isothermal cylinder enclosed by a square duct. Discussion is carried out about the certainty of the estimators obtained with the post-processing procedure. They have been shown to be useful parameters in order to assess credibility and quality to the reported numerical solutions.

Numerical Simulation of Two-Phase Fluid Flow and Heat Transfer With or Without Phase Change Using a Volume-of-Fluid Model

2004 ◽  
Author(s):  
Lieke Wang ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Phase Change ◽  
Fluid Model ◽  
Piecewise Linear ◽  
Volume Of Fluid ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Vof Model ◽  
Phase Fluid

Numerical simulations of two-phase fluid flow and heat transfer with or without phase change have been carried out. The Volume-of-Fluid (VOF) model was used in the simulations, and a procedure for considering the phase change process was developed. The Piecewise Linear Interface Calculation (PLIC) method is employed for the interface reconstruction, to keep the sharp interface. The coupling between pressure and velocity is treated by the SIMPLEC algorithm. The surface tension is modeled by the Continuum Surface Force (CSF) model. An in-house code has been developed, and two examples are presented in this paper, i.e., dam-break case and a falling water droplet in a steam bath. The calculation results are compared with corresponding experimental data, and good agreement is obtained.

Numerical Simulation of Operating Performance of Heat Exchangers in a Residential Split Air-Conditioner

2011 ◽  
Vol 250-253 ◽  
pp. 3913-3918 ◽  
Author(s):  
Shun Yu Su ◽  
Tian Tian ◽  
Jian Chen
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchangers ◽  
Great Influence ◽  
Working Fluid ◽  
Air Conditioner ◽  
Two Phase ◽  
Air Conditioning System ◽  
Flow And Heat Transfer ◽  
Phase Fluid

The mechanism of fluid flow and heat transfer in the heat exchangers was investigated in this paper. Using R22 as the working fluid, the steady distributed parameter models of condenser and evaporator in a residential split air-conditioner were established based on thermophysical laws such as mass, momentum and energy conservation equations. The regions of two-phase fluid and superheated gas in evaporator and the regions of superheated gas, two-phase fluid and subcooled liquid in condenser were respectively simulated under designed conditions of air-conditioning system. Based on the calculated results, the flow and heat transfer performances of heat exchangers were analyzed. The results show that the two-phase fluid regions in both evaporator and condenser have great influence on the fluid flow and heat transfer performances in it.

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