Effect of Wavy Wall and Plate Bifurcations On Heat Transfer Enhancement in Microchannel

2021 ◽  
Author(s):  
Sathish Kumar D ◽  
Jayavel S
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Working Fluid ◽  
Thin Wall ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Entropy Generation Number ◽  
Transfer Characteristics ◽  
Overall Performance ◽  
Study Heat Transfer

Abstract Miniaturization of electronic components requires compact and effective cooling techniques to dissipate large heat flux without significant increase in pumping power. Microchannel heat sink with liquid as working fluid is a suitable technique for the purpose. In the present study, heat transfer characteristics in presence of vertical bifurcation placed in the downstream of the microchannel passage is studied numerically. Six types of bifurcating plates are considered under two categories: (i) thick-plate and (ii) wavy thin-wall. Water is taken as the working fluid and the flow rate has been varied in the Reynolds number range, 100 = Re = 1000.The effect of bifurcations on pressure drop, heat transfer and the overall thermal resistance are analyzed and compared with those of plane microchannel without bifurcation. The numerical results show that the usage of bifurcation in the microchannel reduces the overall thermal resistance. Field synergy number, entropy generation number and hydro-thermal performance index are calculated to quantify the overall performance improvement in the microchannel with bifurcations. Constant wavy thin-wall bifurcation has been found to improve the overall performance of the microchannel. The detailed geometry of the bifurcation, the resulting convective heat transfer characteristics and percentage improvement in the performance are reported.

scholarly journals Experimental study on heat transfer characteristics of a modified two-phase closed thermosyphon

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2481-2489 ◽  
Author(s):  
Babak Aghel ◽  
Masoud Rahimi ◽  
Saeed Almasi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Experimental Study ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Working Fluid ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Transfer Characteristics ◽  
Adiabatic Section

This study investigated the heat transfer characteristics of modified two-phase closed thermosyphon (TPCT) using water as the working fluid. In the modified TPCT, to reduce thermal resistance, a small TPCT was inserted inside the adiabatic section. For both the plain and modified thermosyphons the performances were determined at various heat inputs from 71-960 W. The results showed that the modified TPCT had less temperature difference between the evaporator and condenser sections than the plain one. According to the experimental data, in the modified TPCT, the thermal performance increased up to 20% over that of the unmodified one.

Heat transfer characteristics of nanofluids from a sinusoidal corrugated cylinder placed in a square cavity

2021 ◽  
pp. 095440622110272
Author(s):  
Salaika Parvin ◽  
Nepal Chandra Roy ◽  
Litan Kumar Saha ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Wide Range

A numerical study is performed to investigate nanofluids' flow field and heat transfer characteristics between the domain bounded by a square and a wavy cylinder. The left and right walls of the cavity are at constant low temperature while its other adjacent walls are insulated. The convective phenomena take place due to the higher temperature of the inner corrugated surface. Super elliptic functions are used to transform the governing equations of the classical rectangular enclosure into a system of equations valid for concentric cylinders. The resulting equations are solved iteratively with the implicit finite difference method. Parametric results are presented in terms of streamlines, isotherms, local and average Nusselt numbers for a wide range of scaled parameters such as nanoparticles concentration, Rayleigh number, and aspect ratio. Several correlations have been deduced at the inner and outer surface of the cylinders for the average Nusselt number, which gives a good agreement when compared against the numerical results. The strength of the streamlines increases significantly due to an increase in the aspect ratio of the inner cylinder and the Rayleigh number. As the concentration of nanoparticles increases, the average Nusselt number at the internal and external cylinders becomes stronger. In addition, the average Nusselt number for the entire Rayleigh number range gets enhanced when plotted against the volume fraction of the nanofluid.

A Fundamental View of the Flow Boiling Heat Transfer Characteristics of Nano-Refrigerants

2012 ◽  
Author(s):  
Lorenzo Cremaschi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Phase ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Working Fluid ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow Boiling Heat Transfer

Driven by higher energy efficiency targets and industrial needs of process intensification and miniaturization, nanofluids have been proposed in energy conversion, power generation, chemical, electronic cooling, biological, and environmental systems. In space conditioning and in cooling systems for high power density electronics, vapor compression cycles provide cooling. The working fluid is a refrigerant and oil mixture. A small amount of lubricating oil is needed to lubricate and to seal the sliding parts of the compressors. In heat exchangers the oil in excess penalizes the heat transfer and increases the flow losses: both effects are highly undesired but yet unavoidable. This paper studies the heat transfer characteristics of nanorefrigerants, a new class of nanofluids defined as refrigerant and lubricant mixtures in which nano-size particles are dispersed in the high-viscosity liquid phase. The heat transfer coefficient is strongly governed by the viscous film excess layer that resides at the wall surface. In the state-of-the-art knowledge, while nanoparticles in the refrigerant and lubricant mixtures were recently experimentally studied and yielded convective in-tube flow boiling heat transfer enhancements by as much as 101%, the interactions of nanoparticles with the mixture still pose several open questions. The model developed in this work suggested that the nanoparticles in this excess layer generate a micro-convective mass flux transverse to the flow direction that augments the thermal energy transport within the oil film in addition to the macroscopic heat conduction and fluid convection effects. The nanoparticles motion in the shearing-induced and non-uniform shear rate field is added to the motion of the nanoparticles due to their own Brownian diffusion. The augmentation of the liquid phase thermal conductivity was predicted by the developed model but alone it did not fully explain the intensification on the two-phase flow boiling heat transfer coefficient reported in previous work in the literature. Thus, additional nano- and micro-scale heat transfer intensification mechanisms were proposed.

Numerical Simulation Study of Impinging Jet Impact Fin Surface on Heat Transfer Characteristics

2013 ◽  
Vol 663 ◽  
pp. 586-591 ◽  
Author(s):  
Li Ming Zhou ◽  
Lei Zhu ◽  
Jing Quan Zhao ◽  
Meng Zheng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Thermal Resistance ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Transfer Characteristics ◽  
Jet Impact ◽  
Jet Array

Three-dimensional numerical simulation was implemented to analyze the heat transfer characteristics for jet impingement impact fin surface. 60 calculation cases were simulated to investigate the effects of different fin surfaces on heat transfer characteristics, and 12 jet array impingement cases were calculated for comparison. The results shown that the fin shape, the height and the fin arrangement were the critical factors to affect the jet impingement and the best combination were existed in a certain range. The thermal resistance of cylinder fin arranged in order was34.7 percent higher than that of cylinder fin arranged staggered. The thermal resistance of square fin arranged in order was38.9 percent higher than that of square fin arranged staggered .The heat transfer coefficients of impinging jet impact fin surface were better than that of jet array impingement. The fitting correlations on heat transfer of impinging jet impact fin surface were given.

Numerical Investigation of Impingement Heat Transfer on Concave- and Convex-Dimpled Plate With Different Dimple Arrangements

2016 ◽  
Author(s):  
Feng Zhang ◽  
Xinjun Wang ◽  
Jun Li ◽  
Rui Tan ◽  
Dongliang Wei
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Pressure Loss ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Impingement Cooling ◽  
Transfer Characteristics

The present numerical study is conducted to investigate the flow and heat transfer characteristics for impingement cooling on concave or convex dimpled plate with four different dimple arrangements. The investigation of the impingement cooling on the flat plate is also conducted to serve as a contrast and these results are compared with experimental measurements to verify the computational method. Dimples studied here are placed, relative to impingement holes, in either spanwise shifted, in staggered, in in-line, or in streamwise shifted arrangements. The flow structure, pressure loss and heat transfer characteristics of the concave and convex dimpled plate of four different dimple arrangements have been obtained and compared with flat plate for the Reynolds number range of 15000 to 35000. The results show that compared with flat plate, the added concave or convex dimples only causes a negligible increase in the pressure loss, and the pressure loss is insensitive to concave or convex dimple arrangement patterns. In addition, compared with flat plate, both spanwise shifted and staggered concave dimple arrangements show better heat transfer performance, while in-line concave dimple arrangement show worse results. Besides that, the heat transfer performance for streamwise shifted concave dimple arrangement is the worst. Furthermore, compared with flat plate, all convex dimple arrangements studied here show better heat transfer performance.

Simulation of Flow and Heat Transfer in the MTPV Systems

2013 ◽  
Vol 448-453 ◽  
pp. 3291-3295
Author(s):  
Ge Ping Wu ◽  
Jun Wang ◽  
Ping Lu
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Friction Factor ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Characteristics ◽  
Pressure Losses ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Different Types

Flow and heat transfer characteristics in the microchannel cooling passages with three different types of the MTPV systems are numerically investigated. Reynolds ranged from 100 to 1000 and hydraulic diameter from 0.4mm to 0.8mm. The steady, laminar flow and heat transfer equations are solved in a finite-volume method. The local heat transfer characteristics, thermal resistance, Nusselt numbers, friction factor and pressure losses of the different types are analyzed. A comparison of the heat transfer coefficient, pressure losses and friction factor of the different microchannels are also presented. The heat transfer performance of the rob bundles microchannel is found to be much better than others. However, the rectangular passage has the lowest thermal resistance than the other types of microchannels.

scholarly journals Heat-Transfer Characteristics of a Cryogenic Loop Heat Pipe for Space Applications

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1616
Author(s):  
Jaehwan Lee ◽  
Dongmin Kim ◽  
Jeongmin Mun ◽  
Seokho Kim
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Infrared Detectors ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Zero Gravity ◽  
Heat Transfer Characteristics ◽  
Space Applications ◽  
Transfer Characteristics ◽  
Start Up

Infrared detectors on satellites and spacecraft require cooling to increase their measurement sensitivity. To efficiently cool infrared detectors in a zero gravity environment and in limited spaces, a cryogenic loop heat pipe (CLHP) can be used to transfer heat over a certain distance by the capillary forces generated from porous wicks without a mechanical power source. The CLHP presented in this study transfers the heat load to a condenser 0.5 m away from an evaporator at temperatures below −150 °C. The CLHP with two evaporators includes a subloop for initial start-up, and uses a pressure reduction reservoir (PRR) for the supercritical start-up from room to cryogenic temperature. Nitrogen is used as the working fluid to verify the thermal behavior of the CLHP, and the heat-transfer capacity according to the nitrogen charging pressure of the PRR is investigated. To simulate a cryogenic environment, the CLHP is installed inside a space environment simulator, including a single-stage GM (Gifford McMahon) cryocooler to cool the condenser. The CLHP is horizontally installed to simulate zero gravity. The heat-transfer characteristics are experimentally evaluated through the loop circulation of the CLHP.

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