Numerical study of single-phase heat transfer performance of a mini/micro-channel integrated with multiple bypass micro-nozzles

2020 ◽  
pp. 1-40
Author(s):  
Raamkumar Loganathan ◽  
Sateesh Gedupudi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Pressure Drop ◽  
Wall Temperature ◽  
Single Phase ◽  
Numerical Study ◽  
Micro Channel ◽  
Temperature Uniformity ◽  
The Third

Abstract Surface temperature uniformity is an important factor in the thermal management of electronics. The present numerical study investigates the influence of multiple bypass injections on the wall temperature distribution of a single-phase mini/micro-channel. The proposed scheme consists of sending a fraction of the coolant through the channel inlet and injecting the remaining coolant through multiple bypass inlets on top of the channel positioned at different axial locations. The study explores four different configurations: the first one being three equispaced bypass inlets of uniform diameter, the second one being three equispaced bypass inlets of varying diameter, the third one being five equispaced bypass inlets of varying diameter, and the fourth one being five bypass inlets, but with three equispaced bypass inlets of varying diameter and the last two bypass inlets of the same diameter as that of the third inlet. The influence of bypass percentage on the thermal performance is evaluated. The fourth configuration results in a near uniform wall temperature distribution, with 82-89% reduction in the wall temperature non-uniformity compared to the no-bypass case. The reductions for the third, second and first configurations are 65-71%, 53-76% and 54-74%, respectively. The third configuration results in an average heat transfer coefficient enhancement of up to 34%. On the whole, the improvement in the wall temperature uniformity is higher than the increase in the pressure drop, and the increase in the channel heat transfer coefficient is higher than pressure drop for some cases.

Experimental and Numerical Study of Methanol-Water Mixture Single-Phase Heat Transfer in a Micro-Channel Heat Sink

2012 ◽  
Author(s):  
Chun K. Kwok ◽  
Matthew M. Asada ◽  
Jonathan R. Mita ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Single Phase ◽  
Numerical Study ◽  
Pure Water ◽  
Molar Fraction ◽  
Water Mixture ◽  
Micro Channel ◽  
Numerical Predictions

This paper presents an experimental study of single-phase heat transfer characteristics of binary methanol-water mixtures in a micro-channel heat sink containing an array of 22 microchannels with 240μm × 630μm cross-section. Pure water, pure methanol, and five methanol-water mixtures with methanol molar fraction of 16%, 36%, 50%, 63% and 82% were tested. Key parametric trends were identified and discussed. The experimental study was complemented by a three-dimensional numerical simulation. Numerical predictions and experimental data are in good agreement with a mean absolute error (MAE) of 0.87%.

scholarly journals Experimental and Simulation Study of Micro-Channel Backplane Heat Pipe Air Conditioning System in Data Center

2020 ◽  
Vol 10 (4) ◽  
pp. 1255
Author(s):  
Liping Zeng ◽  
Xing Liu ◽  
Quan Zhang ◽  
Jun Yi ◽  
Xiaohua Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Outlet Temperature ◽  
Transfer Performance ◽  
Micro Channel ◽  
Heat Transfer Capacity ◽  
The Heat Transfer Coefficient

This paper mainly studies the heat transfer performance of backplane micro-channel heat pipes by establishing a steady-state numerical model. Compared with the experimental data, the heat transfer characteristics under different structure parameters and operating parameters were studied, and the change of heat transfer coefficient inside the system, the air outlet temperature of the back plate and the influence of different environmental factors on the heat transfer performance of the system were analyzed. The results show that the overall error between simulation results and experimental data is less than 10%. In the range of the optimal filling rate (FR = 64.40%–73.60%), the outlet temperature at the lowest point and the highest point of the evaporation section is 22.46 °C and 19.60 °C, the temperature difference does not exceed 3 °C, and the distribution gradient in vertical height is small and the air outlet temperature is uniform. The heat transfer coefficient between the evaporator and the condenser is larger than the heat transfer coefficient under the conditions of low and high liquid charge rate. It increases gradually along the flow direction, and decreases gradually with the flow rate of the condenser. When the width of the flat tube of the evaporator increases from 20 mm to 28 mm, the internal pressure drop of the evaporator decreases by 45.83% and the heat exchange increases by 18.34%. When the number of evaporator slices increases from 16 to 24, the heat transfer increases first and then decreases, with an overall decrease of 2.86% and an increase of 87.67% in the internal pressure drop of the evaporator. The inclination angle of the corrugation changes from 30° to 60°, and the heat transfer capacity and pressure drop increase. After the inclination angle is greater than 60°, the heat transfer capacity and resistance decrease. The results are of great significance to system optimization design and engineering practical application.

scholarly journals Thermo-Fluidic Characteristics of Two-Phase Ice Slurry Flows Based on Comparative Numerical Methods

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 898 ◽  
Author(s):  
Shehnaz Akhtar ◽  
Haider Ali ◽  
Cheol Woo Park
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Flow Velocity ◽  
Mass Fraction ◽  
Single Phase ◽  
Ice Slurry ◽  
Two Phase ◽  
Ice Concentration ◽  
Eulerian Models

Ice slurry is a potential secondary refrigerant for commercial refrigeration systems because of its remarkable thermal properties. It is necessary to optimize the heat transfer process of ice slurry to reduce the energy consumption of the refrigeration system. Thus, this study investigates the heat transfer performance of single-phase (aqueous solution) and two-phase (ice slurry) refrigerants in a straight horizontal tube. The numerical simulations for ice slurry were performed with ice mass fraction ranging from 5% to 20%. The effects of flow velocity and ice concentration on the heat transfer coefficient were examined. The results showed that heat transfer coefficient of ice slurry is considerably higher than those of single-phase flow, particularly at high flow velocity and ice content, where increase in heat transfer with a factor of two was observed. The present results confirmed that ice slurry heat transfer ability is considerably affected by flow velocity and ice concentration in laminar range. Moreover, the second part of this paper reports on the credibility three distinct two-phase Eulerian–Eulerian models (volume of fluid (VOF), mixture, and Eulerian) for the experimental conditions reported in the literature. All two-phase models accurately predict the thermal field at low ice mass fraction but underestimate that at high ice mass fractions. Regardless of the thermal discrepancies, the Eulerian–Eulerian models provide quite reasonable estimation of pressure drop with reference to experimental data. The numerical predictions from the VOF model are more accordant with the experimental results and the maximum percentage error is limited to ~20% and ~13% for thermal and pressure drop predictions, respectively.

Numerical Study on Heat Transfer and Fluid Flow Characteristic of Tube Bank with Integral Wake Splitter-Effect of Wake Splitter Length

2013 ◽  
Vol 315 ◽  
pp. 650-654
Author(s):  
Abobaker Mohammed Alakashi ◽  
Hamidon Bin Salleh
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Characteristic ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Tube Bank ◽  
Computational Fluid Dynamics Cfd

The purpose of this research is to investigate effect of wake splitter to pressure drop and heat transfer characteristics in a tube bank with staggered arrangements. The pressure drop and averaged heat transfer coefficient of seven rows with five tubes in each row with integral wake splitter has been determined by means of 2-D simulation using commercial computational fluid dynamics (CFD) code Fluent. Two type of integral wake splitter length have been studied, 0.5D and 1D with different location. Simulations have been carried out at Reynolds number based on tube diameter from 5000 up to 27800. The results, presented in terms of pressure drop as well as averaged heat transfer coefficient values, show the influence of wake splitter length and direction. By adding 0.5D wake splitter at downstream direction leads to higher averaged heat transfer coefficient and reduction of the pressure drop.

scholarly journals Numerical Study of Laminar Flow Forced Convection of Water-Al2O3Nanofluids under Constant Wall Temperature Condition

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Hsien-Hung Ting ◽  
Shuhn-Shyurng Hou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Volume Concentration ◽  
Numerical Study ◽  
Pure Water ◽  
Particle Volume ◽  
Constant Wall Temperature ◽  
Water Based

This numerical study is aimed at investigating the forced convection heat transfer and flow characteristics of water-based Al2O3nanofluids inside a horizontal circular tube in the laminar flow regime under the constant wall temperature boundary condition. Five volume concentrations of nanoparticle, 0.1, 0.5, 1, 1.5, and 2 vol.%, are used and diameter of nanoparticle is 40 nm. Characteristics of heat transfer coefficient, Nusselt number, and pressure drop are reported. The results show that heat transfer coefficient of nanofluids increases with increasing Reynolds number or particle volume concentration. The heat transfer coefficient of the water-based nanofluid with 2 vol.% Al2O3nanoparticles is enhanced by 32% compared with that of pure water. Increasing particle volume concentration causes an increase in pressure drop. At 2 vol.% of particle concentration, the pressure drop reaches a maximum that is nearly 5.7 times compared with that of pure water. It is important to note that the numerical results are in good agreement with published experimental data.

Conjugate Heat Transfer in a Hexagonal Micro Channel Using Hybrid Nano Fluids

2016 ◽  
Author(s):  
Shreyas S. Hegde ◽  
Narendran Ganesan ◽  
N. Gnanasekaran
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Conjugate Heat Transfer ◽  
Nano Particles ◽  
Micro Channel ◽  
Nano Fluid ◽  
Nano Fluids ◽  
Effect Of Surface

Research is being focused on the use of micro channels with nano fluids as the heat sinks. This requires fundamental understanding of the heat transfer phenomenon in micro channels. The objective of this paper is to present results from a numerical study on laminar forced convection in a Hexagonal Micro Channel (HMC) heat sink. In particular, the numerical study is carried out using a single phase model. The fluid considered is Alumina-Copper hybrid Nano fluid. The performance of Al2O3+Cu+water is compared with Al2O3+water nano fluid and pure water with different volume fractions. The solid region of the channel is assumed as aluminum with a hydraulic diameter of 175μm. The solid and fluid regions of the micro channel are discretized using finite volume method by combining Navier Stokes equation and energy equation for conjugate heat transfer. The thermo physical properties for alumina nanoparticles are calculated by considering it as a spherical particle of 45nm diameter. The effect of surface roughness on convective heat transfer coefficient and pressure drop for the case of nano fluids is also considered. The analysis is further extended by adding pulsating input and by varying the velocity sinusoidally. The Brownian motion of nano particles is increased to study the efficiency of the heat sink. This ensures all the nano particles are in suspension and the randomness increases the micro convection in the fluid. Incorporating the pulsating flow increases the dispersion of the heat in the nano fluid at a faster rate and also decreases particle settlement in laminar flow. The combined effect of surface roughness and pulsating flow accounts for the change in the velocity profile and thermal boundary layer of the channel. Also the effect of surface roughness ranging from 0.2–0.6 is attempted and the variations in pressure drop, Nusselt number, and heat transfer coefficient are studied. The influence of hexagonal geometry and its interaction with alumina nano fluids is intensively studied by evaluating a three dimensional conjugate heat transfer model. The effect of side wall angle of 45°, 50° and 55° are computed to relate the velocity function with pressure drop, surface roughness and local heat transfer coefficient. The variation of Nusselt number with very low volume fraction of nano particles with a minimal amount of pressure drop is also presented.

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