scholarly journals Heat transfer enhancement of car radiator using aqua based magnesium oxide nanofluids

2015 ◽  
Vol 19 (6) ◽  
pp. 2039-2048 ◽  
Author(s):  
Hafiz Ali ◽  
Muhammad Azhar ◽  
Musab Saleem ◽  
Qazi Saeed ◽  
Ahmed Saieed
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Management ◽  
Heat Transfer Performance ◽  
Inlet Temperature ◽  
Fluid Temperature ◽  
Transfer Enhancement ◽  
Volumetric Concentration ◽  
Flow Rates ◽  
Transfer Rates

The focus of this research paper is on the application of water based MgO nanofluids for thermal management of a car radiator. Nanofluids of different volumetric concentrations (i.e. 0.06%, 0.09% and 0.12%) were prepared and then experimentally tested for their heat transfer performance in a car radiator. All concentrations showed enhancement in heat transfer compared to the pure base fluid. A peak heat transfer enhancement of 31% was obtained at 0.12 % volumetric concentration of MgO in basefluid. The fluid flow rate was kept in a range of 8-16 liter per minute. Lower flow rates resulted in greater heat transfer rates as compared to heat transfer rates at higher flow rates for the same volumetric concentration. Heat transfer rates were found weakly dependent on the inlet fluid temperature. An increase of 8?C in inlet temperature showed only a 6% increase in heat transfer rate.

scholarly journals Enhanced heat transfer characteristics of conjugated air jet impingement on a finned heat sink

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 279-288 ◽  
Author(s):  
Shuxia Qiu ◽  
Peng Xu ◽  
Liping Geng ◽  
Arun Mujumdar ◽  
Zhouting Jiang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Cooling System ◽  
Flow Characteristics ◽  
Jet Impingement ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Air Jet

Air jet impingement is one of the effective cooling techniques employed in micro-electronic industry. To enhance the heat transfer performance, a cooling system with air jet impingement on a finned heat sink is evaluated via the computational fluid dynamics method. A two-dimensional confined slot air impinging on a finned flat plate is modeled. The numerical model is validated by comparison of the computed Nusselt number distribution on the impingement target with published experimental results. The flow characteristics and heat transfer performance of jet impingement on both of smooth and finned heat sinks are compared. It is observed that jet impingement over finned target plate improves the cooling performance significantly. A dimensionless heat transfer enhancement factor is introduced to quantify the effect of jet flow Reynolds number on the finned surface. The effect of rectangular fin dimensions on impingement heat transfer rate is discussed in order to optimize the cooling system. Also, the computed flow and thermal fields of the air impingement system are examined to explore the physical mechanisms for heat transfer enhancement.

Falling Film Evaporation of Water on Horizontal Configured Tube Bundles

2010 ◽  
Author(s):  
Wei Li ◽  
Xiaoyu Wu ◽  
Zhong Luo
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Inlet Temperature ◽  
Falling Film ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Film Evaporation ◽  
Tube Bundles ◽  
Falling Film Evaporation

This paper reports an experimental study on falling film evaporation of water on 6-row horizontal configured tube bundles in a vacuum. Three types of configured tubes, Turbo-CAB-19fpi and −26fpi, Korodense, including smooth tubes for reference, were tested in a range of film Reynolds number from about 10 to 110. Results show that as the falling film Reynolds number increases, falling film evaporation goes from tubes partial dryout regime to fully wet regime; the mean heat transfer coefficients reach peak values in the transition point. Turbo-CAB tubes have the best heat transfer enhancement of falling film evaporation in both regimes, but Korodense tubes’ overall performances are better when tubes are fully wet. The inlet temperature of heating water has hardly any effects on the heat transfer, but the evaporation pressure has controversial effects. A correlation with errors within 10% was also developed to predict the heat transfer enhancement capacity.

Heat Transfer Enhancement Using Shaped Polymer Tubes: Fin Analysis

2004 ◽  
Vol 126 (2) ◽  
pp. 211-218 ◽  
Author(s):  
Zhihua Li ◽  
Jane H. Davidson ◽  
Susan C. Mantell
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Transfer Rate ◽  
Polymeric Materials ◽  
Transfer Enhancement ◽  
Transfer Rates ◽  
Shaped Tube ◽  
Polymer Tubes

The use of polymer tubes for heat exchanger tube bundles is of interest in many applications where corrosion, mineral build-up and/or weight are important. The challenge of overcoming the low thermal conductivity of polymers may be met by using many small-diameter, thin-walled polymer tubes and this route is being pursued by industry. We propose the use of unique shaped tubes that are easily extruded using polymeric materials. The shaped tubes are streamlined to reduce form drag yet the inside flow passage is kept circular to maintain the pressure capability of the tube. Special treatment is required to predict convective heat transfer rates because the temperature distribution along the outer surface of the shaped tubes is nonuniform. The average forced convection Nusselt number correlations developed for these noncircular tubes can not be used directly to determine heat transfer rate. In this paper, heat transfer rates of shaped tubes are characterized by treating the tubes as a base circular tube to which longitudinal fin(s) are added. Numerical solution of an energy balance on the fin provides the surface temperature distribution and a shaped tube efficiency, which can be used in the same manner as a fin efficiency to determine the outside convective resistance. The approach is illustrated for three streamlined shapes with fins of lenticular and oval profile. The presentation highlights the effects of the geometry and the Biot number on the tube efficiency and heat transfer enhancement. Convective heat transfer is enhanced for the oval shaped tube for 2000⩽Re⩽20,000 when Bi<0.3. For polymeric materials, the Biot number in most applications will be greater than 0.3, and adding material to the base tube reduces the heat transfer rate. The potential benefit of reduced form drag remains.

Heat Transfer in Annular Shear-Thinning Non-Newtonian Flows Over a Sudden Pipe Expansion

2016 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Power Law ◽  
Shear Thinning ◽  
Wall Heat Transfer ◽  
Transfer Enhancement ◽  
Transfer Rates ◽  
Newtonian Flows ◽  
Prandtl Numbers ◽  
Annular Pipe

Non-isothermal suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid are numerically studied within the steady laminar flow regime. The power-law constitutive equation is used to model the shear-thinning rheology of interest. A parametric study is performed to reveal the influence of annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers over the following range of parameters: k = {0, 0.5}; n = {1, 0.6}; and Pr = {1, 10, 100}. Heat transfer enhancement, i.e., wall heat transfer rates higher than the fully developed ones downstream of the expansion plane, is observed only for Pr = 10 and 100. In the case of Pr = 1, wall heat transfer rates monotonically increase to the fully developed value. Higher Pr, k, and n values, in general, result in more significant heat transfer enhancement downstream of the expansion plane. Further, shear-thinning non-Newtonian flows display two local peak wall heat transfer rates, in comparison with only one peak value in the case of Newtonian flows.

Experimental Heat Transfer Enhancement in Single-Phase Liquid Microchannel Cooling With Cross-Flow Synthetic Jet

2010 ◽  
Author(s):  
Ruixian Fang ◽  
Wei Jiang ◽  
Jamil Khan ◽  
Roger Dougal
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Performance ◽  
Synthetic Jet ◽  
Driving Voltage ◽  
Transfer Performance ◽  
Microchannel Flow ◽  
Transfer Enhancement ◽  
Synthetic Jet Actuator ◽  
Phase Liquid

The present study experimentally investigated a new hybrid cooling scheme by combination of a microchannel heat sink with a micro-synthetic jet actuator. The heat sink consisted of a single rectangular microchannel measured 550 μm wide, 500 μm deep and 26 mm long. The synthetic jet actuator with a 100 μm diameter orifice was placed right above the microchannel and 5 mm downstream from the channel inlet. Micro jet is synthesized from the fluid flowing through the microchannel. Periodic disturbance is generated when the synthetic jet interacts with the microchannel flow. Heat transfer performance is enhanced as local turbulence is generated and propagated downstream the microchannel. The scale and frequency of the disturbance can be controlled by changing the driving voltage and frequency of the piezoelectric driven synthetic jet actuator. The effects of synthetic jet on microchannel heat transfer performance were studied based on the microchannel flow Reynolds number, the jet operating voltage and frequency, respectively. It shows that the synthetic jet has a greater heat transfer enhancement for microchannel flow at lower Reynolds number. It also shows that the thermal effects of the synthetic jet are functions of the jet driving voltage and frequency. We obtained around 42% heat transfer enhancement for some test cases, whereas the pressure drop across the microchannel increases very slightly. The paper concludes that the synthetic jet can effectively enhance single-phase liquid microchannel heat transfer performance and would have more promising enhancements if multi-jets are applied along the microchannel.

Applied Pulsed Flow for Single-Phase Convective Heat Transfer Enhancement in a Laminar Flow Cooling System

2008 ◽  
Author(s):  
Bolaji O. Olayiwola ◽  
Gerhard Schaldach ◽  
Peter Walzel
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Cooling System ◽  
Transfer Enhancement ◽  
Flow Rates ◽  
The Heat Transfer Coefficient

Experimental and CFD studies were performed to investigate the enhancement of convective heat transfer in a laminar cooling system using flow pulsation in a flat channel with series of regular spaced fins. Glycerol-water mixtures with dynamic viscosities in the range of 0.001 kg/ms–0.01 kg/ms were used. A steady flow Reynolds number in the laminar range of 10 &lt; Re &lt; 1200 was studied. The amplitudes of the applied pulsations are in the range of 0.25 &lt; A &lt; 0.55 mm and the frequency range is 10 &lt; f &lt; 60 Hz. Two different cooling devices with active length L = 450 mm and 900 mm were investigated. CFD simulations were performed on a parallel-computer (Linux-cluster) using the software suit CFX11 from ANSYS GmbH, Germany. The rate of cooling was found to be significant at moderate low net flow rates. In general, no significant heat transfer enhancement at very low and high flow rates was obtained in compliance with the experimental data. The heat transfer coefficient was found to increase with increasing Prandtl number Pr at constant oscillation Reynolds number Reosc whereas the ratio of the hydraulic diameter to the length of the channel dh/L has insignificant effect on the heat transfer coefficient. This is due to enhanced fluid mixing. CFD results allow for performance predictions of different geometries and flow conditions.

Passive Heat Transfer Enhancement in Microchannels Using Wall Features

2007 ◽  
Author(s):  
Ravi Arora ◽  
Anna Lee Tonkovich ◽  
Mike J. Lamont ◽  
Thomas Yuschak ◽  
Laura Silva
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Flow Rate ◽  
Transfer Rate ◽  
Transfer Enhancement ◽  
Flow Rates ◽  
Feature Design

The two important considerations in the design of a heat exchanger are — the total heat transfer rate and the allowable pressure drop. The allowable pressure drop defines the maximum flow rate through a single microchannel and economics drives the design towards this flow rate. Typically the flow rate in the microchannel is in laminar flow regime (Re < 2000) due to smaller hydraulic diameter. The laminar flow heat transfer in a smooth microchannel is limited by the boundary layer thickness. Commonly the heat transfer rate is enhanced by passively disrupting the laminar boundary layer using protrusions or depressions in the channel walls. More often these methods are best applicable at small range of Reynolds number where the heat transfer rate enhancement is more than the pressure drop increase and break down as the flow rate is changed outside the range. The benefit of a flow disruption method can be reaped only if it provides higher heat transfer enhancement than the increase in the pressure drop at the working flow rates in the microchannel. A heat transfer efficient microchannel design has been developed using wall features that create stable disrupted flow and break the laminar boundary layer in a microchannel over a wide range of flow rates. The paper experimentally investigates the developed design for the heat transfer enhancement and pressure drop increase compared to a smooth wall microchannel. A simple microchannel device was designed and fabricated with and without wall features. The experiments with single gas phase fluid showed promising results with the developed wall feature design as the heat transfer rate increase was 20% to 80% more than the pressure drop increase in the laminar regime. The wall feature design was an important variable to affect the magnitude of performance enhancement in different flow regime. A general criterion was developed to judge the efficacy of wall feature design that can be used during a microchannel heat exchanger design.

Heat Transfer in Liquid-Liquid Taylor Flow in a Mini-Scale Tube With Constant Wall Temperature

2015 ◽  
Author(s):  
W. M. Adrugi ◽  
Y. S. Muzychka ◽  
K. Pope
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Wall Temperature ◽  
Silicone Oil ◽  
Transfer Enhancement ◽  
Constant Wall Temperature ◽  
Flow Rates ◽  
Taylor Flow ◽  
Low Viscosity ◽  
Wide Range

In this paper, heat transfer enhancement using liquid-liquid Taylor flow is examined. The experiments are conducted in mini-scale tubes with constant wall temperature. The segmented flow is created using several fractions of low viscosity silicone oil (1 cSt) and water for a wide range of flow rates and segment lengths. The variety of liquids and flow rates change the Prandtl, Reynolds, and capillary numbers. The dimensionless mean wall flux and the dimensionless thermal flow length are used to analyze the experimental heat transfer data. The comparison shows the heat transfer rate for Taylor flow is higher than in single-phase flow. The heat transfer enhancement occurs due to internal circulation in the fluid segments.

Effect of Protuberances in the Heat Transfer Enhancement in Mini-Channels

2021 ◽  
Author(s):  
Ariel Cruz Diaz ◽  
Gerardo Carbajal
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Performance ◽  
Heat Removal ◽  
Working Fluid ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Mini Channels

Abstract This study presents the effects of adding an array of protrusions in a microchannel for heat transfer enhancement. The presence of mini-channels increases the overall heat transfer area and boosts the mixing development near the solid-fluid interaction; therefore, it can remove more heat than conventional mini-channels without protuberances. A numerical study proved that protuberances in a mini-channel increase the heat transfer performance by disturbing the relative fluid motion near the solid wall. The numerical simulation was performed with three different protuberances arrays: aligned, staggered, and angular. Each array consists of a thin flat plate with a hemispherical shape; the working fluid and the solid materials were water and copper. The study also includes the effect of different Reynolds numbers: 1,000, 1,500, and 2,000. Three heat inputs were applied in the numerical simulation; these were 1W, 3W, and 5W. The study was compared with a simple microchannel with non-protuberances to analyze the microchannel performance regarding heat removal and pressure drop. For heat transfer performance, the best array was the staggering array with a maximum heat removal increase of 5.26 percent. In terms of pressure drop performance, the best array was the aligned array, with a maximum increase of 34.73 percent.

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