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An experimental study was conducted to investigate the use of waterbased aluminum oxide nanofluids in enhancing the heat transfer performance of heat exchangers. Two types of heat exchangers were studied: a blocktype heat exchanger for an electronic system cooling, and a radiator-type heat exchanger simulating an automobile cooling system. Tests conducted on the block heat exchanger used 20 nm alumina particles at a concentration of 5% by mass (1.3% by volume), while tests conducted on the radiator-type heat exchanger used 50 nm alumina particles at a concentration of 3% by mass (0.8% by volume). Tests conducted on the electronic heat sink system show an average enhancement of about 20% in heat transfer coefficient, while tests conducted on the radiator-type heat exchanger show a substantial enhancement in heat exchanger effectiveness that reaches almost 49%. Results demonstrate that the application of nanofluids in low concentrations is sufficient to cause a considerable improvement in the system‘s thermal performance. Results also show that the increase in bulk flow heat transfer coefficient happens at the expense of the increase in fluid pumping power caused by the increase in fluid viscosity. European Scientific Journal July 2016 /SPECIAL/ edition ISSN: 1857 - 7881 (Print) eHeat Transfer Investigation Of Aluminum Oxide Nanofluids In Heat ExchangersRoy Jean Issa 0Ph.D.
00 West Texas A&M University, USAAn experimental study was conducted to investigate the use of waterbased aluminum oxide nanofluids in enhancing the heat transfer performance of heat exchangers. Two types of heat exchangers were studied: a blocktype heat exchanger for an electronic system cooling, and a radiator-type heat exchanger simulating an automobile cooling system. Tests conducted on the block heat exchanger used 20 nm alumina particles at a concentration of 5% by mass (1.3% by volume), while tests conducted on the radiator-type heat exchanger used 50 nm alumina particles at a concentration of 3% by mass (0.8% by volume). Tests conducted on the electronic heat sink system show an average enhancement of about 20% in heat transfer coefficient, while tests conducted on the radiator-type heat exchanger show a substantial enhancement in heat exchanger effectiveness that reaches almost 49%. Results demonstrate that the application of nanofluids in low concentrations is sufficient to cause a considerable improvement in the system's thermal performance.
Results also show that the increase in bulk flow heat transfer coefficient happens at the expense of the increase in fluid pumping power caused by the increase in fluid viscosity.Heat Transfer Coefficient; Effectiveness; Nanofluid; AL2O3-volume concentration with 36 nm particles (Mintsa, 2009), and to aconsiderable enhancement of 88% at 12% volume concentration with 75 nmparticles (Ghanbarpour, 2014). It is clearly evident in those studies that thebulk fluid thermal conductivity in general increases with the increase innanoparticles volume concentration.The benefit of using nanofluids in heat exchanger applications havebeen investigated by several researchers. In the cooling of a microchannelheat sink, Ijam et al. (2012) has shown that adding Al2O3 nanoparticles towater at 4% volume concentration improved the heat flux by about 3%, andby about 17.3% when the particle volume concentration was 0.8%. Ijamand Saidur (2012) also showed that the addition of SiC nanoparticles towater at 4% volume fraction resulted in an improvement between 7.3 to12.4% in heat flux.
Selvakumar and Suresh (2012) studied the performanceof CuO water-based nanofluid in an electronic heat sink. Their studyrevealed a 29% improvement in heat transfer coefficient for 0.2% volumefraction of CuO in deionized water. Hashemi et al. (2012) studied heattransfer enhancement in a nanofluid-cooled miniature heat sink application.Their study showed an enhancement in the heat transfer coefficient by about27% when using SiO2 at a concentration of 5% concentration by volume.Khedkar et al. (2013) studied the heat transfer in a concentric tube heatexchanger with different volume fractions of water-based Al2O3 nanofluids.It was observed that at 3% volume fraction, the optimal overall heat transfercoefficient was about 16% higher than water.Sun et al. (2015)analyzed theflow and convective heat transfer characteristics of Fe2O3 water-basednanofluids inside inner grooved copper and smooth cooper tubes.
For thesame mass fraction of Fe2O3 nanoparticles, the convective heat transfercoefficient was better in the inner grooved copper tube than in the smoothcopper tube. The enhancement in heat transfer coefficient associated withthe inner grooved copper tube was about 33.5% for Fe2O3 massconcentration of 0.4%. All of the above researchers have examined theeffect of nanoparticles concentration on heat transfer enhancement, and havestudied different types of nanoparticles. However, there are contradictoryconclusions on the heat transfer enhancement at lower nanoparticleconcentrations among different researchers. Also, still limited researchstudies have been conducted on the evaluation of alumina nanofluidproperties and their performance in heat exchanger applications. The currentstudy aims at investigating some of these issues in addition to investigatingthe thermal and rheological properties of water-based alumina nanofluids.Experimental Setup:a) Electronic Heat Sink ApplicationA closed-loop cooling system using block heat exchangers was builtto evaluate the heat transfer performance associated with the use of awaterbased nanofluid with alumina particles as a cooling fluid. A general pictureof the experimental setup is shown in figure 1a.
The nanofluid was preparedby mixing alumina nanoparticles with 20 nm average size in deionized waterfor a suspension concentration of 5% by mass (1.3% by volume). A digitalgeared-pump was used to pressurize the nanofluid for circulation in theclosed-loop system. Two block heat exchangers were used in the system:one to heat the nanofluid (HXR1), and the other to cool the fluid (HXR2).The interior of the block heat exchanger (figure 1b) consisted of 10 channelsthrough which the cooling fluid travelled back and forth.The heat exchanger that was used to heat the nanofluid sat on top of a500 W plate heater separated by a 6.2 mm thick aluminium plate. Atemperature control system was used to control the input heat to the baseplate of the heat exchanger.
The heat exchanger that was used for coolingthe nanofluid sat approximately five inches above the base of the closed-loopsystem. Two cooling fans rated at 120 cfm each were used to cool the upperand lower surfaces of this heat exchanger. Once the fluid exited HXR2 itflowed into a 2-litres reservoir tank. A compact digital mixer systemproviding a top speed of 2,500 rpm was embedded in the tank. To achieveclosed-loop circulation, the outlet from the reservoir tank fed directly into thepump inlet. Thermocouples were embedded at various locations to recordthe temperature variation throughout the system.b) Radiator-Type Heat Exchanger ApplicationAnother closed-loop cooling system was also constructed to evaluatethe performance of a radiator-type heat exchanger as shown in the sketch offigure 2.
The heat exchanger (202 mm x 89 mm x 160 mm) had a 10-passcross-flow finned-tubes with a single tube inlet and outlet, where the tubeswere arranged in a staggered array. Each tube had an inner diameter of 7.73mm, an outer diameter of 9.5 mm, and a length of 12.7 cm. 80 fin plates of0.15 mm thickness, 120 mm width, and 38 mm depth were packaged normalto the tubes to form narrow passes having 1.4 mm separation distance whereair blowing from a fan passed through. A collection tank with a high-speedagitator thoroughly mixed the nanofluid, alumina-water based using 50 nmAL2O3 particles with a mass concentration of 3% (0.8% by volume), beforeit was circulated using a circulation pump. A controlled heating system wasinstalled in the tank to maintain the circulating fluid temperature within adesired range. The fluid was cooled using a blowing fan that was attachedon one side of the heat exchanger.
An experimental study was conducted to investigate the use of waterbased aluminum oxide nanofluids in enhancing the heat transfer performance of heat exchangers. Two types of heat exchangers were studied: a blocktype heat exchanger for an electronic system cooling, and a radiator-type heat exchanger simulating an automobile cooling system.
Tests conducted on the block heat exchanger used 20 nm alumina particles at a concentration of 5% by mass (1.3% by volume), while tests conducted on the radiator-type heat exchanger used 50 nm alumina particles at a concentration of 3% by mass (0.8% by volume). Tests conducted on the electronic heat sink system show an average enhancement of about 20% in heat transfer coefficient, while tests conducted on the radiator-type heat exchanger show a substantial enhancement in heat exchanger effectiveness that reaches almost 49%. Results demonstrate that the application of nanofluids in low concentrations is sufficient to cause a considerable improvement in the system‘s thermal performance. Results also show that the increase in bulk flow heat transfer coefficient happens at the expense of the increase in fluid pumping power caused by the increase in fluid viscosity.
European Scientific Journal July 2016 /SPECIAL/ edition ISSN: 1857 - 7881 (Print) eHeat Transfer Investigation Of Aluminum Oxide Nanofluids In Heat ExchangersRoy Jean Issa 0Ph.D. 00 West Texas A&M University, USAAn experimental study was conducted to investigate the use of waterbased aluminum oxide nanofluids in enhancing the heat transfer performance of heat exchangers. Two types of heat exchangers were studied: a blocktype heat exchanger for an electronic system cooling, and a radiator-type heat exchanger simulating an automobile cooling system. Tests conducted on the block heat exchanger used 20 nm alumina particles at a concentration of 5% by mass (1.3% by volume), while tests conducted on the radiator-type heat exchanger used 50 nm alumina particles at a concentration of 3% by mass (0.8% by volume). Tests conducted on the electronic heat sink system show an average enhancement of about 20% in heat transfer coefficient, while tests conducted on the radiator-type heat exchanger show a substantial enhancement in heat exchanger effectiveness that reaches almost 49%. Results demonstrate that the application of nanofluids in low concentrations is sufficient to cause a considerable improvement in the system's thermal performance. Results also show that the increase in bulk flow heat transfer coefficient happens at the expense of the increase in fluid pumping power caused by the increase in fluid viscosity.Heat Transfer Coefficient; Effectiveness; Nanofluid; AL2O3-volume concentration with 36 nm particles (Mintsa, 2009), and to aconsiderable enhancement of 88% at 12% volume concentration with 75 nmparticles (Ghanbarpour, 2014).
It is clearly evident in those studies that thebulk fluid thermal conductivity in general increases with the increase innanoparticles volume concentration.The benefit of using nanofluids in heat exchanger applications havebeen investigated by several researchers. In the cooling of a microchannelheat sink, Ijam et al. (2012) has shown that adding Al2O3 nanoparticles towater at 4% volume concentration improved the heat flux by about 3%, andby about 17.3% when the particle volume concentration was 0.8%. Ijamand Saidur (2012) also showed that the addition of SiC nanoparticles towater at 4% volume fraction resulted in an improvement between 7.3 to12.4% in heat flux. Selvakumar and Suresh (2012) studied the performanceof CuO water-based nanofluid in an electronic heat sink.
Their studyrevealed a 29% improvement in heat transfer coefficient for 0.2% volumefraction of CuO in deionized water. Hashemi et al. (2012) studied heattransfer enhancement in a nanofluid-cooled miniature heat sink application.Their study showed an enhancement in the heat transfer coefficient by about27% when using SiO2 at a concentration of 5% concentration by volume.Khedkar et al. (2013) studied the heat transfer in a concentric tube heatexchanger with different volume fractions of water-based Al2O3 nanofluids.It was observed that at 3% volume fraction, the optimal overall heat transfercoefficient was about 16% higher than water.Sun et al.
(2015)analyzed theflow and convective heat transfer characteristics of Fe2O3 water-basednanofluids inside inner grooved copper and smooth cooper tubes. For thesame mass fraction of Fe2O3 nanoparticles, the convective heat transfercoefficient was better in the inner grooved copper tube than in the smoothcopper tube. The enhancement in heat transfer coefficient associated withthe inner grooved copper tube was about 33.5% for Fe2O3 massconcentration of 0.4%. All of the above researchers have examined theeffect of nanoparticles concentration on heat transfer enhancement, and havestudied different types of nanoparticles.
Fluid Flow And Heat Transfer In Wellbores Pdf Readers
However, there are contradictoryconclusions on the heat transfer enhancement at lower nanoparticleconcentrations among different researchers. Also, still limited researchstudies have been conducted on the evaluation of alumina nanofluidproperties and their performance in heat exchanger applications. The currentstudy aims at investigating some of these issues in addition to investigatingthe thermal and rheological properties of water-based alumina nanofluids.Experimental Setup:a) Electronic Heat Sink ApplicationA closed-loop cooling system using block heat exchangers was builtto evaluate the heat transfer performance associated with the use of awaterbased nanofluid with alumina particles as a cooling fluid. A general pictureof the experimental setup is shown in figure 1a.
The nanofluid was preparedby mixing alumina nanoparticles with 20 nm average size in deionized waterfor a suspension concentration of 5% by mass (1.3% by volume). A digitalgeared-pump was used to pressurize the nanofluid for circulation in theclosed-loop system. Two block heat exchangers were used in the system:one to heat the nanofluid (HXR1), and the other to cool the fluid (HXR2).The interior of the block heat exchanger (figure 1b) consisted of 10 channelsthrough which the cooling fluid travelled back and forth.The heat exchanger that was used to heat the nanofluid sat on top of a500 W plate heater separated by a 6.2 mm thick aluminium plate. Atemperature control system was used to control the input heat to the baseplate of the heat exchanger.
The heat exchanger that was used for coolingthe nanofluid sat approximately five inches above the base of the closed-loopsystem. Two cooling fans rated at 120 cfm each were used to cool the upperand lower surfaces of this heat exchanger.
Once the fluid exited HXR2 itflowed into a 2-litres reservoir tank. A compact digital mixer systemproviding a top speed of 2,500 rpm was embedded in the tank.
Heat Transfer Designs
To achieveclosed-loop circulation, the outlet from the reservoir tank fed directly into thepump inlet. Thermocouples were embedded at various locations to recordthe temperature variation throughout the system.b) Radiator-Type Heat Exchanger ApplicationAnother closed-loop cooling system was also constructed to evaluatethe performance of a radiator-type heat exchanger as shown in the sketch offigure 2. The heat exchanger (202 mm x 89 mm x 160 mm) had a 10-passcross-flow finned-tubes with a single tube inlet and outlet, where the tubeswere arranged in a staggered array.
Fluid Flow And Heat Transfer In Wellbores Pdf Reader Free
Each tube had an inner diameter of 7.73mm, an outer diameter of 9.5 mm, and a length of 12.7 cm. 80 fin plates of0.15 mm thickness, 120 mm width, and 38 mm depth were packaged normalto the tubes to form narrow passes having 1.4 mm separation distance whereair blowing from a fan passed through. A collection tank with a high-speedagitator thoroughly mixed the nanofluid, alumina-water based using 50 nmAL2O3 particles with a mass concentration of 3% (0.8% by volume), beforeit was circulated using a circulation pump.
A controlled heating system wasinstalled in the tank to maintain the circulating fluid temperature within adesired range. The fluid was cooled using a blowing fan that was attachedon one side of the heat exchanger.