USING THE NANOFLUID TO IMPROVE THE HEAT TRANSFER IN THE DOUBLE PIPE HEAT EXCHANGER

Transcription

1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 12, December 2018, pp , Article ID: IJCIET_09_12_064 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed USING THE NANOFLUID TO IMPROVE THE HEAT TRANSFER IN THE DOUBLE PIPE HEAT EXCHANGER Asst.Prof.Dr.MaatheAbdulwahed, Asst.Prof.Khalid M. Owaid, Al Mustansiriyah University, College of Engineering,Materials Engineering Dept. ABSTRACT Heat transfer is the science that seeks to predict the energy transfer that may take place between material bodies as a result of a temperature difference. In the present work Experimental investigation of heat transfer enhancement in double pipe heat exchanger with and without addition of nanofluid have been carried out. Experimental work included to design of double pipe heat exchanger with calculated dimensions.four type of working fluids are used (distilled water and distilled water with different volume concentration (0.3,1.2and 2.1). Zinc Oxide ZnO nanoparticle powder with 20 nm diameter is dispersed in distilled water with different volume concentrations 0.3, 1.2 and 2.1 % by volume is used as nanofluid. The nanofluids were prepared by using ultrasonic cleaner with 10 hours of continuous sonication at 1200 W (sonication power). The sedimentation in nanofluids was observed after about six hours. The working fluid of 2.1%ZnO was chosen as an optimum according to the results that obtained from experimental work. The experimental results indicate that heat transfer coefficient is increased by increasing particles volume concentration as well as Reynolds, heat flow and Nusslet Number Keywords: Heat transfer coefficient, nanofluid, Nusselt number. Cite this Article:, Using the Nanofluid to Improve the Heat Transfer in the Double Pipe Heat Exchanger, International Journal of Civil Engineering and Technology, 9(12), 2018, pp INTRODUCTION Enhancement of Heat transfer achived by employing various techniques mythologies such as increasing either heat transfer surface or increasing heat transfer coefficient between the fluid and surface that allow high heat transfer rate in small volume. In general, the enhancement techniques can be divided into two types: active and passive techniques as follow: editor@iaeme.com

2 The active techniques require external forces, e.g. electric field, acoustic, and surface vibration. The passive techniques require special surface geometries such as roughness surface, treated surface and extended surface or fluid additives. Both techniques have been used for improving heat transfer in heat exchangers. Due to their compact structure and high heat transfer coefficient, double pipe has been introduced as one of the passive heat transfer enhancement techniques and are widely used in various industrial applications. Recently another technique to enhance heat transfer rate by adding nano-sized particles of highly thermally conductive materials have been used such as, metal, metal oxides into base fluid to improve thermal conductivity of fluid. The dispersion or suspension this particle in the base fluid is called nanofluid. 2. LITERATURE REVIEW Murshed and others (2005)studied experimentally the increasing of thermal conductivity buy using nanofluids which are prepared by dispersing TiO2 nanoparticles in rod-shapes of 10nm 40nm (diameter by length) and in spherical shapes of 15 nm in deionized water. The experimental results show that the thermal conductivity increases with an increase of particle volume fraction. For TiO2 particles of 10nm 40nm and 15 nm dimensions with maximum 5% volume fraction, the enhancement is observed to be nearly 33%. Suresha and others (2009) studied the experimental investigations and theoretical determination of effective thermal conductivity and viscosity of Al2O3/H2Onanofluid are reported in this paper. Al2O3/water nanofluid with a nominal diameter of 43nm at different vol-ume concentrations (0.33 5%) at room temperature were used for the investigation. Both the thermal conductivity and viscosity of nanofluids increase with the nanoparticle volume concentration. Rajan and others (2012) studied thermal conductivity enhancements CuO water nanofluids which were prepared from non-spherical CuO nanoparticles by dispersing them in water through the aid of ultra sonication along with the use of Tiron as dispersant. Thermal conductivity enhancements of 13% and 44% have been obtained with 0.016vol% CuO water nanofluids at 28 C and 55 C respectively. Reza Aghayari and others (2016) showed that the heat transfer of a fluid containing nanoparticles of aluminum oxide with the water volume fraction ( ) percent has been reported. Heat transfer of the fluid containing nano water aluminum oxide with a diameter of about 20 nm in a horizontal double pipe counter flow heat exchanger under turbulent flow conditions was studied. The results showed that the heat transfer of nanofluid in comparison with the heat transfer of fluid is slightly higher than 12 percent. Seyfollah Saedodin(2017) studied experimentally the thermal conductivity of CuO/EGâ water nanofluid in different temperatures and solid volume fractions. The nanofluid has been prapared in different solid concentrations ranging from 0.1% to 2% and temperatures within 20 to 50 C. Based on the experimental data, new correlations for predicting the thermal conductivity of CuO/EGâ water at different temperatures have been proposed. The results indicate that with the increase of the solid concentration, the thermal conductivity of the nanofluid increases. Also, the thermal conductivity of the nanofluid increases while the temperature increases editor@iaeme.com

3 Using the Nanofluid to Improve the Heat Transfer in the Double Pipe Heat Exchanger Figure. 1: Comparison of thermal conductivity of different conventional heat transfer fluids and solids 3. PREPARATION OF NANOFLUID The first key step in applying nanophase particles to change the heat transfer performance of conventional fluids is preparation of nanofluid. In order to get stable, durable suspension, with low agglomeration of particles, the nanoparticles and the distilled water are mixed directly using electric mixer (1950 RPM) for 20 minutes. Nanofluid samples are prepared for different concentrations by dispersing pre weighed quantities of dry (Zinc Oxide (ZnO) (30 nm)) nanoparticle in (3 litters) the volume of distilled water used in the test rig. The process results in uniform dispersions for the duration of the experiments. The properties (density,thermal conductivity and specific heat) for the nanoparticle usedare listed in table Properties of Nanofluids The thermo physical properties of the prepared ZnO/water nanofluid are determined at the fluids bulk mean temperature, Tb by using the correlations widely used in the literature. The density of the nanofluid is determined using Pak and Cho s equation (Pak and Cho1998). Ρ 1 φρ φρ (1) Where is volume fraction of nano particle. Indices of p, bf and nf refers to nanoparticles, base fluid, and nanofluid, respectively. The specific heat of the nanofluid is calculated using Xuan and Roetzel s equation (Xuan and Roetzel 2000). Cp1 φcp φcp (2) Hamilton and Crosser (Hamilton and Crosser1962) developed one of the basic models for the prediction of thermal conductivity of nanofluids as follows: K nf= ( (3) Where n is the empirical shape factor. Thermal conductivity of nanofluids also can be calculated by using Wasp (1977) model that is defined as the following: editor@iaeme.com

4 Knf= ( (4) Finally, (Timofeeva et al, 2007) introduce the effective medium theory to compute thermal conductivity of Nano fluid, which defined as below: 1+3 ] (5) The viscosity model used in this work is developed by Brinkman (1952) 1 µ nf = µ 2. 5 ( ) water 1 ϕ (6) Bachelor (1977) developed a regression equation (7) for viscosity of nanofluids with spherical shape nanoparticles as follows:! " = # ]! (7) Einstein has developed a viscosity correlation (Drew and passman- 1999) in terms of nanoparticle volume concentration in the base fluid, when the nanoparticle volume concentration is lower than 5%, and is given by! " = # ]! (8) Wong and Xu (1999) proposed a model to predict the dynamic viscosity of nanofluid that expressed as following:! " = # ]! (9) Heat transfer coefficient is calculated from: U = Where: +, / +, 123 4, / : 0, Heat transfer ratethe (W) is calculated from Ao=;<=>, Ai=;<B> Q h =md C p (T T F ) (11) Where Q is the rate of heat transfer (W), G D is the nanofluid mass flowrate (kg/s) and Cp is the specific heat capacity of the nanofluid (J/Kg.K). The heat transfer rate can also be determined from the Newton s Law of Cooling: Q C=GD C p (H I T i) (12) Table 1: Physical properties of ZnO nanoparticle and water (10) S. No 1 2 Nanoparticle /fluid ZnO Water Mean Diameter (nm) 30 - Density (Kg/m 3 ) Thermal conductivity (W/mK) Specific Heat (J/kg K) editor@iaeme.com

5 Using the Nanofluid to Improve the Heat Transfer in the Double Pipe Heat Exchanger 3. EXPERIMENTAL PROCEDURE The setup used in this experiment as shown in Fig.2. This experimental setup consists of two tanks (tank A and 'B ) with a capacity of 500 ltrs were used to store the water.1200 W immiscible heater is fitted in the tank A to heat the water. Two centrifugalpumps were used to circulate the water into the test section. One pump is used tocirculate the cold water in the outer tube and the other pump is used to circulate thehot water in the inner tube. The outer pipe of the test section is made of PVC, 50.8 mm outside diameter and 42.9 mm inner diameter. The inner tube is made from smooth copper tubing with 12.7 mm outer diameter and 10.2 mm inner diameter and the heat exchange length of 82 cm. To reduce the heat loss from the system the test section is perfectly insulated by using rock wool. The K- type thermocouples are used to measure the temperature at the inlet and outlet side tubes. Figure.2: schematic diagram of the experimental test rig. 4. RESULT AND DISCUSSION Figures (3, 4,5and6) show the effect of ZnO nanoparticles concentration on the convective heat transfer coefficient comparing with different working fluids at the same working conditions.these figures clearly show that the convective heat transfer coefficient of the ZnO/water nanofluid is higher than other fluids. The highest heat transfer coefficient is obtained by using 2.1 Vol% of ZnO/water nanofluid editor@iaeme.com

6 Figure. 3: Comparison of heat transfer coefficient of different working fluids at inlet temperature =35 o c Figure. 4: Comparison of heat transfer coefficient of different working fluids at inlet temperature =45 o c Figure 5: Comparison of heat transfer coefficient of different working fluids at inlet temperature =55 o c editor@iaeme.com

7 Using the Nanofluid to Improve the Heat Transfer in the Double Pipe Heat Exchanger Figure 6: Comparison of heat transfer coefficient of different working fluids at inlet temperature =65 o c Figures (7,8,9and10) show the effect of ZnO nanoparticles concentration on the Nusselt number of comparing with different working fluids at the same working conditions.these figures clearly show that the Nusselt number of the ZnO/water nanofluid is higher than other fluids.the highest Nusselt number is obtained by using 2.1 Vol% of ZnO/water nanofluid. Figure 7: Comparison of Nusslet number of different working fluids at inlet temperature =35 o c Figure 8: Comparison of Nusslet number of different working fluids at inlet temperature =45 o c editor@iaeme.com

8 Figure. 9: Comparison of Nusslet number of different working fluids at inlet temperature =55 o c Figure 10: Comparison of Nusslet number of different working fluids at inlet temperature =65 o c Figures (11, 12,13and14) show the effect of ZnO nanoparticles concentration on the heat transfer rate comparing with different working fluids at the same working conditions. These figures clearly show that the heat transfer raste of the ZnO/water nanofluid is higher than other fluids.the highest heat transfer rate is obtained by using 2.1 Vol% of ZnO/water nanofluid. Figure 11: Comparison of Heat transfer rate of different working fluids at inlet temperature =35 o c editor@iaeme.com

9 Using the Nanofluid to Improve the Heat Transfer in the Double Pipe Heat Exchanger Figure 12: Comparison of Heat transfer rate of different working fluids at inlet temperature =45 o c Figure 13: Comparison of Heat transfer rate of different working fluids at inlet temperature =55 o c Figure 14: Comparison of Heat transfer rate of different working fluids at inlet temperature =65 o c 5. CONCLUSION The following conclusions were derived from thiswork: Addition of small amount of ZnO nanoparticles into distilled water as the bas fluid would increase the rate of heat transfer, Nusslet number and convection heattransfer coefficient by at least 20.6%, 17.4 %and 22.8 % respectively editor@iaeme.com

10 Volume concentration has a sufficient effect on heat transfer.as the volume loading increases, the thermal conductivity increases, which consequently increases the heat transfer. The heat transfer rate and the convection heat transfer coefficient is significantly affected by the change in nanoparticle volume concentration by an average of 29.3% and 64.1% for each increase in volume loading, respectively. Comparing the three volume concentrations, it can be observed that 2.1% volume loading produces greater increase in rate of heat transfer, Nusslet number and convection heat transfer coefficient. Table (1) enhancement in Nusselt number Vol % JD kg/s Enhancement % Table (2) enhancement in heat transfer coefficient Vol % JD kg/s Enhancement % editor@iaeme.com

11 Using the Nanofluid to Improve the Heat Transfer in the Double Pipe Heat Exchanger Table (3) enhancement in heat transfer rate Vol % JD kg/s Enhancement % REFERENCES [1] S.M.S.Murshed.CLeongC.Yang, Enhanced thermal conductivity of TiO2 water based nanofluids, Volume 44, Issue 4, Pages (2005) [2] M. Chandrasekara, S. Suresha,*, A. Chandra Boseb, Experimental investigations and theoretical determination of thermalconductivity and viscosity of Al2O3/water nanofluid, Nanomaterials Laboratory, National Institute of Technology, Tiruchirappalli , India, Experimental Thermal and Fluid Science(2009). [3] K. Rohini Priya, K.S. Suganthi, K.S. Rajan, Transport properties of ultra-low concentration CuO water nanofluids containing non-spherical nanoparticles, International Journal of Heat and Mass Transfer,p ,(2012) [4] Reza Aghayari,Heydar Maddah,Fatemeh Ashori,Afshin Hakiminejad Mehdi Aghili, Effect of nanoparticles on heat transfer in mini double-pipe heat exchangers in turbulent flow, International journal of science and technology, Article 10, Volume 23, Issue 5, P (2016) [5] Mohammad Hemmat Esfe ; Seyfollah Saedodin; mojtaba biglari; SeyedHadi Rostamian, Thermal conductivity of CuO/EGâ water nanofuid: Experimental investigation and development of new correlations, Journal of modeling in engineering, Article 12, Volume 15, Page Issue 51,(2017) [6] S. Senthilraja and KCK. Vijayakumar, Analysis of Heat Transfer Coefficient of CuO/Water Nanofluid using Double Pipe Heat Exchanger, International Journal of Engineering Research and Technology, Volume 6, Number 5,pp , (2013) [7] Choi S.U.S, Lee S., Li S., Eastman J.A. Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles, Journal of Heat Transfer, vol.121, pp (1999) [8] Wasp, F.J. Solid Liquid Slurry Pipeline Transportation, Trans Tech, Berlin, [9] Timofeeva E.V., Gavrilov A.N., McCloskey J.M., Tolmachev. Y.V., Thermal conductivity and particle agglomeration in alumina nanofluids: experiment and theory, Physical Review 76 pp , (2007) [10] Brinkman H.C., The viscosity of concentrated suspensions and solution, Journal of Chemical Physics 20 pp , (1952) [11] Batchelor G.K. The effect of Brownian motion on the bulk stress in a editor@iaeme.com

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