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  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 164 THERMAL PERFORMANCE AND FLOW ANALYSIS OF NANOFLUIDS IN A SHELL AND TUBE HEAT EXCHANGER S. Bhanuteja1 , D.Azad2 1 (P.G Student, Department of Mechanical Engineering, AITAM, Tekkali) 2 (Associate professor, Department of Mechanical Engineering, AITAM, Tekkali) ABSTRACT This paper reports the thermal performance of a Counter-flow Shell and Tube Heat exchanger using nano fluids as the working fluids. Finite volume Method was used to solve the three- dimensional steady, turbulent developing flow and conjugate heat transfer in a Shell and tube heat exchanger. The nano fluids used were Ag, Al2O3, CuO, SiO2, and TiO2 and the performance was compared with water. The thermal performance and flow of the Shell and tube heat exchanger was analyzed using different nanofluids. Temperature profile, heat transfer coefficient, pressure profile, was obtained from the simulations. The results are evaluated in terms of effectiveness, heat transfer rate, and Overall heat transfer coefficient. Keywords: Heat exchanger, Heat transfer enhancement, Nanoparticle, Nanofluids, pressure drop. I. INTRODUCTION The two factors that limit the heat transfer coefficient are reductions in channel dimensions were accompanied by higher pressure drop; and the amount of heat transfer was limited by the heat transfer fluids used. Traditional transfer fluids used in heat exchangers are mainly water, ethylene- glycol and oil. The heat transfer performance of the traditional fluids is low; this causes heat transfer enhancement efficiency to be lower. In order to enhance the thermal conductivity of the traditional fluid and heat transfer characteristics, the solid particles are suspended into the base fluid used in the heat exchangers. Adding particles into the base fluid enhances the thermal conductivity, because the thermal conductivity of the solid metal particles is higher than the base fluid. H.A. Mohammeda et al. [1] tested the new heat transfer fluids engineered by dispersing nano particles having smaller diameter than 100 nm into the base fluid are called as nano fluid. Using nano fluids in heat exchange systems enhances thermal conductivity. Heat transfer coefficient increases by the increase of the thermal conductivity. Farajollahi et al. [2] performed an experimental analysis to study heat transfer of nanofluids in a shell and tube heat exchanger. The nanofluids used were Al2O3/water and INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 4, Issue 5, September - October (2013), pp. 164-172 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2013): 5.7731 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 165 TiO2/water under turbulent flow conditions to investigate the effects of Peclet number, volume concentration of suspended particles, and particle type on the heat transfer characteristics. The results indicate that addition of nanoparticles to the base fluid enhances the heat transfer performance and results in larger heat transfer coefficient than that of the base fluid at the same Peclet number. Mapa and Mazhar [3]. tested the effect of nanofluids in mini heat exchanger. Their experiments tested the heat transfer performance in the heat exchanger using water/water as working fluids, and using water and nanofluid with concentration of 0.01% and 0.02% volume. They concluded that nanofluids enhance the heat transfer rate, and stated that the presence of nanoparticles reduced the thermal boundary layer thickness. Several other researchers have reported similar trend in the increase of heat transfer in conventional fluids by the addition of nanoparticles. For example, Masuda et al. [4] and Xuan and Li [5] stated that with low nanoparticle concentrations (1–5% volume), the thermal conductivity of the suspensions can increase by more than 20%. Since Choi et al. [6] reported that the addition of a small amount (less than 1% volume) of nanoparticles to traditional heat transfer liquid approximately doubled the thermal conductivity of the fluid, the frenzy into nanofluids research for heat transfer applications is started. II. OBJECTIVES OF THE PRESENT WORK The present work begins with the thermal performance analysis of a shell and tube heat exchanger. For this we have chosen an existing 2 ton capacity of counter flow shell and tube heat exchanger and is modeled. By the flow field analysis, the performance of shell and tube heat exchanger is done with nano fluids and was compared with water. In this R22 is used as a primary refrigerant (hot fluid) and water based nanofluids used were Ag, Al2O3, CuO, SiO2, and TiO2 (cold fluids). Analysis through computer predictions costs less than laboratory or field experiments and provides higher level of confidence. In the light of above discussion, the present work has been taken up aiming at achieving the following objectives. • To perform thermal analysis on a shell and tube heat exchanger using ANSYS 12, after modeling the heat exchanger. • To observe the effect on temperature rise and pressure drop along the length of tube and shell. • To study the heat transfer enhancement capabilities of coolant. 1. Geometric modeling The geometric modeling of shell and tube heat exchanger was made. The heat exchanger specifications are listed in Table1. The 3D meshed geometry of circular type shell and tube heat exchanger is shown in fig1. Fig 1: Meshing of Geometry
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 166 Table 1. Specifications of a Heat exchanger 1 Shell outer diameter 100mm 2 Shell thickness 10mm 3 Length of the shell 150mm 4 Shell material Stainless steel 5 Tube outer diameter 20mm 6 Tube thickness 1mm 7 Tube material Copper 8 Type of tube layout Circular layout 9 Type of tube arrangement Inline arrangement 10 No of tubes inside the shell 6 2. Properties of the working fluid The model which has been developed is taken for further analysis. Here R22 is used as a refrigerant (Hot fluid) and the nano fluids (cold fluids) used were Ag, Al2O3, CuO, SiO2, and TiO2. Required Properties are shown in Table 2. The thermo physical properties of required nanofluids at different volumetric concentrations are calculated using the following equations. Density: ߩ௡௙ ൌ ሺ1 െ Øሻߩ௕௙ ൅ ‫ߩ׎‬௣ Heat capacity: ሺߩܿ௣ሻ௡௙ ൌ ሺ1 െ ‫׎‬ሻ൫ߩܿ௣൯௕௙ ൅ ‫׎‬ሺ൫ߩܿ௣൯௣ Thermal conductivity: ݇௡௙ ൌ ௞೛ାଶ௞್೑ାଶሺ௞೛ି௞್೑ሻØ ௞೛ାଶ௞್೑ିሺ௞೛ି௞್೑ሻØ Viscosity: ߤ௡௙ ൌ ߤ௕௙ሺ1 ൅ 2.5‫׎‬ሻ Where Ø is particle volume fraction, the subscript “nf” refers to nanofluid, “bf” refers to base fluid, and “p” refers to particle. Table 2. Thermo physical properties of Nano fluids at volume fraction of 2% 3. Data collection and analysis The shell side fluid temperature is taken as 54.40C and for tube is 23.30C. Inlet mass flow rate is 0.1584 kg/ sec. For the same inlet conditions the performance of the Shell and tube heat exchanger was analyzed using different nanofluids and was compared with water. Nano fluids Density (kg/m3) Heat capacity ( J/kg K) Viscosity (N s/m3) Thermal conductivity ( W/m K) H2O 998.2 4182 0.001003 0.613 Ag–H2O 1188.236 3484.436 0.00105315 0.650366928 Al2O3–H2O 1057.636 3925.475 0.00105315 0.648823843 CuO– H2O 1108.236 3754.264 0.00105315 0.647218493 SiO2– H2O 1022.236 4032.254 0.00105315 0.621942641 TiO2– H2O 1063.236 3902.529 0.00105315 0.643637682
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 167 4. Calculations • The general relation for heat transfer is as follows: Q = m Cp (To−Ti) --------------- (1) • The heat removed from the hot fluid, Qh, and the heat absorbed by the cooling liquid, Qc, are calculated by the following equations. ܳ ൌ ܳܿ ൌ ݉ܿ‫ܿ݌ܥ‬ሺ∆ܶܿሻ ---------------- (2) ܳ ൌ ݄ܳ ൌ ݄݉‫݄݌ܥ‬ሺ∆݄ܶሻ ---------------- (3) • The total heat transfer coefficient is defined as: ܷ ൌ ொ ஺.௅ெ்஽ ----------------- (4) ‫ܦܶܯܮ‬ ൌ ்೓೚ି்೎೔ି்೓೔ି்೎೚ ூ௡ ೅೓೚ష೅೎೔ ೅೓೔ష೅೎೔ ----------------- (5) • Effectiveness (ε) Under ideal condition, using the value of actual heat transfer rate (q) from the energy conservation equation, the effectiveness valid for all flow arrangement of the two fluids is given by εଵ ൌ ்೓,೔ି்೓,೚ ்೓,೔ି்೎,೔ ----------------- (6) εଶ ൌ ்೎,೚ି்೎,೔ ்೓,೔ି்೎,೔ ----------------- (7) II. RESULTS AND DISCUSSION The analysis has been carried out with R22 is used as a primary refrigerant (hot fluid) and water based nanofluids used were Ag, Al2O3, CuO, SiO2, and TiO2 as cold fluids. During each analysis for the same inlet conditions the temperatures of both hot and cold streams were recorded. From that data the heat transfer rates, overall heat transfer coefficient, effectiveness and pressure drop can be calculated. 1. Thermal field analysis of the Shell and Tube Heat exchanger This section discusses the effects on the temperature profile of the Shell and Tube Heat exchanger, heat transfer coefficient, and heat transfer rate for various nanofluids. The effect of various nanofluids on the dimensionless temperature profile of the Shell and Tube Heat exchanger is shown in below fig. The nanoparticle concentration used in this case is 2%. It can be observed that the overall bulk temperature of the nanofluids (cold fluid) is higher than of water. This is an indication of higher amount of heat received by the nanofluids compared to water, thus raising the overall bulk temperature of the fluids. The temperature contour obtained from analysis is shown below in fig2. From analysis the outlet temperatures of various nano fluids are recorded, and are listed in Table 3. The temperature rise along tube length for tested fluids is plotted in fig 3. Fig3. indicates that among the nanofluids tested, Ag obtained the highest overall bulk temperature, followed by CuO, TiO2, Al2O3, SiO2, and finally water.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 168 Fig2. Temperature contour of a circular tube heat exchanger Table 3. Outlet Temperatures of various nano fluids along tube length of a shell and tube heat exchanger Fig3. Temperatures of nanofluids along tube length The heat transfer rate along tube length is calculated using equation (1), for various nano fluids, and is listed in Table 4. Fig 4. Heat rate comparison among nanofluids tube length in mm Water Ag-H2O Al2O3- H2O CuO- H2O SiO2- H2O TiO2- H2o temp in k temp in k temp in k temp in k temp in k temp in k 0 296.4 296.4 296.4 296.4 296.4 296.4 50 301 302.7 301.3 301.7 301.3 301.3 100 303 304.7 303.8 304.3 303.7 303.7 150 304.6 306.3 305 305.6 306.5 305
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 169 Table 4. Heat rate(J/sec) of various nano fluids along tube length of a shell and tube heat exchanger Finally by increasing the thermal conductivity of cold fluid heat transfer rate is increased. Fig 4. Shows water has high heat transfer rate because of its high specific heat as 5431.92 J/sec. Among the nanofluids tested heat transfer rate increases to 6450.96 J/sec by SiO2 followed by, CuO, water, Al2O3, TiO2, and Ag. The Overall heat transfer coefficient along length of the shell is calculated using equation (4). Calculated values are shown in Table 5. Fig 5. Overall heat transfer coefficient of nanofluids Table 5. Overall heat transfer coefficient (W/mm2K) of various nano fluids along length of the shell The overall heat transfer coefficient is influenced by the thickness and thermal conductivity of the mediums through which heat is transferred. The larger the coefficient, the easier heat is transferred. Fig 5. Depicts that SiO2 nanofluid has the highest value followed by, CuO, Al2O3, TiO2, Ag, and finally water. 2. Flow field analysis of a shell and tube heat exchanger This section analyses the effects of various nano fluids on the pressure drop profile. Changes in pressure drop along tube length are shown in Table 6. tube length in mm Water Ag-H2O Al2O3- H2O CuO- H2O SiO2- H2O TiO2- H2o 0 0 0 0 0 0 0 50 3047.17 2925.25 3046.8 3746.45 3129.67 3028.98 100 4372.03 4360.28 4601.28 4935.81 4662.57 4512.57 150 5431.91 5077.79 5347.43 5887.29 6450.96 5316.18 tube length (mm) Water Ag- H2O Al2O3- H2O CuO- H2O SiO2- H2O TiO2- H2O 0 0 0 0 0 0 0 50 0.00233 0.00232 0.00236 0.00306 0.00242 0.00235 100 0.00354 0.00382 0.00389 0.00435 0.00392 0.00381 150 0.00464 0.00469 0.00473 0.00553 0.00602 0.00471
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 170 Fig 6. Pressure drop profile of Heat exchanger using different nanofluids Table 6. Pressure values of nano fluids along tube length Pressure drop( Pa) comparison Length (mm) 0 50 100 150 H2O 101370.172 101356.625 101334.047 101325.016 Al2O3 101369.578 101356.211 101338.383 101325.016 Ag 101364.68 101352.781 101338.3 101325.008 CuO 101367.539 101354.781 101337.773 101325.016 SiO2 101369.539 101356.823 101337.734 101325.007 TiO2 101369.359 101356.055 101338.313 101325.008 Fig 6. Indicates that among the nanofluids tested, SiO2 nanofluid has the highest pressure drop, followed by Al2O3, TiO2, water, CuO and finally Ag. The performance of the Shell and tube heat exchanger is presented in terms of effectiveness. Effectiveness of cold fluid is calculated using equation (7), and the values are listed in Table 7. Fig 7. Effectiveness of various nano fluids
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 171 Table 7. Effectiveness of cold fluid along tube length Fig 7. Results that Ag nanofluid has the highest effectiveness value followed by CuO, SiO2, TiO2, Al2O3, and finally water. III. CONCLUSIONS The analysis was completed by increasing the thermal conductivity of cold fluid. Here an approach has been taken to make comparative study of heat transfer between the R22 refrigerant and various nanofluids. Based on the results obtained from the analysis the following conclusions have been drawn out. a) Among the nanofluids tested, Ag obtained the highest overall bulk temperature, followed by CuO, TiO2, Al2O3, SiO2, and finally water. b) By increasing the thermal conductivity of cold fluid heat transfer rate is increased. Water has high heat transfer rate because of its high specific heat as 5431.92 J/sec. Among the nanofluids tested heat transfer rate increases to 6450.96 J/sec by SiO2 followed by, CuO, water, Al2O3, TiO2, Ag. c) The overall heat transfer coefficient is influenced by the thickness and thermal conductivity of the mediums through which heat is transferred. The larger the coefficient, the easier heat is transferred. SiO2 nanofluid has the highest value followed by, CuO, Al2O3, TiO2, Ag, and finally water. d) Among the fluids tested, SiO2 nanofluid has the highest pressure drop, followed by Al2O3, TiO2, water, CuO and finally Ag. Water did not obtain the lowest pressure drop in this case due to higher average velocity it had compared with CuO and Ag along the channel length. e) Results indicated that Ag nanofluid has the highest value followed by, CuO, SiO2, TiO2, Al2O3, and finally water. REFERENCES [1] H.A. Mohammeda,, G. Bhaskaran a, N.H. Shuaib a, R. Saidur Numerical study of heat transfer enhancement of counter nanofluids flow in rectangular micro channel heat exchanger 28 June 201. [2] B. Farajollahi, S.Gh. Etemad, M. Hojjat, Heat transfer of nanofluids in a shell and tube heat exchanger, Int. J. Heat Mass Transfer 53 (2010) 12–17. [3] L.B. Mapa, S. Mazhar, Heat transfer in mini heat exchanger using nanofluids, Sectional Conference, American Society for Engineering Education, Illinois, 2005. tube length (mm) Water Ag-H2O Al2O3- H2O CuO- H2O SiO2- H2O TiO2- H2O 0 0 0 0 0 0 0 50 0.14465 0.19811 0.15408 0.16666 0.154088 0.15408 100 0.20754 0.26100 0.23270 0.24842 0.22956 0.22956 150 0.25786 0.31132 0.27044 0.28930 0.31761 0.31761
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 5, September - October (2013) © IAEME 172 [4] S.U.S. Choi, Z.G. Zhang, W. Yu, F.E. Lockwood, E.A. Grulke, Anomalously thermal conductivity enhancement in nanotube suspensions, Appl. Phys. Lett. 79 (2001) 2252–2254. [5] H. Masuda, A. Ebata, K. Teramae, N. Hishinuma, Alteration of thermal conductivity and viscosity of liquid by dispersing ultra-fine particles (Dispersion of g-Al2O3, SiO2, and TiO2 ultra-fine particles), Netsu Bussei. 7 (1993) 227–233. [6] S.U.S. Choi, Z.G. Zhang, W. Yu, F.E. Lockwood, E.A. Grulke, Anomalously thermal conductivity enhancement in nanotube suspensions, Appl. Phys. Lett. 79 (2001) 2252–2254. [7] D.B. Tuckerman, R.F.W. Peace, High-performance heat sinking for VLSI, IEEE Electron. Devices Lett. 2 (1981) 126–129. [8] M.I. Hasan, A.A. Rageba, M. Yaghoubib, H. Homayoni, Influence of channel geometry on the performance of a counter flow microchannel heat exchanger, Int. J. Therm. Sci. 48 (2009) 1607–1618. [9] Y. Yener, S. Kakac, M. Avelino, T. Okutucu, Single-phase forced convection in micro channels: a state-of-the-art review, Microscale Heat Transfer (2005) 1–24. [10] M.A. Al-Nimr, M. Muqableh, A.F. Khadrawi, S.A. Ammourah, Fully developed thermal behaviors for parallel flow micro channel heat exchanger, Int. Commun. Heat Mass Transfer 36 (2009) 385–390. [11] T. Bayraktar, S.B. Pidugu, Review: characterization of liquid flows in micro fluidic systems, Int. J. Heat Mass Transfer 49 (2006) 815–824. [12] X. Lu, A.G.A. Nnanna, Experimental study of fluid flow in micro channel, Proceedings of the ASME Int. Mechanical Engineering Congress and Exposition, IMECE (2008) Paper No. 67932. [13] M. Senta, A.G.A. Nnanna, Design of Manifold for Nanofluid Flow in Micro channels, Proceedings of the ASME Int. Mechanical Engineering Congress and Exposition, IMECE (2007) Paper No. 42720, pp. 1–8. [14] T. Dang, J. Teng, J. Chu, A study on the simulation and experiment of a micro channel counter-flow heat exchanger, Appl.Therm. Eng. 30 (2010) 2163–2172. [15] S.W. Kang, S.C. Tseng, Analysis of effectiveness and pressure drop in micro cross flow heat exchanger, Appl. Therm. Eng. 27 (2007) 877–885. [16] J.C. Maxwell, A Treatise on Electricity and Magnetism, Clarendron Press, UK, 1873. [17] M. Necatiozisik, Heat Transfer- A basic approach. McGraw-Hill, International editions,pp.524-566. [18] J.P. Holman, Heat transfer, McGraw-Hill, edition 2009. [19] Sunil Jamra, Pravin Kumar Singh and Pankaj Dubey, “Experimental Analysis of Heat Transfer Enhancement in Circular Double Tube Heat Exchanger Using Inserts”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 306 - 314, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [20] Prof.Alpesh V Mehta, Nimit M Patel, Dinesh K Tantia and Nilsh M Jha, “Mini Heat Exchanger using Al2o3-Water Based Nano Fluid”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 2, 2012, pp. 238 - 244, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [21] Kavitha T, Rajendran A, Durairajan A and Shanmugam A, “Heat Transfer Enhancement using Nano Fluids and Innovative Methods - An Overview”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 769 - 782, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.