CFD ANALYSIS OF RADIATORS WITH NANO FLUIDS

Transcription

1 CFD ANALYSIS OF RADIATORS WITH NANO FLUIDS VODNALA VEDA PRAKASH, S.CHAKRADHARA GOUD Research Scholar, Prof. & Principal Shri JJT University Rajasthan, Moghal College of Engineering & Technology, Hyderabad Abstract: Interior Combustion motors in the vehicle applications are winding up exceedingly control pressed with expanding energy to weight and additionally volume proportion. Further, the space accessible under the hat is likewise diminishing because of the regularly expanding interest of little autos by the clients. Nano liquids are another class of warmth exchange liquids designed by scattering nano metre - estimate strong particles in customary warmth exchange liquids. In the present examination a Nano liquid is utilized as a coolant in a radiator show and is dissected for assessing the liquid stream and warmth exchange qualities. A radiator show is displayed in CATIA demonstrating programming and is fit utilizing a pre-preparing programming GAMBIT. Distinctive stream rates are 200 LPH, 300 LPH, 400 LPH, 500 LPH AND 600 LPH. The particular readings for variety in the stream rates were taken and recorded. It is watched that utilization of NF increments convective warmth exchange coefficient up to 41 % and general warmth exchange coefficient up to 21 %. Test esteems are approved with CFD reenactment. Keywords- Aluminum Oxide, Two Step method, Nanofluid, Cross flow heat exchanger, percentage heat transfer enhancement, CFD by fluent 1.0 INTRODUCTION: CFD is a science that can be useful for concentrate liquid stream, warm exchange, substance responses and so forth by comprehending scientific conditions with the assistance of numerical investigation. CFD (Computational liquid flow) utilizes an extremely basic rule of settling the whole framework in little cells or lattices and applying overseeing conditions on these discrete components to discover numerical arrangements with respect to weight conveyance temperature inclinations, stream parameters and so forth in a shorter time at a lower cost as a result of decreased required test work. Car Radiator are ending up profoundly control stuffed with expanding energy to weight or volume proportion. Expanded request on control pressed radiators, which can disperse most extreme measure of warmth for any given space. Nano liquids give higher warmth exchange rate than base liquids. This examination includes CFD reenactment Page 26

2 of the mass stream rate of Nano liquid and warmth exchanger (radiator) at different coolants (Nano liquids). In this paper, CFD used to reenact stream and warmth exchange radiator (warm exchanger). Coolants course through the containers of the radiator, warm is exchanged through tube viders to the air by conduction and convection. The radiator of auto is examined to get warm exchange rate at various volume parts and coolants in this examination. CFD investigation gives precise and correct outcome. Warmth is made when the gas and air blend is touched off in the ignition chamber. This blast makes the cylinder be constrained down inside the motor, levering the associating bars, and turning the crankshaft, making power. Metal temperatures around the burning load can surpass 538 C. With a specific end goal to keep the overheating of the motor oil, chamber dividers, cylinders, valves, and different parts by these outrageous temperatures, it is important to successfully discard the warmth. Roughly 1/3 of the warmth in ignition is changed over into energy to drive the vehicle and its extras. Another 1/3 of the warmth is taken away into the environment through the fumes framework. The rest of the 1/3 must be expelled from the motor by the cooling framework The utilization of nano fluids can possibly enhance the motor cooling rates. These upgrades can be utilized to evacuate motor warmth with a diminished size cooling framework. Littler cooling framework prompts utilization of littler and lighter radiators which thusly will prompt better execution and expanded productivity. 2.0 LITERATURE REVIEW: 1. K. Singh and V. S. Raykar, Microwave synthesis of silver nanofluids with polyvinylpyrrolidone (PVP) and their transport properties, Colloid and Polymer Science, vol. 286, no , pp , Stated that There is the limitation for this method as it requires long term observation. So, centrifugal method came into effect. Singh et al applied this method to observe the stability of silver nanofluids prepared by microwave synthesis in ethanol by reduction of AgNO3 with PVP as stabilizing agent. Results obtained are that nanofluids are stable for more than 1 month in stationary state and more than 10 hour under centrifugation at 3000 rpm without sedimentation. It is because of the use of PVP as it retards the growth and agglomeration of nanoparticles by steric effect. The ways to enhance the stability of nanofluids Surfactants used in nanofluids also known as dispersants. 2. Patel, H. E.; Sundararajan, T. & Das, S. K. (2008). A cell model approach for thermal conductivity of nanofluids A micro-convection model for thermal conductivity of nanofluids. J. Nanopart Res., Vol. 10, No. 1, 87 97, ISSN: investigated the mechanisms of conduction in liquids and conduction through solid nanoparticles and the micro-convective heat transfer to the nanoparticles due to their Brownian motion in the liquid. These investigations show that nanofluids have higher heat transfer relative to conventional fluids and also a better stability compared to fluids with suspended micro particles, making nanofluids useful. Several factors such as gravity, Brownian motion, layering at the solid/liquid interface, ballistic phonon transport between the particles and nanoparticle clusters and the friction between the fluid and the solid particles contributes to the increase in nanofluid heat transfer. With a very small volume fraction of Page 27

3 nanoparticles, thermal conductivity and convective heat transfer capability are enhanced significantly without the problems encountered in common slurries such as clogging, erosion, sedimentation, and large increases in pressure drop. Suspended nanoparticles have higher thermal conductivity than base-fluids, so the effective thermal conductivity of the nanofluids increases. The enhancement of thermal conductivity increases with the solid content i.e. volume fraction in Base fluid, due to the higher number of particles present in the suspension and the higher number of contacts between them. 3. Y. Li, J. Zhou, S. Tung, E. Schneider, and S. Xi, A review on development of nanofluid preparation and characterization, Powder Technology, vol. 196, no. 2, pp , Since today many methods have taken into account for stability but a few has become quite effective. One of the simplest and earliest methods is sedimentation. In this method, the sediment weight or volume of nanoparticles in nanofluids under an external force field is the indication of stability of particular nanofluid & nanofluid as coolants is assumed to be stable when the concentration or particle size of sedimented particle is constant. Zhou used a sedimentation balance method to measure the stability of graphite suspension 4. V. A. M. Selvan, R. B. Anand and M. Udayakumar, J. Eng. Appl. Sci. 4, 1 (2009).taken Cerium oxide nanoparticles were used in base fluid such as diesel and bio-diesel mixture and found the improvement and reduction in the exhaust emission by using a cerium oxide nano particle catalyst. The cerium oxide acted as an oxygen donating catalyst and provides oxygen for the oxidation of CO or absorbs oxygen for the reduction of NOx. 5. K.V. Sharma, L. SyamSundar, P.K. Sarma, Estimation of heat transfer coefficient and friction factor in the transition flow with low volume concentration of Al2O3 nanofluid flowing in a circular tube and with twisted tape insert, International Communications in Heat and Mass Transfer 36 (2009) implemented 12.5 vol.% Al2O3 in water in a horizontal tube geometry and concluded that at (Pe) number of 3500 and 6000 up to 41% promotion in heat transfer coefficient compared to pure water may be occurred. 6. Vasu V, Rama Krishna K, Kumar ACS. Heat transfer with nanofluids for electronic cooling. Int J Mater Prod Technol 2009;34(1/2): studied the thermal design of compact heat exchanger using nanofluids. In this study, it is found that pressure drop of 4% Al2O3 +H2O nanofluids is almost double of the base fluid. 7. W. G. Peng, Y. C. Liu, Y. W. Hu, Y. R. He, Simulation of heat exchange enhancement using in engine cooling system, Harbin institute of technology 43(1) (2011) They showed that compared to water by using TiO2, Al2O3 and CuO nanofluid, the average surface heat transfer coefficient is increased by 10.82%, 8.43% and 11.24%, and correspondingly the pump power is increased only by 1.06%, 1.30% and 1.98%, respectively. 8. R Saidur, K Y Leong & H A Mohammad., (2011), A Review on Applications and challenges of Nanofluids, Renewable and Sustainable Energy Reviews, 15(5), pp , In a study done by Saidur et al (2011) have shown that the use of nanofluids in Page 28

4 radiators can lead to a reduction in the frontal area of the radiator by up to 10%. This reduction in aerodynamic drag can lead to a fuel saving of up to 5%. 3.0 METHODOLOGY: From this analysis radiator, we conclude that Efficiency of radiator increases. Thermal conductivity of the system increases. The addition of nano-particles to the coolant has the potential to improve automotive and heavy-duty engine cooling rates. Also help in a reduced-size cooling system by removing heat from engine. Smaller and lighter radiators, which in turn benefit almost every aspect of vehicle performance and lead to increased fuel economy. Nano fluids will have a greater application in heat transfer problems. These analyses provide strong references to the design of cooling methods, shortened the design period, and reduced the design cost. From the practical point of view it is not costly to add surfactant and adjust the ph for the Nano fluid to gain a very small increase in heat transfer performance of the radiator. To have the same increase in the overall heat transfer coefficient, it would be less costly and more practical to increase the airflow rate. Assumptions in CFD: The physics of conjugate heat transfer in radiator is simplified with the following technically valid assumptions. Velocity and temperature at the entrance of the radiator core for air and coolant is uniform. No phase change occurs in fluid streams. Fluid flow rate is uniformly distributed through the core in each pass on each fluid side. No flow leakages occur in any stream. The flow condition is characterized by the bulk speed at any cross section. The thermal conductivity of the solid material is constant. No internal source exists for thermal-energy generation Properties of the fluids and the wall, such as specific heat, thermal conductivity, and density are only dependent on temperature. Preparation and Estimation of Nano fluid Properties: The idea behind development of nano fluids is to use them as thermo fluids in heat exchangers for enhancement of heat transfer coefficient and thus to minimize the size of heat transfer equipment s. Nano fluids help in conserving heat energy and heat exchanger material. The important parameters which influence the heat transfer characteristics of nano fluids are its properties which include thermal conductivity, viscosity, specific heat and density. The thermo physical properties of nano fluids also depend on operating temperature of nano fluids. Hence, the accurate measurement of temperature dependent properties of nano fluids is essential. Thermo physical properties of nano fluids are pre requisites for estimation of heat transfer coefficient and the Nusselt number. Estimation of Nano particle Volume Concentration The amount of Al2o3 and ZrO2 Nano particles required for preparation of nano fluids is calculated using the law of mixture formula. A sensitive weighing balance with a 0.001mg resolution is used to weigh the Al2o3 and ZrO2 nano particles very accurately. The weight of the nano particles required for preparation of 100 ml Page 29

5 Al2o3 and ZrO2 nano fluid of a particular volume concentration, using water-ethylene glycol base fluid is calculated by using the following relation. Effect on Radiator output temperature: In order to check In order to check the effect of nanofluid on the outlet temperature of the radiator, the figure of radiator outlet temperatures, Tout, as a function of fluid volume flow rate circulating in the radiator. As can be seen, adding nanoparticles to base fluid decreased radiator outlet temperature. It should be said that, for every cooling system, in an equal mass flow rate, the more reduction in working fluid temperature indicated better the thermal performance of the cooling system. Moreover, Figure 4 shows the decrease in cooling rate to increase in the volume flow rate circulating in the radiator. It may be because, increase in volume flow rate caused increase in velocity of the fluid. Therefore, the fluid had less time for connecting with air which comes from the fan and so the outlet temperature increased. It should be noted that all the data in Figure were obtained when the fluid inlet temperature of the radiator was 90 CFD analysis with NANO fluids for radiators Modelling 2D model of radiator 3D model of radiator BOUNDARY CONDITIONS AND PHYSICS SELECTED One of the most important operations of the fluid flow analysis of the radiator heat transfer is applying the boundary conditions to the geometric parts of the radiators. The conservation equations of mass, momentum, and energy are nonlinear and coupled systems, which are solved subjected to the following boundary conditions. At the inlet of the radiator properties of Nano Page 30

6 fluid such as Thermal conductivity, density, specific heat, viscosity is prescribed. The inlet temperature and mass flow rate of the radiator have been taken as 353 K and 2 kg/s which is typical for automotive radiators. The mass flow rate at the inlet assumed in the present study is an idealization of the actual flow pattern because considerable flow non uniformities arising from the fluid entering the top of the radiator will be inevitable in the actual case. In Fluent the outflow boundary condition corresponds to fully developed mass flow rate and temperature profiles. For an automobile radiator, a realistic thermal boundary condition on the outside of the wall is a prescribed free stream temperature. 4.0 RESULTS AND ANALYSIS: Simulation analysis of the car radiator done for 0.3 volumetric flow rate. After adding the Nano fluids to the base fluid enhanced heat transfer results are shown. In following heat transfer contours analysis results are given for 0.2 of Nano fluids at Mass flow rate kg/s and temperature at 353k we simulate Nano fluids with base fluid with 0.2 concentrations. The simulation results for each Nano fluid have been observed. Meshed Model of Radiator Heat transfer co efficient of contour of the Aluminum oxide Page 31

7 Velocity Distribution velocity contour for radiator at 0.43 kg/sec mass flow rate Temperature Distributions temperature contour for radiator at 0.43 kg/sec mass flow rate Loss in temperature of coolant with nanofluid and water Page 32

8 Temperature distribution Temperature distribution of aluminum made radiator Heat flux Heat flux of aluminum radiator temperature and the heat flux for Aluminum radiator. The maximum temp and het flux was observed at Page 33

9 Variation In Thermal Conductivity With Mass Flowrates Simulation results of the of the tempreature and the velocity are shown for the 2, 3, 4, 5. % of the nano fluids for volume flowrate of the 5 litter per minute. These simulation results made to compare with the simulation values of the plain water and with that enhanced heat transfer values will get. Simulation results are obtained with four paranetes like Heatransfer Mass flow rate and Temperature and the velocity componants from thses parameters its easy to analysis the nanofluids effectively. Overal Heat Transfer Co-efficient for different % Nano fluids : Increase in Overall Heat Transfer coefficient with % of Nano fluids Thermal conductivity Page 34

10 Overall Heat Transfer Co-efficient with Temperature As seen figure Increase in the overall heat transfer co-efficient the characteristic curve show that increase with % of nano fluids. And in the figure 4.4 when % of the nano fluid increases in X- axis to that the thermal conductivity of the fluid also increases simultaneously. And figure 4.5 Increase in the heat transfer co efficient with temperature Hence from this we can conclude that from our project by using the nano fluids to the base fluid for any coolant that will enhance the thermal conductivity of the fluid and also heat carrying capacity of fluid. 5.0 Conclusions: From this analysis radiator, we conclude that Efficiency of radiator increases. Thermal conductivity of the system increases. The addition of nano-particles to the coolant has the potential to improve automotive and heavy-duty engine cooling rates. Also help in a reduced-size cooling system by removing heat from engine. Smaller and lighter radiators, which in turn benefit almost every aspect of vehicle performance and lead to increased fuel economy. Nano fluids will have a greater application in heat transfer problems. These analyses provide strong references to the design of cooling methods, shortened the design period, and reduced the design cost. From the practical point of view it is not costly to add surfactant and adjust the ph for the nano fluid to gain a very small increase in heat transfer performance of the radiator. To have the Page 35

11 same increase in the overall heat transfer coefficient, it would be less costly and more practical to increase the airflow rate. References: 1. W. G. Peng, Y. C. Liu, Y. W. Hu, Y. R. He, Simulation of heat exchange enhancement using in engine cooling system, Harbin institute of technology 43(1) (2011) Glezer, A., and R. Mahalingam (2003). System and method for thermal management by synthetic jet ejector channel cooling techniques, U.S. patent 6,588, Keblinst P, Eastman J.A. and Chaill D.G. Nanofluids for thermal transport. Material Today 8 (2005), 6: pp Tzeng, S.-C., C.-W. Lin, and K. D. Huang (2005). Heat transfer enhancement of nanofluids in rotary blade coupling of four-wheel-drive vehicles, Acta Mech., 179: Liu M-S, Lin MC-C, Tsai CY, Wang C-C. Enhancement of thermal conductivity with Cu for nanofluids using chemical reduction method. Int J Heat Mass Transfer 2006;49(17 18): , International Journal of Thermal Sciences, Volume 66, April 2013, Pages Assael, M. J.; Metaxa, I. N.; Kakosimos,K. & Constantinou, D. (2006). Thermal Conductivity of Nanofluids-Experimental and Theoretical, International Journal of Thermophysics, Vol.27, No.4, (July 2006) , ISSN: X 7. Ollivier E, Bellettre J, Tazerout M, Roy GC. Detection of knock occurrence in a gas SI engine from a heat transfer analysis. Energy Convers Manage 2006;47(7 8): M. J. Kao, C. H. Lo, T. T. Tsung, Y. Y. Wu, C. S. Jwo, and H.M. Lin, Copper-oxide brake nanofluid manufactured using arc submerged nanoparticle synthesis system, Journal of Alloys and Compounds, vol , pp , Page 36