Journal of Selected Topics in Energy

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In this study, heat transfer coefficient and the bubble diameter during pool boiling of pure water, pure ethanol and water-ethanol solutions on a horizontal tube in an atmospheric pressure is examined. Experiments are accomplished for different mole fraction of ethanol in water and in heat flux of 5-103   .The results reveal that heat transfer coefficient increases by increasing heat flux for pure water and pure ethanol and the combination of these two liquids. The heat transfer coefficient in the solution except for ethanol molar concentration of 0.04 is less than those in single component substances at the same heat flux. Also the heat transfer coefficient for azeotrope molar concentration y an error about 6% is almost equal to ideal heat transfer coefficient. Finally, the results are analyzed by Genetic Algorithm and a new model is presented to calculate the heat transfer coefficient of the water-ethanol solution.

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Because of increasing demand on new reliable power source for hybrid electric vehicles, lithium-ion (Li-ion) batteries have received much attention in the last decade. Problem free Li-ion batteries are already in use for low power demand applications such as cell phone and laptop battery packs, however; for high power applications such as in automotive propulsion drives, there are serious issues which need to be addressed. Among various issues that high power application lithium-ion (Li-ion) batteries are encountered, thermal issues have received more attention because of their potential to degrade battery performance. In this work, a lumped capacitance heat transfer model is developed in conjunction with a flow network approach to study performance of a commercial-size Lithium-ion battery pack, under various design and operating conditions of a thermal management system. Air, silicon oil and water are chosen as cooling media in the battery pack. Different flow configurations are considered and temperature dispersion, cell-averaged voltage and resistance distributions, and parasitic losses due to the fan/pump power demand are calculated. It is found that application of a coolant with an appropriate viscosity and heat capacity, such as water, in conjunction with a Y-type flow configuration will result in uniform temperature and voltage distributions in the battery pack while keeping the power requirement at low, acceptable levels.

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In this study, the effect of adding polyisobutylene (PIB) as drag reducing agent (DRA) and nanoSiO₂ particles as heat transfer enhancer to crude oil, separately and also the simultaneous addition of these materials to crude oil as poly-nanofluids (PNFs) in a vertical pipe and under constant heat flux conditions is investigated. The use of drag reducers is one of the most important and simplest methods to overcome some of the energy losses during fluid transpotation. The aim of this study is to investigate the effects of PIB solution and crude oil/silica nanofluid, separately and also the simultaneous effect of adding these two materials, called polyanofluid, on heat transfer and drag reduction in a vertical pipe. In order to make PNFs, polymer-based solutions with concentrations of 10-30 ppm are prepared. Then, nanoSiO₂ with concentrations of 0.1-0.5wt% are added to the base fluid. The experiments were performed in the range of Reynolds 5800-8700 and temperature was 25°C. Experimental conclusions predicted that with increasing Reynolds number, temperature and concentration, Nusslet number and heat transfer rate in supplied nanofluids and PNFs enhanced with nanoparticle concentrations, while PIB concentration cause to reduce thermal propertied and improve the tribological properties of prepared PNFs. This occurrence can be attributed to the formation of the polymeric layer around the nanosilica particles.

 

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 Heat transfer has an effective role in industrial and engineering applications. In this study, the effect of Al₂O₃ nanoparticles on laminar forced convection heat transfer flow in a tube is studied. Governing Equations are discretized using the finite difference method on a staggered grid. Nanofluid flow is simulated using single-phase and mixture models. Simulation results show that the average Nusselt Number increases with an increase in the Reynolds Number. Also, by increasing the volume fraction, the average Nusselt number and consequently the heat transfer rate increases. The results of the mixture model are in better agreement with experimental results than the single-phase model.