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This article experimentally investigates the heat generation characteristics and the effectiveness of passive cooling of commercially available LiFePO 4 (7.25 mm × 160 mm × 227 mm, 19.5 Ah) cells using different cooling materials. The specific heat capacity and the entropy coefficient of the cell are experimentally measured. The heat generation rate of the cell at 1-4 C current rates are also determined using three different methods: (1) the heat absorption calculated from the temperature increase of cooling water; (2) the energy loss calculated from the difference between the operating voltage and open circuit voltage; and (3) the energy loss during a charge-discharge cycle calculated using the voltage difference between charging and discharging. Results show that the heat generation rate estimated from heat absorbed by the water can be underestimated by up to 47.8% because of the temperature gradient within the cell and on the surface. The effectiveness of different passive cooling materials is compared at discharge current rates of 1-3 C. The average increase of the cell surface temperature is 22.6, 17.1, 7.7, 7.2 and 6.4 • C at 3 C (58.5 A) using air, aluminum foam, octadecane, water with aluminum foam and water, respectively.

Entropy generation of an Al 2 O 3 -water nanofluid due to heat transfer and fluid friction irreversibility has been investigated in a square cavity subject to different sidewall temperatures using a nanofluid for natural convection flow. This study has been carried out for the pertinent parameters in the following ranges: Rayleigh number between 10 4 and 10 7 and volume fraction between 0 and 0.05. Based on the obtained dimensionless velocity and temperature values, the distributions of local entropy generation, average entropy generation, and average Bejan number are determined. The results are compared for a pure fluid and a nanofluid. It is totally found that the heat transfer, and entropy generation of the nanofluid is more than the pure fluid and minimum entropy generation and Nusselt number occur in the pure fluid at any Rayleigh number. Results depict that the addition of nanoparticles to the pure fluid has more effect on the entropy generation as the Rayleigh number goes up. C⃝ 2014 Wiley Periodicals, Inc. Heat Trans Asian Res, 00(00): 1-16, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj).

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Enhancement of buoyancy-driven convection heat transfer within vertical cavities containing nanofluids subjected to different side wall temperatures and various aspect ratios is investigated. The computations are based on an iterative, finitevolume numerical procedure (SIMPLE) that incorporates the Boussinesq approximation to simulate the buoyancy term. With the base fluid being water, three different nanoparticles (Cu, TiO 2 , and Al 2 O 3) are considered as the nanofluids. This study has been carried out for the pertinent parameters in the following ranges: the Rayleigh number, Ra f = 10 5-10 7 and the volumetric fraction of nanoparticle between 0 and 5 percent. The results are presented for different length-to-height ratios varying from 0.1 to 1.0. The comparisons show that the mean Nusselt numbers and velocity magnitudes increase with volume fraction for the whole range of the Rayleigh numbers. The predictions show a noticeable heat transfer enhancement compared to pure fluid. It is also found that the heat transfer enhancement utilizing nanofluid is more pronounced at low aspect ratios than high aspect ratios. Moreover, the results depict that the addition of nanoparticles to the pure fluid has more effects at lower Rayleigh numbers.

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