The enhancement of heat transfer in cooling system of cylindrical lithium-ion battery pack is numerically investigated by installing fins on the cooling plate. Battery Design StudioⓇ software is used for modeling electro-chemical heat generation in the battery and the conjugated heat transfer is analyzed with the commercial package STAR-CCM+. The result shows that installing fins on the cooling plate increases the convective heat transfer on the surface and thus lowers the maximum temperature of the battery pack. As the length and thickness of the fins increase, heat transfer in the battery pack improves. Considering the geometry and airflow of the battery pack, the optimal values for the length and thickness of the fin are both 2mm. As the convective heat transfer coefficient of the surface increases, the maximum temperature of the battery pack is greatly reduced and the temperature gradient is greatly improved.

The improvement of heat transfer in water cooling passage of lithium-ion battery is numerically studied by employing trapezoidal vortex generators. Battery Design StudioⓇ software is used for modeling electro-chemical heat generation in the battery. The conjugated heat transfer is analyzed with the commercial package STAR-CCM+ in terms of inlet flow velocities. The result shows that vortex generator enhances the convective heat transfer by developing thermal boundary layers and secondary flows in downstream, which results in reducing the average temperature of the battery by about 1℃. The heat transfer is enhanced for the whole inlet velocity, while the pressure loss sharply increases at more than inlet velocity of 0.1m/s. The optimum inlet velocity is around 0.1m/s for in terms of the heat transfer and pressure loss.

In the present study, single-phase heat transfer characteristics for downstream flow in the support grid of 6×6 rod bundle were investigated. It has been known that a turbulence generation due to a support grid with split mixing vanes enhances heat transfer in rod bundle but its heat transfer enhancement actually affects to relatively shorter distance. On the other hand, it has been also turned out that a support grid with large scale vortex flow (LSVF) mixing vanes results in heat transfer enhancement to a longer distance. Based on the results of literatre survey, single-phase water heat transfer experiments were performed for Reynolds numbers at around 30,000, and the heat transfer enhancement effect with both i) the split mixing vanes and ii) the LSVF mixing vanes was compared in this study. The key results showed that the effect of heat transfer enhancement in rod bundle region by the split mixing vanes was maintained up to the length of 15Dh behind the spacer grid. For the Reynolds numbers at around 30,000, it was also observed that the effect using the LSVF mixing vanes was stronger at about 3% when compared to the case using the split mixing vanes only for the distance ranging from 1 to 15Dh behind the spacer grid.

In this study, we investigated to the heat transfer performance of coating nano-structure with various shapes and patterns on the heat transfer surface. As a result of the measurement of the 3D nano shape, it was confirmed that the roughness generally increases when the adhesive is sprayed on the coating surface and finished durability experiment. In the case of TEOS adhesive, the roughness increased by 0.074 ㎛, 0.012 ㎛ and 0.015 ㎛, and the contact angle decreased 12.64°, 1.31°, 9.84° at the coating time of 120 seconds, 180 seconds and 240 seconds, respectively. In the case of PVA adhesive, the roughness increased by 0.069 ㎛, 0.056 ㎛ and 0.03 ㎛, and the contact angle decreased 2.85°, 4.82°, 6.96° at the coating time of 120 seconds, 180 seconds and 240 seconds, respectively. In the case of DGEBF adhesive, the roughness increased by 0.042 ㎛, 0.053 ㎛ and 0 ㎛, and the contact angle decreased 0.81° at the coating time of 120 seconds, increased 4.82°, 6.96° at the coating time of 180 seconds and 240 seconds, respectively. As a result, the durability tends to decrease as more nano-structures are deposited, and 3D nano shapes, contact angles and SEM photographs showed that the performance of the PVA adhesive was superior among the three adhesives.

The present experimental study investigates single-phase heat transfer coefficients downstream of support grid in 6×6 rod bundles. Support grid with Split mixing vanes enhance heat transfer in rod bundles by generating turbulence but this turbulence is confined to a short distance. Support grid with large scale vortex flow(LSVF) mixing vanes enhanced heat transfer to a longer distance. In this study, the experiments were performed at reynolds numbers of 50,000. The characteristics of the heat transfer enhancement of the Split mixing vane and those of the LSVF mixing vane were compared. The results showed that the characteristics of the heat transfer enhancement of rods by the Split mixing vane were limited to 10 Dh after the spacer grid, but those by the LSVF mixing vane were maintained until 15 Dh after the spacer grid. For the reynolds number of 50,000, the heat transfer enhancement effect was 3.0% greater when using the LSVF mixing vane than when using the Split mixing vane between the 1 ∼ 15 Dh interval after the spacer grid.

Computational results with pseudoplastic fluid flows for fully developed non-Newtonian laminar flows have been obtained. Those consist of the product of friction factor and Modified Reynolds number and Nusselt numbers with respect to the shear rate parameter in an annular pipe. The numerical results of the product of friction factor and Reynolds numbers and the Nusselt numbers for both Newtonian region and the power law region were compared with previously published asymptotic results, respectively. In the present calculations, the product of friction factor and Newtonian Reynolds numbers for pseudoplastic fluid at power law region in annular pipe is 180% less than that for Newtonian fluid. For power law fluids with different power law flow indices, the difference of the product of friction factor and power law Reynolds number between previous and the present results at the power law region is within 0.20%. The solutions also show the effect of the shear rate parameter on the Nusselt number and about 11% increase of Nusselt number at the power region.

This work studies for boiling and condensation heat transfer performance of trapezoidally shaped integral-fin tubes having fin densities from 748fpm to 1654fpm. For comparison, tests are made using a plain tube having the same inside and outside diameter as that of the root of fins of finned tubes. Hahne's theoretical model and Webb's theoretical model are used to predict the R-11 boiling heat transfer coefficient and condensing heat transfer coefficient respectively for plain tube and all integral-fin tubes. Experiments are carried out using R-11 as working fluid. This work is limited to film-wise condensation and pool boiling on the outside surface of plain tube and 4 low integral-fin tubes. In case of condensation, the refrigerant condenses at saturation state of 32℃ on the outside tube surface cooled by coolant and in case of boiling. the refrigerant evaporates at saturation state of 1bar on the outside tube surface. The amount of non-con-densable gases in the test loop is reduced to a negligible value by repeated purging. The actual boiling and condensing processes occur on the outside tube surfaces. Hence the nature of this surface geometry affects the heat transfer performances of condenser and evaporator in refrigerating system. The condensation heat transfer coefficient of integral-fin tube is enhanced by both extended tube surface area and surface tension. The ratio of the condensation heat transfer coefficients of finned to plain tubes is greater than that of surface area of finned to plain tubes, while ratio of the boiling heat transfer coefficient of finned to plain tubes shows reverse result. As a result, low integral-fin tube can be used in condenser more effectively than used in evaporator.