• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.417-427
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• 1998

The effect of secondary flow on the heat transfer of a turbulent wake generated by a flat plate was experimentally investigated. The secondary flow was induced in a curved duct in which the flat plate wake generator was installed. All three components of turbulent heat flux were measured in the plane containing the mean radius of curvature of the curved duct. The results showed that mean temperature profiles deviate from the similarity of the straight wake because of the cold fluid transported from the free-stream. The half-width of the mean temperature profile increased rapidly by upwash motion of the secondary flow. The changes to turbulence structure caused by the secondary flow show more pronounced effect on heat transport than on momentum transport. This is because the response to the variation of flow conditions is delayed in temperature field. Negative production of the turbulent heat flux is observed in the inner wake region. From the conditional averaging, it has been found that the negative production of the turbulent heat flux is generated due to a mixing process between the hot and low momentum eddies occupied in the inner wake region and the cold and high momentum eddies in the potential region.

• Solar Energy
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• v.18 no.3
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• pp.63-69
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• 1998

The heat conduction and the water vapour diffusion flow through heat insulators between hygroscopical moist building materials were measured by means of the plate method. It was found that the heat transport increases with a moisture motion occuring in the temperature drop. On his basis of simplified assumptions, the increase in the thermal conductivity was calculated from the rate of diffusion flow per unit area, which generally resulted in values inferior to the measured values. The Increase in the heat transport due to water vapour diffusion measured at a large-scale wall specimen was inferior to the one measured by means of the plate method by using a comparable arrangement of layers. The overall heat transfer caused by moisture motion is not a characteristic value of the material, but a property of the whole wall structure

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1782-1798
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• 2004

A numerical study of a natural convection in a rectangular cavity with the low-Reynolds-number differential stress and flux model is presented. The primary emphasis of the study is placed on the investigation of the accuracy and numerical stability of the low-Reynolds-number differential stress and flux model for a natural convection problem. The turbulence model considered in the study is that developed by Peeters and Henkes (1992) and further refined by Dol and Hanjalic (2001), and this model is applied to the prediction of a natural convection in a rectangular cavity together with the two-layer model, the shear stress transport model and the time-scale bound ν$^2$- f model, all with an algebraic heat flux model. The computed results are compared with the experimental data commonly used for the validation of the turbulence models. It is shown that the low-Reynolds-number differential stress and flux model predicts well the mean velocity and temperature, the vertical velocity fluctuation, the Reynolds shear stress, the horizontal turbulent heat flux, the local Nusselt number and the wall shear stress, but slightly under-predicts the vertical turbulent heat flux. The performance of the ν$^2$- f model is comparable to that of the low-Reynolds-number differential stress and flux model except for the over-prediction of the horizontal turbulent heat flux. The two-layer model predicts poorly the mean vertical velocity component and under-predicts the wall shear stress and the local Nusselt number. The shear stress transport model predicts well the mean velocity, but the general performance of the shear stress transport model is nearly the same as that of the two-layer model, under-predicting the local Nusselt number and the turbulent quantities.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.461-471
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• 2016

Numerical modules based on a conventional thermo-hydrological numerical model, TOUGH2, are developed to provide a numerical modeling technique for a standing column well (SCW). Cooling and heating operations for two different types of SCW are then simulated using these modules. Modeling showed these operations to be significantly influenced by heat exchange and fluid mixing between the SCW and the adjacent geologic formation and groundwater. The results also reveal that heat exchange between the oppositely flowing outflow and inflow in the PVC or PE pipe and the SCW borehole is an important factor. Overall, the numerical modeling technique developed here can reasonably simulate fluid flow and heat transport phenomena in the complex internal structures of a SCW. The proposed technique can be used practically for the quantitative analysis of heat exchange in a SCW at the design, construction, and operation stages.

• Journal of Aerospace System Engineering
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• v.14 no.1
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• pp.8-15
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• 2020

In this paper, we propose a container wall and its boundary layer insulation design method that can maintain the temperature inside the spacecraft shipping container constantly under the condition that the heat or the external temperature changes severely to safely transport the satellite to the launch site. We will examine if the temperature inside the satellite shipping container is kept constant through the heat flow analysis and the satellite heat transfer analysis for the external environment of the satellite shipping container. Through the flow analysis inside the container, the flow distribution around the satellite in the container is analyzed, and the auxiliary fan, air conditioning system and special grill guide structure design for improving and optimizing heat flow performance are proposed.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.1
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• pp.50-61
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• 2000

The effects of an inserted coil on flow . patterns and heat transfer performance for a horizontal rotating heat pipe have been studied experimentally. Especially, the present study is to see an internally inserted helical coil inside a RHP would lead to the same kind of results as internal fins. Visualization test conducted for an acryl tube, charged water with at a volumetric rate of 20%. When the flow kept pool regime at a low rpm(less than 1,000rpm), the movement of coil forced the water to flow in axial direction. But this pumping effect of coil disappeared, when the pool regime changed to annular one which could be created by increasing rpm. The pumping effects for RHP with an inserted coil resulted in the enhancement in both condensation heat transfer coefficient and heat transport limitation, as obtained in case of using internal fins. But all these effects became negligible in the range of higher rpm(above 1,000-1,200) with the transition of flow regime to annular flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1139-1144
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• 2005

This study has been performed to investigate the thermal performance of variable conductance heat pipe (VCHP) with meshed wick. The length of condenser portion in a VCHP is varied by the expansion of inert gas with the operation temperature, and the heat transport capacity is thus varied with the operating temperature. In this study, numerical evaluation of the VCHP is made for the thermal performance of VCHP, based on the diffusion model of inert gas. Water is used as a working fluid and nitrogen as a control inert gas in the copper tube. As a result, the thermal performance of VCHP has been compared with that of constant conductance heat pipe (CCHP) according to the variation of operation temperature. Maximum heat transport capacity of VCHP is mainly presented for operation temperature and the variation of operation temperature is also presented for heat transfer rate of VCHP.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.762-769
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• 2024

The TMSR-SF0 simulator is an integral effect thermal-hydraulic experimental system for the development of thorium molten salt reactor (TMSR) program in China. The simulator has two heat transport loops with liquid FLiNaK. In literature, the 95% level confidence uncertainties of the thermophysical properties of FLiNaK are recommended, and the uncertainties of density, heat capacity, thermal conductivity and viscosity are ±2%, ±10, ±10% and ±10% respectively. In order to investigate the effects of thermophysical properties uncertainties on the molten salt heat transport system, the uncertainty and sensitivity analysis of the heat transfer characteristics of the simulator system are carried out on a RELAP5 model. The uncertainties of thermophysical properties are incorporated in simulation model and the Monte Carlo sampling method is used to propagate the input uncertainties through the model. The simulation results indicate that the uncertainty propagated to core outlet temperature is about ±10 ℃ with a confidence level of 95% in a steady-state operation condition. The result should be noted in the design, operation and code validation of molten salt reactor. In addition, more experimental data is necessary for quantifying the uncertainty of thermophysical properties of molten salts.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.1
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• pp.80-87
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• 2001

Global robust diagnostic models are established based on MOM of GFDL to study the circulation in the world ocean. The horizontal grid sizes 1/2 degree, and the vertical water column is divided into 21 levels. The hydrographic data are taken from Levitus et al.(1994) and the wind stress from Hellerman and Rosenstein (1983). Based on the model results the horizontal volume, heat and salt transports across some representative sections are calculated. The preliminary results show that Though the cross-equator volume transports in the Atlantic, Indian and Pacific Oceans are all small, the heat transports across equator in the Atlantic are northward. This is clearly a result of the southward flow of the North Atlantic Deep Water and the northward compensating warm flow in the upper layer. The annual mean of the cross-equator heat transport in the Pacific Ocean from the present model is significantly lower than that calculated by Philander et at. (1987). This might indicate the importance of the Indonesian Throughflow in the heat transport in the Pacific Ocean. Our calculation shows that the heat transport through the Indonesian Archipelago is 0.5 PW, which is comparable with the poleward heat transport in the North Atlantic and Pacific Oceans. The difference in heat transports across the sections 5 and 6 demonstrates the important role of the Agulhas Current in the heat balance of the world ocean.

• Membrane and Water Treatment
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• v.7 no.2
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• pp.87-100
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• 2016

A numerical simulation of membrane evaporation process was carried out in this work. The aim of simulation is to describe transport of water through porous membranes applicable to the concentration of aqueous solutions. A three-dimensional mathematical model was developed which considers transport phenomena including mass, heat, and momentum transfer in membrane evaporation process. The equations of model were then solved numerically using finite element method. The results of simulation in terms of evaporation flux were compared with experimental data, and confirmed the accuracy of model. Moreover, profile of pressure, concentration, and heat flux were obtained and analyzed. The results revealed that developed 3D model is capable of predicting performance of membrane evaporators in concentration of aqueous solutions.