• Magazine of the Korean Society of Agricultural Engineers
• /
• v.32 no.E
• /
• pp.80-87
• /
• 1990

Energy balance equations Were developed to describe the heat transfer mechanisms in a double layer plastic greenhouse with a water curtain system. Heat transfer variables were determined by using various temperature data measured in a conventional prototype semicircular cross-section greenhouse over a range of water temperatures and water flow rates. The heat transfer coefficient between flowing water and greenhouse air was independent of water flow rates. But the heat transfer coefficient between water surface and the stagnant air space within the double plastic layer was dependent on water flow rates. Substituting the heat transfer coefficients, determined from the energy balance equations in the heat transfer equations, demonstrated various relationships among ambient air temperature, greenhouse air temperature, water temperature, and water flow rates. The heating benefits were linearly related to not only the inside and outside air temperatures but also to the water temperature. The energy conservation effects of the water curtain system were found even initial water temperatures were considerably lower than the greenhouse setting temperatures. Sensitivity analysis for heat transfer coefficients demonstrated that the heat transfer coefficient between greenhouse air and the stagnant air within the plastic layers was the most significant coefficient in the estimation of heating effects.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1159-1165
• /
• 2009

In the present study, the flow and heat transfer characteristics of a large plate heat exchanger are investigated numerically. The flow passages are very complicated due to the grooved corrugation patterns of the plate surface so that the detailed mesh and the large amount of the computation time have to be required in the numerical simulation for the conjugate heat transfer analysis. In order to accomplish the efficient and fast analysis of the heat transfer characteristics in the plate heat exchanger, a semimicroscopic method using the porous media model has been investigated numerically. The results showed that the characteristics of the heat transfer and pressure drop, which are respectively presented with Colburn j-factor and Fanning f-factor, are in a good agreement between the detailed mesh and the porous media model. The results of the present study could be applicable to the numerical analysis of entire flow passages in the large plate heat exchanger using porous media treatment.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.2
• /
• pp.141-148
• /
• 2008

A numerical simulation of brushless DC motor is performed to elucidate thermo-flow characteristics in winding and bearing with heat generation. Rotation of rotor and blades drives influx of ambient air into the rotor inlet. Recirculation zone exists in the tiny interfaces between windings. The flow separation causes poor cooling performance in bearing part and therefore the redesign of the bearing groove is required. The design parameters such as the inlet location, geometry and bearing groove threshold angle have been selected in the present simulation. As the inlet location moves inward in the radial direction, total incoming flow rate and heat transfer rate are increased. Total incoming flow rate is increased with increasing the inlet inner length. The effect of the bearing groove threshold angle on the thermal performance is less than that of other design parameters.

• 한국전산유체공학회:학술대회논문집
• /
• 2001.05a
• /
• pp.176-180
• /
• 2001

For windshield defrosting, flow analysis of inner room(vehicle) and heat conduction on the windshield surface are undertaken. Simulation for defrosting enthalpy method is usedand verification of heat and fluid flow analysis for room is done in cavity flow. The defrosting process is three dimensional phenomena and phase is changing. The result of defrosting analysis are well presenting the phase change and these results offer basic design data for defrosting phenomena.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.3
• /
• pp.208-212
• /
• 2015

This study will design the structural optimization of 21 W LED heat sink using the thermal conductive plastic materials. The thermal conductive plastic heat sink is inferior to aluminum heat sinks in thermal properties. This study will solve this problem using formability of thermal conductive plastic heat sink. A heat sink was optimized in terms of the number, and the thickness of fins and the base thickness of the heat sink, using the Heatsinkdesigner software. Also by using SolidWorks Flow simulation and thermal analysis software, the thermal characteristics of the heat sink were analyzed. As the result, the optimized heat sink has 17 fins, which are 1.5 mm thick and a 3.7 mm-thick base. The highest and the lowest temperature were $51.65^{\circ}C$ and $46.24^{\circ}C$ respectively. Based on these results, The thermal conductive plastic heat sink is considered possible to overcome heating problem when designing in complex structure.

• The KSFM Journal of Fluid Machinery
• /
• v.18 no.6
• /
• pp.37-44
• /
• 2015

Conjugate heat analysis on a high pressure turbine stage including secondary flow paths has been carried out. The secondary flow paths were designed to be located in front of the nozzle and between the nozzle and rotor domains. Thermal boundary conditions such as empirical based temperature or heat transfer coefficient were specified at nozzle and rotor solid domains. To create heat transfer interface between the nozzle solid domain and the rotor fluid domain, frozen rotor with automatic pitch control was used assuming that there is little temperature variation along the circumferential direction at the nozzle solid and rotor fluid domain interface. The simulation results showed that secondary flow injected from the secondary flow path not only prevents main flow from penetrating into the secondary flow path, but also effectively cools down the nozzle and rotor surfaces. Also thermal barrier coating with different thickness was numerically implemented on the nozzle surface. The thermal barrier coating further reduces temperature gradient over the entire nozzle surface as well as the overall temperature level.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.2
• /
• pp.202-216
• /
• 1998

A computer simulation for the performance analysis of automobile air conditioning components is carried out for the various operating conditions. The automobile air conditioning system consists of laminated type evaporator, swash plate type compressor, parallel flow type condenser, externally equalized thermostatic expansion valve and receiver drier. The overall heat transfer coefficient and the pressure drop in laminated type evaporator were obtained through experiments. In parallel flow type condenser, the performance analysis computer program using the empirical equation for heat transfer coefficient has been developed and the results are compared with experimental results. A model for matching the performance analysis programs of respective components .of automobile air conditioning system is introduced. Further, the effects of varying condenser size and refrigerant charge on the performance of automobile air conditioning system are discussed clearly.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.2
• /
• pp.125-130
• /
• 2016

In this paper, various heat dissipation designs for a rail anchoring failure detection module were investigated by a thermal flow analysis. For the detection module with the heat dissipation design on the overall housing surface, an average temperature inside the module was lowered by $25^{\circ}C$ when compared to no heat dissipation design. In addition, an internal heat-flow blocking layer and an heat conduction layer inserted between the LED module and housing case were effective in reducing the temperature in the rail anchoring failure detection, which has a limited space for installation and little air flow. Especially, the temperature near LED module decreased below $55^{\circ}C$ when the optimal heat dissipation design was applied.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.3
• /
• pp.131-139
• /
• 2009

The simulation of refrigeration cycle is important since the experimental approach is costly and time-consuming. The present paper focuses on the simulation of a refrigeration cycle equipped with a capillary tube-suction line heat exchanger(SLHX), which is widely used in small vapor compression refrigeration systems. The present simulation is based on fundamental conservation equations of mass, momentum, and energy. These equations are solved through an iterative process. The non-adiabatic capillary tube model is based on homogeneous two-phase flow model. This model is used to understand the refrigerant flow behavior inside the non-adiabatic capillary tube. The simulation results show that both of the location and length of heat exchange section influence the coefficient of performance (COP).

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.26 no.4
• /
• pp.371-377
• /
• 2017

In this study, the heat dissipation performances of metal printed circuit boards (MPCBs) and flexible printed circuit boards (FPCBs) used in light-emitting diode (LED) lights were compared and analyzed by performing a heat dissipation simulation using a thermal flow analysis program. The results were summarized graphically. The temperature distribution of the MPCB was found to be better than that of the FPCB, indicating the better heat dissipation performance of the MPCB. For the two FPCB structures studied, we confirmed the LED temperature and temperature distribution by thermal flow analysis and found that for better overall heat dissipation performance, PCBs should preferably have an asymmetric structure. We confirmed the possibility of using FPCBs, which are characterized by a flexible structure, for LED lighting.