• Journal of Biosystems Engineering
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• v.33 no.6
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• pp.396-403
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• 2008

Because thermal non-uniformity of transported agricultural products is mainly affected by cooling air flow pattern in the cold transport equipment, the analysis and control of flowfield is key to optimization of cold transport equipment. The objectives of this study were to estimate the effects of geometric and operating parameters of cold container on the air flow and heat transfer, and find the optimum design parameters for the low temperature level and its uniformity in given cold container with CFD simulations. Existences of ducts, gaps between pallets and geometries of exit as geometric parameters and fan blowing velocity as operating parameter were investigated. CFD simulations were carried out with the FLUENT 6.2 code. The result showed that optimum design condition was bulk loading with no duct, wall exit and 8.0 m/s of fan blowing velocity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.3 s.258
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• pp.256-263
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• 2007

The purpose of this study is to investigate the cooling performance of heat sinks for an electronic telecommunication system by adequate natural convection. Heat generation rates of electronic components and the temperature distributions of heat sinks and surrounding air are analyzed experimentally and numerically. In order to perform the heat transfer analysis for the thermal design of telecommunication system a program is developed. The program used the graphic user interface environment to determine the arrangement of heat sources, interior fan capacity, and heat sink configuration. The simulation results showed that the heat sinks were able to achieve a cooling capacity of up to 230W at the maximum temperature difference of $19^{\circ}C$. To verify the results from the numerical simulation, an experiment was conducted under the same condition as the numerical simulation, and their results were compared. The design program gave good prediction of the effects of various parameters involved in the design of a heat sinks for an electronic telecommunication system.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.161-167
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• 2009

The liquid solar air conditioning system is introduced as an alternative solution to control air condition and to save electrical energy consumption. The heat and mass transfer performances of dehumidifier/regenerator in liquid solar air conditioning system are influenced by air and desiccant condition. The application of this system, the thermal energy from the sun and inlet air are unable to control, but operation parameter of other components such as pump, fan and sensible cooling unit are able to control. The equilibrium point of heat and mass transfer are the liquid desiccant and inlet air conditions, where, the heat and mass are not transferred between the liquid desiccant and vapor air. By knowing equilibrium point of heat and mass transfer, the suitable optimal desiccant conditions for certain air condition are funded. This present experiment study is investigated the equilibrium point heat and mass transfer in various air and desiccant temperature. The benefit of equilibrium point heat and mass transfer will be helpful in choose and design proper component to optimize electrical energy consumption.

• Journal of Bio-Environment Control
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• v.9 no.1
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• pp.27-39
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• 2000

In this study, we quantitatively compare the cooling effects of single span plastic greenhouses by opening or shutting of toot and side vents, and operation of fan or sprinkler. With those variables, we simultaneously made experiments at 4 greenhouses under equivalent conditions. By the experiments, the shutting of roof and side vents caused the high temperature difference of indoor and outdoor which the crops cannot be cultivated. However, the opening of the windows effectively reduced the indoor temperature and showed uniform temperature distribution in the greenhouses. The sprinkler abruptly reduced the indoor temperature, and showed excellent cooling effects. Finally, this paper provides the fundamental data for environmental control in greenhouses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.288-296
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• 2019

Radiation cooling has used ceilings or floors as cooling surfaces. In such cases, to avoid moisture condensation on the surface, the surface temperature needs be higher than the dew point temperature or an additional dehumidifier is added. In this study, with a goal for residential application, intentional moisture condensation on the cooling surface was attempted, which increased the cooling capacity and improved the indoor comfortness. This method included two separate refrigeration cycles - convection-type dehumidifying cycle and the panel cooling cycle. Test results on the panel cooling cycle showed that, at the standard outdoor ($35^{\circ}C/24^{\circ}C$) and indoor ($27^{\circ}C/19.5^{\circ}C$) condition, the refrigerant flow rate was 8.8 kg/h, condensation temperature was $51^{\circ}C$, evaporation temperature was $8.8^{\circ}C$, cooling capacity was 376 W and COP was 1.75. Furthermore, the panel temperature was uniform within $1^{\circ}C$ (between $13^{\circ}C$ and $14^{\circ}C$). As the relative humidity decreased, the cooling capacity decreased. However, the power consumption remained approximately constant. In the convection-type dehumidification cycle, the refrigerant flow rate was 21.1 kg/h, condensation temperature was $61^{\circ}C$, evaporation temperature was $5.0^{\circ}C$, cooling capacity was 949 W and COP was 2.11 at the standard air condition. When both the radiation panel cooling and the dehumidification cycle operated simultaneously, the cooling capacity of the radiation panel cycle was 333 W and that of the dehumidification cycle was 894 W, and the COP was 1.89. As the fan flow rate decreased, both the cooling capacity of the radiation panel and the dehumidification cycle decreased, with that of the dehumidification cycle decreasing at a higher rate. Finally, a possible control logic depending on the change of the cooling load was proposed based on the results of the present study.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.339-344
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• 2005

A PEMFC system model for FCEV was constructed and simulated numerically to examine the heat/water flow of the system and air/fuel humidification process for various operation conditions (ambient pressure /temperature/humidity, operating temperature, power load). We modeled PEMFC stack which can generate maximum electricity of about 80 kW. This stack consists of 400 unit cells and each unit cell has $250cm^2$ reacting area. Uniform current density and uniform operating voltage per each cell was assumed. The results show the flow characteristics of heat and water at each component of PEMFC system in macro-scale. The capacity shortage of the radiator occurred when the ambient was hot $(over\;40^{\circ}C)$ and power level was high (over 50 kW). In spite of some heat release by evaporation of water in stack, heat unbalance reached to 20kW approximately in such a severe operating condition. This heat unbalance could be recovered by auxiliary radiators or high speed cooling fan with additional cost. In cold environment, the capacity of radiator exceeded the net heat generation to be released, which may cause a problem to drop the operating temperature of stack. We dealt with this problem by regulating mass flow rate of coolant and radiator fan speed. Finally, water balance was not easily broken when we retrieved condensed and/or unused water.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.1
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• pp.39-45
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• 2016

Thermal management of a fuel cell is important to satisfy the requirements of durability and efficiency under varying load conditions. In this study, a linear state feedback controller was designed to maintain the temperature within operating conditions. Due to the nonlinearity of automotive fuel cell system, the state feedback controller results in marginal stable under load condition from $0.5A/cm^2$ to $0.7A/cm^2$. A PWM (Pulse Width Modulation) and the modified state feedback controller are applied to control the temperature under the load condition from $0.5A/cm^2$ to $0.7A/cm^2$. The cooling system model is composed of a reservoir, radiator, bypass valve, fan, and a water pump. The performance of the control algorithm was evaluated in terms of the integral time weighted absolute error (ITAE). Additionally, MATLAB/SIMULINK$^{(R)}$ was used for the development of the system models and controllers. The modified state feedback controller was found to be more effective for controlling temperature than other algorithms when tested under low load conditions.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.433-439
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• 2001

An experimental study was carried out on the characteristics of the mixed-convection heat transfer from a protruding heat source module which had uniform heat flux and was located on a flat plate in the inclined channel. The effects of the inclined channel(${\varphi}=0{\sim}90^{\circ}$) was studied for the input power($Q=3,\;7W$) and inlet air velocities($V_{i}=0.1{\sim}0.9m/s$). Experimental results indicate that the input power was most effective parameter on the temperature differences between inlet air and module. The effects of the inclined angle was negligible when the inlet velocities were above 0.5m/s and 0.9m/s at Q = 3W, 7W respectively. As the inclined angle of the channel increases, the temperatures of the module are decreased. So we obtained the best condition on the adiabatic board at the vertical channel.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.31-36
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• 2010

A small unmanned helicopter was suggested to replace the conventional spray system. Aerial application using an agricultural helicopter helps precise and timely spraying, and reduces labor intensity and environmental pollution. In this research, a rotor system (SW05) was developed and its lift capability was evaluated. Lift force for the dead weight of the helicopter was obtained at the grip pitch angle of $12^{\circ}$. As the pitch angle increased to $14^{\circ}$ and $16^{\circ}$, the payload increased to 176 N and 216 N, respectively. Compared with SW04 airfoil performance in the total lift, the SW05 airfoil showed nearly the same capacity, but the payload of the SW05 was reduced because of the increased dead weight. A rated flight condition was defined as lifting mean payload of 294 N with the grip pitch angles of $16{\sim}17^{\circ}$ at the rotor rotating speed of 850~950 rpm for the adjusted engine power. The fuel consumption would be 4.8~6.0 L/hr, and the air temperature of cooling fan should be kept below $160^{\circ}C$.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.5
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• pp.486-493
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• 2015

In this paper, a battery model for electric vehicle virtual platform was developed. A battery model consisted of a battery cell model and battery thermal management system. A battery cell model was developed based on Randles equivalent circuit model. Circuit parameters in the form of 3D map data was obtained by charge-discharge experiment of Li-Polymer battery in various temperature condition. The developed battery cell model was experimentally verified by comparing voltages. Thermal management system model was also developed using heat generator, heat transfer and convection model, and cooling fan. For verification of the developed battery model in vehicle level, the integrated battery model was applied in to EV(electric vehicle) virtual platform, and virtual driving simulation using UDDS velocity profile was conducted. The accuracy of the developed battery model has been verified by comparing the simulation results from EV platform with the experimental data.