• 설비공학논문집
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• 제13권9호
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• pp.818-826
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• 2001

In this study, in-situ performance test of a wet surface finned-tube evaporator of an air source heat pump which has a rating capacity of 20RT is carried out. Since test conditions, such as indoor and outdoor air conditions cannot be controlled to satisfy the standard test conditions, experiments are done with the inlet air conditions as they exist, From the experimental data, air side heat and mass transfer coefficients were calculated by the well known heat and mass transfer analogy and tube-by-tube method. since current procedure underpredicted the experimental sensible heat factor(SHF), a proper empirical parameter was introduced to predict the experimental data with satisfactory results. This study provides the method of evaluating the heat and mass transfer coefficients of a wet surface finned-tube evaporator of which in-situ performance test in necessary.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권1호
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• pp.11-21
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• 2005

The present paper investigates the heat transfer characteristics in a cylinder packed with porous medium of solid spheres for various parameters such as mass flow rate, sphere diameter, length of the porous medium, and gas temperatures. Pressures and temperatures at the inlet and outlet regions were measured by using static pressure gages and R-type thermocouples. The modified relationship based on the Ergun equation is suggested for the estimation of pressure drops. In addition, the useful empirical correlation for thermal efficiency is obtained in the current study. Thermal efficiency is expressed in terms of non-dimensional time, sphere diameter, porosity, and pressure drops. It is also found that the pressure drop through the cylinder becomes larger as the gas temperature does higher at the inlet region, whereas it substantially decreases when the inlet flow rate decreases.

• 설비공학논문집
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• 제22권2호
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• pp.112-121
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• 2010

With the global climate changes, a global concerns on building energy uses and $CO_2$ emission to improve the environment friendly has been increasingly growing. To achieve this global goal, the Korea government has been seeking an environment-friendly and sustainable development. As the results, the government started Green Building Certification Criteria system. however the certificate system has still been at the basic stage. To upgrade and advance it's level, it's necessary to identify the current status. This study aims to pick out the items requiring improvement for the Ecology of Education Facilities. We expect that the results of this study will be helpful for the next design works of certificate system.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권4호
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• pp.211-219
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• 2002

In this study, in-situ performance test of a wet surface finned-tube evaporator of an air source heat pump which has a rating capacity of 20 RT is carried out. Since test conditions, such as indoor and outdoor air conditions cannot be controlled to satisfy the standard test conditions, experiments are done with the inlet air conditions as they exist. From the experimental data, air side heat and mass transfer coefficients were calculated by the well known heat and mass transfer analogy and tube-by-tube method. Since current procedure underpredicted the experimental sensible heat factor (SHF), a proper empirical parameter was introduced to predict the experimental data with satisfactory results. This study provides the method of evaluating the heat and mass transfer coefficients of a wet surface finned-tube evaporator of which in-situ performance test is necessary.

• 설비공학논문집
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• 제13권12호
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• pp.1205-1213
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• 2001

The electrical characteristics and particle collection efficiency of a wide-plate spacing electrostatic precipitator are numerically investigated, and the results are compared with those obtained experimentally. The electric potential and field strength near the collection plate increase with increasing the plate spacing. The electric field strength of a discharge electrode of a twisted pin type is larger than that of a rectangular type. As the roughness factor of the discharge electrode wire becomes small, or the plate spacing becomes narrow, the corona current of the precipitator increases. The numerical results agree well with those obtained from experimental method.

• 설비공학논문집
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• 제14권8호
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• pp.664-670
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• 2002

A heat sink (HS) system using heat pipes for electronics systems was studied. The experimental results indicate that a cooling capacity of up to 150w at an overall temperature difference of $50^{\circ}C$ can be attainable. The heat sink design program also showed that a computer simulation can predict the most of the parameters involved. To do so, however, the interior temperature distribution had to be verified by experimental results. The current simulation results were close to the experimental results in acceptable range. The simulation study showed that the design program can be a good tool to predict the effects of various parameters involved in the optimum design of the heat sink.

• 설비공학논문집
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• 제2권1호
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• pp.49-62
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• 1990

The forced cooling system has been widely applied to passing more electric current in the underground power transmission cable technology. In this paper, the optimum cooling span of the in-trough-indirect water cooling method within an electric tunnel was investigated. A parametric study was performed for the cable currents, the coolant flow rates, and the coolant inlet temperatures. As a result, the temperature of the inlet air has been found as the most important parameter in determination of the optimum cooling span.

• 설비공학논문집
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• 제2권1호
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• pp.74-83
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• 1990

The temperature distributions inside molds with heating or cooling tubes were calculated using special boundary element method. This special boundary element method was employed in order to reduce the error for small diameter tubes. Calculated temperature was compared with results using finite element method. It was found that the current method becomes more accurate as tubes' diameter gets smaller. Optimal arrangement of tubes for uniform temperature distribution along specific surface was found. CONMIN program was employed for the optimization.

• 설비공학논문집
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• 제18권7호
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• pp.578-586
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• 2006

The present study has been conducted to examine the effect of obstacles around a cooling tower and an air-guide to prevent recirculation. In order to analyze the interaction between external flow and cooling tower exit flow, the external region as well as the cooling, tower are included in computational domain. Two dimensional analysis is performed using the finite volume method with non-orthogonal and unstructured grid system. The standard ${\kappa}-{\varepsilon}$ turbulence model is used. To investigate the recirculation phenomena, flow and temperature fields are calculated with three approaches such as, the distance between cooling tower and obstacle, the allocated geometrical type, and the effect of height of obstacle. In addition, the air-guide is considered in the current computation. The mean recirculation rate increases with the height of obstacle. The effect of air-guide to reduce the mean recirculation rate is obviously observed.

• 설비공학논문집
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• 제14권7호
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• pp.607-616
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• 2002

This study has been conducted to evaluate the applicability of the control method in the dehumidification-integrated radiant floor cooling system in terms of stability of the room air temperature and the control variables through experiments. To do this, the relationship between the control variables in preventing floor surface condensation is first analyzed and the control method is predetermined through simulations. The results are as follows. First, it is necessary to determine the operation status of the dehumidification system according to the relationship between floor surface temperature and dew point temperature in the conditioned space. Second, outdoor reset with indoor temperature feedback control is better than on/off bang-bang control with respect to temperature stability in controlling the room air temperature and the possibility of energy savings. Finally, the humidity sensor can be located with the current thermostat in that there are small differences in absolute humidity in vertical distribution.