• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.6
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• pp.543-550
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• 2003

In order to saving the energy for HVAC system of buildings, utilization of wind-induced cross ventilation is thought to be promising. However, utilization of natural ventilation alone is not sufficient for maintaining the human thermal-comfort such as in hot and humid regions. A hybrid air conditioning system with a controlled natural ventilation system, or combination of natural ventilation with mechanical air conditioning is thought to overcome the deficiency of wind-driven cross ventilation and to have significant effects on energy reduction. This paper describes a concept of hybrid system and propose a new type of hybrid system using radiational cooling with wind-induced cross ventilation. Moreover, a radiational cooling system is compared with an all-air cooling system. The characteristics of the indoor environment will be examined through CFD (Computational Fluid Dynamics) simulation, which is coupled with a radiation heat transfer simulation and with HVAC control in which the PMV value for the human model in the center of the room is controlled to attain the target value.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.88-94
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• 1998

The thermal performance of cooling towers is affected mainly by the velocity, temperature and humidity of the entering air, In this paper, the effects of these variables are experimentally investigated for both counter-flow and cross-flow cooling towers. The cooling performance is reduced by up to 50% as the relative humidity of the entering air is increased from 40% to 80%. The higher air velocity and lower coolant flow show better cooling performance. The coolant loss rates in the present experimental conditions are in the range of 0.4 to 1.7%

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.415-423
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• 2002

An experimental study using a psychrometric calorimeter was conducted to investigate the temperature and pressure mea surement errors permitted for determining cooling capacity of an air conditioner. First, the instrument calibration was made in accordance with the related test methods and guidelines in order to accurately evaluate basic performance (cooling capacity and airs flow rate). Secondly, a parametric study was performed to examine the effect of measurement error involved if temperature and pressure measuring instruments on the cooling capacity calculation. From the results, it was found that the degree of accuracy for both temperature and pressure measurements played an important role on the error occurring in the determination of cooling capacity and needed to be maintained within a certain value to guarantee required accuracy of cooling capacity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.3
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• pp.201-208
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• 2009

Our government will make a plan regulating the cooling limit temperature of the summer season to 26 degree and the heating limit temperature of the winter season to 20 degree for energy saving. Where, the key point of this politic pursuit can be the charge system on heating and cooling cost. We have suggested new cost allocation methodology as a worth evaluation method in the precedent study, and preformed the worth evaluation and cost allocation on four kind of warm air produced from a heating system as an example. In this study, we applied the suggested method to four kind of cool air, and preformed the worth evaluation and cost allocation on each cool air. As a result, similarly to the precedent study, the more energy a customer saved, the more cooling unit cost decreased, and the more energy a customer consumed, the more cooling unit cost increased. From this analysis, we hope that the suggested methodology can offer a theoretical basis to the energy charge policy of government, and induce the spontaneous energy saving of consumers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4253-4259
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• 2015

In this study, the effects of various control methods of outdoor air cooling control system on control characteristics and energy consumption in building are researched by simulation. The system analysis modelling is done by using TRNSYS program package, and the control performances with existing outdoor air cooling methods are compared with the control ones without outdoor air cooling. As a result, appropriate operating temperature conditions of outdoor air cooling system according to outdoor temperature changes are required, and the outdoor air/return air dry bulb temperature comparison control method among the control methods shows best responses in energy savings.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.50-57
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• 2006

This study describes to analyze the cooling load characteristics for a room air conditioner as a function of supply ventilation air when an air conditioner is running An experimental apparatus consists of a test room, a room air conditioner, a humidifier, an electrical heater a supply fan and a controller The reaching time to the inside setting temperature of the room air conditioner with is evaluated theoretically and experimentally in a conditioned space cooling loads such as supply ventilation air, lighting, occupancy and infiltration. In the conditions of cooling loads for the supply ventilation air of 9.5 L/s(0.98 ACH). lights. one Person, and infiltration, the reaching time to the inside setting temperature ($27\;^{\circ}C$ dry-bulb) increases up to $35\%$ more than for no supply ventilation air condition. Theoretical modelling of the reaching time shows good agreement with experimental results.

• Tribology and Lubricants
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• v.13 no.1
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• pp.8-13
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• 1997

Generally, A motor integrated spindle is selected to perform the high speed machining, to improve the machining flexibility, and to simplify the structure of machine tools. The thermal deformation caused by heat generation of the integrated motor is, however, serious problem in motor integrated spindle system. In this study, cooling characteristics for the several kinds of cooling systems(such as, oil-jacket cooling, air cooling) are investigated and more efficient cooling method is presented. The results show that the shaft cooling by the air cooling system is effective to improve the thermal characteristic of motor integrated spindle.

• The KSFM Journal of Fluid Machinery
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• v.12 no.2
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• pp.24-30
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• 2009

Flow and noise analyses are conducted for examining a new design concept of impinging jet electronics cooling, and the analysis results are compared with conventional electronics cooling techniques. For the application of impinging jet electronics cooling method, the present study considers the air duct where air is supplied by axial fan and air flow from the duct is impinged vertically onto the electronic component heat source. Applying CFD simulation technique and fan noise model to the present cooling scheme, the cooling performance of the impinging jet as well as the operation condition and the noise characteristics of fan are investigated for various impinging jet nozzle conditions and fan models. Furthermore, the impinging jet electronics cooling analysis results are compared with the conventional parallel-flow cooling scheme to give the design concept and criteria of impinging jet cooling method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.4
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• pp.225-234
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• 2009

The present study has been preformed to investigate the effect of obstacles around a cooling tower with air-guide to prevent recirculation. The external region as well as the cooling tower are included in the computational domain to analyze the flow phenomena around a cooling tower accurately. Three-dimensional analysis is performed using the finite volume method with non-orthogonal and unstructured grid system. The standard turbulence model is used to consider the turbulence effect. In order to investigate the recirculation phenomena, flow and temperature fields are calculated with the distance between cooling tower and obstacle, the allocated geometrical type and the air-guide. The moisture fraction rates decrease with increment of the distance between cooling tower and obstacle. The effect of air-guide to reduce the mean recirculation rate is obviously observed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.7
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• pp.482-491
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• 2010

In conventional air-handling units, when the circulated air from the air-conditioned space pass through the cooling coil, the air is over-cooled to eliminate the moisture as well as to decrease the temperature. The purpose of this study is to estimate the thermal performance and energy saving of the cooling/reheating system using heat exchanger which can save both cooling energy and reheating energy by exchanging heat between the cooled air and reheated air. The energy balance equations to estimate the state of the air for each components were provided and the heat transfer rates and the energy saving rates for the system were calculated from the equations. The results showed that the energy saving was up to 40% under present conditions, and saving rates were significantly affected by the air velocity, inlet conditions and the effectiveness of heat exchanger.