• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.11
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• pp.761-769
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• 2007

The purpose of this study is to present a simplified model of predicted mean vote (PMV) using multiple regression analysis. We performed the experiments and the numerical calculations in the lecture room during summer and winter to simplify PMV. And the multiple regression analysis on PMV was conducted to estimate the contribution of independent variables toward PMV. From the multiple regression analysis, we found that the effect of independent variables on PMV followed in order, clo value>air temperatur>air velocity>mean radiant temperature>relative humidity. And the simplified PMV was proposed through a few assumptions and then was compared with original PMV. They had a good agreement with each other. Additionally, we compared the simplified PMV with EDT. We expected that the simplified PMV can be more useful than EDT to evaluate the thermal comfort in the place, where radiation is dominant. But the comfort range of the simplified PMV should be adjusted to predict the exact thermal comfort in the future.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.814-819
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• 2008

The purpose of this study was developing the building materials for creation the comfortable IAQ. By reducing formaldehyde(HCHO) known as the main factors of Sick House Syndrome. This material must be revealed the physical and eco-friendly performance, so this study set up the basic standards for building materials. The source of physical performance evaluation is Korea Industrial Standards and the base of environmental ability is the Eco Label considering certificated system related to an apartment house. Because the developed material was satisfied with the established standards, it was tested in mock-up room for obtaining the real date from indoor air. The mock-up test was conducted according environmental standard method for indoor air Quality of the ministry of environment. The result of this study were as follows; the functional building materials had a effect to reduce the formaldehyde concentration for a initial period without wall paper, so additional development is needed for application with the wall paper and the available period.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.10
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• pp.646-655
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• 2011

This study aimed at quantifying the impact of the reinforced standard for envelope insulation on heating and cooling energy consumption in a Korean detached house as well as at identifying the effect of regionally subdivided standards. For them, a series of simulations for application of the reinforced standard on respective walls, roof, floor, windows, and all envelopes were computationally conducted for a prototypical detached residential building. In addition, the subdivided standards were applied to each regions-central and southern regions, and the Jeju island. Analysis revealed that heat transfer through envelopes was the most significant source of building heat gain and loss; the reinforced standard effectively reduced heating energy consumptions, especially in central region; and the subdivided standards did not presented a clear difference in the amount of energy consumption for the southern region and the Jeju island, thus, a further study is required to investigate the necessity of regional subdivisions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.8
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• pp.538-544
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• 2010

An experimental investigation is presented to study the effect nozzle spacing, jet to plate spacing and Reynolds number on the local heat transfer to normally upward impinging submerged circular water jets on a flat heated surface. Nozzle arrays are a single jet(nozzle dia. = 8 mm), a row of 3 jets(nozzle dia. = 4.6 mm, nozzle spacing = 37.5 mm) and a row of 5 jets(nozzle dia. = 3.6 mm, nozzle spacing = 25 mm), and jet to plate spacing ranging from 16∼80 mm(H/D = 2∼10) is tested. Reynolds number based on single jet exit condition is varied 30000∼70000($V_o$ = 3∼7 m/s). Except for the condition of H/D = 10, the average Nusselt number of multi-jet is higher than that of single jet. For H/D = 2, average Nusselt number is increased by 50.3∼82.5% for a row of 3 jets and by 52.9∼65.2% on a row of 5 jets when compared to the average Nusselt number on the single jet.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.8
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• pp.509-514
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• 2010

A numerical simulation of passenger evacuation in a subway station was performed by coupling the passenger flow analysis and the fire simulation. The algorithm of the passenger flow analysis was based on a DEM (Discrete Element Method) using the potential map of the direction vector for each passenger. This algorithm was improved in the present study as to use finer grid smaller than a passenger in order to resolve detailed geometry of the station and to resolve the behavior of passengers in the bottleneck at the ticket gate considering the collision of passengers to a wall or with other passengers. In the fire simulation, the CO distribution predicted by using CFD was used to take into account the effect of toxic gases on the passengers' mobility. The methodology proposed in the present study could be used in designing safer subway station in case of fire occurrence.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.7
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• pp.447-454
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• 2008

The regenerative evaporative cooler(REC) is to cool a stream of air using evaporative cooling effect without an increase in the humidity ratio. In the regenerative evaporative cooler, the air can be cooled down to a temperature lower than its inlet wet-bulb temperature. Besides the cooling performance, for practical application of the regenerative evaporative cooler, the compactness of the system is also a very important factor to be considered. In this respect, three different configurations, i.e., the flat plate type, the corrugated plate type, and the finned channel type are investigated and compared for the most compact configuration. The optimal structure of each configuration is obtained individually to minimize the volume for a given effectiveness within a limit of the pressure drop. Comparing the three optimal structures, the finned channel type is found to give the most compact structure among the considered configurations. The volume of the regenerative cooler can be reduced to 1/8 by adopting the finned channel type as compared to that of the flat plate type.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.7
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• pp.486-491
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• 2008

The performance of a microturbine CHP system equipped with an absorption chiller was analyzed by modeling it. The microturbine with recuperator was simulated with the Brayton cycle model. The mass flow rate and available heat energy of the exhaust gas from the microturbine were simulated. These results were utilized as input values for the generator of the absorption chiller. The absorption chiller is a single-effect air cooled type with a solution heat exchanger. The heat input into the generator was proportional to the heat transfer rate and the UA values of the heat exchangers of the absorption chiller. Furthermore, the COP of the absorption chiller increased with respect to an increase of the heat input into the generator, under the sufficient evaporator capacity condition. When the capacity of the CHP system increased from 30 to 60 kW, the mass flow rate of the LiBr for the absorption chiller doubled, and the UA values for evaporator and condenser increased by factors of x3.9 and x3.4, respectively, under the same COP condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.8
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• pp.401-407
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• 2017

The effect of different rib geometries such as V-shaped continuous (case A), parallel broken (case B), and V-shaped broken (case C) ribs on local heat transfer distributions and pressure drops in a divergent channel with $30^{\circ}$ inclined ribs on one wall or two walls was investigated for Reynolds numbers from 22,000 to 75,000. Top and bottom walls were insulated; two side walls were uniformly heated in the divergent channel. Heated walls were composed of 10 isolated coper sections and length-to-outlet hydraulic diameter ratio of 10. Rib height-to-outlet hydraulic diameter ratio was 0.1, and rib pitch-to-height ratio equaled 10. Results revealed that V-shaped continuous rib (case A) produced approximately 1.4 times higher average Nussselt number than in the parallel broken rib (case B), and V-shaped broken rib (case C) in the channel with two ribbed walls at Re = 54,000.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.10
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• pp.947-955
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• 2005

For the purpose of evaluating the thermal performance for air-barrier air conditioning system in perimeter zone, two air-conditioning systems, conventional perimeter air-conditioning system and air-barrier system, are evaluated and compared by scale model experiment and simulation during cooling season. As a result, measurement shows that supply air velocity of 1 m/s in the upstream direction at perimeter is more effective. Air-barrier system could reduce the cooling energy by $10\sim20\%$ compared with conventional system. Numerical simulation was carried out considering solar effect for reliable result. This method has improved the accuracy of numerical simulation for the space affected by the solar radiation. Both measurement and simulation results show that supply air velocity of 1 m/s at perimeter is the most effective.

• 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.