• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.5
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• pp.385-390
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• 2012

This paper discusses the applicability of a compact rolling piston refrigeration compressor to portable refrigerators. The capacity of this compressor is 1 cc. Using a 12 V BLDC motor, the compressor is driven from 2500 rpm to 6000 rpm. The height of the compression module and motor is approximately 56 mm, and their weight is approximately 374 g. We confirmed the effective operation of the compressor components by evaluating their compression and cooling performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.1
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• pp.29-36
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• 2012

An experimental study has been carried out to investigate the dehumidification characteristics for several operating conditions of a compact desiccant rotor. This problem is of particular interest in the design of a desiccant type of dehumidifier. Room temperature, room humidity, regeneration temperature, revolution speed and frontal air velocity of desiccant rotor are varied as operating conditions. The results obtained indicate that dehumidification rate is increased with an increase in the room humidity while dehumidification effectiveness is not changed much. It is also found that the optimal rotor speed and optimal regeneration temperature exist for maximum dehumidification rate and dehumidification effectiveness.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.10
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• pp.733-738
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• 2012

It is important issue to reduce the electric energy to save the operating cost of HVAC system. Even if electrical energy is the clean energy, it is difficult and takes high cost for storage of electricity. These cause the high peak load of electric energy for HVAC in summer season. In korea, government impose the electric charge with several grade for the purpose of cut-off the peak load of electricity. Government has a policy to support to design and install the heat/ice storage system using midnight electricity. In this study, analysis of cooling load and operating characteristics for ice storage system are performed. And, also economical efficiency is compared between ordinary charge system of electricity and midnight rate charge of electricity. The systematic and economical supports are needed for expansion of usage of energy saving equipments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.3
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• pp.97-102
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• 2014

For an analysis of the horizontal-type geothermal heat exchanger system, an understanding of the ground temperature distributions is required in order to predict system performance. Because it is difficult to decide on the underground temperature due to the adjustment of its temperature cycle, numerous calculations are required in order to decide on the temperature cycle. In this paper, Buggs formula is utilized to decide a phase shift for outdoor temperature and ground surface temperature, which are obtained from Korea Meteorological Administration. Overall, the underground temperature distribution in the Changwon region is predicted as $10.5^{\circ}C{\sim}20.3^{\circ}C$ at a depth of 3 m.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.4
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• pp.158-162
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• 2014

A series of numerical simulation has been carried out to study thermo-hydraulic characteristics of a primary surface type heat exchanger, which is designed for the evaporator and condenser of a geothermal ORC. Working fluid is geothermal water at hot side and R-245fa, which is a refrigerant designed for ORC, at cold side. Amplitude ratio of the channel and Reynolds number are considered as design parameters. Nusselt number is presented for the Reynolds number ranging from 50 to 150 and compared to analytic solutions. The result shows that higher amplitude ratio channel gives better heat transfer performance within the range of investigation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.147-152
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• 2011

The cryogenic cooling load from the top plate of cryostat to liquid helium surface, including wall conduction, thermal radiation and current leads, is investigated in a closed cryostat system for superconducting magnet. In general methods of load estimation, individual load is calculated separately, however they are actually coupled each other because of natural convection of helium vapor. Using relevant heat transfer analysis, we calculate cryogenic load with taking into account the effect of natural convection. Cryogenic load is under-estimated approximately 1% when the natural convection is ignored. The difference between actual cooling load and cooling load by individual calculation increases with supplying current.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.9
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• pp.699-703
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• 2012

The performance of the typical VAV dampers; blade type, venturi type and blade-orifice type, for the circular duct, is obtained by measuring the volume flow rate as a function of the opening degree. The performance features are discussed by comparing the volume flow rate of each damper. It is shown that the blade-orifice type damper, recently developed, is excellent in its linearity of the performance and that it is worse than the blade type but much better than the venturi type in its flow resistance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.381-387
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• 2014

The off-set strip fins (OSF) have been widely used to construct plate-fin heat exchangers. Conventional OSF is constructed in successive rows of fins. New OSF structure is suggested to have a gap between adjacent rows of fins. The gap is intended to reduce fouling by allowing small objects to flow through fins. The objective of this work is to investigate the performance of off-set strip fins with gap between successive rows. Results showed that the performance of OSF with gap can't be predicted by previous correlation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.5
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• pp.422-427
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• 2012

This study investigates on the relationship between total load which is caused by infiltration and insulation thickness against compensation effect. As the result of experiment, the PVC(Synthetic resins sash) window frame in airtightness is superior to the AL(Aluminum sash) window frame. In this study, as the increasing of insulation thickness in reference building does not reduce significantly cooling load, the compensation effect due to airtightness against infiltration is very small. But the compensation effect against infiltration can be closely related with heating load. Therefore, the proper thermal insulation thickness can be needed respect to cooling and heating load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.5
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• pp.415-421
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• 2012

Stirling engine is an external combustion engine, whose efficiency approaches that of Carnot engine with the help of a regenerator. The regenerator is a heat exchanger composed of porous medium, whose performance is dependent on the pore structure. Three types of pore structures are considered in the present study. They are wire screen, random wire and composite structure, i.e. a combination of wire screens with different hydraulic diameters. The porosity more highly affects the performance of a regenerator compared to the hydraulic diameter. The random wire can yield high effectiveness even at a high porosity. The composite mesh gives better performance when the hydraulic diameter decreases in the direction from hot side to cold side.