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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Korean Journal of Air-Conditioning and Refrigeration Engineering
Journal Basic Information
Journal DOI :
The Society of Air-Conditioning and Refrigerating Engineers of Korea
Editor in Chief :
Volume & Issues
Volume 20, Issue 12 - Dec 2008
Volume 20, Issue 11 - Nov 2008
Volume 20, Issue 10 - Oct 2008
Volume 20, Issue 9 - Sep 2008
Volume 20, Issue 8 - Aug 2008
Volume 20, Issue 7 - Jul 2008
Volume 20, Issue 6 - Jun 2008
Volume 20, Issue 5 - May 2008
Volume 20, Issue 4 - Apr 2008
Volume 20, Issue 3 - Mar 2008
Volume 20, Issue 2 - Feb 2008
Volume 20, Issue 1 - Jan 2008
Selecting the target year
Effect of Radiative Mean Temperature on Thermal Comfort of Underfloor Air Distribution System
Chung, Jae-Dong ; Hong, Hi-Ki ; Yoo, Ho-Seon ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 711~717
Despite the fact that UFAD(Under Floor Air Distribution) systems have many benefits and are being applied in the field in increasing numbers, there is a strong need for an improved fundamental understanding of several key performance features of these systems. This study numerically investigates the effect of supplied air temperature and supplied flow rate on the performance of UFAD, especially focused on thermal comfort. Also this study has compared UFAD with conventional overhead air distribution system. In contrast to the well-mixed room air conditions of the conventional overheat system, UFAD system produces an overall floor-to-ceiling airflow pattern that takes advantage of the natural buoyancy produced by heat sources in the occupied zone and more efficiently removes heat loads and contaminants from the space. Thermal comfort parameters were evaluated by CFD approach and then PMV was computed to detect the occupants' thermal sensation. Results show that radiative mean temperature plays crucial role on the evaluating PMV. Until now, the radiative temperature has been the missing link between CFD and thermal comfort, but the present study paves the way for overcoming this weakness.
Experimental Study on the Performance of a Simultaneous Heating and Cooling Heat Pump in the Heat Recovery Mode
Choi, Jong-Min ; Chung, Hyun-Joon ; Joo, Young-Ju ; Kang, Hoon ; Kim, Yong-Chan ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 718~726
The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. Hence, the development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, the performance of a simultaneous heating and cooling heat pump was investigated in the heat recovery mode (HR mode). The system adopted a variable speed compressor using R410A with four indoor units and one outdoor unit. In the HR mode, the capacity and COP were improved as compared with those in the cooling or heating mode because the waste heat in the outdoor unit was utilized as useful heat in the indoor units. However, energy imbalance between heating and cooling capacity of each indoor unit was observed in the 2H-1C HR mode. Therefore, the performance of the system in the 2H-1C HR mode was enhanced by controlling refrigerant flow rate through the outdoor unit.
Frost Behavior on a One-Dimensional Fin Considering Heat Conduction of Heat Exchanger Fins
Kim, Jung-Soo ; Kang, Soo-Jin ; Lee, Kwan-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 727~732
This paper presents a mathematical model to predict the behavior of frost formed on an one-dimensional fin of heat exchanger, considering fin heat conduction under frosting conditions. The computational domain consists of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with constant fin surface temperature assumed (Case B). The results indicate that for Case B, the frost thickness and heat transfer are overpredicted in most regions of the fin, as compared with those for Case A. In addition, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length after 30mm contributes insignificantly to heat transfer.
Prediction of Density and Viscosity for
-PEC9 Mixture at Low Oil Concentration
Yun, Rin ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 733~738
Due to environmental concerns
has been reintroduced as a potential candidate to replace HFCs in refrigeration systems. Oils are always required in a vapor-compression cycle, and thus it is necessary to precisely estimate the thermodynamic mixture properties of
-lubricant oil. In the present study, the density and the viscosity of the mixture was calculated by the Redlich and Kwong type EoS and the modified Peng and Robinson type viscosity EoS, respectively. The viscosity model was based on the similarity between P-v-T and T-
-P relationships. The predicted results were compared with the experimental data of Pens ado et al. whose test conditions were 100
650 bar of pressure and 303 K
353 K of temperature with the
-POEs mixtures under 92.2 wt.% and 83.3 wt.% of
concentration. The mean deviations of the mixture density were 7.93% and 8.32% for 92.2 wt.% and 83.3 wt.% of
concentration, respectively. Concerning the viscosity, the mean deviations were 4% and 10% for 92.2 wt.% and 83.3 wt.% of
concentration under the Pensado et al.'s test conditions.
Measurement of Ground Thermal Conductivity and Characteristics of Thermal Diffusion by the Ground Heat Exchanger
Jeong, Young-Man ; Koo, Kyung-Min ; Hwang, Yu-Jin ; Jang, Se-Yong ; Lee, Yeong-Ho ; Lee, Dong-Hyuk ; Lee, Jae-Keun ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 739~745
This paper presents the measurement of ground thermal conductivity and the characteristics of ground thermal diffusion by a ground heat exchanger(GHE). A borehole is installed to a depth of 175 m with a diameter of 150 mm. To analyze the thermal diffusion property of the GHE, thermocouples are installed under the ground near the GHE. The outdoor temperature, the ground temperature, and the water temperature of the GHE are monitored for evaluating the characteristics of ground thermal diffusion. The ground thermal conductivity is evaluated by the in-situ thermal response tester and the line source model. It is found to be 3.08 W/
in this study. The ground temperature is greatly dependent on the outdoor temperature from the ground surface to 2.5 m in depth and is stable below 10 m in depth. The surface temperature of the GHE varies as a function of the temperature of circulating water. But the ground temperature at 1.5 m far from the GHE is not changed in accordance with the temperature of circulating water.
Study on Application and Economic Evaluation of New Insulation Material to Confront High Oil Price: Focus on an Apartment
Hyun, Jong-Hun ; Kim, Ji-Yeon ; Park, Hyo-soon ; Choi, Moo-Hyuck ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 746~751
The best plan to reduce the building energy consumption is that the insulation performance should be improved because the insulation and airtight of building envelopes have an effect on the energy consumption basically. New insulation materials, which have the high performance and are above insulation standard, have been developed steadily. Because there are not studies on the building energy rating system and economic evaluation considering new insulation materials, these matters should be studied. In result alternatives, which applied 6 high performance material each, reduce the annual heating energy and raise the building energy rating. Applying the vacuum insulation material(Case 1, 2) and vacuum or triple glazing can retrieves the investment with $120 and $140
150 per barrel each.
Climograph using Standard Weather Data of the region of Seoul
Cho, Min-Kwan ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 752~759
This paper is to make up the climograph using standard weather data of the region of Seoul. It is made up by existed standard weather data of which the subjected region is Seoul in order to easily use work. The factors of weather data are outside air temperature and its absolute humidity, total solar radiation, amount of clouds, wind direction, and wind velocity. The standard weather data are verified by comparing with values of the existed degree day method. As the result of their verification, the difference of the data showed less than 3% each other. And, reliability of standard weather data is thought to be same as those of degree day.
Honeycomb and Laminated Mesh as Open Volumetric Solar Receiver : Performance of Heat Transfer and Pressure Drop
Cho, Ja-Hyun ; Lee, Ju-Han ; Kang, Kyung-Mun ; Seo, Tae-Beom ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 760~766
The characteristics of heat transfer and pressure drop of several different porous materials which can be used as inserts inside solar volumetric air receivers were experimentally investigated. Generally, porous materials were inserted into solar volumetric air receivers to increase the thermal performance. In the present work, honeycomb (diameter: 100 mm, thickness: 30 mm), laminated mesh (diameter: 100 mm, thickness: 1 mm) are considered as the inserts for the experiment. The experimental apparatus consists mainly of a cylindrical ceramic duct as a receiver and an electric heater as an energy source. This system is an intake open loop, which used as air of working fluid. The temperatures inside the ceramic tube are measured by thermocouples, which are installed at each layer of the porous materials. The pressure-drop experimental apparatus is fabricated alike the above experimental equipment. An acrylic tube is used like as the ceramic tube, which has the same specifications of the ceramic tube. The pressure drop of porous materials inserted in the acrylic tube is measured between front and rear of those by transmitter. The results show that the laminated mesh surpasses the honeycomb of heat transfer and pressure drop increase as the porous material thickness and Reynolds number.
The Characteristics of Thermal Hydraulic Performance for Micro Plate Heat Exchanger with Straight channel
Kim, Yoon-Ho ; Lee, Kyu-Jung ; Seo, Jang-Won ; Jeon, Seung-Won ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 20, issue 11, 2008, Pages 767~774
This paper presented the heat transfer and pressure drop characteristics for micro plate heat exchanger with straight channel. The metal sheets for straight channel are manufactured by chemical etching and fabricated micro plate heat exchangers by using the vacuum brazing of bonding technology. The performance experiments are performed within the Reynolds numbers range of 15
250 under the same flow rate conditions for hot and cold sides. The inlet temperature of hot and cold water are conducted in the range of
, respectively. Heat transfer rate and pressure drop are evaluated by the Reynolds numbers and mass flow rates as the inlet temperature variations of the hot and cold sides. Correlations of Nusselt number and friction factor are suggested for micro plate heat exchanger with straight channel using the results of performance experiment.