Mobile QR Code QR CODE : Korean Journal of Air-Conditioning and Refrigeration Engineering
Korean Journal of Air-Conditioning and Refrigeration Engineering

Korean Journal of Air-Conditioning and Refrigeration Engineering

ISO Journal TitleKorean J. Air-Cond. Refrig. Eng.
  • Open Access, Monthly
Open Access Monthly
  • ISSN : 1229-6422 (Print)
  • ISSN : 2465-7611 (Online)

Korean Journal of Air-Conditioning
and Refrigeration Engineering

A journal devoted to investigations of HVAC and building technologies in various climatic conditions

• Editors-in-Chief: Doosam Song

상온 자기냉동장치에 대한 실험적 연구 Experimental study on a Room-Temperature Magnetic Refrigeration Apparatus

https://doi.org/10.6110/KJACR.2020.32.9.413

Jong Suk Lee

Magnetic refrigeration, which utilizes the magnetocaloric effect of the magnetic material, is highlighting alternative refrigeration technologies. It is an eco-friendly refrigeration technology using solid refrigerants, instead of CFC refrigerants. Also, it is regarded as an efficient refrigeration system to generate the temperature difference between high and low sides using the temperature change of magnetic refrigerants according to the change of the internal magnetic field, instead of using compressors that are typically power-consuming and noisy. This paper presents some experimental results obtained from a room-temperature magnetic refrigeration apparatus, which has two sets of concentric Halbach cylinder permanent magnets. Experimental results, which were obtained by using single magnetic material or combination of magnetic materials in AMR beds of the magnetic refrigeration apparatus, were discussed.

CFD 기반 고밀도 데이터센터의 공기분배시스템 효율평가에 관한 비교연구 CFD-based Comparison Study of Hot Aisle Containment and Cold Aisle Containment Solutions in High-density Data Centers

https://doi.org/10.6110/KJACR.2020.32.9.419

Jinkyun Cho ; Wonbae Suh ; Jesang Woo

High energy costs and spiking energy consumption rates have forced data centers to rethink cooling strategies. Although traditional cooling approaches, such as perimeter cooling through a raised floor plenum, are prevalent, containment approaches are gaining significant inroads. Hot aisle containment (HAC) and cold aisle containment (CAC) can improve the efficiency of legacy data center cooling and the air distribution systems. While both solutions mitigate the air recirculation and bypass, there are operational differences in application that have significant results on IT environment conditions and the thermal performance of cooling. Based on the computational fluid dynamics (CFD), the purpose of this study was to investigate the thermal performance of an air distribution system as compared to the two HAC and the CAC. By using the CFD models, the simulation and analysis were performed, with a focus on comparing the inlet air temperature distribution of rack servers based on the ASHRAE guideline. The selection of the HAC over the CAC can improve 43.2% in cooling system efficiency, corresponding to 15.9% reduction in the recirculation ratio. This paper analyzes the methods and highlights why HAC appears as the preferred solution.

액체질소의 분무냉각 막비등 열전달에 관한 연구 Study on Spray Cooling Film boiling Heat Transfer of Liquid Nitrogen

https://doi.org/10.6110/KJACR.2020.32.9.435

Yeung Chan Kim

In this study, experiments on spray cooling of liquid nitrogen were conducted and the effect of the droplet flow rate on the spray cooling heat transfer was mainly observed for the film boiling region. Experiments were performed for the range of droplet flow rate; D = 0.015~0.028 m3/(m2s). The results of the study are as follow: First, within the range of this experiment, as the droplet flow rate increased, so did the spray cooling heat flux of the liquid nitrogen. The spray cooling heat flux of the nitrogen was shown to be higher than the pool boiling heat flux, but was estimated to be lower when using the pure water of the same droplet flow rate. Second, the spray cooling heat transfer coefficients of liquid nitrogen were in proportion to the D0.7. This result agrees with that of the previous report using pure water.

창면적비와 SHGC 범위에 따른 SPD를 적용한 반응형 스마트창호의 에너지 성능 평가 Energy Performance Evaluation of Responsive Smart Windows Applying SPD According to Window Area Ratio and SHGC Range

https://doi.org/10.6110/KJACR.2020.32.9.441

Yujin Ko ; Hiki Hong ; Joonki Min

Smart skin window controls the light transmittance in real time, equivalent to adjusting the window’s solar heat gain coefficient (SHGC). It would be ideal if the SHGC can be freely controlled between 0 and 1, but controllable SHGC range is limited by the specifications of the glass. Thus, in this study, the standard controllable SHGC range (0.11~0.35) was set, and first, the energy requirements of the model with the SPD windows compared to the general window models according to the window area ratio were analyzed. Additionally, based on the standard, the effect on the energy requirement was compared through the TRNSYS18 simulation program by expanding the range (0.11~0.45, 0.11~0.55) or increasing the minimum/maximum value (0.21~0.45, 0.31~0.55). As a result, since increasing the ratio of the heating energy and decreasing of the cooling energy increased as the window area ratio increases, the annual energy showed a decreasing ratio of up to 11.7% at a window area ratio of 70%. As a result of the simulation while expanding the range based on the standard, when the controllable range was the largest (0.11~0.55), the maximum decreasing ratio (16.7%) was shown with the window area ratio of 70%. As a result of simulation while simultaneously increasing the minimum/maximum value of standard range, when the window area ratio is 40% or less, the larger the minimum/maximum value, the greater the decreasing ratio. The smaller minimum/maximum value is more advantageous at 50% or more.

기계설비법 제정에 따른 설비 정보체계 구축에 관한 연구 A Study on the Establishment of Mechanical Facility Information System Based on Mechanical Facilities Act

https://doi.org/10.6110/KJACR.2020.32.9.448

Ja Kang Yang ; Chang Jae Lee ; Sang Ki Jin ; Sun Hyo Park

Reducing greenhouse gas emissions has become a global issue, and the corresponding response should also be made regarding building energy, which accounts for a large portion of total energy consumption. Thus, this study defines the ‘Facility Information Construction’ based on the Mechanical Facilities Act, which became effective April 18, 2020, and proposes the establishment of a technology information sharing platform for developing technologies for low carbon energy efficiency of existing buildings. First, data classification is conducted on the definition of facilities and the establishment of an information system according to the enactment of the Mechanical Facilities Act, and the information system of the machinery and facility industry is established based on the classified data. The newly established information system can be efficiently used in the business system according to the Enforcement of the Mechanical Facilities Act in connection with the business process under the Mechanical Facilities Act.