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

해수온도차발전 적용을 위한 역자기열량효과 발전시스템 성능연구 A Study on the Power Generation System with Reverse Magnetocaloric Effect for Ocean Thermal Energy Conversion

Yeongmin Kim ; Yoonjung Ko ; Jong Woo Kim ; Seung Jin Oh

This study aimed to performance analysis of a magnetocaloric effect power generation system that can be operated at a low-temperature difference in an ocean thermal energy conversion system. The major components of the system are a gadolinium (Gd) and a permanent magnet. Rotational motion is generated by the interaction of gadolinium with a permanent magnet. The electromagnetic and piezoelectric generators were connected to the gadolinium rotor, and the power generation performance by rotational motion was measured. The electromagnetic generator generated an output of open voltage 2V and a short circuit current of 6mA when the temperature difference between hot and cold water was about 6.5℃ and the rotation speed was 130rpm. Under the same conditions, the piezoelectric generator produced an open circuit voltage and a short circuit current of 8V and 8.2μA, respectively.

건물 내 위생설비 및 배관 시스템을 통한 병원균 전파 가능성에 대한 실험적 연구 An Experimental Study on the Possibility of Virus Transmission via Sanitary Plumbing Systems in a Building

Jinkyun Cho ; Seungmin Jang ; Beungyong Park

The building sanitary plumbing system may be one of the transmission routes for the virus. The trap without water seal can allow the aerosolized virus to enter living rooms from the drainage system; however, no experimental evidence has been presented yet. There is no risk of the virus spreading through the water supply system because the drinking water disinfection is sufficiently effective. The virus in wastewater maybe an early-warning before an epidemic develops. A small scale sanitary plumbing system was built with two simulated toilets on the same floor. This study presents evidence by experiment that virus can be aerosolized and transported on airflow within sanitary plumbing systems and enter buildings via empty traps. Typical sanitary plumbing system airflows were sufficient to carry aerosolized virus between bathrooms due to pressure differences. Traps without water seal allowed virus to enter the negative pressure chamber, encouraging cross-transmission. All test cases of no trap water seal were found to be contaminated with SF6 tracer gas. In hospitals, the infection risk via sanitary plumbing systems increases. Basically, on the premise that the trap water seal is maintained, the exhaust fan should be left running regardless of whether the toilet is used or not, and the door must be always closed.

흡착열교환기의 1차원 과도 해석해와 그 응용 One-Dimensional Transient Solution for Adsorption Heat Exchangers and Its Application

Dong-Seon Kim

A one-dimensional transient model for adsorbent heat exchangers is based on the analytical solution of an ideal adsorbent heat exchanger, which consists of one-dimensional fluid, metal, and adsorbent control volumes. Periodic boundary conditions are applied in the form of Fourier time series to obtain a general solution. The model is used to predict the performance of a silica gel-water adsorption chiller. It has been reported that the model have a high degree of predictive validity With an average error of 0.8-1.2 K for dew temperature, 2 K for exit water temperature, 0.1 kW for cooling power and 0.04 for COP. Major source of the error is the uncertainty in the boundary conditions during switching time.

다중 응축 열원 조건에서 R-1234ze(E) 냉동사이클 성능 향상에 관한 연구 A Study on the Performance Enhancement of the Multi Condensing Source for R-1234ze(E) Refrigeration Cycle

Dong Ho Kim ; Yoong Chung ; Jin Woo Yoo ; Kong Hoon Lee

In this study, the performance characteristics of each model according to the flow rate of the low-temperature cooling water heat source of the hybrid chiller combined with the adsorption chiller and vapor compression refrigeration were confirmed. The system performance characteristics included condensation and evaporation capacity and coefficient of performance with the changes of compressor and heat exchanger. It was confirmed that as the cooling water flow rate of the low-temperature condenser increased, the condenser capacity increased with the decrease of the condensation saturation temperature and the degree of subcooling increased. It was also confirmed that the cooling capacity increased as the inlet quality of evaporator decreased due to the increased cooling capacity along with the increase in cooling water flow rate of the low-temperature condenser. The direct correlation with the condensation saturation temperature was confirmed according to the load ratio of the low-temperature condenser, and the performance characteristics of the compression refrigeration system were confirmed according to the change of specific equipment. Finally, a cooling capacity of 20 RT class (70 kW) with a COP of 5.0 was confirmed.

데이터 센터의 공냉식 프리쿨링 냉동기 에너지 효율 분석 Energy Efficiency Analysis of Air Cooled Free-Cooling Chillers in Data Center

Jong Hun Kim ; Byung Hwan Um

The number of data centers and the amount of data processed worldwide has exploded. However, the growth rate of energy consumption in data centers has shown a different pattern (from 194 TWh in 2010 to 205 TWh in 2018) which is attributed the spread of uninterruptible power supply (UPS) and increase in cooling efficiency.(1) The decrease in electric power consumption due to the increase of such high-efficiency data centers can be confirmed through previous studies.(2) There are various cooling methods that benefit from the increase in semiconductor performance in data centers.(3) Recently, domestic data centers have also introduced systems that employ free cooling. In this study, the energy performance of an air-cooled free-cooling chiller and a general air-cooled chiller, in which water-side economizer (WSE) and a chiller are integrated, was compared based on historical data in Seoul, Korea. In addition, the power consumption and the cold water conditions of the data center were compared between the chillers. Finally, the energy efficiency was analyzed accordingly.