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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
  • ISSN : 1229-6422 (Print)
  • ISSN : 2465-7611 (Online)

폐열수 유량에 따른 축열식 판형 열교환기의 축열 및 방열 특성 Heat Storage and Release Characteristics of Plate type Heat Exchanger with Thermal Storage to the Flow Rate of Waste Heat Water

https://doi.org/10.6110/KJACR.2019.31.6.237

Donghyun Kim ; Donggyu Lee ; Dong-Yeol Chung ; Jong-Hyeon Peck ; Chaedong Kang

During the industrial process, a huge amount of waste heat is discharged from temperatures ranging from 60 to 90℃. The operation of high temperature heat pump system which utilizes the waste heat in industries, requires stable conditions due to the need for high reliability in the manufacturing process. In this study, a plate heat exchanger (3 kW cap.) with phase change material was used to conduct different types of heat storage/release experiment. Waste heat water and brine are utilized as the working media to circulate in the heat exchanger. Heat storage and heat release were performed based on the individual flow rate of the waste heat water and the brine. As a result, it was established that the amount of heat generated by PCM contributed to the initial state in the heat release process. In other words, when the waste heat is interrupted or when it is in normal operating condition, the average heat transfer rate of 3 kW can be maintained for more than 5 minutes using PCM.

기류분석을 통한 종합병원(외래)진료부의 공기 감염 개선 연구 A Study on the Improvement of Air Infection in General Hospital(Outpatient Department) through Airflow Analysis

http://dx.doi.org/10.6110/KJACR.2019.31.6.246

Yong Woo Song ; An-Na Won ; Jung-Ha Hwang ; Jin Chul Park

This study was conducted to investigate and possibly prevent airborne infection in general hospitals The CFD analysis of emergency and outpatient departments was summarized as follows; First, assessment on the first floor of the general hospital revealed that indoor exhaust air was not ejected in concurrence with the supply air, which could lead to an air shutdown. Second, CFD analysis confirmed the results of the actual survey that air congestion and inflow into other spaces may increase the probability of airborne infection. Third, the CFD analysis reflecting the improvement plan established that when the exhaust in the lobby was increased and the door was opened, there was difficulty in air control. When all the doors were closed, pressure differences occurred on the left and right sides of the lobby. Particularly, air flow may be stagnant in the stairwells and corridors, or an introduction of air in the lobby. Further installation of the front rooms, doors and exhaust outlets also enhanced the control of air flow between spaces, and flow through staircases and elevators. Therefore, it is thought that the separation of space and the proper location of exhaust could be the most effective way of controlling airflow in hospitals. In addition, it is necessary to put in place measures to reduce the possibility of airborne infection by applying each of the exhaust systems by space.

과도 상태에서 R-600a와 R-134a의 증기 응축 특성에 관한 실험적 연구 Experimental Investigation of Refrigerant Vapor Condensation During a Transient tate

http://dx.doi.org/10.6110/KJACR.2019.31.6.258

Gaeun Lee ; Ji Hwan Jeong

Recent research on refrigeration systems indicate that in some instances refrigerant enters the capillary tube in a sub-cooled state, but the refrigerant remains in the two-phase state rather than in liquid phase only. This phenomenon is referred to as non-equilibrium state deviating from thermodynamic equilibrium. Previous studies confirms the non-equilibrium state of refrigerants. Majority of these experiments were done with R-600a as the working fluid. To understand the non-equilibrium phenomenon of R-600a, it is necessary to not only study its effects on the system but also its refrigerant properties. Therefore, comparison of phase change between R-600a and other refrigerants is essential. In the current study, experiments were conducted to investigate the process of phase change in refrigerants through processes such as condensation by inducing sudden pressure change and subsequently obtaining the pressure change curve that reaches the equilibrium state by condensation. Through comparison the rate of condensation of the refrigerants in stationary condition during the phase change process, the difference in characteristic between R-600a and R-134a was investigated.

설비공학 분야별 최근 연구 동향 :2018년 설비공학논문집 발표논문에 대한 종합적 고찰 Recent Progress in Air-Conditioning and Refrigeration Research : A Review of the Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2018

https://doi.org/10.6110/KJACR.2019.31.6.265

Doosam Song ; Dong-Seon Kim ; Sumin Kim ; Hyun Jung Kim ; Yujin Nam ; Youn Cheol Park ; Young-Jin Baik ; Jin-Kyun Cho ; Jae-Weon Jeong

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2018. The objective of this article is to understand the current issues in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities as per the recent research. Summary of this paper is follows : (1) The papers published in the field of building mechanical system can be categorized into equipment for multi-residential buildings and building envelope related technology, data center and clean room related technology, renewable energy related technology, and other related technologies. The topics included the energy consumption, indoor environment analysis, energy saving measures for radiant floor heating, temperature stratification of underfloor air-conditioning system, management of electric power demand, clean room humidification, initial cost of central heating and cooling system, solar thermal storage, data center air conditioning system and its performance evaluation, and underfloor heat exchanger performance etc. (2) Articles in the field of building environment can be classified into indoor environment, building energy and others. The research topics included; the comfort of passenger in automobile, the roof ventilation of the arcade type market, the flush out of new apartment buildings, window energy efficiency ratings, the windows' airtightness and opening performance, pollutant diffusion in national inpatient isolation units, shading evaluation of PV module, light-shelf with PV, hospital building energy management process, IAQ in children's facility, underground parking lot, smoke control, cool loop etc. (3) Various topics were reported in the field of refrigeration system. The topics included; membrane-based dehumidification system for residential building, heat pump performance enhancement using waste heat, LiCL dehumidification performance, integrated vehicle heat management, heat recovery system, regeneration type geothermal heat pump, open geothermal system, plate heat exchanger, freezer operation error diagnosis, absorption type refrigerator, two-stage inflatable auto-cascade refrigerator, electric scroll compressor, and absorption refrigerator with thin film adsorption heat exchanger etc. (4) The topics of the papers published in the field of heat and mass transfer included; the performance of multi-stacked fuel cell systems, heat dissipation performance of heat sink, heat transfer and pressure drop of the liquid nitrogen cooling heat exchanger, compressive dehumidifier, pressure loss and heat transfer of plate heat exchanger, heat and mass transfer of heat exchanger, inner tube heat transfer coefficient of the supercritical carbon dioxide, heat storage and heat dissipation characteristics of the regenerative dual cylindrical tubular heat exchanger, the liquid evaporator heat transfer, and the thermal conductivity of the vapor chamber. (5) Ventilation was the most cited keyword in the papers published in 2018, while the subsequent were the heat exchange, heat transfer, energy performance, air-conditioning, refrigeration, heat pump, dehumidification, building energy, absorption chiller, compressor, PV, refrigerant, simulation, data center, thermal sensation, mass transfer, floor heating etc.

원지 투기도 및 투습도가 전열교환소자의 성능에 미치는 영향에 대한 연구 A Study on the Effect of Paper Permeance and Moisture Transmission Rate on the Performance of Enthalpy Exchange Elements

https://doi.org/10.6110/KJACR.2019.31.6.279

Jeong-Kun Lee ; Nae-Hyun Kim

Properties, such as air permeance, and moisture transmission rate are known to affect the thermal performance of enthalpy exchange in elements made of paper. Additionally, these properties are highly associated with the paper manufacturing processes including beating, calendering as well as addition of moisture absorbents. In this study, we investigated the effects of paper manufacturing processes and absorbents on air permeance and moisture transmission rate through experiments. The results showed that wet beating was more effective than free beating for improvements in the air permeance. Furthermore, lowering of the calendering speed was found to be beneficial to air permeance. Four enthalpy exchange elements were made using papers having different properties. Test results revealed that the sample made by wet beating reduced the rate of air leakage by 49% as compared to the sample made through free beating. After the amount of impregnated LiCl increased from 10% to 14%, the enthalpy efficiency of the elements increased by 39% in cooling condition and by 15% in heating condition.