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

건물 부하계산 프로그램을 이용한 외단열 시공의 에너지 절감 효과 분석 Analysis of the Energy Saving Effect for the External Insulation Construction by Building Load Calculation Method

Jaejoong Park ; Jemin Myeong ; Doosam Song

Reinforcement of insulation in apartment buildings reduces the heating and cooling energy consumption by lowering the heat transfer in the building envelope. There are differences between internal and external insulation methods in heat transmission properties. However, some building load calculation programs cannot analysis the differences between the two. This is because these programs do no account for the timelag or thermal storage effect of the wall according to the location of insulation. In this study, the heat transmission characteristics of internal and external insulation were analyzed by EnergyPlus, and heating and cooling energy demand was compared. The results showed that external insulation system had lower heating and cooling loads than internal insulation system. Also the heat transfer rate of external insulation is steadier than internal insulation. About 13.6% of heating and cooling energy demand decreased when the outdoor wall was finished with external insulation compared to the demand with internal insulation.

CFD를 활용한 바닥공조시스템 디퓨저의 성층화 모델 예측 Prediction of Stratification Model for Diffusers in Underfloor Air Distribution System using the CFD

Jeong-Eun Son ; Byeong-Ho Yu ; Seung-Ki Pang ; Kwang Ho Lee

Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings. UFAD systems use the underfloor plenum beneath a raised access floor to provide conditioned air through floor diffusers that create a vertical thermal stratification during cooling operations. Thermal stratification has significant effects on energy, indoor air quality, and thermal comfort performance. The purpose of this study was to characterize the influence of a linear bar grille diffuser on thermal stratification in both interior and perimeter zones by developing Gamma-Phi based prediction models. Forty-eight simulations were carried out using a Computational Fluid Dynamics (CFD) technique. The number of diffusers, the air flow supply, internal heat gains, and solar radiations varied among the different cases. Models to predict temperature stratification for the tested linear bar grille diffuser have been developed, which can be directly implemented into dynamic whole-building simulation software such as EnergyPlus.

부분부하 조건에서 히트펌프의 운전변수 최적화를 통한 냉방계절성능(SEER) 향상에 관한 실험적 연구 An Experimental Study on the Performance Improvement of the Seasonal Energy Efficiency Ratio(SEER) of a Heat Pump by Optimizing Operating Parameters under Partial Load Conditions

Sungkyung Choi ; Sang Hun Lee ; Sunjae Kim ; Yongchan Kim

Performance factors such as the EER(Energy Efficiency Ratio) and the COP (Coefficient of Performance) are being replaced by seasonal energy efficiency factors, like the SEER (Seasonal EER) and the SCOP (Seasonal COP) to evaluate the performance of a heat pump by the time of the year. Seasonal performance factors, such as the CSPF (Cooling Seasonal Performance Factor) and the HSPF (Heating Seasonal Performance Factor) are used to describe the heat pump's performance during the cool and hot seasons. In this study, the optimization of all heat pump's operating parameters was experimentally conducted to enhance the SEER based on the EU standard (EN 14825). Moreover, the SEER was improved by the compressor frequency, as well as indoor and outdoor fan speeds. In addition, the performance characteristics of the heat pump were studied under partial load conditions. As a result, the SEER was enhanced by 17% when the compressor frequency was optimized. An additional 2% improvement was achievable with the optimization of indoor and outdoor fan speeds.

복수정을 이용한 개방형 지열 시스템의 초기투자비 회수기간 분석 Analysis of the Initial Cost Payback Period on the Open-loop Geothermal SystemUsing Two Wells

Jeong-Heum Cho ; Yujin Nam

Recently, ground source heat pump systems are being used in buildings for cooling and heating to reduce greenhouse gas and save energy. However, ground source heat pump systems mainly use the vertical closed-loop geothermal system design rather than the open-loop geothermal system design. This is due to a lack of knowledge and few research feasibility studies. In this research, a dynamic thermal analysis numerical simulation based on a standard house model was conducted for an open-loop geothermal system. Based on heating load analysis results, the life cycle costs of a standard house using an open two-well geothermal system were analyzed and compared with a vertical closed-loop geothermal system, and a diesel boiler. As a result, it was found that using an open two-well geothermal system shows economic return on investment after three years.

고압식 스크롤 압축기 스러스트 오일 그루브 최적 설계 Optimal Design of Thrust Surface Oil Groove of a High Side Scroll Compressor

Hyun-Jin Kim ; Young-Jae No

Performance analysis has been carried out on a high side scroll compressor that had a fixed scroll equipped with a circular oil groove on its thrust surface. Oil was supplied to the oil groove through an intermittent opening from a high pressure oil reservoir formed inside the orbiting scroll hub. Oil in the groove was then delivered to both suction and back pressure chambers by pressure differentials and viscous pumping action of the orbiting scroll base plate. Mathematical modeling of this oil groove system was incorporated into a main compressor performance simulation program for an optimum oil groove design. The study findings were as follows. Pressure in the oil groove can be controlled by changing its configuration and the oil passage area. With an enlarged oil passage, the pressure in the oil groove heightens due to an increased flow rate, but the pressure elevation in the back pressure chamber is small, resulting in reduced friction loss at the thrust surface between the two scrolls. On the other hand, by increasing the oil passage area, the oil content in the refrigerant flow increases. Considering all these factors, the energy efficiency ratio could be improved by about 3.6% under the ARI condition by an optimal oil groove design.

운전자 졸음시 냉풍 자극이 뇌파 및 심전도 반응에 미치는 영향 The Effect of Cold Air Stimulation on Electroencephalogram and Electrocardiogram during the Driver's Drowsiness

Minsoo Kim ; Donggyu Kim ; Jongil Park ; Jongsoo Kum

The purpose of this study was to analyze physiological changes via a cold air reaction experiment to generate basic data that are useful for the development of an automobile active air conditioning system to prevent drowsiness. The CO2 concentration causing drowsiness in vehicle operation was kept below a certain level. Air was blown to the driver's face by using an indoor air cooling apparatus. Sleepiness and the arousal state of the driver in cold wind were measured by physiological signals. It was evident in the EEG that alpha waves decreased and beta waves increased, caused by cold air stimulation. The α/β ratio was reduced by about 52.9% and an alert state confirmed. In the electrocardiogram analysis, the efficiency of cold air stimulation was confirmed by the mean heart rate interval change. The R-R interval had a delay time of about one minute compared to the EEG response. The findings confirmed an arousal effect from sleepiness due to cold air stimulation.

골심지의 흡습제 함침에 의한 종이 재질 판형 전열교환 소자의 성능 향상 Performance Improvement of a Paper Enthalpy Exchange Element by Impregnation of the Spacer

Nae-Hyun Kim

Improvement of the enthalpy exchange element's energy efficiency is of current interest from anenergy-saving viewpoint. In this study, a LiCl-impregnated spacer was devised as a means to improve the performance of the enthalpy exchange element. Two samples were tested : one with and one without impregnated spacers of 338×338×380 mm sizes with 2.0 mm channel spacing. The results showed that the temperature efficiencies of the two samples were approximately the same. The humidity efficiency, however, was strongly affected by the LiCl impregnation. The impregnated sample yielded a 9% higher humidity efficiency under cooling and the difference increased to 14% under aheating condition. It was anticipated that more moisture would beadsorbed on the LiCl-impregnated spacers, which was delivered to their roots and eventually to the air in neighboring channels. Separate moisture adsorption tests revealed that both the adsorption rate and the amount of the adsorbed moisture are higher for the LiCl-impregnated specimen.