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R1234yf와 R134a 냉매의 이젝터를 적용한 냉동사이클 성능에 대한 해석적 연구
조홍현(Honghyun Cho),박차식(Chasik Park) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.7
This paper presents a numerical study on the performance of a vapor compression cycle equipped with an ejector as an expansion device to improve the COP by reducing the expansion loss and compressor work. The simulation is carried out using a model based on the conservation of mass, energy and momentum in the ejector. From the results of the simulation, the vapor compression cycle equipped with an ejector showed a maximum COP improvement of 14.0% when using R134a refrigerant and 16.8% when using R1234yf. In addition, the performance of the system with an ejector represents the increased performance as the temperature difference between condensing and evaporating increased.
대체냉매 R1234yf를 적용한 자동차용 에어컨 시스템의 성능향상에 관한 연구
조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.4
The performance of automobile air conditioning systems of R1234yf was evaluated and compared with that of R134a. In particular, the performance evaluation was carried out by installing an internal heat exchanger in order to improve the performance of the system used in R1234yf. A performance comparison between the R1234yf and R134a for automotive air conditioning revealed that the cooling capacity and COP of the 1234yf system without the IHX decreased by up to 7% and 4.5%, respectively, but those with the IHX decreased by up to 1.8% and 2.9%, respectively.
냉매 R1234yf 적용 자동차용 에어컨 Drop-in 성능 특성
조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2012 설비공학 논문집 Vol.24 No.12
In this study, the performance of mobile air conditioner(MAC) systems to which the refrigerants R134a and R1234yf were used was evaluated to compare the characteristic of automotive refrigeration cycles with refrigerant. The experimental setup of a MAC consists of an belt driven compressor, a condenser, an evaporator and a block type thermal expansion valve. The drop-in test on MAC were carried out under variable compressor speed from 800 to 2500 rpm. Performance test by using R1234yf and R134a in the same system revealed low the charge amount and mass flow rates for using R1234yf, that is, up to 10% and 17%, respectively. The compressor discharge temperature of R1234yf is 8℃ lower than that of R134a. The cooling capacity with R1234yf system decreased by 4~7% compared with R134a system. In addition, The COP of R1234yf system is lower 3~4% than that of R134a system.
R134a 및 R1234yf 적용 냉동시스템의 비가역성 분석
조홍현(Honghyun Cho),이호성(Hoseong Lee),박차식(Chasik Park) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6
In this study, the performance of mobile air conditioner(MAC) systems to which the refrigerants R134a and R1234yf were used was evaluated to compare the characteristic of automotive refrigeration cycles with refrigerant. The drop-in test on MAC were carried out under variable compressor speed from 800 to 2500 rpm. Performance test by using R1234yf and R134a in the same system revealed low the charge amount and mass flow rates for using R1234yf, that is, up to 10% and 17%, respectively. The irreversiblilty of evaporator in a R134a air conditioning system with compressor speed under idle condition was 36.8% which was maximum value, and that of compressor increased with compressor speed. The irreversibility of compressor and IHX in a R1234yf air conditioning system with IHX with compressor speed was 39.6%, 3.6% under idle condition, and those was 44.1%, 9.7% at the compressor speed of 2520 rpm.
학습환경에서 불쾌적온도에서 쾌적온도로의 변화시 생체신호 및 주관적 반응에 대한 실험적 연구
임광현(Gwanghyun Im),김진현(Jinhyun Kim),박차식(Chasik Park),조홍현(Honghyun Cho) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.11
In this study, experiments using bioelectronic signals and questionnaire surveys were carried out in learning conditions when temperatures changed from low- and high-uncomfortable to comfortable. As a result, the stress factor Photoplethysmography (PPG) decreased, while the Root Mean Square of Standard Deviation (RMSSD) of PPG increased when the indoor temperature was changed from low- or high-uncomfortable to comfortable. Additionally, the absolute power of the α-wave in the brain increased. According to the analysis of the association between the questionnaire and bioelectronic signals, the standard deviation of the stress factor as measured by pulse was closely related to the result of the thermal sensation questionnaire. In addition, it was found that the concentration on studying improved under comfortable temperatures when compared to uncomfortable temperatures.
주거용 건물의 특성에 따른 단위면적당 온실가스 배출량 분석
지창윤(Ji, Chang-Yoon),신성은(Shin, Sung-Eun),최민석(Choi, Min-Seok),박차현(Park, Cha-Hyun) 대한건축학회 2017 대한건축학회 학술발표대회 논문집 Vol.37 No.2
This study aims to determine the greenhouse gas emissions intensity (GEI) of residential buildings (detached houses, row house, multiplex house, and apartment complex) in Seoul. To this end, this study collects data on GHG emissions and characteristics(type, scale, construction year, and heating type) of 245,833 cases ana complements the statistical analysis using R. The results of statistical analysis are as follows. The more recent the buildings were constructed, the smaller the GEI is. In particular, the most dramatic decline of GEI was observed in single-family homes. Nevertheless, the GEI of single-family houses was higher than that of apartment complexes. In the case of apartment complex, the GEI decreased with the increase of the floor area. In addition, the GEI of the apartment complex using city gas heating was lower than those using district heating. The results show the validity of the greenhouse gas reduction policy for large buildings. In addition, it is also expected to help establish new policies.
표종현(Jong-Hyun Pyo),김원석(Won-Seok Kim),조홍현(Honghyun Cho),박차식(Cha-Sik Park) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.5
An experimental study was carried out to investigate performance characteristics of the hybrid solar system during spring season. The system operating condition, each load, and heat pump performance were analyzed with the cloud cover. As a results, the collector heat, solar fraction, and hot water load were decreased with a rise of the cloud. The heating load was considerably effected by the ambient temperature regardless of the cloud cover. Besides, the temperature of hot water increased with the solar radiation. The COP of the heat pump was significantly influenced by the ambient temperature, that was 2.09∼2.46 for gray day and 1.94∼2.71 for fair day, respectively.
공동주택 친환경성능의 정량적 분석을 통한 녹색건축인증기준의 실효성 검증에 관한 연구
배철학(Bae, Cheol-Hak),김선복(Kim, Seon-Bok),박차현(Park, Cha-Hyun),추승연(Choo, Seung-Yeon) 대한건축학회 2016 대한건축학회논문집 Vol.32 No.1
In order to prevent the global warming, many countries have performed the Green Building Certification Systems headed by the developed countries. G-SEED is the representative certification system in Korea for constructing Green-Buildings as other countries" LEED, BREEAM, CASBEE, GREEN STAR etc. G-SEED was established started in 2002 and has been revised several times, still has problems regarding the appropriateness of articles weight and eco-friendly efficiency of Green Building. To confirm the G-SEED effectiveness for reducing Green House Gas(GHG) emission, we suggested how to calculate the amount of the carbon dioxide emissions. In this study the amount of carbon of the green buildings certified through G-SEED is computed and analyzed . Calculating and analyzing the amount of carbon emission of 68 certified Green Buildings(apartment houses), there was a little correlation between the Green Building grade and the amount of carbon emission. Therefore it was verified that there is a little effectiveness of the green building criteria in reducing GHG emissions. The reason is that there is a few criteria of calculating the GHG in Green Building Certification, and it is needed to revise the criteria that can verify the effectiveness of Green Building by evaluating the performance quantitatively. It is not affordable to give it a rating through evaluating quantitatively the carbon emission of buildings. It is also important that green building has to give us the qualitative satisfaction of the environment and phychological comfort. If G-SEED is well coordinated by the part of quantitative assessment and qualitative assessment, the sustainable buildings could be widespread to our living places without wasting the resources of future generations or degrading the environment.