내부열교환기와 TXV를 적용한 자동차용 공조시스템의 성능에 관한 수치적 연구

박차식(Cha-Sik Park) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.1

최근에 지구온난화 문제로 인하여 자동차 공조시스템은 GWP 지수가 높은 R134a 냉매를 대체할 수 있는 대체 냉매를 적용하고 있다. 본 연구에서는 R1234yf 냉매를 사용하여 내부열교환기와 가면용량형 팽창밸브인 TXV를 적용한 자동차 공조시스템의 성능특성을 해석하였다. 상용 소프트웨어인 Amesim을 이용하여 주요 부품인 압축기, 응축기, 팽창장치, 증발기와 내부열교환기를 모델링을 하여 외기온도와 응축기 휜 피치 변화에 따른 냉동사이클 시뮬레이션을 수행하였다. 외기온도가 30℃에서 40℃로 증가함에 따라 시스템의 냉방용량은 3.1% 감소하고, 압축기 소비동력은 17.1%증가하였다. 또한, 응축기의 휜 피치를 0.8 mm에서 1.4 mm로 증가시키면서, 사이클 성능특성을 해석하였다. 휜 피치가 1.0 mm 클 경우에 응축기의 방열량은 감소하였고, COP는 5.9% 까지 감소하였다. 응축기 휜 피치가 1.0 mm 보다 작은 0.8 mm에서는 시스템 성능에 큰 변화가 없어 휜 피치 1.0 mm에서 최적의 성능을 나타내는 것으로 분석되었다. Recently, automobile air conditioning systems have applied an alternative refrigerant that can replace the high GWP refrigerant R134a due to the global warming problem. This study simulated the performance of an automobile climate control system with an internal heat exchanger and TXV. Refrigerant R1234yf was applied as the working fluid. Amesim, a commercial software program, was used to model the main components of the compressor, condenser, TXV, evaporator, and internal heat exchanger. As the outside temperature increased from 30℃ to 40℃, the cooling capacity of the system decreased by 3.1%, and the power consumption of the compressor increased by 17.1%. In addition, The performance characteristics of the refrigeration cycle were simulated by increasing the fin pitch of the condenser from 0.8 mm to 1.4 mm. When the fin pitch was larger than 1.0 mm, the condenser capacity decreased, and the system COP was lowered by 5.9%. When the fin pitch of the condenser was 0.8 mm, which was smaller than 1.0 mm, there was no significant change in the system performance. Hence, the optimal performance was observed at a fin pitch of 1.0 mm.

냉매 R1234yf/R1234ze/R152a에 대한 이젝터 적용 냉동사이클의 성능 향상에 관한 연구

박차식(Cha Sik Park) 호서대학교 공업기술연구소 2015 공업기술연구 논문집 Vol.34 No.1

본 연구는 이젝터를 팽창장치로 적용하여 대체냉매에 대한 냉동사이클의 성능향상을 해석적으로 분석하였다. 이젝터 내부의 유동을 연속방정식, 에너지방정식. 그리고 운동량방정식을 이용한 이론식을 모델링하여 해석을 실시하였 다. 해석결과를 통하여 이젝터 적용 냉동사이클의 성능향상은 냉매 R1234yf가 가장 높게 나타났고, R152a가 가장 낮게 나타났다. 또한 증발온도와 응축온도의 차가 증가하는 가혹한 운전 조건일수록 이젝터 냉방사이클의 성능 향상효과가 크게 나타났다. 이젝터 디퓨져의 성능 변화에 대한 영향은 R1234yf 냉매가 가장 크게 나타났다. This paper presents a numerical study on the performance of refrigeration cycle equipped with an eiector using alternative remgerants. The simulation is carried out using the model based on the conservation of mass, energy and momentum in the ejector. Based on the results of simulation, the COP improvements of R1234yf system is highest, Pereas that of R152a system is lowest when the ejector refrigeration cycle is applied. The ejector refrigeration system represents the more irrqjroved effects with the increase of the temperature difference between condensing and evaporating. In addition, the efticiency of the ejector diffuse has an greatest effect on the performance of R1234yf system.

천안지역 친환경적 도시 설계를 위한 소음영향 평가

박차식(Cha-sik Park),강기준(Ki-jun Kang) 호서대학교 공업기술연구소 2016 공업기술연구 논문집 Vol.35 No.1

많은 도시에서 교통량과 인구의 증가로 인하여 소음 문제가 발생하고 있다 . 도시에서의 소음은 전세계가 광대하게 연구되는 공통적 문제이다 . 특히 , 도시의 소음은 공공 보건 문제로 까지 고려되어진다 . 본 연구의 목적은 현장지역의 소음 측정과 소음지도 작성을 바탕으로 천안시청 주변 도로의 소음환경을 평가하고자 하였다 . 대상지역의 소음 특성을 분석하기 위하여 6군데의 다른 지역을 선택하였다 . 소음지도 작성을 위하여 CadnaA 소프트웨어를 사용하 였다 . 소음지도 작성결과로서 , 대로변 주변의 아파트단지는 야간의 경우에 소음기준을 초과한 지역이 많은 것으로 나타났다 . Noise pollution problem has been occurred by the increase of traffic flow and population in manv cities. Noise in cities is a common issue which has been studied extensively around the world. Urban noise is especially considered as a public health problem. The purpose of this study is to evaluate environmental noise on stretches of road in Cheonan and its vicinity, based on in-situ measurements and the calculation of noise maps. To characterize noise in the evaluated road stretches, 6 measurements were taken at different points. The CadnaA software was used for the noise mapping calculations. As a results, a large part of an apartment community around the main road indicated noise levels exceeding the legal limits during nighttime.

수열원 열펌프 시스템의 냉난방 성능 특성에 대한 연구

박차식(Cha Sik Park),강기준(Ki Jun Kang) 호서대학교 공업기술연구소 2010 공업기술연구 논문집 Vol.29 No.1

The objectives of this study are to develop a simulation model to predict of a 2-stage heat pump and analysis the performance by varying heat sources. A simulation model for the 2-stage compression heat pump system was developed with each component model composed of compressors, heat exchangers, a flash tank and electronic expansion valves. The heat pump simulation program was designed to operate as the 1-stage compression in the cooling mode and to operate as the 2-stage compression in the heating mode. The two-stage compression cycle in the heat pump system was used in the heating mode with river water because the temperature difference between the heat source and the hot water temperature supplied for the heating is relatively large. The performance of the 2-stage compression cycle was better than that of the 1-stage compression when inlet temperature of condenser reservoir was higher than 40 °C.

이젝터를 적용한 냉동시이클 성능에 대한 해석적 연구

박차식(Cha sik Park) 호서대학교 공업기술연구소 2014 공업기술연구 논문집 Vol.33 No.2

본 연구는 추력손실을 감소시킬 수 있는 이젝터를 팽창장치로 적용하여 냉동사이클의 성능향상을 이론적으로 분석 하였다. 이젝터 내부의 유동을 연속방정식, 에너지방정식, 그리고 운동량방정식을 이용한 이론식을 모델링하여 해석을 실시하였다. 해석결과를 통하여 시스템의 최대성능은 면적비와 유입비가 각각 9와 0.736에서 나타났다. 또한, 이젝터를 적용한 시스템은 응축온도와 증발온도의 온도차가 클수록 성능개선 효과가 큰 것으로 나타났다 This oaper presents a numerical study on the performance of refrigeration cycle equipped with an ejector as an expansion device to improve the COP by reducing the expansion loss. The simulation is carried out using the model based on the conservation of mass, energy and momentum in the ejector. Based on the results of simulation, The ejector area ratio and the entrainment ratio are obtained for the maximum COP. In addition, the performance of the system equipped with an ejector showed the more improved effects with the increase of the temperature difference between condensing and evaporating.

노광장비 내 유동특성 규명을 통한 입자제어

박경우(Kyoungwoo Park),박차식(Cha-Sik Park),심성태(Sung-Tae Sim) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7

An exposure process, which is making a pattern at photoresist, is one of the key technologies in the field of semiconductor chip production. Therefore, researches on performance improvement of an exposure apparatus have been carried out recently. In this paper, CFD was used to predict the flow characteristics numerically in exposure apparatus in order to suggest the new shape for performance improvement. For them, analyses were performed for seven different shapes of exposure apparatus and parametric studies were carried out to suggest the efficient flow scheme that can reduce the vortex. As the results of this study, vortex is generally formed in the stage that is occurred an exposure at granite surface plate gap. Consequently, it is also found the modified shape which can reduce the strength of vortex in the stage. Henceforth, the authors will compare with real data of exposure apparatus in recent days.

열교환방식에 따른 지열히트펌프의 냉방특성에 관한 연구

차동안(Dong An Cha),권오경(Oh Kyung Kwon),박차식(Cha Sik Park),박성구(Sung Gu Park) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7

The objective of this study is to investigate the influence of the heating performance for a water-to-water 10RT ground source heat pump by using the water switching and refrigerant switching method. The test of water-to-water ground source heat pump was measured by varying the compressor speed, load side inlet temperature, and ground heat source side temperature. The cooling capacity and COP of the heat pump decreased with increasing ground heat source temperature. As a result, the water switching method with counter flow, compared to a refrigerant switching method, improves the cooling capacity and COP by approximately 8~10% in average, respectively.

냉매 R1234yf의 모세관내 유동 특성에 관한 해석적 연구

김대영(Kim, Daeyeong),박차식(Park, Cha-Sik) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.11

최근에 지구온난화 문제로 인하여 R134a 냉매에 대한 규제가 강화되면서 대체냉매로서 R1234yf 냉매가 개발되었다. 냉동사이클에서 팽창장치인 모세관은 유량제어와 압력조절의 역할을 한다. 본 연구에서는 모세관에 흐르는 냉매유동의 지배 방정식을 사용하여 R134a와 R1234yf 냉매에 대하여 해석적 연구를 수행하였다. 모세관 길이를 1-4 m로 변화시켰을 때 R1234yf 냉매의 질량유량은 47.0% 감소하였다. 모세관의 직경을 1.3-1.5 mm로 변화시켰을 때 R134a 냉매와 R1234yf 냉매의 질량유량은 각각 117.9%와 121.0% 증가하였다. 모세관 입구의 과냉도를 0-7℃ 변화시켰을 때 R134a 냉매와 R1234yf 냉매의 질량유량은 28.3%와 29.1% 증가하는 것으로 나타내었고, 모세관 입구에서 운전조건을 35-60℃로 변화시켰을 때 R134a 냉매 는 31.0%, R1234yf 냉매는 45.4% 증가를 각각 나타내었다. R1234yf has been developed as an alternative refrigerant to R134a, which has been associated with global warming. The capillary tubes as expansion valves control the mass flow rate and balance system pressure in the refrigeration cycle. The present numerical model used the governing equations including the law of conservation of mass, momentum, and energy in a capillary tube. The mass flow rate of R1234yf decreased by 47.0% as the capillary tube length was increased from 1 to 4 m. As the inner diameter of the capillary tubes was changed from 1.3 to 1.7 mm, the mass flow rate of R134a and R1234yf increased by 117.9% and 121.0%, respectively. The mass flow rate of the R134a and R1234yf increased by 28.3% and 29.1% with subcooling increasing from 0 to 7℃. In addition, when the inlet temperature of the capillary tubes was changed from 35 to 60℃, the mass flow rate of R134a and R1234yf increased by 31.0% and 45.4%, respectively.

수절환 및 냉매절환방식에 따른 지열히트펌프의 냉방특성에 관한 연구

차동안(Dong An Cha),권오경(Oh Kyung Kwon),박차식(Cha Sik Park) 대한설비공학회 2012 설비공학 논문집 Vol.24 No.8

The objective of this study is to investigate the influence of the cooling performance for a water-to-water 10 RT ground source heat pump by using the water switching and refrigerant switching method. The test of water-to-water ground source heat pump was measured by varying the compressor speed, load side inlet temperature, and ground heat source side temperature. The cooling capacity and refrigerant mass flow rate of the heat pump increased with increasing ground heat source temperature. But COP of the heat pump decreased with increasing ground heat source temperature. As a result, the water switching method with counter flow, compared to a refrigerant switching method, improves the cooling capacity and COP by approximately 6~9% in average, respectively.

In-Plane Buckling Analysis of Asymmetric Curved Beam Using DQM

Ki-jun Kang(강기준),Cha-Sik Park(박차식) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.10

편미분방정식해법을 위한 효일적인 방법 중의 하나는 미분구적법이다. 이방법은 복잡한 구조 및 하중에 따른 컴퓨터 용량의 과도한 사용뿐만 아니라, 복합알고리즘의 어려움 피하기 위해 많은 분야에 적용되어 왔다. 본 연구에 서는 내평면 등분포하중 하에서 단면적이 변하는 비대칭 곡선보의 좌굴 (buckling)을 미분구적법(DQM)으로 해석하였 다. 다양한 단면적 변화와 열림각 (opening angle)에 따른 임계하중을 계산하였다. DQM의 해석결과는 정확한 수학적 해법 (exact analytic solution)과 비교하였으며, DQM은 적은 격자점 (grid point)을 사용하여 정확한 해석결과를 보여주 었다. 또한, 다양한 단면적 변화에 따른 새로운 결과를 제시하였다. One of the efficient procedures for the solution of partial differential equations is the method of differential quadrature. This method has been applied to a large number of cases to circumvent the difficulties of programming complex algorithms for the computer, as well as excessive use of storage due to conditions of complex geometry and loading. Under in-plane uniform distributed load, the buckling of asymmetric curved beam with varying cross section is analyzed by using differential quadrature method (DQM). Critical load due to diverse cross section variation and opening angle is calculated. Analysis result of DQM is compared with the result of exact analytic solution. As DQM is used with small grid points, exact analysis result is shown. New result according to diverse cross section variation is also suggested.