• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.37 no.7
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• pp.4-8
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• 2008

현재 사용되어지는 냉매에 대한 규제와 에너지 수급불균형의 문제를 해결하기 위해 증기압축식 냉동기의 대체방안중 하나인 흡수식 시스템에 대해 알아보고 흡수식 시스템의 성능향상을 위해 차세대 냉매인 이성분 나노유체의 적용가능성을 제시하고자 한다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.1
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• pp.48-58
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• 2001

For the past few decades the vapor compression cycle with a solution circuit (VCCSC) has been known to provide high efficiency and variable capacity. In this study performance of a VCCSC cycle is examined through computer simulation. In the simulation heat exchangers were modelled by specifying UA or effectiveness values while the compressor performance was specified by an isentropic efficiency. Aqua/ammonia solution was chosen as the working fluid which can be used in the high temperature range. The results show that there exists an optimum operation condition which is dependent upon the temperatures of the external heat transfer fluids(HTFs). Besides the HTF\`s temperature, the maximum system pressure and the size of the solution heat exchanger are shown to have an influence on the optimum operation condition. Finally, as compared to a simple vapor compression heat pump with HFC134a, the COP of the VCCSC is shown to be 2∼22% higher.

• Journal of the Korean Institute of Gas
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• v.3 no.1
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• pp.14-20
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• 1999

This study describes the results of Coefficient of Performance(COP) analysis by cycle simulation for two types of absorption-compression hybrid cycle using the Water/Lithium Bromide solution pair. These types are basic hybrid systems introducing a mechanical compression process into the refrigerant vapor phase of the single effect absorption cycle. In absorption-compression hybrid cycles, coefficient of performance is improved compared with absorption cycle. Hybrid cycle Type 2 is considered as a key technology to support energy utilization system, given its capability of utilizing waste heat to drive system with a high level of efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.229-235
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• 2011

This research aims todevelopa compression/absorption hybrid heat pump system using an $NH_3/H_2O$ as working fluid.The heatpump cycle is based on a combination of compression and absorption cycles. The cycle consists of two-stage compressors, absorbers, a desorber, a desuperheater, solution heat exchangers, a solution pump, a rectifier, and a liquid/vapor separator. The compression/absorption hybrid heat pump was designed to produce hot water above $90^{\circ}C$ using high-temperature glide during a two-phase heat transfer. Distinct characteristics of the nonlinear temperature profile should be considered to maximize the performance of the absorber. In this study, the performance of the absorber was investigated depending on the capacity, shape, and arrangementof the plate heat exchangers with regard tothe concentration and distribution at the inlet of the absorber.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1367-1373
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• 2011

This research concerns the development of a compression/absorption high-temperature hybrid heat pump that uses a natural refrigerant mixture. Heat pumps based on the compression/absorption cycle offer various advantages over conventional heat pumps based on the vapor compression cycle, such as large temperature glide, temperature lift, flexible operating range, and capacity control. In this study, a lab-scale prototype hybrid heat pump was constructed with a two-stage compressor, absorber, desorber, desuperheater, solution heat exchanger, solution pump, liquid/vapor separator, and rectifier as the main components. The hybrid heat pump system operated at 10-kW-class heating capacity producing hot water whose temperature was more than $90^{\circ}C$ when the heat source and sink temperatures were $50^{\circ}C$. Experiments with various $NH_3/H_2O$ mass fractions and compressor/pump circulation ratios were performed on the system. From the study, the system performance was optimized at a specific $NH_3$ concentration.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.193.2-193.2
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• 2012

달착륙선 등과 같은 특수 목적을 위해 제작된 우주용 착륙선에는 착륙 시 전달되는 충격하중이 탑재장비로 전달되지 못하도록 연착륙(soft-landing)을 위한 충격흡수 메커니즘이 구현되어 있어야 한다. 일반적으로 자동차 및 항공기에서는 실린더와 피스톤으로 구성된 유공압식 완충장치를 주로 사용하여, 피스톤 압축으로 실린더 내부 오일 또는 압축공기가 오리피스를 통하여 분출됨에 따라 유체마찰 에너지를 활용한 충격 흡수장치가 일반적이다. 그러나 이와 같은 지상 장비용 유공압식 충격흡수 메커니즘은 진공 및 무중력 우주 환경하에서 오리피스 기능 상실, 유압유 기화 현상 및 극저온/고온 환경에서의 성능저하 등의 문제점으로 인하여 우주용 착륙선 충격완충장치로 적용이 불가능하다. 따라서 기존의 우주용 착륙선의 대부분은 충격에너지를 기계적인 좌굴 소성 변형에너지로 변환하여 충격을 흡수할 수 있도록 알루미늄 허니콤을 주로 많이 사용하여 왔다. 본 연구에서는 진공 및 무중력 우주환경에서 착륙선 충격완충 장치로 적용이 가능하도록 실리콘 포옴과 스프링을 조합하여 구성하였으며, 충격완충 매체로 유압유 및 공압을 대체할 수 있도록 실리콘 포옴을 후방 사출 성형 방식으로 적용하여 오리피스를 통과한 실리콘 포옴의 변형에너지로 충격에너지를 흡수하게 함으로서 착륙 완충효율을 극대화 할 수 있도록 검토하였다.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.3
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• pp.19-24
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• 1991

본 고에서는 자동차 안전대책중에서 One-box car의 전면충돌 안전대책에 대하여 개략적으로 소개하고자 한다. 1. 충돌기본식 1/2M$V^{2}$=F.S에서 에너지 흡수율이 frame의 변형 평균 하중과 차체 변형량에 좌우된다. 2. frame 형상은 굽힘형보다 압축형이 동일한 변형구간에서 월등한 충돌에너지를 흡수한다. 3. 압축형 frame의 에너지 흡수효과는 main-frame의 버팀강도가 e.a-frame의 변형 하중보다 강해야만 그 효과를 충분히 얻을 수 있다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.191-196
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• 2010

Hybrid heat pumps, which combine the vapor compression and absorption heat pump cycle, can efficiently produce hot water of $80^{\circ}-90^{\circ}C$ from the low temperature of ${\sim}50^{\circ}C$. In this study, the performance of a two-stage hybrid heat pump (HHP) was compared with a single-stage hybrid heat pump using EES (Engineering Equation Solver). For the same operating conditions, the two-stage HHP showed a slightly higher COP (Coefficient Of Performance) and more stable operating conditions than the single-stage HHP. Moreover, the maximum working fluid temperature of the two-stage HHP was found to be lower than that of the single-stage HHP by about 40 K, which makes the working conditions of the lubricating oil safer. The COPs of both systems decreased with increasing UA-values. However, the heat output of the HHP was increased at the same time.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.451-456
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• 2005

The mathematical model for the heat exchangers of absorber and desorber is made in the elementary control volume method and the thermodynamic properties of working fluid. water/ammonia mixture. are calculated by some fundamental subroutines in RefProp 7.0 and flash subroutines made by authors The simulation results show that two-stage cycle has higher COP than single stage if temperature lift is high: the performance of single stage compression cycle can be improved by increase of absorber pressure. but the performance of two-stage compression cycle can not be improved in this way : the compressor discharging temperature of two-stage compression is much lower than that of single stage cycle. which is very important to the safety operation of CA heat pump. Major parameter comparison between the cycles at their optimal configurations is also given.

• Solar Energy
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• v.18 no.2
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• pp.31-49
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• 1998

Four main solar cooling technologies have been developed over the past twenty years are considered in this paper. These technologies include absorption, vapor compression, desiccant, adsorption, etc. All of these solar cooling technologies considered here are solar thermal ones. The destails of the thermodynamic cycle of these solar cooling technologies are given. The general concept of these solar cooling and the relative advantages among them are also presented. At last, the status and outlook for each approach are summarized.