COMPACT BRAZED PLATE HEAT EXCHANGERS FOR CO2 HEAT PUMP WATER HEATERS

DANIEL LEIGHTON,YUNHO HWANG,REINHARD RADERMACHER 대한설비공학회 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.4

The plate-type heat exchanger is found to be well suited for the application of a transcritical CO2 heat pump water heater. A CO2 heat pump water heater test facility was used to evaluate the performance of a high-pressure plate-type heat exchanger. The performance characteristics of heat exchanger effectiveness, capacity, and pressure drop were evaluated over a range of CO2 gas cooler inlet pressures and temperatures. For the ambient temperature range of 10°C to 30°C, the maximum observed capacities ranged from 4.46 kW to 5.34 kW, with the capacity increasing approximately linearly with increasing ambient temperature. Over this maximum capacity range, the effectiveness of the gas cooler ranged from 98.7% to 99.4%, with the effectiveness increasing with decreasing ambient temperature. The largest gas cooler pressure drop was approximately 130 kPa at a volumetric flow rate of 128 cm3/s, which is the flow rate resulting from the optimum system operating conditions at an ambient temperature of 30°C.

A Dynamic Test Facility for Mobile Air Conditioning Systems

Amr Gado,Yunho Hwang,Reinhard Radermacher 대한설비공학회 2007 International Journal Of Air-Conditioning and Refr Vol.15 No.4

Mobile air conditioning systems work under widely changing operating conditions. To understand the system behavior under such dynamic conditions, a test facility that can impose transient loads as well as conducting dynamic measurements is needed. To test mobile air conditioning systems including their dynamic performance under various drive cycle patterns without using full scale vehicles in a wind tunnel, a new test facility, called "dynamic simulator," is described. It can replicate real vehicle operating conditions by interacting with the system being tested based on the measured system performance and subsequently adjusting the air properties returning to the test system based on the results of a numerical cabin model. A new dynamic simulator has been designed, constructed, and verified for performing dynamic tests. It was successful in controlling the temperature and relative humidity of the air returning to the test unit within ± O.7℃ and ± 4% of their respective intended values. The verification test under the New European Driving Cycle demonstrated that detailed transient behavior of the mobile air conditioning system could be measured by using this dynamic simulator.

$CO_2$ Transcritical Cycle Research at CEEE

Hwang, Yun-Ho,Radermacher, Reinhard 대한설비공학회 2002 설비저널 Vol.31 No.7

1991년에 Maryland 대학에 Dr. Reinhard Rader-macher에 의해 환경에너지공학연구소(CEEE)가 설립되었다. 이 연구소는 환경 및 경제적인 관점에서 에너지 변환 시스템을 개발하는데 선두적인 역할들 수행해왔다. 환경 에너지 공학 연구소는 산업체, 정부,및 연구소에서 지원 받는 컨소시엄 형태의 연구 센터이다. 대체 냉매, $CO_2$초월임계 사이클에 관한 연구를 1993년에 시작한 이래, 현재 세계적으로 40여 개의 회사가 지원을 하고 있다. 2단 압축 $CO_2$ 사이클 최적화, 초월 임계 사이클에서의 오일에 따른 열전달 영향, 초월$CO_2$임계 시스템에서의 오일 정체, $CO_2$압축기 모델링, 자동차에서의 $CO_2$기후 조절 시스템, $CO_2$냉매를 이용한 에어컨, $CO_2$저온 냉동 시스템 등에 관한 연구를 수행하고 있다. CEEE는 향후 연구로 구성요소 및 시스템 최적화, 효율향상, 시스템 적용확대에 관한 연구를 할 예정이다. 센터는 보고서, 컨소시엄 미팅. 워크샵, 교과목 개설, 당문 연구자 초청들을 통해 산업계 및 기술을 전달하고 있다. 본 고에서는 환경에너지 공학 연구소에서 $CO_2$ 초월임계 사이클에 초점을 맞추어 연구소의 연구활동을 기술한다.

A New Variable Refrigerant Flow System Simulation Approach in EnergyPlus

Xiaojie Lin,Hoseong Lee,Yunho Hwang,REINHARD RADERMACHER,Byung-Soon Kim 대한설비공학회 2016 International Journal of Air-Conditioning and Refr Vol.24 No.1

A variable refrigerant °ow (VRF) system is widely applied to build air conditioning systems. Literature review of previous VRF modeling studies was conducted, and it was found that the current calculation approach in EnergyPlus can result in more than 20% deviation in both heat transfer capacity and power consumption. Therefore, a new VRF model is proposed in this study, which includes an improved thermal zone distribution concept, new indoor unit types, and a new thermodynamic model. The developed model is validated with experimental data within 10% in heat transfer capacity and 5% in power consumption. Based on the proposed model, the operation control strategy is also discussed. The results show that the proposed model could also simulate the current control strategy in the VRF system.

COMPACT BRAZED PLATE HEAT EXCHANGERS FOR $CO_2$ HEAT PUMP WATER HEATERS

Leighton, Daniel,Hwang, Yun-Ho,Radermacher, Reinhard The Society of Air-Conditioning and Refrigerating 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.4

The plate-type heat exchanger is found to be well suited for the application of a transcritical $CO_2$ heat pump water heater. A $CO_2$ heat pump water heater test facility was used to evaluate the performance of a high-pressure plate-type heat exchanger. The performance characteristics of heat exchanger effectiveness, capacity, and pressure drop were evaluated over a range of $CO_2$ gas cooler inlet pressures and temperatures. For the ambient temperature range of $10^{\circ}C$ to $30^{\circ}C$, the maximum observed capacities ranged from 4.46kW to 5.34 kW, with the capacity increasing approximately linearly with increasing ambient temperature. Over this maximum capacity range, the effectiveness of the gas cooler ranged from 98.7% to 99.4%, with the effectiveness increasing with decreasing ambient temperature. The largest gas cooler pressure drop was approximately 130 kPa at a volumetric flow rate of 128 $cm^3/s$, which is the flow rate resulting from the optimum system operating conditions at an ambient temperature of $30^{\circ}C$.

A Dynamic Test Facility for Mobile Air Conditioning Systems

Gado, Amr,Hwang, Yun-Ho,Radermacher, Reinhard The Society of Air-Conditioning and Refrigerating 2007 International Journal Of Air-Conditioning and Refr Vol.15 No.4

Mobile air conditioning systems work under widely changing operating conditions. To understand the system behavior under such dynamic conditions, a test facility that can impose transient loads as well as conducting dynamic measurements is needed. To test mobile air conditioning systems including their dynamic performance under various drive cycle patterns without using full scale vehicles in a wind tunnel, a new test facility, called "dynamic simulator," is described. It can replicate real vehicle operating conditions by interacting with the system being tested based on the measured system performance and subsequently adjusting the air properties returning to the test system based on the results of a numerical cabin model. A new dynamic simulator has been designed, constructed, and verified for performing dynamic tests. It was successful in controlling the temperature and relative humidity of the air returning to the test unit within ${\pm}0.7^{\circ}C$ and ${\pm}4%$ of their respective intended values. The verification test under the New European Driving Cycle demonstrated that detailed transient behavior of the mobile air conditioning system could be measured by using this dynamic simulator.

Performance investigation on solid desiccant assisted mobile air conditioning system

Lee, Hoseong,Lin, Xiaojie,Hwang, Yunho,Radermacher, Reinhard Elsevier 2016 Applied thermal engineering Vol.103 No.-

<P><B>Abstract</B></P> <P>In the conventional mobile air conditioning system, the temperature and humidity control is achieved by a vapor compression system. This system cools the air down to lower than the dew point temperate of the cabin to control the humidity. Thus, reheating of the air is necessary. These two factors could increase the fuel consumption of the system. To overcome these issues, a solid desiccant assisted mobile air conditioning system is proposed and investigated. The desiccant assisted technology can separate the latent heat load from the sensible heat load, which will effectively increase the evaporating temperature and reduce the power consumption of the compressor. It is proposed to apply the solid desiccant to the mobile air conditioning system to handle most of latent load, while the vapor compression cycle handles the remaining latent load and sensible load. The model of the proposed concept is developed and validated with experimental data. Lastly, the possible configurations of the solid desiccant assisted mobile air conditioning system are discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A solid desiccant assisted MAC system is proposed and investigated. </LI> <LI> The developed model is validated with experimental data. </LI> <LI> The proposed system reduced the power consumption by 26.3%. </LI> <LI> Possible system configurations of the solid desiccant assisted MAC are discussed. </LI> </UL> </P>

Review article: Numerical simulation of adsorption heat pumps

Pesaran, Alireza,Lee, Hoseong,Hwang, Yunho,Radermacher, Reinhard,Chun, Ho-Hwan Elsevier 2016 ENERGY Vol.100 No.-

<P><B>Abstract</B></P> <P>The primary advantages of the AHP (adsorption heat pump) including using environmentally friendly working fluids and their capability of using low-grade waste heat as their primary driving energy have raised a great deal of attention in recent years. In this work, computer models of AHPs and the latest relevant findings are reviewed since the performance of an AHP system greatly depends on the coupled heat and mass transfer rates inside the adsorbent bed and the design parameters of the adsorber. The nonlinearity of the coupled heat and mass transfer equations makes the qualitative analysis of such systems difficult and hence many researchers have proposed various models to predict the performance of the system and optimize the design parameters to boost the performance. The available models in the literature have been categorized into thermodynamic models, lumped-parameter models, and distributed-parameter (heat and mass transfer) models. The results of the literature review indicate that recent numerical modeling of AHPs relies on the distributed-parameter models. Majority of the modeling works are focused on validating the proposed model and used the model to optimize the adsorber design parameters and operating conditions of the system. Based on the literature review, some potential future research areas are suggested.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Reviewed different types of models to predict the adsorption heat pump performance. </LI> <LI> Distributed-parameter models are identified as the most accurate models. </LI> <LI> Linear driving force model is widely used for the internal mass transfer resistance. </LI> <LI> Darcy's law is widely used for the external mass transfer resistance. </LI> </UL> </P>