• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.668-672
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• 2009

This is to report the result of Development of Single effect/Double lift absorption chiller & heater which is used in the district heating net work. The heating cycle was newly developed to make the secondary hot water from evaporator and the cycle change-over function was added for the heating to the cooling mode and the cooling to the heating mode. Finally, it was assured through the site trial operation that the outlet temperature of primary hot water can be produced lower than $68^{\circ}C$ when the outlet temperature of secondary hot water is $60^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.41-48
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• 2000

The characteristics of a combined cycle for the production of fresh water and air-conditioning was analyzed. The combined cycle consisted of an open water cycle and a $CO_2$ refrigeration cycle interlinked in the pre-heater of the water cycle, which is the condenser of the refrigeration cycle. The oprating conditions and criteria for the fresh water production and air-conditioning was described and their effects on the total system were evaluated. The results indicated an increase of desalinated water with the increase of hot water temperature, which resulted in the decrease of cooling capacity of the refrigeration system in this study. However, the energy saving correspond to the pre-heating of the water cycle by the condensing of the refrigeration system shows the avilable advantage of the proposed cycle as compared to other single purpose plants for desalination.

• Solar Energy
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• v.18 no.2
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• pp.51-67
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• 1998

In this paper, various solar systems are introduced according to usage pattern considering national weather condition and hot water comsumption pattern. First, basic principle and components of solar hot heater are presented, and then operational machanism of various solar hot water systems are presented according to the case of domestic and industrial use with network of piping.

• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.119-119
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• 2003

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.2
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• pp.82-89
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• 2018

This paper presents a novel prototype of dual mode control based phase shift ZVS PWM high frequency load resonant inverter with lossless snubber capacitors in addition to a single active auxiliary resonant snubber for electromagnetic induction heating(IH) foam metal based consumer fluid dual packs(DPA) heater. The operating principle in steady state and unique features of this voltage source soft switching high frequency inverter circuit topology are described in this paper. The lossless snubber and auxiliary active resonant snubber assisted constant frequency phase shift ZVS PWM high frequency load resonant inverter employing IGBT power modules actually is capable of achieving zero voltage soft commutation over a widely specified power regulation range from full power to low power. The steady state operating performances of this dual mode phase shift PWM series load resonant high frequency inverter are evaluated and discussed on the basis of simulation and experimental results for induction heated foam metal heater which is designed for compact and high efficient moving fluid heating appliance in the consumer pipeline systems.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.81-81
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• 2011

본 연구는 $CO_2$를 냉매로 하는 급탕용 히트펌프 성능특성을 평가하는 시험 평가법에 대하여 국내 실정에 맞는 시험평가법을 개발하기 위한 목적으로 기존 $CO_2$ 급탕용 히트펌프의 평가방법을 분석하고자 한다. 현재 $CO_2$ 급탕기 또는 급탕용 히트펌프 제품은 일본에서 2000년 초반부터 에코큐트라는 제품으로 일본 급탕용 난방기기로 판매되고 2009년을 기초로 누적판매 대수가 150만대에 이르고 있다. 국내에는 2008년 후반부터 공기열원 또는 폐열원 등을 이용한 급탕용 히트펌프 제품이 일부 수입되어 목욕탕, 찜질방과 같은 숙박업소용으로 판매되고 있는 추세이다. 국내에서는 급탕용 열펌프의 제품의 정의가 아직 정립되지 않고 이에 대한 시험평가방법이 전무한 실정이기 때문에 현재 일본의 가정용 열펌프 급탕기의 규격을 토대로 실제 급탕용 열펌프의 시험을 수행하여 급탕용 히트펌프의 급탕성능특성을 평가하는 방법을 개발하고자 한다. 시험시료는 일본에서 판매되고 있는 급탕용 히트펌프(D사) 제품을 이용하였으며, 현재 일본에서 사용하고 있는 JRA4050 규격에 의해 급탕성능평가를 진행하고 급탕성능평가 지표 등을 국내 유사조건과 급탕성능특성의 평가방법을 비교분석하였다.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.119-124
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• 2008

Recently, focus has been drawn on natural refrigerants due to increasing concern on global warming. As a consequence, CO2 systems such as a heat pump water heater using CO2 as a refrigerant are rapidly growing on the market. Currently, rolling piston rotary compressors are widely used for CO2 heating and/or refrigeration systems. There are several ways of realizing gas compression structure. They are single stage compression with single cylinder, single stage compression with two cylinders, and two stage compression with two cylinders. In this paper, computer simulation program which was validated for a single stage rotary compressor with one cylinder has been extended for a single stage, two cylinder rotary type. Numerical investigation has been made on optimal design for the cylinder configuration using the extended simulation program. For a single stage two cylinder rotary compressor having a displacement volume of 4 cc for each cylinder, compressor efficiency has been found to be maximum when the cylinder radius and height are 31mm and 10mm, respectively.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.246-247
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• 2005

The paper presents the heat transfer characteristics during cooling process of carbon dioxide($CO_2$) in a helically coiled tube. The main components of the apparatus consist of a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section with the inner diameter 4.55 [mm] is a tube in tube type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The main results were summarized as follows : The heat transfer coefficient increases with respect to the decrease of the gas cooler pressure in a supercritical region and the increase of the refrigerant mass flux. The pressure drop decreases in increases of the gas cooler pressure and increases with respect to increases the refrigerant mass flux.

• The KSFM Journal of Fluid Machinery
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• v.10 no.2 s.41
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• pp.16-21
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• 2007

Potential advantages of using vapor injection in a two stage rotary compressor for a $CO_2$ heat pump water heater system were addressed in this paper by numerical simulation. Vapor separated from a flash tank in the middle of the expansion process can be used for injection into the second stage suction plenum of the compressor to improve the system performance. Vapor injection increases the intermediate pressure between the two stages, thus increasing the first stage compressor work and reducing that of the second stage. As a whole, however, the compressor input power increases due to injected mass flow rate for the second stage. Computer simulation showed that increment of the cooling capacity by vapor injection exceeded that of the compressor work, thus improving the system performance. COP improvement by vapor injection was calculated to be about 5-14% for normal operating conditions. With vapor injection, a maximum COP was found when the displacement volume of the second stage becomes 90-95% of that of the first stage of the compressor.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.216-221
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• 2005

The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a helically coiled tube were investigated experimentally. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section is a double pipe type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. It was made of a copper tube with the inner diameter of 4.85 [mm], the outer diameter of 6.35 [mm] and length of 10000 [mm]. The refrigerant mass fluxes were 200${\sim}$600 [kg/$m^2$s] and the average pressure varied from 7.5 [MPa] to 10.0 [MPa]. The main results were summarized as follows: The heat transfer coefficient of supercritical $CO_2$ increases, as the cooling pressure of gas cooler decreases. And the heat transfer coefficient increases with the increase of the refrigerant mass flux. The pressure drop decreases in increase of the gas cooler pressure and increases with increase the refrigerant mass flux.