• Journal of Power System Engineering
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• v.16 no.1
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• pp.38-43
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• 2012

This paper describes an analysis on performance of R744-R404A cascade refrigeration system with internal heat exchanger to optimize the design for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, internal heat exchanger and compression efficiency, evaporating and condensing temperature in the R744 low- and R404A high-temperature cycle and temperature difference of cascade heat exchanger. The main results are summarized as follows : COP of cascade refrigeration system increases with the increasing of compression efficiency, but decreases with the increasing temperature difference of cascade heat exchanger. Also, the COP increases with the increasing of internal heat exchanger efficiency in high-temperature cycle, but decreases with that in low-temperature cycle. Therefore, internal heat exchanger efficiency, compressor efficiency and temperature difference of cascade heat exchanger on R744-R404A cascade refrigeration system have an effect on the COP of this system.

• Solar Energy
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• v.18 no.1
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• pp.69-79
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• 1998

This paper is concerned about the performance of HCFC22 alternative refrigerants used in heat pumps and industrial chillers. A water-to-water breadboard heat pump with counter-current heat exchangers and a hermetic compressor was built to carry out the experiments with various refrigerants. For each test, more than 40 temperatures, 4 pressures, power input, mass flow rates of the heat transfer fluids were measured. Refrigerants tested were HCFC22, R290(Propane), an azeotrope of 45%Propane/55%R134a mixture, and a nonazeotropic mixture of Calor 50. All tests were conducted under ARI test A condition. It is found that the COP and capacity of propane were 18% and 2.5% higher than those of HCFC22 while the COP and capacity of 45%Propane/55%R134a mixture were 3.5% and 5.3% higher than those of HCFC22 respectively. Also the COP and capacity of Calor 50 were 17% and 7.8% higher than those of HCFC22. Compressor discharge temperatures of alternative refrigerants were roughly $35^{\circ}C$ lower than that of HCFC22 indicating that these refrigerants are good from the view point of compressor reliability. The charging amounts for the alternative refrigerants were reduced by 40-60% as compared to that of HCFC22. Overall, it can be said that hydrocarbon containing alternative refrigerants are excellent in thermodynamic performance but should be used with considerable care due to their flammability.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.3
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• pp.94-102
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• 1998

This experiment was carried out to study on the effect of greenhouse heating by water-to-water heat pump system employing heating water tank(ground water) as the heat source. Followings are the results obtained from this study ; 1. The heat amount absorbed from evaporator and the heat amount rejected from condenser were approximately 9, 000~ 12, 000kcal/h and 13, 000~ 17, OOOkcal/h, respectively. 2. The heat efficiencies of evaporator and condenser used in this experiment were approximately 79% and 83%, respectively. 3. The maximum heating load estimated for the experimental greenhouse was about 18, 000 ~ 25, OOOkcal/h, which was found to be about 28 ~ 32% higher than the heating capacity of the heat pump system adopted for this experiment. 4. The coefficients of performance(COP) for the heat pump and the total heat pump system were approximately 2.9~3.5 and 1.5~2.4, respectively. 5. The coefficient of performance(COP) calculated from the Mollier Diagram was about 3.2 ~ 3.4, which was reasonably close to the COP estimated on the basis of measured values. 6. The temperature of experimental greenhouse heated by the heat pump system could be maintained about 12~15 。C higher than that of a control greenhouse.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.11
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• pp.529-534
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• 2014

This research developed a hybrid heat pump system with the functions of dehumidification and heating, which uses simulated air that is like underground air, from an environmental chamber as a heat source. The system consisted of three evaporators and three condensers that were installed in series in the air passage, between the underground and load space. As results, the total amount of dehumidification was 2.726 kg/h, and the heating $COP_h$ was 1.84 at air intake temperature $17^{\circ}C$ and relative humidity 70%, which is a similar condition to underground air. We found that the total amount of dehumidification also increased with the air temperature and humidity. The system $COP_s$ was reached at 2.5, if we include the latent heat of dehumidification in the conventional heat pump system's COP.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.375-380
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• 2014

The purpose of this paper is to investigate the cooling and heating performance of a standalone-type thermoelectric system equipped with a thermoelectric module. The system consists of a blower and two thermoelectric modules with a fin, which is soldered onto both sides of the thermoelectric module and a courtesy light. The thermoelectric system experiment is conducted with the intake voltage to find the optimum cooling and heating performance of each. The results showed that the cooling capacity and coefficient of performance (COP) were 22 W and 0.31, and the heating capacity and COP were 147 W and 1.1, respectively. In the vehicle cooling and heating performance test in a climate wind tunnel, the results showed that the standalone thermoelectric system's cooling performance was slightly better than the base system; and the heating performance of the standalone thermoelectric system was $54.1^{\circ}C$ and the COP was 1.3, compared to the base system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7736-7744
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• 2015

Considering the significant waste of industrial energy, effective use of low temperature waste heat is extremely important. In this study, a heat pump cycle with double effect and double stage was realized, which escalates the hot water temperature from $50^{\circ}C$ to $70^{\circ}C$ using $160^{\circ}C$ high temperature heat source and $17^{\circ}C$ low temperature heat source. The steam generated in the first generator condenses in the first condenser generating steam in the second generator. The steam condenses in the second condenser and is provided to the second evaporator. Part of the water out of the second evaporator is supplied to the first evaporator, which evaporates using low temperature waste heat. The evaporated steam enters the first absorber and the second evaporator. The steam out of the second evaporator is absorbed into the solution at the second absorber. The hot water temperature is raised in the second condenser and in the second absorber. Proper flow rates and UA values, which satisfied temperature lift $20^{\circ}C$ and COP 1.6, were deduced through trior and error. The COP increases as the temperature of the high temperature water increases, hot water temperature decreases and flow rate increases, waste water temperature and flow rate increases, solution circulation rate decreases. On the other hand, the temperature rise of the hot water increases as the temperature of the high temperature water increases, hot water temperature increases and flow rate decreases, waste water temperature and flow rate increases, solution circulation rate increases. In addition, the COP and hot water temperature rise increase as UAs of the heat exchangers increase.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.1
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• pp.75-82
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• 2014

PURPOSE: PURPOSE: The purpose of this study was to analyze the effect and examine the feasibility of an intervention of ankle strategy exercise on balance of patients with hemiplegia. METHODS: The subject were randomly allocated to three groups: ankle strategy exercise (group A), balance exercise (group B) and control (group C). Group A was received the conventional physical therapy plus ankle strategy exercises for 20 minutes in one session. Group B was received the same conventional physical therapy plus balance exercises for 20 minutes in one session. Two active groups were performed in the session 3 times a week, for a total of 6 weeks. and Group C was only received the same conventional physical therapy. Balance test was assessed using center of pressure (COP) in the anteroposterior (A-P), mediolateral (M-L) direction, Berg balance scale (BBS) and Timed Up and Go Test (TUG). RESULTS: All groups showed improvements in balance parameters. In especial, the Group A was statistically significant differences in almost part evaluation items and showed more improvements in BBS and TUG parameters than Group B and Group C. and moving distance of M-L COP was more improvements than Group B. CONCLUSION: Ankle strategy exercises had more influence on balance than balance exercises and neurodevelopmental treatment.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.159-164
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• 2000

In this paper a new type refrigerant liquid subcooling system which adopts ice storage system is proposed. And the cycle characteristicso of a new system was investigated. Since this system subcools a refrigerant in the daytime using the ice storaged by electric power in the night it is high efficiency heat pump system which have the merit of ice storage system and possible to improve the performance of the heat pump. The running to storage the ie was carried out for 10 hours in the night and th evaporating temperature was set on $-5^{\circ}C.$ Subcooling operation stayed as 430^{\circ}C$ subcooling degree and perfomed till the water in the IST(Ice storage tank) was reached $12^{\circ}C$. The experimental result showed that a new system was superior to the existing refrigeration system generally. The total cooling capacity of a new system was about 11% higher than that of the existing refrigeration system. And the COP of a new system was improved by 22% compared to the existing refrigeration system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.400-405
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• 2011

This paper presents the heating performance characteristics of the air source heat pump with air to water type. The heating capacity, COP, P-h diagram were measured at various operating conditions, air-side temperatures, relative humidities, and inlet/outlet water temperature under the standard heating condition of KS B 6275. The experimental data for the heat pump were measured using the air-enthalpy calorimeter and the constant temperature water bath. As the air-side temperature increases, the heating capacity and COP increase. The effect of the air-side relative humidities on the heat pump performance is insignificant. The heat pump performance on inlet and outlet water temperatures and air-side temperatures(-7, -11, $-15^{\circ}C$) were studied. Heating capacity and COP increased about 27~39% with the air-side temperature increasing. Enthalpy between the front and the rear of condenser decreased about 6% by increasing of the inlet water temperature. These results can be utilized in the design of the air source heat pump system with air to water type.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.1
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• pp.7-14
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• 2017

This study carried out a numerical analysis of the effects of hot waste water supply on the performance of a Type II absorption heat pump. There are two types of hot waste water supply, regular series flow and reverse series flow. Also it investigated the interaction between each type of flow and heat exchange solutions. As the effectiveness of heat exchange solutions increase, the steam generation and (COP) increase as well. If the effectiveness of a heat exchange solution is lower than 0.566, the steam generation rate of the reverse flow is lower than that of the regular series flow. A high effectiveness of heat exchange solution is therefore required to make a larger amount of steam in reverse series flow than with ordinary series flow. The COP difference between the two types of flow decreases with the increasing effectiveness of the heat exchange solution. Thus, a reverse flow type absorption heat pump can match the high steam generation rate and COP of the ordinary flow type when a highly effective heat exchange solution is applied.