• Title/Summary/Keyword: Cascade Heat Exchanger

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Experimental Study on the Cooling and Heating Operation Characteristics of a Sea Water Source Heat Pump (해수열원 히트펌프 시스템의 냉난방 운전 특성에 관한 실증 연구)

  • Kim, Ji-Young;Baik, Young-Jin;Chang, Ki-Chang;Ra, Ho-Sang
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.544-549
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    • 2009
  • The purpose of this study is to investigate the field Operation Characteristics of a sea water heat source cascade heat pump system and system applicable to Building. Cascade heat pump system is composed R410A compressor, R134a compressor, EEV, cascade heat exchanger, Plate heat exchanger etc. Building area is $890m^2$ and has five floors above ground. R410A is used for a low-stage working fluid while R134a is for a high-stage. The system could runs at dual mode. One is mode of general R410A refrigeration cycle in summer and the other is cascade cycle. In order to gain a high temperature supply water in winter season, the system is designed to perform a cascade cycle. The filed test results show that the sea water heat source heat pump system exhibits a COP of about 5.5 in cooling mode along with a heating COP of about 4.0 in 1-stage heating mode. Cascade 2-stage heat pump system is enough to supply $60^{\circ}C$ water and heating COP is about 3.0

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Mass flow rate ratio analysis for optimal refrigerant charge of a R744 and R404A cascade refrigeration system (R744-R404A 캐스케이드 냉동시스템의 최적 냉매 충전을 위한 질량유량비 분석)

  • Oh, Hoo-Kyu;Son, Chang-Hyo;Jo, Hwan;Jeon, Min-Ju
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.6
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    • pp.575-581
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    • 2013
  • In this paper, the influences of several factors, such as subcooling, superheating degree, internal heat exchanger efficiency, and etc. to the optimal amount of refrigerant charge are investigated for the case of R744-R404A cascade refrigeration system. Refrigerants used in the cascade refrigeration system are R404A in high temperature cycle and R744 in the low temperature cycle. The main results are summarized as follows : The mass flow rate ratio decreases with increasing subcooling, superheating degree and internal heat exchanger efficiency in the high temperature cycle, and evaporating temperature and compression efficiency in the low temperature cycle. And the mass flow rate ratio decreases with decreasing temperature difference of cascade heat exchanger and evaporating, condensing temperature in the high temperature cycle, and subcooling, superheating degree and internal heat exchanger efficiency in the low temperature cycle.

Performance Analysis of Cascade Refrigeration System with Respect to Refrigerants Appling to High Temperature Cycle (고온측 냉매에 따른 이원 냉동시스템의 성능 분석)

  • Yoon, Jung-In;Jeon, Min-Ju;Son, Chang-Hyo
    • Journal of Power System Engineering
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    • v.21 no.3
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    • pp.45-50
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    • 2017
  • This paper presents the Coefficient of performance(COP) and mass flow ratio of cascade refrigeration system with respect to refrigerants appling to high temperature cycle. The operating parameters considered in this study include degree of superheating and subcooling, compressor efficiency, evaporating temperature, condensing temperature and internal heat exchanger effectiveness in high temperature cycle. The result of this study is as follows : The COP of cascade system increases with increasing degree of superheating and subcooling, compressor efficiency and internal heat exchanger effectiveness except increasing condensing temperature. The mass flow ratio of low and high temperature cycle increases with increasing evaporating temperature and condensing temperature, but decreases with increasing internal heat exchanger effectiveness, degree of superheating and subcooling. Also, the mass flow ratio has no correlation with compressor efficiency at high temperature cycle.

Study on the Performance of a Cascade Heat Pump with Two-stage Water Heating Process (2단 승온 캐스케이드 히트펌프의 성능 특성에 관한 연구)

  • Jang, Hanbyeoul;Choi, Jong Min
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.12 no.4
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    • pp.27-32
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    • 2016
  • It is estimated that only heating and cooling take about one third of the total energy consumption worldwide. However, the conventional heating and cooling systems have low efficiencies. Also, boilers and electric heaters that are mostly used to generate both domestic and industrial hot water are inefficient and high energy consumers. For this reason, cascade heat pumps which are known to be very energy efficient and have less environmental impact are being promoted to replace conventional heating, cooling and hot water systems. In this study, a newly designed cascade heat pump by two-stage water heating method has been experimentally investigated. By adopting the auxiliary heat exchanger, the performance of the system was increased. The performance enhancement rate of the system could be maximized by adjusting the low stage compressor speed rather than the high stage compressor speed. The performance of the system with the auxiliary heat exchanger was enhanced by 16.5%.

Study on the Performance of a Variable Speed Cascade Heat Pump under Various Operating Conditions (운전조건에 따른 가변속 캐스케이드 열펌프의 성능 특성 연구)

  • Jeong, Kwangmoo;Choi, Jong Min
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.9 no.2
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    • pp.1-7
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    • 2013
  • Most researches done on heat pumps have been on heat pumps for refrigeration, cooling and heating. There is therefore the need for more research on hot water heat pumps, especially for high temperature. Even though the cascade heat pump cycle has a great potential more efficient hot water generation even at low evaporating temperatures, it has been researched least for this purpose. In this study, the heating performance of a variable speed cascade heat pump was investigated by varying operating conditions. For the same heating capacity values, it was found that increasing the low stage compressor speed was more suitable for enhancing the performance of the system to get a higher temperature.

Performance Simulation of a R744-R717 Cascade Refrigeration System According to Operating Conditions (R744-R717 캐스케이드 냉동시스템에서 운전조건 변화에 따른 성능 해석)

  • Ryu, Jiho;Cho, Honghyun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.10
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    • pp.497-505
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    • 2015
  • The evaporating temperature range required for the low temperature freezing system is from $-50^{\circ}C$ to $-30^{\circ}C$. Since it is difficult to keep the required capacity in a cabinet, it is advantageous to design the system using a cascade refrigeration system. Use of carbon dioxide and ammonia would be advantageous since ammonia is an environment-friendly working fluid and has a high capacity for performance improvement. To investigate the performance characteristics of the R744-R717 cascade refrigeration system, a theoretical model was developed and performance was analyzed according to cascade heat exchanger operating temperature. The optimal cascade R744 condensing temperature was $-5^{\circ}C$, and maximum COP was 1.13 when the temperature difference of the cascade heat exchanger was $5^{\circ}C$. In addition, the total system COP increased by 1.17 when the cascade temperature gap was $3^{\circ}C$ at the middle temperature of $-7.5^{\circ}C$.

A Study on Operating Characteristics of Heat Pump System Using Sea Water Sources (해수온도차에너지이용 냉난방시스템 운전특성에 관한 연구)

  • Chang, Ki-Chang;Baik, Young-Jin;Yoon, Hyung-kee;Ra, Ho-Sang
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.422-425
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    • 2009
  • A sea water source cascade heat pump was designed and tested in this study. The system was designed to perform a single stage operation in summer, as well as a cascade operation in winter to ensure the high temperature lift. A steady-state simulation model was developed to analyze and optimize its performance. The simulation results show that the R717 exhibits best performance among combinations considered in this study. A R410A also exhibits the highest performance among HFCs with the smallest compressor displacement. A 15-RT R410A-R134a pilot system was installed in the 5-story commercial building at Samcheok City by the East Sea. A scroll type R410A compressor, a reciprocating type R134a compressor, plate type condenser/evaporator/ cascade heat exchanger and two electronic expansion valves were used to build a pilot. A titanium plate type heat exchanger is also used for the heat exchanging with a sea water. The heat source/sink water is supplied from the well below the seashore in the depth of 5 m. In the initial test of the system, supply water temperature was rising up to $67^{\circ}C$ using a sea water heat source of $9^{\circ}C$, while an ambient temperature was $4.5^{\circ}C$.

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The Operation Characteristics of a Sea Water Source Heat Pump System (해수열원 히트펌프 시스템의 운전특성)

  • Chang, Ki-Chang;Baik, Young-Jin;Ra, Ho-Sang;Kim, Ji-Young;Lee, Jae-Hoon
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.1353-1357
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    • 2008
  • A sea water source cascade heat pump was designed and tested in this study. The system was designed to perform a single stage operation in summer, as well as a cascade operation in winter to ensure the high temperature lift. A steady-state simulation model was developed to analyze and optimize its performance. The simulation results show that the R717 exhibits best performance among combinations considered in this study. A R410A also exhibits the highest performance among HFCs with the smallest compressor displacement. A 15-RT R410A-R134a pilot system was installed in the 5-story commercial building at Samcheok City by the East Sea. A scroll type R410A compressor, a reciprocating type R134a compressor, plate type condenser/ evaporator/ cascade heat exchanger and two electronic expansion valves were used to build a pilot. A titanium plate type heat exchanger is also used for the heat exchanging with a sea water. The heat source/sink water is supplied from the well below the seashore in the depth of 5 m. In the initial test of the system, supply water temperature was rising up to $67^{\circ}C$ using a sea water heat source of $9^{\circ}C$, while an ambient temperature was $4.5^{\circ}C$.

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A Design and Test of a Sea Water Source Heat Pump System (해수열원 히트펌프 시스템의 설계 및 운전)

  • Lee, Jae-Hun;Kim, Ji-Young;Baik, Young-Jin;Chang, Ki-Chang;Ra, Ho-Sang;Shin, Kwang-Ho
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.1273-1278
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    • 2008
  • A sea water source cascade heat pump was designed and tested in this study. The system was designed to perform a single stage operation in summer, as well as a cascade operation in winter to ensure the high temperature lift. A steady-state simulation model was developed to analyze and optimize its performance. The simulation results show that the R717 exhibits best performance among combinations considered in this study. A R410A also exhibits the highest performance among HFCs with the smallest compressor displacement. A 15-RT R410A-R134a pilot system was installed in the 5-story commercial building at Samcheok City by the East Sea. A scroll type R410A compressor, a reciprocating type R134a compressor, plate type condenser/ evaporator/ cascade heat exchanger and two electronic expansion valves were used to build a pilot. A titanium plate type heat exchanger is also used for the heat exchanging with a sea water. The heat source/sink water is supplied from the well below the seashore in the depth of 5 m. In the initial test of the system, supply water temperature was rising up to $67^{\circ}C$ using a sea water heat source of $9^{\circ}C$, while an ambient temperature was $4.5^{\circ}C$.

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Performance Characteristics of New LNG Liquefaction Cycles with Temperature Differences in the Heat Exchangers (열교환기 온도차에 따른 새로운 LNG 액화사이클의 성능 특성)

  • Yoon, Jung-In;Son, Chang-Hyo
    • Journal of Power System Engineering
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    • v.18 no.1
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    • pp.51-56
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    • 2014
  • In this paper, the performance of the $CO_2-C_2H_6-N_2$ cascade liquefaction cycle with respect to temperature differences in the LNG heat exchangers is analyzed theoretically using HYSYS software and then compared the COP(coefficient of performance) of the cascade liquefaction cycles using $C_3H_8-C_2H_4-C_1H_4$ and $CO_2-N_2O-N_2$. In comparison of COP of three cycles, the cascade liquefaction cycles using $C_3H_8-C_2H_4-C_1H_4$ showed the highest COP. And the liquefaction cycle using $CO_2-C_2H_6-N_2$ and $CO_2-N_2O-N_2$ presented the second and third highest COP, respectively. In case of COP, the $C_3H_8-C_2H_4-C_1H_4$ cascade liquefaction cycle yields better COP. But, in terms of the environment and maintain, it is confirmed that the cascade liquefaction cycle using $CO_2-C_2H_6-N_2$ provides favorable characteristics.