• Title/Summary/Keyword: 이단압축

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Performance of Carbon Dioxide System for Freezing and Refrigeration (이산화탄소를 이용한 냉동·냉장 시스템의 성능연구)

  • Kim, Yoonsup;Yun, Rin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.2
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    • pp.81-86
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    • 2015
  • Performance of freezing and refrigeration systems in supermarket, which utilized $CO_2$ as a refrigerant, was investigated by using the Pack Calculation II. The configuration of simulated systems was basic parallel refrigeration system, cascade system, and two-stage system. The $CO_2$ cascade system showed higher COP than basic parallel R404A system by 13% for MT and 62% for LT, respectively. Among the $CO_2$ cascade systems, R717(MT)-$CO_2$(LT) showed the highest performance. Open-type intercooler method showed higher performance than liquid injection for the two-stage $CO_2$ systems.

Experimental Study on Compression/Absorption High-Temperature Hybrid Heat Pump with Natural Refrigerant Mixture (천연혼합냉매를 이용한 압축/흡수식 고온히트펌프의 실험적 연구)

  • Kim, Ji-Young;Park, Seong-Ryong;Baik, Young-Jin;Chang, Ki-Chang;Ra, Ho-Sang;Kim, Min-Sung;Kim, Yong-Chan
    • 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.

Comparison of Molding Characteristics for Multi-cavity Molding in Conventional Injection Molding and Injection Compression Molding (다수 개 빼기 성형에서 일반사출성형과 사출압축성형의 성형특성 비교)

  • Lee, Dan Bi;Nam, Yun Hyo;Lyu, Min-Young
    • Polymer(Korea)
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    • v.38 no.2
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    • pp.144-149
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    • 2014
  • Large residual stresses are remained in the conventional injection molded products because of the high cavity pressure in packing phase during injection molding process. Conventional injection molding (CIM) invokes distribution of cavity pressure and it has a limitation to obtain product with uniform physical property. Multi-cavity conventional injection molding contains quality deviation among the cavities since flow imbalance occurs during filling phase. Injection compression molding (ICM) is adopted to overcome these limitations of CIM. In this study, molding characteristics of CIM and ICM have been investigated using multi-cavity injection mold. Researches were performed by both experiment and computer simulation through observations of birefringence for transparent resins, polycarbonate and polystyrene in CIM and ICM. As a result, low and uniform birefringence and mold shrinkage were showed in the specimens by ICM that could give a uniform cavity pressure. Deviation of physical property among the specimens in multi-cavity mold shown in CIM was significantly reduced in the specimens by ICM. Through this study it was concluded that the ICM in multi-cavity molding was valid for molding products with uniform property in an individual cavity and also reduced property deviation among the cavities.

Experimental Study on Optimization of Absorber Configuration in Compression/Absorption Heat Pump with NH3/H2O Mixture (NH3/H2O 혼합냉매를 사용한 압축/흡수식 히트펌프 시스템의 흡수기 최적화에 관한 실험적 연구)

  • Kim, Ji-Young;Kim, Min-Sung;Baik, Young-Jin;Park, Seong-Ryong;Chang, Ki-Chang;Ra, Ho-Sang;Kim, Yong-Chan
    • 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.

Comparison of System Performances of Hot-gas Bypass and Compressor Variable Speed Control of Water Coolers for Machine Tools (핫가스 바이패스 및 압축기 가변속 제어에 의한 공작기계용 수냉각기의 성능 비교)

  • Jeong, Seok-Kwon;Lee, Dan-Bi;Yoon, Jung-In
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.1
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    • pp.1-8
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    • 2012
  • Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a cooler system to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the water cooler system. In this paper, comparisons of system performances according to the control schemes in a cooler for machine tools were conducted in detail. Each proportional-integral feedback controller for the two different control systems is designed. The system performances, especially the temperature control accuracy and coefficient of performance which is a criterion of energy saving, were mainly analyzed through various experiments using 1RT water cooler system with different two types of control scheme. These evaluations will provide useful information to choose suitable water cooler system for the engineers who design controllers of the cooler system for machine tools.

Comparative Research on the Carbon Dioxide Liquefaction Using Several Refrigerants (몇 가지 냉매를 사용한 이산화탄소 액화에 대한 비교 연구)

  • ILSU PARK;PHILSUNG HWANG;KICHEOL JUNG;JUNESHU ANH;JUNGHO CHO
    • Journal of Hydrogen and New Energy
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    • v.34 no.2
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    • pp.226-233
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    • 2023
  • In this study, we compared the performance of several refrigeration cycles using different refrigerants and utilizing the cold heat of liquefied natural gas (LNG) for the liquefaction of carbon dioxide. The final conditions for the liquefied CO2 were set to -20℃ and 20 bar. The refrigerants used included R404a, ammonia, propane, and propylene using a vapor recompression refrigeration cycle. For the refrigeration cycle, the CO2 at room temperature and pressure was compressed in a two-stage compression process with an intermediate cooling stage using a refrigeration unit. To compare with the liquefaction process using refrigeration, we compressed the CO2 to 8 bar in a single compression stage and cooled it to around -50℃ using the cold heat of the LNG before liquefying it. Results showed that using ammonia as the refrigerant required the least amount of compressor power for the liquefaction process, and the heat transfer area of the evaporator was the smallest when using propylene as the refrigerant. Using the cold heat of LNG instead of refrigeration using R404a resulted in approximately 69% less energy consumption.

Preparation and Application Characteristics of Carboxylated Styrene Butadiene Latex for Latex Modified Concrete (라텍스 개질 콘크리트용 Carboxylated Styrene Butadiene 라텍스의 제조와 적용 특성)

  • Lee, Bong-Kyu;Ju, Chang-Sik
    • Korean Chemical Engineering Research
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    • v.50 no.6
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    • pp.1076-1081
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    • 2012
  • For the purpose of development of the latex suitable for latex modified concrete, experimental researches on the preparation of carboxylated styrene butadiene latex by the method of the two-step emulsion polymerization and application to concrete were performed. Sodium dodecylbenzene sulfonate and sodium salt of lauryl sulfonate were selected as anionic emulsifiers, and nonylphenoxy poly(ethyleneoxy) ethanols (n=10, 20, 40) as latex stabilizer. Potassium persulfate and sodium bisulfite were used as redox initiator, besides $Na_2HPO_4$ and $K_2CO_3$ as electrolytes. Polymerization recipe of latex suitable for latex modified concrete were suggested from the experimental researches on the effects of anionic emulsifiers and their concentration on the polymerization stability, and the effect of electrolytes concentration on the particle size of latex. Physical properties, such as slump, air contents, compressive and flexural strength, of latex prepared by suggested polymerization recipe were examined. The experimental results showed that latex modified concrete satisfied the quality standards in slump and air contents. Furthermore, it was turned out that the compressive and the flexural strength of latex modified concrete with 28 days curing time showed appreciably improvements.

Effects of Melt-blending Condition and Additives on Mechanical Properties of Wood/PP Composites (용융혼합 조건과 첨가제가 목분/폴리프로필렌 복합체의 기계적 특성에 미치는 영향)

  • Ahn, Seong Ho;Kim, Dae Su
    • Polymer(Korea)
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    • v.37 no.2
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    • pp.204-210
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    • 2013
  • Effects of additives (lubricant and antioxidant) and melt-blending condition (temperature, time and rotor speed) on the mechanical properties of polypropylene-based wood polymer composites (WPCs) were investigated. WPCs were prepared by melt-blending followed by compression molding. To understand melt-blending procedure, torque change of the WPC melt-blend was monitored. Maleic anhydride modified PP and nanoclay were used as a compatibilizer and a reinforcing filler, respectively. UTM and izod impact tester were used to measure the mechanical properties of the WPCs and a color-difference meter was used to measure the discoloration of the WPCs according to melt-blending condition. The mechanical properties showed that the optimized melt-blending condition was $170^{\circ}C$, 15 min, and 60 rpm. The mechanical properties of the WPCs decreased with increasing lubricant and antioxidant content. The two step method, adding wood flour later separately during melt-blending, was more effective than the typical one step method for improving the mechanical properties of the WPCs.