• Title/Summary/Keyword: Heating cycle

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Studies for Processing Condition Optimization and Physicochemical Property of Resistant Starch (난소화성 전분 제조공정의 최적화 및 이화학적 특성 연구)

  • 한명륜;김우경;강남이;이수정;김명환
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.32 no.8
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    • pp.1193-1199
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    • 2003
  • As a result of resistant starch yield depending on heating temperature, moisture content, storage temperature and heating-cooling cycle with RSM (response surface methodology), high amylose corn starch (46%) was appeared higher than normal corn starch in the yield (22%). At the high amylose corn starch, optimum conditions for resistant starch formation were 6 times of heating-cooling cycle, 108$^{\circ}C$ heating temperature and 67% moisture content at the 2$0^{\circ}C$ storage temperature, which resulted in 25% yield with these experiment conditions. Affecting factor for the resistant starch formation was arranged according to heating -cooling cycle, moisture content, heating temperature and storage temperature. Raw corn starch granule was destructive and appeared a porous reticular structure by the resistant starch formation. Color became dark and increased yellowness by caramelization during heating processing. Heating-cooling processing was the result of decreased hardness, cohesiveness, springiness and gumminess.

Optimal Operation Model of Heat Trade based District Heating and Cooling System Considering Start-up Characteristic of Combined Cycle Generation (가스터빈 복합발전의 기동특성을 고려한 열거래 기반 지역 냉난방 시스템의 최적 운영 모델)

  • Kim, Jong-Woo;Lee, Ji-Hye;Kim, Hak-Man
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.11
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    • pp.1610-1616
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    • 2013
  • Recently, district heating and cooling (DHC) systems based on combined cycle generation (CCG) providers are increasing in Korea. Since characteristics of combined heat and power (CHP) generators and heat demands of providers, heat trading between DHC providers based on the economic viewpoint is required; the heat trading has been doing. In this paper, a mathematical model for optimal operation based on heat trading between DHC providers is proposed. Especially, start-up characteristic of CCG is included. The operation model is established by mixed integer linear programming (MILP).

Simulation on a Residential Heat Pump System Using $CO_2$ (이산화탄소를 적용한 주거용 냉난방 겸용 열펌프 시스템의 시뮬레이션)

  • 조홍현;이무연;김용찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.12
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    • pp.987-995
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    • 2003
  • The performance of a residential heating and cooling system with $CO_2$ is predicted by using a cycle simulation model. The simulations are conducted by varying design parameters and operating conditions. The efficiency of the transcritical cycle can be improved by utilizing the advantages in heat transfer characteristics of $CO_2$ and developing microchannel indoor and outdoor heat exchangers. For the designed system of this study, the predicted COP of the heat pump system is approximately 3.5 in the heating mode and 3.0 in the cooling mode. The predicted optimal discharge pressure for the heat pump system is approximately 11 MPa in the heating mode and 9 MPa in the cooling mode.

Analysis of Life Cycle Cost for Heat Source Equipments in Buildings for Adolescent Trainees (청소년 수련관의 열원설비 대안별 생애주기 비용에 관한 연구)

  • Ahn, Chang-hwan;Pang, Seung-ki;Baik, Yong-gyu
    • KIEAE Journal
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    • v.5 no.3
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    • pp.25-31
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    • 2005
  • Computer simulations were performed for Heating Ventilating and Air-Conditioning (HVAC) systems to figure out more efficient maintenance methods for the building used for adolescent trainees. This study aims at suggesting design alternatives for optimum operation and performing life cycle cost (LCC) for each alternative. First, the capacity of the heat source equipment was determined using annual maximum heating and cooling loads. Annual loads were calculated and applied to the alternative for the purpose of calculating annual energy cost. Second, several types of data were collected to predict energy cost. Finally, the pay back period for each alternative was calculated using total cost estimation during standard duration period. This study indicates that the absorption chiller that does not occupy most part of a mechanical room, and does not need much operation cost was most economical.

Experimental Studies on the Performance of a Transcritical Cycle for Hot Water Heating Using Carbon Dioxide (이산화탄소를 이용한 온수급탕용 초월임계사이클의 성능에 대한 실험적 연구)

  • 김성구;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.6
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    • pp.461-470
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    • 2003
  • The purpose of this study is to investigate the performance of a transcritical cycle for hot water heating using $CO_2$ as a working fluid. Some of the main parameters that affect the practical performance of the $CO_2$ system are discussed; the performance on the variation of refrigerant charge, changes in flow conditions of secondary fluids, and that with or without internal heat exchanger, The experimental results show that the optimum charge is approximately the same for various mass flow rates of the secondary fluid at gas cooler. The experimental results on the effect of secondary fluids are in general agreement with the experimental results of transcritical cycle in the open literature and show similar trend for conventional subcritical vapor compression cycles. The heat exchanger effectiveness increases with an increase of the heat exchange area of the internal heat exchanger regardless of the mass flow rate at the gas cooler.

Induction Heating Apparatus for Rapid Heating of Flat-Type Metallic Mold in Hot Embossing (미세 패턴 성형용 판형 금형의 급속 가열을 위한 유도가열기구)

  • Hong, S.K.;Lee, S.H.;Heo, Y.M.;Kang, J.J.
    • Transactions of Materials Processing
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    • v.16 no.4 s.94
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    • pp.282-287
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    • 2007
  • Hot embossing, one of Nanoimprint Lithography(NIL) techniques, has been getting attention as an alternative candidate of next generation patterning technologies by the advantages of simplicity and low cost compared to conventional photolithographies. A typical hot embossing usually, however, takes more than ten minutes for one cycle of the process because of a long thermal cycling. Over the last few years a number of studies have been made to reduce the cycle time for hot embossing or similar patterning processes. The target of this research is to develop an induction heating apparatus for heating a metallic micro patterning mold at very high speed with the large-area uniformity of temperature distribution. It was found that a 0.5 mm-thick nickel mold can be heated from $25^{\circ}C\;to\;150^{\circ}C$ within 1.5 seconds with the temperature variation of ${\pm}5^{\circ}C$ in 4-inch diameter area, using the induction heating apparatus.

Economic Evaluation of the Passive Solar-house Heating System Using the All-glass Evacuated Solar Collector Tubes and the Pebble Bed Heat Storage (자연형 태양열주택 난방시스템의 경제적 평가)

  • Jang, Moon-Ki;Yulong, Zhang;Zailin, Piao;Rhee, Shin-Ho
    • Journal of The Korean Society of Agricultural Engineers
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    • v.50 no.3
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    • pp.43-48
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    • 2008
  • The economics of a passive solar heating system (PSHS) with the pebble bed heat storage was evaluated, and the applications of the PSHS were analyzed, in this study. The results are as follows: The heating load, solar heat gain, and stored heat/year of the PSHS in the solar house model were found to be 10,778MJ, 3,438MJ, and 11,682MJ, respectively. The yearly energy expenses of the PSHS and the alternative heating system (conventional coal heating system, CCHS), which uses coal, were found to be USD 1.60/year and USD 60.90/year, respectively, and the yearly expenses of the PSHS were found to be 38 times less than those of the alternative heating system (CCHS). If it will be supposed that the life cycle of the passive solar heating system, according to the results of the LCC analysis in the two systems, is 40 years, the total expenses for the life cycle of the PSHS and the CCHS will be USD 1,431.50 and USD 2,740.00, respectively. The period for the investment payback of the PSHS is six years.

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.

An Experimental Study on the Performance of a Heat Pump for the Cold Climate (한랭지용 열펌프의 저온난방 성능에 관한 실험적 연구)

  • Ju Jeong-Dong;Bae Kyung-Su;Hwang Young-Kyu;Lee Yun-Yong;Jeong Gyoo-Ha;Oh Sang-Kyong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.1
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    • pp.39-46
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    • 2005
  • The present study concerns an experimental study of a R-22 heat pump system consisted of liquid and liquid heat exchangers. The test was performed for various systems of a single-, tandem-, and two stage-cycle at the same environmental conditions of temperature. Various experiments of the heat pump system were peformed to compare the heating capacity and COP, when the outdoor temperature is near $-15^{\circ}C$ and the indoor temperature is $20^{\circ}C.$ As the results of the present study, the system of Tandem(parallel) cycle showed the best heating performance, while the discharge temperature of refrigerant was too high. In case of the system of two stage cycle, the performance characteristics were significantly improved by employing the inter cooler.

A Study of the Defrosting Control in the Application of Photoelectric Sensors (광센서를 이용한 제상제어 방법에 대한 연구)

  • Jeon, ChangDuk
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.4
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    • pp.167-174
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    • 2017
  • This study attempted to investigate the value of photoelectric sensors in terms of a defrost-control method. Tests were conducted in a calorimeter room under the heating with the defrost-performance test conditions described in KS C 9306. Accordingly, the photoelectric technology is a competitive defrost-control method that can precisely control the operational defrost cycle using the output voltages that are proportional to the frost height. The heating period is gradually reduced because the complex defrost-control method, for which the sensors initiate the defrosting process and the defrosting process is terminated by the time parameter, could not adjust the net defrosting time by itself. Therefore, a complex defrost-control method, for which the photoelectric sensors start the defrosting process and it is terminated by the temperature parameter, is preferred because of the adjustment of the net defrosting time. Regardless of the defrost-control method, the first defrosting cycle is activated earlier than the times that are determined in the second and third cycles and so on, because the first operation cycle can decide the characteristics of the subsequent cycle.