• 제목/요약/키워드: Pre-cooling Time

검색결과 44건 처리시간 0.029초

저온진공기술을 이용한 예냉 및 해동 겸용장치에 관한 연구 (A Study on the Combined Equipment for the Pre-cooling and the Thawing using the Low Temperature Vacuum System)

  • 김성규;박영승;최현규;이정혜;김경근
    • Journal of Advanced Marine Engineering and Technology
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    • 제27권2호
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    • pp.280-288
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    • 2003
  • We need refrigeration system which can maintain the freshness of agricultural products, because of being distance from a tiller to a consumer. Vacuum Pre-cooling system has an advantage in quality maintenance through vapid cooling down by using latent heat of evaporation of stored products. A number or thawing methods in current use have also several disadvantages in thawing time. discoloration mass loss caused by drying, capital costs and running cost. These damages are, it is claimed, either eliminated or improved by the vacuum thawing system. An experimental study on the pre-cooling for the bean sprouts and cabbage, and thawing for hairtail and croaker by the low temperature vacuum system were carried out. The cabbage cooling time with this Pre-cooling vacuum system took about 60 minutes to reach from $23.2^{circ}C to 4.5^{\circ}C$ at 5 mmHg abs. ($6.66\times10^{-4}$ MPa). The croaker thawing time with this low temperature vacuum thawing system took about 170 minutes to reach from $-10.3^{circ}C to -0.8^{\circ}C$ at 20 mmHg abs ($2.67\tiems10^{-3}$MPa). The vacuum Pre-cooling and thawing system have merits compared with present systems in their short intervals to cool down and to thaw without any quality losses.

BEMS 데이터의 통계적 분석에 기반한 공조기 최적 예냉운전 모델 개발 (Developing Optimal Pre-Cooling Model Based on Statistical Analysis of BEMS Data in Air Handling Unit)

  • 최선규;곽노열;구상헌
    • 설비공학논문집
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    • 제26권10호
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    • pp.467-473
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    • 2014
  • Since the operating conditions of HVAC systems are different from those for which they are designed, on-going commissioning is required to optimize the energy consumed and the environment in the building. This study presents a methodology to analyze operational data and its applications. A predicted operation model is to be produced through a statistical data analysis using multiple regressions in SPSS. In this model, the dependent variable is the pre-cooling time, and the independent variables include the power output of the supply air inverter during pre-cooling, the supply air set temperature during pre-cooling, the indoor temperature-indoor set temperature just before pre-cooling, supply heat capacity, and the lowest outdoor air temperature during non-cooling/non-heating hours. The correlation coefficient R2 of the multiple regression model between the pre-cooling hour and the internal/external factors is of 0.612, and this could be used to provide information related to energy conservation and operating guidance.

수소충전소용 프리쿨러를 위한 수소가스 냉각에 관한 연구 (Study on Cooling of Hydrogen Gas for the Pre-Cooler in the Hydrogen Refueling Station)

  • 이경한;구경모;유철휘;황갑진
    • 한국수소및신에너지학회논문집
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    • 제30권3호
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    • pp.237-242
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    • 2019
  • In the hydrogen refueling station (HRS), it is need the pre-cooling system (PCS) to limit the inside temperature ($85^{\circ}C$) of the onboard thank (700 bar) and to charge the hydrogen at short time (within 3 minutes) to fuel cell electric vehicle (FCEV). From those safety reasons, the temperature of hydrogen gas must be controled $-33^{\circ}C$ to $-40^{\circ}C$ in PCS. The cooling test of the gaseous ($N_2$, He, $H_2$) was carried out using heat exchanger (pre-cooler) by indirect cooling and direct cooling method. It was confirmed that the temperature of hydrogen gas had below $-40^{\circ}C$ at below $-75^{\circ}C$ of chiller temperature in direct cooling.

차압통풍 예냉 청과물의 냉각특성 (Cooling Characteristics of Fruits and Vegetables for Pressure Cooling)

  • 윤홍선;박경규
    • 한국식품저장유통학회지
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    • 제4권3호
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    • pp.237-243
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    • 1997
  • Numerous variables affect product cooling rate of pressure cooling system for fruits and vegetables. These include carton vent area, initial and desired final product temperature, flow rate and temperature of the cooling air, product size, shape and thermal properties and product configuration(whether in bulk or packed in shipping cartons). This study was carried out to determine the influence of each of these variables as they affect cooling time. The opening ratio and number of the vent hole were recomended as 4∼10% and 2∼4ea., respectively, for a minimum alt flow resistance and for a uniform air flow pattern. In the cooling experiment for tomatoes and mandarins, optimum air flow rate was 0.04 m3/min.kg in terms of energy saving. The cooling air temperature should be about 2$^{\circ}C$ less than the desired final product temperature for reducing cooling time.

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흡습 냉각 패드에서의 열 및 물질전달에 관한 연구 (Theoretical Analysis on the Heat and Mass Transfer in a Sorption Cool Pad)

  • 황용신;이대영;박봉철
    • 설비공학논문집
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    • 제16권2호
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    • pp.167-174
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    • 2004
  • A sorption cool pad brings cooling effect without any pre-cooling, nor any external energy supply. It uses evaporative cooling effect stimulated by the desiccative sorption. In this paper, heat and mass transfer in the sorption cool pad are investigated theoretically. The evaporative cooling process caused by the desiccant is modeled and analyzed considering the sorption characteristics of the desiccant. Two nondimensional parameters are found to dominate the cooling process: one is related to the psychrometric characteristics and the other is to the sorption capacity of the desiccant. The former decides the time to reach the lowest temperature and the later controls the time duration of the cooling effect being sustained.

산양유의 지방분해에 미치는 온도활성화 및 교반의 영향 (Effects of Agitation and Temperature Activation on Lipolysis in Goat Milk)

  • 김거유;이승범
    • 한국축산식품학회지
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    • 제20권2호
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    • pp.107-113
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    • 2000
  • This study was carried out to investigate the effects of temperature activation and agitation on lipolysis of goat milk. When goat milk was temperature activated twice at intervals of 12hours, free fatty acids were significantly increased after the first activation, but increased slightly during the re-cooling period and after the second activation. Lipolysis of the goat milk warmed at $30^{\circ}C$ was significantly facilitated during the re-cooling period. Lipolysis of the goat milk warmed at $30^{\circ}C$ was much higher than those warmed at $10^{\circ}C$ and $40^{\circ}C$ respectively. The highest lipolysis was occurred when the goat milk was warmed at $30^{\circ}C$ for 5 minutes after pre-cooling for 24 hours at $40^{\circ}C$. However, any significant difference was not found in the milk warmed at $40^{\circ}C$, regardless of the pre-cooling period. Lipolysis of the goat milk warmed and agitated at $30^{\circ}C$ was significantly facilitated during the re-cooling period. The lipolysis of that at $30^{\circ}C$ was significantly facilitated during the re-cooling period. The lipolysis of that at $30^{\circ}C$ was much enhanced with agitation. The lipolysis was much higher when agitated at $30^{\circ}C$ than when agitated at $10^{\circ}C$. The length of agitation time at $30^{\circ}C$ didn't give any effect on lipolysis.

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열간 판재단조시 강괴 내부의 기공폐쇄에 관한 연구 (Study on Internal Void Closure in Slab ingot during Hot Plate Forging)

  • 조종래;김동권;김영득;이부윤
    • 소성∙가공
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    • 제5권1호
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    • pp.18-26
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    • 1996
  • In order to investigate the effect of pre-cooling of ingot on void closure in hot plate forging the internal strain and stress distributions are examined quantitatively by using ABAQUS. Simula-tions are carried out on a large slab ingot having the same temperature and the temperature gradient induced by air-cooling. It is shown that pre-cooling produces little effect on the strain behavior but remarkable effect on the hydrostatic stress at the central zone of ingot. The main factors for crushing micro-voids are the effective strain and the time integral of hydrostatic stress in the region surrounding the voids. Based on regression analysis it was found that the distortion of void can be expressed as a polynomial function of the two factors.

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대형 단조품 코깅 공정의 기공 압착 인자에 대한 연구 (A Study on the Parameters Contributing to the Void Crushing in the Cogging Process of Large Forged Products)

  • 송민철;권일근;박연구
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2007년도 춘계학술대회 논문집
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    • pp.127-130
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    • 2007
  • Effect of the forging process parameters on the void crushing is the cogging process has been studied in order to find the most effective factor. The Process parameters used for this study are die width ratio, reduction ratio and pre-cooling time before cogging process. Void crushing analysis about the selected process parameters was carried out using FE analysis. The results of FE analysis were evaluated by Taguchi method. It was found that the efficiency of void crushing increases with an increase in the values of all selected process parameters and the principal factor controlling the void crushing was identified as the reduction ratio.

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대형 단조품 코깅 공정의 기공 압착 인자에 대한 연구 (A Study on the Parameters Determining the Void Crushing Ratio in the Cogging Process of Large Forged Products)

  • 송민철;권일근;박연구
    • 소성∙가공
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    • 제16권7호
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    • pp.502-508
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    • 2007
  • Effect of the process parameters of the cogging process on the void crushing has been studied in order to identify the most effective factor. The process parameters considered in this study are die width ratio, reduction ratio and pre-cooling time before cogging process. Void crushing analysis with the selected process parameters was carried out using FE analysis. The results of FE analysis were evaluated by Taguchi method. It was found that the efficiency of void crushing increases with an increase in the values of all selected process parameters and the principal factor controlling the void crushing was identified as the reduction ratio.

자동차용 피스톤 주물의 3차원 응고해석 (Three Dimensional Solidification Analysis in Automotive Cast Piston)

  • 김지준;김진수;류관호;최정길;이진형;홍준표
    • 한국주조공학회지
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    • 제13권3호
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    • pp.268-275
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    • 1993
  • In gravity die casting, die cooling systems are frequently employed with water cooling to remove the heat of the solidifying metal. Thermal modeling is an important technique in mold design for improving the productivity of the process. Computer simulation system which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of cyclic gravity die casting. The pre-processor is used for mesh generation in a PC system. The modified finite difference method is adopted for the main solidification simulation algorithm during all the casting cycles. The post-processor graphically presents the simulation results. Several experiments in automotive cast piston were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. The effects of cycle number on solidification pattern are also studied. Several experimental results for the prediction of shrinkage defects are compared with calculated results.

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