• 제목/요약/키워드: Heat transportation

검색결과 319건 처리시간 0.027초

Internal Changes of Blood Compartment and Heat Distribution in Swamp Buffaloes under Hot Conditions : Comparative Study of Thermo-Regulation in Buffaloes and Friesian Cows

  • Koga, A.;Kurata, K.;Ohata, K.;Nakajima, M.;Hirose, H.;Furukawa, R.;Kanai, Y.;Chikamune, T.
    • Asian-Australasian Journal of Animal Sciences
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    • 제12권6호
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    • pp.886-890
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    • 1999
  • From previous studies, there is a strong possibility in buffaloes that the marked increase in blood volume (BV) under hot conditions contributes to heat transportation from the rectum to the skin. The present study was done to clarify changes with environmental temperature on water-shift between blood and extracellular fluid (ECF), heat distribution between the rectum and the skin, and blood flow rates (BFR) at the hind legs (reflecting the skin surface). Four buffaloes and four Friesian cows were successively exposed to three different temperatures of $20^{\circ}C$, $30^{\circ}C$ and $35^{\circ}C$. BV and ECF volume were measured with Evans' blue and sodium-thiocyanate dilution methods, respectively. Rectal and subcutaneous (as the skin) temperatures were measured by copper-constantan thermocouples. BFR were measured by a supersonic blood flow meter. With an increase in environmental temperature, skin temperature in buffaloes increased significantly than cows, but rectal temperature was not significantly different between two species. BV, especially plasma compartment, increased significantly in only buffaloes, while ECF volume did not change in both species. BFR increased significantly in buffaloes, but not in cows. From these results, the increased of BV may be caused by water flowing from ECF compartment. The water-shift may induce the increase of BFR and skin temperature. It is suggested in the present study that internal changes of blood compartment in buffaloes contribute to transfer of heat to the skin surface.

저온의 고-액상변화 모듈 용기의 배열에 따른 축냉시스템의 수치해석 (Numerical Analysis of Cold Storage System with Array of Solid-Liquid Phase Change Module)

  • 문수범
    • 해양환경안전학회지
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    • 제21권5호
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    • pp.577-582
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    • 2015
  • 본 논문은 육해상의 운송장치에 축냉시스템을 적용시키기 위한 기초 연구이다. 또한, 축냉재의 고액상변화에 대한 수치해석을 수행한 연구이다. 수치해석법으로는 유한차분법(Finite-Difference Method)을 이용하였으며, 1차원 비정상의 상태를 가정하여 계산하였다. 또한 용기는 직사각형의 구형용기로 가정하여 대칭의 조건을 이용하였다. 축냉을 목적으로 사용하는 열매체는 염화칼슘 수용액($CaCl_2$) 30wt%의 물성치를 사용하여 계산을 수행하였다. 계산에 영향을 미치는 요소로는 냉동고의 냉기 온도 및 냉기 유속이 있으며, 축냉재를 싸고 있는 용기는 플라스틱으로 가정하였다. 본 수치해석에서 경계층의 두께는 냉기의 속도 증가와 함께 얇게 되고 축열시간도 짧아지는 것을 확인할 수 있었다. 그리고 냉기의 유속이 빨라질수록 열전달이 촉진되어 축냉용기 전면부에서의 온도가 낮아짐을 알았다. 축냉용기의 후면부에서는 경계층이 두꺼워져 열전달이 전면부에 비해 작아짐을 알았다.

Heat stress on microbiota composition, barrier integrity, and nutrient transport in gut, production performance, and its amelioration in farm animals

  • Patra, Amlan Kumar;Kar, Indrajit
    • Journal of Animal Science and Technology
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    • 제63권2호
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    • pp.211-247
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    • 2021
  • Livestock species experience several stresses, particularly weaning, transportation, overproduction, crowding, temperature, and diseases in their life. Heat stress (HS) is one of the most stressors, which is encountered in livestock production systems throughout the world, especially in the tropical regions and is likely to be intensified due to global rise in environmental temperature. The gut has emerged as one of the major target organs affected by HS. The alpha- and beta-diversity of gut microbiota composition are altered due to heat exposure to animals with greater colonization of pathogenic microbiota groups. HS also induces several changes in the gut including damages of microstructures of the mucosal epithelia, increased oxidative insults, reduced immunity, and increased permeability of the gut to toxins and pathogens. Vulnerability of the intestinal barrier integrity leads to invasion of pathogenic microbes and translocation of antigens to the blood circulations, which ultimately may cause systematic inflammations and immune responses. Moreover, digestion of nutrients in the guts may be impaired due to reduced enzymatic activity in the digesta, reduced surface areas for absorption and injury to the mucosal structure and altered expressions of the nutrient transport proteins and genes. The systematic hormonal changes due to HS along with alterations in immune and inflammatory responses often cause reduced feed intake and production performance in livestock and poultry. The altered microbiome likely orchestrates to the hosts for various relevant biological phenomena occurring in the body, but the exact mechanisms how functional communications occur between the microbiota and HS responses are yet to be elucidated. This review aims to discuss the effects of HS on microbiota composition, mucosal structure, oxidant-antioxidant balance mechanism, immunity, and barrier integrity in the gut, and production performance of farm animals along with the dietary ameliorations of HS. Also, this review attempts to explain the mechanisms how these biological responses are affected by HS.

광센서를 이용한 제상제어 방법에 대한 타당성 검토 (Feasibility Study on a Defrost Control Method by Using a Photoelectric Sensors)

  • 전창덕;김동선;이승준
    • 한국산학기술학회논문지
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    • 제15권6호
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    • pp.3389-3395
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    • 2014
  • 제상제어 수단으로 사용하고 있는 일정 시간 제어방식, 온도차 제어방식 등은 종종 제상 오작동과 에너지 낭비를 가져오므로 좀 더 정확하게 제상을 제어할 수 있는 방법이 요구되고 있다. 수광부와 발광부로 구성된 광센서를 실외 열교환기 전방에 설치하여 서리의 유무에 따른 출력전압의 변화를 관찰함으로서 정확하게 제상제어를 할 수 있다. 본 연구에서는 기존의 일정시간 제상 방법을 사용하는 경우 나타나는 시스템 성능 및 특성 곡선을 광센서를 사용하여 재현가능한지 판단하기 위해 KS C 9306에 따른 난방 제상능력 시험조건(건구온도 $2^{\circ}C$/습구온도 $1^{\circ}C$)에서 실험을 수행하였다. 실험을 통해 측정한 난방능력, 소비전력, 열교환기 표면온도와 광센서 수광부 출력전압을 비교, 분석한 결과 제상 제어수단으로 광센서의 사용가능성을 확인하였다. 일정시간 제상방법을 통해 구한 제상 제어 단속 주기는 광센서를 통해 측정한 출력 전압의 단속 주기와 잘 일치하였다.

설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제26권12호
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

삼중수소 저장용기 이종용접부의 수소취화 거동 평가 (I) (Evaluations of Hydrogen Embrittlement Behaviours on Dissimilar Welding Part of SDS Bottles (I))

  • 조경원;최재하;장민혁;이영상;홍태환
    • 한국수소및신에너지학회논문집
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    • 제26권2호
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    • pp.114-119
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    • 2015
  • Nowdays, fossil fuels have been used as an important resource in development of industry. But it is limited and caused climate change such as pollution and global warming. So nuclear fusion research is being issued with tritium to develop eco-friendly and sustainable energy. Republic of Korea is in charge of Storage and Delivery System (SDS) in the International Thermonuclear Experimental Reactor (ITER), weld present in the SDS bottles are easily exposed to the hydrogen embrittlement of special characteristics of the hydrogen in hydrogen atmosphere, When the hydrogen embrittlement is rapidly progresses, the cracking is generated in the weld zone. Due to this cracking, the risk of leakage of tritium into the atmosphere occurs. In this study, hydrogen heat treatment was processed through the Pressure-Composition-Temperature (PCT) device according to the time variation. Also mechanical properties such as rupture strength test, three point bend test and hardness test in accordance with the respective time have been conducted and the fracture was observed by scanning electron microscopy(SEM) after the mechanical properties evaluation.

Designing of a Novel Core-Shell-Structured Co-free Cathode Material with Enhanced Thermal and Structural Stability for Lithium Ion Batteries

  • Shin, Ji-Woong;Nam, Yun-Chae;Son, Jong-Tae
    • 전기화학회지
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    • 제22권4호
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    • pp.172-176
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    • 2019
  • The first commercialized cathode material, $LiCoO_2$, suffers from disadvantages such as high cost and toxicity and also possesses safety problems. The nickel-rich $LiNi_{0.9}Mn_{0.1}O_2$ cathode material, used as an alternative to $LiCoO_2$, has highly reversible capacity and high energy density. So, the nickel-rich $LiNi_{0.9}Mn_{0.1}O_2$ cathode material is widely used as an alternative to $LiCoO_2$ due to its highly reversible capacity and high energy density. However, $LiNi_{0.9}Mn_{0.1}O_2$ has several disadvantages as well, such as poor cycle performance and poor thermal instability. To address these problems, we synthesized a new material, $LiNi_{0.5}Mn_{0.5}O_2$, as a shell on the surface of a core to suppress the surface degradation. The new material showed high structural and thermal stabilities and could also maintain a high capacity. The capacity retention of the core-shell cathode (87.7%) was better than that of the core cathode (76.9%) after 50 cycles. Analysis using differential scanning calorimetry revealed that the heat generation in the core-shell cathode ($65.9Jg^{-1}$) was lower than that in the core cathode ($559.7Jg^{-1}$).

Enterococcus faecium CJNU 2008 균주 생산 박테리오신의 특성 규명 (Characterization of the Bacteriocin from Enterococcus faecium CJNU 2008)

  • 서숙진;양정모;문기성
    • 한국식품위생안전성학회지
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    • 제33권6호
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    • pp.516-520
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    • 2018
  • 박테리오신은 미생물이 생산하는 단백질성의 항균물질이다. 본 연구에서는 Enterococcus faecium CJNU 2008 균주로부터 생산되는 박테리오신에 대한 일부 특성을 규명하였다. 부분 정제 박테리오신은 열처리($100^{\circ}C$ 30분, $121^{\circ}C$ 15분) 및 유기용매(메탄올, 에탄올, 아세톤, 아세토니트릴, 클로로포름)에 대한 안정성이 우수하였으며 효소처리의 경우 Lipase와 ${\alpha}-amylase$에 대해서는 안정하였으나 Protease 처리에서 활성이 소실되었다. 이는 E. faecium CJNU 2008균주가 생산하는 항균물질이 단백질성의 박테리오신임을 추가적으로 증명하는 것이다. 병원성 세균인 Listeria monocytogenes 균주를 지시균으로 사용했을 때 박테리오신은 살균(bactericidal)의 작용양상을 보였다. Tricine-SDS-PAGE를 이용한 박테리오신의 분자량은 6.5 kDa 이하로 확인되었다. 부분 정제된 박테리오신을 이용하여 HPLC법을 활용한 정제를 수행하였으며 크로마토그램 상에서 단일 피크를 얻었을 수 있었다. 앞으로 정제된 박테리오신은 생화학적 분석 등에 활용할 계획이다.

공기조화, 냉동 분야의 최근 연구 동향 -2002년 및 2003년 학회지 논문에 대한 종합적 고찰 - (Recent Progress in Air Conditioning and Refrigeration Research - A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2002 and 2003 -)

  • 정광섭;김민수;김용찬;박경근;박병윤;조금남
    • 설비공학논문집
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    • 제16권12호
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    • pp.1234-1268
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    • 2004
  • A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2002 and 2003 has been carried out. Focus has been put on current status of research in the aspect of heating, cooling, air-conditioning, ventilation, sanitation and building environment/design. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation in diverse facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat transfer, humidity was also interesting to promote comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing research topics. Well developed CFD technologies were widely applied for analysis and design of various facilities and their systems. (2) Heat transfer characteristics of enhanced finned tube heat exchangers and heat sinks were extensively investigated. Experimental studies on the boiling heat transfer, vortex generators, fluidized bed heat exchangers, and frosting and defrosting characteristics were also conducted. In addition, the numerical simulations on various heat exchangers were performed and reported to show heat transfer characteristics and performance of the heat exchanger. (3) A review of the recent studies shows that the performance analysis of heat pump have been made by various simulations and experiments. Progresses have been made specifically on the multi-type heat pump systems and other heat pump systems in which exhaust energy is utilized. The performance characteristics of heat pipe have been studied numerically and experimentally, which proves the validity of the developed simulation programs. The effect of various factors on the heat pipe performance has also been examined. Studies of the ice storage system have been focused on the operational characteristics of the system and on the basics of thermal storage materials. Researches into the phase change have been carried out steadily. Several papers deal with the cycle analysis of a few thermodynamic systems which are very useful in the field of air-conditioning and refrigeration. (4) Recent studies on refrigeration and air-conditioning systems have focused on the system performance and efficiency enhancement when new alternative refrigerants are applied. Heat transfer characteristics during evaporation and condensation are investigated for several tube shapes and new alternative refrigerants including natural refrigerants. Efficiency of various compressors and performance of new expansion devices are also dealt with for better design of refrigeration/air conditioning system. In addition to the studies related with thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out. It should be noted that the researches on two-phase flow are constantly carried out. (5) A review of the recent studies on absorption refrigeration system indicates that heat and mass transfer enhancement is the key factor in improving the system performance. Various experiments have been carried out and diverse simulation models have been presented. Study on the small scale absorption refrigeration system draws a new attention. Cooling tower was also the research object in the respect of enhancement its efficiency, and performance analysis and optimization was carried out. (6) Based on a review of recent studies on indoor thermal environment and building service systems, it is noticed that research issues have mainly focused on several innovative systems such as personal environmental modules, air-barrier type perimeterless system with UFAC, radiant floor cooling system, etc. New approaches are highlighted for improving indoor environmental conditions and minimizing energy consumption, various activities of building energy management and cost-benefit analysis for economic evaluation.

공기조화, 냉동 분야의 최근 연구 동향 -2000년 및 2001년 학회지 논문에 대한 종합적 고찰 - (Recent Progress in Air Conditioning and Refrigeration Research -A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2000 and 2001-)

  • 강신형;한화택;조금남;이승복;조형희;김민수
    • 설비공학논문집
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    • 제14권12호
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    • pp.1102-1139
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    • 2002
  • A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2000 and 2001 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation of facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat, humidity was also interesting for comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing topics. Well developed CFD technologies were widely applied for developing facilities and their systems. (2) Most of papers related with heat transfer analysis and heat exchanger shows dealt with convection, evaporation, and channel flow for the design application of heat exchanger. The numerical heat transfer simulation studies have been peformed and reported to show heat transfer characteristics. Experimental as well as numerical studies on heat exchanger were reported, while not many papers are available for the system analysis including heat exchanger. (3) A review of the recent studies on heat pump system shows that performance analysis and control of heat pump have been peformed by various simulations and experiments. The research papers on multi-type heat pump system increased significantly. The studies on heat pipe have been examined experimently for change of working characteristics and strut lure. Research on the phase change has been carried out steadily and operation strategies of encapsulated ice storage tank are reported experimentally in several papers. (4) A review of recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. Evaporation and condensation heat transfer characteristics are investigated for tube shapes and new alternative refrigerants. Studies on components of refrigeration/air conditioning system are carried to examine efficiency for various compressors and performance of new expansion devices. In addition to thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out, however research works on two-phase flow seemed to be insufficient. (5) A review of the recent studies on absorption cooling system indicates that heat and mass transfer phenomena have been investigated to improve absorber performance. Various experimental data have been presented and several simulation models have been proposed. A review of the recent studies on duct and ventilation shows that ventilation indices have been proposed to quantify the ventilation performance in buildings and tunnels. Main efforts have been focused on the applications of ventilation effectiveness in practice, either numerically using computational fluid dynamics or experimentally using tracer gas techniques. (6) Based on a review of recent studies on indoor thermal environment and building service systems, research issues have mainly focused on many innovative ideas such as underfloor air-conditioning system, personal environmental modules, radiant floor cooling and etc. Also, the new approaches for minimizing energy consumption as well as improving indoor environmental conditions through predictive control of HVAC systems, various activities of building energy management and cost-benefit analysis for economic evaluation were highlighted.