• Title/Summary/Keyword: Bio-heat transfer

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Analysis on Heat Loss of Single-span Greenhouse Using Small-scaled Wind Tunnel (소형풍동을 이용한 단동 비닐온실의 열손실 분석)

  • Kim, Young Hwa;Kim, Hyung kow;Lee, Tae suk;Oh, Sung sik;Ryou, Young sun
    • Journal of Bio-Environment Control
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    • v.29 no.1
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    • pp.73-79
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    • 2020
  • The objective of this study is to analyze the heat transfer loss of covering materials in a single-span plastic greenhouse under the steady-state wind environment. To achieve this objective, the following were conducted: (1) design of a small-scaled wind tunnel (SCWT) to analyze heat losses of the greenhouse and its performance; (2) determination of the overall heat transfer coefficient (OHTC) for the covering materials using a small-scaled greenhouse model. The SCWT consists of the blowing, dispersion, steady flow, reduction and testing areas. Each part of the SCWT was customized and designed to maintain air flow at steady state and to minimize the variances in the SCWT test. In this study, the OHTCs of the covering materials were calculated by separating each with the roof, side wall, front and back of the small-scaled greenhouse model. The results of this study show that the OHTC of the roof increases as wind speed increases but the zones in which the increase rate of the OHTC decreased, were distinguished by wind tunnel wing speed of 2 ms-1. For the side wall, the increase rate of the OHTC was particularly higher in the 0-1 ms-1 zone.

Comparison of Heat Insulation Characteristics of Multi-layer Thermal Screen and Development of Curtain System (다겹보온자재의 보온성 비교 및 커튼개폐장치 개발)

  • Lee, Si-Young;Kim, Hark-Joo;Chun, Hee;Yum, Sung-Hyun;Lee, Hyun-Joo
    • Journal of Bio-Environment Control
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    • v.16 no.2
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    • pp.89-95
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    • 2007
  • This study was accomplished to compare energy saving effects of several heat insulation materials in greenhouse and to develop new automatic opening and closing equipment which is suitable to the most effective heat insulation material. To find out more effective heat insulation material, the magnitude of heat transfer occurred through aluminum screen (ALS), non-woven fabric (NWF), double-layer aluminum screen with chemical cotton sheet (DAL), and multi-layer fabric screen material quilted with non-woven fabric, chemical cotton, poly foam, and polypropylene (MLF) were compared relatively. The results showed that the relative magnitude of heat transfer occurred through MLF was lower than DAL and ALS by 23.3% and 43.0% respectively. MLF screen material was the most effective compared with other heat insulation materials. But because of thickness, there was a need of new mechanism for automatic operation in greenhouse. Accordingly, new screen system using MLF-thick but profitable for keeping warm in greenhouse-was developed. Opening & closing equipment was designed to roll MLF with pipe axis during opening process and pull MLF with string during closing process with electric motors, clutches, drums, and so on. In hot pepper cultivation and energy saving test during winter time, the early stage yield of pepper under MLF screen system was higher than NWF by 27%, and gasoline consumption of MLF screen system was lower than NWF by 46%.

Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014 (설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.7
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. 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 heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were 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 thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance 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 was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

Heat Exchange Performance of Improved Heat Recovery System (개량형 열회수 시스템의 열교환 성능)

  • Suh, Won-Myung;Yoon, Yong-Cheol;Kwon, Jin-Keun
    • Journal of Bio-Environment Control
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    • v.12 no.3
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    • pp.107-113
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    • 2003
  • This study was carried out to improve the performance of pre-developed heat recovery devices attached to exhaust-gas flue connected to combustion chamber of greenhouse heating system. Four different units were compared in the aspect of heat recovery performance; A-, B-, and C-types are exactly the same with the old ones reported in previous studies. D-type newly developed in this experiment is mainly different with the old ones in its heat exchange area and tube thickness. But airflow direction(U-turn) and pipe arrangement are similar with previous three types. The results are summarized as follows; 1. System performances in the aspect of heat recovery efficiency were estimated as 42.2% for A-type, 40.6% for B-type, 54.4% for C-type, and 69.2% for D-type. 2. There was not significant improvement of heat recovering efficiency between two different airflow directions inside the heat exchange system. But considering current technical conditions, straight air flow pattern has more advantage than hair-pin How pattern (U-turn f1ow). 3. The main factors influencing on heat recovery efficiency were presumably verified to be the total area of heat exchange surface, the thickness of ail-flow pipes, and the convective heat transfer coefficient influenced by airflow velocity under the conditions of allowable pipe durability and safety. 4. Desirable blower capacity for each type of heat recovery units were significantly different to each other. Therefore, the optimum airflow capacity should be determined by considering in economic aspect of electricity required together with the optimum heat recovery performance of given heat recovery systems.

Circulating Concurrent-flow Drying Simulation of Rapeseed (순환식 병류형 유채씨 건조 시뮬레이션)

  • Han, Jae-Woong;Keum, Dong-Hyuk;Kim, Woong;Duc, Le Anh;Cho, Sung-Ho;Kim, Hoon
    • Journal of Biosystems Engineering
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    • v.35 no.6
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    • pp.401-407
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    • 2010
  • In this study, computer simulations were conducted to assess the use of a circulating concurrent-flow dryer for rapeseed drying and to determined the effect of this drying method on the germination ratio of rapeseed after the drying process was complete. The simultaneous heat and mass transfer between air and rapeseed in a concurrent-flow dryer was examined by simulation. The drying simulation was based on several parameters with sequent time series. Equations concerning air psychrometrics, physical properties, thermal properties, equilibrium moisture content, thin layer drying of rapeseed, etc. were all combined to solve the simulation models. Based on energy and mass transfer in the concurrent-flow drying model, a simulation program for the circulating concurrent-flow rapeseed dryer was built along with a detailed description of the mathematical solution to the model. A pilot scale circulating concurrent-flow dryer(200 kg/batch) was used to verify the fitness of the simulation program. A comparison between the experimental data and the model predicted results was presented and discussed. The drying parameters and germination ratio were analyzed and the accuracy of the simulation program was evaluated. The simulation program proved to be reliable and was shown to be a convenient tool for predicting rapeseed drying and germination ratio of rapeseed in a concurrent-flow dryer.

Heat Transfer Characteristics and Cooling Load of a Soil Cooling System in Greenhouse Root Zone (지중 냉각 시스템의 열전달 특성과 냉각부하)

  • 남상운
    • Proceedings of the Korean Society for Bio-Environment Control Conference
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    • 2002.04a
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    • pp.25-29
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    • 2002
  • 대부분의 작물이 생육하기에 적합한 지온은 18-2$0^{\circ}C$정도이고 최고한계는 23-$25^{\circ}C$로 알려져 있으나, 여름철 온실내의 지온은 이보다 높으며 2001년 8월에 온실내의 지온을 계측해본 결과 표층으로부터 5-35cm 깊이의 평균 지온은 27-29.4$^{\circ}C$까지 상승하는 것으로 나타났다(김 등, 2001). 따라서 지중 냉각의 필요성이 인정되며, 정 등(1998)의 보고에 의하면 무처리시 지온 25.7$^{\circ}C$에 대하여 지하수 냉각으로 지온을 19-19.6$^{\circ}C$로 냉각해줄 경우 배추 수량이 8-11% 증수되었다. (중략)

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Effects of hCG Treatment on the Pregnancy Rates and Progesterone Concentrations in Hanwoo Recipients with SCNT Embryos (hCG 투여가 복제란 이식 한우 대리모의 임신과 Progesterone 농도에 미치는 영향)

  • Hwang, Seong-Soo;Yang, Byoung-Chul;Im, Gi-Sun;Ko, Yeoung-Gyu;Choi, Sun-Ho;Min, Kwan-Sik;Yoon, Jong-Taek;Seong, Hwan-Hoo
    • Journal of Embryo Transfer
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    • v.23 no.3
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    • pp.177-181
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    • 2008
  • This study was performed to investigate the effects of hCG treatment on pregnancy and delivery rates in the Hanwoo recipients. There were significantly higher pregnancy and delivery rates in the recipients treated with hCG at 7 days after artificial insemination (p<0.05), respectively. The SCNT embryos from bovine fetal fibroblast cells were transferred into the synchronized recipients. The recipients were administered saline (n=89) or hCG (1,500 IU) (n=48) at 7 days after heat, respectively. The pregnancy rate was significantly higher in the recipients treated with hCG compared to that of saline treated group (p<0.01), however, the delivery rate was not different in both treated groups. The concentration of plasma progesterone (P4) was not different in both groups before hCG treatment, but the P4 level was increased significantly in hCG treated group after hCG injection (p<0.05). Although the pregnancy rate was very high in early stage of pregnancy, it was decreased dramatically after 50 days of pregnancy and maintained basal level. Taken together, the treatment of hCG in the SCNT recipients after day 7 of heat was effective method to increase the P4 concentration and to increase the pregnancy rate. But it did not affect directly to delivery.

Dehumidification and Evaporative Cooling Efficiency by Water Pipes in Greenhouse (냉수파이프에 의한 온실의 제습 및 증발냉각효율)

  • 김문기;남상운;윤남규
    • Journal of Bio-Environment Control
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    • v.7 no.3
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    • pp.237-245
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    • 1998
  • Greenhouse crop production under critical summer climate In Korea has considerable difficulties because of high temperature and relative humidity. In this study, some water pipes were tested as a means of the dehumidification and increment of evaporative cooling efficiency. As a result of heat transfer characteristic analysis, overall heat transfer coefficient of copper pipe was larger than steel pipe, and estimated values were smaller than measured values. The condensed quantities of vapor were not significantly different between copper pipe and steel pipe, however dehumidifying effect by the water pipes was significantly large. It was estimated based on the results that the evaporative cooling system by the water pipe will be able to increase the evaporative cooling efficiency of about 48%, and decrease the temperature of about 1.3$^{\circ}C$.

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Heat Insulation Characteristics of Multi Layer Materials for Greenhouse (시설원예용 조합형 다겹보온자재의 보온 특성)

  • Chung, Sung-Won;Kim, Dong-Keon;Lee, Suk-Gun;Nam, Sang-Heon;Lee, Yong-Beom
    • Journal of Bio-Environment Control
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    • v.18 no.4
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    • pp.341-347
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    • 2009
  • Experiments and computations were conducted to investigate the heat insulation characteristics of multi layer materials for cultivation greenhouse. In case of the experiments, measurements of temperature were carried out with a K-type thermocouples and data logger to research the heat transfer in the experimental module generated by the heat source. A thermal conductivity meter, QTM-500 based on modified transient hot wire method was used to measure the thermal conductivity of multi layer materials. The numerical analyses were performed by commercial code CFX-11 according to the variation of multi layer materials without air layer. The experimental results showed that the heat insulation of multi layer materials was higher than single layer materials by 50~90%. It was found that the effect of heat insulation was raised by the combination of multi layer materials.

Cooling Performance of Horizontal Type Geothermal Heat Pump System for Protected Horticulture (시설원예를 위한 수평형 지열 히트펌프의 냉방성능 해석)

  • Ryou, Young-Sun;Kang, Youn-Ku;Kang, Geum-Chun;Kim, Young-Joong;Paek, Yee
    • Journal of Bio-Environment Control
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    • v.17 no.2
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    • pp.90-95
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    • 2008
  • It has become a big matter of concerns that the skill and measures against reduction of energy and cost for heating a protected horticultural greenhouse were prepared. But in these days necessity of cooling a protected horticultural greenhouse is on the rise from partial high value added farm products. In this study, therefore, a horizontal type geothermal heat pump system with 10 RT scale to heat and cool a protected horticultural greenhouse and be considered to be cheaper than a vertical type geothermal heat pump system was installed in greenhouse with area of $240\;m^2$. And cooling performances of this system were analysed. As condenser outlet temperature of heat transfer medium fluid rose from $40^{\circ}C$ to $58^{\circ}C$, power consumption of the heat pump was an upturn from 11.5 kW to 15 kW and high pressure rose from 1,617 kPa to 2,450 kPa. Cooling COP had the trend that the higher the ground temperature at 1.75 m went, the lower the COP went. The COP was 2.7 at ground temperature at 1.75 m depth of $25.5^{\circ}C$ and 2.0 at the temperature of $33.5^{\circ}C$ and the heat extraction rate from the greenhouse were 28.8 kW, 26.5 kW respectively at the same ground temperature range. 8 hours after the heat pump was operated, the temperature of ground at 60 cm and 150 cm depth buried a geothermal heat exchanger rose $14.3^{\circ}C$, $15.3^{\circ}C$ respectively, but the temperature of ground at the same depth not buried rose $2.4^{\circ}C$, $4.3^{\circ}C$ respectively. The temperature of heat transfer medium fluid fell $7.5^{\circ}C$ after the fluid passed through geothermal heat exchanger and the fluid rejected average 46 kW to the 1.5 m depth ground. It analyzed the geothermal heat exchanger rejected average 36.8 W/m of the geothermal heat exchanger. Fan coil units in the greenhouse extracted average 28.2 kW from the greenhouse air and the temperature of heat transfer medium fluid rose $4.2^{\circ}C$after the fluid passing through fan coil units. It was analyzed the accumulation energy of thermal storage thank was 321 MJ in 3 hours and the rejection energy of the tank was 313 MJ in 4 hours.