• Title/Summary/Keyword: surface heating

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The Effect of Soil Warming on the Greenhouse Heating Load (지중가온이 온실의 난방부하에 미치는 영향)

  • Nam, Sang-Woon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.48 no.5
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    • pp.51-60
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    • 2006
  • In order to examine the heat transfer characteristic of a soil warming system and effects of soil warming on the greenhouse heating load, control experiments were performed in two greenhouses covered with double polyethylene film. One treated the soil warming with an electric heat wire and the other treated a control. Inside and outside air temperature, soil temperature and heat flux, and heating energy consumption were measured under the set point of heating temperature of $5,\;10,\;15,\;and\;20^{\circ}C$, respectively. Soil temperatures in a soil warming treatment were observed $4.1\;to\;4.9^{\circ}C$ higher than a control. Heating energy consumptions decreased by 14.6 to 30.8% in a soil warming treatment. As the set point of heating temperature became lower, the rate of decrease in the heating energy consumptions increased. The percentage of soil heat flux in total heating load was -49.4 to 24.4% and as the set point of heating temperature became higher, the percentage increased. When the set point of heating temperature was low in a soil warming treatment, the soil heat flux load was minus value and it had an effect on reducing the heating load. Soil heat flux loads showed in proportion to the air temperature difference between the inside and outside of greenhouse but they showed big difference according to the soil warming treatment. So new model for estimation of the soil heat flux load should be introduced. Convective heat transfer coefficients were in proportion to the 1/3 power of temperature difference between the soil surface and the inside air. They were $3.41\;to\;12.42\;W/m^{2}^{\circ}C$ in their temperature difference of $0\;to\;10^{\circ}C$. Radiative heat loss from soil surface in greenhouse was about 66 to 130% of total heating load. To cut the radiation loss by the use of thermal curtains must be able to contribute for the energy saving in greenhouse.

An Investigation of Surface Appearance of an Injection-Molded Plastic Part with Various Induction Heating Conditions (고주파 가열조건에 따른 플라스틱 사출성형품의 표면특성 고찰)

  • Sohn, Dong-Hwi;Seo, Young-Soo;Park, Keun;Lee, Kwang-Woo
    • Elastomers and Composites
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    • v.44 no.4
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    • pp.358-365
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    • 2009
  • High-frequency induction is an efficient way to rapidly heat mold surface by electromagnetic induction. In the present work, high-frequency induction heating is applied to injection molding of a mobile phone cover in order to eliminate weldlines by efficiently raising the mold temperature. Through the induction heating experiments, the maximum temperature of $143^{\circ}C$ is obtained on the mold surface in 3s of heating, which is higher than the glass transition temperature of the resin material. An injection molding experiment is then performed with the aid of induction heating, from which we can successfully remove all the weldlines of the mobile phone cover. The effect of induction heating conditions such as the heating power and the heating time on the surface appearance is experimentally investigated.

Characteristics of plasma sprayed composite YSZ/Ni-Cr resistant heating coatings (YSZ/Ni-Cr 저항 발열 복합용사피막의 특성)

  • 김병수;박경채;김태형;양병모
    • Proceedings of the KWS Conference
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    • 2003.05a
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    • pp.111-113
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    • 2003
  • The existing heating unit is indirect-heating method that make use or the nichrome wire or halogen lamp. The indirect-heating method has the demerits of long warming time, high power consumption and many organization parts. In this study, the heating unit of direct-heating method manufactured as being the thermal spray coating of conductive heating material on the surface of heating unit in order to improve the demerits of indirect-heating method. And YSZ added Ni-20Cr that had moderate electrical resistivity was chosen of the conductive heating material.

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A Study of Surface Improvement for Automotive Part by Injection Mold of Electronic Heating (전류가열 사출금형에 의한 자동차 부품의 표면개선에 관한 연구)

  • Choi, Dong-Hyuk;Hwang, Hyun-Tae;Son, Dong-Il;Kim, Daeil
    • Journal of the Korean institute of surface engineering
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    • v.51 no.1
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    • pp.40-46
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    • 2018
  • The light-weight of the research and development materials is actively carried out by overseas automobile companies and technology development continues in Korea. For the sake of fuel efficiency, the development of lightweight technology by improving the manufacturing method has been very effective. Recently, to maximize the effects of light weight, automotive interior parts have been applied by the micro-cellular injection molding using supercritical fluids and we call the Mucell manufacturing. This technique causes a problem in the quality of the surface of the products, because the shooting cells are revealed as the surface layer of the products by forming micro cells at the center of the products during injection molding. To overcome these phenomenon, we increased the temperature of injection molding using joule heating until critical value. In this study, we have predicted the problem of Mucell injection molding through the finite element analysis as changed the temperature by joule heating. From the result of finite element analysis, we have determined the optimized process and made the injection mold included electric current heating system with Mucell manufacturing analyzed the surface characteristics of the injection product according to changing mold temperature.

Change of Surface Temperature in Woodceramics Made from MDF(I) -Effect of Density and Burning Temperature- (MDF로 제조된 우드세라믹의 표면온도변화(I) -밀도 및 소성온도의 영향-)

  • 오승원
    • Journal of Korea Foresty Energy
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    • v.21 no.1
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    • pp.1-6
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    • 2002
  • The following conclusions were obtained with measuring the surface temperature change of woodceramics which were made of MDF to identify usability of using them as a sub-material for heating system when installing Ondol heating floor. For this purpose, woodceramics were burned at the temperature of $650^{\circ}C$ and $800^{\circ}C$ 1. Surface temperature of woodceramics increased with the increase of density of woodceramics, but no significant difference was detected at the surface temperature when burning temperature was changed. 2. Surface temperature change under given temperature increased as time passed and it showed more increase in temperature at the burning temperature of 80$0^{\circ}C$. 3. Surface temperature change with the change in floor temperature increased u hen floor temperature increased and heating mechanism was fast with increase of measuring temperature.

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Effect of Moisture Migration in Concrete with Hating Rate on Concrete Spalling (가열속도에 따른 콘크리트 내부의 수분이동이 폭렬발생에 미치는 영향)

  • Choe, Gyeong-Cheol;Kim, Gyu-Yong;Nam, Jeong-Soo;Kim, Hong-Seop;Yoon, Min-Ho;Hwang, Ui-Chul
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2017.05a
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    • pp.246-247
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    • 2017
  • In this study, it reviewed the effect of moisture migration in concrete with heating rate on concrete spalling. Concrete specimens with compressive strength 30MPa and 110MPa are used and its size is □100×100×h200mm. And, two kinds of heating rate are set such as IS0 834 and 1℃/min. As a result, in the concrete specimen exposed to ISO 834 standard heating condition, moisture could migrate through pore network and surface concrete pieces fall out by generating moisture clog near the surface in 110MPa concrete specimen. Meanwhile, In the case of concrete specimens exposed to 1℃/min. heating condition, it is appeared that moisture could not migrate because temperature is distributed uniformly. Therefore, surface spalling is not occurred with low heating rate. However, in the case of 110MPa concrete specimen is exploded even though it heated by low heating rate.

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Nondestructive Estimation of Average Wood Moisture Content Using Surface Temperature Rise by Radiation Heating and Moisture Gradient

  • Lee, Hyoung-Woo;Kim, Byung-Nam
    • Journal of the Korean Wood Science and Technology
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    • v.27 no.4
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    • pp.38-42
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    • 1999
  • Average moisture content of 30mm-thick Korean red pine(Pinus densiflora) was estimated nondestructively and continuously using surface temperature rise by radiation heating and moisture gradient profile in wood. The surface temperature rises increased as surface moisture contents decreased and good relationships were found between surface moisture contents and surface temperature rises at three different feed speeds of 10, 20 and 30 m/min. Average moisture content could be described as a function of surface moisture content and wood thickness.

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Aerodynamic Heating Test of Payload Fairing of KSLV-I (KSLV-I 페어링 공력 가열 시험)

  • Choi, Sang-Ho;Kim, Seong-Lyong;Kim, In-Sun
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.448-451
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    • 2008
  • KARI is developing a satellite launch vehicle that is called KSLV(Korea Space Launch Vehicle)-I. During the flight, launch vehicles are exposed to aerodynamic heating conditions while flying at high Mach numbers in the atmosphere. KARI constructed Aerodynamic Thermal Simulation Facility to simulate aerodynamic heating on the ground. ATSF is a facility that can simulate given temperature profile using about 4,000 halogen heaters on fairing model. Aerodynamic heating profile is got from result of thermal analysis using MINIVER, Thermal Desktop, and SINDA/FLUINT. Aerodynamic heating test of fairing of KSLV-I was done using engineering model of payload fairing and Aerodynamic Thermal Simulation Facility. It was found that thermal analytic results show good agreement with aerodynamic heating test results within 6$^{\circ}$C at fairing inner surface. Also it was confirmed that maximum temperature of fairing nose-cone inner surface during flight is lower than allowable temperature limit.

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The Effects of Operating and Design Conditions on the Performance of Radiant Heating Panel (복사 난방 패널의 공급유량 및 설계변수가 성능에 미치는 영향)

  • Lee, Tae Won;Kim, Ho Young
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.4
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    • pp.276-285
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    • 1991
  • The transient heat transfer characteristics in the radiant heating panel were predicted by numerical analysis. Thermal behaviors of panel, such as temperature distributions in panel and convective and radiative heat fluxes in panel surface with respect to time were obtained. Heating hours per day, rate of energy supplied and maximum temperature differences at panel surface were also compared for several important parameters. The performance and thermal comfort of heating panel were studied and compared for various operating and design conditions such as pipe pitch, pipe location, pipe diameter and flow rate of hot water for the purpose of producing useful data, which can be used for the test and decision of efficient operating condition of the conventional heating systems or the optimal design of the new panel heating systems.

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Fundamental Study for Development of Pre-Heater for Warm In-Place Recycling in Korea (국내 현장중온재생공법의 프리히터 개발을 위한 기초연구)

  • Kim, Dae-Hun;Kim, Seung-Hoon;Kwon, Soo-Ahn;Kim, Yongjoo;Lee, Jaejun
    • International Journal of Highway Engineering
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    • v.17 no.2
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    • pp.31-37
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    • 2015
  • PURPOSES : To design a pre-heater for warm in-place recycling equipment, three different heating systems were evaluated to determine their thermal efficiency. METHODS: In this study, a $30cm{\times}30cm{\times}15cm$ wheel-tracking specimen was used to measure the inner temperature as a function of the heating system. The inner temperature of the specimen was measured with a data logger at the surface, and at depths of 1cm, 2cm, 3cm, 4cm, and 5cm. To evaluate the thermal efficiency, the researchers used three different types of equipment, namely, IR, a heating wire, and a gas burner. RESULTS: The IR heating system exhibits a higher level of performance than the others to achieve the target temperature at a depth of 5cm in the specimen. The gas burner system was capable of heating the surface to a temperature of up to $600^{\circ}C$. The other types, however, cannot heat the surface up to 600. The thermal efficiencies were measured based on the laboratory conditions. CONCLUSIONS: To find the most effective system for application to the development of a pre-heater for warm in-place recycling, various systems (IR, heating wire, gas burner) were examined in the laboratory. As a result, it was found that the hot plate of a gas burner system provides the highest temperature at the surface of the asphalt but, of all the systems, the IR system provides the best internal temperature increase rate. Furthermore, a gas burner can age the asphalt binder of the surface layer as a result of the high temperature. However, the gas burner cannot attain the target temperature at 5cm. The IR system, on the other hand, is effective at increasing the internal temperature of asphalt.