• Title/Summary/Keyword: Relative Thermal Control

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Determination of Thermal Radiation Emissivity and Absorptivity of Thermal Screens for Greenhouse (온실 스크린의 장파복사 방사율 및 흡수율 결정)

  • Rafiq, Adeel;Na, Wook Ho;Rasheed, Adnan;Kim, Hyeon Tae;Lee, Hyun Woo
    • Journal of Bio-Environment Control
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    • v.28 no.4
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    • pp.311-321
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    • 2019
  • Greenhouse farmers often use thermal screens to reduce greenhouse heating expenses during the winter, and for shade during hot, sunny days in the summer, as it is an inexpensive solution to temperature control relative to other available options. However, accurate measurements of their emitted and absorbed radiations are important for the selection of suitable screens that offer maximum performance. Material's ability to save energy is highly dependent on these properties. Limited studies have investigated the measurement of these properties under natural conditions, but they are only applicable to materials having partial porosities. In this work, we describe a new radiation balance method for determining emissive power and absorptive capacity, as well as reflectivity, transmissivity and emissivity of materials having complete and partial transparency by using pyrgeometer and net radiometer. In this study, four materials with zero porosity, were tested. The emissivity value of PE, LD-13, LD-15 and PH-20 was $0.439{\pm}0.020$, $0.460{\pm}0.010$, $0.454{\pm}0.004$, and $0.499{\pm}0.006$, respectively. All tested samples showed high emitted radiation as compared to absorbed radiation.

Influences of Wearing Far-infrared Indoor Clothing on Skin Blood Flow, Perceptual and Thermal Responses (원적외선 방사 기능 실내복 착용이 인체 피부혈류량, 온열 심리 및 온열 생리 기능에 미치는 영향)

  • Baek, Yoon Jeong;Seo, Wonji;Kim, Hyung Chan;Lee, Joo-Young
    • Journal of the Korean Society of Clothing and Textiles
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    • v.44 no.2
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    • pp.342-353
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    • 2020
  • The purpose of this study was to evaluate far-infrared clothing (FIR condition) with non-far-infrared clothing (Control condition) to assess the effects of FIR on thermo-physiological responses. Eight young healthy males (23.0±2.3 yr, 176.5±3.7 cm, and 69.0±4.3 kg) participated in this experimental trial, which consisted of a 20 min rest followed by a 40 min walk (4.0 km·hr-1) and a 20 min recovery at 20℃ with 50%RH. The results showed that finger skin blood flow and mean skin temperature were significantly higher for the FIR condition than the control during exercise and recovery (p<.001). Clothing microclimate temperature of the FIR condition was 0.5℃ higher on the back (p=.001) and 0.4℃ higher on the thigh (p=.015) during recovery. Clothing microclimate relative humidity of the FIR condition was 13% higher on the chest (p=.006) and 19% higher on the back (p<.001) during exercise than control. Subjects felt warmer and more comfortable in the FIR condition than in the control (p<.05). Perceived skin wettedness (%BSA) was less in the FIR condition than in the control (p=.001). These results indicate that ceramic-embedded clothing had significant effects on thermoregulatory responses for light activity in an indoor environment.

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 (설비공학 분야의 최근 연구 동향 : 2013년 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.26 no.12
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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.

Development of Greenhouse Cooling and Heating Load Calculation Program Based on Mobile (모바일 기반 온실 냉난방 부하 산정 프로그램 개발)

  • Moon, Jong Pil;Bang, Ji Woong;Hwang, Jeongsu;Jang, Jae Kyung;Yun, Sung Wook
    • Journal of Bio-Environment Control
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    • v.30 no.4
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    • pp.419-428
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    • 2021
  • In order to develope a mobile-based greenhouse energy calculation program, firstly, the overall thermal transmittance of 10 types of major covers and 16 types of insulation materials were measured. In addition, to estimate the overall thermal transmittance when the cover and insulation materials were installed in double or triple layers, 24 combinations of double installations and 59 combinations of triple installations were measured using the hotbox. Also, the overall thermal transmittance value for a single material and the thermal resistance value were used to calculate the overall thermal transmittance value at the time of multi-layer installation of covering and insulating materials, and the linear regression equation was derived to correct the error with the measured values. As a result of developing the model for estimating thermal transmittance when installing multiple layers of coverings and insulating materials based on the value of overall thermal transmittance of a single-material, the model evaluation index was 0.90 (good when it is 0.5 or more), indicating that the estimated value was very close to the actual value. In addition, as a result of the on-site test, it was evaluated that the estimated heat saving rate was smaller than the actual value with a relative error of 2%. Based on these results, a mobile-based greenhouse energy calculation program was developed that was implemented as an HTML5 standard web-based mobile web application and was designed to work with various mobile device and PC browsers with N-Screen support. It had functions to provides the overall thermal transmittance(heating load coefficient) for each combination of greenhouse coverings and thermal insulation materials and to evaluate the energy consumption during a specific period of the target greenhouse. It was estimated that an energy-saving greenhouse design would be possible with the optimal selection of coverings and insulation materials according to the region and shape of the greenhouse.

Application Effect of Heating Energy Saving Package on Venlo Type Glasshouse of Paprika Cultivation (파프리카 재배 벤로형 유리온실에서 난방에너지 절감 패키지 기술 적용효과)

  • Kwon, Jin Kyung;Jeon, Jong Gil;Kim, Seung Hee;Kim, Hyung Gweon
    • Journal of Bio-Environment Control
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    • v.25 no.4
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    • pp.225-231
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    • 2016
  • Glasshouse heating package technologies to improve energy usage efficiency in winter were developed. Heating package was composed of the ground water source heat pump with heating capacity of 105kW, the aluminum multi-layer thermal curtain with six layers of different materials and the root zone local heater with XL pipes of ${\phi}20mm$. Venlo type glasshouse($461m^2$) with the heating package was compared with the same type and area control glasshouse with the light oil boiler, the usual non-woven fabric thermal curtain with respect to the glasshouse inside temperature, relative humidity, crop growth, and heating energy consumption. The results of test in paprika cultivation glasshouses showed that the air temperature inside glasshouse with aluminum multi-layer thermal curtain was maintained $2.2^{\circ}C$ higher than that of control glasshouse in un-heating night time and the temperature in bed with root zone local heating was $4.7^{\circ}C$ higher than that in bed without local heating. Average heating coefficient of performance(COP) of the ground water source heat pump used in paprika cultivation was 3.7 and the glasshouse inside temperature was maintained at $21^{\circ}C$ of heating set up temperature. The heating energy consumptions per 10a were measured at 14,071L of light oil and 364kWh of electric power for the control glasshouse and 35,082kWh for the glasshouse applied heating package. As results, the heating cost of the glasshouse applied heating package was 87 percent lower than that of control glasshouse. The growths of paprika in glasshouses of control and applied heating package did not show any significant difference.

Rheological Properties and Roll Coating Dynamics of Basecoats for Precoated Automotive Metal Sheets (자동차 선도장 강판용 베이스코트의 유변학적 특성 및 롤코팅 동적 거동)

  • Lee, Dong Geun;Hwang, Ji Won;Kim, Kyung Nam;Noh, Seung Man;Jung, Hyun Wook
    • Journal of Adhesion and Interface
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    • v.16 no.1
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    • pp.15-21
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    • 2015
  • In this study, rheological properties and flow dynamics in roll coating process of basecoat paints have been investigated for automotive precoated metal (PCM) sheet applications. Various rheological properties for basecoats with three colors (black, blue, and silver), such as shear viscosity data at room temperature and elastic/viscous moduli under thermal curing condition, have been measured using a rotational rheometer. It is found that the relative portion of function groups inside basecoats and their viscosity level have greatly affected the formation of crosslinked networks by thermal curing. Also, operability coating windows for basecoats have been established in three-roll coating process system by observing their flow instabilities such as ribbing and cascade. It is confirmed that rheological approaches applied in this study have been usefully applied to develop environmentally-friendly PCM coating technology and optimally control the coating operations for non-Newtonian PCM paints.

Physical Properties of Liquid Ammonia Wood for Bending (휨가공을 위한 액체암모니아 처리재의 물리적 성질)

  • Kang, Ho-Yang
    • Journal of the Korean Wood Science and Technology
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    • v.31 no.1
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    • pp.52-60
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    • 2003
  • The physical properties of small hardwood and softwood specimens treated with liquid ammonia were investigated. The specimens treated for 4 or 18 hours were compared with the controls. The EMCs of the liquid ammonia treated specimens were higher than those of the controls when conditioned at the same humidities. However once oven-dried they didn't show any significant differences in EMCs. With the increase of liquid ammonia treatment time specimens shrank in radial and tangential directions, but not in longitudinal direction. As liquid ammonia treatment time increased the ultrasonic velocities of specimens decreased and their densities increased, thus their dynamic MOEs decreased. For chestnut specimens the presteamed were more plasticized than the liquid ammonia treated. Incising on the surfaces of specimens didn't improve liquid ammonia permeability in both hardwoods and softwoods. Liquid ammonia treatment was very effective for plasticizing 5 mm thick softwoods. Relative dielectric constants and thermal conductivities were measured with both liquid ammonia treated and control specimens.

The Finite Element Analysis and the Geometric Optimal Design of Linear Motor (리니어 모터의 유한요소해석과 기하학적 최적설계)

  • Lee Tae Won;Jung Jae Han
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.12
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    • pp.67-74
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    • 2004
  • Linear motor has been considered to be the most suitable electric machine for high speed and high precision linear motion control. Thrust of linear motor is one of the important factor to specify motor performance. Maximum thrust can be obtained by increasing the current in conductor and is relative to the sizes of conductor and magnet. But, the current and the size of conductor have an effect on temperature of linear motor. Therefore, it is practically important to find design results that can effectively maximize the thrust of linear motor within limited range of temperature. Finite element analysis was applied to calculate thrust and numerical solutions were compared with experiment. The temperature of the conductor was calculated by the thermal resistance which was measured by experiment. The optimum design process was coded by the ADPL of ANSYS which is a commercial finite element analysis software. Design variables and constraints were chosen based on manufacturing feasibility and existing products. As a result, it is shown that temperature of linear motor plays an important role in determining optimum design.

Electrical Properties and Preparation of 6FDA/4-4'DDE Polyimide Thin Films by Vapor Deposition Polymerization Method (진공증착중합법을 이용한 6FDA/4-4'DDE 폴리이미드 박막의 제조와 전기적 특성)

  • Hwang, S.Y.;Lee, B.J.;Kim, H.G.;Kim, Y.B.;Park, K.S.;Lim, H.C.;Kang, D.H.;Park, K.H.;Lee, D.C.
    • Proceedings of the KIEE Conference
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    • 1998.07d
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    • pp.1487-1489
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    • 1998
  • In this paper, thin films of PI were fabricated VDPM of dry processes which are easy to control the film's thickness and hard to pollute due to volatile solvents. From FT-lR, PAA thin films fabricated by VDP were changed to PI thin films by thermal curing. From SEM, AFM and Ellipsometer experimental, as the higher curing temperatures the films thickness decreases and reflectance increases. Therefore, Pl could be fabricated stable by increasing curing temperature. The relative permitivity and dissipation loss factor were 3.7 and 0.008. Also, the resistivity was about $1.05{\times}10^{15}{\Omega}cm$ at $30^{\circ}C$.

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Synthesis and Sintering of Cordierite by using Coprecipitation Method (공침법에 의한 Cordierite분말의 합성 및 소결에 관한 연구)

  • 한문희;박금철
    • Journal of the Korean Ceramic Society
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    • v.27 no.7
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    • pp.899-906
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    • 1990
  • The cordierite powders were prepared from Mg(NO3)2.6H2O, Al(NO3)3.9H2O and colloidal silica by the coprecippitation method, and the sintering behavior of the powders were investigated. Two different methods were applied for producing the precursor powders. The one was to added the aqueous solution of Mg(NO3)2.6H2O and Al(NO3)3.9H2O to NH4OH to adjust pH at 10 where the colloidal silica of pH 10 was added. The other wa to add the aqueous solution of Mg(NO3)2.6H2O and Al(NO3)3.9H2O to the colloidal silica with NH4OH to control the final mixture to be at pH 10. It was confirmed that more homogeneous powders were obtained from the latter method. The firing linear shrinkage of the powder compacts fabricated from the calcined powder between 90$0^{\circ}C$ and 110$0^{\circ}C$ was found to be larger as the calcination temperature was low. But all of them stopped shrinking around 120$0^{\circ}C$. The powder compacts, fabricated using the calcined powders at 90$0^{\circ}C$ and 95$0^{\circ}C$ for 2hours and sintered at 142$0^{\circ}C$ for 2hours, showed relative density of 93-96%, 3-point bending strength of 81-83MPa, KIC of 1.9-2.4 MPam1/2 and thermal expansion coefficient of 0.213-0.732$\times$10-6$^{\circ}C$.

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