Parametric analysis of radiant and convective heat transfer in underfloor heating system
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Radiant Heating Systems by balancing four main convenience factors i.e., environment temperature, Radiant heating, air flow and relative humidity provide convenience for human. In these systems, high percentage of obtained heating is radiantly. In this study, surface radiant heat transfer rate with conductive and natural convective heat transfer in a model enclosure heated by radiant system is investigated experimentally and theoretically. For this purpose an enclosure by 240 240 240 cm3 is fabricated, then insulated and equipped by heating system and finally tested. A model based on the net-radiation method is employed to compute the radiation exchange between surfaces. The radiation model assumes opaque, diffuse and gray surfaces, a nonparticipating medium, and uniform incident and hence reflected energy flux and temperature. In this method internal and external surface temperature of enclosure for determining radiant heat transfer is required. For this study, the surface temperatures were measured using type k thermocouples and thermometer. In net radiation method, view factors and surface temperatures are required for computing radiant heat transfer. These calculations are done by MATLAB program. After calculation radiant heat transfer by net radiation method, conductive and convective heat transfer rate were computed. Results are shown, in the underfloor heating systems, 75-80 % heat transfer of floor and in radiant ceiling heating systems 90-98 % heat transfer of ceiling is radiation heat transfer.Keywords:
Enclosure
Radiant energy
Radiant heating
Radiant cooling
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Based on the network method for radiant heat transfer, a radiant space resistance ke R /4F1 was proposed, the radiant heat transfer network diagrams which subjects to the radiation attenuation was given in this paper, this method is helpful to accurately analyze the zero-dimensional radiant heat transfer. Simulation results show that, due to the radiant space resistance kR /4F, the total thermal resistance between the flame and the water wall surface is degraded, radiation attenuation from the flame center to water wall surface should not be ignored. It is also shown that,when the radiation attenuation is involved, the furnace outlet flue gas temperature utilizing the furnace ɛf syn blackness is more accurate than the Soviet Union 1973 calculation standard.
Thermal Radiation
Intensity
Radiant intensity
Radiant heating
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Two experiments have been conducted to study radiative heat transfer in lightweight fibrous insulations (LWFI). The spectral extinction coefficients for a commercial LWFI have been measured via transmission measurements, and a guarded hot plate apparatus has been used to measure the radiant heat flux as well as the total heat flux in the insulation. The experimental results are compared with the theoretical values calculated according to the analytical models presented in Part I of this paper. The comparisons reveal that the analytical models are useful in giving representative values for the radiative properties of typical LWFI. However, only qualitative agreements have been obtained for the heat transfer results.
Radiant flux
Radiative flux
Extinction (optical mineralogy)
Thermal Radiation
Radiant heat
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Radiant flux
Thermometer
Thermal Radiation
Mean radiant temperature
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1次元輻射半透過性媒体の輻射加熱に関して, 媒体の射出を考慮に入れて温度応答ならびに定常状態温度分布および熱流束分布を理論的に解析した.解析結果は本実験範囲内において実験結果と良好な傾向的一致を示し, 本理論解析の妥当性が確かめられた.また, 内部加熱効果が温度応答, 定常状態温度分布および熱流束分布に顕著な影響を及ぼし, その程度は入射輻射線の主要な振動数域における媒体の単色光学的厚さと境界壁の単色射出率の大きさに強く依存することを明らかにした.
Radiant heating
Internal heating
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Radiant heat
Throttle
Radiative Cooling
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also been given in international standards for experimental approaches. In accordance with the experimental standards, the analyses are realized at the room dimensions of (L x H x W= 4 x 3 x 4 m), and at the thermal boundary conditions of (Tc= 35 – 50oC), (Tw= 15 – 24oC), (Tf= 15 – 24oC). As a result of iterations conducted using a computational fluid dynamics package program code, each corresponding to a case study, convective, radiative, and total heat fluxes from radiant heated ceiling are obtained, and afterward using relevant reference temperature proposed in the literature, heat transfer coefficients pertaining to convection, radiation, and total heat transfer have been found. In conclusion, average heat flux values of 95.83 Wm-2 and 17.49 Wm-2 are gained through the examined radiant heated ceiling, by means of radiation and convection, respectively. This denotes that roughly 85% of total heat transfer from the ceiling arises through radiation that is very compatible with the relevant literature. Finally, spanning the entire different case studies, average convective, radiative, and total heat transfer coefficients of 1.1 Wm-2K-1, 5.4 Wm-2K-1, 7.6 Wm-2K-1 are acquired.
Ceiling (cloud)
Thermal Radiation
Radiative Cooling
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We have developed an analysis method of radiation heat transfer in a radiant cooled space. This method can be applied to a complicated situation where various objects are contained in the space. The steady-state cooling environment of a room with a cooled ceiling panel was analyzed.
Ceiling (cloud)
Thermal Radiation
Radiant cooling
Radiant heating
Radiant energy
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