دانلود رایگان مقاله لاتین ضریب انتقال حرارت جابجایی در ساختمان از سایت الزویر
عنوان فارسی مقاله:
مدل پویا برای اندازه گیری ضریب انتقال حرارت جابجایی در سطوح خارجی ساختمان
عنوان انگلیسی مقاله:
Dynamic model for measurement of convective heat transfer coefficient at external building surfaces
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
The convective heat flux qc (W m2 ) from the building aboveground external surface is an important heat transfer process in the simulation of building energy performance. Usually, qc is expressed as: qhTT c= − cs a ( ) ( ) 1 where hc (W m2 K1 ) is the CHTC, Ts (K) is the building exterior surface temperature, and Ta (K) is the outdoor air temperature. The hc coefficient depends on several factors, for examples building geometry, surface roughness, air flow pattern, and wind speed V (ms1 ) at some reference position. Many empirical models exist that correlate hc and V in specific cases, some based on wind tunnel studies of flat plates (see e.g. Jürges [1]), while other models stem from field hc measurements, using a sensor placed on the building surface [2–6]. There is a high uncertainty in the hc values predicted by such empirical correlations, and when these values are used as input data to BES programs, this leads to uncertainty in the simulation results [7,8]. Part of the uncertainty in predicted hc values from empirical models is due to measurement error in hc. There exists several methods for measurement of the heat flux and external CHTC (see reviews by [9–11]). Among these methods, the most commonly used within the field of building physics for measurement of CHTC is the heated gradient sensor type, as pioneered by Ito et al. [2]. The heated gradient sensor consists of a gradient heat flux meter (HFM), heated from its back side, using a resistive heater, and equipped with a thermometer for measurement of its front surface temperature Ts (K). The HFM estimates the conductive heat flux qd (W m2 ) through the sensor by measuring the temperature gradient across a slab, using a series of thermocouples. The sensor front surface is in contact with the air boundary layer, whose hc value is to be measured. The momentary heat balance of the sensor front surface is given by: q Iaq q d+ =+ s/ r c ( ) 2 where a is the sensor surface area, Is (W) is the short-wave solar radiation, and qr (W m2 ) is the net thermal radiation: = − ε σ ( ) ( ) q TT r s s r 3 4 4 with εs ¼ the surface emissivity, s ¼ the Stefan-Boltzmann constant (5.67 108 W m2 K4 ), and Tr (K) ¼ the mean radiant
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کلمات کلیدی:
New external convective heat transfer coefficient ... - ResearchGate https://www.researchgate.net/.../235952489_New_external_convective_heat_transfer_... Building energy analyses are very sensitive to external convective heat transfer coefficients so that some researchers have conducted sensitivity calculations ... [PDF]Review of external convective heat transfer coefficient models in ... www.urbanphysics.net/2013_MM_DC_BB_JH_ATE_CHTC_review__Preprint.pdf by M Mirsadeghi - Cited by 66 - Related articles Convective heat transfer coefficients for external building surfaces (hc,ext) are ... simulation (BES) to calculate convective heat gains and losses from building ... [PDF]CFD Analysis of Convective Heat Transfer Coefficient on ... - MDPI www.mdpi.com/2071-1050/7/7/9088/pdf by AL Vollaro - 2015 - Cited by 11 - Related articles Jul 13, 2015 - Abstract: Convective heat transfer coefficients for external building surfaces are essential in building energy simulation (BES) to calculate convective heat gains and losses from building facades and roofs to the environment. Buildings.HeatTransfer.Convection.Exterior Buildings.HeatTransfer ... simulationresearch.lbl.gov › Home › Modelica May 4, 2015 - If conMod= Buildings.HeatTransfer.Types.ExteriorConvection.Fixed , then the convective heat transfer coefficient is set to the value specified by ... [PDF]convective heat transfer coefficients: experimental ... - SciELO México www.scielo.org.mx/pdf/ccid/v5n2/v5n2a3.pdf by J Chávez-Galán - 2014 - Related articles Keywords: convection, heat transfer coefficients, wind tunnel, solar global irradiation, ... Studies about convection heat transfer in buildings are focused mainly on .... The box container had exterior dimensions of 0.6 x 0.7 x 0.2 m and internal ... CFD analysis of convective heat transfer coefficient on external ... https://sapienza.pure.elsevier.com/.../cfd-analysis-of-convective-heat-transfer-coefficie... by A de Lieto Vollaro - 2015 - Cited by 11 - Related articles Convective heat transfer coefficients for external building surfaces are essential in building energy simulation (BES) to calculate convective heat gains and ... [PDF]analysis of wind-driven flow and external convective heat transfer ... www.ibpsa.org/proceedings/BS2005/BS05_0287_294.pdf by MG Emmel - 2005 - Cited by 1 - Related articles context, a Computational Fluid Dynamics (CFD) program has been used to predict external convective heat transfer coefficients at external building surfaces. An indirect validation of convective heat transfer coefficients (CHTCs ... link.springer.com/article/10.1007/s12273-015-0212-0 by J Liu - 2015 - Cited by 6 - Related articles Jan 19, 2015 - An indirect validation of convective heat transfer coefficients (CHTCs) for external building surfaces in an actual urban environment. Authors ...
