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This study concerns the flow and heat transfer characteristics of a turbulent submerged circular air jet impinging on a horizontal flat surface when free stream turbulence exceeds 20 percent. The turbulent fluctuations of the free stream velocity are the primary aerodynamics influencing heat transfer. Two regions with distinct flow characteristics are observed: the stagnation region, and the wall-jet region. According to the linear form of the energy equation, the surface heat flux may be decomposed into laminar and turbulent components. An inverse methodology can determine the turbulent component of the heat transfer coefficient in the stagnation region and in the wall-jet region as a function of the root mean square value of the fluctuating component of velocity in the bulk flow direction.

A transient, one-dimensional thermal model that incorporates combined conduction, radiation heat transfer, and moisture transport for residential attic insulations has been developed. The governing equations are the energy equation, the radiative transport equation for volumetric radiation within the insulation batt, and the species equations for bound H 2 O and vapor H 2 O. A simultaneous solution procedure with a Eulerian control volume-based finite difference method was used to solve the energy equation and the species equations. The method of discrete ordinates was used in solving the radiative transport equation. For H 2 O transport, both diffusion of vapor H 2 O and bound H 2 O, and moisture adsorption/desorption within the insulation binder are included in the model. The experimental data measured at an occupied North Mississippi residence for R19STD (standard R19 fiberglass insulation batt without a foil radiant barrier) were used to validate the model which predicted heat fluxes for summer, spring, winter, and fall seasonal conditions. These predictions were compared with the measured heat flux data and the predictions from the dry model (without the moisture transport). Various profiles such as temperature-time histories, relative humidity time histories, spatial H 2 O concentrations, spatial temperatures, and spatial heat fluxes are presented to explain the overall heat transfer behavior. Nomenclature c f = specific heat, J/kg-K e b = blackbody flux, W/m 2 h ad = heat of adsorption/desorption, J/kg / = radiative intensity, W/m 2 -sr i b = specific enthalpy of bound H 2 O, J/kg i v = specific enthalpy of vapor H 2 O, J/kg k = thermal conductivity, W/m-K m b = bound mass concentration, kg bound H 2 O/m 3 m b = rate of absorption of H 2 O, Eq. (6), kg bound H 2 O/m 3 -s m v = vapor mass concentration, kg vapor H 2 O/m 3 m^ = constant in Eq. (6b), Table 1 n = refractive index of medium q = source/sink term, W/m 3 q r -radiative component of total heat flux, W/m 2 q T = total heat flux, W/m 2 RH = relative humidity T = temperature, K T A = attic temperature, K T c = ceiling temperature, K Tj = inside room temperature, K T R = roof temperature, K T r = reference temperature, 300 K T s = bottom of the batt temperature, TO -top of the batt temperature, K t = time, s X = mass of absorbed moisture/mass of dry fiberglass, kg H 2 O/kg fiberglass y = physical thickness, m y 0 = thickness of insulation batt, m ft -extinction coefficient, r = /3y, cm" 1 K y b = diffusion coefficient of bound H 2 O, m 2 /s y v = diffusion coefficient of vapor H 2 O, m 2 /s e w = emissivity of the roof s s = emissivity of the substrate 0 = polar angle, deg /z, = cosine of polar angle p f = density of fiberglass, kg/m 3 p n = reflectivity of the roof p s = reflectivity of the substrate T = optical thickness T O = optical thickness, /3y 0 O = scattering phase function 4> = relative humidity i/r = azimuthal angle 0} = single scatter albedo Subscripts b = bound / = fiberglass v = vapor 0 = top surface

By implementing various substrate barriers to a R-30 fiberglass insulation batt, this research shows the overall changes in the substrate heat flux. Independently, a plastic vapor barrier, and both a perforated and nonperforated radiant barrier are analyzed in this study. Conduction, radiation heat transfer, and moisture (mass) transport are considered to be the main contributors to heat transport within attic fiberglass insulation. A transient, one-dimensional, computational thermal model has been developed to simultaneously model all three of these heat transport mechanisms, which allows the total heat flux at the attic insulation substrate to be predicted. This numerical model has the capabilities to determine the effect on each of the three modes of heat transfer once a substrate barrier has been added. Summertime experimental data were collected at an occupied North Mississippi residence for cases with and without a vapor barrier at the substrate for R-30 fiberglass insulation. Within this investigation, experimental and predicted total heat transfer results are compared and analyzed. Profiles such as temperature-time histories, vapor H 2 O concentrations, and individual modes of heat transfer plots are presented to support the experimentally determined overall effects on the heat transfer at the substrate once a substrate barrier has been implemented.