Investigation of heat transfer performance in fenestration system based on finite element methods

In this dissertation, two-dimensional heat transfer through fenestration systems will be numerically modeled and analyzed. The numerical investigation consists of three major parts: (1) New heat transfer correlations for two-dimensional convective heat transfer across the rectangular cavities of Insulated Glazing Units (IGU\u27s); (2) The instability of two-dimension natural convection in rectangular cavities of IGU\u27s; (3) Two-dimensional condensation resistance investigation for IGU\u27s of fenestration system. Laminar natural convection models will be developed for both part 1 and 2 studies. The imposed boundary conditions are constant temperatures at the side walls and zero heat flux at the top and bottom surfaces. For the purpose of evaluating window thermal performance, a new set of convective heat transfer correlations is to be developed as functions of both aspect ratios and Rayleigh numbers based on the numerical calculations. Since the instability generally results in higher heat transfer rates across the window cavities as well as complex temperature distributions on window surfaces. Therefore the instability regime definition becomes essential, and based on the resulting regime definition more accurate heat transfer results as well as the local temperature distributions can be resolved. A set of detailed convective, radiative and conductive heat transfer numerical models will be developed in the condensation resistance investigation for several different sets of boundary conditions. One set of boundary conditions is variable surface heat transfer coefficients on the indoor and outdoor glass surfaces. Seven IGU\u27s will modeled and analyzed for this study. Comparisons is to be made between the numerical calculations in this studies and the available experimental and numerical results done by other researchers