heat transfer

The actual heating load of a building differs often from the designed load. One reason for this is the uncontrolled ventilation through a building envelope. The heating load of air infiltration has, in practical calculations, been calculated according to the predicted leakage flow rate and to the indoor and outdoor air temperature difference. We suggest, however, that the value of transmission heat losses should be corrected by a factor, Nusselt number, because of the thermal interaction of leakage flows and conduction heat transfer in wall structures.

The design of a low cost ventilation air heat exchanger which utilizes plastic sheets as the heat transfer surface is presented. Laboratory tests on such acounter flow heat exchanger have demonstrated very high values of overall heat transfer coefficients, heat exchanger effectiveness, and temperature recovery when the flow is laminar and buoyancy effects assist the heat transfer. The costs of such heat exchangers would make them attractive for many building applications.

In order to obtain means for determining realistic convective heat transfer coefficients, a hierarchy of interacting and interdependent calculation methods have been developed by the authors. Both higher and lower level models have been used to develop and verify an 'intermediate level' computer code, which formed the basis for generating input convective heat transfer data for dynamic building models. The contribution considers the computation of convective heat exchange within three-dimensional, rectangular enclosures when buoyancy effects are significant.

Investing in insulation is a good way to reduce energy consumption in the home. The homeowner must determine where adding insulation will be most cost effective. Attics are usually the place to start, followed by floors and walls. Since there is a wide variety of material on the market, thedo-it-yourselfer must choose carefully and install them with proper regard for ventilation and vapour barriers. Even if the work is performed by a contractor, the informed homeowner will benefit by his knowledge of materials and procedures.

Factsheet on the solar greenhouse, including an introduction to the design differences between solar and traditional greenhouses, and sections on the attached solar greenhouse, the role of conservation, solar greenhouse additions: zoning, siting the solar greenhouse, design of the solar greenhouse, framing, building permits, foundation and structure, glazing, thermal mass, heat transfer, summertime operation and cost and performance.