Measurements reported in this paper demonstrate the increase in heat transfer due to convective air flow that can occur in wood-frame walls containing air-permeable mineral wool insulation with air spaces in contact with both sides. The effect of this air interchange between the air spaces increases with increasing temperature difference, air space height and air permeability of the insulation. Use of mid-height blocking and higher density insulation thus resulted in some reduction in the heat flow through the insulation, although convective effects were still significant.
Theoretical relationships have been developed to describe the heat transfer by combined fluid conduction-convection through air-permeable insulation with vertical air spaces adjacent to both surfaces. The fluid conduction-convection is shown to be a function of fluid properties, air flow coefficient of the insulation, insulation height and thickness, and temperature difference. A correlation in terms of dimensionless groups has been derived. Results of measurements on a 4-ft high insulation specimen over a temperature difference range from 30 to 90F were in agreement with the theory.
This paper presents a numerical calculation method for a two-dimensional, isothermal, turbulent room air movement. In this case, the time averaged stream function-vorticity equations were represented by finite differencing approximations
Flat wood-frame house roofs with insulation applied between joists are susceptible to condensation problems in cold climates. Investigation of difficulties experienced in a wood-frame row housing project in Eastern Canada showed that many interrelated factors contribute to the occurrence of problems and demonstrated that control of air leakage through the ceiling is the one primary requirement for successful performance.
Effects of vertical shaft venting on smoke movement in tall buildings are examined in order to obtain conditions for minimum smoke filtration into upper floors, stairways, and elevator shafts during fires. Results show that sufficient bottom venting will nearly eliminate flow of air into shafts, while top venting reduces flow from shafts. Either should reduce smoke transfer between levels. Multiple shaft buildings benefit from top ventingsome and bottom venting others, reducing necessary vent size for sufficient ventilation.
A computer analysis of stack effects in a large multi- storey building was performed, comparing the air flow (and consequent hypothetical smoke concentrations at higher floors) with and without a smoke shaft. Additionally, tests were performed on one building using one of two stairwells as a smoke shaft. Results indicate that a smoke shaft can be effective in limiting smoke movement to upper stories, as long as the fire floor is not open to outside air (such as by a broken window), or the smoke shaft is not open to a floor higher than the fire floor.
This paper describes a set of velocity measurements which were made within a series of models of rectangular enclosures whose dimensions in plan were varied, the heights of the walls being held constant. The airflow's speed was measured at each of the points of a rectangular grid and the arithmetic mean of these measurements was adopted as a measure of the enclosure's performance in providing shelter from the wind, and was used to compare the effectiveness of one geometry against another. It was found that the degree of shelter could be optimised by a correct choice of geometry.
The appearance of bubbles used for flow visualisation around bluff bodies in a wind tunnel is illustrated. It is demonstrated that the large diameter and low density properties of bubbles could enable them to represent raindrops in a wind tunnel.
Substantial work on ventilation effectiveness has been carried out in Norway and Sweden using tracer gas techniques based on fundamental physical and mathematical concepts. The nature of, and how to characterize by using tracer gas techniques, the flow of ventilation air and contaminants through a ventilated room is known. Displacement flow has been proved to be the best flow principle for ventilation, and in general ventilation air should be supplied to the occupied zone.
For proper control of the ventilation in a building, it is necessary to know the factors involved. These include (1) the climate, including temperature, wind direction, and wind velocity, (2) the building performance, (the interconnections b
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