This paper presents the results of full-scale experiments in a realistic building to evaluate natural convective heat and mass transfer through doorway-like apertures under small temperature differentials. The zone-to-zone temperature differences were nominally between re and 2.5°C. Heat transfer correlations, coefficient of discharge, and thermal stratification are reported for air (Pr = 0. 71), an enclosure aspect ratio of 0.26, aperture height relative to the enclosure height in the range of 0. 75 to l, and aperture width relative to the enclosure width in the range 0.29 to 0. 79.
The effect of airflow through an opening (or a crack) on the natural convection in a stairwell model is presented. The flow is driven by energy input from an electric panel heater located in the lower floor of the stairwell. The work concentrates on the effect of the size of inlet opening by varying it while keeping the area of the outlet constant. New data are presented for the measured temperatures and velocities at various cross-sections of the stairwell.
In order to evaluate the accuracy of COMIS predictions for large openings,and to study its sensitivity, two tests have been performed. In the first test, COMIS is used together with four existing multizone air flow models to calculate natural ventilation in a building for various climatic and opening configurations. In the second test, COMIS predictions are compared with single-sided ventilation measurements taken in test cells. The results of the tests are reported.
A sudden contamination of the outdoor air by some toxic gas can have several causes. To find out the protection afforded by sheltering indoors was the primary goal of the investigation. The object of the computational approach was a single family house with 2 floors. Three different models were utilized to calculate the infiltration air flows, the contaminant transport inside the building and the temperature decay of the building.
Direct capture efficiency of a local exhaust system is defined by introducing an imaginary control box surrounding the contaminant source and the exhaust opening. The imaginary box makes it possible to distinguish between contaminants directly captured and those that escape. Two methods for estimation of direct capture efficiency are given: (I) a numerical method based on the time-averaged Navier-Stokes equations for turbulent flows; and (2) a field method based on a representative background concentration.
There are many unanswered questions about the typical effects of duct system operation on the infiltration rates and energy usage of single-family residences with HVAC systems in their basements. In this paper, results from preliminary field studies and computer simulations are used to examine the potential for improvements in efficiency of air distribution systems in such houses. The field studies comprise thermal and flow measurements on four houses in Maryland. The houses were found to have significant envelope leakage, duct leakage, and duct conduction losses.
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