This report contains a brief description of an air infiltration measuring device jointly developed by the National Bureau of Standards and Princeton University's Center for Environmental Studies. The device maintains a constant concentration of a tracer gas (SF6) in each room of a structure by injection, and relates the infiltration rate for each room to the rate of gas injected. Specifics of construction and use are included.
The purpose of this research project is for the Thermal Engineering Section of NBS to conduct air leakage measurements on selected large buildings tovalidate calculation formula developed by Shaw and Tamura, (see Shaw, C.Y., and Tamura, G.T., 'The Calculation of Air Infiltration Rate Caused by Wind and Stack Action for Tall Buildings', ASHRAE Trans., Vol. 83 part 2).
This report describes a technique which models the infiltration process for an entire enclosure more accurately than standard methods. Both air flow and convective/conductive heat transfer are accounted for to (a) improve building heat load calculations, (b) determine the important characteristics of existing (and new) buildings for infiltration heat loads, and (c) account more accurately for wind effects.
This is done by means of a fan pressing air into the interior of a not air-tight greenhouse. The amount of exchanged air is measured by equipping the fan with a wind tunnel, it is depending on the difference of pressure between the inside and outside of the greenhouse. The difference of pressure and the air exchange figures are applied to the natural conditions in the case of different air velocities.
In the early stages of the project on thermal performance of our experimental masonry building, measurements were made to determine the magnitude of air exchange between the building and the surrounding chamber during the process of cyclic temperature changes. Since wind forces were negligible during the testing period,the major driving force influencing the change of air was the thermal difference between the air inside of the building and that of the surrounding air in the chamber.
The air change rate in a single story office building was measured using atracer gas technique. The air change rate was determined by the rate of decay method using sulfur hexafluoride as the tracer gas. A total of eight tests were conduc
The heating of air infiltrating through cracks around doors and windows forms an important part of the heat balance of buildings. The complexity of the problem makes it difficult to calculate. Describes the development of an insitu method for measuring the infiltration of buildings.
Computer programs INFILS and ACFES2/R have been developed for the analysis of industrial buildings' heating loads and energy consumption relating to air infiltration. The heat demand computation results for typical hall structures are presented. It is shown that on windy days with low outside temperatures, total heat losses rose to 180% of basic heat losses. The necessity of developing proper methods for designing, building and testing elements of industrial buildings is emphasized.
The interaction of air leakage and transmission heat through a double frame window makes the overall heat loss less than the sum of them acting separately. Theoretical calculation shows that in the case of infiltration, a double frame window may recover 21% to 32% of air leakage heat loss, and exfiltrated air through a double frame window not only loses no energy but, on the contrary, reduces the energy consumption of heat transmission, covering 23% to 36% of the enthalpy drop of exfiltrated air before and after leakage. Experimental data and field test agreed well with these results.
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