crack

Describes the network procedure for calculating the most energy-conserving and economical form of natural ventilation of a building. Provides application examples in the form of the determination of mass air flows through doors and windows and cracks in industrial work sheds. Provides the results of a calculation of crack ventilation in winter with mechanical ventilation with positive pressure, plus optimisation of air flow through a cooling bed for hot rolled steel sections.

The pressure drop and flow characteristics of short capillary tubes have been investigated experimentally for length-to-diameter ratios varying from 0.45 to 18 at diameter Reynolds numbers ranging from 8 to 1500. In the range of the dime

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.

Describes the first stage of a project to study domestic background leakage. Fundamental flow measurements have verified the crack flow equation for the simplest crack type for a much larger range of crack and flow parameters than have previously been examined. It is hoped to develop a portable, automated pressurization system capable of identifying and quantifying background leakage areas in rooms.

Simulation of the thermal performance of a building to take account of uncontrolled infiltration shows that infiltrating air on a leakage path is efficiently warmed up, especially if infiltration flow rates are low. For allowable infiltration flow rates with respect to thermal comfort, (0.5 -0.7 dm3/sm), the heating is 25 - 60 per cent of the temperature difference between the outside and inside air. For the longest leakage path, the incoming air is even near to the room air temperature.

The normally used equation for calculation of infiltration flow rates into a house is a power law of which the exponent n is normally assumed to be 0.66 but sometimes values of 0.5 or even 1 can be seen in the literature. In this paper the constant n is calculated assuming a non fully developed infiltration flow. The constant n will for this assumption take values between 0.67 and 0.77 if the slots where the flow takes place are long enough to get a flow close to a developed one.

Reports TNO-IMG research into ventilation of houses including the influence of cracks, open windows, weather conditions, occupants' behaviour, pollutants and guidelines. Lists conclusions such as an opened window renews the room air within half an hour. 40% of the occupants open windows for too long, 27%ventilate insufficiently, 25% of the dwellings are air tight, 75% leaky. Ventilation occurs partially through shafts (30%) and cracks (60%).Ventilation rates differ considerably between the rooms in a house.Ventilation ducts should have an exhaust function.

Reports measurements on air transport through homes made by a committee working a Dutch Standard on Heating Load Calculation similar to DIN 4701, but taking account of air infiltration losses through joints and cracks between glazing, window-frame and facade construction. Describes the measuring method applied. Tables air leakage coefficients c and flow exponents, n ,of a number of flats and single family houses. Also tables c and n values of cracks according to type of construction and material, use of weather strips and measuring institute.