neutral pressure level

Air curtains are used to eliminate airflows through doorways (doorway tightness). In this paper the impacts of air circulation, jet discharge momentum flux and nozzle design parameters on the tightness of an upwards blowing air curtain are presented. The tightness values were measured using a tracer gas decay method in the laboratory hall. Measurements were undertaken for two nozzle widths, 30 mm and 120 mm, and for two different discharge angles, 10° and 30°.

A study has been made, both experimentally and analytically, on the characteristics of thermal performance of high-rise buildings using a simulated model building with five floors and a number of exterior openings under various temperature distributions. The effect of the temperature variation on the location of the neutral pressure level (NPL) was of particular interest of the present study.

An analysis has been made of draft failure with residential heating units operating at low rates of combustion during mild, calm weather. It has been shown that under these conditions the relation between chimney draft andhouse pressures becomes important in determining when venting failure will occur. A simple equation expressing this relation has been developed. It shows that draft failure will occur if the mean flue gas temperature in the chimney falls below a value that depends on the neutral zone level.

The use of lightwells and courtyards for natural ventilation in high-rise buildings is exaimed using both wind tunnel and field measurements of the pressures and neutral pressure zone caused by wind and temperature differences. Though air flow patterns are complex for complex building designs, air exchange rates in lightwells and courtyards were generally seen great enough to assure clean air for natural ventilation via air infiltration. However the cost of land in urban settings will probably make mechanical ventilation systems the economic choice.

A study has been made, both experimentally and analytically, of the characteristics of thermal performance of high-rise buildings using an idealized model building with a number of openings at various locations and temperature distributions. The building was assumed to have no internal partitions. The effect of the factors affecting the location of the neutral pressure level was of particular interest.

Air change rates were measured in one two-storey detached house with five basic types of passive ventilation systems: an intake vent in the basement wall, an outdoor air supply ducted to the existing forced air heating system, an exhaust stack extending from the basement to the roof, and two combinations of the supply systems and the exhaust stack. An expression was developed for estimating house air change rate from house airtightness, neutral pressure level and indoor-outdoor air temperature difference.

Describes a general model for air infiltration which will accomodate wind pressures, stack effect and ventilation openings provided the vents are either all above or all below their respective neutral pressure levels. States that main innovation of this model is expressing the infiltration as a function of the shell leakage and of the neutral heights of each face.Describes experimental method for finding the neutral pressure level. Gives typical values of parameters for tight mid-westhouses for light and strong wind.