pressure

Room pressure differential is an important aspect in order to guarantee sufficient contamination control, but is difficult to control in airtight cleanrooms. This research uses simulation models to get an understanding and to quantify the room pressure controllability of airtight cleanrooms. The most influential parameters on the room pressure controllability are identified using a sensitivity analysis. The effects of the shell airtightness and overflow flowrates are quantified, and the effect of a flow/pressure cascade with three coupled rooms is investigated.

This paper presents an integrated damper and pressure reset (IDPR) method for variable air volume (VAV) system fan control. The IDPR method controls the static pressure at a minimum required level while maintaining at least one terminal box damper at full open position. When the entire system

Measurements results are compared with calculations for predicting the broadband noise from low and high pressure axial fans.

This article describes the physical mechanisms leading to broadband noise from axial fans. It gives the results of a literature survey about the semi-empirical correlations available to predict this noise and their application to two examples : a low pressure fan and a high pressure fan.

A new model has been proposed for evaluating the discharge coefficient and flow angle at an inflow opening for cross-ventilation. This model is based on the fact that the cross-ventilation flow structure in the vicinity of an inflow opening creates dynamic similarity under the condition that the ratio of the cross-ventilation driving pressure to the dynamic pressure of cross flow at the opening is consistent. It was confirmed, from a wind tunnel experiment, that the proposed model can be applied regardless of wind direction and opening position.

The proposed local dynamic similarity model of cross-ventilation predicted ventilation flow rates more accurately than the conventional orifice flow model assuming constant discharge coefficients when discharge coefficients actually decreased with change of wind direction. This model was used to develop a new method for evaluating the ventilation performance of window openings. The obstructive effect of model size on flow fields in a wind tunnel was avoided by installing the opening parallel to the wind tunnel floor.

The wind and buoyancy pressure driving forces for natural ventilation of buildings are very low, typically less than 10 Pa. Depending upon the prevailing climatic and thermal conditions, or even the location of a building on a site in relation to other surrounding buildings and landscape, the predominant pressure force incident on a purpose-provided natural ventilation opening can either be closer to the lower range of pressure differentials (< 2 Pa) or vary over a wider range of higher pressures (2 - 10 Pa).

Air infiltration continues to play a major role in the ventilation of houses, despite modern trends to increased airtightness of the building envelope. In colder climates, stack effect is the principal driving force for this natural air exchange. The neutral pressure level divides the envelope areas subjected to stack effect pressures driving infiltration from those subjected to pressures driving exfiltration. The neutral pressure level is therefore important to our understanding of stack driven air exchange and our ability to model it.