duct

The fan and the ductnetwork is designed for 100% ventilation rate. Because the fan energy is the main important energy consumption in systems all over the year it is worthwhile to control the systems correctly. By reducing the air volume rate the pressure drop in the ductnetwork drops nearly with the second power.

The adequate ventilation of houses is essential for both the occupants and the building fabric. As air-tightness standards increase, background infiltration levels decrease and extra ventilation has to be designed into the building. Passive stack ventilation has many advantages - particularly when employed in low cost housing schemes - but it is essential that it performs satisfactorily. This paper give the results from monitoring two passive stack ventilation schemes.

The aim of the study was to identify methods for the renovation of ventilation systems in domestic buildings which are 3 - 8 storeys high. Three typical buildings were selected and the problems in ventilation were examined. The designers made their proposals for repairs and the research team analyzed the solutions and made improvements. The special problems compared with new buildings included less airtight building envelopes and leakages in existing ventilation ducts.

BRE have experimental data for the flows found in Passive Stack Ventilation (PSV) ducts from a test house in Garston. These data cover different duct diameters, number of bends and roof terminals, all measured over a variety of weather conditions. In the first part of this paper the data are analyzed to separate temperature and wind effects, and to see how well they fit well to the expected model of duct flow. The second part gives a comparison of the same data with predictions from the single zone ventilation model BREVENT.

A possible alternative to mechanical extract ventilation for kitchens and bathrooms is passive stack ventilation (PSV). BRE has carried out work on this type of system in a test house under controlled conditions. To find out how well they worked in practice, four occupied dwellings were monitored over a period of 2 - 3 weeks each. Each dwelling had two ventilation ducts. Air flow rates within the ventilation ducts were measured, together with humidities, temperatures and climatological data.

The Building Research Establishment has set up various passive stack ventilation systems (PSV) in a test house in order to assess their performance. The test house used was a two storey, end terrace dwelling on the BRE site at Garston. A PSV was installed in the kitchen of the test dwelling. The duct material, diameter and configuration were varied to determine any differences that they would make to the air flow rates obtained in the duct. In addition, three different ridge terminals were tested and three ceiling inlets.

An effort has been made to gather the information available about duct cleaning. The emphasis in the survey was on the hygienic aspect of the cleaning of supply air ducts. Most of the literature deals with cleaning of exhaust ducts. Guidelines for the cleanness of ductsurfaces have been given by some organizations, but the scientific basis for such guidelines needs more research.

This work examines the application of the constant-injection and pulse-injection tracer gas techniques for measurement of airflow in rectangular ducts. Experiments were carried out in ducts with aspect ratios of 1,2, and 4. Tracer gas measurements were generally similar to measurements made using a pitot tube. Relationships for the friction-factor and hydrodynamic entrance length are presented for Reynolds number between 73,300 and 395,000.

This report presents the results of a study on the efficiency of residential duct cleaning. The study was performed In 33 houses and describes the results of measuring duct flows, fan amperage, dust, and micro-organisms before and after duct cleaning. The study concludes that there were no significant improvements in duct flows, fan amperage, duct airborne dust, house airborne dust, or supply duct dust levels. Only dust concentrations in the return ducts and the concentrations in airborne micro-organisms have significantly improved after the duct cleaning.