Macroscopic flow numbers relating to the jet momentum of air diffusion terminal devices are studied in this paper. Diffuser jet momentum, jet momentum number and jet momentum ratio are reviewed in the literature. New expressions for jet momentum ratios and jet volume numbers are proposed for specifying the mean room air speed in mechanically ventilated enclosures. The proposal is validated against experimental data from seven sites under fifteen operating flow conditions. Two macroscopic flow numbers correlate with the measured mean air speed in the room.
To investigate the effect of ventilation on indoor radon (222Rn), simultaneous measurements of radon concentrations and air change rates were made in 117 Danish naturally ventilated slab-on-grade houses built during the period 1984-1989. Radon measurements (based on CR-39 alpha-track detectors) and air change rate measurements (based on the perfluorocarbon tracer technique; PFT) were in the ranges 12-620 Bq m-3 and 0.16--0.96 h-1, respectively. Estimates of radon entry rates on the basis of such time-averaged results are presented and the associated uncertainty is discussed.
An extensive survey has been carried out in 52 underground car parks in Hong Kong focusing on carbon monoxide concentrations in the air. So far as short term health effects are concerned this compound is generally regarded as the most important chemical species from car exhausts. Its presence can be used to quantify air pollution, and give an indicator of the air quality in car parks. The sites were sampled during peak hours. This report presents the results and analysis of the carbon monoxide levels measured.
Trees, displacement ventilation and the use of thermal mass all played their part in giving the Green Building of the Year Award to the Ministry of Defence. Ewen Rose gets under the skin of the winning building.
Demand controlled ventilation systems can be used to minimise energy consumption whilst maintaining satisfactory levels of indoor air quality (IAQ). As an alternative to C02 sensors IAQ sensors (based on Taguchi mixed gas sensors) can be used to infer levels of IAQ. This Technical Note provides details of a series of laboratory and site tests to determine the performance of a range of IAQ sensors.
The paper examines the extent to which user's intervention may compromise the therrmal performance of small sunspaces in the context of a Solar Energy Demonstration Project at Easthall in Glasgow (55°52'N), which was monitored from September 1992 to May 1994. Results indicate a tendency to close down windows etc. late in autumn and open them up early in spring relative to heat demand. In other words a user – driven energy load due to ventilation is higher in autumn and spring than in the central winter period.
In a way most heat pumps recover or reclaim heat energy for space heating and cooling, water heating or process heating. In the building sector, the natural heat sources which heat pumps transfer to useful heat, such as outside air, the ground, ground water and sea/lake/river water are in fact all heat sources that consist of solar heat and cannot be directly used for heating due to their temperature. Hence, one can argue that heat pumps which use these sources are (solar) heat-recovery devices.
This article describes the retrofitting of a five-family apartment building, implemented as a pilot and demonstration project for the Swiss Federal Office of Energy. The fact that this building on Mutschellenstrasse in Zurich is a listed building, imposes restrictions to the retrofitting process. However, the cellar ceiling, the roof and part of the building facade have been insulated, new windows have been installed and three apartments have been fitted with a mechanical ventilation system with heat recovery. Heating is provided by heat pumps.
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