diffusion

In a previous study, a whole room IAQ model consisting of multi-phase emission/sorption model for wall materials and room volume mass balance model catering for practical ventilation schemes was developed. The interactions between volatile organic compounds (VOCs) and building materials composing different building components can thus be modeled based on fundamental mass transfer theories. In the present study, the effects of various ventilation strategies and outdoor source on the indoor gas phase VOC concentration are investigated by simulating different building scenarios.

A physically based diffusion model is used to evaluate the sink effect of diffusion-controlled indoor materials and to predict the transient contaminant concentration in indoor air in response to several time-varying contaminant sources. For simplicity, it is assumed that the predominant indoor material is a homogeneous slab, initially free of contaminant, and that the air within the room is well mixed.

This paper presents the experimental results of utilizing Electro-Osmotic Pulsing Technology toreduce the diffusion of radon soil gas through a concrete slab. A laboratory system with state-of-theartinstrumentation has been used to measure the diffusion coefficient of radon soil gas through 30.5cm diameter, 10.2 cm thick standard composition concrete samples (w/c = 0.5 and cement:sand:gravel= 1:2:4). Within these concrete samples, a triple titanium anode configuration is embedded while anexternal copper rod is used as the cathode.

This paper presents the experimental results of utilizing a flexible thin-film membrane as a passivebarrier to radon gas diffusion. Nine commercially available membranes of various compositions andthicknesses were evaluated as retardant to radon gas diffusion. The radon gas concentration ratiosacross the thin-film membranes alone and in combination with an adjacent concrete sample (effectivediffusion coefficient) were measured in a laboratory system with state-of-the-art instrumentation.

Numerical modelling is a powerful tool for studies of soil gas and radon-222 entry into houses. It isthe purpose of this paper to review some main techniques and results. In the past, modelling hasfocused on Darcy flow of soil gas (driven by indoor-outdoor pressure differences) and combineddiffusive and advective transport of radon. Models of different complexity have been used. Thesimpler ones are finite-difference models with one or two spatial dimensions. The more complexmodels allow for full 3D and time dependency.

The effectiveness of various insulating materials for limiting radon entry into houses has beeninvestigated experimentally in 90 existing houses and in laboratory conditions. Each material hasbeen evaluated according to several aspects - placeability, durability, tear resistance and diffusionproperties. The results of the radon diffusion coefficients measurement in more than 80 insulatingmaterials are summarized. We have found out that great differences exist in diffusion properties,because the diffusion coefficient varries within four orders from 10-13 m2/s to 10-10 m2/s.

This study describes an approach for measuring and modeling diffusive and advective transport of radon through building materials. Goal of these measurements and model calculations is to improve our understanding concerning the factors influencing the transport of radon through building materials. To reach this goal, a number of experiments has to be conducted. These experiments, including measurements in a large cylinder for creating diffusive and advective transport of radon under controlled, dwelling-like conditions, are described here and the initial results are presented.

There is a currently growing interest in the effect of exposure to 222Rn, because it became recognised as an important “pollutant” factor of the environment. Possible lung cancer incidence due to exposure to environmental radon levels may thus account for

This paper reports experimental measurements on the diffusion of confluent jets thatform a wall jet. The experiments were carried out at a fixed air flow rate and fixed temperaturedifference between the supply and room air in the cooling mode. Based on these experiments, theresults presented show the behaviour of the wall confluent jet in the form of velocity profiles, thespreading ratio of jet on the wall, etc. The empirical equations derived are compared with othertypes of air jets, such as the free confluent jet, free plane wall jet, and free plane jet.

This paper deals with how to visibly render the thermal climate in the design and presentationtools used by different participants in the building process. The focus is on those ventilation/coolingsystems where cool air is supplied directly into the occupied zone and therefore have a potential ofgenerating a volume close to the device with poor comfort. This volume could be described as a spreading bubble. In the paper a practical procedure for rendering the spreading bubble is presented. This is achieved in a number of steps.