Low Emissivity Materials Research Articles

Modelling of Emissions of Total Volatile Organic Compounds in an Australian House

A simplified indoor air quality (IAQ) model has been applied to predict IAQ in an Australian house, using environmental chamber measurements of source strengths, house ventilation and room size. Total volatile organic compounds (TVOCs) was used as the model pollutant in this study. The validity of the IAQ model was initially assessed by comparing model predictions with measurements in the house over a period of time. The root mean square error between the measured and predicted values was 0.039. This model explains 57% of the potential for error. The TVOC concentrations measured in the conventional house ranged from 60 to 162 µg·m^–3. These values are much lower than some published values (0.48–31.7 mg·m^–3) for new houses in Scandinavian countries and in the USA. The low TVOC concentrations obtained in this study probably result from the high ventilation rates in this conventional house and the use of low TVOC emission materials.

Characterization of total volatile organic compound emissions from paints

Recently, Homeswest in Western Australia and Murdoch University developed a project to construct low allergen houses (LAH) in a newly developed suburb. All potential volatile organic compound (VOC) emission materials used in LAH are required to be measured before the construction of LAH, to ensure they are low VOCs emission materials. To protect people sensitive to exposure to VOCs it is important to evaluate and select low VOCs emitting paints. In this paper, therefore, twelve different paints provided by local manufacturers were selected for analysis to characterize total volatile organic compounds (TVOC) emissions. Emissions of TVOCs from six organic solvent-soluble paints and six water-soluble paints were evaluated using a small test chamber under controlled temperature, relative humidity and air exchange rates. The major volatile organic compounds in these paints were also identified. The time dependence of TVOC emissions from paint products in the chamber was evaluated. TVOC emissions from organic solvent-soluble and water-soluble paints were compared. The influence of air exchange rate on the TVOC concentrations emitted from organic solvent-soluble and water-soluble paints was also investigated. A double-exponential equation was used to evaluate emission characteristics of TVOC from paint products. With this double-exponential model, the physical processes of TVOC emissions can be explained. A variety of emission parameters can be calculated and used to estimate real indoor TVOCs concentrations.

Modelling of Emissions of Total Volatile Organic Compounds in an Australian House

A simplified indoor air quality (IAQ) model has been applied to predict IAQ in an Australian house, using envi ronmental chamber measurements of source strengths, house ventilation and room size. Total volatile organic compounds (TVOCS) was used as the model pollutant in this study. The validity of the IAQ model was initially assessed by comparing model predictions with mea surements in the house over a period of time. The root mean square error between the measured and predicted values was 0.039. This model explains 57% of the poten tial for error. The TVOC concentrations measured in the conventional house ranged from 60 to 162 μg.m-3 . These values are much lower than some published val ues (0.48-31.7 mg.m-3) for new houses in Scandinavian countries and in the USA. The low TVOC concentrations obtained in this study probably result from the high ven tilation rates in this conventional house and the use of low TVOC emission materials.

Strip speed measurement using distributed infra-red detectors

A non-contact method for measuring the speed of electrically conducting strip over the range of speeds found in industry is described. The method is thermal in character and relies on the ability of the strip to store heat for short periods of time. A wavelength-sensitive reading head consisting of an array of equally spaced infra-red detector s senses the heat pattern present on the moving strip. The signals from the array elements are combined and the array acts as a spatial filter. The resultant signal is then fed back to a heater, or writing head, placed upstream of the reading head, resulting in a closed loop time-delay feedback system which oscillates at a frequency proportional to the strip speed. Phase shifts within the feedback loop cause a departure from linearity in the speed/frequency relationship. This effect is minimised by a digital feedback loop which performs phase correction. The method has been implemented using inexpensive pyroelectric detectors, an accuracy of 0.4% being obtained with strip of adequate emissivity. Use of high-performance detectors would enhance performance, particularly for low emissivity material.

Emission of organic substances from indoor surface materials

A wide variety of surface materials in buildings can release organic compounds. Examples include building materials, furnishings, maintenance materials, clothing, and paper products. These sources contribute substantially to the hundreds of organic compounds that have been measured in indoor air. Their emissions have been directly connected to complaints of odors or hyperreactivity and are presumed to contribute to the problems in many ‘sick buildings’ where the cause complaints is uncertain. Significant progress has been made in the past decade in developing procedures for measuring emissions from such materials, in controlled experiments where factors affecting emission rates can be determined and quantified. Emissions data are still limited but are being accumulated gradually by research groups in Europe and North America. It is clear from the recent data gathered in research and modeling studies that one of the most effective ways to limit indoor concentrations of organic compounds is to limit the content of volatile compounds in materials that are used in buildings. Limiting the original residual content of volatile compounds in the materials, or conditioning such materials prior to use in buildings, or (perhaps) conditioning such materials in place before occupancy of a new or renovated building, are most likely to prevent excessive indoor concentrations. If emissions testing and product certification procedures are available and there is sufficient market demand for low-emitting materials caused by indoor air quality concerns, significant reductions of indoor concentrations of vapor-phase organic compounds could be achieved within the next decade.

Heat Conservation System for Arc Lamps

In order to have high efficiency in a metal arc discharge, the metal vapor pressure has to reach an optimum value, and this requires a minimum wall temperature. Therefore, if one can effectively use the thermal energy for heating purposes, the efficiency of the lamp can be improved. In this paper the author will discuss the effectiveness of selecting a low emissivity material for the arc tube, and reducing the effective emissivity of arc tubes by using transparent heat shields to conserve heat. Simplified formulas for the wall temperature calculations with such heat conservation systems are included.

Application of hemispherical surface pyrometers to the measurement of the emissivity of platinum (a low-emissivity material)

The total hemispherical emissivity epsilonht of platinum in the temperature range 300-1200°C has been determined by a technique based on the Land hemispherical surface pyrometer. It is shown that epsilonht of a low-emissivity material and its dependence on temperature can be measured conveniently, rapidly and precisely by this technique. The spectral hemispherical emissivity of platinum at 0.9 μm has been measured in the temperature range 900-1200°C.