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The Experts below are selected from a list of 2301 Experts worldwide ranked by ideXlab platform

Xudong Yang – 1st expert on this subject based on the ideXlab platform

  • a test based method for estimating the service life of adsorptive portable Air Cleaners in removing indoor formaldehyde
    Building and Environment, 2019
    Co-Authors: Mengqiang Lv, Xudong Yang

    Abstract:

    Abstract Portable Air Cleaners (PACs) with activated carbon filters are frequently used to remove gaseous contaminants. However, activated carbon has a limited adsorption capacity for small polar molecules, such as formaldehyde. Formaldehyde is a ubiquitous Air contaminant with hazardous effects to human health. Thus, characterizing carbon filter performance decay and being able to predict the service life of PACs is of high importance. This study proposes a testing method which enables the continuous measurement of the clean Air delivery rate (CADR). Vaporized formaldehyde was injected at a constant rate, i.e. 14 mg/h or 45 mg/h, into an Air-tight chamber where the PAC was operating. The CADR was calculated from the steady-state concentration in the chamber according to the mass-balance equation. An adsorptive PAC with a pleated composite filter of activated carbon and high efficiency particulate Air (HEPA) was tested until the CADR decreased to ca. 30% of its initial value. The functional relationship between the CADR and the cumulative adsorbed mass (CAM) of formaldehyde was established. Then, formaldehyde emission rates and ventilation rates in real Chinese residences were estimated by literature research. The obtained data were used in simulation to investigate PAC service life under a range of different situations. Test results showed that the CADR tended to decay exponentially with the CAM. According to the simulation, the CADR declined by 90% after a duration of 130–190 h under the most strenuous condition. However, PAC service life could be prolonged to more than 2000 h under realistic usage conditions.

  • a predictive model for the formaldehyde removal performance of sorption based portable Air Cleaners with pleated composite filter
    Building and Environment, 2019
    Co-Authors: Mengqiang Lv, Xudong Yang

    Abstract:

    Abstract Sorption-based portable Air Cleaners (PACs) are widely-used to remove gaseous contaminants. However, their capacity decline as a result of saturation cannot be well predicted through tests alone. Therefore, a predictive model to characterize the performance of a sorption-based PAC installed with a pleated composite filter is proposed in this paper. A salient merit of this proposed model is that once verified, it merely requires information regarding the adsorbent to simulate the assembled PAC. The model verification was conducted at three levels: 1) Dynamic adsorption test on the single-layer filter segment; 2) Contaminant removal test on the assembled PAC in the laboratory, which validated the extrapolation from the filter to the actual PAC unit; and 3) Field test in the research building. The third part estimated the robustness of the model in real situations. Formaldehyde was chosen as the target contaminant. Results show that the model can handle changes in significant factors including temperature, relative humidity, flow rate, and inlet concentration. It was successfully extrapolated to an assembled PAC and was able to capture the point of decline of the clean Air delivery rate (CADR) in the laboratory. Besides, the average relative errors between the tested and simulated results in the field test were under 20%, which is considered suitable for engineering applications.

  • performance of sorption based portable Air Cleaners in formaldehyde removal laboratory tests and field verification
    Building and Environment, 2018
    Co-Authors: Mengqiang Lv, Xudong Yang

    Abstract:

    Abstract Formaldehyde is one of the primary indoor Air contaminants that widely exists in construction materials and household consumable products. Acute exposure to formaldehyde causes irritation and dermal allergies, while chronic exposure can result in DNA and chromosomal damage. However, only a handful studies have evaluated formaldehyde removal capacities of portable Air Cleaners (PACs) both in the field and in the laboratory. The laboratory performance of PACs has not been statistically compared with their field performance. This study evaluated the initial formaldehyde removal capabilities of several relatively popular commercial sorption-based PACs in Chinese market by measuring their clean Air delivery rates (CADRs) in an 8 m3 environmental chamber. The modified ‘pull-down’ method was applied in this study, and the total operation time of the tested PACs was 1.5 h. The laboratory results showed wide variations in the CADRs (13.8 m3/h to 75.6 m3/h), which was in agreement with the CADRs reported in previous studies. A single-zone field test under natural ventilation was also conducted in a bedroom with an area of 25 m2 and a volume of 67.5 m3 using the best performing PAC. The results were statistically analyzed for any significant difference between the laboratory and field data. The difference between the laboratory and field performance of the tested PAC was insignificant at a confidence level of 95%.

William P Bahnfleth – 2nd expert on this subject based on the ideXlab platform

  • estimating the effects of ambient conditions on the performance of uvgi Air Cleaners
    Building and Environment, 2009
    Co-Authors: William P Bahnfleth, James D. Freihaut

    Abstract:

    Abstract Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure mercury vapor lamps to control biological Air contaminants. Ambient Air velocity and temperature have a strong effect on lamp output by influencing the lamp surface cold spot temperature. In-duct UVGI systems are particularly susceptible to ambient effects due to the range of velocity and temperature conditions they may experience. An analytical model of the effect of ambient conditions on lamp surface temperature was developed for three common lamp types in cross flow from a convective–radiative energy balance assuming constant surface temperature. For one lamp type, a single tube standard output lamp, UVC output and cold spot temperature data were obtained under typical in-duct operating conditions. Over an ambient temperature range of 10–32.2 °C and an Air velocity range of 0–3.25 m/s, measured cold spot temperature varied from 12.7 to 41.9 °C and measured lamp output varied by 68% of maximum. Surface temperatures predicted by the heat transfer model were 6–17 °C higher than corresponding measured cold spot temperatures, but were found to correlate well with cold spot temperature via a two-variable linear regression. When corrected using this relationship, the simple model predicted the cold spot temperature within 1 °C and lamp UVC output within ±5%. To illustrate its practical use, the calibrated lamp model was employed in a simulation of the control of a contaminant in a single-zone ventilation system by an in-duct UVGI device. In this example, failure to account for the impact of ambient condition effects resulted in under-prediction of average space concentration by approximately 20% relative to a constant output system operating at maximum UVC output.

  • Estimating the effects of ambient conditions on the performance of UVGI Air Cleaners
    Building and Environment, 2009
    Co-Authors: Josephine Lau, William P Bahnfleth, James D. Freihaut

    Abstract:

    Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure mercury vapor lamps to control biological Air contaminants. Ambient Air velocity and temperature have a strong effect on lamp output by influencing the lamp surface cold spot temperature. In-duct UVGI systems are particularly susceptible to ambient effects due to the range of velocity and temperature conditions they may experience. An analytical model of the effect of ambient conditions on lamp surface temperature was developed for three common lamp types in cross flow from a convective-radiative energy balance assuming constant surface temperature. For one lamp type, a single tube standard output lamp, UVC output and cold spot temperature data were obtained under typical in-duct operating conditions. Over an ambient temperature range of 10-32.2 °C and an Air velocity range of 0-3.25 m/s, measured cold spot temperature varied from 12.7 to 41.9 °C and measured lamp output varied by 68% of maximum. Surface temperatures predicted by the heat transfer model were 6-17 °C higher than corresponding measured cold spot temperatures, but were found to correlate well with cold spot temperature via a two-variable linear regression. When corrected using this relationship, the simple model predicted the cold spot temperature within 1 °C and lamp UVC output within ±5%. To illustrate its practical use, the calibrated lamp model was employed in a simulation of the control of a contaminant in a single-zone ventilation system by an in-duct UVGI device. In this example, failure to account for the impact of ambient condition effects resulted in under-prediction of average space concentration by approximately 20% relative to a constant output system operating at maximum UVC output. © 2008 Elsevier Ltd. All rights reserved.

  • estimating the effects of ambient conditions and aging on the performance of uvgi Air Cleaners
    6th International Conference on Indoor Air Quality Ventilation and Energy Conservation in Buildings: Sustainable Built Environment IAQVEC 2007, 2007
    Co-Authors: William P Bahnfleth, James D. Freihaut

    Abstract:

    Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure Hg vapor lamps to control biological Air contaminants. Lamp UV output depends on multiple factors, including accumulated operating time (age) and the thermal effects of ambient Air temperature and velocity. Additionally, the life of some lamp types depends on the frequency of on-off cycles. Models of lamp life as a function of cycling rate and lamp output as a function of age and ambient conditions are developed for three common standard output lamp types based on heat transfer theory and manufacturer’s lamp performance data. Example results are presented and a parametric study in the form of a 3 factorial experiment is used to identify significant factors affecting output and their interactions. A typical range of ambient conditions reduces lamp output by more than 30% of rated capacity and the inclusion of aging effects reduces capacity by as much as 70%. For given ambient conditions, performance varies substantially across lamp types due to their differing heat transfer characteristics. It is concluded that short term and long term variation of lamp output is highly significant and that modeling of such effects is necessary for accurate system design and analysis.

Mengqiang Lv – 3rd expert on this subject based on the ideXlab platform

  • a test based method for estimating the service life of adsorptive portable Air Cleaners in removing indoor formaldehyde
    Building and Environment, 2019
    Co-Authors: Mengqiang Lv, Xudong Yang

    Abstract:

    Abstract Portable Air Cleaners (PACs) with activated carbon filters are frequently used to remove gaseous contaminants. However, activated carbon has a limited adsorption capacity for small polar molecules, such as formaldehyde. Formaldehyde is a ubiquitous Air contaminant with hazardous effects to human health. Thus, characterizing carbon filter performance decay and being able to predict the service life of PACs is of high importance. This study proposes a testing method which enables the continuous measurement of the clean Air delivery rate (CADR). Vaporized formaldehyde was injected at a constant rate, i.e. 14 mg/h or 45 mg/h, into an Air-tight chamber where the PAC was operating. The CADR was calculated from the steady-state concentration in the chamber according to the mass-balance equation. An adsorptive PAC with a pleated composite filter of activated carbon and high efficiency particulate Air (HEPA) was tested until the CADR decreased to ca. 30% of its initial value. The functional relationship between the CADR and the cumulative adsorbed mass (CAM) of formaldehyde was established. Then, formaldehyde emission rates and ventilation rates in real Chinese residences were estimated by literature research. The obtained data were used in simulation to investigate PAC service life under a range of different situations. Test results showed that the CADR tended to decay exponentially with the CAM. According to the simulation, the CADR declined by 90% after a duration of 130–190 h under the most strenuous condition. However, PAC service life could be prolonged to more than 2000 h under realistic usage conditions.

  • a predictive model for the formaldehyde removal performance of sorption based portable Air Cleaners with pleated composite filter
    Building and Environment, 2019
    Co-Authors: Mengqiang Lv, Xudong Yang

    Abstract:

    Abstract Sorption-based portable Air Cleaners (PACs) are widely-used to remove gaseous contaminants. However, their capacity decline as a result of saturation cannot be well predicted through tests alone. Therefore, a predictive model to characterize the performance of a sorption-based PAC installed with a pleated composite filter is proposed in this paper. A salient merit of this proposed model is that once verified, it merely requires information regarding the adsorbent to simulate the assembled PAC. The model verification was conducted at three levels: 1) Dynamic adsorption test on the single-layer filter segment; 2) Contaminant removal test on the assembled PAC in the laboratory, which validated the extrapolation from the filter to the actual PAC unit; and 3) Field test in the research building. The third part estimated the robustness of the model in real situations. Formaldehyde was chosen as the target contaminant. Results show that the model can handle changes in significant factors including temperature, relative humidity, flow rate, and inlet concentration. It was successfully extrapolated to an assembled PAC and was able to capture the point of decline of the clean Air delivery rate (CADR) in the laboratory. Besides, the average relative errors between the tested and simulated results in the field test were under 20%, which is considered suitable for engineering applications.

  • performance of sorption based portable Air Cleaners in formaldehyde removal laboratory tests and field verification
    Building and Environment, 2018
    Co-Authors: Mengqiang Lv, Xudong Yang

    Abstract:

    Abstract Formaldehyde is one of the primary indoor Air contaminants that widely exists in construction materials and household consumable products. Acute exposure to formaldehyde causes irritation and dermal allergies, while chronic exposure can result in DNA and chromosomal damage. However, only a handful studies have evaluated formaldehyde removal capacities of portable Air Cleaners (PACs) both in the field and in the laboratory. The laboratory performance of PACs has not been statistically compared with their field performance. This study evaluated the initial formaldehyde removal capabilities of several relatively popular commercial sorption-based PACs in Chinese market by measuring their clean Air delivery rates (CADRs) in an 8 m3 environmental chamber. The modified ‘pull-down’ method was applied in this study, and the total operation time of the tested PACs was 1.5 h. The laboratory results showed wide variations in the CADRs (13.8 m3/h to 75.6 m3/h), which was in agreement with the CADRs reported in previous studies. A single-zone field test under natural ventilation was also conducted in a bedroom with an area of 25 m2 and a volume of 67.5 m3 using the best performing PAC. The results were statistically analyzed for any significant difference between the laboratory and field data. The difference between the laboratory and field performance of the tested PAC was insignificant at a confidence level of 95%.