Progress 09/01/04 to 08/31/08
Outputs
OUTPUTS: OUTPUTS: Our Computational Fluid Dynamics (CFD) models developed during the 2005-2006 period, was utilized to evaluate the effect of multi-year weather conditions (1996 - 2006) on the half-loss time (HLT) and concentrationtime (Ct) product, concluding that past fumigation data should not be the primary means for quantifying the effectiveness of temporary structural sealing. In follow up study, using the same CFD model the standardized building pressurization test and superposition method commonly used for heating/cooling load and in-door air quality calculations in buildings were evaluated for prediction of HLT and Ct product. A simulated pressurization test was performed in order to determine the flour mill's effective leakage area. Then, the simulated mill was subjected to several fixed environmental conditions to determine the stack and wind coefficients which were necessary for the superposition calculation. The HLTs and Ct products generated by the 11-year fumigation simulations were compared with the corresponding values predicted based on the superposition method. The HLT and Ct product predictions were within 20 and 10% of the simulated values, respectively, except for one simulated fumigation. These results showed that the pressurization test and superposition method have potential application benefits for optimizing the structural fumigation process. PARTICIPANTS: Purdue Staff: Dirk E. Maier, PI & PD, Professor of Ag & Bio Engineering; Klein E. Ileleji, Co-PI, Assistant Professor of Ag & Bio Engineering; Jayathi Murthy, Co-PI, Professor of Mechanical Engineering; Linda J. Mason, Co-PI, Associate Professor of Entomology; Wat Chayaprasert, PhD Student, Ag & Bio Engineering; Wan-Tien Tsai, MS/PhD Student, Entomology; Vaidehi Ambatipudi, MS Student, Mechanical Engineering; Partner Organizations: Fumigation Service & Supply, Westfield, IN; Dow AgroSciences, Indianapolis, IN; Several commercial flour mills; TARGET AUDIENCES: Results of this research were presented at several national and international conferences (2006 International Working Conference on Stored Product Protection, Campinas, Brazil; 2005, 2006, 2007 Methyl Bromide Alternatives Conference; 2005, 2006 Annual Meeting of the Entomology Society of America; 2005, 2006, 2007 International Meeting of the American Society of Agricultural & Biological Engineers; 2008 International Grain Quality & Technology Congress, Chicago, USA; 2008 Controlled Atmosphere & Fumigation Conference, Chengdu, China) and industry conferences (2007 Fumigants & Pheromones Conference, Bremen, Germany; 2007 Regional Meeting of the International Association of Operative Millers) attended by researchers, government regulators, and representatives of the U.S. flour milling and food processing industry as well as the pest control industry. PROJECT MODIFICATIONS: The primary change in approach for this project is the development of an automated fumigation monitoring and DECISION SUPPORT system instead of an automated monitoring and CONTROL system. Reason for this change is that the stewardship protocol for sulfuryl fluoride currently requires manual release of the gas from cylinders rather than automatic release. We were not aware of this limitation when we initiated this project. However, the decision support software advises the fumigator as to when to release gas and how much. The system is set up so that an automated option could easily be incorporated in the future. An additional change to the project was that it was not possible to conduct a structural fumigation with ECO2Fume (98% CO2 with 2% Phosphine) as was originally proposed. After the project had been initiated, the commercial collaborator decided to only conduct SF fumigations. On the other hand, when the project was proposed we did not expect that we would be able to monitor any methyl bromide fumigations. Fortunately, we were able to do so and thus could compare SF versus MeBr fumigations in the same structures.
Impacts
Viable alternatives such as heat treatment, ECO2Fume (98% CO2 with 2% phosphine), Profume (Sulfuryl fluoride) and a combination of heat treatment, CO2 and ECO2Fume have proven to be effective for structural fumigation of flour mills, food processing plants and food warehouses when lethal concentrations and temperatures are held for exposure periods that will achieve over 95% mortality. Unlike methyl bromide (MeBr) which is a faster acting fumigant, most of the alternatives require higher concentrations and longer periods of exposure to be effective. Thus, the key for successful adoption of alternative measures lies in the optimization of their application during fumigation. Even though it is generally known that the success of a fumigation is affected by a multitude of structural, environmental, and fumigation methods, previous to this study there was no data in the literature or used by industry that accurately described the relationship of these factors and the dosage application rate. Because it is not practical to perfectly seal the structure, the fumigation process can be better optimized only if the dynamics of gas movement in the fumigated space and the effects of environmental conditions on the fumigation process are well understood. Our project effort developed a Structural Fumigation and Analysis Tool (SFAT-CFD) for promising MeBr alternatives (e.g., sulfuryl fluoride [SO2F2]) for the structural fumigation of flour mills, food processing plants, and food warehouses. We also developed a fumigation monitoring and decision support system that can automatically monitor a fumigation with any gas and provide expert advice to the fumigator. Additionally, we determined that no measurable differences exist between MeBr and SO2F2 gas movement in these structures, and that pressure testing of the structure pre-fumigation can be used to predict the half-loss time (HLT) of the fumigation. As a result of our efforts, all project objectives were successfully accomplished.
Publications
- Watcharapol Chayaprasert, Dirk E. Maier, Klein E. Ileleji and Jayathi Y. Murthy. 2008. Effects of weather conditions on sulfuryl fluoride and methyl bromide leakage during structural fumigation in a flour mil. Journal of Stored Products Research. 44(x):1-9. Available on-line October 8, 2008.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: Using our Computational Fluid Dynamics (CFD) models developed during the 2005-2006 period, eleven fumigation simulations were performed using historical weather data of the same time period between 1996 and 2006 to evaluate the effect of multi-year weather conditions on the gas leakage rate (i.e., HLT) and the concentration x time (Ct) product during structural fumigation. The simulation results suggested that prediction of fumigation performance should incorporate quantifiable sealing effectiveness which can be achieved by the building pressurization test. With this testing method, the tested structure is pressurized at different constant pressure levels using a specially calibrated fan. At each pressure level, the air flow rate that passes through the pressurization fan is measured. The pressure-flow rate measurements provide the leakage characteristic of the structure. In order to thoroughly disinfest the fumigated structure of insect pests, the target Ct product must be
reached throughout the structure. Thus, a second simulation study was conducted to quantitatively evaluate the effectiveness of circulation fans on gas distribution during structural fumigation and provide guideline recommendations for configuring circulation fan systems (e.g., number of fans, fan locations and orientations, and flow capacity). General guideline recommendations for configuring circulation fan systems were (1) one circulation fan should be placed in each separate fumigation volume, (2) fumigant introduction locations should be as close to the middle area of the fumigated space as possible, and (3) circulation fans should be oriented in the direction in which there are no obstacles in their flow paths. Bioassay mortality data and insect population dynamic monitoring data were also collected to compare SF and MB fumigations' efficacy in flour mills. Current bioassay results indicate 100% mortality of larval and adult stages of both species for both fumigants. More than
99% of red flour beetle and 100% of Indianmeal moth pupae died when exposed to either fumigant. The majority of red flour beetle larvae from treated eggs died before the adult stage (95.36% SF and 99.67% MB) as well as Indianmeal moth eggs (96.56% SF and 99.67% MB). Insect populations were usually significantly lower right after fumigation but could increase to pre-population level within 2-8 weeks depending on the facility. A sanitation scale was also developed to evaluate mills and their sanitation practices. Sanitation audits have been done in 50% of the mills. These three major biological aspect approaches will help to develop better integrated pest management programs in food processing facilities.
PARTICIPANTS: Purdue Staff: Dirk E. Maier, PI & PD, Professor of Ag & Bio Engineering; Klein E. Ileleji, Co-PI, Assistant Professor of Ag & Bio Engineering; Jayathi Murthy, Co-PI, Professor of Mechanical Engineering; Linda J. Mason, Co-PI, Associate Professor of Entomology; Wat Chayaprasert, PhD Student, Ag & Bio Engineering; Wan-Tien Tsai, MS/PhD Student, Entomology; Vaidehi Ambatipudi, MS Student, Mechanical Engineering; Partner Organizations: Fumigation Service & Supply, Westfield, IN; Dow AgroSciences, Indianapolis, IN; Several commercial flour mills;
TARGET AUDIENCES: Results of this research were presented at several national and international conferences (2006 International Working Conference on Stored Product Protection, Campinas, Brazil; 2005, 2006, 2007 Methyl Bromide Alternatives Conference; 2005, 2006 Annual Meeting of the Entomology Society of America; 2005, 2006, 2007 International Meeting of the American Society of Agricultural & Biological Engineers) and industry conferences (2007 Fumigants & Pheromones Conference, Bremen, Germany; 2007 Regional Meeting of the International Association of Operative Millers) attended by researchers, government regulators, and representatives of the U.S. flour milling and food processing industry as well as the pest control industry.
PROJECT MODIFICATIONS: The primary change in approach for this project is the development of an automated fumigation monitoring and DECISION SUPPORT system instead of an automated monitoring and CONTROL system. Reason for this change is that the stewardship protocol for sulfuryl fluoride currently requires manual release of the gas from cylinders rather than automatic release. We were not aware of this limitation when we initiated this project. However, the decision support software advises the fumigator as to when to release gas and how much. The system is set up so that an automated option could easily be incorporated in the future.
Impacts
Viable alternatives such as heat treatment, ECO2Fume (98% CO2 with 2% phosphine), Profume (Sulfuryl fluoride) and a combination of heat treatment, CO2 and ECO2Fume have proven to be effective for structural fumigation of flour mills, food processing plants and food warehouses when lethal concentrations and temperatures are held for exposure periods that will achieve over 95% mortality. Unlike methyl bromide (MeBr) which is a faster acting fumigant, most of the alternatives require higher concentrations and longer periods of exposure to be effective. Thus, the key for successful adoption of alternative measures lies in the optimization of their application during fumigation. Even though it is generally known that the success of a fumigation is affected by a multitude of structural, environmental, and fumigation methods, there is no data in the literature or used by industry that accurately describes the relationship of these factors and the dosage application rate.
Because it is not practical to perfectly seal the structure, the fumigation process can be better optimized only if the dynamics of gas movement in the fumigated space and the effects of environmental conditions on the fumigation process are well understood. Our long-term goal is to develop a Structural Fumigation and Analysis Tool (SFAT-CFD) for promising MeBr alternatives (e.g., sulfuryl fluoride [SO2F2]) for the structural fumigation of flour mills, food processing plants, and food warehouses. We will also develop a fumigation monitoring and decision support system that can automatically monitor the fumigation and provide expert advice to the fumigator. Additionally, we will determine whether measurable differences exist between MeBr and SO2F2 gas movement in these structures.
Publications
- Watcharapol Chayaprasert, Dirk E. Maier, Klein E. Ileleji and Jayathi Y. Murthy. 2008. Development and validation of Computational Fluid Dynamics models for precision structural fumigation. Journal of Stored Products Research. 44(1):11-20.
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Progress 10/01/05 to 09/30/06
Outputs
Computer simulations of the structural fumigation process in a flour mill were conducted using Fluent, a commercial Computational Fluid Dynamics (CFD) solver, to capture the effect of wind velocity on the fumigant leakage rate which was expressed in terms of half-loss time (HLT) values based on one set of fumigation data. That data was collected during the fumigation of a commercial flour mill during the summer of 2005. Two flow models, one for the flow outside the structure and one for the flow inside the structure, were constructed. The information from the pressure profile on the external wall from the external flow model was used for estimating the boundary conditions for the internal flow model. Since it was not possible to obtain the actual number and size of the unsealed cracks by any kind of measurement, an idea for representing the cracks as an effective leakage zone (ELZ) was adopted. The HLT of the building estimated from the raw data was 10 hours. The
models were able to predict this HLT value. The methodology of model building established in this paper will serve as the basis for the development of a structural fumigation control process.
Impacts
Viable alternatives such as heat treatment, ECO2Fume (98% CO2 with 2% phosphine), Profume (Sulfuryl fluoride) and a combination of heat treatment, CO2 and ECO2Fume have proven to be effective for structural fumigation of flour mills, food processing plants and food warehouses when lethal concentrations and temperatures are held for exposure periods that will achieve over 95% mortality. Unlike methyl bromide (MeBr) which is a faster acting fumigant, most of the alternatives require higher concentrations and longer periods of exposure to be effective. Thus, the key for successful adoption of alternative measures lies in the optimization of their application during fumigation. Our long-term goal is to develop a Structural Fumigation and Analysis Tool (SFAT-CFD) for two promising MeBr alternatives (ProFume [SO2F2] and ECO2Fume [[PH3] + CO2 + Heat combination) for the structural fumigation of flour mills, food processing plants and food warehouses. We will also develop a
precision fumigation system (FUMITROL control system) that can automatically monitor and control gas dosage. Additionally, we will determine whether measurable differences exist between MeBr and SO2F2 gas movement in these structures.
Publications
- No publications reported this period
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Progress 10/01/04 to 09/30/05
Outputs
Two sulfuryl-fluoride fumigations were performed at commercial flour mills during the summer of 2004. Several measurements were taken in order to use these data to validate our new structural fumigation computer models. The models simulate the effects of the prevailing environmental conditions as well as account for the leakage rate of the fumigant. Leakage rate is a function of the pressure drop across the building envelope. The three major mechanisms that create pressure differences across building walls are the stack effect caused by temperature differences, the natural wind impinging on the building, and the mechanical ventilation system. One of the findings from this fumigation was that the addition of the gas fumigant into the sealed buildings and the operation of circulation fans did not affect the hydrostatic pressure inside of the building. Therefore, it does not appear that the fumigant addition and circulation fan operation contribute to the loss of
fumigant concentration. Given that one of the facilities was a relatively new and air-tight structure, we do not expect to observe a pressure buildup due to the fumigant addition in any other structure. The data showed that the temperature of the air inside the building was always greater than that of the outside environment, which created density differences. Based on our initial analysis, the hydrostatic pressure in the lower portion of the building was lower than the environmental barometric pressure and the opposite occurred in the upper portion of the building. Therefore, in the absence of other driving forces the outside air will enter the building in the lower portion and the mixture of air and fumigant will flow out of the building in the upper portion. This also generates an updraft current of the mixture moving from the bottom floor to the top floor which to some extent assists the mixing of the air and fumigant. Additionally, the initially observed variation in the
concentration readings on different floors vanished within two hours of start up even though the circulation fans on these floors were not operating. The distribution of the gas on these was attributed to the stack effect. The wind effect on this particular fumigation seemed to be substantial (up to 4 m/s or 9 mph). Natural wind creates a distribution of static pressures on the building exterior surface which depends mainly on the direction of the wind and the shape and orientation of the building. We are currently in the process of analyzing the data collected with a computational fluid dynamics tool. It consists of an external flow model that can be used to generate the static pressure profile based on the wind data collected and the net pressure difference across the building envelope can be determined by superposition of the wind and stack effects.
Impacts
Viable alternatives such as heat treatment, ECO2Fume (98% CO2 with 2% phosphine), Profume (Sulfuryl fluoride) and a combination of heat treatment, CO2 and ECO2Fume have proven to be effective for structural fumigation of flour mills, food processing plants and food warehouses when lethal concentrations and temperatures are held for exposure periods that will achieve over 95% mortality. Unlike methyl bromide (MeBr) which is a faster acting fumigant, most of the alternatives require higher concentrations and longer periods of exposure to be effective. Thus, the key for successful adoption of alternative measures lies in the optimization of their application during fumigation. Our long-term goal is to develop a Structural Fumigation and Analysis Tool (SFAT-CFD) for two promising MeBr alternatives (ProFume [SO2F2] and ECO2Fume [[PH3] + CO2 + Heat combination) for the structural fumigation of flour mills, food processing plants and food warehouses. We will also develop a
precision fumigation system (FUMITROL control system) that can automatically monitor and control gas dosage.
Publications
- No publications reported this period
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