46 SYSTEM MODELING OF MOULD GROWTH ON BUILDING MATERIALS YUJING LI, Ph.D. DIV. OF BUILDING MATERIALS FACULTY OF ENGINEERING (LTH), LUND UNIVERSITY, SWEDEN MARCH 5 TH 4, GÖTEBORG Challenge... varje har en kritisk fuktnivå som inte får överskridas och om den inte kan redovisas så får ets relativa fuktighet inte överstiga 75 %... BBR (Boverket)
46 Questions Only critical level matters? RH RH & temperature Exposure time How long? Constant level vs. Changing conditions Long term prediction? Practical tool? Previous models What s missing The mechanism of the growth The mechanism of the decaying Other factors, e.g., the oxygen level etc. The connections between the biology and the Etc.
46 Major challenge Modelling HOW MOULD grown on building MATERIALS Fundamentals behind: How does mould grow? Material
46 Fundamentals behind: How does mould grow Water Organic compounds in the Fundalmentals behind: How does mould grow Water Oxygen available Organic compounds in the 4
46 A Causal Loop Diagram (CLD) Water? Oxygen available Organic compounds in the A Causal Loop Diagram (CLD) Desorption Water activity in the Relative humidity in the air Absorption Oxygen available Organic compounds in the 5
46 A Causal Loop Diagram (CLD) Desorption Water activity in the Relative humidity in the air Absorption Oxygen available Organic compounds in the A Causal Loop Diagram (CLD) Desorption Water activity in the Relative humidity in the air Absorption Enzyme activity Enzyme destruction Oxygen available Organic compounds in the Aging 6
46 Modelling... Can we put ALL together? System analysis & System dynamic modelling Building Biology Group, LTH, Lund University www.byggnads.lth.se Applied Systems Analysis & System Dynamics (ASASD) Group, Lund University www.lth.se/asasd Desorption Water activity in the Relative humidity in the air Absorption Enzyme activity Enzyme destruction Oxygen available Organic compounds in the Aging 7
46 Materal s moisture simulation Desorption and Adsorption,,, m wv,s : water vapour mass flow rate (kg/ms) h D : diffusion coefficient R: gas constant T: temperature P wv,w : water vapour pressure of the wood P wv,a : water vapour pressure in the air Moisture content / % 5 5 5 absorption desorption 4 5 6 7 8 9 Relative humidity / % The sorption isotherm of wood (air dried spruce sapwood). Desorption Water activity in the Relative humidity in the air Absorption Enzyme activity Enzyme destruction Oxygen available Organic compounds in the Aging 8
46 Relative humidity and temperature,.7.46 6... Simplified psychrometric chart for temperatures and relative humidities. Source: University of Nebraska 8, http://www.ianrpubs.unl.edu/pages/publicationd.jsp?publicationid= Desorption Water activity in the Relative humidity in the air Absorption Enzyme activity Enzyme destruction Oxygen available Organic compounds in the Aging 9
46 factors Fig.. The factor by relative humidity on mould activity. (Ayerst 969) Fig. 4. The temperature factor (Ayerst 969 Desorption Water activity in the Relative humidity in the air Absorption Enzyme activity Enzyme destruction Oxygen available Organic compounds in the Aging
46 Modelling: moisture properties RH difference water dif fuse in Wood coeff icient diffuse coefficient Temperautre Water in wood Dif f usion in to wood Water in air Diff use in out Water in Water out water consumed Diff usion out Initial water Mass of wood WC in wood RH in wood Wood dif fuse coeff icient RH dif ference water v apour content v olume of air RH in air Ambient oxygen lev el Saturated water v apour content Temperautre Air Pressure Saturated Water v apour pressure model of water vapour exchange between wood and air, STELLATM V 9. (isee systems, inc.) Modelling: mould growing behaviour model of mould growth with influencing factors, STELLATM V 9. (isee systems, inc.)
46 Some simulaiton results start with... Mould grown on wood in a closed environment Air Water Results: Scenario drying Initial conditions: RH in the air: 7% Water content in wood:. : C (constant) : 4: : 4: : RH in air RH in wood Mould sy nthesis 4: Mould biomass Trend 4 Active mould biomass 4 4 RH in wood : 4: Page 4. 6.. 8. 4. Hours 4 den 6 jul Time Fig. 5. The development of mould growth on wood during wood drying
46 Results: Scenario drying Initial conditions: RH in the air: 7% Water content in wood:. : C (constant) : : : Water in air Water in wood Mould biomass Trend Water in air Active mould biomass Water in wood : Page. 6.. 8. 4. Hours den 6 jul Untitled Time Fig. 5. The development of mould growth with moisture content changes Initial conditions: Scenario wetting RH in the air: 9% Water content in wood:.6 : C (constant) : 4: : 4: : RH in air RH in wood Mould sy nthesis 4: Mould biomass Trend 4 RH in wood 4 Active mould biomass : 4 4 4:. 6.. 8. 4. Page Hours 5 den 6 jul Time Fig. 6. The development of mould growth on wood during wood wetting
46 Initial conditions: Scenario fluctuating temperature RH in the air: 7% Water content in the wood:. varying between C (noon time) and C (night) : 4: 5: : 4: 5: : RH in air RH in wood Mould sy nthesis 4: Mould biomass 5: Temperautre Trend 5 RH in air 5 5 5 : 4: 5: Page 4 4 4 4 5. 8. 6. 54. 7. Hours 4 den jun Time Fig. 5. The development of mould synthesis with varying temperature changes Scenario fluctuating temperature Initial conditions: RH in the air: 7% Water content in the wood:. varying between C (noon time) and C (night) : : : Mould biomass Water in air Water in wood Trend Active mould biomass : Page. 6.. 8. 4. Hours 4 den jun Time Fig. 6. The development of mould biomass with varying temperature changes 4
46 : Water in air Water in wood Mould biomass : Mould biomass Water in air Water in wood : : : : : Page :. 6.. 8. 4. Hours den Page 6 jul Initial conditions: Untitled RH in the air: 7% Water content in wood:. : C (constant). 6.. 8. 4. Hours 4 jun den Initial conditions: RH in the air: 7% Water content in the wood:. varying between C (noon time) and C (night) Initial conditions: RH in the air: 65% Water content in the wood:.6 varying between C (noon time) and C (night) Scenario 4 longer period 5
46 month Longer period 6 month 6
46 Even longer ~ month Starting with: RH in the air: 65% ºC Water content in the wood:.6 fluctuating daily ºC ºC months 6 months months 7
46 Conclusion The temperature variation has significant impact on mould growth on s it is called a conceptual model for the moment It is possible to combine the properties and the mould behaviour into modelling A new MModel project (Comparing to Johansson et. al. ) 8
46 The work flow of the new Mmodel Modelling Model validation Practical tool Data collection Building physics & climate data Long term prediction Acknowledgement 9
46 Thank you for your attention! Fundamental reasons behind Physical parameters (temp. RH, etc.) Materials Mould on
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