OF BUILDING MATERIALS FACULTY OF ENGINEERING (LTH), LUND UNIVERSITY, SWEDEN

Transcription

1 SYSTEM MODELING OF MOULD GROWTH ON BUILDING MATERIALS YUJING LI, Ph.D. DIV. OF BUILDING MATERIALS FACULTY OF ENGINEERING (LTH), LUND UNIVERSITY, SWEDEN Major challenge Modelling HOW MOULD grown on building MATERIALS

2 Fundamentals behind: How does mould grow? Material Fundamentals behind: How does mould grow Water

3 Fundalmentals behind: How does mould grow Water A Causal Loop Diagram (CLD) Water?

4 A Causal Loop Diagram (CLD) Desorption Water activity in the wood Relative humidity in the air Absorption A Causal Loop Diagram (CLD) Desorption Water activity in the wood Relative humidity in the air Absorption 4

5 A Causal Loop Diagram (CLD) Desorption Water activity in the wood Relative humidity in the air Absorption Enzyme activity Enzyme destruction Aging Modelling... Can we put ALL together? System analysis & System dynamic modelling Building Biology Group, LTH, Lund University Applied Systems Analysis & System Dynamics (ASASD) Group, Lund University 5

6 Desorption Water activity in the wood Relative humidity in the air Absorption Enzyme activity Enzyme destruction Aging 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 / % absorption desorption Relative humidity / % The sorption isotherm of wood (air dried spruce sapwood). 6

7 Desorption Water activity in the wood Relative humidity in the air Absorption Enzyme activity Enzyme destruction Aging Relative humidity and temperature, Simplified psychrometric chart for temperatures and relative humidities. Source: University of Nebraska 8, 7

8 Desorption Water activity in the wood Relative humidity in the air Absorption Enzyme activity Enzyme destruction Aging factors Fig.. The factor by relative humidity on mould activity. (Ayerst 969) Fig. 4. The temperature factor (Ayerst 969 8

9 Desorption Water activity in the wood Relative humidity in the air Absorption Enzyme activity Enzyme destruction Aging 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.) 9

10 Modelling: mould growing behaviour model of mould growth with influencing factors, STELLATM V 9. (isee systems, inc.) Some simulaiton results start with... Mould grown on wood in a closed environment Air Water

11 Results: Scenario drying Initial conditions: RH in the air: 7% Water content in wood:. : C (constant) : : : RH in air RH in wood Mould sy nthesis Mould biomass Trend 4 Active mould biomass 4 4 RH in wood : Page Hours 4 den 6 jul Time Fig. 5. The development of mould growth on wood during wood drying 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 Hours den 6 jul Untitled Time Fig. 5. The development of mould growth with moisture content changes

12 Initial conditions: Scenario wetting RH in the air: 9% Water content in wood:.6 : C (constant) : : : RH in air RH in wood Mould sy nthesis Mould biomass Trend 4 RH in wood 4 Active mould biomass : Page Hours 5 den 6 jul Time Fig. 6. The development of mould growth on wood during wood wetting Initial conditions: Scenario fluctuating temperature RH in the air: 7% Water content in the wood:. varying between C (noon time) and C (night) : 5: : 5: : RH in air RH in wood Mould sy nthesis Mould biomass 5: Temperautre Trend RH in air : 5: Page Hours 4 den jun Time Fig. 5. The development of mould synthesis with varying temperature changes

13 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 Hours 4 den jun Time Fig. 6. The development of mould biomass with varying temperature changes : Water in air Water in wood Mould biomass : Mould biomass Water in air Water in wood : : : : : Page : Hours den Page 6 jul Untitled Initial conditions: RH in the air: 7% Water content in wood:. : C (constant) Hours 4 jun den Initial conditions: RH in the air: 7% Water content in the wood:. varying between C (noon time) and C (night)

14 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 4

15 Conclusion it is called a conceptual model for the moment It is possible to combine the properties and the mould behaviour into modelling The temperature variation has significant impact on mould growth 5

16 Thank you for your attention! Fundamental reasons behind Physical parameters (temp. RH, etc.) Materials Mould on 6

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