Is there a curve on SAT

 

8.1 Condensation in the component cross-section

8.1.1 Calculation of the amount of condensation water and the Evaporation rate

In the following, the calculation method for determining the amount of condensate mW, T and the amount of evaporation mW, V specified in the event that condensation occurs in one layer within a component. The calculation is based on a balancing of mass flows. It is a semi-graphic process (Glaser process).

 

a) thaw period

1. Temperatures Jj calculate in the layer boundaries

2. Water vapor saturation pressures psat determine in the layer boundaries

3. Calculate water vapor partial pressures on the surfaces

in Pa

in Pa

4. Air layer thicknesses equivalent to water vapor diffusion sd of the individual layers

5. Water vapor saturation curve psat over the water vapor diffusion equivalent air layer thickness sd Instruct

6. Construct the curve of the water vapor partial pressure. For this purpose, the shortest connection between the partial vapor pressures at the surfaces is pvi and pve to be constructed, whereby the saturation line must not be exceeded. The linear connection of the partial vapor pressures at the surfaces intersects the psatCurve, condensation will form in the component.

7. Calculation of the amount of condensate mW, T

in kg / m²s

in kg / m²s

in kg / m²

 

b) evaporation period

1. Temperatures Jj determine in the layer boundaries

2. Water vapor saturation pressures psat determine in the layer boundaries

3. Calculate water vapor partial pressures on the surfaces

in Pa

in Pa

4. Air layer thicknesses equivalent to water vapor diffusion see chapd of the individual layers

5. Water vapor saturation curve psat Apply over the water vapor diffusion equivalent air layer thickness sd

6. Construct the curve of the water vapor partial pressure. For this purpose, the saturation pressure psat, w in the plane in which condensation took place during the thawing period, with the partial vapor pressures on the surfaces pvi and pve connected in a straight line. *12)

7. Calculation of the amount of evaporation mW, V

in kg / m²s

in kg / m²s

in kg / m²

 

Special case: evaporation period on the roof

When investigating the amount of evaporation mW, V A roof surface temperature of 20 ° C must be used as a basis for roof ceilings. This creates, contrary to the boundary conditions for other external components, a temperature gradient from the outside to the inside.

 

 

 

1 roof skin

2) thermal insulation

3) vapor barrier

4) reinforced concrete

 
 

 

 

in kg / m²s

in kg / m²s

in kg / m²

 

c) Compilation of the various cases for the Glaser process

The calculation formulas for other cases are given in the following table. The formulas are derived in an analogous manner.

Table 8: Compilation of the different cases for the Glaser process

 

Thaw period

Evaporation period

The water vapor partial pressure pD. in the component is lower than the possible water vapor saturation pressure at every point. Therefore falls in the component no Condensation on.

 
(To the table overview)

 

 

Thaw period

Evaporation period

Condensation occurs on the level between layers 1 and 2:

Amount of condensate mW, T

 

Evaporation rate mW, V

(To the table overview)

 

Thaw period

Evaporation period

Condensation occurs in two levels of the component, between layers 1 and 2 and between layers 3 and 4:

Amount of condensation water mW, T

mW, T = mW, T1 + mW, T2

 

 

Evaporation rate mW, V

(To the table overview)

 

Thaw period

Evaporation period

Condensation occurs in one layer of the component between the levels in layer 2:

Amount of condensate mW, T

 

Evaporation rate mW, V

(To the table overview)

d) Calculation of the partial vapor pressure in the separating layers

For the computational recording, the partial vapor pressure in the individual separating layers can be calculated under steady-state conditions, comparable to the determination of the temperature in the separating layers. *13)

 

 

8.1.2 Standard conditions for calculating the amount of condensation water and the amount of evaporation

 

In DIN 4108, T 2, climatic boundary conditions are specified that enable the calculation of the amount of condensation water mW, T and the amount of evaporation mW, V are to be taken as a basis. In less favorable climatic conditions (e.g. swimming pools, cold stores, etc.), the actual room climate and the outside climate at the location must be used. To simplify matters, the climatic conditions for wall components can also be used as a basis for roofs.

The following conditions apply to the thaw period

J gi= 20 ° Cj gi = 0.5 (50% r.h.)
J ge= -10 ° Cj ge = 0.8 (80% r.h.)

t T = 5,184*106s (1440 h / 60 days)

t T = Duration of the thaw period

The following applies to the evaporation period

a) Wall components and ceilings under undeveloped attic spaces:

J Li = 12 ° C

j gi = 0.7 (70% r.h.)
j ge = 0.7 (70% r.h.)

Climate in the condensation area:

J = 12 ° Cj = 1.0 (100% r.h.)

t V. = 7,776*106s (2160 h / 90 days)

t V. = Duration of the evaporation period

 

b) Roofs that close off common rooms from the outside air:

J gi = 12 ° Cj gi = 0.7 (70% r.h.)
J ge = 12 ° Cj ge = 0.7 (70% r.h.)

J s, DA = 20 ° C (roof surface)

Climate in the condensation area:

J according to the temperature gradient from the inside to the outside

j = 1.0 (100% r.h.)

t V. = 7,776*106s (2160 h / 90 days)

t V. = Duration of the evaporation period

 

Renewed condensation during the evaporation period is not taken into account according to DIN 4108.

 

8.1.3 Requirements for moisture protection according to

DIN 4108

According to DIN 4108, components requiring proof must meet the following requirements for condensation protection:

1. The amount of condensation water that occurs during the thawing period mW, T must not be greater than the amount of evaporation mW, V be.

2. The following must apply to roof and wall constructions:

3. The following must apply to the contact surfaces of layers that are not water-absorbent by capillary action, e.g. contact surfaces of fiber insulation materials or air layers on the one hand and vapor barriers or concrete layers on the other hand: *15)

4. The building materials that come into contact with the condensation water must not be damaged (e.g. by corrosion, fungal attack).

5. The following increases in the mass-related moisture content are not permitted:

Wood

by more than 5%

 

a) exterior walls

Table 9: External walls for which no proof is required

Wall type

 

Masonry

single-shell according to DIN 1053, plastered on both sides

double-shell according to DIN 1053, with and without thermal insulation

single-shell, external insulation layer and external plaster or ventilated cladding

single-shell, interior insulation and interior plaster ()

concrete

Aerated concrete, reinforced ()

Lightweight concrete without thermal insulation, plastered on both sides

Normal concrete or lightweight concrete with external thermal insulation and external plaster without rear-ventilated cladding

Wood panel construction

Thermal insulation in the compartment, vapor barriers on the inside
(), external planking made of wood or wood-based materials
() and ventilated weather protection

(To the table overview)

 

8.2 Formation of condensation on the surface of components

 

Conditions can be set under which condensation can be avoided.
Condition for freedom from condensation on the room-side component surface:

 

Boundary conditions according to DIN 4108 "Thermal insulation in building construction":

Jge = -15 ° Cje = 0.8 (80% r.h.)
Jgi = 20 ° Cji = 0.5 (50% r.h.)

 

Unless special conditions, e.g. in the case of severely hindered heat transfer due to furniture or a geometric thermal bridge (e.g. room corner, connection points between two components), the choice of a larger internal heat transfer resistance Rsi according to DIN 4108:

 


 

 

The level in which condensation has accumulated during the thawing period is saturated (j = 100%)
It should be noted that is.
Capillary water-absorbing layers and thus capillary moisture transport are required.
To limit run-off and dripping.
e.g. chipboard etc.
In the following, the following notation is chosen for the water vapor partial pressure of the room air: psi= pi