Physical analysis#
import fesslix as flx
flx.load_engine()
Random Number Generator: MT19937 - initialized with rand()=1028149038;
Random Number Generator: MT19937 - initialized with 1000 initial calls.
0
Todo
Write this section.
dew point and humidity#
saturation vapor pressure from temperature#
- flx.phys_temp2svp()#
- Syntax:
flx.phys_temp2svp(temp)- Description:
Evaluates the saturation vapor pressure as a function of temperature temp.
Example:
For a temperature of 22°C, the saturation vapor pressure is:
print(f"{flx.phys_temp2svp(22.):.2f} hPa")
26.37 hPa
vapor pressure#
Vapor pressure is evaluated by multiplying the saturation vapor pressure with the relative humidity. Note that vapor pressure is the primary conserved variable in steady-state building physics.
Example:
For a temperature of 22°C and 40% humidity, the vapor pressure is:
vp = 0.4 * flx.phys_temp2svp(22.)
print(f"{vp:.2f} hPa")
10.55 hPa
dew point from temperature and relative humidity#
- flx.phys_dewpoint()#
- Syntax:
flx.phys_dewpoint(temp, phi)- Description:
Evaluates the dew point as a function of temperature temp and humidity phi.
Example:
For a temperature of 22°C and 40% humidity, the dew point is:
dew_point = flx.phys_dewpoint(22.,0.4 )
print(f"{dew_point:.1f} °C")
7.8 °C
temperature from dew point and relative humidity#
- flx.phys_tauphi2temp()#
- Syntax:
flx.phys_tauphi2temp(temp_dewp, phi)- Description:
Evaluates the temperature associated with a given dew point temp_dewp and humidity phi.
Example:
If the dew point is at 7.8°C and we have a humidity of 40%, the associated temperature is:
temp = flx.phys_tauphi2temp(dew_point,0.4 )
print(f"{temp:.1f} °C")
22.0 °C
relative humidity from dew point and temperature#
- flx.phys_tauptemp2phi()#
- Syntax:
flx.phys_tauptemp2phi(temp_dewp, temp)- Description:
Evaluates the humidity associated with a given dew point temp_dewp and temperature temp.
Example:
If the dew point is at 7.8°C and the temperature is 22°C, the humidity is:
phi = flx.phys_tauptemp2phi(dew_point, 22. )
print(f"{phi*100:.0f}%")
40%
absolute humidity from temperature and relative humidity#
- flx.phys_abs_humidity()#
- Syntax:
flx.phys_abs_humidity(temp, phi)- Description:
Evaluates the absolute humidity as a function of temperature temp and humidity phi.
Example:
For a temperature of 22°C and 40% humidity, the absolute humidity is:
abs_hum = flx.phys_abs_humidity(22.,0.4 )
print(f"{abs_hum:.1f} g/m³")
7.7 g/m³
Application examples#
Maximum humidity to avoid mold (on walls)#
## surface temperature (of critical element)
t_s = 9. ## [°C]
## temperature at dew point
t_dew = flx.phys_dewpoint(t_s,0.8 ) ## above 80% relative humidity at the critical element, it becomes critical
print(f"{t_dew = :.1f} °C")
## vapor pressure
svp = flx.phys_temp2svp(t_s)
vp = 0.8 * svp
print(f"{vp = :.2f} hPa")
## absolute humidity at surface
t_s_abs = flx.phys_abs_humidity(t_s,0.8 )
print(f"{t_s_abs = :.1f} g/m³")
print()
## mold becomes likely if for the specified temperatures, humidity is exceeded
print("room temp rel. humidity vapor pressure abs. humidity")
for temp in [19.,20.,21.,22.,23.]:
phi_of_temp = flx.phys_tauptemp2phi(t_dew, temp )
print( f"{temp:.0f}°C, {phi_of_temp*100:.0f}%, {phi_of_temp*flx.phys_temp2svp(temp):.2f} hPa {flx.phys_abs_humidity(temp,phi_of_temp ):.1f} g/m³" )
t_dew = 5.7 °C
vp = 9.17 hPa
t_s_abs = 7.0 g/m³
room temp rel. humidity vapor pressure abs. humidity
19°C, 42%, 9.17 hPa 6.8 g/m³
20°C, 39%, 9.17 hPa 6.8 g/m³
21°C, 37%, 9.17 hPa 6.8 g/m³
22°C, 35%, 9.17 hPa 6.7 g/m³
23°C, 33%, 9.17 hPa 6.7 g/m³
Airing of a room (minimum humidity that can theoretically be achieved)#
## outside temperature
t_out = 5.2 ## [°C]
## outside humidity
phi_out = 0.9
## inside temperature
t_in_lst = [19.,20.,21.,22.,23.]
## vapor pressure
vp = phi_out * flx.phys_temp2svp(t_out)
print(f"{vp = :.2f} hPa")
## temperature at dew point
t_dew = flx.phys_dewpoint(t_out,phi_out )
print(f"{t_dew = :.1f}°C")
## absolute humidity
abs_hum = flx.phys_abs_humidity(t_out,phi_out )
print(f"{abs_hum = :.1f} g/m³")
print()
## minimum humidity (inside) that can be (theoretically) achieved for the specified temperature
print("temp rel. humidity vapor pressure abs. humidity")
for t_in in t_in_lst:
phi_in = flx.phys_tauptemp2phi(t_dew, t_in )
print( f"{t_in:.0f}°C, {phi_in*100:.0f}%, {phi_in*flx.phys_temp2svp(t_in):.2f} hPa {flx.phys_abs_humidity(t_in,flx.phys_tauptemp2phi(t_dew, t_in ) ):.3f} g/m³" )
vp = 7.96 hPa
t_dew = 3.7°C
abs_hum = 6.2 g/m³
temp rel. humidity vapor pressure abs. humidity
19°C, 36%, 7.96 hPa 5.901 g/m³
20°C, 34%, 7.96 hPa 5.881 g/m³
21°C, 32%, 7.96 hPa 5.861 g/m³
22°C, 30%, 7.96 hPa 5.841 g/m³
23°C, 28%, 7.96 hPa 5.821 g/m³