Bronkhorst®
Instruction Manual Vapor Delivery Module
9.17.079D
22
Be aware that both heater and tracing temperature depend on the location of the sensor. Therefore, it is advised to set the
heater temperature approximately 20°C above the theoretical temperature.
In addition, it is advised to set the tracing temperature another 10°C higher.
5.3.1
Operation example
Application
The VDM can be used for generating certain humidity in a gas stream. Carrier gas and liquid (water) are controlled to
regulate the humidity. The water is mixed with the gas and consequently evaporated. The humidity at a certain temperature
corresponds with a certain ratio of gas and water, this ratio can be set by the flow controllers which are part of the VDM.
Calculation example for setting of relative humidity
At atmospheric pressure, at 80°C, 2 l
n
/min Air has to be moistened. Which water flow is needed for a r.h. of 50%. The vapor
pressure of water at 80°C is 473.3 mbar according to FLUIDAT®.
FLUIDAT® on the Net: Bronkhorst's interactive Flow Calculations and routines generating Physical Properties. Visit
www.fluidat.com
Assumptions:
·
consider water vapor as an ideal gas
·
1 mole of ideal gas at normal conditions = 22.4 l
·
1 mole of water is 18 g and 1 hour is 60 min.
·
1 atm. = 1013.25 mbar.
At 100% r.h., the (Mole)Ratio between gas and water is:
The mole ratio:
So in a gas flow of 2 l
n
/min, the saturated vapor flow (100% r.h.) is:
and in [g/h]:
At 50% r.h., the (Mole)Ratio between gas and water is:
The mole ratio:
So in a gas flow of 2 l
n
/min, the saturated vapor flow (50% r.h.) is:
and in [g/h]:
