Re: Dry And Wet Bulb Temperature Neasurement
I may be missing something here but why would you want to even try to do the measurement? I am not sure the concept has any meaning above 100C?
Is the function of wet bulb measurement not to find out what percentage of 100% relative humidity your gas stream is at?
If the gas stream is at more than 100C (assuming water and ambient pressure of course) then the gas stream will have unlimited capacity to carry water vapour. Condensation is purely dependent upon the "dry" temperature. ■
Re: Dry And Wet Bulb Temperature Neasurement
Dear Mall,
Relative Humidity (RH) = (vapor pressure)/(saturated vapor pressure)
If the temperature is at or above the boiling temperature, all the water evaporates (boils off) and will have the same temperature as the air.
Then you are dealing with 2 gases (air and overheated steam) and the equilibrium between evaporation and condensation no longer exists.
Extracting a sample from the air stream in the duct and cooling it down to measurable temperatures could be a solution.
success.
teus
attached a spreadsheet to calculate RH
Attachments
■
Teus
Re: Dry And Wet Bulb Temperature Neasurement
sorry......
actually just to get the the moisture content of the air .......by using psychrometric chart
RHumidity proble hygrometer can be used below temp 80 deg C.
teus, what do mean the vapor pressure, how u measure it using pitot tube and manometer as static pressure or what?
tq for replies..... ■
Re: Dry And Wet Bulb Temperature Neasurement
Dear Mr Mall,
The pressure of an air-water vapor mixture is the addition of 2 pressures:
-the dry air pressure + the vapor pressure.
Below the boiling temperature (which can be increased under higher pressures) ,
the saturated vapor pressure is dependant of the actual temperature.
At saturation there is an equilibrium between the water molecules going into the vapor phase
(evaporation) and water molecules going back into the liquid water phase (condensation).
This temperature is measured by the wet bulb thermometer.
The temperature difference (psychometric difference) between the wet and the dry thermometer is an indication for the relative humidity of the air-vapor mixture, which then can be calculated.
best regards
teus ■
Teus
Re: Dry And Wet Bulb Temperature Neasurement
Use a continuous feed of water to the wick.
Scott ■
Dry and wet bulb temperature neasurement
hi
for ducting from grinding machine or dryer, for temperature below 90 deg C, for we can wet the bulb with cotton etc and insert inside ducting to get the wet bulb temperature.
but for high temperature > 120deg C or 200 deg C, this method seems not practical.
do you have proper and accurate measurement at high temperature?
pls share
tq ■