7 replies to this topic

[ayche]

Well I was going through the topic of humidification and after completing the topic I was solving some multiple choice questions. I came across this question saying that when temperature increases at constant humidity(absolute humidity) what happens to relative humidity and wet bulb temperature?

As far as I my understanding goes, Since the moisture content remains the same and the temperature is increased ,Relative Humidity should decrease, which is what the answer said, but it also said that Wet Bulb Temperature(WBT) increases.!

Now as the relative humidity decreases that means the air is more dry which means that the difference between wet bulb bulb and dry bulb temperature should be more now and WBT should decrease. 

Please help me with this doubt of mine.

But it says WBT increases.!!

Ayche

[breizh]

  http://www.uigi.com/WebPsycH.html

 

Consider this calculator to support your query . Test this tool , it should help you out .

 

Breizh

Edited by breizh, 25 September 2013 - 01:33 AM.

[ayche]

Sir ,the calculator will give me theoritical value,what I am trying to ask is why wet bulb temperature increases when relative humidity decreases, at constabt absolute humidity? Whats the concept behind this?

[ayche]

I meant calculator will give the numerical value

[breizh]

My advice , take a look at a psychrometric chart and you should get your answers .This is typical homework .

Hope you understand .

 

Breizh

[ayche]

I did.! it was a slight confusion. Thank you sir for the help.!

[Propacket]

Good question: If absolute humidity is constant and temperature is increased, relative humidity decreases because of increase in vapor pressure. Why wet bulb temperature increases although relative humidity is decreasing?

 

My friend! Wet bulb not only depends upon relative humidity but also on gas temperature. Lets take an example:

Case 1: Gas at 100 degF and 50% Relative Humidity. You start cooling the gas from 100 degF by saturating the gas with water until it achieves Wet Bulb Temp say 70 degF.

Case 2: Gas at 150 degF and 50% Relative Humidity. You start cooling the gas from 150 degF by saturating the gas with water until it achieves Wet Bulb Temp say 120 degF.

 

Result: Wet bulb temperature depends upon gas temperature too.

 

Although relative humidity decreases (at constant absolute humidity) due to increase in temperature, wet bulb temperature will increase due to increase in gas temperature.

[breizh]

Ayche,

 

A good resource , in addition to the comments above .

 

This should help.

 

Breizh