[usman_liaquat]

moist asir at 35°C with dew point of 20°C is to be dehydrated so that during is passage through a large cold room for food storage excess ice formation can be avoided on the chilling coils. If 72% of initial water in moist air is to be removed and moist air enters at 40 psi, to what temperature should the air be cooled at constant pressure?
Solve using Cox chart from Basic Chemical Processes by Olaf A. Hougen and Watson.

guys please help me i am 1st semester student of chemical Engineering and this question is given to me in Assignment and i can not solve it.

[Enthalpy]

Hi usman_liaquat,

what you first need is some relation or graph between the air temperature and the amount of water vapour it can contain. I wouldn't be surprised if that were the chart in the referenced book.

When you have that relation or graph, invest time in meditating it. Apparently you missed that part of the story.

[usman_liaquat]

Hi usman_liaquat,

what you first need is some relation or graph between the air temperature and the amount of water vapour it can contain. I wouldn't be surprised if that were the chart in the referenced book.

When you have that relation or graph, invest time in meditating it. Apparently you missed that part of the story.

and how will i relate the dew point?
and there is a temperature-vapor pressure graph.

[billnotgatez]

@usman_liaquat
You have to show your attempts or thoughts at solving the question to receive help.
This is a forum policy.
Click on the link near the top center of the forum page.
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[billnotgatez]

Some things you might post may assist others in helping you
If you have done a GOOGLE search on the table(s) mentioned and post the link
Of less help but may be useful is the ISBN of the book mentioned.

You might start by
Stating your understanding of how Dew Point relates to the amount of water in the air.

By the way
GOOGLE and WIKIPEDIA can be your friends

[usman_liaquat]

@usman_liaquat
You have to show your attempts or thoughts at solving the question to receive help.
This is a forum policy.
Click on the link near the top center of the forum page.
Forum Rules: Read This Before Posting.
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okay i am solving it by myself, i have found the molal humidity from the chart to be 0.037 and as we know the molal humidity is moles of vapor/ moles of vapor-free (dry) gas. so taking 1 mole of dry gas as basis we have moles of water can i find volume by considering these moles of water as of gas' by comparing it to the volume occupied by 1 mole of gas i.e. 359 cubic feet so it will occupy 13.283 cubic feet? and also i have a question the vapor pressure of water or any other liquid at dew point is equal to the vapor pressure at a temperature higher than dew point?