A clothes dryer discharges moist air at 35 degrees C and 80 percent relative hum

Question

      A clothes dryer discharges moist air at 35 degrees C and 80 percent relative humidity (at 1 on the diagram). The flow is guided through a duct to the roof where it is vented to the atmosphere. Due to heat transfer int he duct, the air is cooled to 24 degrees C and fully saturated when it exits the duct (at 2 on diagram). assuming that the air is at atmospheric pressure, use the psychometric chart to determine:

a) the absolute humidity of the moist air discharged from the dryer (at diagram 1)
b) the absolute humidity of the moist air when it exits the duct (at 2 on the diagram)
c) the heat transfer from the pipe (in kJ/kg of air) by treating the duct as a steady flow device. Note that h = CpT +(omega)hg

Please take your time with this, the most thorough and well explained response will be rated.

http://i39.tinypic.com/1195wdk.jpg

here is a picture to help

Explanation / Answer

(1)

AT POINT 1

DBT=35 DEG CEL

R.H.=80%

W1=0.0287 KJ/KG OF D.A.

(2)

AT POINT 2

DBT=24 DEG CEL

R.H.=100%

W2=0.0184 KJ/KG OF D.A.

(3)WE KNOW THAT

H= CpT +(omega)Hg

H1=1.005*35+0.0287*2565

=108.79 KJ/KG OF D.A.

H2=1.005*24+0.0184*2545=70.94 KJ/KG OF D.A.

the heat transfer from the pipe (in kJ/kg of air) by treating the duct as a steady flow device

=H1-H2=108.79-70.94=37.84KJ/KG OF D.A.

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