2 replies to this topic

[irahjo]

Hi,

Im trying to design condenser for vapor compression cycle. My problem is , how to find heat transfer coefficient for superheated vapor. from the resource I read, i need to check either the the wall temperature is below or above the saturation temperature to check will the condensation will directly occur. but no proper guidence is given. whats the best way to check the wall temperature and if the saturation temperature is above saturation temperature, how to determine its coeffcient and find the overall coefficient. The condition of the fluid is below:

Superheated temperature:409K

Saturated temperature: 316K

Available coooling water: 296

 

Thanks

[Napo]

Irahjo,

 

The influence of superheated steam in the condensation is minimal and in the practical calculus cannot be take in account.

 

I send you information related from the book "Fundamentals of Heat Transfer for Process Engineering", by Azbel D., 1984. pp. 275-276.,

 

Napo.

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[srfish]

irahjo

 

I don't know how a condenser with desuperheating can be designed without using a trial and error calculation. First the tube wall temperature is  estimated using a gas heat transfer coefficient in the desuperheating zone. Then the trial and procedure is used until the calculated tube wall temperature matches the assumption. If the calculated tube wall temperature is above or the same as the inlet temperature then a normal LMTD and a overall condensing heat transfer rate can be used. If the calculated tube wall temperature is less than the inlet temperature then there will be two zones of heat transfer, a gas zone and a condensing zone.