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Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: mufan on July 30, 2015, 11:13:20 AM

Title: thermodynamics of cooling water for hot process
Post by: mufan on July 30, 2015, 11:13:20 AM

Hi,
I work with cooling towers where essentially cool water (85 deg F) is sent to a heat exchanger where it picks up 10 deg F and returns to the tower at 95 deg F.  My questions are:

• if you gain 10 deg F in water temp then do you essentially cool the process by 10 deg F.  is this exchange 100% efficient like that?I'm thinking the water flow across the exchanger will play into somehow
• and therefore, can you determine the temperature of the process being cooled from the difference in cool supply water and the hot return water?

Title: Re: thermodynamics of cooling water for hot process
Post by: Corribus on July 30, 2015, 11:41:27 AM

One of our resident engineers will probably have a more specialized response, but in general even if a heat transfer process is 100% efficient, you still have to take into account heat capacities to know what actual temperature changes will be. That is to say, a 100% efficient process is not the same thing as one in which the temperature drop by the heat donor equals the temperature gain by the heat acceptor.

Title: Re: thermodynamics of cooling water for hot process
Post by: Irlanur on July 30, 2015, 11:41:54 AM

Quote

if you gain 10 deg F in water temp then do you essentially cool the process by 10 deg F.

If I understand you correctly then you are completely wrong.