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mirza zaheer
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Temp for mixed flow - Chilled water.

09/05/2009 4:15 AM

Hi,

If we have an absorption chiller say with a capacity of 100l/s chilled water flow rate & 7 deg the supply temp/outlet temp from the chiller. From this 100l/s if we take one branches of 25l/s to an electric chiller in series & drop down the temperature for this 25l/s flowrate from 7 to 4 deg c. After this if the both both flow rates that is 25l/s @4 deg c & the remainig 75l/s @ 7 deg c from absorption chiller if mixed again in one header to take it to the AHU'S/END USER What will be the temperature of this mixed flow.

With your answer. please give the formula that is been used.
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JohnDG
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#1

Re: Temp for mixed flow - Chilled water.

09/05/2009 6:22 AM

((75 x 7) + (25 x 4)) ÷ 100 = 6.25° (assuming the temperatures are still 7° and 4° where the mixing happens).

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#2
In reply to #1

Re: Temp for mixed flow - Chilled water.

09/06/2009 8:33 AM

and it is assumed that the density and specific heat remains unaltered for the coolent at 7C and 4C. This may not be the case for water. However, this calculation sure is a good rule of thumb to get neat to actual value.

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#3

Re: Temp for mixed flow - Chilled water.

09/06/2009 11:24 AM

If there is no hitch in this problem, then the temperature of the mixed flow will be

(75*7+25*4)/100= 6.25 deg.

Regards.

Anant
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bhrescobar
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#4

Re: Temp for mixed flow - Chilled water.

09/07/2009 6:21 PM

Consider calculating it in absolute units, this is the way it should be done.

(75 l/s x 280.15K + 25 l/s x 277.15K) = 100l/s @ 279.4 K or 6.25 degC

COnsidering no losses, fluid properties constant, etc.

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Mikerho
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#5

Re: Temp for mixed flow - Chilled water.

09/08/2009 8:34 AM

Am I the only one who thinks this sounds like homework?

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PWSlack
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#6

Re: Temp for mixed flow - Chilled water.

09/09/2009 7:12 AM

Ignoring the variation of density of water with temperature, 61/4degC, by simple proportion.

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