GPM/TR Vs Delta T

[harrysharry]

Does any body has GPM/TR Vs Delta T (Temp. difference) chart for Chillers. Though we can get it thru TR=GPM x Temp diff/24. But need to clarify

01. whether this formula holds good for Condenser flow as well?
02. Whether this formula holds good for any temp difference? i mean not necessarly 10 Def F.

thanks for your support.

 

[quark]

That formula holds good for all types of water and for any temperature difference. This formula is derived from the basic formula Q = m x Cp x dT, where Q is heat rejected or absorbed, m is mass flowrate of water, Cp is specific heat of water and dT is the temperature difference. You should be careful to use consistent set of units.

I didn't happen to see such a chart but your chiller manufacturer can be able to provide you one. It will be useful only if you want to account for the derating of the chiller, if any.

 

[HVAC68]

For condenser flow, the capacity of the chiller needs to be multiplied by the heat rejection factor. This could vary depending on the type of equipment and the operating parameters.



HVAC68

 

[lilliput1]

For condenser water, heat rejection = cooling load Btu/hr + input to chiller in Btu/hr = condenser gpm x 500 x (95-85)

 

[harrysharry]

Thanks to all of you for your valuable input.

In fact i was trying the above equation recommended by lilliput and i found that we can calculate chiller efficiency (or Kw consumption) in case we know cond flow, chiller capacity and Delta T across condenser.

while trying this equation i have found that i am getting close to results in case Delta T is 10 Deg F but if i vary Delta T (Say less than 10 Deg F) i am not getting even closer to Chiller input. it means there is definitly some relation with Condenser water temp difference.

THAT WAS THE MAIN REASON I HAVE ASKED MY FIRST QUESTION WHETHER TR=GPM x Temp diff/24 HOLDS GOOD FOR ANY TEMP DIFFERENCE ? WHETHER IT HOLDS GOOD FOR CALCULATING CONDENSER FLOW ALSO ??

Pls comment..thanks

 

[lilliput1]

Yes it is. The basic equation is heat in = heat out. I should have but Temp Diff in the above equation, not 95-85. With more efficient chillers & w/ condenser water flow sized at the rule of the thumb 3 gpm/ton, condenser water temperature difference would be less than 10°F.