Could you please help me in this quistion
I had this quistion during an enterview yesterday
If we have chiller and the outlet GPM of this chiller should be 1000 GPM
what should be the capacity of the centrifugal pump which is feeding the chiller
Assuming the following
the deta T across the chiller at full load is 10 degrees F
the chiller capacity is 800 ton/r
the refrigerant is R-134a
the pressure drop across the chiller is 12 psig

And the most important quistion which i been asked is
Is there is a percentage that we can added to the outlet GPM 1000 let us say 10%
(100 GPM) so we can directlly say the pump capacity should be hiegher 105 above the outlet of the chiller

Could you please help me in this quistion

I had this quistion during an enterview yesterday
If we have chiller and the outlet GPM of this chiller should be 1000 GPM
what should be the capacity of the centrifugal pump which is feeding the chiller


Assuming the following
the deta T across the chiller at full load is 10 degrees F
the chiller capacity is 800 ton/r
the refrigerant is R-134a
the pressure drop across the chiller is 12 psig

And the most important quistion which i been asked is
Is there is a percentage that we can added to the outlet GPM 1000 let us say 10%
(100 GPM) so we can directlly say the pump capacity should be hiegher 105 above the outlet of the chiller


بسم الله الرحمن الرحيم و الصلاة و السلام علي اكرم الخلق سيدنا محمد صلي الله عليه و سلم
اخي الكريم اجابة اسئلتك كالآتي:
في حاله ما اذا كانت سعه التشلر 1000gpm فإن سعة المضخة الابتدائيه هي ايضاً 100gpm و اجمالي سعة المضخات الثانويه يساوي اجمالي سعة التشلرات اما الــStatic Head أو الضغط المانومتر للمضخات فيحسب بالنسبه للمضخه الابتدائيه علي اساس فاقد الاحتكاك علي التشلر + فاقد الاحتكاك علي مواسير الشبكه الافقيه مضاف الي الاجمالي 5%معامل امان و بالنسبه للمضخات الثانويه فيحسب فقط فاقد الاحتكاك بالشبكه مضاف اليها فاقد الاحتكاك لمجموعات المحابس بالشبكه
و سؤالك هذا خاص بالمضخه الابتدائيهprimary pump و بخصوص اضافة نسبه 10% فأنا لم افهم هذا السؤال حيث ان التشلر سعه 1000gpm يعني ان قدره التبريد تساوي 416.7TR أو طن تبريد و هذا يعني انه تم حساب حمل التبريد للمبني و علي اساسه تم عمل اختيار للتشلر و يستحيل رفع سعه التشلر بعد تصنيعه و تركيبه و في حالة زياده معدل السريان فإن القدره التبريديه للتشلر ستقل بسبب زيادة سرعه المياه التي ستؤثر علي عمليه التبادل الحراري تأثير عكسي و بالتالي فلن يتم الحصول علي درجة التبريد المطلوبه و وفقك الله

الأخ المهندس محمود سليم
تحية طيبة. أشكر لك أهتمامك وردك على سؤالى
أعتزر على كتابتى بالأنجليزية لأن كتابتى بالعربية بطيأة جدا

The question I had during the interview was
Is the capacity of the chilled water pump before the chiller “Primary Pump” should be higher or lower or exact as per the chiller design flow rate and why?
What I have achieved from the question is, Is there an easy way to calculate or assume the capacity of the chiller pump and to know if its matched the chiller capacity or not when you are in the chiller room and your only data is the pump name plate and the chiller design flow rate.
Put into consideration the following:
1- The pump is located about 10 meters away from the chiller.
2- The pipe fittings.
Any how my answer was that the pump should be higher capacity than the chiller design flow rate as there will be a pressure drop on lines and valves in between the pump and the chiller and I can regulate the exact amount of flow rate to feed the chiller by adjusting the chiller outlet balance valve.
Is that correct answer?

Please Mahmoud, don’t forget to answer my question if there is a short answer like adding a percentage to the pump capacity to compensate the pressure drop in betweens.

Thanks again.