length of each coil’s refrigerant circuits

[wilsoncheung]

Hello,you guys!

In the evaporator or condenser, how to design the length of each circuit? It's the same that how many circuits we may design.

As we know, it's quite difficult to calculate the refrigerant pressure drop through the tube. So it's not easy to design the circuit according to the pressure drop. But I think there is some rule of thumb about the length. It may come from the engineers' experience.

Thank you!

Wilson

[GMRILocust]

Hello,you guys!

In the evaporator or condenser, how to design the length of each circuit? It's the same that how many circuits we may design.

As we know, it's quite difficult to calculate the refrigerant pressure drop through the tube. So it's not easy to design the circuit according to the pressure drop. But I think there is some rule of thumb about the length. It may come from the engineers' experience.

Thank you!

Wilson

about 1000 times the diameter of the tube,
for instance, the length of every circuit is more or less 10m,(not to be longer than 12~15m)
:|...my poor english///

[GMRILocust]

about 1000 times the diameter of the tube,
for instance, the length of every circuit is more or less 10m,(not to be longer than 12~15m)
:|...my poor english///

sorry, for a phi9.52*0.36 tube..

[Magoo]

There is no rule of thumb, it comes back to effective surface area and heat transfer per circuit. Added complication is pressure drop per circuit. Small coils single circuit, large coils multi-circuit, whether condensers or evaporators.
Remove rule of thumb from your vocabulary. Calculate!!!!.
Rule of thumb is in the same league as "assume " and assume translates to Ass-u&-me.
magoo

[US Iceman]

Rule of thumb is in the same league as "assume " and assume translates to Ass-u&-me.

And that is why an assumption should never be used for design work in a finished product. An assumption is OK, when and only when, it is relevant to the mode of operation that particular piece of equipment will see and be operated within.

Coil circuiting is a lengthy discussion full of specifics I am not prepared to get into, so I will bow out gracefully.

[wilsoncheung]

There is no rule of thumb, it comes back to effective surface area and heat transfer per circuit. Added complication is pressure drop per circuit. Small coils single circuit, large coils multi-circuit, whether condensers or evaporators.
Remove rule of thumb from your vocabulary. Calculate!!!!.
Rule of thumb is in the same league as "assume " and assume translates to Ass-u&-me.
magoo

Thanks,Magoo!
Yes, rule of thumb is not good,but it can guide us. As it's quite difficult to calculate the pressure drop of the two phase refrigerant flow, if we use the macro way to calculate, it may not be correct or accurate.

But if use the micro way, like using CFD to simulate the flow, it would be too difficult and time-consuming.

And if there is some experience, we will know the suitable range for the tube length, at least we can check whether our calculations falls into the range or not.

I suppose that we may use the suitable gas refrigerant velocity to determine the number of circuits.

[wilsoncheung]

about 1000 times the diameter of the tube,
for instance, the length of every circuit is more or less 10m,(not to be longer than 12~15m)
:|...my poor english///

Thanks,GMRILocust!
1000 times of the diameter? How you get this figure. It should be different when using different refrigerant, like R22, R407C,R134a.

[Peter_1]

It was a rule of thumb
We take a max circuit length of 30 m

[wilsoncheung]

Peter_1, is it 30 meter too long?

[desA]

But if use the micro way, like using CFD to simulate the flow, it would be too difficult and time-consuming.

Using today's cfd technology, it would most likely also be completely wrong...

[Peter_1]

We use 30 m. as a max length

[wilsoncheung]

Using today's cfd technology, it would most likely also be completely wrong...

desA，why you say so? It seems that you have that kind of experience, pls let me know? Thank you!

Using CFD to simulate two phase flow, especially including heat exchange, is extremely difficult, we need to use the right model, otherwise we would get the other way around.

Ok, Let's get to the point. Anyone has comment on the length of each coil's circuit? Pls do not hesitate to tell me, thank you!