Question about chiller flow control with bypass

[belburase]

I’m working with a chiller to cool a system, and I’m trying to better understand how a bypass affects the flow rate. My pump operates at 10 LPM, and my system requires between 4-8 LPM. I have a bypass installed, and I’m trying to determine whether opening it will increase or decrease the flow going to my system.

Looking at the pressure vs. flow rate graph (50 Hz) for the pump, it seems that if I open the bypass and divert some water from the main line (the one going to my system), the pressure decreases. But I’m not sure whether that means the flow to my system increases or decreases.

Does opening the bypass always reduce the flow to my system? Or does the total flow from the pump increase, causing more flow in both paths? In other words, when opening the bypass, do I move to the right on the pressure-flow graph (higher total flow), or does the bypass always reduce the flow to the system?

I also have the option to buy a flow regulator valve if that would be a better solution.

Any advice would be greatly appreciated!

Thanks!

 

[LittleInch]

Buy the valve.

It's not really possible to say without knowing all the data, but simply opening a bypass could reduce flow through your system, but you will go right on your pump curve.

A valve is fool proof.

 

[belburase]

Buy the valve.

It's not really possible to say without knowing all the data, but simply opening a bypass could reduce flow through your system, but you will go right on your pump curve.

A valve is fool proof.

Thanks for your response!

I see what you're saying about moving to the right on the pump curve when opening the bypass. My question is whether this always reduces the flow to my system or if, in some cases, the total increase in pump flow could mean my system still gets more than expected.

For example, if my pump is currently at 10 LPM and I open the bypass aiming for 7 LPM, but this moves the pump to 13 LPM total, would my system still get less than the original 10 LPM, or is there a scenario where it could receive more?

I understand that it depends on multiple factors, but I’m trying to confirm if the flow to my system will always be lower than the initial 10 LPM.

 

[georgeverghese]

Bypass control schemes with a single valve on the bypass line have very limited operating range. A better scheme is to use a 3way throttle valve. An even better scheme will have a control valve on the main line feeding the chiller and another control valve( which may be on the bypass or operating as a min flow recycle). Ask a process controls engineer to help you with this if not familiar.

 

[goutam_freelance]

also have the option to buy a flow regulator valve if that would be a better solution.

This could be a solution, but bypassing is still needed to ensure minimum pump flow.

 

[Snickster]

The overall pump flow will increase but the flow to the system will decrease.

 

[pierreick]

Hi,
A sketch will save words and will limit confusion.
Pierre

 

[LittleInch]

This could be a solution, but bypassing is still needed to ensure minimum pump flow.

Agree. A closer look at the curve shows flow through the pump should be greater than about 8 lpm (avoid the dashed line section).