Pressure profile for open system is not the same as closed system.
From open loop system, we can see that if we route the pipe of open type cooling tower expecting that it will be the same characteristic of reverse return as closed loop system, the pipe routing may cause you misinterpret the actual pressure profile of the system.
The pressure in open loop is start from atmospheric pressure and is break the loop at the discharge pipe of cooling tower (also atmospheric pressure), so there is just only direct return piping. There is no reverse return characteristic. If we rout the pipe to mimic the “look like” of reverse return, we just only add pressure loss to the system without offsetting the pressure loss for balancing and waste money to pipe without any benefit.
However, if the cooling tower is closed type, routing the reverse return will make the system pressure more uniform and easy for balancing (the same as in chilled water system).
Below is the “look like” reverse return for open loop cooling tower system, however, it is not. This routing is usually seen in the cooling tower plant using with single-pass chiller for miminimize the pipe lenght, also pipe cost.
For open loop cooling tower, the uniform pressure will be achieved by looping the pipe or upsize the main header. This will be in other note I will provide.
Related notes:
Pressure profile of condenser water system
Understanding the pressure profile in open-loop water system
Pressure profile of chilled water system
Direct return vs Reverse return – comparison in pressure profile perspective
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