Pipe Flow Analysis: Temperature Changes

In this simulation a channel's cross section was analyzed, 5 NPS 1/8 SCH 40 pipes were used to cool down stationery water in a larger channel, flow was analyzed for 10s (more CPU time for longer calculation on my CPU).

Ambient Temperature: 313.15 K
Initial Pipe (all 5 pipes) Temperature: 313.15 K
Water Temperature: 281.15 K

Water Flow Rate (Pipes): 0.00015 m^3/s (9 lt./min)
Water Flow Rate (Channel): 0 m^3/s

Material of the Pipes: Steel Stainless 302 (Pre-Defined\Alloys)
Gravity: On

Coarse Mesh (3/8 Level)

As soon as the flow started, the pipes and water (stationery) started to cool down, as you can see from the temperature graphics attached (all photos are after 10 s of flow).

It will take a large amount of CPU power and time to calculate time for water (stationery) and all the 5 pipes to be at same temperature as cold water.