Chilled water pipe sizing.

[RMERMP]

Can someone please confirm if im using the correct way of sizing up a chilled water pipe? the total TR of all the fan coil unit is 40 TR. 40TRx 2.4GPM = 96GPM
then i input it into the sizer it said im should us3 80mm size pipe. my other question is, how can i size up the pipes in their max capacities?. thanks,

 

[willard3]

Get help from a senior person in your office with this.

 

[EnergyProfessional]

sizing of pumps and pipes is the same as for heating. BUT: viscosity of cold water (or even glycol) is much higher and pump performance is degraded. Pump manufacturer software let's you enter the fluid type and temperature.

 

[pocketengineer]

Depends on your pipe design velocity. 80mm pipe size would give you 1.2 m/s pipe velocity. There are some guides on pipe velocity, example in Carrier or Ashrae Handbooks.

 

[ZDR1985]

What is your delta T?

For pipes 50mm and below, consider max velocity 1.2 m/s and max friction loss of 600 Pa/m.
For pipes larger than 50mm, consider max velocity 2.4 m/s and max friction loss of 400 Pa/m.

If it's in then you should be good.

 

[dynamo78]

The recommended pressure drop for chilled water pipe is from 1 to 4 feet per 100ft I usually design it at 3 ft per 100 ft of equivalent length. It helps too in hydronic balancing because of uniform PD. Just my input Brothers.

 

[EnergyProfessional]

you all are right, use the maximum velocities AND pressure drops.
Velocities will be independent of the fluid, but pressuredrop rises a lot with cold glycol

 

[urgross]

I agree that the range of velocity and friction loss are the basis of sizing. Keep in mind any planned expansion and increased roughness in aging piping. I tend to use mid-point or lower on the range, then go up to next standard size, especially for mains. Also depends on the type of system that you have and if diversity can be considered.