Pipe sizing Flashcards
Explain the primary pipe sizing process:
Mass flow rate of water is determined as a function of:
target heat output from emitters/(specific heat capacity of water*flow & return delta T)
Minimum cross sectional of pipe is calculated by:
(Mass flow rate * density)/target velocity.
Target velocity is 1m/s for smaller pipes.
Minimum cross sectional area of the pipe is rounded up to the (internal diameter) of the next readily available pipe size.
What is the secondary pipe sizing process
Calculate heat losses from each section of pipe using data provided in the CIBSE tables. Revise the volume flow rates to include these heat losses. Revise the minimum pipe sizes to the new volume flow rate. Revise the actual water velocity to the new volume flow rate and if necessary pipe size.
What is the process of calculating pressure drop in a pipe run.
Darcys equation states that
Delta P =
(Friction coefficientLengthdensity of the fluidvelocity^2)/2pipe diameter
The friction coefficient is taken from the moody diagram as a function of pipe roughness and the reynolds number.
The pressure drop accross the fittings will be provided in the manufacturers data.
The pump duty is the pressure drop accross all sections of pipe and fittings and emmitters.
