Pump and Pipe Sizing Calculation for Chiller Water System

Pump and Pipe Sizing Calculation:
Pump Head Calculation for Chiller water System
Pump head is the total resistance that a pump must overcome
1. Velocity Head
Accelerating water from a standstill or low velocity at the starting point to a velocity at an ending
point requires high energy. In the closed system the starting point as same as the end point.
Therefore the beginning velocity is same as the ending velocity, so velocity head is not a
consideration.
2. Pressure Head
When liquid is pumped from a vessel at one pressure to a vessel at another vessel, pressure
head exist. Common application is condensate pump and boiler feed pump. Condensate pumps often
deliver water from an atmospheric receiver to a deaerator operating at 5 PSIG, meaning that in
addition to other heads, the pump must overcome a pressure head of 5 PSIG.
3. Friction Head
This is also called pressure drop. When fluid flows through any system component, friction
results. This causes a loss in pressure. Components causing friction include boilers, chillers, piping,
heat ex changers, coils, valves, and fittings. The pump must overcome this friction. Friction head is
usually expressed in units called "feet of head."A foot of friction head is equal to lifting the fluid one
foot of static height.
4. Static Head
Static head represents the net change in height, in feet, that the pump must overcome. It applies
only in open systems. Note that in a closed loop system, the static head is zero because the fluid on
one side of the system pushes the fluid up the other side of the system, so the pump does not need to
overcome any elevation.
Total heat load h = Cp x ρ x q x dt
h = heat load(BTU/hr)
Cp = 1 (BTU/lbm F) for water
ρ = 8.33 (lbm/gal) for water
q = Water volume flow rate (gal/min)
dt = Temperature difference
Sl. No. Parameter Symbol Value UOM
1 Heat load h 3412142.00 BTU/hr
2 Density ρ 8.33 lbm/gal
3 Specific heat Cp 1.00 BTU/ lbm F
4 Water flow rate q 14629.32 gal/min
5 Temp difference dt 28.00 F

Pump is a most common equipment used in a chemical plant to transfer fluid from one location to
another. This article shows how to do pump sizing calculation to determine differential head required
to be generated by pump based on suction and discharge conditions.
Pressure at pump suction is calculated as following
where,
P1 is pressure at liquid surface in suction vessel.
Pstatic is pressure due to height of liquid level above pump suction.
ΔPEquipment is pressure drop in an equipment at pump suction like strainers, filters etc.
ΔPfriction is pressure drop due to suction pipe and fittings.
Pstatic
where, h1 is height of liquid above pump suction, SG is specific gravity of liquid, ρ is liquid density
(kg/m³) and g is gravitational constant (9.81).
ΔPfriction
ΔPPipe is pressure drop in a pipe due to single phase fluid flow. ΔP_Fittings is pressure drop due to pipe
fittings, which can be calculated based on 2-K & 3-K method.