Lecture Objectives:
• Plumbing
• Hydronic distribution systems
–Chiller/Boiler – Storage – Building
• Pumps
Reading assignment:
Chilled Water Plant Design Guide (Section 4)
http://energydesignresources.com/media/2305/EDR_DesignGuidelines_CoolToolsChilledWater.pdf
Primary/Secondary and
Tertiary Pumping (schematics A&B below)
Coil Pumping Strategies
Variable speed pumps vs. Single pas Valve
vs. Mixing valves vs. Diverting Valves
Impact of Piping Coil
How will this affect needed CHW flow?
What about the chiller performance?
Plumbing Arrangement
in Building’s Hydronic Systems
Radiators
Baseboard heaters
Fan coil systems
What is the difference between
these two configuration?
Hydronic Terms
• Head loss
• Open-loop vs. closed loop
•
Open System
h
Pump
•
Closed System
Chiller
Pump
Cooling coil in AHU
Is this open or closed system ?
Cooling towers
Relationship between velocity in a pipe
and pressure drop
Δp ~ v2
Δp = Constant × v2
Required power (P) for the pump
P = V × Δp
Δp [Pa or ft water]
smaller pipe
larger pipe
P –power [W],
V –volume flow rate [m3/s],
Δp – pressure drop [Pa]
v – velocity [m/s]
Δp ~ v2 (Δp ~ V2 – when same pipe is used)
P ~ V × V2 – when same pipe is used
P ~ V3
P2/P1 = (V2/V1)3 For the same pipe
When different pipe is used for the same flow rate:
For the same
flow rate V
Reduction of D:
D1
A1
V1
P1
D2= D1/2
A2=1/22 A1
V2=22 V1
P2/P1 = (D1/D2)4 - for the same flow rate
or 50% smaller diameter of the pipe
v [m/s or fpm]
for the same flow rate wee have:
4 times larger velocity
16 times larger pressure drop and
16 times lager power for the pump
Head Loss
Fittings
2
V
h  k
2g
Pumps
• Raise pressure and produce flow
• Main type
• Centrifugal
Example of
Turbine pump
Inline
Reading (textbook)
Page 3-36 - 3-45
Base mounted
Pump curves
• NPSHR = Net Positive Suction Head Required
Changing Pump Speed
Net Positive Suction Head
(cavitation)
Curve for Multiple Pumps
System Curves
∆p
A
∆p
A+B
B
A+B
A
B
V
A
B
V
Parallel
A
B
Serial
Find a system curve for this
plumbing configuration
System balancing
AHU1
AHU2
HC1
HC2
100 ft
1000 ft
10 gpm
2 gpm
10 ft
pump
BOILER
Valves
• Section 5-14 and 6-15 in the textbook
• Types
• Butterfly Valves
• Ball Valves
• Globe Valves
Three way valves
Valve Sizing and Flow Coefficient
Cv value:
in liter/hour or….
in Pa
Control Valve Selection For Hydronic Systems
reference:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=
8&ved=0CCUQFjAA&url=http%3A%2F%2Fbookstore.ashrae.biz%2Fjournal%2Fdow
nload.php%3Ffile%3Dhegberg.pdf&ei=IvcqU_O1KMuE2AWgloHgDA&usg=AFQjCNF
RAMzPnbzDpAluhyk4l8u_SKKTdw
Control Valve Selection For
Hydronic Systems
Before DC we tried to do this
Valve authority