Lecture Objectives: Learn about Pumps and System Curves

Hydronic Terms Head loss Open-loop vs. closed loop Open System Closed System h Pump Chiller Cooling coil in AHU Pump

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 P –power [W], V –volume flow rate [m3/s], v – velocity [m/s] Δp – pressure drop [Pa] 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: smaller pipe larger pipe Δp [Pa or ft water] D1 D2= D1/2 A1 V1 P1 A2=1/22 A1 V2=22 V1 P2/P1 = (D1/D2)4 - for the same flow rate or 50% smaller diameter of the pipe for the same flow rate wee have: 4 times larger velocity 16 times larger pressure drop and 16 times lager power for the pump v [m/s or fpm]

Head Loss

Fittings

Pumps Raise pressure and produce flow Main type Centrifugal Example of Turbine pump Base mounted Inline Reading (textbook) Page 3-36 - 3-45

Pump curves NPSHR = Net Positive Suction Head Required

Changing Pump Speed

Net Positive Suction Head (cavitation)

Curve for Multiple Pumps

System Curves ∆p ∆p A+B A B A+B A B V A B V A B Parallel Serial

Find a system curve for this plumbing configuration

Primary/Secondary and Tertiary Pumping (schematics A&B below)

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%2Fdownload.php%3Ffile%3Dhegberg.pdf&ei=IvcqU_O1KMuE2AWgloHgDA&usg=AFQjCNFRAMzPnbzDpAluhyk4l8u_SKKTdw

Control Valve Selection For Hydronic Systems We tried to do this: Valve authority

HW2 40 ft 20 ft 20 ft 5 ft 200 ft 30 ft 30 ft 200 ft 40 ft 10 ton