Lecture Objectives: Learn about Pumps and System Curves
Hydronic Terms Head loss Open-loop vs. closed loop Open System Closed System Pump h Cooling coil in AHU Chiller Pump
Is this open or closed system ? Cooling towers
Relationship between velocity in a pipe and pressure drop Δp ~ v 2 Δp = Constant × v 2 Δp [Pa or ft water ] v [m/s or fpm] larger pipe smaller pipe Required power (P) for the pump P = V × Δp P –power [W], V –volume flow rate [m 3 /s], v – velocity [m/s] Δp – pressure drop [Pa] Δp ~ v 2 (Δp ~ V 2 – when same pipe is used ) P ~ V × V 2 – when same pipe is used P ~ V 3 P 2 /P 1 = (V 2 /V 1 ) 3 For the same pipe When different pipe is used for the same flow rate: For the same flow rate V Reduction of D: D1D1 D 2 = D 1 /2 A 1 V 1 P 1 A 2 =1/2 2 A 1 V 2 =2 2 V 1 P 2 /P 1 = (D 1 /D 2 ) 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
Head Loss
Fittings
Pumps Raise pressure and produce flow Main type Centrifugal Inline Base mounted Example of Turbine pump Reading (textbook) Page
Pump curves NPSHR = Net Positive Suction Head Required
Changing Pump Speed
Net Positive Suction Head (cavitation)
Curve for Multiple Pumps
System Curves A B ∆p V A+B Parallel A B A B ∆p V A+B A B Serial
Find a system curve for this plumbing configuration
Primary/Secondary and Tertiary Pumping (schematics A&B below)
System balancing BOILER HC2 AHU1 AHU2 HC1 pump 100 ft 1000 ft 2 gpm 10 gpm 10 ft
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: 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