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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