Presentation on theme: "How to Convert and Optimize Primary/Secondary Pumping Systems"— Presentation transcript:
1How to Convert and Optimize Primary/Secondary Pumping Systems to Variable Flow Primary SystemsPresented By: Hemant Mehta, P.E.WMGroup Engineers, P.C.
2History of Variable Primary Flow Projects King Saud University - Riyadh (1977)Louisville Medical Center (1984)Yale University(1988)Harvard University (1990)MIT(1993)Amgen (2001)New York-Presbyterian Hospital (2002)Pennsylvania State Capitol Complex (2005)Duke University (2006)NYU Medical Center (2007)Memorial Sloan-Kettering Cancer Center (2007)
3King Saud University – Riyadh (1977) 60,000 ton capacity with 30,000 tons for first phaseSix 5,000 ton Carrier DA chillersSeven 10,000 GPM 240 TDH constant speed pumpsMajor Problem: Too much head on chilled water pumpsLesson Learned: Be realistic in predicting growth
4Louisville Medical Center (1984) Existing system (1984)Primary/Secondary/Tertiary with 13,000 ton capacityCurrent System (2007)120 feet TDH constant speed primary pumps with building booster pumps – 30,000 ton capacityChanged the heads on some of the evaporator shells to change number of passesPrimary pumps are turned OFF during winter, Early Spring and Late Fall. Building booster pumps are operated to maintain flow.
5Yale University (1988) Existing system (1988) Primary/Secondary/Tertiary with 10,500 ton capacityCurrent System (2007)180 feet TDH VFD / Steam Turbine driven variable flow primary pumps – 25,000 ton capacityChanged the heads on some of the evaporator shells to change number of passes
6Amgen (2001)Creation of a computerized hydraulic model of the existing chilled water plant and distribution systemIdentification of bottlenecks in system flowEvaluation of existing capacity for present and future loadsTwo plants interconnected: Single plant operation for most of the year, second plant used for peakingAnnual Energy Cost Savings: $500,000
7Additional Variable Primary Flow Projects Harvard University (1990)MIT(1993)New York-Presbyterian Hospital (2002)Pennsylvania State Capitol Complex (2005)Duke University (2006)NYU Medical Center (2007)Memorial Sloan-Kettering Cancer Center (2007)
8Duke University Background CCWP-1 plant was built four years agoCCWP-2 design was 90% complete (Primary/Secondary pumping)We were retained by Duke to peer review the designPeer review was time sensitivePlant design for CCWP-2 was modified to Variable Primary pumping based on our recommendations
12Duke CIEMAS Building CHW System 90% closedTriple duty valves50% closed
13Duke CIEMAS Building AHU-9 Balancing valve50% closed
14NYU Medical Center (2007)Plant survey and hydraulic model indicated unnecessary pumps1,300 horsepower of pumps are being removed, including 11 pumps in two brand new chiller plants$300,000 implementation cost$460,000 annual energy savings
15NYU Medical Center (2007)Plant survey and hydraulic model indicated unnecessary pumps1,300 horsepower of pumps are being removed, including 11 pumps in two brand new chiller plants$300,000 implementation cost$460,000 annual energy savings8 Pumps Removed3 Pumps Removed7 Pumps Removed3 Pumps Removed
17Memorial Sloan-Kettering - After Bypass or removal of pumpsBypass or removal of pumpBypass or removal of pumps
18Pump CemeteryTo date we have removed several hundred large pumps from our clients’ chilled water systems
19Good Engineers Always Ask “Why?” Why does the industry keep installing Primary/Secondary systems?Why don’t we get the desired system ΔT?Why does the industry allow mixing of supply and return water?
20Good Engineers Always Ask “Why?” Why does the industry keep installing Primary/Secondary systems?Why don’t we get the desired system ΔT?Why does the industry allow mixing of supply and return water?Answer: To keep consultants like us busy!Why change?
21Reasons to ChangeChiller manufacturing industry supports the concepts of Variable Primary FlowEvaporator flow can vary over a large rangeLess space is required for fewer pumpsLower first cost and operating costs
22Change is Starting Around the World Most of the large district cooling plants in Dubai currently use Primary/Secondary pumpingBy educating the client we were able to convince them that this is not necessaryWe are now currently designing three 40,000 ton chiller plants in Abu Dhabi using Variable Primary Flow as part of a $6.9 billion development project
23Design Guidelines of A Primary Variable Flow System Main EquipmentMinimize amount of installed equipmentEstimate maximum chiller capacity required with full build-out of your campusUse 350 SF/Ton as a guideline for most building typesMultiple Plants/ Virtual Central SystemReview your existing system and decide your needs for ultimate build-out
24Design Guidelines of A Primary Variable Flow System ChillersRenegotiate with manufacturer to provide maximum capacity based on the chiller selection.Keep flow velocity around 6.5 ft/sec at peakChilled Water PumpsVariable Frequency DriveReview feasibility of oversizing pumps in lieu of providing a standby pump
25Design Guidelines of A Primary Variable Flow System Condenser Water PumpsVariable Speed Condenser Water Pumps?Cooling TowersDesign for at least 2°F higher wet bulb temperature than normal design wet bulbSpecify full flow coverage at 50% of peak flowPressurization TankCity water pressure may be adequateTank May not be required for large systemAir SeparatorsNot required
26Design Guidelines of A Primary Variable Flow System ControlsFlow control valves on CHWR and CWR lines to each chillerChilled water differential pressure bypass valve at the plantDifferential pressure sensors at the hydraulically most remote buildingsFlow meters on CHWR and CWR lines to each chillerOutside air weather stationTemperature and humidity sensors for cooling tower controlsLearn the behavior of your systemRememberYou can not manage what you do not measure
27Design Guidelines of A Primary Variable Flow System Chilled water flow controls and site differential pressureMaster ControlCHWP VFD is controlled to maintain required differential pressure at remote buildingsSub Master ControlProvide to maintain individual chiller minimum flow
29Variable Volume Primary System Flow Diagram Chillers
30Variable Volume Primary System Flow Diagram CHW Pumps
31Variable Volume Primary System Flow Diagram DP Bypass
32Variable Volume Primary System Flow Diagram Condensers
33Variable Volume Primary System Flow Diagram Control Valves
34Variable Volume Primary System Flow Diagram CW Pumps
35Variable Volume Primary System Flow Diagram Cooling Towers
36SummaryThere are many chilled water plants with significant opportunities for improvementWM Group has a proven record of providing smart solutions that workWe will be happy to review your plant logs with no obligation1985: $ 0.171/ton-hr2002: $0.096/ton-hr
37Thank You WMGroup Engineers, P.C. Hemant Mehta, P.E. President (646)