Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Waterside energy-recovery hourlong-chicago_ashrae

0 views

Published on

Published in: Education, Business

Waterside energy-recovery hourlong-chicago_ashrae

  1. 1. WatersideEnergy RecoveryRequirements, Design andApplication Mick Schwedler, PE manager Trane applications engineering © 2011 Ingersoll Rand
  2. 2. reasons to useEnergy Recovery Required by code or standard Availability of simultaneous heating and cooling loads Economically justified  Reduces heating load  Reduces ancillary power Environmentally responsible  Reduces emissions  Eligible for “green” benefits (energy, water usage)
  3. 3. ASHRAE 90.1-2010 (since 1999)Waterside Energy RecoveryIF … Facility operates 24 hours per day  Heat rejection exceeds 6 million Btu/hr (~ 450 tons)  Design service water heating load exceeds 1 million Btu/hrTHEN Required energy recovery is (smaller of):  60% of design heat rejection  Preheating water to 85°F
  4. 4. types ofHeat-Recovery Chillers Single condenser (“bundle”) Dual condenser heat- standard  Equally sized condenser = recovery condenser bundles Auxiliary condenser heat-  Unequally sized standard condenser > recovery condenser bundles
  5. 5. heat-recovery chillersSingle Condenserhelical-rotary (screw)compressor scroll compressor centrifugal compressor
  6. 6. heat-recovery chillersDual Condenserheat-recovery leaving capacity chillercondenser water control? efficiencyFull capacity hot yes decreasesPartial capacity warm no increases heat-recovery condenser standard condenser evaporator water-cooled chiller with centrifugal compressor
  7. 7. heat-recovery chillersComparison of Options Chiller condenser optionCharacteristic Dual Auxiliary “Heat pump”Configuration Second, Second, No extra full-size smaller condenser condenser condenserApplication Large Preheating Large base- heating loads heating loads loads or continuous operationLeaving water Hot Warm HotCapacity control? Yes No YesChiller efficiency Decreases Increases Acceptable
  8. 8. variable air volumeTempering Supply AirWhen required supply/primary airflow isless than minimum setting:  Reduce primary airflow to minimum  Let space temperature drift downward  Add heat to avoid overcooling 105°F (40.6°C) water often is sufficient Supply air is always dehumidified
  9. 9. waterside heat recoveryTemperaturesService-water 85°F to 95°Fpreheating (29.4°C to 35°C)Space heating 105°F to 110F (40.6°C to 43.3C) source: 2008 ASHRAE Systems and Equipment Handbook
  10. 10. tempering VAV supply airHeating Coil Selectionselection parameter 1-row coil 2-row coilEntering water 113°F 105°FCoil flow rate 4.33 gpm 1.75 gpmFluid delta-T 6.02°F 14.91°FCoil fluid pressure drop 10.3 ft H2O 0.21 ft H2OAir pressure drop: design cooling airflow 0.45 in. wg 0.79 in. wg minimum airflow (est) 0.04 in. wg 0.07 in. wgLeaving-coil (primary) air 75°F 75°F Effectively balances heat-recovery temperatures and system pressure drops
  11. 11. waterside heat recoveryEffect on Chillers Compressor work is proportional to lift  “Lift” is pressure difference between evaporator and condenser  Warmer condenser water (for heat recovery) raises condenser pressure Changes in lift affect different compressors differently  Positive displacement  Centrifugal (full load vs. part load)
  12. 12. positive-displacement water chillerRefrigeration Cycle heat recovery 5 condenser 2 4 3 pressure expansion liquid/vapor compressor device separator 7 1 evaporator 6 enthalpy
  13. 13. positive-displacement water chiller Capacity 100 compressor type: 80 scrollchiller capacity, % screw 60 40 20 0 0° 10° 20° 30° 40° temperature rise (leaving-condenser water)
  14. 14. positive-displacement water chiller Efficiency 100 compressor type:power increase, % kW/ton 80 scroll screw (S) screw (M) 60 screw (L) 40 20 0 0° 10° 20° 30° 40° temperature rise (leaving-condenser water)
  15. 15. centrifugal chiller performance Power Increase Heat recovery 40 Chiller 85-105 F 32power increase, % kW/ton impeller diameter, inches compressor change 30 30 power increase 20 28 10 impeller diameter 0 26 85 87 89 91 93 95 97 99 condenser water temperature, °F
  16. 16. centrifugal chiller comparisonEfficiency Operating modeChiller type Cooling Heat recoveryCooling only 0.57 kW/ton Not applicable (6.2 COP)Heat recovery 0.60 kW/ton 0.69 kW/ton (5.9 COP) (5.1 COP) Entering to leaving water temperatures:Evaporator 54°F to 44°F 54°F to 44°F (12.2°C to 6.7°C) (12.2°C to 6.7°C)Condenser 85°F to 95°F 85°F to 105°F (29.4°C to 35.0°C) (29.4°C to 40.6°C)
  17. 17. heat-recovery chiller controlCondensing Temperature unloading with constant % maximum pressure differential leaving hot-water temperature C A unloading with constant B entering hot-water temperature % load
  18. 18. heat-recovery chiller controlCondensing TemperatureCompressor type Acceptable basis of controlPositive displacement Entering-condenser water temperature Leaving-condenser water temperature • Provides less capacity • Uses more powerCentrifugal Entering-condenser water temperature • Reduces likelihood of surge
  19. 19. Energy Recovery Topics Airside  Waterside  Outdoor air  Requirements  Types  Types  Requirements  Operation  System configurations  Supply air tempering  Operation  Requirements  Operation
  20. 20. system configurationPrimary–Secondary Available heat off = 150 × (52.6 – 40) 52.6°F 40°F = 1890 MBh Auxiliary heat required 750 gpm = 2000 – 1890 52.6°F 40°F = 110 MBh heat-recovery 300 gpm chiller production52.6°F (supply) 40°F distribution 225 gpm (demand) 40°F56°F 825 gpm
  21. 21. system configurationPreferential Loading Available heat off = 150 × (56 – 40) 51.2°F 40°F = 2400 MBh Rejected heat 750 gpm = 2400 – 2000 production51.2°F (supply) = 400 MBh 40°F525 gpm distribution 225 gpm (demand) 56.0°F 40°F heat-recovery 300 gpm chiller 40°F56°F 825 gpm
  22. 22. system configurationsSidestream Loading off Available heat = 150 × (56 – 42.7) 50.2°F 40°F = 2000 MBh 900 gpm production No rejected heat50.2°F (supply) No auxiliary heat51.2°F 40°F distribution 75 gpm (demand) 42.7°F 56°F heat-recovery 300 gpm chiller 40°F56°F 825 gpm
  23. 23. system configurationsSidestream LoadingControl strategies:  Satisfy heating requirements  Maintain leaving-condenser water temperature (positive-displacement compressors)
  24. 24. system configuration comparisonHeat Available/Required System configuration Primary–Characteristic secondary Preferential SidestreamCooling load:cooling-only units 393 tons 350 tons 383 tonsheat-recovery unit 157 tons 200 tons 167 tonsHeat-recovery 40°F 40°F 42.7°Fsupply temperatureAvailable heat 1890 MBh 2400 MBh 2000 MBhAuxiliary heat 110 MBh –400 MBh* 0 MBhrequired*Surplus recovered heat must be rejected
  25. 25. system configurations Variable Primary Flow Piping heat-recovery chiller in sidestream position may simplify control bypass line modulating control valveVFD for minimum chiller flow heat-recovery chiller control valve
  26. 26. system configurationsDistributed SidestreamTypical application:  Remote heating requirement  Chilled water load  Small chiller (or water-to-water heat pump) heating load heat-recovery chiller chilled water supply or return
  27. 27. airside system options Load-shedding economizer heat-recovery chiller heating load chilled water supply or return Control cooling load so heat rejection equals heating loadoutdoor-air controllertemperature sensor
  28. 28. airside system optionsLoading chiller withexhaust airstream Water from chiller Water to chiller EA RA C EA space T H T C HOA MA CA SA
  29. 29. single condenserHeat-Recovery Control controller V1 cooling tower heating T1 load V2 heat condenser exchanger P P water-cooled T2 chiller controller P evaporator cooling load
  30. 30. Dual-Condenser Chillersheat-recoverycondenserstandardcondenserpiped to cooling tower centrifugal heat-recovery chiller
  31. 31. dual condenserHeat-Recovery Controlcontroller cooling T2 tower P heating V2 controller load standard condenser T1 heat- P recovery P condenser auxiliary water-cooled heat P evaporator chiller Control based on entering-condenser water temperature cooling load
  32. 32. Analysis Toolstool applicationSystem Analyzer™ High-level scoping (< 1 hr)TRACE™ Chiller Plant Simplified building entriesAnalyzer Full analysis of chilled water plant, economic ratesEnergyPlus, HAP, TRACE Full energy simulation Hour-by-hour calculations of energy consumption, power demand, related costs
  33. 33. Waterside EnergyRecovery Steps Simultaneous heating  Place the chiller(s) in and cooling loads the appropriate system location Chiller HR capacity = Design heat recovery  Design the system with load the proper connections and controls Select lowest temperature that  Train the building meets requirements operators Select the proper  Operate the system chiller type properly Analyze the system
  34. 34. waterside heat recoveryReferencesFrom Trane: Waterside Heat Recovery in HVAC Systems SYS-APM005-EN 1991 Engineers Newsletter: “Two Good Old Ideas Combine to Form One New Great Idea” http://www.trane.com/commercial/library/EN20-1.pdfBy others: 2008 ASHRAE Handbook: HVAC Systems and Equipment chapter 8 2003 ASHRAE Journal: “Energy Efficiency for Semiconductor Manufacturing Facilities” Ralph M. Cohen, PE (August issue)
  35. 35. waterside heat recoveryReferences2008 ASHRAE Handbook: HVAC Systems and Equipmentchapter 82003 ASHRAE Journal: “Energy Efficiency for SemiconductorManufacturing Facilities”Ralph M. Cohen, PE (August issue)

×