Technical Development Program

Transcription

1 Technical Development Program COMMERCIAL HVAC CHILLER EQUIPMENT Water-Cooled Chillers PRESENTED BY: Omar Rojas Sales Engineer

2 Menu Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Section 7 Section 8 Section 9 Section 10 Section 11 Section 12 Introduction Basic Refrigeration Cycle Chiller Components Chiller Controls Screw Compressor Operational Details Centrifugal Compressor Operational Details Capacity Control Methods Refrigerant Related Topics Heat Transfer Codes and Standards Selection Criteria Summary

3 SECTION 1 WATER-COOLED CHILLERS Introduction

4 Objectives Compare the advantages of water-cooled versus air-cooled chillers Identify and diagram the different components of a basic refrigeration cycle as it applies to a water-cooled chiller Compare and describe the differences among scroll, reciprocating, centrifugal, and screw water-cooled chillers and their applications Discuss the differences in construction of water-cooled chillers of various sizes Identify the codes and standards that apply to water-cooled chillers Understand the typical inputs required to select a water-cooled chiller Section 1 Introduction

5 Dr. Willis H. Carrier In the early 1900 s, centrifugal air compressors were adopted for use in the air conditioning industry. Section 1 Introduction

6 Early Centrifugal Chiller Section 1 Introduction

7 Smithsonian Institute Carrier Centrifugal Chiller on Display Section 1 Introduction

8 Evolution of Centrifugal Chillers Section 1 Introduction

9 Water-Cooled vs. Air-Cooled Chillers Section 1 Introduction

10 Typical Water-Cooled Chiller System Water-cooled packaged chillers are available up to about 3000 tons of capacity. Water-Cooled Condenser Chiller Condenser Water Pump Cooling Tower Section 1 Introduction

11 SECTION 2 WATER-COOLED CHILLERS Basic Refrigeration Cycle

12 Basic Refrigeration Cycle Condenser Pressure Reducing Device Compressor Water Nozzles Hot Gas Discharge Line 95 F 85 F Liquid Line Suction Line 44 F 54 F Evaporator Section 2 Basic Refrigeration Cycle

13 Basic Refrigeration Cycle Section 2 Basic Refrigeration Cycle

14 Pressure-Enthalpy Diagram Refrigeration Cycle P c PRESSURE P s Saturated Condensing Saturated Suction LIFT RE ENTHALPY Section 2 Basic Refrigeration Cycle

15 Refrigeration Cycle with Subcooling P c SUBCOOLING tc PRESSURE P s ts Vgs h fc RE ENTHALPY h gs Section 2 Basic Refrigeration Cycle

16 Water-Cooled Condenser Subcooler Condenser tubes Orifices in subcooler Condenser shell Subcooler box at the bottom of the condenser Float valve metering device Section 2 Basic Refrigeration Cycle

17 Refrigeration Cycle with Economizer 2-Stage Centrifugal Shown PRESSURE P c P e P 2 P s RE h fe h fc h gs h ge h 3 ENTHALPY Section 2 Basic Refrigeration Cycle

18 SECTION 3 WATER-COOLED CHILLERS Chiller Components

19 Brazed-Plate Evaporator Note: Brazed-plate heat exchangers are also used as condensers Return water in 54º F Refrigerant out Refrigerant in Chilled water out 44º F Section 3 Chiller Components

20 Direct Expansion Evaporator Water Out Water In Refrigerant is in the tubes Water is in the shell Section 3 Chiller Components

21 Flooded Shell-and-Tube Evaporator Tubes penetrating end of tube sheet Refrigerant Suction Flange Waterbox Ring End Tube Sheet Section 3 Chiller Components

22 Flooded Shell-and-Tube Evaporator Refrigerant Suction Outlet Water in tubes Water Nozzles Tube Support Sheets Liquid refrigerant floods the shell around the tubes. Section 3 Chiller Components

23 Evaporator Refrigerant Path Waterbox Nozzles Refrigerant Distribution System Gaseous Refrigerant Suction Gas to Compressor Liquid Refrigerant Liquid Refrigerant from Condenser Section 3 Chiller Components

24 Space Elimination Free space for gaseous refrigerant Liquid refrigerant rises to top-most tube level. Tube Support Sheets Liquid Refrigerant Distribution Box Section 3 Chiller Components

25 End Tube Support Sheet Double Grooves Section 3 Chiller Components

26 Parallel and Series Evaporators Section 3 Chiller Components

27 Large Chiller Shell-and-Tube Condenser Hot Gas Inlet Subcooler Circuit Float Valve Chamber Waterbox Ring End Tube Support Sheet Section 3 Chiller Components

28 Large Chiller Condenser Cutaway Hot Gas Inlet Orifice Tubes Float Valve Chamber Liquid Outlet Tube Support Sheets Subcooler Section 3 Chiller Components

29 Condenser Refrigerant Path Hot Refrigerant Vapor Inlet Return to Cooling Tower Water From Cooling Tower Liquid Refrigerant Outlet Section 3 Chiller Components

30 Compressors Two Categories: - Positive Displacement - Dynamic Compression (Centrifugal) Section 3 Chiller Components

31 Reciprocating Compressor Cylinder Head Terminal Box Multi-Compressor Reciprocating Chiller Motor Semi-Hermetic Compressor Section 3 Chiller Components

32 Reciprocating Compressor Section 3 Chiller Components

33 Scroll Compressor Electrical Terminal Connection Pressure Relief Hot Gas Discharge Orbiting Scrolls Hermetic Shell Suction Inlet Hermetic Motor Section 3 Chiller Components

34 Scroll Compressor Section 3 Chiller Components

35 Screw Compressor 2-Circuit Screw Chiller Evaporator Screw Compressor Condenser Section 3 Chiller Components

36 Double Rotor Screw Compressor Section 3 Chiller Components

37 Centrifugal Compressor Transmission Motor Rotor Refrigerant Motor Cooling Line Guide Vane Motor Hermetic Drive Inlet Guide Vanes Impeller Open Drive Section 3 Chiller Components

38 Centrifugal Compressor Need Avi file Section 3 Chiller Components

39 Hermetic Centrifugal Compressor Refrigerant Cooling Transmission High Speed Shaft Impeller Hermetic Housing Electric Motor Rotor Low Speed Shaft Inlet Guide Vanes Oil Filter Oil Pump Section 3 Chiller Components

40 Open Drive Centrifugal Compressor Drive Shaft Section 3 Chiller Components

41 Refrigerant Metering Large Chiller Hot Gas Inlet Condenser Condenser Tubes Liquid Refrigerant Float Valve Open Liquid Outlet Section 3 Chiller Components

42 Nozzle-in-Head Waterboxes Waterbox Assembly Dished Head Design Nozzles Section 3 Chiller Components

43 Marine Waterboxes 1 or 3-Pass Marine Waterbox Outlet Nozzles Outlet CONDENSER 2-Pass Marine Waterbox Inlet Hinged Water Box Covers EVAPORATOR Section 3 Chiller Components

44 Purge Unit Purge Unit Negative Pressure Centrifugal Chiller Section 3 Chiller Components

45 Positive Pressure Chiller/Transfer Compressor Section 3 Chiller Components

46 Storage Tank and Transfer Unit This assembly is required when using a chiller design where in-chiller storage of refrigerant is not available. Tank-Mounted Transfer Compressor Refrigerant Storage Tank Section 3 Chiller Components

47 Relief Valves Reseating Type Relief Valves on Positive Pressure Centrifugal Chiller Rupture Disk Relief on Negative Pressure Centrifugal Chiller Section 3 Chiller Components

48 SECTION 4 WATER-COOLED CHILLERS Chiller Controls

49 Centrifugal Chiller Control Panel Unit-Mounted Control Panel RUNNING TEMP CONTROL LEAVING CHILLED WATER : HOURS CHW IN 55.1 CDW IN 85.0 OIL PRESS 21.8 CHW OUT 44.1 CDW OUT 95.0 OIL TEMP EVAP REF 40.7 COND REF 98.1 MTR AMPS 93 CCN LOCAL RESET MENU Includes visual display/user interface Monitors and controls the chiller and auxiliary devices such as pumps Provides BAS communication functions Section 4 Chiller Controls

50 Chiller Starting Methods Across-the-Line Auto Transformer* Primary Reactor* Part-Winding* Wye-Delta* Solid State* Variable Frequency Drive * Soft Start Softest Start Section 4 Chiller Controls

51 Unit-Mounted Solid State Starter Section 4 Chiller Controls

52 VFD Starter for Unit-Mounting Section 4 Chiller Controls

53 Motor Starting Current Information Starting Method Motor Starting Current as a % of Locked Rotor Current Full Load Current Across-the-Line Auto Transformer & Primary Reactor 80% 65% 50% Part Winding Wye-Delta Solid-State VFD Section 4 Chiller Controls

54 SECTION 5 WATER-COOLED CHILLERS Screw Compressor Operational Details

55 Screw Chiller Technology Rotors Transmission Section 5 Screw Compressor Operational Details Large Screw Chiller Compressor

56 SECTION 6 WATER-COOLED CHILLERS Centrifugal Compressor Operational Details

57 Centrifugal Compressor Theory Heavier the ball (molecular weight) = MORE FORCE Longer the string (diameter) = MORE FORCE Faster the ball rotates (rpm) = MORE FORCE FORCE FORCE BALL GAS MOLECULE LENGTH DIAMETER STRING Section 6 Centrifugal Compressor Operational Details

58 Centrifugal Compressor Theory Section 6 Centrifugal Compressor Operational Details

59 Centrifugal Principle Section 6 Centrifugal Compressor Operational Details

60 Centrifugal Principle Section 6 Centrifugal Compressor Operational Details

61 Centrifugal Head P S Suction (inlet) pressure VAPOR HEAD FEET Head can be pictured as the height of a column of refrigerant vapor which, due to its weight, produces the same pressure as that developed across the compressor. P D Section 6 Centrifugal Compressor Operational Details Discharge (outlet) pressure

62 Lift Lift = SCT less SST 95F 85F Saturated temperatures are surrogates for pressures To condense, refrigerant must be warmer than the leaving condenser water. SCT = 95F + 2F approach = 97F To boil, refrigerant must be 44F colder than the leaving 54F 44F chilled water. SST = 44F 2F approach = 42F Lift is Based On Leaving

63 Lift Sat. Condensing = 97 F PRESSURE Sat. Suction = 42 F Lift 55 F ENTHALPY Section 6 Centrifugal Compressor Operational Details

64 Lift Like pumps, chiller energy consumption is a function of mass flow and differential pressure. Compressor Input kw ~ Mass Flow X Lift Compressor/Cycle Efficiency Chiller Cooling Tower CHILLER ENERGY (KW) ~ TONS X LIFT

65 Lift Reduction PRESSURE Sat. Condensing = 97 F Sat. Condensing = 77 F Lift = 35 F Sat. Suction = 42 F Lift 55 F ENTHALPY Section 6 Centrifugal Compressor Operational Details

66 Centrifugal Compressor Map 25% 50% 75% 100% Head Factor Load line plotted on compressor map Stone Wall Flow Factor Section 6 Centrifugal Compressor Operational Details

67 Centrifugal Compressor Stages Earlier Multi-Stage Design Single-Stage Design (one impeller) Section 6 Centrifugal Compressor Operational Details

68 SECTION 7 WATER-COOLED CHILLERS Capacity Control Methods

69 Centrifugal Chiller Capacity Control - IGV Guide Vane Motor Inlet Guide Vanes Inlet Shroud Impeller Section 7 Capacity Control Methods

70 Capacity Control - IGV Inlet Guide Vanes Closed Section 7 Capacity Control Methods

71 Centrifugal Compressor Efficiency Characteristics Constant Speed Centrifugal Efficiency 70% 80% 90% Lift 60% Open Vanes 50% Vanes 25% Vanes 10% Vanes Capacity (Tons) Section 7 Capacity Control Methods

72 Screw Capacity Control Methods SLIDE VALVE METHOD Infinite Capacity Control PORT VALVE METHOD Stepped Capacity Control Slide Valve Step Valves Section 7 Capacity Control Methods

73 Affinity Laws for Centrifugal Loads Flow ~ Speed Lift ~ Speed 2 Power ~ Speed 3 % Flow % Pressure/Head % Input Power % rpm % rpm % rpm Section 7 Capacity Control Methods

74 VFD Saves Energy Constant Speed kw/ton VFD kw/ton kw / ton % 30% 40% 50% 60% 70% 80% 90% 100% Percent Full Load Tons Typical 500-Ton Centrifugal Chiller Section 7 Capacity Control Methods

75 Centrifugal Compressor Efficiency Characteristics Variable Speed Centrifugal New operating characteristics created by speed reduction Lift 100% 80% Efficiency 90% 100% 90 % 70% 60% Speed Capacity (Tons) Section 7 Capacity Control Methods

76 SECTION 8 WATER-COOLED CHILLERS Refrigerant Related Topics

77 HCFC Phase Outs Production Cap 65% (1 Jan 2004) Current Montreal Protocol 35 % ( 2010) 10 % (2015) 0.5% (2020) No New R-22 No New R-123 Equipment Equipment Section 8 Refrigerant Related Topics

78 Chiller Construction Large R-134a chillers are constructed in accordance with ASME Section VIII, Division I Section 8 Refrigerant Related Topics

79 Chiller Size Refrigerant Impact Chiller size is affected by refrigerant molecular size. HFC 410A HCFC 22 HFC 134a HCFC 123 Section 8 Refrigerant Related Topics

80 Allowable Exposure Limits Exposure Limits HFC-134a 1000 ppm 50 ppm HCFC ppm Ammonia Safety Section 8 Refrigerant Related Topics

81 Refrigerant Safety Groups High Flammability A3 Propane B3 Low Flammability A2 R-142b, 152a B2 Ammonia No Flame Propagation A1 R-11, R-12, R-22, R-114, R-500, R-134a Lower Toxicity B1 R-123, SO 2 Higher Toxicity ASHRAE Standard 34 Section 8 Refrigerant Related Topics

82 SECTION 9 WATER-COOLED CHILLERS Heat Transfer

83 Heat Transfer - Condenser Temperature t" Refrigerant Temperature t R Dt Lvg t 2 Dt Ent t 1 t R The refrigerant is changing from a gas to a liquid and is releasing its latent heat of condensation Section 9 Heat Transfer

84 Heat Transfer - Evaporator Temperature t" t 1 Dt Ent t R Refrigerant Temperature Dt Lvg t 2 t R The refrigerant is changing from a liquid to a gas while absorbing its latent heat of vaporization Section 9 Heat Transfer

85 Chiller Equation for Tons tons = gpm * 24 D t F gpm = Flow rate for evaporator or condenser Dt F = Difference in fluid entering and leaving 24 = Conversion to tons for fresh water Section 9 Heat Transfer

86 Heat Transfer Overall Heat Transfer Exchanged q = U * A * LMTD LMTD Log Mean Temperature Difference = Log e D t æ ç è F D D t t Ent Lvg ö ø Heat Transfer Coefficient 1 / U = R W + R F + R M + R R Section 9 Heat Transfer

87 Overall Heat Transfer Saturated Condensing Temperature (t R ) Dt Ent HEAT OF CONDENSATION t 2 Dt Lvg t 1 t 1 Dt Ent HEAT OF VAPORIZATION t 2 Dt Lvg Saturated Suction Temperature (t R ) Section 9 Heat Transfer

88 Typical Resistances to Heat Transfer - Baseline HEAT TRANSFER RESISTANCES BETWEEN FLUID IN THE TUBES AND THE REFRIGERANT R W % Fluid Film R F % Fouling R M % Tube Material R R % Refrigerant Film R T % Total Section 9 Heat Transfer

89 Resistances with Increase in Fouling R W % Fluid Film R F % Fouling R M % Tube Material R R % Refrigerant Film R T % Total Section 9 Heat Transfer

90 Fouling (Scaling Resistance) R F Fouling is the build-up of deposits on tube surfaces and depends on the quality of water (i.e., dirty river, etc.) Expressed as a number ( or or 0.002) Minimal in evaporators Closed piping circuit Greater in condensers ARI fouling factor Basis of chiller ratings for condensers For evaporators Lower water velocities result in higher fouling rates Water Heat Flow Refrigerant Resistant Layers Water in Tube Water Film R W Scale (Fouling) R F Metal R M Refrigerant Film R R Section 9 Heat Transfer

91 Resistances With Lower Water Velocity in Tubes R W % Fluid Film (4 fps velocity) R F % R M % R R % R T % Section 9 Heat Transfer

92 Resistances With Tube Material Change R W % R F % R M % CuNi Tube Material R R % R T % Section 9 Heat Transfer

93 Evaporator Tubing Materials Chart Application Tubing Materials Chart Tube Material Approximate Cost Multiplier vs. Copper Tubes Fresh Water Copper 1.0 Glycols Copper 1.0 Corrosive Water Cupro-Nickel 1.3 Special Process Stainless Steel 2 to 3 Sea Water Titanium or Cupro-Nickel 3 to 4 Section 9 Heat Transfer

94 Shell-and-Tube Heat Exchanger Tubing INTERNALLY AND EXTERNALLY ENHANCED Evaporator Tubing Condenser Tubing Section 9 Heat Transfer

95 Pass Arrangements One-Pass AREA = A Low Pressure Drop, Low Rise Two-Pass AREA = A/2 Medium Pressure Drop, Medium Rise Three-Pass AREA = A/3 High Pressure Drop, High Rise Section 9 Heat Transfer

96 SECTION 10 WATER-COOLED CHILLERS Codes and Standards

97 ARI Weighting Factors Percent Chiller Load FOR IPLV CALCULATION Entering Condenser Temp Percent Weighting Section 10 Codes and Standards

98 ASHRAE 90.1 and T24 Standard WATER CHILLING PACKAGES-MINIMUM EFFICIENCY REQUIREMENTS *kw/ton = 3.516/COP Section 10 Codes and Standards

99 ASHRAE 90.1 and T24 Standard Adjustment Formula for Minimum Efficiency Standards IKW/TonRequired Condenser Delta T Section 10 Codes and Standards

100 ASHRAE Standard 15 Provide a mechanical room if the amount of refrigerant used exceeds ASHRAE 15 table values Terminate discharge lines away from air intakes Eliminate any passages allowing refrigerant to escape into the building Run piping from purge and rupture disk to outside Size relief lines per ASHRAE 15 Install dedicated mechanical room ventilation fan Use a tight fitting mechanical room door Store refrigerant in approved storage vessels only Install refrigerant leak detector interlocked to ventilation fan and alarm Restrict mechanical room access to authorized personnel Section 10 Codes and Standards

101 SECTION 11 WATER-COOLED CHILLERS Selection Criteria

102 Centrifugal Chiller Input Screen 1 Section 11 Selection Criteria

103 Centrifugal Chiller Input Screen 2 Section 11 Selection Criteria

104 SECTION 12 WATER-COOLED CHILLERS Summary

105 Summary Compared the advantages of water-cooled versus air-cooled chillers Identified and diagrammed the different components of a basic refrigeration cycle as it applies to a water-cooled chiller Compared and described the differences among scroll, reciprocating, centrifugal, and screw water-cooled chillers and their applications Discussed the differences in construction of water-cooled chillers of various sizes Identified the codes and standards that apply to water-cooled chillers Reviewed the typical inputs required to select a water-cooled chiller Section 12 Summary

106 Technical Development Program Thank You This completes the presentation.