Chilled Water System Presentation

Transcription

1 Chilled Water System Presentation

2 Constant Volume Distribution Constant Volume Distribution

3 Air-conditioning System Components

4 Constant Volume System Components

5 Typical 3-way Valve Zone

6 Full Load Condition

7 Fully Loaded Coil Supply water temperature 45 F Design return water temp. 55 F Coil design flow 100 GPM Coil design pressure drop 20 FT Load (flow x 10 F x 500) 500,000 Btuh Coil design flow 20 FT Bypass flow 0 GPM Bypass P 3-way valve closed 3-way valve pressure drop 10 FT Pump flow and head FT Actual return water temp 55 F

8 Unloaded Condition

9 Unloaded Coil Supply water temperature 45 F Design return water temp. 55 F Coil design flow 0 GPM Coil design pressure drop 3-way valve closed Load (flow x 10 F x 500) 0.0 Btuh Coil design flow 0 FT Bypass flow 100 GPM Bypass P 20 FT 3-way valve pressure drop 10 FT Pump flow and head FT Actual return water temp 45 F

10 So What? When the load on the coil is zero, the valve is returning unused chilled water at essentially supply temperature. Cold return water unloads the chillers, causing them to operate inefficiently.

11 Part Load Condition

12 Partially Loaded Coil Supply water temperature 45 F Design return water temp. 55 F Coil design flow 50 GPM Coil design pressure drop 20 FT Load (flow x 10 F x 500) 250,000 Btuh Coil design flow 5 FT Bypass flow??? GPM Bypass P 3-way partially closed 3-way valve pressure drop 10 FT Pump flow and head??? 30 FT Actual return water temp?? F

13 3-way Valve Characteristic 125 1/2 Through Coil 1/2 Through Bypass 100 % Flow Full Flow Through Coil Full Flow Through Bypass % Valve Stroke

14 What s Really Happening?

15 Coil with 3-way Valve at Mid-position Supply water temperature 45 F Design return water temp. 55 F Load (flow x 10 F x 500) 250,000 Btuh Coil design pressure drop 20 FT Coil flow 62.5 GPM Coil 62.5% flow 7.8 FT Coil leaving water temp 53 F Bypass flow 62.5 GPM Bypass P 7.8 FT 3-way valve pressure drop 10 FT Pump flow and head FT Actual return water temp 49 F ( F F)

16 Head 2 = Head 1 (Flow 2 / Flow 1 ) 2 Head 2 = 20(.625/1) 2 Head 2 = 20(.3906 ) Head 2 = 7.8

17 T = Load/ Flow X 500 T = 250,000/62.5 X 500 T = 8 Therefore, LWT coil = = 53

18 RWT = (Flow 1 X EWT + Flow 2 X LWT)/ Flow RWT = (62.5 X X 53)/125 RWT = 49

19 3-way Valve in Mid Position

20 3-way Valve System Deficiencies 1. Low return water temperatures. 2. Robs chilled water from other coils at part load conditions. 3. Increases flow in primary piping. 4. Adds additional chillers on line. 5. Chiller performance is reduced.

21 Chiller Performance Curve KW per Ton Percent Load

22 Pump Sizing Select for full chiller flow Head must be adequate for: Chiller evaporator Longest circuit Coil Three way valve Air separator

23 System Configuration Constant Volume

24 Any Questions?

25 Variable Volume Constant Speed

26 Variable Volume Constant Speed Primary Secondary System Primary Circuit Includes Chillers & Primary Pump. Constant water flow through the chiller is maintained and chilled water is produced Secondary Chilled water is circulated to the Circuit demand area (load) by using Secondary pumps.

27 PRIMARY - SECONDARY

28 Other Famous Names of Primary- Secondary Primary Production Loop Secondary Distribution Loop

29 Fundamental Idea

30 No Secondary Flow

31 Primary = Secondary

32 Primary > Secondary

33 Primary < Secondary

34 Control Valve in Secondary

35 Common Pipe Design Criteria Use the flow of the largest chiller Chiller staging at half of this flow is common Head loss in common <1 1/2 ft Distribution pipe size is often used where reductions would be inconvenient Three pipe diameters between tees Excessive length increases total head loss Low velocities in system piping

36 Control Valve in Secondary Variable flow through coil Constant flow through system Three Way Valve Variable flow through coil Variable flow through system Two Way Valve

37 Variable Volume Constant Speed PRIMARY SECONDARY CIRCUIT

38 Control Valves Change the Secondary System Curve H1 H2 H3 Head Flow F1 F2 F3

39 Head Absorbed by 2-way Valves 150 TDH of pump Pump curve HD Varying differential pressure absorbed by control valve System resistance % Flow

40 Pump Horsepower Comparison Constant Flow Primary Pumps, only HP Secondary Pumps + Primary Pumps = V/V % Design Flow

41 Constant vs Variable Volume Constant Flow, C/S Pump (3 Way Valve) Pump Over-haded by 150% C/S Pump (2 Way Valve) Base Design HP % % Full Load (Design) HP Constant Flow, C/S Pump (3 Way Valve) C/S Pump (2 Way Valve) Pump HD Matched to Design Flow % Flow

42 Any Questions?

43 Step Function of Chillers

44 Production = Distribution

45 Distribution > Production

46 Production > Distribution

47 Loading a Chiller A chiller is a heat transfer device. Like most equipment, it is most efficient at full load. To load a chiller means: Supply it with its rated flow of water Insure that water is warm enough to permit removal of rated Btu without freezing the water

48 Chiller Performance Curve 1.1 KW per Ton Percent Load

49 Check Valve in Common?

50 What can we do?

51 What else can we do? Reset Supply Temperature Lower chiller set point when mixing occurs to maintain a constant temperature to the system. Expect increases in cost of chiller operation at lower set point: 1-3% per degree of reset. Delays start of the next chiller.

52 What else can we do? Coils that are selected at higher supply temperatures will not be impaired by small changes. Loads that require fixed temperatures may use a small chiller to reverse the effects of mixing.

53 Multiple Chillers

54 60/40 Chiller Split to Help Minimize Low Part Load Operation

55 Typical Load Profile % Time % Load

56 Three Unequally Sized Chillers

57 Approaching Flow = Load % Load Time

58 Any Questions?Alternate Pumping Methods Comparison

59 Two Pipe Direct Return

60 Two Pipe Reverse Return

61 Primary-Secondary Pumping. Simplest to install. Simplest to operate. Flexible in design for present and future. Efficient to operate. May over-pressurize near zones.

62 Primary-Secondary-Tertiary

63 Primary-Secondary-Tertiary Pumping. Best piping flexibility. Best expansion flexibility. Provides hydraulic decoupling. Efficient to operate. May require added horsepower. Requires additional pumps and piping. Increased controls complexity.

64 Primary-Secondary-Tertiary Hybrid

65 Primary-Secondary-Tertiary Hybrid Pumping. Low present horsepower. Low future horsepower. Good piping flexibility. Good expansion flexibility. Provides hydraulic decoupling. May require added horsepower Requires additional pumps and piping. Increased controls complexity.

66 Primary-Secondary Zone Pumping

67 Primary-Secondary Zone Pumping. Low built out horsepower. Low system head. Increased control complexity. Present horsepower total higher due to future needs. Present pumps sized for future requirements. Difficult to apply in retrofits projects.

68 Any Questions?

69 Variable Volume Variable Speed

70 Why Do We Need Variable Speed Secondary Pumps??? For Energy Saving. For better & optimise operation.

71 How Do We Achieve This Reduction In Power Consumption?? By Using Variable Frequency Drive and Logic controller with the Secondary Pumps.

72 Power Comparison at Reduced Speed

73 Basic Law which helps in achieving this Affinity law 1. Flow 2 = Flow 1 (Speed 2 / Speed 1 ) 2. Head 2 = Head 1 (Speed 2 / Speed 1 ) 2 3. BKW 2 = BKW 1 (Speed 2 / Speed 1 ) 3 If Diameter of Impeller is to be trimmed then instead of speed the same can be used in above formulas.

74 Operating Cost Annual Operating Cost $ $0.10/kWh Motor Horsepower

75 Variable flow system Pump Curve System Curve as two way valves close Head System Curve Flow

76 Energy savings offset Pump Curve Increased head loss System Curve at part load System Curve at design flow H Q

77 Pumps in parallel Head Single Pump System Curve Pumps in Parallel Flow

78 Parallel pumping power savings Horsepower % Single Parallel Pump Single Large Pump Two Parallel Pumps Flow %

79 Theoretical Savings

80 Establishing Efficiency Curves 50 % 60 % 70 % 80 % % Efficiency 85 % 85 % 80 % 100 % 90 % Head, Feet 30 % 40 % 50% 60 % 70 % % Speed Curves 80 % Constant Efficiency Curve GPM

81 Variable Speed Efficiencies FT, 85.9 % 600 A B 1770 E D 600 C

82 No Valve System Curve Head Overall system curve 25 FT Differential Head Maintained Across Load (Set Point) Set Point Flow Distribution piping head loss curve Pump TDH

83 110 Effect of Constant Set Point 100 Head Overall system curve Control curve Distribution piping head loss curve Set point, 25 FT Pump TDH Flow

84 Control curve P1 P2 100% 75% Control Curve Head 50% P Variable Head Loss Flow

85 Large systems, long pipe runs Annual Operating Cost $0.10/kwh) Single C/S Pump, 200% Overheaded Single C/S Pump, No Overheading Variable Speed Pump Total Equivalent Pipe Length (feet)

86 Variable Head Loss Ratio Base C/S, Constant Flow System Pump Head Matched to System at Design Flow Percent Design BHP C/S, Variable Flow V/S, 0% Variable Hd Loss, 100% Constant Hd V/S, 25% Variable Hd Loss, 75% Constant Hd V/S, 50% Variable Hd Loss, 50% Constant Hd V/S, 75% Variable Hd Loss, 25% Constant Hd V/S, 100% Variable Hd Loss, 0% Constant Hd % Flow

87 Variable Head Ratio w/ Overheading Constant Flow, C/S Pump 150 Pump O Headed by 150% (3 Way Valve) C/S Pump (2 Way Valve) Base Design HP % % Full Load (Design) HP Constant Flow, C/S Pump (3 Way Valve) C/S Pump (2 Way Valve) V/S, 100% Constant HD V/S, 25/75* V/S, 50/50 V/S, 75/25 V/S, 100% Variable HD Pump HD Matched to Design Flow * 25/75 Means: 25 % Variable HD Loss 75 % Constant HD Loss

88 Locations of Sensor Where to install the Sensor? What type of Sensor?

89 Single Point Pressure Sensor Load Balancing Valve 2 Way Valve Chillers Single Point Pressure Sensing Panel with PLC & VFD`s Primary Pumps Common Secondary Pumps Air - Separator

90 Single Point Pressure Sensor Is Single Point Pressure Sensor Correct? Wrong!! Why? -Pump is a differential pressure device. -A single point is only influence by pressure. This is good for booster only. -In a closed loop system, system pressure rises due to thermal expansion, pumps will slow down. -When static pressure decrease, pumps will speed up. -This is self-defeating since now the pump speed is not influence by the system load changes, but rather by system water pressure. -Therefore, single pressure sensor are a misapplication in a closed loop HVAC system.

91 Single Point Differential Pressure Sensor Primary - Secondary Circuit With Variable Speed Secondary Pumps Load Balancing Valve DPT 2 Way Valve Chillers Panel with PLC & VFD`s Primary Pumps Common Secondary Pumps Air - Separator

92 Opening/Closing of 2- Way Valve -Signal from the sensor, installed at load regulates the valve opening & closing. -This way differential across 2-way valve also changes & accordingly output signal is given to PLC. 2 Way Valve Control Temperature Sensor Load ` ` Output to PFU from DPT `

93 Question: Can we put the DPT across coil alone?

94 Question: Across the pumps?

95 Single Point Differential Pressure Sensor Primary - Secondary Circuit With Variable Speed Secondary Pumps To Maximize energy system, we must maximize the variable head loss in the system. This is done by locating the sensor at the most remote zone ( hydraulically) in the system.

96 System Control Curve Ft Hd Control curve Overall system curve Distribution piping head loss curve Set point, 25 FT Pump TDH Flow, gpm

97 Variable vs Constant Head Loss

98 The Active Zone Zone set points do not have to be the same. Pump controller scans all zones often, comparing process variable to set point in each case. Pumps are controlled to satisfy the worst case. What happens to the rest of the zones?

99 Basic Concept PMU Set Value 4 20 ma From Field Sensor (DPT) PFU Output To VFD/Pump PFU Pump Functional Unit PMU Pump Management Unit

100 Multi Point Differential Pressure Sensor Different Sensor Signal To Common PFU Panel DPT DPT Balancing Valve Panel with PLC & VFD`s Load Chillers Secondary Pumps Common

101 Multi Point Differential Pressure Sensor POSSIBILITY OF MULTIPLE PROCESS SIGNALS FROM DIFFERENT ZONES PMU Set Value VFD Module PFU VFD Multiple Process Signals From Field Sensors All zones can have different set values

102 Multi Point Differential Pressure Sensor POSSIBILITY OF MULTIPLE PROCESS SIGNALS FROM DIFFERENT ZONES Multiple Process Signals From Field Sensors PMU Set Value VFD 4 20 ma Sig Signal Comparator PFU VFD Signal Comparator All zones can have different set values

103 HVAC Control System DPT Signal Comparator

104 HVAC Control System DPT Signal Comparator - High and Low Signal Selections - Signal Averaging - High/Low Limit Control The module has the addition following features : 1) LED status indications 2) Accepts voltage or milliamp input signal 3) DIP switch-selectable operating modes 4) Accepts 24 VAC/DC power

105 HVAC Control System DPT Signal Comparator Benefits 1) We are able to supply VFD systems with multiple inputs signals ranges to compete with our competitors. 2) We are able to use Grundfos PFU 2000 as the main processor to control the full system operations. 3) We will be minimising outsourcing or external controller in order to serve the HVAC market. 4) The MM allows us to integrate into the system multiple sensor control at a more cost effective price.

106 HVAC System Other Types of Systems

107 Separate System for Each Zone Balancing Valve DPT DPT Load 2 Way Valve Panel with PLC & VFD`s Chillers Secondary Pumps Primary Pumps Common Air - Separator Expansion Tank

108 Separate System for Each Zone Systems In Multi - Zones Two options: 1. Separate Systems can be used for different zones. So each zone will have its own sensor. 2. Signal from different zone sensors is given to the common PFU and most deviated signal, from the set point, is given as output.

109 Tertiary Pumping System VFD pumps For Each Zone Balancing Valve DPT DPT Load 2 Way Valve E-pumps E-pumps Chillers Primary Pumps Common Air - Separator Secondary Pump Expansion Tank

110 Reverse Return Pumping Load Balancing Valve DPT Chillers Panel with PLC & VFD`s Primary Pumps Common Secondary Pumps Air - Separator

111 Reverse Return Pumping Benefits : 1) Equalize the pressure drops of each zone. 2) Selections of the sensor becomes easier. 3) If load are similar or symmetrical, 1 centrally located sensor is adequate. 4) As in direct return system, multiple sensor can still provide a benefit to the end user.

112 Type of VFD Systems

113 Possible Options of Variable Speed panels Type ME - Multiple Pumps & Multiple VFDs. Type MF - Common VFD for Multiple Pumps.

114 System with Multi Pumps & Multi VFDs Signal from Field Sensor(s) (DPT) Panel with PFU & PMU VFD - 1 VFD - 2 Secondary Pumps

115 System with Common VFD for All Pumps Signal from Field Sensor(s) (DPT) Panel with PFU & PMU VFD Secondary Pumps

116 APPROVAL FROM INTERNATIONAL AGENCIES Approval from CE, U/L Conforms to - Electromagnetic compatibility (89/336/EEC) to standard EN and EN and Electrical equipment design 73/23/EEC standard to EN

117 Single PMU For Control of 8 Zones/Pumps PMU PFU PFU

118 Single PMU For Control of 8 Zones/Pumps PMU PFU PFU PFU PFU

119 The End