presentation chilled water

Chilled Water Distribution System Dynamic Balancing

Ir. Victor LeungProject Director, J. Roger Preston Limited

Chilled Water Distribution System Dynamic Balancing 2

ContentContent

Overview of traditional balancingmechanics, drawbacks & limitations

Chilled water balancing with constant flow valvemechanics and problem

3 in 1 chilled water dynamic balancingtechnical analysis, benefits


Traditional Chilled Water Balancing Traditional Chilled Water Balancing & Control& Control

MechanicsInitial balancing with commissioning valves under full flow conditionMaintain index circuit supply/ return pressure differential at preset levelModulate cooling coil chilled water control valve opening to regulate chilled water flow rate maintain preset indoor space temperature


Traditional Chilled Water BalancingTraditional Chilled Water Balancing

MechanicsInitial balancing with commissioning valve under full flow condition Require comprehensive chilled water distribution circuit hydraulics analysis to determine initial commissioning valve setting & refinement / adjustment with on site measurement

ProblemsLaborious process to determine valve settingProne to improper and incompletecommissioningInitial static balancing under full flow condition will distorted under dynamic condition


Traditional Chilled Water ControlTraditional Chilled Water Control

MechanicsModulate chilled water control valve opening to regulate chilled water flow rate & maintain preset indoor space temperature

ProblemsSpace temperature controller can only modulate the control valve opening, its effect on chilled water flow rate is unknownRelatively high initial resistance due to necessary 50% control valve authority (ie full open control valve resistance = cooling coil + commissioning valve resistance)


% of Design Flow

Pres

sure

loss

△p[

kPa]

Coil

DRV

0% 100%

HydronicHydronic FundamentalsFundamentalsTraditional control valve and Double Regulating ValveTraditional control valve and Double Regulating Valve(index circuit)(index circuit)


% of Design Flow

Pres

sure

loss

△p[

kPa]

Coil

DRV

0% 100%

Coil + DRV

HydronicHydronic FundamentalsFundamentalsTraditional control valve and double regulating valveTraditional control valve and double regulating valve(index circuit)(index circuit)


% of Design Flow

Pres

sure

loss

△p[

kPa] Control Valve

Coil

DRV

0% 100%

Coil + DRV



% of Design Flow

Pres

sure

loss

△p[

kPa]

Control Valve

Coil

DRV

0% 100%

Coil + DRV

HydronicHydronic FundamentalsFundamentalsTraditional control valve and double regulating valve Traditional control valve and double regulating valve (index circuit)(index circuit)

Index circuit Total pressure drop

Index circuit Total pressure drop


Chilled Water Balancing with Chilled Water Balancing with Constant Flow ValveConstant Flow Valve

MechanicsConstant Flow Valves limit chilled water flow rate to below preset

ProblemsOnly serves to limit flow rate and do not have system resistance balancing function as for commissioning valve since pressure drop across valve remains relatively constant at below preset flow rate

Introduces noticeable resistance to distribution system as valve balancing action depends on pressure loss across valve


33--inin--1 Chilled Water Dynamic Balancing1 Chilled Water Dynamic BalancingMechanics

Combine commissioning/ automatic balancing/ control valve functions into oneDeliver exact chilled water flow rate as determined by space temperature controller

BenefitsSystem initial balancing much simplifiedImproves indoor condition with more direct control of chilled water flow rateMinimizes system chilled water flow resistance

Orifice controlled

by actuator

Orifice self-adjusted by

system pressure


Pres

sure

loss

△p[

kPa]

CoilDynamic Balancing Control valve

% of Design Flow0% 100%

HydronicHydronic FundamentalsFundamentalsDynamic BalancingDynamic Balancing

Coil


Pres

sure

loss

△p[

kPa]




Coil

Total Pressure drop


Advanced TechnicalAnalysis

Advanced TechnicalAnalysis


33--inin--1 Chilled Water Dynamic 1 Chilled Water Dynamic Balancing Balancing –– Static ConditionStatic Condition

Under conditions of all parameters including

P1, P3 and k1, k2, & K being fixed

From (4), P2 varies only with A1

From (3), Q varies only with A1

Note (*) The linearity of Q in equations (1) and (2) depends on manufacturer design and construction tolerance

A2, k2A1, k1

2111 PPAkQ −∝

3222 PPAkQ −∝

3231

2 PPPP

KkQ −−

∝

………..(1*)

………..(2*)

………..(3)

Where k1 & k2 are flow coefficients, and K is relation of A2 to(P1-P3 ), From (1) and (3), we have

3231

22111 PPPP

KkPPAk −

−=− …..(4)


33--inin--1 Chilled Water Dynamic 1 Chilled Water Dynamic Balancing Balancing –– Dynamic ConditionDynamic Condition

Flow rate remain constant with system pressure variation

31 PP −

21 PP −

32 PP −

322 PPAQ −∝

312 PP

KA−

∝

A2, k2A1, k1( - ) no change

therefore, no change

………...….

………...….

…….….

…….….


What are theTechnical Advantages?

What are theTechnical Advantages?

Commissioning

System Performance

Energy Efficiency


Commissioning Performance Energy

Easy Commissioning


Preset of Maximum FlowPreset of Maximum Flow

Valve can be conveniently preset for maximum flow by local adjustment or remote via BMS

Max. flow setting in actuator

Max. flow setting by BMS



Pressure Independent Control


Pressure Independent CharacteristicPressure Independent Characteristic

Flow can be conveniently preset and then maintained constant under dynamic condition with minimum required pressure differential

Accurate control of flow rate over larger control range as compared with traditional control valve

Valve max. flow

Pre-setDesignFlow

50% 6V

max kPamin kPadiff pressure

0 2V

Control SignalDesign flow

Preset

10V100%



Good Space Temperature Control


Steady Space Temperature being maintainedSteady Space Temperature being maintained

18

20

22

24

26

28

30

6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00

Roo

m T

emp

(℃)

Time

With air conditioningWith air conditioning



Linear Control on Flow Rate


Linear Control of Flow RateLinear Control of Flow Rate

0.00

3.60

7.20

10.80

14.40

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

Control signal (V)

Flow

rate

(m

3 /hr)

Testresult

DirectDirect and linearlinear relationship of control signal with and flow rate over noticeable large control range as compared with traditional control valve



Energy Saving


% of Design Flow

Pres

sure

loss

△p[

kPa]

Control Valve

Coil

DRV

0% 100%

Coil + DRV


Index circuitTotal pressure drop

Index circuitTotal pressure drop


Pres

sure

loss

△p[

kPa]




Coil

Total Pressure drop


Pres

sure

loss

△p[

kPa]


Energy Saving Energy Saving in Dynamic Balancing systemin Dynamic Balancing system

System with Traditional Control valve & Double

Regulating Valve

System with Dynamic Balancing

Control Valve

Energy saved

160

95 kPa

50

160 kPa



Flowrate monitoring


Flow MonitoringFlow MonitoringComparison with Electromagnetic Type Flowmeter

No specific requirementMin 5D upstream & 3D downstream to ensure accurate measurement

Installation requirement

Up to 35kPa for valve max. flow rate @ 2m/s

No requirementDiff pressure

Independent of installation.

2% of valve maximum flow rate at 2m/s

Highly depend on compliance of installation requirement.Typical catalogue quoted accuracy: 0.5% of operating range (flowmeter design at 9 to 10m/s).Accuracy @ pipe actual flow rate of 2m/s:1.8 -2.25%

Accuracy

Determine the flow rate by calibrated opening (orifices)

Determine the fluid velocity by induced voltage

Mechanics

3-in-1 Dynamic Balancing Control Valve

Flowmeter(electromagnetic type)


Case Study : Case Study :

Flowrate feedback by the Dynamic Balancing Control valve and monitored by the BMS system

Office Tower in Office Tower in SingaporeSingapore


AHU3

AHU2

AHU1

Chiller1

Chiller2

Chiller3

DCV

CFV3

CFV2

CFV1

FMb

DCV

DCV

qS1

qS2

qS3

qD1

qD2

qD3

Qb

QS

QD

BPV

AHUn DCVqDn

FMQ

DCV Dynamic balancing control valve CFV Constant flow valve BPV By-pass Valve

bFM Flowmeter to measure bypass flow QFM Flowmeter to verify flow in riser

iqD Air Handling Unit demand flow

determined from Dynamic balancingcontrol valve feedback signal

DQ Total system demand flow

= nqDqDqDqD +⋅⋅⋅⋅⋅+++ 321

jqS Supply flow of each chiller

SQ Total plant supply flow = 321 qSqSqS ++

bQ Bypass flow, DS QQ − Pumps and isolation valves not shown

Schematic of the Schematic of the HydronicHydronic SystemSystem


Flow Rate VerificationFlow Rate VerificationResults

QD, Required demand calculated via feedback signal of DCV (3-in-1 dynamic balancing control valves) = qD1 + qD2 + qD3 +…. qDn= 27.44 Lps

FMQ, flow rate measured in supply mains by flowmeter= 27.38 Lps

Only minor variance between summation of DCV valve and flowmeter measurement

AHU3

AHU2

AHU1

Chiller1

Chiller2

Chiller3

DCV

CFV3

CFV2

CFV1

FMb

DCV

DCV

qS1

qS2

qS3

qD1

qD2

qD3

Qb

QS

QD

BPV

AHUn DCVqDn

FMQ


SummarySummary


Chilled Water Distribution System Dynamic BalancingChilled Water Distribution System Dynamic BalancingSummarySummary

Deliver exact flow rate under dynamic condition as required by space temperature controller

Only limit flow rate and do not have balancing function

Only achieve balancing under full load static condition which becomes distorted under dynamic condition which resistance of system components changes

Mechanics

Dynamic system: 3-in-1 Dynamic Balancing Control valve

Constant Flow valve in series with Control valve

Traditional system: Balancing valve in series with Control valve


Convenient preset of maximum flow either locally at the valve or remotely at BMS

No commissioning required

Require laborious hydraulic analysis to determine appropriate valve setting, adjustment of valve setting has to be performed and verified locally at the valve which is prone to error

Commissioning




Chilled Water Distribution System Dynamic BalancingChilled Water Distribution System Dynamic BalancingSummary (conSummary (con’’t)t)


Yes. NilNilFlow rate monitoring

Energy saving due to low initial full load control valve pressure loss and ability to capture reduced system resistance at partial load

Same as the case of Traditional system of balancing valve in series with control valve but with additional energy consumption due to balancing valve resistance

Waste energy due to high initial full load control valve pressure loss and inability to capture reduced system resistance at partial load

Energy efficiency

Dynamic system: 3-in-1 dynamic balancing control valve

Constant flow valve in series with control valve

Traditional system: balancing valve in series with control valve



Superior control performance due to direct relationship of space temperature control signal to chilled water flow rate and satisfactory modulating capability under partial load condition

Do not have system resistance balancing function and hence performance is inferior to traditional commissioning valve

Indirect relationship of space temperature control signal to chilled water flow rate and inferior modulating capability under partial load condition

System Performance






Thank You!Question and Answer

Thank You!Question and Answer

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