selection of control valves in variable flow systems · pdf fileselection of control valves in...
TRANSCRIPT
Selection of Control Valves inVariable Flow Systems
By Chris Parsloe
BG 51/2014
A BSRIA Guide www.bsria.co.uk
BG 51 -14 Control Valves COVER_BSRIA Guide Cover 27/05/2014 12:49 Page 1
1
Selection of control valveS in variable flow SyStemS
© bSria bG 51/2014
Acknowledgements
This publication has been written with the help of an industry steering group. BSRIA would like to thank the following people, without whom it would not have been possible:
Simon Barden Arup
Peter Clackett Skanska
Luke Collier BSRIA
Stuart Cruickshank Samson Controls Ltd.
Elio Galluzzi SAV Systems Ltd.
Ashish Goyal Honeywell
Andy Harrop Armstrong Fluid Technology
Stephen Hart Frese
Andy Lucas Crane Building Services & Utilities
Nick Martin Marflow Hydronics Ltd.
Martyn Neil Danfoss Ltd.
John Middleton Samson Controls Ltd.
Justin Pearce Belimo Automation UK Ltd.
David Queen Herz Valves UK Ltd.
Christian Bo Rasmussen Frese
Peter Rees TA Hydronics
Mike Smith BSRIA
Bob Swayne The Hampden Consultancy
Hedley Thomas Belimo Automation UK Ltd.
Paul Wightman Danfoss Ltd.
BSRIA acknowledges the very significant contribution made by all the steering group members, and especially the author, Chris Parsloe of Parsloe Consulting. The final editorial responsibility for this publication rested with BSRIA. It was designed and produced by Joanna Smith of BSRIA.
the guidance given in this publication is correct to the best of bSria’s knowledge. However bSria cannot guarantee that it is free of errors. material in this publication does not constitute any warranty, endorsement or guarantee by bSria. risk associated with the use of material from this publication is assumed entirely by the user.
all rights reserved. no part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic or mechanical including photocopying, recording or otherwise without prior written permission of the publisher.
© BSRIA June 2014
Control valves.indd 3 23/05/2014 16:03:28
Selection of control valveS in variable flow SyStemS
© bSria bG 51/2014
contents
1 introDUction 1
1.1 objective 2
2 matcHinG control valve tyPeto terminal Device 4
2.1 natural convection/radiation (passive) 42.2 forced convection (active) 42.3 water to water heat exchangers 5
3 acHievinG effective moDUlatinG control 8
3.1 flow characteristic 83.2 valve authority 103.3 actuators 12
4 control valve SiZinG 13
4.1 motorised on/off valves 134.2 thermostatic radiator valves (trvs) 134.3 three-port control valves 144.4 four-port control valves 164.5 two-port control valves 174.6 Pressure independent control valves (Picvs) 21
referenceS anD biblioGraPHy 25
Control valves.indd 5 23/05/2014 16:03:29
© bSria bG 51/2014
Selection of control valveS in variable flow SyStemS
symbols
Pressure independent controlvalve (note this is different from the symbol used in previous BSRIA publications)
Pump
Pressure test point
Non-return valve
Isolating valve
Drain off cock
Lockshield valve
Double regulating valve
Fixed orifice flow measurementdevice (orifice plate)
Differential pressurecontrol valve
Two-port control valve
Three-port control valve
Four-port control valve
IV
NRV
TP
DPCV
MV
MV
MV
PICV
LSV
DOC
DRV
OP
Control valves.indd 6 23/05/2014 16:03:29
introDUction 1
Selection of control valveS in variable flow SyStemS
© bSria bG 51/2014
1
This guide has been produced to help designers avoid problems with the selection and application of control valves used in hydronic systems. By way of background, BSRIA has been involved in a number of investigations into the performance of one particular type of device that is widely used in variable flow hydronic systems. These devices are collectively referred to as Pressure Independent Control Valves (PICVs). It became apparent that some issues occurred because there was no common format for presenting the performance of PICVs or independent guidance on their selection.
Working with an enthusiastic steering group of manufactures and others, BSRIA researched and produced both a series of test methodologies and a format for the standardisation of the presentation of results. This is published as BTS 1/2012 Test Method for Pressure Independent Control Valves[1]. Having a test standard is very useful to the industry but it is equally important that, armed with useful performance data, the correct selection processes are followed, so equipment choices are appropriate.Working with many of the same manufacturers and others, BSRIA has produced this guide, which effectively complements BTS 1/2012. As this guide is used by practitioners, and as industry practices change or new products emerge and become more prevalent, it may become necessary to revise this guide. Therefore feedback from users, on any aspect of this guide, would be very much appreciated.
For the purposes of this guide, a control valve is a valve which (governed by an automatic control system) varies the flow of water through the pipe or branch in which it is installed. The main valve types discussed in this guide are summarised in Table 1.
This guide explains the selection and sizing of valves for the control of heating or cooling outputs from terminal devices. The term terminal device is used to denote any heating or cooling output device connected to a heating or chilled water pipework system. Examples include radiators, fan coil units, air handling units, chilled beams, trench heaters, plate heat exchangers and calorifiers.
1 IntRodUctIon
Control valves.indd 1 23/05/2014 16:03:29
Selection of control valveS in variable flow SyStemS
© bSria bG 51/2014
5
2matcHinG control valve tyPe to terminal Device
For this type of terminal device (if recommended by the manufacturer) some form of “modulating” control valve can be effective i.e. a valve that varies the flow of water in order to vary the heating or cooling output of the emitter. This might typically include a two-port valve, three-port valve, four-port valve or pressure independent control valve (PICV). However, to be effective, the valve must have the appropriate type of flow characteristic and be sized with sufficient authority for the circuit in which it is located. These concepts are explained in the following sections.
Terminal devices that transfer heat from one flow of water to a different flow of water separated by a thin metal wall do so principally by means of conduction of heat through the separating wall. For this type of terminal device the relationship between flow rate and heat transfer is close to proportional i.e. for each change in flow rate on the input side of the heat exchanger, there is a proportional change in heat transfer.
2.3 Water tO Water heat exchaNgers
Figure 1: relationship between heat transfer and flow rate for forced convection heating and sensible cooling terminal devices.
Hea
t tr
ansf
er (
%)
60 70 80 90 100 1105040302010Design flow rate (%)
Heating ∆T = 10oC
1200
120
110
100
90
80
70
60
50
40
30
20
10
Heating ∆T = 20oC
Heating ∆T = 30oC
Cooling ∆T = 6oC
Control valves.indd 5 23/05/2014 16:03:30
Old Bracknell Lane West, Bracknell, Berkshire, RG12 7AH, UK
Offices in Bracknell, Beijing, Dusseldorf,St Helens, Toulouse, Madrid, Brazil andAssociates in Armagh
BSRIA � the built environment expertsBSRIA gives you confidence in design, added value inmanufacture, competitive advantage in marketing, profitable construction, and efficient buildings
¢ Testing
¢ Modelling
¢ Research
¢ Consultancy
¢ Instrument hire, sales and calibration
¢ Troubleshooting
¢ Information
¢ Training
¢ Publications
¢ Market research and intelligence
Membership is the foundation of BSRIA’sexpertise and independence
Whatever your buildingservices requirement contact BSRIA:
T: +44 (0)1344 465600F: +44 (0)1344 465626E: [email protected] W: www.bsria.co.uk
BG 51 -14 Control Valves COVER_BSRIA Guide Cover 27/05/2014 12:49 Page 2
Energy Efficient PumpingSystems
A design guide
By Chris Parsloe
BG 12/2011
A BSRIA Guide www.bsria.co.uk
Supported by
deeps COVER_D3-2010 Legislation cover.qxd 15/03/2011 10:20 Page 1
ENERGY EFFICIENT PUMPING SYSTEMS © BSRIA BG 12/2011
ACKNOWLEDGEMENTS
This document has been prepared with the support of BRE Trust. The project was undertaken by BSRIA with the assistance of a project steering group drawn from the following companies who provided BSRIA staff with technical assistance and supported the publication of this guide: Andrew Reid and Partners LLP Belimo Automation UK LtdCrane Fluid Systems LtdDanfoss Randall UKFrese Ltd Grundfos LtdHerz Valves UK LtdSAV UK Ltd. The research project was led by Dr Arnold Teekaram of BSRIA, with support from Dr Fiona Lowrie of BSRIA and Chris Parsloe of Parsloe Consulting. The guidance was written by Chris Parsloe with the assistance of a project steering group who were: Andy Lucas David Considine David Queen Howard Hall Jan Hansen Lars Fabricius Luke Collier Paul Wightman Robert Fowler Stephen Hart. The document has also been reviewed by Mike Campbell of AECOM and members of the BSRIA Publications Panel: Jim Mellish and Peter Clackett, Skanska Mitch Layng, Prupim. This publication has been designed and produced by Alex Goddard and Ruth Radburn. Every opportunity has been taken to incorporate the views of the contributors, but final editorial control of this document rests with BSRIA.
This publication has been printed on Nine Lives Silk recycled paper.
©BSRIA March 2011 105060 ISBN 978 0 86022 692 5 Printed by ImageData Ltd
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic or mechanical including photocopying, recording or otherwise without prior written permission of the publisher.
ENERGY EFFICIENT PUMPING SYSTEMS © BSRIA BG 12/2011
CONTENTS
1 INTRODUCTION 1
1.1 Scope 1 1.2 Guide structure 1
2 SUMMARY OF RECOMMENDATIONS 2
2.1 Variable or constant flow 2
3 PUMP ENERGY FUNDAMENTALS 4
3.1 Calculating pump energy 4 3.2 Pump affinity laws 6 3.3 Pump speed control 8
4 PIPE SIZING 11
5 PIPE LAYOUT 13
6 SYSTEM CONTROL ISSUES 17
6.1 Remote sensor control 17 6.2 Temperature differentials 18 6.3 Constant and variable temperature circuits 19 6.4 Effect of flow on temperature differential 20 6.5 System by-passes 21 6.6 Pump minimum flow-rate 23 6.7 Flow control at terminals 25 6.8 Secondary hot water circuits 26 6.9 Primary circuits 29 6.10 Low emission heat sources 33
APPENDIX A: VALVE TERMINOLOGY 34
APPENDIX B: SYSTEM LIFE CYCLE ENERGY CALCULATIONS 35
APPENDIX C: COMMISSIONING ISSUES 39
REFERENCES 40
ENERGY EFFICIENT PUMPING SYSTEMS © BSRIA BG 12/2011
FIGURES
Figure 1: Pressure loss diagram for a simple pumped circuit 5 Figure 2: Constant pressure pump speed control 9 Figure 3: Proportional pump speed control 9 Figure 4: Remote sensor pump speed control 10 Figure 5: Notional terminal unit layout 13 Figure 6: Layout 1 - Single branch flow return layout 14 Figure 7: Layout 2 - Split branch flow return layout 14 Figure 8: Layout 3 - Split branch reverse return layout 14 Figure 9: Layout 4 - Looped reverse return layout 14 Figure 10: Layout 5 - Single flow return layout feeding valve
modules 14 Figure 11: Alternative valve and pump control design solutions 15 Figure 12: Comparative pump energy consumption for alternative
pipe system design solutions 15 Figure 13: Example of potential moving index 17 Figure 14: Secondary pump arrangements for constant and
variable temperature circuits 19 Figure 15: Constant flow by-pass at end of radiator circuit 21 Figure 16: By-pass through an end-of-line four port diverting
control valve 22 Figure 17: Minimum flow rate for canned rotor pumps 23 Figure 18: Determining pump power values at zero flow under
different pump speed control regimes 24 Figure 19: Design resulting in excess flows and pressures across
terminal units 25 Figure 20: Typical temperatures across hot water cylinder at 30 K
design temperature differential 28 Figure 21: Plate heat exchanger unit for provision of hot water 29 Figure 22: Mixing of flows in low loss headers 30 Figure 23: Variable flow primary circuit using boiler shunt pumps 31 Figure 24: Variable flow primary circuit using single primary
pump set 32 Figure 25: Primary circuit integrating low emission heat source
alongside back-up boilers 33 Figure 26: Total life cycle energy consumption for a constant
flow steel pipe system 36 Figure 27: Total life cycle energy consumption for a variable
flow steel pipe system with constant pressure control of pump speed 37
Figure 28: Total life cycle energy consumption for a variable flow steel pipe system with remote sensor control of pump speed 37
ENERGY EFFICIENT PUMPING SYSTEMS © BSRIA BG 12/2011
ABBREVIATIONS BMS Building energy management systemCFR Constant flow regulator DRV Double regulating valve DPCV Differential pressure control valveOP Orifice plate flow measurement deviceDRV Double regulating valve PICV Pressure independent control valveTRV Thermostatic radiator valve For detailed explanation of valve functions, refer to Appendix A.
SYMBOLS
1
1.1
1.2
INTROD
SCOPE
GUIDE STRUCTURE
DUCTIO
Thene ThUStheasso50%deseffi Thpipoptrec In binctheene Moappincleadto leffesou
E Secrecexp
ON
his applicationergy efficient
he potential foS Departmene world’s eneociation of p% more enersign and instaiciency may b
he recommenpe sizing methtions and systcommendatio
building servcur the largesese applicatioergy savings d
ost of the guiplications. Socluding districd to missed elower systemectiveness of urces.
ction 2 provicommendatioplained in Se
n guide provt pumping sy
for reducing pt of Energy e
ergy use by elump manufa
rgy efficient ballation[2]. Thbe achieved.
ndations presehods, pipewotem control mon are also av
vices applicatt pumping lons. Cooling due to the la
idance is appome sections ct heating, benergy saving
m temperaturef some low ca
ides an execuons. The resections 3 to 6
ENE
ides recommystems.
pump energyestimates thatlectric motoracturers) estimby careful cohis guide show
ented here arork layouts, vmeasures. Se
vailable from
tions, heatingoads. This gusystems usua
arger flow rat
licable to boare written secause a lackgs elsewhere.e differentialsarbon emissio
utive summarearch process6.
INTROD
ERGY EFFICIEN
mendations on
y consumptiot pumping acrs[1]. Europummates that sysnsideration ows some way
re based on avalve selectioeparate resear
BSRIA.
g and coolinguide thereforeally offer the tes involved.
th heating anspecifically fok of regard fo. For exampls, thereby reon or renewa
ry of the mai, its findings,
DUCTION
NT PUMPING
© BSRIA BG
n the design
on is substantccounts for 2mp (a pan Eustems could bof componenys in which t
analyses of altons, pump corch reports fo
g systems usue focuses mabest scope fo
nd cooling or heating sysor pump enerle, excess flowducing the able energy h
in design , and conclus
SYSTEMS
G 12/2011
1
of
tial. The 20% of uropean be 30 to nts, his
ternative ontrol or each
ually inly on
or pump
stems, rgy may ws tend
heat
sions are
1