selection of control valves in variable flow systems · selection of control valves in variable...

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

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


© 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


© bSria bG 51/2014


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


introDUction 1


© 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



© 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


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.


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


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


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

selection of control valves in variable flow systems · selection of control valves in variable...

Documents