π
<-
Chat plein-écran
[^]

FLOW COEFFICIENT


Hierarchy of files

 Downloads
 Files created online(22118)
 HP-Prime(2222)

 mViewer GX Creator App(1770)

DownloadTélécharger


LicenceLicense : Non spécifiée / IncluseUnspecified / Included

 TéléchargerDownload

Actions



Vote :

ScreenshotAperçu


Informations

Catégorie :Category: mViewer GX Creator App HP-Prime
Auteur Author: cext104
Type : Application
Page(s) : 12
Taille Size: 1.53 Mo MB
Mis en ligne Uploaded: 15/09/2021 - 18:55:46
Uploadeur Uploader: cext104 (Profil)
Téléchargements Downloads: 1
Visibilité Visibility: Archive publique
Shortlink : http://ti-pla.net/a2792447

Description 

UNIVERSITÁ DEGLI STUDI DI SALERNO


Bachelor Degree in Chemical Engineering


Course:
Process Instrumentation and Control
(Strumentazione e Controllo dei Processi Chimici)


CONTROL VALVE SIZING

FLOW COEFFICIENT
AND INHERENT CHARACTERISTIC


Rev. 2.3 of March 25, 2021
CONTROL VALVES:
Components
COMPRESSED AIR

taken from:
ACTUATOR Magnani, Ferretti e Rocco (2007)
schematic drawing




ACTUATOR
MEMBRANE

SPRING
STEM
BODY
CLOSURE MEMBER
SEAT
INGOING
FLUID
OUTGOING
FLUID



JOINTS


15/09/2021 Process Instrumentation and Control - Prof. M. Miccio 2
CONTROL VALVES: 
Terminology
NOMINAL PIPE SIZE (NPS): it is the identification value of the interface dimension of a valve and of the
other piping elements. Elements having the same NPS and NP (nominal pressure) can be coupled.
BODY: The body of the valve is the main pressure boundary. It provides the pipe connecting ends and the
fluid flow passageway. It can also support the seating surface and the valve closure member.
PORT: fixed opening or orifice in the body, which determines fluid passing (for globe valves)
TRIM: The assembly of the inside components of a valve, which are in contact directly with the fluid. The
seat, plug, stem and ball are all trim components. With their shapes they determine the flow characteristic
of the valve.
CLOSURE MEMBER: it is a properly shaped movable element. Its position determines the section area
through which the flow crosses the valve. The closure member can assume every position between two limit
positions: closed position, at which corresponds ZERO or the minimum flowrate, and the full-open
position, at which corresponds the maximum flowrate.
FULL CLOSE: a valve is defined full close when the flowrate is zero as the closure member is in closure.
TRAVEL or STROKE or LIFT or OPENING: it is the displacement of the closure member from the closed
position. Usually it is from ½” to 1½“ in a globe valve.
NOMINAL TRAVEL or RATED TRAVEL: it is the travel corresponding to the full-open position.
RELATIVE TRAVEL: it is the ratio between the travel and the nominal travel. It is indicated with h. In closure
position is h=0; in fully open position is h=1.
See also:
https://aabi.uitm.edu.my/controlnotes/control%20valve/Cashco%20Terminology.htm
15/09/2021 Process Instrumentation and Control - Prof. M. Miccio 3
CONTROL VALVES:
Example of a globe valve


cross-sectional drawing

animated view
with




15/09/2021 Process Instrumentation and Control - Prof. M. Miccio 4
CONTROL VALVES:
fluid properties

The flow rate of the fluid crossing the valve can be expressed as either
volumetric or mass. It depends on valve characteristics and on the state and
properties of the fluid, such as:
Inlet pressure, P1
Inlet temperature, T1
Outlet pressure, P2
Pressure drop, ΔP = P1 - P2
Vapor pressure of the liquid, Pv, calculated at the inlet temperature, when
considering negligible the temperature change inside the valve;
Specific gravity of the fluid, Gf = ρ/ρ0, where ρ is the density of the fluid at the
inlet conditions and ρ0= 1000 kg/m3 (T=4°C) is the density of water at ambient
conditions.


15/09/2021 Process Instrumentation and Control - Prof. M. Miccio 5
CONTROL VALVES:
Flow coefficient Cv (for liquids)

• For the flow characteristics of a valve, it is necessary to put the flow
rate passing through the valve to the physical reference state of the
fluid
• The parameter, of British/American origin, which is used to define the
flow characteristics of a valve is, traditionally, the flow coefficient Cv
• In particular,
Cv of a valve is the volumetric flow rate of water in US gal min-1
(one United States gallon is equal to 3.785 liters) crossing the
valve at a temperature between 5÷40°C (Gf=1) for a specified
(partially or full open) valve opening with a static pressure drop
ΔP = 1 psi [=] 6895 Pa

Cv [=] US gal (H2O) min -1 psi-1/2

15/09/2021 Process Instrumentation and Control - Prof. M. Miccio 6
CONTROL VALVES:
Terminology
Cv assumes values between the smallest flow coefficient Cvmin and the largest flow coefficient Cvmax when
the closure member moves from the close position (h=0) to the full opening position (h=1). To understand
the relationship between Cv and h, the following definitions hold:



Nominal (or Rated) value of Cv at the nominal travel (Cvn=Cvmax)
flow coefficient Cvn
Relative flow a non-dimensional ratio  [0,1]
coefficient Φ=Cv/Cvn
Opening value of Φ expressed as a percentage  [0,100]
Rangeability r = ratio between the largest and the smallest flow coefficient;
Cvmax/Cvmin r   for Cvmin = 0
The higher the number, the better. The rangeability is 5:1 on
typical small globe valves (1/2"), 75:1 on a large globe valve (2"),
100:1 on rotating valves, 6:1 practically on butterfly valves.
Inherent characteristic the relationship between the relative flow coefficient Φ and the closure
Φ(h) member travel h with constant pressure drop ΔP across the valve.
The inherent characteristic depends on the conformation of the trim,
of which the shaping of the closure member is also part (in the cage
15/09/2021 valves, from the shape
Process Instrumentation and and dimensions
Control of the holes of the cage) 7
- Prof. M. Miccio
INHERENT CHARACTERISTICS
• The inherent flow characteristics of a valve are defined and provided by the
manufacturer considering:
• a reference fluid (i.e., water)
• a reference temperature
• a reference pressure drop
• They are defined from the flow coefficient CV (or AV or KV)
• They allow to characterize the dependence of the flow rate on the valve's own
characteristics and to compare the ability to pass a flow rate in different valves.
• The flow coefficient Cv (h) results as a monotonically increasing function of the
relative travel h of the closure member.
• When the control valve is a rotary one, the relative travel h is replaced by the
opening angle 
• Following the IEC 534-2-4 norm, the manufacturer must provide the inherent
characteristic of a control valve as table or diagram. In this latter case, the Cv
at 5%, 10% up to 100% of the relative travel at 10% intervals has to be provided.



15/09/2021 Process Instrumentation and Control - Prof. M. Miccio 8
THE MOST COMMON
INHERENT CHARACTERISTICS
Hypothesis: ΔP = const.

Nominal
conditions



Inherent characteristics:
a. linear
b. equal percentage or exponential
c. quadratic or parabolic
d. quick opening
e. butterfly valve or V-Port globe (green)
h
Nominal
travel


NOTE:

ℹ️ The ON/OFF valves generally allow, by varying the degree of opening, an intermediate
position of the closure member and, hence, a partial flow rate.
However, there is no unique correspondence between closure member position and
flowrate. Therefore, they cannot be used for control purposes.

15/09/2021 Process Instrumentation and Control - Prof. M. Miccio 9
THE MOST COMMON
...

Archive contentsContenu de l'archive

Action(s) SizeTaille FileFichier
3.06 Ko KB readme.txt
3.65 Ko KB lisezmoi.txt
1.09 Ko KB FLOW_COE.hpprgm
1.53 Mo MB FLOW_COE.hpappdir.zip
95 octets bytes appslist.txt

Pub / Ads

-
Search
-
Social
-
Featured topics
Concours de rentrée 2021 - La Geste d'Alrys
Concours de rentrée 2021 - Synchro-donjon !
Comparaisons des meilleurs prix pour acheter sa calculatrice !
Remplace ton ancienne fx-92 Collège ou Graph 35 par la nouvelle Graph 35+E II programmable en Python ! Pour tout achat d'une nouvelle Graph 35 d'ici le 30 septembre 2021, Casio te rembourse 10€. En cas de retour de ta fx-92 Collège c'est 18€, et même ou 23€ si tu retournes ton ancienne Graph 35. Etiquette de retour fournie, pas de frais de port à payer, même les anciens modèles et machines non fonctionnelles sont acceptées. En partenariat avec les Restos du cœur.
Remplace ton ancienne fx-92 Collège ou Graph 35 par la Graph 90+E couleur. Pour tout achat, Casio te rembourse 10€ en cas de retour de ta fx-92 Collège, ou 15€ en cas de retour de ta Graph 35. Etiquette de retour fournie, pas de frais de port à payer, même les anciens modèles et machines non fonctionnelles sont acceptées. En partenariat avec les Restos du coeur.
10€ remboursés par Casio sur l'achat de ta calculatrice Graph 35 d'ici le 30 Septembre 2021
Reprise de ton ancienne fx-92 Collège à 5€ ou Graph 35 à 10€. Même non fonctionnelle ou ancien modèle. Etiquette de retour fournie, pas de frais de port à payer. En partenariat avec les Restos du coeur.
25€ remboursés par Casio sur l'achat de ta calculatrice fx-CP400 d'ici le 31 Octobre 2021
3€ remboursés par Casio sur l'achat de ta calculatrice fx-92 Collège d'ici le 30 Septembre 2021
Casio Graph 90+E ou Graph 35+E II avec couvercle personnalisé à gagner sur simple participation aux formations Casio de Septembre 2021.
Coque NumWorks édition limitée Septembre 2021 à gagner.
1234567891011
-
Donations / Premium
For more contests, prizes, reviews, helping us pay the server and domains...
Donate
Discover the the advantages of a donor account !
JoinRejoignez the donors and/or premium!les donateurs et/ou premium !


Partner and ad
Notre partenaire Jarrety Calculatrices à acheter chez Calcuso
-
Stats.
674 utilisateurs:
>656 invités
>12 membres
>6 robots
Record simultané (sur 6 mois):
6892 utilisateurs (le 07/06/2017)

-
Other interesting websites
Texas Instruments Education
Global | France
 (English / Français)
Banque de programmes TI
ticalc.org
 (English)
La communauté TI-82
tout82.free.fr
 (Français)