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MapleSim Hydraulics Library from Modelon

Gas Cylinder  Gas volume in a gas-filled piston accumulator

The Gas Cylinder component describes a high-pressure gas volume in a cylinder. For initializing the amount of gas in the cylinder, it is assumed that the preload pressure, p_preload, and the initial temperature, T_start, completely fill the cylinder to initialFilling  s_max, where s_max is the maximum position of the cylinder.

 

Equations

Variables

Connections

Parameters

Equations

`environment.Q_flow`=Mgascp`environment.T`Ttthermaluse_time_constant`environment.Q_flow`=αAheat`environment.T`Totherwise

ρ=MgasV

V&equals;srelPistonAreasrel<smaxsmaxPistonAreaotherwise

cp&equals;Medium.specificHeatCapacityCp_pTp&comma;T

dU&equals;MgasduTptT&plus;dupTtp

dU&equals;ptV&plus;environment.Q_flow

duTp&equals;Medium.specificEnergy_derT_p_pTp&comma;T

dupT&equals;Medium.specificEnergy_derp_T_pTp&comma;T

p&equals;Medium.pressure_dTMgasV&comma;T

flange_a.f&equals;pPistonArea

flange_b.f&equals;f

Aheat&equals;2PistonArea&plus;πdismaxsrel

Mgas&equals;Medium.density_pTppreload&comma;TstartPistonAreainitialFillingsmax

srel&equals;flange_b.sflange_a.s

flange_a.f&plus;flange_b.f&equals;0

Variables

Name

Value

Units

Description

Modelica ID

srel

 

m

Relative position

s_rel

f

 

N

Force between flanges

f

Aheat

 

m2

Heat transfer area

A_heat

Mgas

 

kg

Gas mass filling

M_gas

V

 

m3

Gas Volume of cylinder

V

p

 

Pa

Gas pressure

p

T

 

K

Gas Temperature

T

cp

 

JkgK

Heat capacity of gas

cp

ρ

 

kgm3

Density

rho

duTp

 

JkgK

Partial derivative of inner energy wrt T at constant p

duTp

dupT

 

Jms2kg2

Partial derivative of inner energy wrt p at constant T

dupT

dU

 

W

Energy transfer term

dU

Connections

Name

Description

Modelica ID

flangea

 

flange_a

flangeb

 

flange_b

environment

Port for environment temperature

environment

Parameters

General Parameters

Name

Default

Units

Description

Modelica ID

Vstart

PistonAreasmax

m3

Initial Volume

V_start

Tstart

300

K

Initial gas Temperature

T_start

tthermal

 

s

Thermal time constant

t_thermal

use time constant

true

 

 

use_time_constant

α

150

Wm2K

Heat transfer coefficient

alpha

ppreload

 

Pa

Gas preload pressure

p_preload

Vmax

1

m3

Maximum volume

V_max

di

 

m

Inner diameter of cylinder

d_i

smax

 

m

Maximum position of cylinder

s_max

initial filling

1

 

Initial filling of cylinder as fraction of total

initialFilling

Constant Parameters

Name

Default

Units

Description

Modelica ID

PistonArea

[1]

m2

Cross section area

PistonArea

[1] 14di2π

See Also

Volumes

MapleSim Hydraulics Library from Modelon Overview

 


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