Thermal Fluid Two Port
Define the base-equations shared by thermal-fluid two-port components
Description
Equations
Connections
Variables
Parameters
Constants
Modelica Standard Library
A Thermal-Fluid Two-Port is the base model shared by many of the thermal-fluid components. It has two thermal-fluid ports, a and b.
The following equations are the base equations for the two-port model. Each component based on this model extends these equations.
Mass Balance
Mass does not accumulate in the component.
mflowa+mflowb=0
Energy Balance
The power flow into the device equals the rate of energy increase of the mass. If the mass is essentially zero, this is set to exactly zero.
Qflow+Hflowa+Hflowb={mcvT.ε<m0otherwise
Enthalpy Flow
The flow of enthalpy into each port depends on the direction of the mass flow through the component.
Hflowa=mflowa{ha0≤mflowahotherwise
Temperature
The temperature at a port is computed from the specific enthalpy at the port and the specific heat capacity of the medium.
Ta=hacp
Tb=hbcp
Tq=T−signVflow1−tapTΔT
ΔT={T−Ta0≤VflowTb−Totherwise
Volume Flow
The volume flow is given by the mass-flow into port a and the density of the medium.
Vflow=mflowaρ
Pressure Drop
The pressure drop from port a to port b is
Δp=pa−pb
Name
Modelica ID
flowPorta
Thermal-Fluid flow port
flowPort
flowPortb
Units
Δp
Pa
Pressure drop from a to b
dp
px
Pressure at port x
flowPort_x.p
Tx
K
Temperature at port x
T_x
ΔT
Temperature increase of fluid, in direction of flow
dT
Tq
Temperature used for heat exchange with the ambient
Qflow
W
Heat exchange with ambient
Q_flow
Vflow
m3s
Volume flow from from port a to port b
V_flow
h
Jkg
Specific enthalpy of medium
medium.h
hx
Specific enthalpy of flow at port x
flowPort_x.h
Hflowx
Enthalpy flow rate into port x
ρ
kgm3
Density of medium
medium.rho
cp
JkgK
Specific heat capacity of medium at constant pressure
medium.cp
cv
Specific heat capacity of medium at constant volume
medium.cv
The symbol x stands for a or b, it indicates one of the ports.
Default
medium
Thermal-Fluid Media
m
1
kg
Mass of medium in component
T0
293.15
Pressure
ε
1·10−60
A very small number
Modelica.Constants.small
The component described in this topic is from the Modelica Standard Library. To view the original documentation, which includes author and copyright information, click here.
See Also
Thermal Fluid Media
Thermal Overview
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