Flow Resistance (TL)
Hydraulic resistance in the thermal liquid network.
blockType: AcausalFoundation.ThermalLiquid.Elements.FlowResistance
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Description
Block Flow Resistance (TL) simulates the total pressure drop in the thermal liquid network. The pressure drop is proportional to the square of the mass flow. The proportionality coefficient is determined based on the nominal characteristics specified in the parameters of the unit.
This unit is used when only data on the pressure drop at the corresponding mass flow value is known about the component, or when there is no detailed information about the geometry of the component, or it is impossible to theoretically determine the pressure drop in the component based on the geometry of its channel.
Conservation of mass
It is assumed that the volume of fluid inside the hydraulic resistance is negligible. Then the mass flow rate at the input through one port is equal to the mass flow rate at the output through the other port:
,
Where:
-
— mass consumption.
-
Subscripts and — Ports A and B respectively.
Energy conservation
There is no energy exchange in the unit, energy can only be transferred through the ports of the thermal liquid. Heat exchange between the walls and the environment does not occur, the liquid does not do any work. The amount of energy entering per unit of time through one port is equal to the amount of energy leaving through another port per unit of time:
,
Where
-
and — Energy flow through ports A and B, respectively.
Conservation of momentum
An approximation is used when the pressure drop is proportional to the square of the mass flow. For small values of the mass flow in a small region of the laminar flow, the dependence of the pressure drop on the square of the mass flow is linear, resulting in
,
Where:
-
and — pressure at ports A and B, respectively.
-
— crisis value of mass flow rate for laminar-turbulent transition.
-
— proportionality coefficient:
,
Where
-
— the value of the Nominal pressure drop parameter.
-
— the value of the Nominal mass flow rate parameter.
-
Ports
Undirected
A — input or output
thermal liquid
The thermal liquid port corresponds to the inlet or outlet of the hydraulic resistance. This block does not have a specific focus.
B — input or output
thermal liquid
The thermal liquid port corresponds to the inlet or outlet of the hydraulic resistance. This block does not have a specific focus.
Parameters
Nominal pressure drop — pressure drop at known operating mode
0.001 MPa (by default)
The pressure drop from the inlet to the outlet at a known operating mode. The unit uses nominal parameters to calculate the proportionality coefficient between the pressure drop and the mass flow rate.
Nominal mass flow rate — mass flow rate at the known operating mode
0.1 kg/s (by default)
The mass flow rate from the input to the output at a known operating mode. The unit uses nominal parameters to calculate the proportionality coefficient between the pressure drop and the mass flow rate.
Cross-sectional area at ports A and B — cross-sectional area of hydraulic resistance ports
0.01 m2 (by default)
The cross-sectional area of the hydraulic resistance ports. It is assumed that the port sizes are the same.
Fraction of nominal mass flow rate for laminar flow — the ratio of the threshold value of the mass flow to the nominal mass flow
1e−3 (by default)
The ratio of the critical value of the mass flow to the nominal mass flow. In the block, this parameter is used to calculate the crisis value of the mass flow rate, and as a result, to set the limits of the linear approximation for calculating the pressure drop.