Local Resistance (TL)

Hydraulic resistance in a pipe in a heat-conducting fluid network.

blockType: EngeeFluids.ThermalLiquid.Fittings.LocalResistance

Path in the library:

/Physical Modeling/Fluids/Thermal Liquid/Pipes & Fittings/Local Resistance (TL)

Description

Block Local Resistance (TL) simulates pressure losses related to the resistance of a pipe, which is set by the user, in a network of heat-conducting liquid. In the block, you can set different values of loss coefficients for forward and reverse flows through the pipe section.

The loss coefficient can be set to a constant value determined by the pressure in the pipe, or it can be found from the user table of loss coefficients and the corresponding Reynolds numbers.

Constant loss ratio

The resistance coefficients of the sections where they can be considered constant in a given speed range are calculated as:

where

and — parameter values Forward flow loss coefficient (from A to B) and Reverse flow loss coefficient (from B to A) accordingly;
— pressure drop.

Critical pressure drop — this is the pressure difference determined by the critical Reynolds number Critical Reynolds number, , which is a transition point between laminar and turbulent flow modes:

where

— the loss coefficient determined by the critical pressure and based on the average value of the loss coefficients in the forward and reverse directions;
— kinematic viscosity of the liquid;
— the average density of the liquid;
— the hydraulic diameter of the section, which is the equivalent diameter of a pipe with a non-circular section: , where — parameter value Flow area.

Tabular parameterization method

The loss coefficient can be determined using the data provided by the user on the Reynolds number and the loss coefficient. The vector of Reynolds numbers can have both positive and negative values, which indicates a forward and reverse flow, respectively.:

Conservation of mass

The law of conservation of mass is fulfilled for the pipe section:

The mass flow rate through the pipe section is

where — the flow loss coefficient, which is selected between the parameter values Forward flow loss coefficient (from A to B) and Reverse flow loss coefficient (from B to A) depending on the flow direction in the block.

Energy conservation

The unit provides energy conservation as follows:

where

— energy flow in port A;
— energy flow in port B.

Ports

Conserving

# A — thermal liquid port
thermal liquid

Details

Port of isothermal liquid, corresponds to the inlet or outlet of liquid from a section of pipe. When the flow direction is positive, the liquid flows from port A to port B.

Program usage name

port_a

# B — thermal liquid port
thermal liquid

Details

Port of isothermal liquid, corresponds to the inlet or outlet of liquid from a section of pipe. When the flow direction is positive, the liquid flows from port A to port B.

Program usage name

port_b

Parameters

Main

# Local loss parameterization — the method of calculating hydraulic losses
Constant | Tabulated data - loss coefficient vs. Reynolds number

Details

A method for calculating the loss coefficient in a pipe section.

The loss coefficient can be set to a constant value determined by the pressure in the pipe, or it can be found from the user table of loss coefficients and the corresponding Reynolds numbers.

Values	`Constant` \| `Tabulated data - loss coefficient vs. Reynolds number`
Default value	`Constant`
Program usage name	`resistance_loss_model`
Evaluatable	No

# Forward flow loss coefficient (from A to B) — loss factor for flow from A to B

Details

The loss coefficient related to pressure loss for flows from port A to port B.

Default value	`1.0`
Program usage name	`loss_coefficient_a_b`
Evaluatable	Yes

# Reverse flow loss coefficient (from B to A) — loss factor for flow from B to A

Details

The loss coefficient related to pressure loss for flows from port B to port A.

Default value	`1.0`
Program usage name	`loss_coefficient_b_a`
Evaluatable	Yes

# Reynolds number vector — a vector of Reynolds number values

Details

A vector of Reynolds number values for tabular parameterization of the loss coefficient. The vector must correspond element by element to the vector Loss coefficient vector. The elements of the vector must be set in ascending order.

Dependencies

To use this parameter, set for the parameter Local loss parameterization meaning Tabulated data - loss coefficient vs. Reynolds number.

Default value	`[-500.0, -200.0, -100.0, -50.0, -40.0, -30.0, -20.0, -10.0, 10.0, 20.0, 30.0, 40.0, 50.0, 100.0, 200.0, 500.0, 1000.0, 2000.0]`
Program usage name	`Re_vector`
Evaluatable	Yes

# Loss coefficient vector — vector of loss coefficients

Details

Vector on loss coefficients for tabular parameterization of the loss coefficient, where — the length of the vector of values of the Reynolds number. The elements of the vector must be larger 0.

Dependencies

To use this parameter, set for the parameter Local loss parameterization meaning Tabulated data - loss coefficient vs. Reynolds number.

Default value	`[0.65, 0.75, 0.90, 1.15, 1.35, 1.65, 2.3, 3.10, 4.0, 2.70, 1.80, 1.46, 1.30, 0.90, 0.65, 0.42, 0.30, 0.20]`
Program usage name	`loss_coefficient_vector`
Evaluatable	Yes

# Flow area — the cross-sectional area of the site
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The cross-sectional area of the pipe section.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`1e-3 m^2`
Program usage name	`flow_area`
Evaluatable	Yes

# Critical Reynolds number — upper limit of the Reynolds number for laminar flow

Details

The upper bound of the Reynolds numbers for the laminar flow regime.

Default value	`150.0`
Program usage name	`Re_critical`
Evaluatable	Yes