Heat Exchanger Interface (G)
Thermal boundary between the gas and the environment.
blockType: EngeeFluids.HeatExchangers.EffectivenessNTU.Interfaces.Gas
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Path in the library: |
Description
The Heat Exchanger Interface (G) block simulates heat transfer by means of gas flow inside the heat exchanger. Use a second heat exchanger block to model a pair of heat transfer fluids. The boundaries can be in different heat transfer media, e.g. one in a liquid and the other in a gas. Use the block E-NTU Heat Transfer, to connect the interfaces and capture the heat transfer between the heat transfer fluids.
Mass conservation
Implementing a fixed volume block allows you to reflect changes in the mass flow rate of the heat transfer fluid due to compressibility. The total mass storage rate is equal to the sum of the mass flow rates through the ports:
where
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- mass accumulation rate;
-
- mass flow rate. The subscripts denote ports A and B.
The mass flow rate is positive when it is directed into the gas channel. Changes in density are reflected in the mass accumulation rate:
where
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- density;
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- pressure;
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- specific internal energy;
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- volume.
Conservation of momentum
Conservation of momentum between the inlet and outlet ports of a heat exchanger determines the direction and velocity of flow within the heat exchanger. Changes in momentum are mainly due to friction losses from pipe bends that result in pressure changes. Local resistances such as bends, elbows and tees can cause flow separation, resulting in negligible additional pressure losses. For steady-state flows, the mass flow rate remains constant.
Conservation of momentum is applied to each segment of the gas (pipe) volume. This figure shows a bundle of pipes divided into two volumes and three nodes. The nodes correspond to ports A, B, and the coolant volume . These nodes define the coolant states, such as pressure and temperature, and properties, such as density and viscosity.
Note that the flow inertia is negligible and the flow is assumed to be quasi-stationary. The conversion of transients to mass flow rates may be biased: due to the coupling between density, pressure and temperature, the propagation of changes through the system is not instantaneous. Other sources and recipients of momentum, such as head differences between ports or radial deformations of the channel wall, are not considered. The momentum conservation equation for half of the volume in port A has the form:
where
-
- is the pressure at the node indicated in the subscript;
-
- is the total pressure loss between the port node and the internal node due to friction.
The total pressure loss includes both major and minor losses. The momentum conservation equation for half of the volume at port B is of the form:
Friction
The pressure change caused by viscous friction depends on the square of the mass flow rate for turbulent flows and on the magnitude of the mass flow rate for laminar flows. This pressure change is characterised by three dimensionless parameters: the Darcy friction coefficient, the pressure loss coefficient and the Euler number. These numbers are calculated from empirical relationships or estimated from look-up tables, depending on the parameters Pressure loss model.
The division into laminar or turbulent flow is based on the Reynolds number. When the Reynolds number is above the parameter Turbulent flow lower Reynolds number limit, the flow is fully turbulent. When the Reynolds number is below the parameter Laminar flow upper Reynolds number limit, the flow is fully laminar. Reynolds numbers between these values indicate transient flows. Transient flows exhibit characteristics of both laminar and turbulent flows. In Engee, numerical smoothing is applied between these boundary values.
Ratio for flow inside pipes.
If the parameter Pressure loss model is set to the value of Correlation for flow inside tubes, then the Darcy friction coefficient for the pipes is used, . The momentum conservation equation for half the volume in port A has the form:
where
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- pipe length;
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- pipe length for the calculation of equivalent losses, which reproduces the negligible viscous losses by usage instead of elbows, tees, joints or other local resistances;
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- cross-sectional area of the pipe, in case of non-uniform cross-sectional area should be used ;
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- the hydraulic diameter of the pipe, or the diameter of a circle equal in area to the cross-sectional area of the pipe:
If the pipe has a circular cross-section, the hydraulic diameter and the pipe diameter are the same.
The equation of momentum conservation for half of the volume in the port B has the form:
For turbulent flows, the Darcy friction coefficient is calculated using the Haaland relation. The Reynolds number is set at the boundary port:
where is the roughness of the wall taken as a characteristic height, the value of the parameters Internal surface absolute roughness.
For laminar flows, the friction coefficient depends on the pipe shape and is calculated using the pipe shape coefficient:
where is the shape coefficient, the value of the parameters Laminar friction constant for Darcy friction factor.
Reynolds number is calculated in the boundary port as:
Substituting into the port pressure loss equation A, the momentum conservation equation is transformed as follows:
Similarly, the momentum conservation equation for half the volume in port B will be of the form:
The usage of the pressure loss coefficient
If the parameter Pressure loss model is set to . Pressure loss coefficient, then the pressure loss coefficient, is used. Use this option for ducts other than pipes.
The momentum conservation equation for turbulent flows for half the volume in port A has the form:
The momentum conservation equation for turbulent currents for half the volume in port B is of the form:
The equation of conservation of momentum for laminar currents for half the volume in port A has the form:
where is the block parameter Laminar flow upper Reynolds number limit.
The equation of conservation of momentum for laminar flows for half of the volume in the port B has the form:
Table data for determining the Darcy friction coefficient based on Reynolds number
If the parameter Pressure loss model is set to . `Tabulated data - Darcy friction factor vs. Reynolds number`then the tabular data for determining the Reynolds number-based Darcy friction coefficient for flows in the pipe are used.
The momentum conservation equation for half of the volume in the port A has the form:
The equation of conservation of momentum for half the volume in port A has the form:
For the turbulent regime, the friction coefficient is given as a tabulated function of the Reynolds number:
The reference points of the tabular function are taken from the vector parameters of the block. The parameter Reynolds number vector for Darcy friction factor defines the independent variable, and the parameter Darcy friction factor vector defines the dependent variable. Linear interpolation is applied between the reference points. Outside the data range of the table, the nearest reference point defines the coefficient of friction.
For the laminar regime, the coefficient of friction is determined from the shape factor, :
Table data for determining the Euler number based on the Reynolds number
If the parameter Pressure loss model is set to . `Tabulated data - Euler number vs. Reynolds number`then the tabular data for determining the Reynolds number Euler number is used. This calculation depends on the flow regime and the Euler number is given as a tabular function of the Reynolds number:
The reference points of the tabular function are taken from the vector parameters for Reynolds numbers and Euler numbers. The parameter Reynolds number vector for Euler number specifies the independent variables, the Reynolds numbers, and the parameter Euler number vector specifies the dependent variable, the Euler number, for each Reynolds number. Linear interpolation is applied between the reference points. Outside the data range of the table, the nearest reference point defines the coefficient of friction.
The momentum conservation equation for turbulent currents for half the volume in port A is:
where is the Euler number in port A.
The equation of momentum conservation for turbulent flows for half of the volume in the port B has the form:
The equation of conservation of momentum for laminar currents for half the volume in port A has the form:
where
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- is the value of parameters Laminar flow upper Reynolds number limit;
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- Euler number calculated from tabulated data at a given Reynolds number.
The equation of momentum conservation for laminar flows for half of the volume in the port B has the form:
Conservation of energy
Energy conservation in a volume of gas is made up of the gas flow rate across the channel boundaries and the associated heat transfer. Energy can be transferred by advection in the ports and convection at the wall. Although heat conduction contributes to energy conservation in the ports, it is often negligible compared to advection. However, heat conduction is not negligible in heat transfer fluids that are in a near-steady state, such as when the fluid stagnates or changes direction. The energy conservation equation is as follows:
where
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and are the energy fluxes at ports A and B, respectively;
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- heat flux.
Advection and conduction are accounted for in , and convection is accounted for in . Heat flux is positive if it is directed into the gas volume.
Heat flux
Heat transfer between two heat transfer fluids in a heat exchanger occurs through several mechanisms:
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Convection at the heat transfer medium interfaces;
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conduction through layers of deposits;
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heat conduction through the wall thickness.
Heat transfer extends beyond the gas channel, so other blocks are required to model the entire heat exchanger system. The second heat exchanger boundary block models the second flow channel and the E-NTU Heat Transfer block models the heat flow through the wall. Heat transfer parameters specific to the gas channel, but required by the E-NTU Heat Transfer block, are available through the scalar ports:
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The C port outputs the value of the flux heat capacity, which is a measure of the gas’s ability to absorb heat and is needed to calculate the number of transfer units (NTU). The flux heat capacity of is calculated as:
where is the specific heat capacity.
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The HC port outputs the heat transfer coefficient, .
If the heat transfer coefficient is considered a constant value, its value is uniform throughout the flow channel. If the heat transfer coefficient is variable, it is calculated for each port from the expression:
where
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- Nusselt number;
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- thermal conductivity;
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- hydraulic diameter for heat transfer.
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The hydraulic diameter is calculated as:
where
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- is the value of parameters Heat transfer surface area;
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- the value of the parameters Length of flow path for heat transfer.
Nusselt number
The Nusselt number is based on empirical relationships to the Reynolds and Prandtl numbers. Use the parameters Heat transfer coefficient model, to select the most appropriate formulation for the simulation.
The simplest model Constant heat transfer coefficient, obtains the heat transfer coefficient directly from the value of the parameter Gas-wall heat transfer coefficient.
The model Correlation for flow inside tubes uses analytical relationships with constant or calculated parameters to reflect the Nusselt number dependence on the flow regime for flows in pipes.
The remaining models are tabulated functions of the Reynolds number. They are useful for varying Nusselt numbers or heat transfer coefficients at different flow regimes. The functions are generated from experimental relationships between Reynolds number and Colburn factor or Reynolds number and Prandtl number for Nusselt number.
Constant heat transfer coefficient.
If the parameters Gas-wall heat transfer coefficient are set to the value of Constant heat transfer coefficient, then the heat transfer coefficient is a constant and the Nusselt number is not used in the calculations. Use this parameterization as a simple approximation for gas flows confined to the laminar regime.
Ratios for pipes
If the parameter Gas-wall heat transfer coefficient is set to `Correlation for flow inside tubes', the Nusselt number depends on the flow regime.
For turbulent flows, its value varies proportionally to the Reynolds number and is calculated by the Gnelinski relation:
where
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- Reynolds number;
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- Nusselt number;
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- Prandtl number;
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- friction coefficient, which coincides with the coefficient used in calculations of pressure loss in the pipe.
For laminar flows, the Nusselt number is a constant. Its value can be obtained from the parameters Nusselt number for laminar flow heat transfer, :
Table data for determining the Colburn factor as a function of Reynolds number
If the parameter Gas-wall heat transfer coefficient is set to the value of Tabulated data - Colburn factor vs. Reynolds number, then tabular data is used to determine the Colburn factor based on the Reynolds number. The Colburn equation is used to determine the Nusselt number, which varies in proportion to the Reynolds number. The Colburn factor is a measure of the proportionality between the Reynolds, Prandtl and Nusselt numbers:
where is the Reynolds number based on the hydraulic diameter for heat transfer, , and the minimum free flow area in the channel,
Table data for determining the Nusselt number as a function of Prandtl and Reynolds numbers
If the parameters Gas-wall heat transfer coefficient are set to the value of `Tabulated data - Nusselt number vs. Reynolds number and Prandtl number`then the tabular data for determining the Nusselt number as a function of the Prandtl and Reynolds numbers are used. Linear interpolation is used to determine the values between the reference points.
The Nusselt number is a function of and , so the parameters Reynolds number vector for Nusselt number, Prandtl number vector for Nusselt number, and Nusselt number table, Nu(Re,Pr) define the table reference points:
The tabulated Reynolds number must be calculated based on the hydraulic diameter for heat transfer, .
Ports
Conserving
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A
—
gas inlet or outlet
gas
Details
Inlet or outlet port on the gas side of the heat exchanger.
| Program usage name |
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B
—
gas inlet or outlet
gas
Details
Inlet or outlet port on the gas side of the heat exchanger.
| Program usage name |
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#
H
—
thermal boundary
`heat
Details
The thermal boundary between the heat transfer fluid being modelled and the heat exchanger boundary.
| Program usage name |
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Output
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C
—
flux heat capacity
scalar
Details
The instantaneous value of the flux heat capacity of a gas given as a scalar.
| Data types |
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| Complex numbers support |
No |
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HC
—
heat transfer coefficient
scalar
Details
The instantaneous value of the heat transfer coefficient between the gas flow and the wall, given as a scalar.
| Data types |
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| Complex numbers support |
No |
Parameters
Parameters
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Minimum free-flow area —
cross-sectional area of the hole at the narrowest point
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2
Details
Minimum cross-sectional area of orifice between inlet and outlet. If the channel is a set of channels, tubes, slots or grooves, the value of this parameter is equal to the sum of the smallest areas at the point of minimum flow area. This parameter represents the area where the fluid velocity is maximum. For example, if the fluid flows perpendicular to a series of tubes, the value of this parameter is the sum of the gaps between tubes in the same cross-section where the sum of the gaps is smallest.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
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Hydraulic diameter for pressure loss —
hydraulic diameter
m | cm | ft | in | km | mi | mm | um | yd
Details
Effective internal diameter of the flow. If the cross-sectional diameter varies, the value of this parameter is the diameter at the narrowest point. For non-circular channels, the hydraulic diameter is the equivalent diameter of a circle with the same area as the existing channel.
If the channel is a combination of channels, pipes, slots, or grooves, the total perimeter is equal to the sum of the perimeters of all channels combined. If the channel is a single pipe or tube with a circular cross-section, the hydraulic diameter is equal to the true diameter.
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| Default value |
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| Evaluatable |
Yes |
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Gas volume —
total volume of heat transfer fluid in the duct
l | gal | igal | m^3 | cm^3 | ft^3 | in^3 | km^3 | mi^3 | mm^3 | um^3 | yd^3 | N*m/Pa | N*m/bar | lbf*ft/psi | ft*lbf/psi
Details
The total volume of heat transfer fluid contained in the flow channel of a gas or thermal liquid.
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Laminar flow upper Reynolds number limit — beginning of transition between laminar and turbulent regimes
Details
The Reynolds number value corresponding to the beginning of the transition from laminar to turbulent regime. Above this number, inertial forces become increasingly dominant. By default, the value is given for round tubes and tubes with a smooth surface.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Turbulent flow lower Reynolds number limit — end of transition between laminar and turbulent regimes
Details
The Reynolds number value corresponding to the end of the transition from laminar to turbulent regime. Below this number, viscous forces become increasingly dominant. The by default value is for round tubes and tubes with smooth surfaces.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Pressure loss model —
mathematical model for calculating pressure loss due to friction
Pressure loss coefficient | Correlation for flow inside tubes | Tabulated data - Darcy friction factor vs. Reynolds number | Tabulated data - Euler number vs. Reynolds number
Details
Mathematical model for pressure loss due to friction. This parameter determines which expressions to use for the calculation and which block parameters to specify as input.
For more information, see. Friction.
| Values |
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| Default value |
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| Program usage name |
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| Evaluatable |
No |
# Pressure loss coefficient — total loss factor for all flow resistances between ports
Details
Total loss factor for all flow resistances in the channel, including wall friction (major losses) and local resistances due to bends, elbows and other geometry changes (minor losses).
The loss factor is an empirical dimensionless number used to express the pressure loss due to friction. It can be calculated from experimental data or derived from product specifications.
Dependencies
To use this parameter, set the parameters Pressure loss model to . Pressure loss coefficient.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Length of flow path from inlet to outlet —
distance travelled from port to port
m | cm | ft | in | km | mi | mm | um | yd
Details
The total distance the flow must travel between ports. In multi-pass shell-and-tube heat exchangers, the total distance is the sum of all the passes of the shell. In tube bundles, corrugated plates and other ducts where the flow is divided into parallel branches, it is the distance travelled per branch. The longer the flow path, the greater the basic pressure loss due to wall friction.
Dependencies
To use this parameter, set the parameters Pressure loss model to the value of Correlation for flow inside tubes or Tabulated data - Darcy friction factor vs. Reynolds number.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Aggregate equivalent length of local resistances —
total minor pressure loss expressed in length
m | cm | ft | in | km | mi | mm | um | yd
Details
Total minor pressure loss expressed in length. The length of a straight duct results in an equivalent loss equal to the sum of the existing local resistances of branches, tees and connections. The greater the equivalent length, the higher the pressure loss due to local resistances.
Dependencies
To use this parameter, set the parameter Pressure loss model to . Correlation for flow inside tubes.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Internal surface absolute roughness —
average height of roughnesses on the wall surface that contribute to friction losses
m | cm | ft | in | km | mi | mm | um | yd
Details
The average height of the roughnesses on the wall surface that contribute to friction losses. The greater the average height, the rougher the wall and the greater the pressure loss due to friction. Surface roughness is necessary to obtain the Darcy coefficient of friction from the Haaland relationship.
Dependencies
To use this parameter, set the parameters Pressure loss model to . Correlation for flow inside tubes.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Reynolds number vector for Darcy friction factor — Reynolds number at each reference point in the Darcy friction coefficient look-up table
Details
The Reynolds number at each anchor point in the Darcy friction coefficient lookup table. The block interpolates between the reference points and extrapolates from them to obtain the Darcy friction coefficient at any Reynolds number. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The values of Reynolds numbers must be greater than zero and monotonically increasing from left to right. They can cover laminar, transient and turbulent regimes. The dimensionality of this vector should be equal to the dimensionality of the vector Darcy friction factor vector for the calculation of tabulated reference points.
Dependencies
To use this parameter, set the Pressure loss model parameters to the value of Tabulated data - Darcy friction factor vs. Reynolds number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Darcy friction factor vector — Darcy friction coefficient at each reference point of the Reynolds number look-up table
Details
Darcy’s coefficient of friction at each anchor point in the Reynolds number lookup table. The block interpolates between and extrapolates from the reference points to obtain the Darcy friction coefficient at any Reynolds number. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The values of the Darcy friction coefficient should not be negative and should line up from left to right in ascending order of the corresponding Reynolds numbers. The dimensionality of this vector should be equal to the dimensionality of the vector Reynolds number vector for Darcy friction factor for the calculation of tabulated reference points.
Dependencies
To use this parameter, set the Pressure loss model parameter to Tabulated data - Darcy friction factor vs. Reynolds number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Laminar friction constant for Darcy friction factor — pressure loss correction for the flow cross-section under laminar flow conditions
Details
Pressure loss correction for laminar flow. This parameter is called the shape coefficient and can be used to obtain the Darcy friction coefficient for laminar pressure loss calculations. The By default value corresponds to cylindrical pipes.
Some additional shape coefficients for non-circular cross sections can be determined from analytical solutions of the Navier-Stokes equations. A duct with a square cross section has a shape factor of 56, a duct with a rectangular cross section with an aspect ratio of 2:1 has a shape factor of 62, and a coaxial pipe has a shape factor of 96. A thin duct between parallel plates also has a shape factor of 96.
Dependencies
To use this parameter, set the parameter Pressure loss model to the value of Correlation for flow inside tubes.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Reynolds number vector for Euler number — Reynolds number at each reference point in the Euler number look-up table
Details
The Reynolds number at each anchor point in the Euler number lookup table. The block interpolates between the reference points and extrapolates from them to obtain the Euler number at any Reynolds number. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The values of Reynolds numbers must be greater than zero and monotonically increasing from left to right. They can cover laminar, transient and turbulent regimes. The dimensionality of this vector should be equal to the dimensionality of the vector Euler number vector for the calculation of tabulated reference points.
Dependencies
To use this parameter, set the Pressure loss model parameters to the value of Tabulated data - Euler number vs. Reynolds number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Euler number vector — Euler number at each reference point in the Reynolds number look-up table
Details
The Euler number at each anchor point in the Reynolds number lookup table. The block interpolates between the reference points and extrapolates from them to obtain the Reynolds number at any Euler number. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The values of the Darcy friction coefficient should not be negative and should line up from left to right in ascending order of the corresponding Reynolds numbers. The dimensionality of this vector should be equal to the dimensionality of the vector Reynolds number vector for Euler number for the calculation of tabulated reference points.
Dependencies
To use this parameter, set the Pressure loss model parameter to Tabulated data - Euler number vs. Reynolds number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Heat transfer coefficient model —
mathematical model for heat transfer between the coolant and the wall
Constant heat transfer coefficient | Correlation for flow inside tubes | Tabulated data - Colburn factor vs. Reynolds number | Tabulated data - Nusselt number vs. Reynolds number and Prandtl number
Details
Mathematical model for heat transfer between the heat transfer medium and the wall. The choice of model determines which expressions to apply and which parameters to specify for heat transfer calculations.
For more details see. Nusselt number.
| Values |
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| Default value |
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| Program usage name |
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| Evaluatable |
No |
#
Gas-wall heat transfer coefficient —
heat transfer coefficient by convection between the coolant and the wall
W/(m^2*K) | Btu_IT/(hr*ft^2*deltadegR)
Details
Heat transfer coefficient for convection between the heat transfer medium and the wall.
Dependencies
To use this parameter, set the parameters Heat transfer coefficient model to . Constant heat transfer coefficient.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Heat transfer surface area —
effective surface area used in the heat transfer between the heat transfer medium and the wall
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2
Details
Effective surface area used in heat transfer between a fluid and a wall. The effective surface area is the sum of the primary and secondary surface areas, the area where the wall is exposed to the fluid, and the fin area, if any, used. The fin surface area is usually calculated from the fin efficiency factor.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Length of flow path for heat transfer —
characteristic length travelled during heat transfer between the heat transfer medium and the wall
m | cm | ft | in | km | mi | mm | um | yd
Details
The characteristic length for heat transfer between the heat transfer medium and the wall. This length is used to determine the hydraulic diameter of the channel.
Dependencies
To use this parameter, set the parameters Heat transfer coefficient model to the value of Tabulated data - Colburn factor vs. Reynolds number or Tabulated data - Nusselt number vs. Reynolds number and Prandtl number.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Nusselt number for laminar flow heat transfer — constant value of Nusselt number for laminar flow
Details
Constant value of Nusselt number for laminar flows. The Nusselt number is required to calculate the heat transfer coefficient between the heat transfer medium and the wall. The value by default corresponds to a cylindrical pipe.
Dependencies
To use this parameter, set the parameter Heat transfer coefficient model to the value of Correlation for flow inside tubes.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Reynolds number vector for Colburn factor — Reynolds number at each reference point of the Colburn factor look-up table
Details
The Reynolds number at each anchor point in the Colburn factor lookup table. The block interpolates between the reference points and extrapolates from them to get the Colburn factor at any Reynolds number. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The values of Reynolds numbers must be greater than zero and monotonically increasing from left to right. They can cover laminar, transient and turbulent regimes. The dimensionality of this vector should be equal to the dimensionality of the vector Colburn factor vector for the calculation of tabulated reference points.
Dependencies
To use this parameter, set the Heat transfer coefficient model parameters to the value of Tabulated data - Colburn factor vs. Reynolds number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Colburn factor vector — Colburn factor at each reference point in the Reynolds number look-up table
Details
Colburn factor at each anchor point in the Reynolds number lookup table. The block interpolates between the reference points and extrapolates from them to obtain the Reynolds number at any Colburn factor. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The Colburn factor values must not be negative and must line up from left to right in ascending order of the corresponding Reynolds numbers. The dimensionality of this vector should be equal to the dimensionality of the vector Reynolds number vector for Colburn factor for the calculation of tabulated reference points.
Dependencies
To use this parameter, set the Heat transfer coefficient model parameter to Tabulated data - Colburn factor vs. Reynolds number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Reynolds number vector for Nusselt number — Reynolds number at each reference point in the Nusselt number look-up table
Details
The Reynolds number at each anchor point in the Nusselt number lookup table. Either the Reynolds number or the Prandtl number can be the independent variable. The block interpolates between the reference points and extrapolates from them to obtain the Nusselt number at any Reynolds number. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The values of Reynolds numbers must be greater than zero and monotonically increasing from left to right. They can cover laminar, transient and turbulent regimes. The dimensionality of this vector should be equal to the number of rows in the table Nusselt number table, Nu(Re,Pr). If the table has rows and columns, then the Reynolds number vector must be of length elements.
Dependencies
To use this parameter, set the parameter Heat transfer coefficient model to Tabulated data - Nusselt number vs. Reynolds number and Prandtl number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Prandtl number vector for Nusselt number — Prandtl number at each reference point of the Nusselt number look-up table
Details
The Prandtl number at each anchor point in the Nusselt number lookup table. The independent variable can be either the Reynolds number or the Prandtl number. The block interpolates between the reference points and extrapolates from them to obtain the Nusselt number at any Prandtl number. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The values of Prandtl numbers must be greater than zero and monotonically increasing from left to right. They can cover laminar, transient and turbulent regimes. The dimensionality of this vector should be equal to the number of columns in the table Nusselt number table, Nu(Re,Pr). If the table has rows and columns, the Prandtl number vector must be of length elements.
Dependencies
To use this parameter, set the parameters Heat transfer coefficient model to Tabulated data - Nusselt number vs. Reynolds number and Prandtl number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Nusselt number table, Nu(Re,Pr) — Nusselt number at each reference point of the Reynolds-Prandtl number search table
Details
Nusselt number at each anchor point in the Reynolds-Prandtl number lookup table. The block interpolates between the reference points and extrapolates from them to obtain the Nusselt number at any pair of Reynolds-Prandtl numbers. The interpolation is done using a linear function and the extrapolation is to the nearest value.
The Nusselt number must be greater than zero. Each value must be arranged from top to bottom in order of increasing Reynolds numbers and from left to right in order of increasing Prandtl numbers. The number of rows should be equal to the dimensionality of the vector Reynolds number vector for Nusselt number, and the number of columns should be equal to the dimensionality of the vector Prandtl number vector for Nusselt number.
Dependencies
To use this parameter, set the parameter Heat transfer coefficient model to the value of Tabulated data - Nusselt number vs. Reynolds number and Prandtl number.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Threshold mass flow rate for flow reversal —
threshold mass flow rate
kg/s | N*s/m | N/(m/s) | lbf/(ft/s) | lbf/(in/s)
Details
The mass flow rate below which numerical smoothing is applied. This is to avoid discontinuities when the flow is stagnant.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |