Heat Exchanger Interface (G)
The thermal boundary between the gas and the environment.
blockType: EngeeFluids.HeatExchangers.EffectivenessNTU.Interfaces.Gas
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Path in the library: |
Description
Block Heat Exchanger Interface (G) simulates heat transfer through a gas flow inside a heat exchanger. Use the second heat exchanger unit to simulate a pair of heat carriers. The boundaries can be in different heat carriers, for example, one in a liquid and the other in a gas. Use the block E-NTU Heat Transfer to connect the interface and fix the heat transfer between the heat carriers.
Conservation of mass
The implementation of a block with a fixed volume allows you to reflect changes in the mass flow of the coolant due to compressibility. The total rate of mass accumulation is equal to the sum of the mass costs through the ports:
where
-
— the rate of mass accumulation;
-
— mass consumption. Subscripts indicate 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 rate of mass accumulation:
where
-
— density;
-
— pressure;
-
— specific internal energy;
-
— the volume.
Conservation of momentum
The conservation of momentum between the inlet and outlet ports of the heat exchanger determines the direction and velocity of the flow inside the heat exchanger. Momentum changes occur mainly due to friction losses when the pipes are rotated, which lead to pressure changes. Local resistances such as bends, elbows, and tees can lead to flow separation, resulting in minor additional pressure losses. For stationary flows, the mass flow rate remains constant.
Conservation of momentum is applied to each segment of the gas volume (pipe). This figure shows a bundle of pipes divided into two volumes and three nodes. The nodes correspond to ports A, B, and the volume of the coolant . These nodes determine the states of the coolant, such as pressure and temperature, and properties such as density and viscosity.
Note that the inertia of the flow is negligible, and the flow is considered quasi-stationary. The conversion of transients into mass costs may be biased: due to the relationship between density, pressure, and temperature, the propagation of changes through the system is not instantaneous. Other sources and recipients of the pulse, such as the pressure difference between ports or radial deformations of the channel wall, are not taken into account. The momentum conservation equation for half the volume in port A has the form:
where
-
— pressure at the node indicated in the subscript;
-
— total pressure loss between the port node and the inner node due to friction.
Total pressure loss includes both major and minor losses. The momentum conservation equation for half the volume in port B has 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 characterized by three dimensionless parameters: the Darcy friction coefficient, the pressure loss coefficient, and the Euler number. These numbers are calculated using empirical ratios or estimated from search tables, depending on the parameter. Pressure loss model.
The division into laminar or turbulent flow is based on the Reynolds number. When the Reynolds number is higher than the parameter Turbulent flow lower Reynolds number limit, the flow is completely turbulent. When the Reynolds number is lower than the parameter Laminar flow upper Reynolds number limit, the flow is completely laminar. The Reynolds numbers between these values indicate transitional currents. Transient flows exhibit the characteristics of both laminar and turbulent flows. In Engee, numerical smoothing is applied between these boundary values.
The relationship for the flow inside the pipes
If for the parameter Pressure loss model the value is set Correlation for flow inside tubes, then the Darcy coefficient of friction is used for pipes, . The momentum conservation equation for half the volume in port A has the form:
where
-
— pipe length;
-
— pipe length for calculating equivalent losses, which reproduces minor viscous losses when used instead of elbows, tees, joints or other local resistances;
-
— the cross-sectional area of the pipe, in case of a non-uniform cross-sectional area, use ;
-
— the hydraulic diameter of the pipe, or the diameter of the circle, equal in area to the cross-section of the pipe:
If the pipe has a circular cross-section, then the hydraulic diameter and the pipe diameter are the same.
The momentum conservation equation for half the volume in port B has the form:
For turbulent flows, the Darcy coefficient of friction is calculated using the Haaland ratio. The Reynolds number is set at the border port:
where — the roughness of the wall, taken as a characteristic height, the value of the parameter Internal surface absolute roughness.
For laminar flows, the coefficient of friction depends on the shape of the pipe and is calculated using the pipe shape coefficient.:
where — shape coefficient, parameter value Laminar friction constant for Darcy friction factor.
The Reynolds number is calculated at the border port as:
Substituting in the equation of pressure loss in port A, the equation of conservation of momentum is transformed as follows:
Similarly, the momentum conservation equation for half the volume in port B will have the form:
Use of the pressure loss coefficient
If for the parameter Pressure loss model the value is set Pressure loss coefficient, then the pressure loss coefficient is used, . Use this option for channels 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 flows for half the volume in port B has the form:
The momentum conservation equation for laminar flows for half the volume in port A has the form:
where — block parameter Laminar flow upper Reynolds number limit.
The momentum conservation equation for laminar flows for half the volume in port B has the form:
Table data for determining the Darcy coefficient of friction based on the Reynolds number_
If for the parameter Pressure loss model the value is set Tabulated data - Darcy friction factor vs. Reynolds number, then tabular data is used to determine the Darcy coefficient of friction based on the Reynolds number for flows in the pipe.
The momentum conservation equation for half the volume in port A has the form:
The momentum conservation equation for half the volume in port A has the form:
For the turbulent regime, the coefficient of friction is given as a tabular function of the Reynolds number.:
The reference points of the tabular function are taken from the vector parameters of the block. Parameter Reynolds number vector for Darcy friction factor sets an independent variable, and the parameter Darcy friction factor vector — the dependent variable. Linear interpolation is applied between the reference points. Outside the range of the table data, the nearest reference point determines the coefficient of friction.
For the laminar mode, the coefficient of friction is determined from the coefficient of shape, :
Table data for determining the Euler number based on the Reynolds number_
If for the parameter Pressure loss model the value is set Tabulated data - Euler number vs. Reynolds number, then tabular data is used to determine the Euler number based on the Reynolds number. 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 vector parameters for Reynolds numbers and Euler numbers. Parameter Reynolds number vector for Euler number sets the independent variables, the Reynolds numbers, and the parameter Euler number vector sets the dependent variable, the Euler number, for each Reynolds number. Linear interpolation is applied between the reference points. Outside the range of the table data, the nearest reference point determines the coefficient of friction.
The momentum conservation equation for turbulent flows for half the volume in port A has the form:
where — the Euler number in port A.
The momentum conservation equation for turbulent flows for half the volume in port B has the form:
The momentum conservation equation for laminar flows for half the volume in port A has the form:
where
-
— parameter value Laminar flow upper Reynolds number limit;
-
— the Euler number calculated from tabular data for a given Reynolds number.
The momentum conservation equation for laminar flows for half the volume in port B has the form:
Energy conservation
The conservation of energy in the volume of gas consists of the flow of gas through the channel boundaries and the associated heat transfer. Energy can be transferred by advection in ports and convection at the wall. Although thermal conductivity contributes to energy conservation in ports, it is often negligible compared to advection. However, thermal conductivity is not insignificant in heat carriers that are in a state close to stationary, for example, when the heat carrier stagnates or changes direction. The energy conservation equation looks like this:
where
-
and — energy flows at ports A and B, respectively;
-
— heat flow.
Advection and thermal conductivity are taken into account in , and convection is in . The heat flow is positive if it is directed into the gas volume.
Heat flow
Heat transfer between two heat carriers in a heat exchanger occurs through several mechanisms:
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convection at the interface of heat carriers;
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thermal conductivity through sediment layers;
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thermal conductivity through the wall thickness.
Heat transfer extends beyond the gas channel, so other units are required to simulate the entire heat exchanger system. The second block of the heat exchanger boundary models the second flow channel, and the block E-NTU Heat Transfer simulates the heat flow through the wall. Heat transfer parameters specific to the gas channel, but necessary for the unit E-NTU Heat Transfer, accessible via scalar ports:
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Port C outputs the value of the flow heat capacity, which is a measure of the ability of a gas to absorb heat and is necessary to calculate the number of transfer units (NTU). Flow heat capacity calculated as:
where — specific heat capacity.
-
The HC port outputs the heat transfer coefficient, .
If the heat transfer coefficient is considered a constant value, then its value is uniform throughout the flow channel. If the heat transfer coefficient is variable, then it is calculated for each port from the expression:
where
-
— the Nusselt number;
-
— thermal conductivity;
-
— hydraulic diameter for heat transfer.
-
Hydraulic diameter calculated as:
where
-
— parameter value Heat transfer surface area;
-
— parameter value Length of flow path for heat transfer.
The Nusselt number
The Nusselt number is determined based on empirical dependencies on the Reynolds and Prandtl numbers. Use the parameter Heat transfer coefficient model to select the most appropriate formulation for modeling.
The simplest model Constant heat transfer coefficient, obtains the heat transfer coefficient directly from the parameter value Gas-wall heat transfer coefficient.
Model Correlation for flow inside tubes It uses analytical dependencies with constant or calculated parameters to reflect the dependence of the Nusselt number on the flow regime for flows in pipes.
The remaining models are tabular functions of the Reynolds number. They are useful for varying Nusselt numbers or heat transfer coefficients under different flow conditions. The functions are generated based on the experimental dependences of the Reynolds number and the Colburn factor or the Reynolds number and the Prandtl number for the Nusselt number.
constant heat transfer coefficient
If for the parameter Gas-wall heat transfer coefficient the value is set Constant heat transfer coefficient, then the heat transfer coefficient is a constant and the Nusselt number is not used in calculations. Use this parameterization as a simple approximation for gas flows limited by the laminar regime.
conditions for pipes
If for the parameter Gas-wall heat transfer coefficient The value of Correlation for flow inside tubes is set, then the Nusselt number depends on the flow mode.
For turbulent flows, its value changes proportionally to the Reynolds number and is calculated using the Gnelinsky ratio.:
where
-
— the Reynolds number;
-
— the Nusselt number;
-
— Prandtl’s number;
-
— the coefficient of friction, which is the same as the coefficient used in the calculations of pressure loss in the pipe.
For laminar flows, the Nusselt number is a constant. Its value can be obtained from the parameter Nusselt number for laminar flow heat transfer, :
Table data for determining the Colburn factor as a function of the Reynolds number_
If for the parameter Gas-wall heat transfer coefficient the value is set 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 — this is a measure of proportionality between the Reynolds, Prandtl and Nusselt numbers:
where — this is the Reynolds number based on the hydraulic diameter for heat transfer, , and at the minimum free flow area in the channel,
Table data for determining the Nusselt number as a function of the Prandtl and Reynolds numbers_
If for the parameter Gas-wall heat transfer coefficient the value is set Tabulated data - Nusselt number vs. Reynolds number and Prandtl number, then tabular data is used to determine the Nusselt number as a function of the Prandtl and Reynolds numbers. Linear interpolation is used to determine the values between the reference points.
The Nusselt number is a function of and , therefore , the parameters Reynolds number vector for Nusselt number, Prandtl number vector for Nusselt number, and Nusselt number table, Nu(Re,Pr) define the reference points of the table:
The Reynolds tabular 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 |
#
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.
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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 |
#
Gas volume —
total volume of coolant 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.
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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.
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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.
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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.
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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.
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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.
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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 in 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.
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| Default value |
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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.
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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 look-up 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 |