# AcuHeatBalance

Compute the total surface integrated heat flux, surface integrated convective temperature flux and integrated radiation heat flux from an AcuSolve solution database.

## Syntax

acuHeatBalance [options]

## Type

AcuSolve Post-Processing Program

## Description

AcuHeatBalance is a post-processing utility that uses the AcuSolve solution database to compute the absolute and relative energy balance within the simulation. The energy balance can be computed by summing the surface integrated heat flux values obtained on the walls with the convective temperature flux obtained on the inflow/outflow. The application also reports the integrated temperature, radiation heat flux and mass flux values for the requested element sets.

The primary input for acuHeatBalance is provided with the -cnns flag, referring to the parent element connectivity name, or element set name. By default, the cnns flag is set to _all, which will query all the element sets associated with the simulation to determine the surfaces available and their energy related outputs through osi. The selected surface integrated heat flux on all boundary conditions of type wall is summed to provide the total heat loss/gain due to conduction and radiation. The selected surface integrated convective temperature flux on all boundary conditions of type inflow or outflow is summed to provide the total heat loss/gain due to convection. The quantities are summed to provide an indication of how well the total heat transfer is balanced within the system. For an ideal simulation, the sum of heat flux plus the sum of the inflow/outflow convective temperature flux should be equal to zero. The following relationship is used to determine the percent balance within the system. (1)

Where, ${\stackrel{˙}{Q}}_{i}$ is the heat flux and convective temperature flux for the walls and inlets/outlets, respectively. $Nw$ is the total number of surfaces defined with the wall boundary condition (fluid and solid mediums if requested), $Ninlets$ is the total number of surfaces defined with the inlet boundary condition, and $Noutlets$ is the total number of surfaces defined with the outlet boundary condition.

Note that for simulations where both fluid and solid element sets are present, the sum of heat flux on the walls $\left({\sum }_{i=1}^{{N}_{w}}{\stackrel{˙}{Q}}_{i}\right)$ will contain contributions from both mediums. This may give the indication that the balance is not close to zero. In this case, only the contribution from the fluid element set should be considered by specifying the -cnns flag appropriately.

AcuHeatBalance can only be used on problems were the steady state solution for the Reynolds Averaged Navier-Stokes is specified. The final value of the steady state run is used for the balance and is written to the output files.

In the following, the full name of each option is followed by its abbreviated name and its type. For a general description of option specifications, see Command Line Options and Configuration Files. See below for more individual option details:
help or h (boolean)
If set, the program prints a usage message and exits. The usage message includes all available options, their current values, and the place where each option is set.
problem or pb (string)
The name of the problem is specified via this option. This name is used to generate input file names and extracted surface file names.
run_id or run (integer)
Number of the run in which the translation is requested. If run_id is set to 0, the last run in the working directory is assumed.
element_sets or cnns (string)
Comma-separated list of element_sets. These are the user-given names specified as the user-given name of the ELEMENT_SET commands in the input file. If the element_sets option is set to _all, all output sets are included into the heat balance computation (default).
periodic or p (boolean)
If this option is set to TRUE, the application will allow the balance computation to include the contribution of convective temperature flux from surfaces that are specified with the periodic boundary condition.
query or q (boolean)
If this option is set to TRUE, the application will run in query mode. Query mode will simply print a list of element sets and associated surfaces that are available for heat balance computation. The list of surfaces is queried from the list of surface_output sets available in the solution database.
verbose or v (integer)
Set the verbose level for printing information to the screen. Each higher verbose level prints more information. If verbose is set to 0, or less, only warning and error messages are printed. If verbose is set to 1, basic processing information is printed in addition to warning and error messages. This level is recommended. verbose levels greater than 1 provide information useful only for debugging.

## Examples

Consider the computation of the heat transfer within a two-dimensional annulus, where no inlet or outlet surfaces are considered:
acuHeatBalance
The following will be printed to the standard output of the terminal, as an example:
acuHeatBalance:
acuHeatBalance:  Opening the AcuSolve solution data base
acuHeatBalance:  Problem <annulus_heat> directory <ACUSIM.DIR> runId <1>
acuHeatBalance:
acuHeatBalance:        Successfully Opened Problem:     annulus_heat
acuHeatBalance:        Successfully Opened Run Id:           1
acuHeatBalance:        Found Requested Element Sets from cnns string: 1
acuHeatBalance:        Element Set: Fluid     Surface Set: ID
acuHeatBalance:        Element Set: Fluid     Surface Set: Max_Z
acuHeatBalance:        Element Set: Fluid     Surface Set: Min_Z
acuHeatBalance:        Element Set: Fluid     Surface Set: OD
acuHeatBalance:        Element Set: Fluid     Surface Set: Symmetry
acuHeatBalance:
acuHeatBalance:   Writing to file:  annulus_heat.Individual.Balance.dat
acuHeatBalance:   Writing to file:  annulus_heat.Total.Balance.dat
acuHeatBalance:   Conduction Only
acuHeatBalance:   Walls Heat Flux Sum = -0.000120977209668 W
acuHeatBalance:
acuHeatBalance:   Program complete

Running AcuHeatBalance produces two output files containing the simulated contribution of heat flux from the requested surface sets called <annulus_heat>.Individual.Balance.dat and <annulus_heat>.Total.Balance.dat.

The file called <annulus_heat>.Individual.Balance.dat contains the following columns (area removed for brevity), reporting the individual surface output quantities for each surface:
Table 1.
ElementSet SurfaceSet SBCType Temperature Heat Flux Convective Temperature Flux Mass Flux
Fluid ID wall 373.0 -0.15 0.0 0.0
Fluid Max_Z symmetry 0.0 0.0 0.0 0.0
Fluid Min_Z symmetry 0.0 0.0 0.0 0.0
Fluid OD wall 327.0 0.15 0.0 0.0
The file called <annulus_heat>.Total.Balance.dat contains the following columns, reporting the sum of all the requested surfaces:
Table 2.
Temperature Avg Heat Flux Total Conv Temp Flux Total Mass Flux Total
350 -1.2E-04 0 0
Consider the computation of the heat transfer within a two-dimensional channel, where the convective temperature flux from the inlet to outlet drives the wall heat flux:
acuHeatBalance -cnns Fluid
acuHeatBalance:
acuHeatBalance:  Opening the AcuSolve solution data base
acuHeatBalance:  Problem <channel_laminar_heat> directory <ACUSIM.DIR> runId <1>
acuHeatBalance:
acuHeatBalance:        Successfully Opened Problem:     channel_laminar_heat
acuHeatBalance:        Successfully Opened Run Id:           1
acuHeatBalance:        Found Requested Element Sets from cnns string: 1
acuHeatBalance:        Element Set: Fluid     Surface Set: Inlet
acuHeatBalance:        Element Set: Fluid     Surface Set: Outlet
acuHeatBalance:        Element Set: Fluid     Surface Set: Symm_MaxZ
acuHeatBalance:        Element Set: Fluid     Surface Set: Symm_MinY
acuHeatBalance:        Element Set: Fluid     Surface Set: Symm_MinZ
acuHeatBalance:        Element Set: Fluid     Surface Set: Wall
acuHeatBalance:
acuHeatBalance:   Writing to file:  channel_laminar_heat.Individual.Balance.dat
acuHeatBalance:   Writing to file:  channel_laminar_heat.Total.Balance.dat
acuHeatBalance:   Convective Temperature Flux Inlet + Outlet=51.2592664092 W
acuHeatBalance:   Walls Heat Flux Sum = -52.0100414952 W
acuHeatBalance:   Balance: Convective Flux + Walls Heat Flux = -0.750775086036 W
acuHeatBalance:   Percent Difference = 1.46466217453 %
acuHeatBalance:   Program complete
In this case, the file called channel_laminar_heat.Individual.Balance.dat contains the following columns, reporting the individual surfaces:
Table 3.
ElementSet Surface Set SBC Type Temperature Heat Flux Convective Temperature Flux MassFlux
Fluid Inlet inflow 294.5 0.8 -1717.7 -0.0059
Fluid Outlet outflow 303.4 0.0 1768.9 0.0059
Fluid Symm_MaxZ slip 0.0 0.0 0.0 0.0000
Fluid Symm_MinY slip 293.1 0.0 0.0 0.0000
Fluid Symm_MinZ slip 0.0 0.0 0.0 0.0000
Fluid Wall wall 348.2 -52.0 0.0 0.0000
The file called channel_laminar_heat.Total.Balance.dat contains the following columns, reporting the integrated sum of all the requested surfaces:
Table 4.
Temperature Avg Heat Flux Total Conv Temp Flux Total Mass Flux Total
348.15 -52.0 51.2 0.0
To simply query the solution database, use the following command:
acuHeatBalance -q

acuHeatBalance:
acuHeatBalance:  Opening the AcuSolve solution data base
acuHeatBalance:  Problem <annulus_heat> directory <ACUSIM.DIR> runId <0>
acuHeatBalance:
acuHeatBalance:        Successfully Opened Problem:     annulus_heat
acuHeatBalance:        Successfully Open Run Id:           1
acuHeatBalance:        Total Number of Element Sets:      1
acuHeatBalance:        Element Set Name:                  Fluid
acuHeatBalance:
acuHeatBalance:        Total Number of Surface Sets:      5
acuHeatBalance:        Surface Set Name:                  ID
acuHeatBalance:        Surface Set Name:                  Max_Z
acuHeatBalance:        Surface Set Name:                  Min_Z
acuHeatBalance:        Surface Set Name:                  OD
acuHeatBalance:        Surface Set Name:                  Symmetry
acuHeatBalance:

The application will report the amount of heat transfer on a specific surface due to radiation when the radiation_output command is active on a given surface set.

The following example demonstrates the use of the tool on a database containing radiaition output with no inlets or outlets. The application provides the same previously discussed sum, which includes contributions from radiation. Surfaces contributing to the radiation heat transfer are added to the ouput files individually and are summed for clarity. Note that the sum of a radiation problem should be nearly zero.
acuHeatBalance –q

acuHeatBalance:
acuHeatBalance:  Opening the AcuSolve solution data base
acuHeatBalance:  Problem <sphere_radiation> directory <ACUSIM.DIR> runId <0>
acuHeatBalance:
acuHeatBalance:        Successfully Opened Run Id:           1
acuHeatBalance:        Found Requested Element Sets from cnns string: 3
acuHeatBalance:        Element Set: Inner     Surface Set: Inner_Inner_r1
acuHeatBalance:        Element Set: Inner     Surface Set: Inner_Inner_ri
acuHeatBalance:        Element Set: Outer     Surface Set: Outer_Outer_r2
acuHeatBalance:        Element Set: Outer     Surface Set: Outer_Outer_ro
acuHeatBalance:        Found Radiation Output in Database
acuHeatBalance:
acuHeatBalance:   Radiative Heat Flux Sum = -3.15662873618e-09 W
acuHeatBalance:   Walls Heat Flux Sum = 0.00224294477922 W
acuHeatBalance:
acuHeatBalance:   Program complete
Table 5.
Element Set Surface Set SBC Type Temperature Heat Flux Convective Temperature Flux MassFlux ORI Temperature ORI HeatFlux
Inner Inner_r1 wall 578 -140 0.0 0.0
Inner Inner_ri wall 300 140 0.0 0.0