IECHO(keyword)

IECHO

IECHO

A parameter that specifies whether or not the input data is to be echoed into the output file. The convention is as follows:

 

N -- No Echo

Y -- Echo

 

Notice: This option may be overridden by using the $ECHYO_ON or $ECHO_OFF commands. If the $ECHO commands are used, they must begin in column 1 of the input data file. There is no limit to the number of these $ECHO commands that may be used, and they may be used on any line of the input data file. These commands are especially useful for selectively suppressing the echo of the QINDAT file into the QOUTDAT.

ISCALE(keyword)

ISCALE

ICCALC(keyword)

ICCALC

TLABEL(keyword)

TLABEL

ISCALE

Alphabetic entry that corresponds to the output temperature scale to be used. Regardless of the temperature scale being used to perform the calculations, the temperatures may be output in Celsius, Fahrenheit, Kelvin, or Rankine by entering the appropriate character for ISCALE. The convention is as follows:

 

C -- Celsius

F -- Fahrenheit

K -- Kelvin

R -- Rankine

ICCALC

Alphabetic entry that corresponds to the temperature scale to be used to perform all calculations (e.g., evaluation of temperature-dependent properties, evaluation of temperature dependent heat source/sink functions). The same temperature scale codes that are shown above for ISCALE are used for ICCALC.

Regardless of the scale specified for ICCALC, thermal radiation problems will automatically use correct absolute temperature scales when evaluating heat flows across thermal radiation resistors. Specifically, if ICCALC is specified as C, QTRAN will use K when evaluating the potentials of 6 * T4 at each end of the thermal radiation resistor and will use R if ICCALC was specified as F. Resistor material properties will still be evaluated using the scale specified by ICCALC.

TLABEL

A 10 character entry that corresponds to the time units that are being used for the simulation (e.g., seconds, minutes, hours, fortnights, etc.). TLABEL is not used for any internal units conversions or anything else except that the 10 characters will be printed out after TIME values with the output data. TLABEL may be left blank.

HIPOT (keyword)

HIOPT

HSOL

NTBHUP

HIOPT

Run-option parameter selects one of the following three options:

0 - No flow network solution.

1 - Flow network solution only.

2 - Flow network coupled to the thermal solution.

All hydraulic solutions are quasi steady-state. If a transient run is being made, whenever the hydraulic solution is executed it will be a steady-state solution with the thermal conditions at the beginning of the hydraulic solution being used for the flow network evaluation.

HSOL

Parameter that selects a solution option default SOL is 2 (Direct solver option). Currently, the only direct solution option SOL=2 is supported.

NTBHUP

Usage is dependent on the thermal option selected. If a steady-state thermal solution is being executed, then the hydraulic network solution is recomputed every NTBHUP thermal iterations. For a transient thermal solution, the hydraulic solution is updated every NTBHUP time steps. The hydraulic solution is highly nonlinear and can require significant computer resources. By computing mass flow rates (hydraulic network solution) less often, the overall solution is speeded up without any significant loss of accuracy as long as the flow properties (viscosity, density, etc.) are not a strong function of temperature.

There is a strong coupling between the hydraulic and thermal solutions if buoyancy is included in the hydraulic solution. In this case the two solutions should be updated every iteration by setting NTBHUP to 1.

IOPT (keyword)

IOPT

SOL

NITBUP

MFLIPF

IOPT

Run-option parameter that selects one of the following six calculation sequences (see Section 5.2.6 for an explanation of TSTART and TSTOP):

 

A data check only. Input data will be read and echoed, but no calculations will be performed.

A transient run from initial conditions.

A transient run after initial-steady state calculations have been performed. All time dependent functions are calculated for the initial steady-state calculation using time = TSTART.

A steady-state run only. Time-dependent functions will be evaluated using time = TSTART.

A transient run from initial conditions, followed by a steady-state run from the final conditions. Time-dependent functions will be evaluated using time = TSTOP.

A steady-state run with the time-dependent functions for the steady-state run evaluated at time = TSTART, followed by a transient run, followed by a final steady- state run with the time-dependent functions evaluated at time = TSTOP.

SOL

Parameter that chooses a thermal solution option.

 

Standard SNPSOR solution algorithm, default.

Modified SNPSOR algorithm. The modified SNPSOR algorithm precomputes the values of the conductive resistors, and updates them every NITBUP iterations. By computing the conductive resistors less often, the solution is typically speeded up without any significant loss of accuracy as long as the thermal conductivity associated with the resistors is not rapidly changing.

 

Direct solver using Choleskis method. The direct solver is coupled with the standard SNPSOR solution which is always executed after a direct solution to verify that all nonlinearities have been resolved. How many SNPSOR solutions are performed before a direct solution is repeated is controlled by NITBUP. The direct solver cannot be used with problems that include phase change. Also, the direct solver does not provide the advantages for transient cases compared to the gains that can be made with steady-state problems. Care should be exercised with transient cases that the time steps do not become so large that history effects will be lost even on those cases where boundary conditions and properties are constant. The direct solver is best suited to linear problems which have small bandwidths on the extremely stiff problem.

NITBUP

The Number of Iterations Between Updates. What is updated is dependent on the solution option. If the standard solution is used (SOL = 0), then all nodes that may have been eliminated from the solution because they satisfied the second transient convergence criteria (EPSIT2) are included in the solution every NITBUP iteration. All nodes are evaluated after the solution has converged to guarantee that they are within the desired convergence tolerance. A value between IMIN / 2 and IMIN is recommended. The default value is 1000. This value has no effect for a standard solution, steady- state case. For the modified solution (SOL = 1), NITBUP is the frequency that the conductive resistors are update for both the steady-state and transient solutions. The best value for NITBUP is, of course, problem dependent. For many transient problems, it is sufficient to update the conductive resistors only once per time step, to specify a NITBUP value greater than the value of IMAX (IMAX is the maximum number of iterations allowed per time step). Note that no matter what value is given to NITBUP, QTRAN will automatically recompute the conductive resistor values at the beginning of each time step. For steady-state problems, experimentation with your specific problem is the rule of the day. Values of NITBUP between 10 and 100 are usually appropriate. The default NITBUP value is 0 (update every iteration). If the direct solver is used (SOL = 2), the NITBUP determines how many standard solutions (SNPSOR algorithm) are executed before another direct solution is performed. If material properties and boundary conditions are constant or are weak functions of temperature, the direct solution should be able to calculate the exact answer in one or with very few iterations. In these cases, the NITBUP value should be one. If there are strong nonlinearities involved, such as high temperature radiation boundary conditions, then it is best to do several SNPSOR solutions before doing another direct solution. This gives very sensitive parts of the problem a chance to relax using a much faster solution method while still using a direct solution to carry along the stiff portions of the problem that require many SNPSOR type iterations. For the highly nonlinear case, NITBUP values between 5 and 10 are appropriate.

MFLIPF

The maximum number of over all solutions flip flops by the maximum temperature error before a bisection of all nodes is performed. The error must be less than three orders of magnitude of the allowable error about zero before it is considered a flip/flop condition. (Default value is 8.)

IMAX (keyword)

IMAX

IMIN(keyword)

IMIN

IMAXSS(keyword)

IMAXSS IMAXHS

ISSDMP(keyword)

ISSDMP

IMAX

Maximum number of iterations allowed for any given time step during transient runs. If the number of iterations exceeds IMAX without converging, the time step is decreased and convergence is attempted again. This will be repeated until convergence occurs with less than or equal to IMAX iterations. If zero is entered, QTRAN will supply a default value of 36.

IMIN

Minimum desired number of iterations required to achieve convergence on any given time step for transient runs. If the number of iterations does not equal or exceed IMIN iterations before convergence, the time step size is increased for the next integration step. If zero is entered for IMIN, QTRAN will supply a default value of 9. IMIN should be less than or equal to IMAX.

IMAXSS

Maximum number of iterations allowed for steady state calculations. If QTRAN does not achieve convergence within IMAXSS iterations, a message which states that convergence failed will be printed along with the current values of temperatures and heat fluxes. The program then terminates. If a zero is entered for IMAXSS, QTRAN will supply a default value of 2000.

IMAXHS

Maximum number of iterations allowed for the steady state hydraulic calculations.

ISSDMP

Number of steady-state iterations between print dumps. When a steady-state run is underway, QTRAN will print the results every ISSDMP iterations until the problem has converged. If zero is entered for ISSDMP, QTRAN will supply a default value of 2000.

DT(keyword)

DT

DTMIN

 

TSTART(keyword)

TSTART

 

 

TSTOP(keyword)

TSTOP

 

 

TSFMIN(keyword)

TSFMIN

 

 

TSFMAX(keyword)

TSFMAX

 

 

HYEPIS(keyword)

HYEPIS

HYHDEP

HYMDEP HYPREP

EPSISS(keyword)

EPSISS

 

 

EPSIT(keyword)

EPSIT

EPSIT2

 

PERTUR(keyword)

PERTUR

 

 

RELAXS(keyword)

RELAXS

IFSRLX

 

RLXSAT(keyword)

RLXSAM

RLXSAD

RLXSAU

RLXSRT(keyword)

RLXSRM

RLXSRD

RLXSRU

RLXSHT(keyword)

RLXSHM

RLXSHD

RLXSHU

RLXSCT(keyword)

RLXSCM

RLXSCD

RLXSCU

RLXSST(keyword)

RLXSSM

RLXSSD

RLXSSU

RELAXT(keyword)

RELAXT

IFTRLX

 

RLXTAT(keyword)

RLXTAM

RLXTAD

RLXTAU

RLXTRT(keyword)

RLXTRM

RLXTRD

RLXTRU

RLXTHT(keyword)

RLXTHM

RLXTHD

RLXTHU

RLXTCT(keyword)

RLXTCM

RLXTCD

RLXTCU

RLXTST(keyword)

RLXTSM

RLXTSD

RLXTSU

BETA(keyword)

BETA

BETMIN

BETMAX

DELMAX(keyword)

DELMAX

MINTMP

MAXTMP

PCBAND(keyword)

PCBAND

CPDELT

 

GRAVTY(keyword)

GRAVTY

GO, GX, GY, GZ

 

SBC(keyword)

SBC

 

 

DCMF(keyword)

DCMF

 

 

DT

Initial time step used for transient calculations. DT will usually be adjusted during the course of a transient run by QTRAN to take advantage of easily followed transients or to ensure accuracy during more difficult transients. If 0.0 is entered for DT, QTRAN will set DT to a nonzero but very small number (e.g., 1.0E-30). This is not recommended, but one should not be afraid to start with small time steps to give QTRAN the opportunity to follow a strong transient. For example, if the initial value of DT was set to 1.0D-4, it would take 16 calculation intervals to grow to 1.0 if the growth factor on the time step was 1.8 and the transient was mild enough to enable a time step of 1.0 units. If the initial value of DT was 1.0D-5 or 1.0D-6, it would only take 20 or 24 calculation intervals respectively to reach a DT value of 1.0.

The time step, DT, must be greater than 1.0E-10 * TSTOP. If a problem requires a time step smaller than this, it is probably best broken into multiple parts with restarts and corresponding adjustments to the IMIN and IMAX parameters to fit the regions of the problem that require the small and large time steps.

DTMIN

The minimum allowed time step to be used for any calculation interval. Default is 1.0E-30. This value should be changed only as a last resort to get a difficult problem to run or when the user wants to force fixed time points regardless of errors that may be introduced because of lags in response to a given boundary condition.

TSTART

Starting time used for transient runs. It is also used to evaluate time-dependent functions if initial steady-state calculations are being performed.

TSTOP

Stop time for the program run. It is also used to evaluate time-dependent functions if a steady-state run is being performed after a transient run.

TSFMIN

Time step multiplier that is used to decrease the time step size in case convergence has failed after more than IMAX (see Section 5.2.5) number of iterations. TSFMIN should normally be between 0.0 and 1.0. A recommended value is TSFMIN = 0.6. To run with a constant time step, simply set TSFMIN and TSFMAX (see following TSFMAX definition) to 1.0.

TSFMAX

Time step multiplier that is used to increase the time step size in case convergence has occurred in less than IMIN (see Section 5.2.5) number of iterations. TSFMAX will not increase the time step size to a value greater than DTMAX (see Section 5.2.8.1). TSFMAX should normally have a value greater than 1.0. A suggested value is TSFMAX = 1.8, but a larger value may be used to allow a rapid increase in the time step, or use a smaller value to limit the perturbation to the system when time steps are increased. To run with a constant time step, simply set both TSFMIN (see previous TSFMIN definition) and TSFMAX to 1.0. The IMIN, IMAX, TSFMIN, and TFSMAX parameters all work together. Care should be taken so not to get into the condition that the DT increment is increased too much so that it will be decreased in the next time step. The product of TSFMIN and TSFMAX should be greater than one so that the problem will experience some increase in time step even if the time step is cut down in the next calculation increment.

HYEPIS

Convergence criteria used by flow network solver. Static pressure, head differential across an element (pressure + gravity head + buoyancy head, etc.) and mass flow rates have to converge within HYEPIS before the flow solution is declared converged. HYEPIS is an absolute value and is used for all three parameters being checked. Care should be exercised in selecting this value to be sure that unit and the range of values are properly represented. The mass flow rate typically will be a much smaller value than the pressure and selecting a value consistent with the pressure will have no direct effect on the mass flow rate convergence criteria; however, if the convergence criteria was selected to operate on the mass flow rate, it would probably be too restrictive to enable convergence of the differential head.

HYHDEP

Convergence criteria used by the flow network solver as an independent check on the head differential across an element.

HYMDEP

Convergence criteria used by the flow network solver as an independent check on the mass flow rate at each hydraulic node.

HYPREP

Convergence criteria used by the flow network solver as an independent check on the pressure at each hydraulic node.

EPSISS

Steady-state convergence criteria that is used by QTRAN. This value is the estimated maximum error of the worst (least converged) node in the system, and is NOT an iterative delta as used by many codes. For example, to converge to the nearest 0.001 degrees, enter 0.001 for EPSISS and QTRAN will iterate until its estimate of the error of the worst node in the system is 0.001. Note that this convergence criteria is typically 10 to 100 times more severe than the criteria used in codes which rely on an iterating delta. For example, a value of 0.001 for EPSISS is frequently equivalent to a CINDA convergence criteria of at least 0.0001 to 0.00001. It should be especially noted that while EPSISS is directly related to the system error, the iterative delta convergence schemes (such as are used in CINDA) are truly only related to the convergence rate of a particular problem and not to the problem error. It is best to conservatively run with EPSISS = 0.0001 and obtain good results; however, with EPSISS = 0.1, reasonable answers on many problems may be obtained.

EPSIT

Transient convergence criteria that is used by QTRAN (see EPSISS above). A recommended value is EPSIT = 0.0001. Experience seems to indicate that this is a very good value for most problems. Larger values of EPSIT do not make transient problems run as much faster as you might think, and smaller values seem to be overkill. The idea seems to be that you need to converge a system of equations to within the truncation error of the basic time integration scheme. Convergence beyond this truncation error is probably an exercise in fooling yourself. Conversely, if the problem fails to converge to within the truncation error of the integration scheme, the residual noise (error) in the solution seems to hinder the predictor equation to the point where the poorer predicted temperatures slow things down more than was gained by the looser convergence criteria.

EPSIT2

Optional modification to the transient convergence criteria. It can be thought of as a “cut-out” convergence criteria that can be used to speed convergence. Specifically, for transient problems, QTRAN will compare each nodes iterative error to EPSIT2. If that node’s last iterative error was less than EPSIT2, that node is cut out of the iteration sequence for the remainder of the time step. This allows QTRAN to iterate only on those nodes that are still changing significantly. Please note that the EPSIT2 value should be SIGNIFICANTLY smaller (at lease two or three orders of magnitude) than the EPSIT value. Remember, a large number of very small changes can add up over a period of time, so make sure that EPSIT2 is significantly smaller than EPSIT. The default value for EPSIT2 is 0.0 (this gives the standard QTRAN SNPSOR algorithm).

PERTUR

Perturbation parameter that is used to evaluate derivatives for Newton’s Second-Order Method used by QTRAN. PERTUR corresponds directly to the traditional dx that is used in classical central difference schemes to evaluate derivatives. In this case, PERTUR is used to evaluate both 1st-Order and 2nd-Order derivatives. If the value of PERTUR is grossly too large, the error in the evaluation of the derivatives may cause convergence to be slow. Conversely, if the value of PERTUR is too small (especially for radiation calculations), the perturbations caused by PERTUR may be so small that they are swallowed by round-off error, causing the derivatives to be evaluated as zero and subsequent nonconvergence. If this problem occurs, you should experiment with different PERTUR values. A recommended PERTUR value is 0.01. Smaller values may be used for mass flow and convection problems, while “hot” radiation problems of several thousand degrees Kelvin may require values of 1.0 or greater. A value that is too large or too small may also cause steady-state convergence to fail. In general, problems that are fairly linear in the temperature variable (i.e., temperature-independent material properties and convection correlations with no radiative nodes) are relatively insensitive to larger values of the PERTUR parameter and will tolerate small PERTUR values. Problems that are strongly nonlinear in the temperature variable (e.g., hot radiation problems) are generally more sensitive to the size of the PERTUR variable and may not tolerate extremely small PERTUR values due to the round-off phenomenon. Note that despite all of the above warnings, PERTUR values of 0.1 to 0.01 rarely fail in practice.

RELAXS

Steady-state relaxation parameter. RELAXS is used only for steady-state calculations, and its sole function is to speed convergence (i.e., to reduce the number of iterations required for convergence to a certain accuracy). The absolute value of RELAXS should be between, but not including, 0.0 and 2.0. Positive values invoke QTRAN’s adaptive relaxation algorithm, whereas negative values of RELAXS inhibit the adaptive algorithm. Normally, the value entered for RELAXS should be +1.0, thus allowing QTRAN’s adaptive relaxation algorithm to function. Values with magnitudes greater than 2.0 will cause the algorithm to diverge, while values with magnitudes less than 1.0 may increase the radius of convergence at the expense of the convergence rate. If the adaptive algorithm is enabled, QTRAN begins iterations with your RELAXS value as the initial guess of the relaxation parameter. It is better to guess low at this value because QTRAN’s adaptive algorithm will converge more quickly to the optimal value from below than from above. Furthermore, if the initial guess at the temperature distribution is very poor (and this is typically the case), a value of RELAXS = +1.0 will allow QTRAN to smooth the system slightly before using over relaxation.

 

This smoothing is sometimes necessary for strongly nonlinear systems in order to achieve convergence. The total amount of work required for a steady-state solution is extremely dependent on this parameter. It is not unusual for an optimally over-relaxed problem to run in 1/30th the time of a nonreligious (RELAXS = -1.0) problem. QTRAN’s adaptive algorithm takes the guesswork out of what this value should be.

IFSRLX

A flag that indicates how the relaxation parameters are to be applied to the system of equations being solved. Three options are available. If the IFSRLX=0 option is used, then the relaxation parameter applies to all nodes in the system equally. All nodes are searched each time step, the maximum error is determined, and the relaxation and convergence factors are determined based on the maximum error of the system regardless as to what type of boundary condition is applied to the node. The IFSRLX=1 option applies relaxation and convergence factors based on the type of node and boundary condition that is present at the node. A hierarchy is established as to the type of boundary condition present at the node. This order is from advection, radiation, convection down to conduction. If any node has advection applied, then the advection relaxation parameters will apply even if there is also radiation and or convection at the same node. Advection can destroy the diagonal dominance of the matrix and as such it may be desirable to set the relaxation parameters to force under relaxation for these nodes so that the circle of converge of the problem can be increased. Similarly, the radiation nodes will probably be the most likely to exhibit large fluctuations, therefore, it is not desirable for the relaxation parameters to increase as rapidly for these nodes as for the nodes that exhibit straight conduction. This option, which allows for these groupings, is the recommended option. The third option, IFSRLX=2, is to have the relaxation parameters calculated on a node-by-node basis. This option will usually give the tightest converged solution. The convergence factor is also calculated individually for each node and a node that may not have the largest error could be changing slower than the node that had the greatest error. Thus, the convergence factor could be much larger. The system error is the product of the iteration error and the convergence factor. As a result, the system error determined on a node-by-node basis could be greater than that determined for the system or group methods. The error criteria can probably be relaxed, if the node-by-node relaxation option is used compared to the group or system option.

RLXSAM

Maximum steady-state relaxation parameter that is to be used with all advection nodes. Values input must be greater than 1.0 and less than 2.0

Notice: The relaxation variables discussed below and their association to the input file, Keyword, is shown in the Control Parameters, 236.

RLXSAD

Advection steady-state relaxation damping factor. Based on several conditions, the relaxation parameters are recalculated. The new relaxation parameters are compared to the old values and the actual amount of change is reduced according to the damping multiplier. For example, suppose that the new relaxation factor was calculated to be 1.860 and the old one was 1.0. If the damping factor was 0.95, then the actual relaxation factor defined at this calculation step would be 1.817. In the early stages of a solution, the iterative delta is probably the largest. This may be the time that it is not desirable to over relax, particularly with advection. By using small damping factors, the degree of over relaxation is reduced but will be allowed to approach its optimum value as the solution continues and is usually when the solution is better behaved. In problems where advection is causing convergence problems, it may be desirable to reduce this parameter to 0.05.

RLXSAU

Steady-state multiplier used with all advection nodes. All multipliers are applied by type of node and boundary conditions regardless of the application option that is specified. This parameter is used to implement under relaxation. The relaxation parameter will always be calculated between the values of 1.0 and 2.0, but when they are applied to the iterative delta, the RLXSAU multiplier is included. Thus, if the relaxation parameter was 1.8 and the multiplier 0.3, the effective relaxation parameter would be 0.54 or an under relaxed state. Under-relaxation or multipliers less than 1.0 should only be used in those cases where the node-by-node application of the relaxations parameters has failed to yield convergence. Note that the relaxation parameters specified in the output or status file reflect the multipliers and are only applied to the actual temperature change.

RLXSRM

Maximum steady-state radiation relaxation value allowed.

RLXSRD

Steady-state radiation relaxation damping factor.

RLXSRU

Steady-state radiation relaxation factor multiplier.

RLXSHM

Maximum steady-state convection relaxation value allowed.

RLXSHD

Steady-state convection relaxation damping factor.

RLXSHU

Steady-state convection relaxation factor multiplier.

RLXSCM

Maximum steady-state conduction relaxation value allowed.

RLXSCD

Steady-state conduction relaxation damping factor.

RLXSCU

Steady-state conduction relaxation factor multiplier.

RLXSSM

Maximum steady-state system relaxation value allowed.

RLXSSD

Steady-state system relaxation damping factor.

RLXSSU

Steady-state system relaxation factor multiplier.

RELAXT

Transient solution relaxation parameter which is similar to the previous RELAXS parameter. RELAXT is used only for transient calculations. QTRAN’s adaptive relaxation algorithm may be selected in the same manner as RELAXS, and for transient calculations may easily half the solution time when compared to a fixed relaxation scheme. Whenever the time step changes in magnitude, or after a direct solution, the relaxation parameter is reset to 1.0. All the associated relaxation parameters that were discussed for the steady-state case can be applied independently to the transient part of the solution. These parameters are listed below.

IFTRLX

A flag that indicates how the relaxation parameters are to be applied to the system of equations being solved. Three options are available. If the IFTRLX=0 option is used, then the relaxation parameter applies to all nodes in the system equally. The IFTRLX=1 option applies relaxation and convergence factors based on the type of node and boundary condition that is present at the node. The third option, IFTRLX=2, is to have the relaxation parameters calculated on a node-by-node basis.

RLXTAM

Maximum transient relaxation parameter that is to be used with all advection nodes.

RLXTAD

Advection transient relaxation damping factor.

RLXTAU

Transient multiplier used with all advection nodes.

RLXTRM

Maximum transient radiation relaxation value allowed.

RLXTRD

Transient radiation relaxation damping factor.

RLXTRU

Transient radiation relaxation factor multiplier.

RLXTHM

Maximum transient convection relaxation value allowed.

RLXTHD

Transient convection relaxation damping factor.

RLXTHU

Transient convection relaxation factor multiplier.

RLXTCM

Maximum transient conduction relaxation value allowed.

RLXTCD

Transient conduction relaxation damping factor.

RLXTCU

Transient conduction relaxation factor multiplier.

RLXTSM

Maximum transient system relaxation value allowed.

RLXTSD

Transient system relaxation damping factor.

RL XTSU

Transient system relaxation factor multiplier.

BETA

Explicit/implicit ratio variable that is used to control the amount of explicitness and implicitness of transient integration solutions. If β is negative, QTRAN’s optimizing algorithm is disabled and the value that you entered for β will be used for all nodes which have capacitors assigned to them (zero capacitance nodes are not integrated, but are instead computed directly). A value of β = 0.0 yields a fully-explicit solution (forward Euler method), β = -1.0 yields a fully-implicit solution (backward Euler method), and anything in between yields a weighted average. If the recommended value β = +1.0 is used (or any positive number significantly greater than zero), QTRAN computes its own optimized value for β on a node-by-node basis. The optimized value also means that some nodes are at times run completely explicitly, and this mixture of explicit/implicit integration has yielded speed increases of 3 to 4 on some test problems. Also note that if a node is undergoing a phase change, the node is automatically integrated fully implicitly for the duration of the phase change activity of that node. Note that except for performing comparison benchmark tests of the algorithms, always run with β = 1.0. No case has yet been found where this has proven to be a problem. There seems to be no motivation to run with any other β value except possibly to verify that QTRAN’s implicit algorithm actually works. Solution accuracy and run times are normally fairly independent of the β value chosen, as long as a b value is chosen by you or by QTRAN that results in a stable solution.

BETMIN

Minimum allowable value of the β parameter. This gives more control over the degree of explicitness or implicitness desired. Explicit solutions are stable if linear properties are present, but even for this case, the transient may exhibit oscillations. If the material properties are highly nonlinear, limit the explicit calculations. By specifying a BETMIN, the nodes that are run explicitly can be limited while allowing the explicit/implicit weighting function to do its optimization.

BETMAX

Maximum allowable value of the β parameter.

DELMAX

Maximum allowed temperature change per iteration. If an iterative temperature change is calculated with a larger magnitude than DELMAX, the sign is kept but the magnitude is limited to DELMAX. If 0.0 is entered for DELMAX, a default value of DELMAX = 1000.0 will be used. DELMAX is used as a last-ditch effort to help force convergence to occur for the extremely rare problems for which QTRAN’s SNPSOR algorithm may otherwise fail. Normally, use the default value for DELMAX of 1000.0 by entering a 0.0 for DELMAX.

MINTMP

Minimum allowed temperature of a problem. In some cases, especially after strong perturbation in boundary conditions, explicit calculations or initial prediction can extrapolate the solution to unreasonable values. By specifying minimum and maximum values for the solution, any node whose value is extended beyond the limits of the solution will be declared to be solved by fully implicit means and the new guess in node temperature will be MINTMP. Care must be exercised that the value of MINTMP is not within the limits that can be expected for normal numerical oscillation of the solution.

MAXTMP

Maximum allowed temperature of a solution.

PCBAND

Temperature interval over which phase changes will be smeared. If set to 0.0 or less, a value of 1.0 degrees will be used. The smaller the value of PCBAND that is used, the more accurate the answer will be at the expense of more computation. Phase change begins at the phase change temperature minus PCBAND and is completed at the phase change temperature plus PCBAND. Phase change begins at the phase change temperature minus PCBAND and is completed at the phase change temperature plus the PCBAND.

CPDELT

Temperature integration step size used to evaluate an integrated average of the specific heat across a time step. If the specific heat is highly variable (e.g., a spike or other discontinuity exists in the Cp vs. temperature curve), set CPDELT to a fraction of the width of the spike. The calculated temperature change during a time step is divided by CPDELT to determine the number of points that the specific heat is to be evaluated. The specific heat is the average of all evaluations at each temperature point determined by CPDELT and is evaluated independently for each node, at each iteration for each time step. If CPDELT is greater than the temperature change, two points - the beginning and resultant temperature - will be used each time step to determine the specific heat. This is the default if CPDELT is left blank.

GRAVTY

Gravitational constant used with turbine, pump head calculation and for required internal units conversions. The default value is dependent on the ICCALC option. If Metric or an English temperature is specified, 9.80665 meters / second / second or 32.1741 feet / second /second respectively is used.

GX

Positive value indicates that gravity is working against a positive x direction. Default is 0.0.

GY

Positive value indicates that gravity is working against a positive y direction. Default is 0.0.

GZ

Positive value indicates that gravity is working against a positive z direction. Default is 0.0.

SBC

Stefan-Boltzmann thermal radiation constant. If SBC is entered as zero, QTRAN will set SBC to 5.6696D-08 W / (m2-K4) if ICCALC is in degrees K or C, and to     0.1712D-08 Btu/(hr-ft2-R4) if ICCALC is in degrees R or F.

DCMF

Discontinuous Macrofunction Flag. If set to 0, there is no effect. If set to 1, DCMF alerts QTRAN’s transient integration algorithm that one or more macrofunctions may be severely discontinuous in nature. QTRAN then uses a β value of 1.0 for nodes with macrofunctions assigned to them. Using β = 1.0 allows the transient integration algorithm to notice sharp discontinuities in dT/dt that occur in the middle or end of a time step and then forces QTRAN to use smaller time steps in the neighborhood of such a discontinuity.

IRQFLO (keyword)

RQFLO(1...9)

IRQFLO

Allows print/no print options to be selected for resistor, capacitor, and heat source macrofunction data in the system. Setting IRQFLO(i) to 1 causes QTRAN to print data for the i'th entry in the following list, while any other value causes no data to be printed for that item. The data is printed at the end of a steady state run, or at each print interval for a transient run. This data includes such things as resistor heat flow, conductance, capacitance, material property data, and others. The list of IDMNRF(i) items is as follows:

IRQFLO(1) -- Conduction Resistors

IRQFLO(2) -- Convective Resistors

IRQFLO(3) -- Gray Radiative Resistors

IRQFLO(4) -- Wavelength-Dependent Resistors

IRQFLO(5) -- Advective Resistors

IRQFLO(6) -- Capacitors

IRQFLO(7) -- Heat Source Macrofunctions

IRQFLO(8) -- Hydraulic Advection Resistors

IRQFLO(9) -- Hydraulic Capacitors

Since there can be a large amount of data (especially conductive and radiative resistor data), you normally should be selective about the volume of information that is requested.

NRFORM (keyword)

NRFORM

NRFORM

Format of the nodal results file.

0. Binary nodal results files.

1. ASCII nodal results files.

The flag that tells QTRAN whether to output the nodal results file is ASCII or binary. NRFORM=0 will give a binary file (default). NRFORM=1 will generate a text file.

IDMNRF (keyword)

DMNRF(1...18)

IDMNRF

Allows which items are to be put in the nodal results files. The first eight items plus fifteenth through the nineteenth into the nodal results files with the prefix designation NRnnn, ninth and tenth go to NPnnn type files, and the eleventh through the fourteenth go into NHnnn type files. The list of IDMNRF(i) items is as follows:

0. Denotes that parameter is not written to the results file.

1. Denotes that parameter is written to the results file.

IDMNRF(1)--Temperatures

IDMNRF(2)--Net nodal heat flow

IDMNRF(3)--Explicit stable time step

IDMNRF(4)--QMACRO function heat input

IDMNRF(5)--QBASE heat input to each node

IDMNRF(6)--Total heat input to each node

IDMNRF(7)--Temperature error

IDMNRF(8)--Average convective heat transfer coefficient

IDMNRF(9)--Nodal pressure from hydraulic solution

IDMNRF(10)--Net mass flow rate from hydraulic solution

IDMNRF(11)--Mass flow rate in hydraulic element

IDMNRF(12)--Differential head in hydraulic element

IDMNRF(13)--Fluid velocity in hydraulic element

IDMNRF(14)--Volumetric flow rate in hydraulic element

IDMNRF(15)--Applied Heat Flux

IDMNRF(16)--Convective Heat Flux - Note that the heat flux summary for plotting is only associated with the application region. The area is unknown or may not exist for the coupled node.

 

IDMNRF(17)--Radiate Heat Flux - As with convection the radiation for plotting is only associated with the application region. If one is working with an enclosure, specify a surface emissivity of 0.9999 to represent black bodies to get an accurate measure of what is happeniIDMNRF(15)--Applied Heat Fluxng at the surface.

IDMNRF(18)--Net Total Heat Flux

IDMNRF(19)--Surface Recession

IDMNRF(20)--Surface Recession Rate

 

Flag that determines what record gets put in the nodal results file. IDNMRF=0 implies that the record will not go to the nrf file while IDMNRF=1 implies that the record will be put out in the nodal results file. If all items are flagged, the following columns would represent the data in the different nodal results files:

NRnnn

Column 1 Temperature

Column 2 Net nodal heat flow

Column 3 Explicit stable time step

Column 4 QMACRO function heat input

Column 5 Qbase heat input into each node

Column 6 Total heat input into each node

Column 7 Temperature error

Column 8 Average convection heat transfer coefficient

Column 9 Applied heat flux

Column 10 Convective heat flux

Column 11 Radiate heat flux

Column 12 Net total heat flux

Column 13 Surface Recession

Column 14 Surface Recession Rate

NPnnn

Column 1 Pressure at a given node from the hydraulic solution

Column 2 Mass flow rate at a given node from hydraulic solution

NHnnn

Column 1 Mass flow rate in hydraulic element

Column 2 Differential head in hydraulic element

Column 3 Fluid velocity in hydraulic element

Column 4 Volume flow rate in hydraulic element

DTMAX (keyword)

DTMAX

DTMAXH

DTMAX

Initial maximum value of the time step allowable for transient calculations, regardless of the number of iterations given for the IMIN parameter (see Iteration Limit Parameters, 234). The time step used for integration will not exceed the value of DTMAX that is set. However, the value of DTMAX can be adjusted (see Maximum Allowable Time Step Adjustments, 253) during a transient run.

DTMAXH

Initial maximum value of the time step allowable for hydraulic calculations. The maximum time allowed to lapse before the hydraulic solution is updated. This is used in conjunction with the NTBHUP parameter to control when new hydraulic calculations are performed. The time and counter are both indexed at the time a new hydraulic solution is calculated with the next update determined by whichever parameter is tripped next.

DTMAXA (keyword)

DTMAXA(I,1)

DTMAXA(I,2)

DTMAXA(I,3)

DTMAXA(I,1)

I'th new value of DTMAX that you want to define.

DTMAXA(I,2)

I'th time at which the value of DTMAX is to be reset to the new value specified by DTMAXA(I,1). As many pairs of DTMAXA data as needed may be entered.

Values defined for DTMAXA groups will force QTRAN to end a time step and to begin a new time step at the DTMAXA(I,2) values.

DTMAXA(I,3)

I'th new value of DTMAXH that is to be defined.

When all DTMAXA data is entered, enter a dollar sign ($) in column 1 of the input data file. After all of the DTMAXA data is entered, enter the dollar sign ($) in column 1 and proceed to Node Definitions, 254.

DEFPND (keyword)

DEFPND(1...3)

DEFPND(1)

Starting node number of the block.

DEFPND(2)

Ending node number of the block. This value should be consistent with the value of DEFPND(1) and DEFPND(3) (again, exactly like a FORTRAN do-loop) or it may not be assigned. For example, if DEFPND(1)=1, DEFPND(2)=4, and DEFPND(3)=2, the assigned node numbers will be 1 and 3. While this is probably not what the user would have intended, this will be the result. A correct set of values, for example, might be DEFPND(1)=20, DEFPND(2)=30, and DEFPND(3)=2. This would declare node numbers 20, 22, 24, 26, 28, and 30.

DEFAULT OPTION: If DEFPND(2) is entered as zero (0), QTRAN will set DEFPND(2) to the value of DEFPND(1).

DEFPND(3)

Node number increment of the block. If DEFPND(3) is given as 0, a value of 1 will be assumed. Negative values of DEFPND(3) are allowed.

To declare single nodes, simply use the same value of DEFPND(2) that is used for DEFPND(1) (the single node number being declared) with a value of 0, 1, or blank for DEFPND(3). Alternatively, using the default options for DEFPND(2) and DEFPND(3), simply enter the node number being declared for DEFPND(1) and leave DEFPND(2) and DEFPND(3) as blank or zero.

Node number declarations are a user convenience. They allow modification of a given network by adding or subtracting nodes at will without having to completely renumber all of the nodes in the model. They also allow node numbers to be assigned to different regions of the model for clarity (e.g., nodes 100-199 to region 1, nodes 200-299 to region 2, nodes 1000-9999 to radiosity nodes, etc.), or any other scheme that may be conceived.

DEFNOD (keyword)

DEFNOD(1...3)

DEFNOD(1)

Starting node number of the block.

DEFNOD(2)

Ending node number of the block. This value should be consistent with the value of DEFNOD(1) and DEFNOD(3) (again, exactly like a FORTRAN do-loop) or it may not be assigned. For example, if DEFNOD(1)=1, DEFNOD(2)=4, and DEFNOD(3)=2, the assigned node numbers will be 1 and 3. While this is probably not what the user would have intended, this will be the result. A correct set of values, for example, might be DEFNOD(1)=20, DEFNOD(2)=30, and DEFNOD(3)=2. This would declare node numbers 20, 22, 24, 26, 28, and 30.

DEFAULT OPTION: If DEFNOD(2) is entered as zero (0), QTRAN will set DEFNOD(2) to the value of DEFNOD(1).

DEFNOD(3)

Node number increment of the block. If DEFNOD(3) is given as 0, a value of 1 will be assumed. Negative values of DEFNOD(3) are allowed.

To declare single nodes, simply use the same value of DEFNOD(2) that you use for DEFNOD(1) (the single node number being declared) with a value of 0, 1, or blank for DEFNOD(3). Alternatively, using the default options for DEFNOD(2) and DEFNOD(3), simply enter the node number being declared for DEFNOD(1) and leave DEFNOD(2) and DEFNOD(3) as blank or zero. Node number declarations are a user convenience. They allow modification of a given network by adding or subtracting nodes at will without having to completely renumber all of the nodes in the model. They also allow node numbers to be assigned to different regions of the model for clarity (e.g., nodes 100-199 to region 1, nodes 200-299 to region 2, nodes 1000-9999 to radiosity nodes, etc.), or any other scheme that may be conceived.

TCOUPL (keyword)

TCPLND

TCPLCN

TCPLND

Temperature coupled node. The node that will be replaced in the solution by the temperature coupling node.

TCPLCN

Temperature coupling node. This is the node that the coupled temperature will be equivalenced to for solution purposes. This node’s temperature will be assigned to the coupled node for output purposes.

NODXYZ (keyword)

NODEID

NODEX

NODEY

NODEZ

NODEID

User node ID that the x, y, z node locations are to be applied. The node locations are stored internally in the same order that the node temperatures are defined. Thus all internal node index references are consistent with the node locations defined in this block. It is not necessary to input all node locations, only those that are to be used in the analysis. When no more data is to be entered in the node locations block, simply put a dollar sign ($) in column 1.

NODEX

Node x location in a global Cartesian coordinate system.

NODEY

Node y location in a global Cartesian coordinate system.

NODEZ

Node z location in a global Cartesian coordinate system.

TPRINT (keyword)

TPRINT

TPRINT

Initial time interval between successive output data printings for transient calculations. The print-time interval may be modified (see Print Interval Adjustments, 259) during a transient run.

PRINTA (keyword)

PRINTA(I,1) and PRINTA(I,2)

PRINTA(I,1)

New print interval value for output during a transient simulation. Negative values force the output to be on multiples of the print interval.

PRINTA(I,2)

Time at which the new print interval will be initiated, and the time at which a print dump will be made.

As many pairs of PRINTA data may be entered as needed. Data entered for PRINTA pairs will force QTRAN to end a time step and to begin a new time step on any time values entered for PRINTA(I,2). When all PRINTA data pairs have been entered, enter a dollar sign ($) in column 1 of the input data file and proceed to Nodal Print Block Definitions, 260. If no PRINTA data is needed, enter a dollar sign ($) in column 1 and proceed to Nodal Print Block Definitions, 260.

PBLOCK (keyword)

PBLOCK(1...3)

PBLOCK(1)

Used to specify the first node number of a Print Block. For example, to print node numbers 15-23 for the nodal Print Block, PBLOCK(1) should have the value of 15.

PBLOCK(2)

Used to specify the last node number of the Print Block. For example, to print node numbers 15-23 for the Print Block, the value of PBLOCK(2) should be 23.

DEFAULT: If a 0 or blank is entered for PBLOCK(2) and PBLOCK(3), QTRAN will set PBLOCK(2) to the value entered for PBLOCK(1) and will set PBLOCK(3) to 1.

PBLOCK(3)

Used to specify the node number increment for the print block. For example, to print all node numbers from 15-23, the value of PBLOCK(3) should be 1. Negative values of PBLOCK(3) are allowed and may be used if needed.

DEFAULT: If a 0 or blank is entered for PBLOCK(3), QTRAN will set PBLOCK(3) to 1.

To specify single nodes as a Print Block, enter the same value for PBLOCK(2) as was entered for PBLOCK(1), or you may enter both PBLOCK(2) and PBLOCK(3) as zero or blank.

IPLTBK (keyword)

IPLTBK(1...3)

IPLTBK(1)

Used to specify the first node number of a Plot Block. For example, plot node numbers 15-23 for the nodal Plot Block, IPLTBK(1) should have the value of 15.

IPLTBK(2)

Used to specify the last node number of the Plot Block. For example, to plot node numbers 15-23 for the Plot Block, the value of IPLTBK(2) should be 23.

IPLTBK(3)

DEFAULT: If a 0 or blank is entered for IPLTBK(2) and IPLTBK(3), QTRAN will set IPLTBK(2) to the value entered for IPLTBK(1) and will set IPLTBK(3) to 1.

Used to specify the node number increment for the Plot block. For example, plot all node numbers from 15-23, the value of IPLTBK(3) should be 1. Negative values of IPLTBK(3) are allowed and may be used if needed.

DEFAULT: If a 0 or blank is entered for IPLTBK(3), QTRAN will set IPLTBK(3) to 1.

To specify single nodes as a Plot Block, enter the same value for IPLTBK(2) as was entered for IPLTBK(1), or enter both IPLTBK(2) and IPLTBK(3) as zero or blank.