**RSICC CODE PACKAGE PSR-393**

**1. NAME AND TITLE**

COMMIX-1C: 3-D Single-Phase Thermal Hydraulics.

**2. CONTRIBUTORS**

Argonne National Laboratory, Argonne, Illinois and US DOE Pittsburgh
Energy Technology Center, Pittsburgh, Pennsylvania through the Energy Science
and Technology Software Center, Oak Ridge, Tennessee.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN 77; Cray, RS/6000, Sun (P00393MNYCP00) (1996 release).

Previous versions available: COMMIX-1B for Vax and IBM Mainframes.

(P00393DVX1100 and P00393I303300) (1991 release).

**4. NATURE OF PROBLEM SOLVED**

COMMIX-1C is designed to perform steady-state or transient, single-phase,
three-dimensional analysis of fluid flow with heat transfer in a single-component
or multicomponent system. The program was developed for the analysis of
heat transfer and fluid flow processes in a nuclear reactor system; however,
it can easily be applied to non-nuclear systems requiring heat transfer
and/or fluid flow analysis. COMMIX-1C solves the conservation equations
of mass, momentum, and energy, and transport equations of turbulence parameters
and provides detailed local velocity, temperature, and pressure fields
for the problem under consideration. It is capable of solving thermal-hydraulic
problems involving either a single component, such as a rod bundle, reactor
plenum, piping system, heat exchanger, etc., or a multicomponent system
that is a combination of these components.

**5. METHOD OF SOLUTION**

COMMIX-1C uses the finite-difference approach to solve the conservation
equations of mass, momentum, and energy and transport equations of turbulence
parameters. These equations are solved as a boundary-value problem in space
and an initial-value problem in time. The solution of the equations is
achieved by the successive over relaxation procedure. The staggered grid
system is used, which considers the field variables as located at the center
of a cell and flow variables as located at the surface of a cell. In COMMIX-1C,
the finite-difference discretization equations are formulated by integrating
the conservation equations over a control volume. There are two alternative
formulation schemes in COMMIX-1C. One is semi-implicit and is a modification
of the ICE technique. It is ideally suited for analyzing fast transients.
The other, a fully implicit scheme called SIMPLEST-ANL, is a modification
of the numerical procedure known as SIMPLER. It is particularly suitable
for the analysis of slow and normal transients.

**6. RESTRICTIONS OR LIMITATIONS**

Maxima of 99 calculational cells in each of the x, y, and z directions,
99 surfaces, 50 user-defined rebalancing regions, 20 correlation types
available for force structures, 10 heat transfer correlations, and 10 materials.

**7. TYPICAL RUNNING TIME**

Running time is dependent on the size and complexity of the problem
being simulated and can vary from a few seconds to several hours of CPU
time.

**8. COMPUTER HARDWARE REQUIREMENTS**

COMMIX-1C runs on Cray, IBM RS/6000 and Sun computers. Problem size determines the memory requirements, which range from 550K to several megabytes.

COMMIX-1B ran on DEC Vax 11 under VMS 5.2 or on IBM 3033 under VM/CMS.

**9. COMPUTER SOFTWARE REQUIREMENTS**

Version 1C runs on Unix-based operating systems and requires Fortran
77 and C compilers. Version 1B requires a Fortran 77 compiler and an assembler
for the IBM version.

**10. REFERENCES**

**a) Included in documentation:**

H. M. Domanus, Y. S. Cha, T. H. Chien, R. C. Schmitt, W. T. Sha, "COMMIX-1C: A Three-Dimensional Transient Single-Phase Computer Program for Thermal-Hydraulic Analysis of Single-Component and Multicomponent Engineering Systems, Equations and Numbers," NUREG/CR-5649, ANL-90/33, Vol. 1 (November 1990).

H. M. Domanus, Y. S. Cha, T. H. Chien, R. C. Schmitt, W. T. Sha, "COMMIX-1C:
A Three-Dimensional Transient Single-Phase Computer Program for Thermal-Hydraulic
Analysis of Single-Component and Multicomponent Engineering Systems, User's
Guide and Manual," NUREG/CR-5649, ANL-90/33, Vol. 2 (November 1990).

**b) Background information:**

"COMMIX-1B: A Three-Dimensional Transient Single-Phase Computer Program for Thermal Hydraulic Analysis of Single and Multicomponent Systems Volume I: Equations and Numerics," NUREG/CR-4348, ANL-85-42 Vol. I (September 1985) and Erratum (January 31, 1986).

"COMMIX-1B: A Three-Dimensional Transient Single-Phase Computer Program for Thermal Hydraulic Analysis of Single and Multicomponent Systems Volume II: User's Manual," NUREG/CR-4348, ANL-85-42, Vol., II (September 1985).

"COMIX-1B, NESC No. R1066.VAX, COMMIX-1B DEC VAX Version tape Description and Implementation Information, NESC Note 91-98 (September 6, 1991).

"COMMIX-1B, NESC No. R1066.3033C, COMMIX-1B Edition C Tape Description
and Implementation Information," NESC Note 91-97 (September 6, 1991).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents in (10.a) and one diskette which
include the source code, makefiles, and input/output files written in a
self-extracting compressed DOS file. No executables are provided with the
package.

**12. DATE OF ABSTRACT**

April 1999.

**KEYWORDS:** HEAT TRANSFER; THERMAL HYDRAULICS