This report describes TVENT, a j-table FORTRAN computer program for predicting flows and pressures in a ventilation system subject to a tornado. The pressure and flow values calculated by TVENT can be used as a basis for structural analysis. TVENT is a one-dimensional, lumpedparameter model with incompressible flow augmented by fluid storage. The theoretical basis for the mathematical modeling and analysis is presented, and a description of the input for the computer code is provided. Modeling techniques specific to ventilation systems are described. Sample problems illustrate the use of TVENT in analyzing ventilation systems. Other sample problems illustrate modeling techniques used in reducing complex systems.

can be expressed as the sum of the lattice conductivity ( A t ) and the electronic coxductivity (A,). X1. = A1 3-Xe(1) Since the lattice conductivity in mixed conductors is difficult to measure directly, the separation of the two processes can be estimated using the Wiedemann-Franz relation A LTA T = -+ T P where A is a constant, T the absolute temperature, L the Lorenz number, and p the electrical resistivity.The data for Uo.495C~ ~BnOo.02 and Uo.4,~Co.,00.1, were analyzed using a special curve-fitting computer programz1 to evaluate the approximate magnitude of X I and A,.(Details of this analysis are reported elsewhere.') The results, although subject to some quantitative limitations, suggest that mixed thermal conduction occurs in uranium oxycarbide.At low temperatures, significant lattice conduction is observed which decreases significantly as the oxygen content is increased (Table 111) ; at high temperatures electronic conduction is dominant. Calculations of the electronic conductivity at 1500°C show that it comprises approximately 85% of the total thermal conductivity at the 2 at.% oxygen level and approximately 95% at the 16 at.% level. At room temperature the lattice conductivities represent 75 and 30% of the total conductivity for the carbides containing 2 and 16 at.% oxygen, respectively. Ryferences A test is described which permits ranking of brittle materials according to their resistance to thermal fracture under steadystate conditions. A water-cooled probe and a small, thin, annular disk specimen heated by a radiator are used. Tests on AUC graphite and on a series of composites of transitionmetal pseudobinary solid-solution carbides with graphite were very reproducible and reliable. A thermal-stress analysis for the graphite agreed well with the test results.

We wi 11 present the results of a numerical and an experimenta 1 study of a flow network subjected to a simulated explosion. The numerical simulation uses a computer codP. ca 11 ed EVENT that predicts the response of a system under gas-dynamic stress conditions. The experiment uses a real flow system that is injected with a high-1fressure gas. The results from these two 'are compared using a flow parameter such as pressure. We conclude that the numerical calculation matches the results of the experiment quite well. I.

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