SCRIMP, Steady-State Thermohydraulics of HTGR Subchannel

1 - Description of problem or function: SCRIMP is a thermal hydraulic sub-channel analysis code which calculates the steady state pressure drops, flow rates, heat transfer rates and temperatures in gas- cooled thermal reactors. It is not designed to model fast reactor conditions, but can be used if the power gradient across a fuel element is not too large. 2 - Method of solution: A lumped parameter type of calculation is applied using averaged values for each sub-flow-area or subsurface. The same pressure drop is assumed to exist along each sub-channel, and no net cross flow is allowed between them in any one axial step. Turbulent eddy, momentum exchange between adjacent sub-channels is, however, calculated. Four heat transfer modes are considered: 1) Surface to coolant convection. 2) Inter-surface radiation exchange. 3) Inter-surface conduction. 4) Surface to ambient heat loss. Axial variation of physical properties and the redistribution of mass flow between sub-channels can be accounted for by dividing the problem into a series of axial steps. The outflow properties of one step are used to compute the inflow properties of the next. 3 - Restrictions on the complexity of the problem: There is a maximum of 28 characteristic flow channels and 74 characteristic surfaces. However, the total number of channels and surfaces is limited only by the available memory space