This paper deals with the one-dimensional unsteady fluid flow model of a natural circulation loop. The governing equations are solved according to both the Euler and Lagrange approaches on two parallel computational grids. The linearization of equations and a semi-implicit discretization scheme are used to enhance the algorithm’s effectiveness. The results of the simulations were verified by using experimental data obtained on an experimental rig that was a scale model of an emergency system for the removal of residual heat after reactor shutdown. The parameters compared were the helium temperature at two locations and the heater outlet pressure. The simulation results generally did not differ from the experimental data by more than 10%. The best agreement was obtained for scenarios in which the helium pressure was highest in combination with slow changes in the input parameters (less than 4%). Conversely, the results differed the most for the scenario with extremely fast device cooling (20%).

The article describes the application of a mathematical model to a natural circulation loop. A set of measurements were conducted at the experimental facility. The pressure and velocity relations were observed during the steady flow of helium. The main goal was to create a numerical model of flow capable of determining the velocity of flowing medium. The model describes the flow of highly compressed gaseous medium with variable density in direct pipelines with local resistances. At the current state, the temperature values along the loop are taken as input to the model. The article also includes the evaluation of local resistances in DHR and GFR, which significantly affects the resulting accuracy. The results from a numerical model are compared with experiments.

Naturally circulated helium loop is a device designed for a decay heat removal from fast nuclear reactors of the type ALLEGRO. The flow is provided by a potential energy difference between hot and cold piping branch. Here we introduce a 1D model of flow in the loop. The model describes the flow of a highly compressed gas with changing density in straight pipes and in the obstacles. The results of the model are compared with experiment.

A numerical model is proposed for flow of helium in natural circulation loop during steady state. The calculations were verified with measurements on experimental facility built in Trnava. The model relies on the calculations of pressure losses along the loop. The estimation of local losses coefficient was essential.

Optimization problems relating to heat source operation are solved via linear (LP) or nonlinear (NLP) programming. The optimization methods used can be compared based on the complexity of the computational program setup, the time required to input and update data, and the computational time required for the optimal shifting and loading of installed power machinery. LP methods are preferred (e.g., the simplex method, the method of characteristics), but the Lagrange multiplier NPL method is sometimes applied. In this paper, the method of proportional increments (LP and NLP) is applied to compare the optimal loadings of power machinery installed in a thermal power plant using linear and quadratic economic characteristics.