transient

In this study, a new method of choosing classical empirical equations for calculating heat transfer coefficients in the tubes of a shell-and-tube heat exchanger in the transient mode is proposed. This method is based on the fact that the flow is structured into a laminar boundary layer (LBL) zone and a turbulized part, and the heat transfer coefficient is calculated through the transient and turbulent heat conductivity, as well as the average thickness of the LBL and, accordingly, the average thickness of the rest of the coolant flow.

The unexploring problem of digital control systems analyzes in this article — the impact on their behavior of the limited bit resolution of the hardware and, accordingly, the discrete transfer functions coefficients. The research conducted by the zeros/poles and transient characteristics methods using the mathematical application MATLAB with the package Control System Toolbox and confirmed the relevance of this problem.

The paper on the basis of interdisciplinary approaches presented mathematical model of the electric power system, a key element of which is the power line that connected substation “Zakhidnoukrayins’ka” — substation “Vinnyts’ka”. On this basis, the analysis of transients in the power line to single-line performance. Results transients are presented as figures which analyzed.

The article deals with mathematical modeling of non-stationary processes non-periodic pressure of the fluid in cylindrical tubes. Based on the Navier-Stokes equations for compressible fluid withdrawn simplified equation for the case of long pipes. It is shown that modeling of single processes, these equations contain only one dimensionless parameter. Identifies conditions which may further simplify these equations to a form that does not contain a dimensionless parameter.