Forced Convection — Study of the Regular Thermal Regime in Different Layers at the Liquid Height

Abstract

The rate of cooling (heating) of experimental liquids was studied separately for five thermocouples located at different heights of the experimental probe.

Research has been carried out on an experimental stand in the system “environment I — body II”, where “environment I” is water, and “body II” is the investigated liquid medium in a thin metal cylindrical shell under conditions of free convection.

The regular mode of cooling (heating) of the object is characterized by a change in the temperature field over time, which is described by an exponential dependence, while the relative cooling rate t of all points of the body remains a constant value, independent of coordinates and time.

The theory of a regular thermal regime has been widely used to solve many practical problems: to determine the rate of cooling (heating) of a body, to study the thermophysical properties of materials, heat transfer and radiation coefficients, thermal resistance, etc. The advantages of this method are that the design of the device and the technique of conducting the experiment are simple, the accuracy of the obtained results is quite high, and the time of the experiment is short.

Non-stationary thermal conductivity corresponds to a thermal regime unstable in time, created by this or that thermal action on the body or environment. Non-stationary thermal conductivity is characterized by the fact that the temperature changes not only from point to point, but also over time. Non-stationary thermal conductivity occurs during heating or cooling of bodies, as well as when starting or stopping heat exchange devices, power units, etc.

The experimental results are presented on the study of the rate of cooling (heating) of experimental liquids separately for five thermocouples located at different heights of the experimental probe under conditions of forced convection