Heat Exchange Between Air and a Liquid Film Flowing Down Along a Profiled Surface

The laws of heat exchange between air and a liquid film flowing down along a solid surface with spherical dimples were investigated experimentally. Three cases of heat transfer were considered: quiescent air, air – liquid counter flow, or their cross flow. In all cases, a significant growth of the heat exchange intensity, especially at air – liquid cross flow, was observed. This is caused by the substantial turbulization of flow and mixing of liquid layers in the film. As a result, it was established that surface profiling (manufacture of dimples) under the optimal conditions leads to an increase in heat exchange intensity by an unexpended factor of 2.5 – 2.8 as compared with a smooth surface, other conditions being equal. The obtained experimental data were generalized in the form of dimensionless dependences Nu vs. Re. The best heat transfer surface can be recommended for use in different heat exchangers.

Experimental investigation of the heat exchange intensity

We study heat exchangers at the experimental setup aiming at the energy-saving. The feature of this heat exchange process is of the fact that the working medium is a porous metal. The pores are filled with freon and operation of the refrigeration unit condenser is studied. The scheme of the experimental setup and experiment methodology are given. The results of the experiment and its processing are also presented.

Regimes of stabilization of the flow of anomalous thermoviscous liquid depending on the heat exchange

In the paper the results of numerical modeling of the flow of an incompressible fluid with a non-monotonic dependence of the viscosity on the temperature in a channel are presented. On the channel’s walls the heat exchange is specified that are written mathematically in the form of the boundary conditions of the third kind on the basis of the Newton– Richman convective heat exchange law. The regimes of flow stabilization in the channel depending on the Nusselt numbers have been studied. Four different types of unsteady processes are discovered and it has been shown that they are determined by the different heat exchange intensity.

Heat Transfer in Boiling Magnetic Fluid in a Magnetic Field

In the present work we report the investigation of heat exchange processes at stationary boiling regime of magnetic fluid on a horizontal surface under magnetic field H ≤ 4.2 kA/m. In the presence of uniform magnetic field the specific thermal flow arriving to boiling magnetic fluid increases by 1.5 - 2 times. We offer the mechanism of magnetic field influence on heat exchange intensity in boiling magnetic fluid. The volume, shape and contact area of steam bubbles in horizontal heating surface in magnetic field is studied. The equation, connecting a specific thermal flow, magnetic field gradient and magnetic fluid magnetization in bubble boiling regime of magnetic fluid is written.