Development of the New Comprehensive Performance Evaluation Equipment for Enhanced Convective Heat Transfer Techniques
Based on the new performance evaluation criterion system (PECS) for enhanced convective heat transfer techniques, an evaluation equipment of enhanced heat exchange tube was developed. The equipment structure and functions, parameters measurement and control of auxiliary system were introduced in detail. The monitoring and control software was programmed with the Delphi 7.0, and be used to realize the data acquisition and processing, database operation and management, and many other functions. A kind of new type enhanced heat exchange tube was tested. The experience result shows that apparatus is feasible to evaluate the performance of enhanced convection techniques.
Least dissipation principle of heat transport potential capacity and its application in heat conduction optimization
In the viewpoint of heat transfer, heat transport potential capacity and its dissipation are defined based on the essence of heat transport phenomenon. Respectively, their physical meanings are the overall heat transfer capability and the dissipation rate of the heat transfer capacity. Then the least dissipation principle of heat transport potential capacity is presented to enhance the heat conduction efficiency in the heat conduction optimization. The principle is, for a conduction process with the constant integral of the thermal conductivity over the region, the optimal distribution of thermal conductivity, which corresponds to the highest heat conduction efficiency, is characterized by the least dissipation of heat transport potential capacity. Finally the principle is applied to some cases in heat conduction optimization.
A Comparison of the Influence of Mechanical and Acoustical Vibrations on Free Convections From a Horizontal Cylinder
Abstract : The results are presented of an experimental investigation of the influence of horizontal transverse mechanical vibrations (frequency order of magnitude: 100 cps) upon the rate of convective heat transfer from a horizontal cylinder. The results are compared with earlier findings. It is shown that, in spite of a tenfold difference in frequency (and amplitude), the heat-transfer correlation equation previously developed for horizontal acoustical vibrations is also valid for horizontal mechanical vibrations, and that the character of the boundary-layer flow is the same (thermoacoustic streaming) for these two cases.