Optimization of working surfaces heat transfer based on local control of thermophysical parameters
DOI:
https://doi.org/10.31548/energiya2020.05.069Abstract
The progressive trend of increasing the efficiency and operational reliability of equipment requires continuous improvement of methods for monitoring and managing work processes. One of the most promising methods for studying transport processes occurring in difficult conditions is physical modeling.
The object of this research is heat-exchange prismatic surfaces, which are typical for many technical applications.
The purpose of the work is to develop methods for optimizing heat transfer of working surfaces based on local control of thermophysical parameters in characteristic zones of the working environment.
The studies were carried out in the ADS-1 aerodynamic stand using the methods of heat and mass analogy and hot-wire anemometry. The arrangement included four rows of prismatic elements.
The essence of the local approach is to determine the average surface heat transfer coefficient from the local velocity, measured above each prismatic element, which makes it possible to estimate the spatial temperature heterogeneity of a specific arrangement and take measures to change the temperature in the desired direction by maneuvering the location of the elements. The proposed approach is fundamentally different from another widespread approach, which we called the channel one, in which information about the velocity and temperature fields is ignored, and the influence of the configuration and size of elements and their location on the hydrodynamic structure of the flow is insufficiently taken into account. The local approach allows, firstly, to more accurately diagnose the types of flow in the boundary layer of a streamlined element, determining laminar, turbulent, pseudolaminar, quasiturbulent, transition and separated flow regimes. Second, on the basis of a set of statistical data, make the transition to an arbitrarily specified arrangement of elements and thereby increase the accuracy of determining the temperature state of individual prismatic elements and the entire arrangement as a whole.
Equations of similarity are proposed for calculating the local heat transfer of each face of the prism separately and the average surface heat transfer depending on the geometric and operating parameters. On the basis of the recommendations received, the thermal state of the elements of a specific arrangement was evaluated and measures were developed to improve it through targeted rearrangements of the elements.
Key words: prismatic heat exchange surface, local thermophysical parameters, optimal arrangement
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