Boiling process in oil coolers on porous elements

Abstract

Holography and high-speed filming were used to reveal movements and deformations of the capillary and porous material, allowing to calculate thermo-hydraulic characteristics of boiling liquid in the porous structures. These porous structures work at the joint action of capillary and mass forces, which are generalised in the form of dependences used in the calculation for oil coolers in thermal power plants (TPP). Furthermore, the mechanism of the boiling process in porous structures in the field of mass forces is explained. The development process of water steam formation in the mesh porous structures working at joint action of gravitational and capillary forces is investigated. Certain regularities pertained to the internal characteristics of boiling in cells of porous structure are revealed, by means of a holographic interferometry and high-speed filming. Formulas for calculation of specific thermal streams through thermo-hydraulic characteristics of water steam formation in mesh structures are obtained, in relation to heat engineering of thermal power plants. This is the first calculation of heat flow through the thermal-hydraulic characteristics of the boiling process in a reticulated porous structure obtained by a photo film and holographic observations.

Analogy in the processes of heat exchange of capillary-porous coatings in energy installations

“…Influence of heat flux density on wall overheating with respect to water vapor temperature (P = 0.1 MPa): 1 -boiling in a large volume on uncoated surface [5][6][7][8]15]; 2 -area of heat pipes operation [9][10][11]; 3 -area of operation of thin-film evaporators [5]; 4 -studied porous cooling system. Shaded area means application of intensifiers in a porous system [1][2][3][4]16].…”

“…The visualization of the thermal impact was also realized with the help of holography, which allowed to investigate the limiting state of good and poor heatconducting materials in the form of porous structures and a steam generating surface. The heat exchange control in porous structures was performed by affecting the internal boiling characteristics and integrated magnitudes [1][2][3][4].…”

“…A number of experimental units have been developed which provide a means of studying the integral characteristics of heat transfer: heat flux rate q, liquid and steam flow rates ml, ms, temperature field distribution along the height and length of the heat exchange surface [3,4].…”

“…Studies are performed in a capillary-porous cooling system, which can operate on the principle of a closed or non-closed evaporative condensation scheme. Various heat exchange conditions, such as: the method of cooler supplying, the degree of clamping by the capillaryporous structure, the ability to feed the structure from the micro-arteries on the height of the heat exchange surface, the orientation of the wall relative to the gravitational forces, the flat, tubular and curved cooling surfaces, the system operation under pressure until the crisis phenomena with a burn walls are studied in [3,4].…”

“…Holography methods [16], dimensional analysis [2] and analogous phenomena [3][4] generalization have been used to study the mechanism of heat transfer.…”