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MARDARSKII, Orest; BOLOGA, Mircea; CHERNIKA, Ion; KOZHEVNIKOV, Igor. Influence of electrohydrodynamic liquid flow on heat transfer at boiling. In: Materials Science and Condensed Matter Physics. Ediția a 9-a, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, p. 256.
|Materials Science and Condensed Matter Physics
Ediția a 9-a, 2018
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 25-28 septembrie 2018
Tendencies to miniaturization of electrotechnical and electronic equipment is typical for the modern development of them; thus, there increase the specific heat loads, get worse the cooling and thermal conditions of separate units and blocks, and degrade the equipment reliability. It is necessary to develop more effective methods of heat transfer enhancement, to design compact efficient heat exchangers, reliable systems of cooling and thermostatting. By now there is accumulated a wide experimental information concerning the influence of an electrical field on heat transfer enhancement which is usually associated with the electroconvective disturbances of liquid. The field action efficiency is also determined by the heat- and electrophysical properties of a heat carrier, the form and sizes of electrodes, the field intensity and the field nonuniformity degree. However, the electroconvective methods of cooling with the growth in heat loads not always ensure the necessary temperature conditions, thus, it is required to elaborate evaporative cooling systems (active control closed-loop electrohydrodynamic systems). It is interesting to study hydrodynamics and heat transfer at phase transformation using special electrodes. The report presents the results of experimental investigation of nonuniform electrical field action on heat transfer and boiling process of a dielectric liquid (hexane, with a boiling temperature of 68,7 ºС) in bulk. The heating of the heat-release element (stainless tube) was performed with direct current. The high-voltage electrode (insulated wire with notches facing the heating surface) was placed over the heating surface. There were obtained the experimental dependences of heat transfer intensity on the heat flux density, interelectrode gap and field intensity. The field influence on the bubbling process reduces with the increase in the heat flux density indicated by the local values of the heat transfer coefficient. The results are in good agreement with literature data and calculated functions (fig. 1). There is investigated the influence of the interelectrode gap on the heat transfer intensity whose optimum value is δ=2,5–3 mm. There is compared the experimental results concerning the heat transfer intensity at boiling as a function of the counter electrode form and profile. At little intensities it is preferable to use a solid electrode 1, and at an intensity of about 40 kV/cm and higher it is necessary to use an electrode with notches 2 (fig. 2).