A study of nucleate boiling and critical heat flux with EHD enhancement

Abstract

Abstract. The paper describes results from an experimental and theoretical study of the effect of an electric field on nucleate boiling and the critical heat flux (CHF) in pool boiling of R123 at atmospheric pressure on a horizontal wall with a smooth surface.Two designs of electrode (parallel rods and wire mesh) were used.The experimental data exhibit some differences from the data obtained by other researchers in similar experiments on a wall with a different surface finish and with a slightly different design of wire mesh electrode. The hydrodynamic model for EHD enhancement of CHF cannot reconcile the differences.A theoretical model has been developed for the growth of a single vapour bubble on a superheated wall in an electric field, leading to a numerical simulation based on the level-set method. The model includes matching of sub-models for the micro-and macroregions, conduction in the wall, distortion of the electric field by the bubble, the temperature dependence of electrical properties and free-charge generation. In the present form of the model, some of these effects are realised in an approximate form. The capability to investigate dry-spot formation and wall temperature changes that might lead to CHF has been demonstrated.

Development of Boiling Type Cooling System Using Electrohydrodynamics Effect

“…They indicated that a slight deposit on the boiling surface can substantially shift the boiling curve and increase CHF. Also, Hristov et al [5] reconfirmed that no hysteresis was shown with Fig. 7.…”

“…Also, the EHD has been recognized as an efficient active method to increase the heat exchange. The CHF for saturated boiling of R123 on polished copper wall at atmospheric pressure was increased up to 64.6 W/ cm by the application of a high dc voltage of 25 kV [5].…”

An experimental investigation of pool boiling heat transfer on smooth/rib surfaces under an electric field

“…Heat flux decreased with the increasing electric field intensity at the same degree of superheat. Although this deterioration in heat flux was also recorded by Hristov et al [18], but they did not analyze this phenomenon because this region existed in a small portion in the boiling curve. Typical nucleation region corresponding to the middle superheat temperature of 20°C < DT < 30°C showed no interaction between bubbles.…”

Equilibrium shapes of a heterogeneous bubble in an electric field: a variational formulation and numerical verifications

“…, 5) as: If the velocity y 1 is supported on Γ 12 (which implies the interfaces between the fluids and the solid substrate remain unchanged if δ is small enough), without loss of generality we can assume the velocity y 1 is normal to the interface Γ 12 and given by y 1 = vn. Then it is clear that T3 = T4 = 0, 10) and (e.g. [47])…”