Multiphase computational fluid dynamics–conjugate heat transfer for spray cooling in the non-boiling regime

Abstract

A numerical study is described to predict, in the non-boiling regime, the heat transfer from a circular flat surface cooled by a full-cone spray of water at atmospheric pressure. Simulations based on coupled computational fluid dynamics and conjugate heat transfer are used to predict the detailed features of the fluid flow and heat transfer for three different spray conditions involving three mass fluxes between 3.5 and 9.43 kg/m 2 s corresponding to spray Reynolds numbers between 82 and 220, based on a 20 mm diameter target surface. A two-phase Lagrange-Eulerian modelling approach is adopted to resolve the spray-film flow dynamics. Simultaneous evaporation and condensation within the fluid film is modelled by solving the mass conservation equation at the film-continuum interface. Predicted heat transfer coefficients on the cooled surface are compared with published experimental data showing good agreement. The spray mass flux is confirmed to be the dominant factor for heat transfer in spray cooling, where single-phase convection within the thin fluid film on the flat surface is identified as the primary heat transfer mechanism. This enhancement of heat transfer, via single-phase convection, is identified to be the result of the discrete random nature of the droplets disrupting the surface of thin film.

Design and analysis of a cooling system for a supersonic exhaust diffuser

“…This method is utilized in Langari et al. 9 and Guechi et al. 12 for the numerical simulation of the spray cooling systems.…”

“…The heat transfer coefficient in the water spray method is much higher than that in the water jacket method. According to the references, 9,13,14 thermal protection of furnaces and iron melting process are examples of the existing systems that use water spray techniques. In general, the water spray method is used where a high heat flux needs to be removed and has proven to have a higher efficiency.…”

“…A schematic of this process is shown in Figure 1. The important factors affecting the water spray performance have been studied by Langari et al 9 Sarkar, 15 and Zhao et al 16 These factors include the nozzle type, orifice diameter, spray angle, flow rate (which depends on the pressure), fluid properties, droplet temperature, spray impact momentum, nozzle angle relative to the surface, and Weber number.…”

“…Therefore, the discrete phase method is appropriate for solving this problem. This method is utilized in Langari et al 9 and Guechi et al 12 for the numerical simulation of the spray cooling systems.…”

“…The most important methods of cooling a diffuser surface include water jacket, jet impingement, and spray cooling. [5][6][7][8][9][10] The present study focuses only on the spray cooling system. Spray cooling is a complex phenomenon, and several parameters affect its performance.…”