Introduction

Background

Objectives


Test facility

Diagnostic techniques


Cross-flow influence

Overall boiling curves

Intermittent cooling efficiency

Heat transfer correlations






 

 
Advances in Intermittent Spray Impact Research

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  Overall boiling curves

The concept of overall boiling curve is first introduced in Moreira and Panão (2006) as a way of describing the boiling curve for a spray with heterogeneous heat transfer processes within the impact area.


According to the classical boiling theory, the boiling curve has two characteristic points: the critical heat flux (CHF) occurring at the Nukyiama temperature; and the minimum heat flux (MHF) occurring at the Leidenfrost temperature (see figure).


An intermittent spray has different local boiling curves throughout the impact area as shown in Panão and Moreira (2005). This means different CHF and MHF, and their corresponding temperatures as depicted below.




This necessarily leads to an integration of the local time-average heat fluxes over the impact area in order to define a boiling curve for a spray, resulting in overall boiling curves as exemplified below for several frequencies of injection.



References
  • Panão, M.R.O. and Moreira, A.L.N. (2005) “Thermo- and fluid dynamic characteristics of spray cooling with pulsed sprays”, Experimental Thermal and Fluid Science, v.30, pp.79-96.
  • Moreira, A.L.N. and Panão, M.R.O. (2006) “Heat transfer at multiple-intermittent impacts of a hollow cone spray”, International Journal of Heat and Mass Transfer, v.49, pp.4132-4151.