Abstract
The of effect pulse form (rectangular, sinusoidal and triangular) on the fluid flow and heat transfer of an intermittent jet impingement was studied numerically. It was shown in a non-steady-state jet, both an increase and decrease in heat transfer are possible compared with steady-state jet for all investigated pulse forms. For small distances between the pipe edge and obstacle (H/D ≤ 6) in the pulsed jet, heat transfer around the stagnation point increases with increasing pulse frequency, while for H/D > 8 an increase in frequency causes a heat transfer decrease. A growth in the Reynolds number causes a decrease in heat transfer, and data for all frequencies approach the steady-state flow regime. The numerical model is compared with the experimental results. Satisfactory agreement on the influence of the form and frequency of pulses on heat transfer for the pulsed jet on the obstacle surface is obtained.
Highlights
Many works deal with the study of aerodynamics and heat transfer in turbulent impinging jets.High values of heat and mass transfer are observed around the stagnation point at the interaction of a jet with an obstacle surface
In the intermittent impinging jet, both an increase and suppression of heat transfer are possible in comparison with a steady-state jet for all studied pulse forms
The heat transfer at the stagnation point increases with increasing pulse frequency in the region of relatively small distances between the pipe edge and the obstacle
Summary
Many works deal with the study of aerodynamics and heat transfer in turbulent impinging jets. High values of heat and mass transfer are observed around the stagnation point at the interaction of a jet with an obstacle surface. Such studies are used in many practical applications (cooling various power equipment, turbine blades, coating, drying, and hardening various materials, etc.). Detailed theoretical and numerical studies of the heat and mass transfer in steady-state jets impingements have been performed. A pulsed (non-steady-state) impinging jets are one of the methods for active control of the fluid flow and heat transfer characteristics.
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