Experimental investigation of spray heat exchanger performance

الملخص EN

A study of the impact dynamics of liquid droplets on a solid surface is required for modeling industrial processes such as spray cooling of hot surfaces, fire extinguishing systems by sprinklers, plasma coating, evaporative cooling, or surface cooling (quenching), ...etc.

An experimental test loop was installed to investigate experimentally the droplet phase change and the heat transfer between heated tube surface and impinging water liquid droplet.

Moreover, investigation the effect of the hot surface superheating, distance from the nozzle distributor to the hot surface location, initial droplet velocity and initial droplet size on heat transfer coefficient and evaporation rate were conducted.

By using the Phase / Doppler Particle Analyzer, the droplet velocity and the droplet size were measured.

The results show that the sprayed mass flow rate and the droplet impinging velocity increased as spray pressure increased, but the droplet size tends to decrease with increasing the spray pressure.

It was found that, droplet mean velocity has a maximum value at the spray centerline, and decreases towards the periphery of the stream.

The sauter mean diameter of the droplet has a minimum value at the center and increases monotonically towards the spray periphery.

The evaporation rate and the heat transfer effectiveness increase by decreasing the falling distance.

Also, the evaporation rate and the heat transfer effectiveness increase by decreasing the initial droplet velocity.

For high initial sprayed mass velocity, the evaporated mass flow rate and the heat transfer effectiveness are inversely proportional to the droplet size.

The comparison between the experimental results and the analytical solution shows reasonable agreement ranging from 8 to 12 %.