Effect of Ice Contamination on Liquid-Nitrogen Drops in Film Boiling

The Leidenfrost Phenomenon: Experimental Investigation of the Vaporization of Nitrogen Droplets on a Food Surface

“…This contamination caused reflection of the rays of light from the floodlight as a result of the whittish ice patches on the droplet's surface. However, as reported earlier by Keshock and Bell (1970) and Schoessow et al (1978), shorter vaporization time ( Fig. 7) and slightly higher values of the apparent heat transfer coefficient (Fig.…”

“…However, the sprays issuing from a pressure nozzle are usually polydispersed (Awonorin, 1989b gen in an environment well above the boiling point of the liquid (-196°C) will cause rapid evaporation of a fraction of the liquid even before impinging on the food substrate (Awonorin, 1989c). Also, moisture from the air in the freezing tunnel and from the foodstuffs usually contaminates the sprays (Awonorin and Lamb, 1988), so a decrease in the vaporization time of droplets occurs in practice (Schoessow et al, 1978). The quantity of moisture available in a cryogenic freezer is highly variable as a result of high dew point temperature of the air and free moisture from the incoming foodstuffs.…”

Heat transfer coefficient for nitrogen droplets film‐boiling on a food surface

“…Schoessow et al (1978) reported an overall decrease in evaporation times by as much as 20.0% for liquid nitrogen drops deliberately contaminated with ice. In the present work, such ice contamination was observed in only a few evaporation runs.…”

“…Evaporation of individual liquid nitrogen droplets on a metal plate was studied by Keshock & Bell (1970), Baumeister, Keshock & Pucci (1971), Schoessow, Chmielewski & Baumeister (1978). Hassan (1981) and Awonorin (1982) measured evaporation times and droplet size in contact with food.…”