Fluid Flow and Heat Transfer in Air Jet Impingement in Food Processing

Abstract

Air impingement technology is gaining popularity in food-processing operations such as baking, freezing, drying, and toasting. In this article, physical characteristics of impinging jets, such as turbulent mixing in the free jet region, stagnation, boundary-layer formation, recirculation, and their interactions with food products in terms of heat and mass transfer have been reviewed. The discussion includes experimental methods used for measurement of heat and mass transfer for single and multiple slot and circular jets. Procedures used for measurement of heat-transfer coefficient such as lumped sensor method, micro-calorimetric approach, and use of flux sensors are presented. Typical qualitative and quantitative flow-field studies using planar visualization and laser Doppler anemometry have been reviewed. Numerical modeling of air impingement systems is discussed with special consideration of problems arising in food-processing systems.

Characterization of a combination oven prototype: Effects of microwave exposure and enhanced convection to local temperature rise in a moist substrate

“…As reviewed by Sarkar et al [25], quantitative determination of the flow field of impinging jet ovens was carried out by using a variety of experimental techniques. In the present work a hot wire anemometer was employed (Digitron, AF210, Torquay, UK) with the sole JI system in operation, and no MW production.…”

“…Food industry has used JI for faster processing rates and reduced cooking times in processes such as baking, freezing, toasting and drying. In some cases JI operations help improve product quality [25]. In actual installations, JI can be obtained when air is injected by one or more nozzles of a given geometry [22].…”

Mathematical modeling of air-impingement cooling of finite slab shaped objects and effect of spatial variation of heat transfer coefficient

“…Impingement on a hot surface is widely used in various industrial applications because of a high heat transfer rate (Fujimoto, Hatta, & Viskanta, 1999). Sarkar, Nitin, Karwe, and Singh (2004) gave a comprehensive review of fluid flow and heat transfer in air jet impingement in food processing. They have stated that the air impingement systems have been used in various industrial applications such as textile and paper drying, electronic cooling and glass quenching, and their use have also been gaining popularity in the food industry, especially in applications such as freezing, thawing and baking.…”

Axisymmetric wall jet development in confined jet impingement

“…12. The velocity magnitude is normalized by u m at each x/d location and the vertical distance from the bottom wall is non-dimensionalized by the nominal y 1/2,i , obtained using the fitted coefficients β i for both the top layer and the wall layer in Equation (2). The rescaled velocity profiles, shown in Fig.…”