Design of radio frequency systems combined with air impingement for thawing of frozen food products

Conventional methods based on convection and conduction heat transfer are widely used for thawing/tempering food products. With this system, since heat transfer travel from surface to center of sample, it is high possible to face quality lost during the obtain the tempering or thawing temperature at center of sample. In radio frequency system which is an innovative food processing method, the sample interacts with electromagnetic energy and volumetric heating occurs in the sample. There is a significant reduction in process time compared the conventional method due to the volumetric heating in radio frequency systems. However, the refraction of electromagnetic energy at corners and edges of sample results in non-uniform temperature distribution, especially thawing process. For this reason, mathematical model studies were carried out to design radio frequency combined with air impingement system to eliminate the high temperature problem at surface of sample. In order to developed this kind of radio frequency system, the effects of the parameters in the radio frequency process were investigated by both experimental and mathematical model studies. Electrode design, orientation of potential electrode and electrode distance effects on the temperature distribution were compared in three different radio frequency systems. According to results, batch single cavity and continuous tunnel cavity were developed combined with air impingement system. In developed combined radio frequency systems, various applied voltage and air velocity were investigated to obtained uniform temperature distribution. In terms of the temperature uniformity, suitable result was obtained applied 2750 V and 5 m/s air velocity conditions.