Heat transfer coefficient in impingement fluidization freezing of vegetables and its prediction

The objective of this work was to obtain experimental characteristics of the heat transfer coefficient during impingement fluidized freezing of vegetables, using a heat flux sensor. The material undergoing freezing was formed from vegetable slices measuring 3 × 3 × 0.5 cm. The formula Nux = 0.353∙Rex0.608 can be used to describe the dependence of the heat transfer coefficient on the process parameters and is valid for the 8000 < Rex < 30000 range. The model was validated by a statistical evaluation of the relative error, the regression characteristics for the Nusselt number, and an estimate of the agreement between the computated and experimental distributions of the Nusselt number. A strong correlation was found between the heat transfer coefficient values from the proposed model and the experimental values.

► An empirical equation was obtained for the heat transfer coefficient during impingement fluidized freezing of vegetable. ► Maximum prediction error with the proposed model is ±20%. ► Heat transfer coefficients under the studied conditions ranged from 62 up to 200 W m−2K−1 subject to air velocity.