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

Spouted Bed and Jet Impingement Fluidization in Food Industry

“…Kluza [32], Kluza and Stadnik [33], Góral and Kluza [34][35][36] thoroughly examined the effect of the apparatus parameters on attainability of fluidal beds of various products. The authors concluded that if the ratio of nozzle symmetry axis spacing to the inner diameters was L/D ≤ 1.8, the bed boiled in a way atypical for jet impingement fluidization.…”

“…The character of the bed behavior was obtained after setting and application of the optimum dependence between the nozzle diameter and the distance between the nozzles. On the basis of the bed development analysis in jet impingement fluidization, Kluza and Stadnik [33], Góral and Kluza [36] performed the assembly of 11 operating heads (nozzle diameter from 11 to 35 mm) with a nozzle pitch four times the nozzle inner diameter L = 4D. The heads were fitted with nozzles in a staggered or aligned configuration.…”

“…As for French fries, proper boiling bed phenomenon occurred when the operating heads with nozzles of inner diameter 20 and 35 mm were arranged by aligning. The papers of Góral and Kluza [36] and Góral et al [39] investigated the problem of heat transfer at vegetable freezing with jet impingement fluidization technique. The authors assumed that the local heat transfer coefficient from the flat plate to air can be estimated from the Nusselt number.…”

“…In most processing cases, a difference between the value of air temperature at the nozzle exit and of the impinging air jet is so small that the air jet temperature within the bed area can be assumed constant [40]. Prior to the development of a calculation model, Góral and Kluza [36] made the following basic assumptions: air jet flow is turbulent within the velocity range enabling reverse fluidization occurrence, air temperature range varies between −50°C and 0°C, material shape corresponds to infinite plate and non-stationary character of heat transfer. Assuming a turbulent fluid flow over the plate-shaped product, the estimation of the local Nusselt number characterizing heat transfer commonly involves using the criterial equation [41]:…”

A Review of Novel and Innovative Food Freezing Technologies

“…The capability and design of the equipment appear to have changed over the years according to the details provided in the various papers. The current configuration is capable of supplying air at −40°C at air velocities ranging from 3.2 to 9.1 m s −1 providing measured heat transfer coefficients (h) of 62 to 200 Wm −2 K −1 , respectively (Góral and Kluza 2012). Relatively little data is provided in these papers on what effect freezing in this system has on vegetable quality.…”