Numerical simulation of fish freezing process by immersion cooling and cold air blasting methods

A three dimensional simulation of cooling and freezing process of fish as a complex geometry is presented. The 3d geometry of the fish was produced by digitizing and the thermo-physical properties of the fish were considered as functions of temperature and water content of the fish. Heating loads and product temperatures during chilling, freezing and post cooling processes for immersion cooling method in brine and for cold air blasting method were predicted. The influence of effective parameters such as initial temperature and fish water content are also investigated on processing time. Because of the slow freezing rate in immersion cooling technique, the results show that the initial temperature of fish highly affects freezing time. We suggest that a combination of immersion and cold air blasting methods will decrease the freezing time in comparison with immersion method when solely applied. Comparison of temperature distribution in present study shows a good agreement with other numerical and experimental results

Effects of gas properties and geometrical parameters on performance of a vortex tube

AbstractIn this paper, energy separation effects in a vortex tube have been investigated using a CFD model. A numerical simulation has been undertaken, due to the complex structure of flow. The governing equations have been solved by the FLUENT™ code in a 2D compressible and turbulent model. Three turbulent models, namely, RSM, Standard k-epsilon and Spalart–Allmaras, have been used. The Spalart–Allmaras turbulent model, which is the first equation, was not so bad in predicting temperature results, although the Standard k-epsilon model better predicts the results in most regions. The effects of geometrical parameters have been investigated. The results have shown that the hot outlet size and its shape do not affect the energy distribution in the vortex tube, and a very small diameter will decrease the temperature separation. Different kinds of gas have been examined for the vortex tube, and it was concluded that using helium as a refrigerant produces the largest energy separation

Optimization of the pitch to chord ratio for a cascade turbine blade in wet steam flow

This study has used shape optimization by the genetic algorithm to gain the suitable pitch to axial chord ratio for a cascade turbine blade. The innovation of the present paper is the modification of the Zweifel coefficient for the wet steam flow passing through the steam turbine cascade. Wetness fraction (WF), average droplet radius (ADR), momentum (MO), pressure loss (PL), and isentropic efficiency (IE) at the exit of the cascade turbine blade in wet steam flow are selected as the objective functions. The ultimate goal was to minimize the wetness fraction, average droplet radius at the outlet of the blade, and pressure losses of the passage and maximize the efficiency and momentum at the outlet together. The Navier-Stokes equations,SSTk-ω turbulence model, and the Eulerian-Eulerian approach are applied for modeling the condensing flow. The agreement gained between the numerical results and the experimental results is satisfactory. A pitch to axial chord ratio of Pi/AC = 0.76 is suggested, and the modified Zweifel coefficient for wet steam flow in the cascade is proposed CZF=0.62. In the optimal case, the wetness fraction and the average droplet radius at the outlet decrease 3.59% and 1.94%, respectively, and the momentum increases 7.28%. In addition, the optimal case compares with original case, the isentropic efficiency decreases 2.48% and the pressure losses increases 2.15%. © 2022 Elsevier Lt