Ohmic heating—a new process for the food industry

Stirling, R.

doi:10.1049/pe:19870065

Cited by 58 publications

(29 citation statements)

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“…[24], who looked at the stability of models allowing for different types of flow. More background on this type of process can be found in [5], [12], [15], [26], [27] and [29]. Lacey et al .…”

Section: Introductionmentioning

confidence: 99%

Estimates of Blow-Up Time for a Non-Local Reactive–convective Problem Modelling Ohmic Heating of Foods

Nikolopoulos¹,

Tzanetis²

2006

Proceedings of the Edinburgh Mathematical Society

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In this work, we estimate the blow-up time for the non-local hyperbolic equation of ohmic type, ut + ux = λf (u)/( 1 0 f (u) dx) 2 , together with initial and boundary conditions. It is known that, for f (s), −f (s) positive and ∞ 0 f (s) ds < ∞, there exists a critical value of the parameter λ > 0, say λ * , such that for λ > λ * there is no stationary solution and the solution u(x, t) blows up globally in finite time t * , while for λ λ * there exist stationary solutions. Moreover, the solution u(x, t) also blows up for large enough initial data and λ λ * . Thus, estimates for t * were found either for λ greater than the critical value λ * and fixed initial data u 0 (x) 0, or for u 0 (x) greater than the greatest steadystate solution (denoted by w 2 w * ) and fixed λ λ * . The estimates are obtained by comparison, by asymptotic and by numerical methods. Finally, amongst the other results, for given λ, λ * and 0 < λ − λ * 1, estimates of the following form were found: upper bound + c 1 ln[c 2 (λ − λ * ) −1 ]; lower bound c 3 (λ − λ * ) −1/2 ; asymptotic estimate t * ∼ c 4 (λ − λ * ) −1/2 for f (s) = e −s . Moreover, for 0 < λ λ * and given initial data u 0 (x) greater than the greatest steady-state solution w 2 (x), we have upper estimates: either c 5 ln(c 6 A −1 0 + 1) or + c 7 ln(c 8 ζ −1 ), where A 0 , ζ measure, in some sense, the difference u 0 − w 2 (if u 0 → w 2 +, then A 0 , ζ → 0+). c i > 0 are some constants and 0 < 1, 0 < A 0 , ζ. Some numerical results are also given.

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Section: Introductionmentioning

confidence: 99%

Estimates of Blow-Up Time for a Non-Local Reactive–convective Problem Modelling Ohmic Heating of Foods

Nikolopoulos¹,

Tzanetis²

2006

Proceedings of the Edinburgh Mathematical Society

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“…The main advantages of ohmic processing are the rapid and relatively uniform heating achieved, together with the lower capital cost compared to other electro heating methods such as microwave and radio frequency heating. Ohmic heating technology has been accepted by the industry for processing liquids and solid liquid mixtures [1] . In the absence of a hot wall, ohmic heating provides a considerable advantage for foodstuff applications, by not only avoiding the degradation of thermo-sensitive compounds through over-heating but also by reducing the fouling of treated food surfaces during processing [2] .…”

Section: Introductionmentioning

confidence: 99%

“…Electromagnetic heating, on the other hand, has been successfully used for efficient pasteurization of food products in the recent years [8] . However most of the studies have concern over the sterilization of food products containing particles [9][10][11][12][13][14]19] . There are only a few scientific and technical studies dedicated to continuous fluid treatment by ohmic heating [15][16] .…”

Section: Introductionmentioning

confidence: 99%

The Effect of Buoyancy Force in Computational Fluid Dynamics Simulation of a Two-Dimensional Continuous Ohmic Heating Process

Salih¹,

Choong²,

Sergie³

et al. 2009

American J. of Applied Sciences

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Problem statement: Earlier work on ohmic heating technique focused on viscous food and foods containing solid particles. In this study, the use of ohmic heating on sterilization of guava juice is carried out. Computational fluid dynamics is used to model and simulate the system. Approach: Investigate the buoyancy effect on the CFD simulation of continuous ohmic heating systems of fluid foods. A two-dimensional model describing the flow, temperature and electric field distribution of non-Newtonian power law guava juice fluid in a cylindrical continuous ohmic heating cell was developed. The electrical conductivity, thermo physical and rheological properties of the fluid was temperature dependent. The numerical simulation was carried out using FLUENT 6.1 software package. A user defined functions available in FLUENT 6.1 was employed for the electric field equation. The heating cell used consisted of a cylindrical tube of diameter 0.05 m, height 0.50 m and having three collinear electrodes of 0.02 m width separated by a distance of 0.22 m. The sample was subjected to zero voltage at the top and bottom of electrodes while electrical potential of 90 volts (AC 50-60 Hz) was set at the middle electrode. The inlet velocity is 0.003 m sec  1 and the temperature is in the range of 30-90°C. Results: The simulation was carried with and without buoyancy driven force effect. The ohmic heating was successfully simulated using CFD and the results shows that the buoyancy has a strong effect in temperature profiles and flow pattern of the collinear electrodes configuration ohmic heating. A more uniform velocity and temperature profiles were obtained with the buoyancy effect included. Conclusion: For accurate results, the inclusion of buoyancy effect into the CFD simulation is important.

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“…The problem was considered initially in [19] where the stability of models allowing for different types of flow is studied. More background on this type of process can be found in [5,4,9,20,22,24]. In [15] problem (1.1) is also studied and it is found that for f decreasing with for instance either f (s) = e −s or f (s) = (1 + s) −p , p > 1, satisfy (1.2).…”

Section: Introductionmentioning

confidence: 99%

Numerical Solution of a Nonlocal Problem Modelling Ohmic Heating of Foods

Nikolopoulos

2009

Comput. Methods Appl. Math.

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-An upwind and a Lax-Wendroff scheme are introduced for the solution of a one dimensional non-local problem modelling Ohmic heating of Foods. The schemes are studied regarding their consistency, stability and the rate of convergence for the cases that the problem attains a global solution in time. A high resolution scheme is also introduced and it is shown that it is total-variation-stable. Finally some numerical experiments are presented in support of the theoretical results.

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Ohmic heating—a new process for the food industry

Cited by 58 publications

References 1 publication

Estimates of Blow-Up Time for a Non-Local Reactive–convective Problem Modelling Ohmic Heating of Foods

Estimates of Blow-Up Time for a Non-Local Reactive–convective Problem Modelling Ohmic Heating of Foods

The Effect of Buoyancy Force in Computational Fluid Dynamics Simulation of a Two-Dimensional Continuous Ohmic Heating Process

Numerical Solution of a Nonlocal Problem Modelling Ohmic Heating of Foods

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