The thermal conductivity of fresh lamb meat, offals and fat was measured over the temperature range -40°C to +30°C using a guarded hot plate apparatus. Simple empirical equations were presented for the conductivity of high-moisture (65 to 80%) meat and offals. With independently obtained values of physical parameters, several theoretical models were tested to sec if thermal conductivity could be calculated from composition and temperature. Over a wide range of compositions and temperatures, best predictions (in terms of mean, standard deviation and range of errors) were obtained with Levy's modification to the Maxwell-Eucken equation. Its accuracy was not unduly sensitive to the uncertainties in the values of the physical parameters, the prediction errors remaining in the range ± 10% for all reasonable values of the latter.
"and extended to the negative temperatures. The water activity was measured and modelled by a GAB l of Levy was used for the thermal conductivity due to its suitability in the low temperature ranges (Pham and Willic, 1989). The bound water (X b = 0.14) was calculated from the curves obtained by DSC (Differential Scanning Calorimetry) and the initial freezing temperature ( determined thanks to experiments. "
[Show abstract][Hide abstract] ABSTRACT: The objectives of this work were to evaluate the advantages brought by using cryogenic freezing in comparison to blast air freezing with respect to weight losses and freezing times during food freezing. A mathematical model was then developed to predict the freezing time and the weight loss of food during freezing in very low ambient temperature. The model, first validated with experimental results, was then used to study the combination of cryogenic freezing and conventional freezing on different products such as meat and bread. The influence of the time spent in a cryogenic freezer to the freezing time, the mass loss and the energy consumption was especially evaluated. Results have shown that the behaviour of the product strongly depends on its thermophysical properties and its geometry/size and that there seems to be a linear relationship between the time spent in the cryogenic freezer, the freezing time and the energy consumptions.
ICR2015, 24th IIR International Congress of Refrigeration, Yokohama, Japan; 08/2015
"Fig. 3 shows that, since k water /k solids is relatively low, the choice of effective thermal conductivity model is not critical for Class I foods. Pham and Willix (1989) performed measurements on the effective thermal conductivity of meat, fat and offal between À40 °C and +30 °C, and compared the results to the predictions of six of the effective thermal conductivity models plotted in Fig. 1. They found that for the unfrozen materials (Class I foods) any of the six models provided satisfactory predictions, consistent with the previous discussion. "
[Show abstract][Hide abstract] ABSTRACT: In this study, it was shown that effective thermal conductivity models that are functions only of the components’ thermal conductivities and volume fractions could not be accurate for both granular-type porous foods (“external porosity”) and foam-type porous foods (“internal porosity”). An extra parameter is needed to make the model sufficiently flexible to allow it to be applied to porous foods with a range of different structures. A number of effective thermal conductivity models contain the required extra parameter, and of these, Krischer’s model appears to have received the greatest use in the food engineering literature; however, for isotropic materials it is recommended that a modified Maxwell model be used instead, because it assumes an isotropic physical structure, unlike Krischer’s model, and because the numerical value of the extra parameter may be estimated based on whether the food has internal or external porosity. A new procedure for predicting the effective thermal conductivity of non-frozen porous foods is presented as a flowchart.
"The model considers the Protein, Fat and Ash content, as a function of the thermal conductivity. Spells  model was considered by Pham  to obtain the conductivity of various kinds of meat. Comini et al. and Spells models deemed only the moisture content as the main parameter, which influenced the thermal conductivity. "
[Show abstract][Hide abstract] ABSTRACT: Thermal conductivity and thermal diffusivity of 'Hashi' camel meat were measured and predicted over a temperature range from 5-45°C. Thermal conductivity and thermal diffusivity were determined using a line heat source probe. The obtained values for thermal conduc vity varied from 0.482 to 0.494 W/m.°C and the percent standard errors varied from 3.2 to 5.2%. The thermal diffusivity values varied from 1.26 x 10-7 to 1.29 x 10-7 m2/s and the percent standard errors varied from 8.7 to 12.3%. Experimental values of the 'Hashi' camel meat were compared with the thermal conductivities and thermal diffusivities calculated using different empirical models.
Journal of King Saud University - Science 01/2004; 16(2):153-160.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.