Thus, materials with a low diffusivity should be chosen to reduce the temperature fluctuations. This can be reached for
example with low conductivity materials, especially if the weight of the material is of any practical concern (manual
handling for example), or with high density and high heat capacity materials with reasonably low conductivity as PCMs.
The damping factor is presented in Fig. 6 for the E21 PCM used in this study and for polystyrene materials. To enable the
comparison, an apparent heat capacity has been used for the PCM, considering that the phase change occurs within a temperature range of 3K. It has to be noted that, for example, amplitude of the temperature fluctuation is divided by 10 with only a 2.5 mm PCM slab but a 45.8 mm polystyrene panel.
Since the volume available for the products in a freezer is usually a critical metric of this type of equipment, the smaller
volume used by a PCM packaging may be an advantage and should be considered. Nevertheless, the efficiency of the
damping effect of a PCM packaging only exists if the initial fluctuation temperature oscillates around its melting temperature.
For example, a 2.5 mm PCM slab used at a temperature lower than the solidification zone, keeping it at all time in solid state, would reduce only the amplitude of temperature fluctuation by 1.5 as shown in Fig. 6.
Thus, materials with a low diffusivity should be chosen to reduce the temperature fluctuations. This can be reached forexample with low conductivity materials, especially if the weight of the material is of any practical concern (manualhandling for example), or with high density and high heat capacity materials with reasonably low conductivity as PCMs.The damping factor is presented in Fig. 6 for the E21 PCM used in this study and for polystyrene materials. To enable thecomparison, an apparent heat capacity has been used for the PCM, considering that the phase change occurs within a temperature range of 3K. It has to be noted that, for example, amplitude of the temperature fluctuation is divided by 10 with only a 2.5 mm PCM slab but a 45.8 mm polystyrene panel. Since the volume available for the products in a freezer is usually a critical metric of this type of equipment, the smallervolume used by a PCM packaging may be an advantage and should be considered. Nevertheless, the efficiency of thedamping effect of a PCM packaging only exists if the initial fluctuation temperature oscillates around its melting temperature.For example, a 2.5 mm PCM slab used at a temperature lower than the solidification zone, keeping it at all time in solid state, would reduce only the amplitude of temperature fluctuation by 1.5 as shown in Fig. 6.
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