ASSEMBLY PHASE

Before positioning the thermocouple, the weighing of the largest container was carried out, thus obtaining a value equal to 65 g.

Then the thermocouple is installed on the bottom of the container, which we will indicate as T0, fixing it with a very simple scotch tape.

Figure 36 Larger container with thermocouple T0 on the bottom

46 Subsequently, the weighing of the wood sawdust is carried out obtaining a value equal to 370 g and immediately after it is introduced into the container and positioned in such a way as to leave the space for the smaller container.

Regarding the thermodynamic properties of sawdust, reference was made to the tabulated values of the COMSOL Multiphysics 5.3a software.

In fact, the software allows, as we will see later, to select the material present in the database and to have already tabulated values. In this case, for sawdust, thermal conductivity values equal to 0.125 ^𝑊

𝑚𝐾, of specific heat equal to 1850 ^𝐽

𝑘𝑔𝐾, while for density, being dependent on temperature, values will be obtained that will vary with temperature variation, but which however, it will have values that will be around 200 ^𝑘𝑔

𝑚³ density. [43]

In order to have the most stable values possible in the monitoring phase in the laboratory, we tried to keep the weight of the sawdust unchanged.

Figure 37 Application of wood sawdust

After the phase of placing the sawdust inside the first container, the assembly phase continues with the installation of the thermocouple (T3), outside the second container, on the bottom and then facing the part of sawdust.

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Figure 38 Smaller container with thermocouple T3 on the bottom, outside

In this case, for a better specification, also the polypropylene container was weighed obtaining a value equal to 22.5 g.

To avoid a possible poor temperature recording, also for the thermocouple T3 has been fixed on the bottom of the container with adhesive tape.

As you can see from the photo, the smallest container has had a good adherence to the space released inside the sawdust.

In such a way as to avoid as much heat loss as possible due to conduction since there will be many due to the simple fact that the entire system is exposed, from the top, outside.

The next step of the assembly phase is the insertion into the smaller container of the phase change material.

As can be seen from the figure 39, the material in this case is the lard, in which an additional thermocouple (T4) has also been applied to the bottom of the container, which will serve to monitor the PCM temperature.

Applying the lard there were numerous difficulties since the container tended to smear and made it more difficult to apply the adhesive tape for fixing the T3 thermocouple.

Although we found problems in the installation phase of the lard, we tried to keep the weight of the material unchanged in order to have a homogeneity in the monitoring phase and obtain more or less similar values.

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Figure 39 PCM into the smaller container with thermocouple T4 for the bottom part

The weighing of the phase change material was carried out subsequently, obtaining a value of 200 g.

Subsequently, a further thermocouple (T1) was applied, which will mainly serve for recording the average or PCM environmental temperature.

Immediately afterwards, inside the container of the phase change material, the aluminium container in the form of a truncated cone was applied, which will serve for the insertion of hot water.

Figure 40 Last container of aluminium

49 As you can see from the image the last thermocouple (T2) has been applied for monitoring the cooling of the hot water inside the aluminium container.

Also for this last insertion, both the water and the aluminium container were weighed, obtaining respectively 73 g and 27 g of weight.

The water, as previously mentioned, comes first the boiler and then poured into the aluminium container.

To monitor the achievement of the correct water operating temperature, a digital thermocouple has been introduced with display inside the boiler.

To have more differentiations of the same problem, we poured the water inside the aluminium container at different temperatures so as to have different trends and be able to verify the behaviour of the material in phase change to various thermal stresses.

At the end of each recording, the water container is removed and the water is poured into the kettle, so as to avoid waste.

Subsequently, the assembly process was applied for the butter, which has a weight of 250 g.

Figure 41 Application of the butter inside the smaller container

Immediately after weighing and inserting into the butter container, thermocouples were introduced while maintaining the same arrangement for all tests and for all phase change materials.

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Figure 42Application of the smaller container inside the whole system

Then, the same procedure is done for the meat fat. In fact is applied 250 g of fat into the smaller container and it was studied the temperature trend and the thermal exchange between hot water and organic compound.

Figure 43 Meat fat applied into the smaller container

Finally, as last process of the first step of temperature recording, it was applied paraffin wax into the smaller container, for having a complete comparative analysis between organic waste materials and a generic organic compound used for thermal storage.

In this case it is installed into the smaller container a paraffin wax with a weight of 140 g.

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Figure 44 Paraffin wax into the smaller container