Study on Nanostructured and Metallic PCM materials for Heat Storage Systems..

Short description

Design of heat storage systems based on nano-PCMs,  thermal characterization of  phase change materials

Main technical features

L1s heat storage system is one of the basic elements for such a reduction in the cost of energy as it allows to improve their functioning and increase their capac operational units. A solution with considerable potential for reducing costs is based on a latent heat storage systems using materials to change (PCM).

Mixtures of PCM nanopcm nanoparticles, known and appropriate, appear to be able to raise both the thermal capacity that the diffusion of the means of accumulation.

The nanopcm PCM is best achieved by using as a mixture of sodium nitrate salts 3.8360 %wt (nano) and potassium nitrate (KNO 340 %wt as nanoparticles) and 1 % of a mixture of oxides of silica (SiO 2) and alumina (Al 2O 3) between 2 and 200 nm

Following the excellent results obtained with the micro extruder bivite, thought was given to use the very method for the production of larger quantities (being the micro extruder limited at a range of 20 g), based on these parameters.

Following the excellent results obtained were developed different ways of mixing at a high temperature.

 

  • Mixing with extruder:

Has been chosen extruder bivite bausano MD 30 of the model

Extrusion production process is a continuous material, as a threadlike element, film or cylindrical symmetry which, through the transition from solid to the malleable cast or, at least, moving the material through one or more heated and endless screws with variable geometry, obliged to rotate within a cylinder that contains it. In our case, the idea was to exploit the rotation of vines for blending high temperature, the PCM and nanoparticles screws of the extruder have a diameter of 30 mm and 25 mm wheelbase Cylinder heating areas (55 mm wide) shall be seven and have means for adjusting the temperature profile. The maximum number of turns of the vines is 95.4 rpm. This method has failed and for this were investigated other high temperature mixing methods.

 

  • Mixing with dispermat:

Is an apparatus used for the mixing of chemical elements in aqueous solutions through a disc rotation sfrangiato perpendicularly to its surface with the fins, present in different number and size. It can also be used at high temperatures were established nanopcm production at a time of 500 g (495 g and 5 g of PCM nanoparticles).

Again, the results have not been satisfactory.

 

  • Mixing with magnetic stirrer

A magnetic stirrer with heating is chosen by means of an electrical resistance under the plan of support may be increased to 370 °C

The sample preparation was the same as the first two methods, the quantity of material used was, however, much more limited. Moreover, instead of steel containers were used 60 ml beaker. The chosen temperature during the melting process remained at 350 °C.

Once rendered the sample was supported over a plate at 370 °C and stirring with a speed of 1 200 rpm. The same was then wrapped with the mattress of ceramic material and then finally there were two Magnetic rods. Finally the beaker is covered in the same way as the containers used previously.

 

  • 2ºmethod mixing in aqueous solution:

In particular, since the solubility of Nano 3 is 912 g/l and that of KNO 3 is 320 g/L, thought was given to increase the concentration of salts up to 100 g/l, 300 g/l and 500 g/l, this has made it possible to produce a quantity higher than the quantity of water nanopcm not too high.

Innovative aspects

To measure the heat capacity was used a calorimeter differential scanning (DSC).

Thermal properties assessed were: The starting temperature, the merger (tonset)

Melting temperature (tfusione), the heat of fusion (h) and the specific heat.

Materials after they have undergone the thermal cycles were analysed in the DSC

Scanning electron microscope (SEM) to help the dispersion of nanoparticles in salt.

 

Finally, were analysed various possible methods to produce micro nanopcm capsules for use in cement for thermal storage to medium temperatures.

These micro capsules could provide benefits in the accumulation of high temperature heat in cement.

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The University of Perugia

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JP.STE.363:Study on Nanostructured and Metallic PCM materials for Heat Storage Systems..
Joint Programme / IRP / ECRIA
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