**2. Experimental methodology and framework**

The aim of the research presented in this chapter is to evaluate the effectiveness of a PCM wall used as a storage medium in reducing the building's air temperature and in improving the occupant's thermal comfort in a Tunisian real house. A specific experimental framework was presented to characterize the PCM wall behavior during the storage and the discharging process (**Figure 2**). In this experimental

the potential of PCM integration in walls and/or building envelopes to increase their thermal inertia to improve their energy performance [2–7]. In this context, Soares et al. [8] proposed the study of the incorporation of PCM drywalls in lightweight steel-framed building envelop. The authors evaluated the impact of PCM drywalls in the annual and monthly heating and cooling thermal performances and energy savings. It was seen that the energy savings due to PCM drywall incorporation range from 46 to 62%. Navarro et al. [9] studied the incorporation of the PCM inside the concrete core slab for cooling purposes. In this context, a prefabricated concrete slab incorporating PCM was used as internal separation inside the building. The results show that the energy savings in building were registered between 30 and 55%. Solgi et al. [2] presented that PCMs have a great influence on enhancing the performance of night purge ventilation and cooling load reduction of buildings in hot-arid climate. It was found that paraffin with 27°C melting point permits the reduction of about 47% in cooling energy. A performance of a collector storage wall system using PCMs was investigated by Zhou et al. [10]. PCM slabs were integrated in the gap-side wall surface to enhance the heat storage. The test was carried out for a whole day with charging period of 6.5 h and discharging period of 17.5 h. They investigated the variations of surface temperature as well as the indoor temperatures. It was found that the indoor temperature was about 22°C during the whole discharging period under given conditions. Barzin et al. [11] presented an experimental study dealing with the building's space cooling by using PCM energy storage

*The rates of energy expenditure in Tunisia (Mehdaoui et al. [1]).*

*Thermodynamics and Energy Engineering*

**Figure 1.**

**148**

in combination with night ventilation. Hence, two experimental tests were achieved: one with PCM-impregnated gypsum boards and the other with normal gypsum board. The result of the experimental investigation shows that substantial electricity saving is about to 73%. Sajjadian et al. [12] presented the study of the potential of using PCMs to reduce domestic cooling energy loads for current and future UK climates. The study used simulations of a high performance detached house model with a near Passivhaus Standard in London, where the impact of climate change effect is predicted to be significant. It was shown that appropriate levels of PCM, with a suitable incorporation mechanism into the building construction, have significant advantages for residential buildings in terms of reducing total discomfort hours. In this context, Royon et al. [13] studied the optimization of PCM implanted in a floor panel envelope of buildings. The study is mainly based on numerical investigation. The numerical results were confronted to experimental ones with the same boundary conditions in order to validate the model. Łukasz et al. [14] presented a parametric study of the thermal performance characteristics of thermal energy storage unit based on PCM integrated in building structure. In order

**Figure 2.** *PCM wall filled with Paraffin-27.*

investigation, a PCM wall was installed in a test cell (**Figure 3**). A framework was installed to follow the indoor air temperatures of the various rooms of the house (with and without PCM). Thirteen T-type copper-constantan thermocouples firstly calibrated with a measurement inaccuracy of 0.2°C were incorporated to PCM wall at the front surface, inside PCM, the back surface and inside the test cell as shown in **Figure 4**. Between the exchanging plates, T-type thermocouples are inserted in both sides of the Plexiglas container to measure the temperature fields on each side of the PCM wall. T-type thermocouples were previously calibrated by using the comparative method. **Figure 4** shows the positions of all thermocouples inside the test cell.

using the data acquisition system, the temperature change at the interior of PCM wall during the charging process is followed. In the second test, the lamp was extinguished and then the PCM temperature fields were followed to evaluate the

*Energy Storage in PCM Wall Used in Buildings' Application: Opportunity and Perspective*

A numerical investigation by using specific FORTRAN program was achieved to

solve the energy and the exergy mathematic relations to evaluate the PCM wall performances by determining the melting phase proprieties (velocity, isotherm,

The proposed numeric investigations describe the heat transfer phenomena inside the PCM wall and evaluate its thermal behavior and effects on test cell ambiance. It allows also the appraisal of the energy and exergy stored during the charging process and to evaluate the thermal characteristics. The considered assumptions are the flow is two-dimensional and laminar, the expansion of the PCM is negligible and the phase change is isothermal. The PCM wall is subjected to an imposed temperature superior to the melting temperature of PCM-27 (**Figure 5**). The other walls are maintained adiabatic (**Figure 5**). Considering the mentioned

> *∂u ∂x* þ *∂v*

> > ¼ � *<sup>∂</sup><sup>p</sup> ∂x* þ *μ<sup>l</sup>*

In the Boussinesq approximation, the source terms *Bu* and *Bv* that appear in the momentum Eqs. (2) and (3) are used to account for this buoyancy force when the PCM is solid. The technique used to cancel the velocity introduces a Darcy term [1].

¼ � *<sup>∂</sup><sup>p</sup> ∂y*

• The quantity of movement relations are given by [1, 23]:

*∂uu ∂x* þ *∂uv ∂y*

*∂uv ∂x* þ *∂vv ∂y*

*<sup>∂</sup><sup>y</sup>* <sup>¼</sup> <sup>0</sup> (1)

*∂*<sup>2</sup> *u ∂y*<sup>2</sup> 

> *∂*<sup>2</sup> *v ∂y*<sup>2</sup>

þ *Bu* (2)

þ *Bv* (3)

*∂*<sup>2</sup> *u ∂x*<sup>2</sup> þ

> *∂*<sup>2</sup> *v ∂x*<sup>2</sup> þ

þ *ρ<sup>l</sup> g* þ *μ<sup>l</sup>*

heat exchanged through the PCM wall during the discharge process.

**3. PCM wall numerical characterization**

*The position of the 13 thermocouples inside the test cell.*

*DOI: http://dx.doi.org/10.5772/intechopen.92557*

• The continuity equation is given by [1, 23]:

melting front evolution, etc.).

*ρl ∂u ∂t* þ *ρ<sup>l</sup>*

*ρl ∂v ∂t* þ *ρ<sup>l</sup>*

**151**

assumptions:

**Figure 4.**

The measurement test was continued for 14 consecutive days during February and March 2016 (from 25/02/2016 to 13/03/2016) to evaluate PCM wall performance. The temperature was measured at front surfaces of PCM wall, at back surfaces of PCM wall, inside the PCM and inside the test cell. The method adopted in the investigation consisted of imposing heating flux (lamp of 120 W) on the exposed PCM wall of the test cell. The simultaneous measurements of the temperature evolution and the heat flux exchanged during charging and the discharging process were accomplished to evaluate the PCM wall thermal performances. A primary experimental test was conducted in the laboratory to determine the characteristics of the phase change material (PCM) during the melting phase. PCM is initially in the solid state at the ambient temperature of the room, 22°C. Then, the right side of the PCM wall was heated by using a special lamp of 120 W held at a distance of 10 cm to ensure the uniformity of heat over the PCM wall surface. By

**Figure 3.** *The test cell.*

*Energy Storage in PCM Wall Used in Buildings' Application: Opportunity and Perspective DOI: http://dx.doi.org/10.5772/intechopen.92557*

**Figure 4.** *The position of the 13 thermocouples inside the test cell.*

investigation, a PCM wall was installed in a test cell (**Figure 3**). A framework was installed to follow the indoor air temperatures of the various rooms of the house (with and without PCM). Thirteen T-type copper-constantan thermocouples firstly calibrated with a measurement inaccuracy of 0.2°C were incorporated to PCM wall at the front surface, inside PCM, the back surface and inside the test cell as shown in **Figure 4**. Between the exchanging plates, T-type thermocouples are inserted in both sides of the Plexiglas container to measure the temperature fields on each side of the PCM wall. T-type thermocouples were previously calibrated by using the comparative method. **Figure 4** shows the positions of all thermocouples

The measurement test was continued for 14 consecutive days during February and March 2016 (from 25/02/2016 to 13/03/2016) to evaluate PCM wall performance. The temperature was measured at front surfaces of PCM wall, at back surfaces of PCM wall, inside the PCM and inside the test cell. The method adopted in the investigation consisted of imposing heating flux (lamp of 120 W) on the exposed PCM wall of the test cell. The simultaneous measurements of the temperature evolution and the heat flux exchanged during charging and the discharging process were accomplished to evaluate the PCM wall thermal performances. A primary experimental test was conducted in the laboratory to determine the characteristics of the phase change material (PCM) during the melting phase. PCM is initially in the solid state at the ambient temperature of the room, 22°C. Then, the right side of the PCM wall was heated by using a special lamp of 120 W held at a distance of 10 cm to ensure the uniformity of heat over the PCM wall surface. By

inside the test cell.

**Figure 3.** *The test cell.*

**150**

*PCM wall filled with Paraffin-27.*

*Thermodynamics and Energy Engineering*

**Figure 2.**

using the data acquisition system, the temperature change at the interior of PCM wall during the charging process is followed. In the second test, the lamp was extinguished and then the PCM temperature fields were followed to evaluate the heat exchanged through the PCM wall during the discharge process.
