Passive study of thermal inertia and thermal behavior of two locals 'test' with and without PCM located in Casablanca city

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Passive study of thermal inertia and thermal behavior of two locals 'test' with and without PCM located in Casablanca city

Article · March 2015

DOI: 10.1109/IRSEC.2014.7059753

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Mustapha El Alami

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Mostafa Najam

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Faraji Mustapha

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Passive study of thermal inertia and thermal behavior of two locals ‘test’ with and without PCM located in

Casablanca city

Amina MOURID¹, Yassine BOUZLOU¹, Mustapha EL ALAMI¹, Mostafa NAJAM¹ and Mustapha FARAJI¹

1LPMMAT, Faculty of Sciences Aïn Chock Hassan II – University of Casablanca, Morocco mouridamina@gmail.com, m.elalami@etude.univcasa.ma

Abstract—To highlight the contribution of the PCM in terms of thermal inertia in the building, we conducted a comparative study of passive heat balance in two cavities scale 1 built in the Faculty of Sciences Ain Chock, Casablanca. The walls of the reference cavity are standards. As against, those of the other cavity incorporate a phase change material (PCM) which fusion begins at a temperature of 22°C and ends at about 45°C. The results of this study show that, first, the oscillation amplitude of the inside temperature decreases greatly in the cavity with PCM.

On the other hand, there is time shift (delay) between these oscillations and those of the internal temperature of the reference cavity, thus demonstrating the ability of PCM to increase the thermal inertia of the walls.

Keywords-component: Thermal inertia, Building, Phase change material (PCM), Casablanca, energy Efficiency

I. INTRODUCTION

Recently, the requirements of thermal regulations for buildings have increased in order to reduce energy consumption.

Therefore, it has become necessary to explore and develop new constructions to levels of performance to produce buildings with very low consumption. Building as it is being built in Morocco, consumes a lot of energy in order to maintain the indoor thermal comfort. The walls have a low thermal inertia due to lack of insulation. To overcome this problem, the phase change material (PCM) has the ability to store and transfer energy in the form of latent heat at a constant temperature (phase change point) [1]. Therefore, not only it increases the thermal inertia of the walls but used too, stored energy in latent form to contribute to this internal thermal comfort

PCMs are divided into three kinds: organic PCM, inorganic PCM and eutectic PCM. Because organic PCMs have various advantages, most researchers have used organic PCM in their research [2], [3], [4] .

The use of PCM in buildings has been studied by many researchers in the last decades. For example, in 2006, Cabeza and al [3] studied a new innovative concrete with PCM in order to develop a product which would not affect the mechanical strength of the concrete wall. They set up 2 real size concrete cubicles in Lleida, Spain, to demonstrate the possibility of using microencapsulated PCM in concrete (with Their experimental results also showed that the energy storage in the concrete enhanced walls leads to an improved thermal inertia as well as lower inner temperatures, in comparison with conventional concrete [5]. A similar study was also carried out by Cabeza et al. [6]. Chandra et al. [5] concluded that a PCM

wall of smaller thickness is more desirable in comparison to an ordinary masonry concrete wall for providing efficient thermal energy storage (TES) as well as better thermal comfort in buildings.

In this work, we present the first results of a comparative passive study between two cavities: one of reference and the other with MCP and both subject to weather conditions of Casablanca. These results are presented in terms of instant internal temperatures to quantify the contribution of PCM in thermal inertia.

This work was developed under the Innotherm II project funded by the Institut de Recherche en Energie Solaire et Energies Nouvelles (IRESEN)

II. DESCRIPTION OF THE EXPERIMENTAL SET-UP A. Phase change material

The phase change material (PCM) used is constituted of 60%

of paraffin within a copolymer (Fig.1). It is encapsulated, in panels (1×1.2×0.0056m³), by using thin Aluminum coverage.

The form of the PCM material is flexible sheets of 5.26 mm thickness which with a melting point of 21.7 and latent heat is 70 kj/kg. The thermal conductivity is 0.18 W/(m.K) in solid phase and about 0.14 W/(m.K) in liquid phase.

B. Presentation of the test cavities

The experimental device was composed of two cavities (Fig.2).

Figure 1: PCM panel

Authors acknowledge the financial support provided by IRESEN

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Figure 1: View of the cells

They are apparently identical, but one of them contains about 24 m² of PCM: the inside faces of it vertical walls are covered by PCM panels. Cubicles dimensions are 3“m”

×3“m”× 3“m”. The north wall is equipped by a window (1m×1m) and a door (2m×1m). The structure of walls consists of hollow bricks (7cm×19cm×25cm) with a phase change materials on the internal side of the cubicles (Fig.3). The external was done with hollow bricks and a cement mortar.

Between these two layers of bricks, there is an air layer of 14cm, Table.1.

C. Instrumentation and measurements

The cells were instrumented with thermocouples K – type in every wall. We have carefully distributed on each wall so that we can have access to average temperatures of all walls, as well as the centers of the two cavities (Fig.4).

Figure 2: composition of the test cell walls

We can also quantify the heat flux lost outwardly (when heated) or the premises (in the case of cooling) by evaluating the thermal resistances. A meteorological station measured inside and outside temperatures, wind speed, global solar radiation and humidity. All devices of the instrumentation are connected to a data logger which is connected, also, to a computer (Fig.5).

Figure 3: Thermocouples Placement on the walls and in PCM Table 1: composition of wall-materials are given from interior to exterior

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Figure 5: Data acquisition.

III. RESULTS AND DISCUSSIONS

The first results from the experimental test in the FSAC cavities, presented in this paper, were obtained from 20^th to 24^th April 2014. Fig.6 and Fig.7 show the time variations of the temperature walls of south and east walls of both cubicles.

Three points can be highlighted from this figure:

 The cell with PCM has a lower temperature fluctuation than the cell without PCM.

 The maximum temperature in the wall with phase change material appears about 1 hour later compared to that without PCM. That because of the thermal inertia of the wall is higher.

 This thermal inertia appears, all the day, due to the melting of a part of the integrated quantity of PCM in the cavity

 Reduction of the magnitude of oscillations by the MCP reaches 2°C by comparing the two temperature profiles for the two cells

Figure 6: Temperature of south walls in both cells and outside temperature.

Figure 7: Temperature of East walls in both cells and outside temperature.

The measurements of two days for the south wall are presented in Figure 8.

The indoor air temperature for the case without PCM fluctuated from13.6 to 24.92, whereas for the PCM case it is varying from 19.37 to 22.53°C. It proves that the PCM walls can decrease the temperature fluctuations by 8.16°C in our tests.

The internal temperature of the cell without PCM fluctuated from 17.96 to 22.07°C while it is varying from 19.37 to 22.53°C (Fig.8).That means using PCM material in such buildings can decrease the temperature fluctuations.

Figure 8: Temperature of south walls during two days.

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IV. CONCLUSION

We conducted a passive study of thermal behaviors of the two 'test' cells of the FSAC. The cavities are subject to weather conditions of Casablanca.

The main objective of this study was to to highlight the thermal inertia of the walls with and without PCM. The conclusions we have derived are such that:

- The results of this study show that including PCM panels reduces fluctuations in air temperature inside the cavity,

- The wall surface temperatures are reduced by using PCM equipment, improving thermal comfort

- There continues to be significant reduction in the amplitude of temperature fluctuations on the walls and in the center of the cavities,

- A phase difference of about 1 hour appeared between the temperature profiles for the two cavities.

References

[1] I. Cerón, J. Neila, M. Khayet, Experimental tile with phase change materials (PCM) for building use, Energy and Buildings 43 (2011) 1869–1874.

[2] S.Jeong, J. Jeon, J. Cha, J.Kim, S. Kim , Preparation and evaluation of thermal enhanced silica fume by incorporating organic PCM, for application to concrete, Energy and Buildings 62 (2013) 190–195.

[3] M.Faraji, M.E. Alami, M. Najam, Thermal Control of Building Using Latent Heat Storage South Wall, Jounal of Mathematics and Computer Science 10 (2014),212-227.

[4] M.Faraji, M.E. Alami, M. Najam, Solar heating of building using phase change material south wall, International Conference on Renewable Energies and Power Quality ICREPO’14 Cordoba (Spain), 8th to 10th April, 2014, Renable Energy and Power Quality (RE&PQJ) ISSN 2172- 038X,No.12,April 2014.

[5] L.F. Cabeza, C. Castellón, M. Nogués, M. Medrano, R. Leppers, O.

Zubillaga, Use of microencapsulated PCM in concrete walls for energy savings, Energy and Buildings 39 (2) (2007) 113–119.

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Nogués, Thermal energy storage with phase change materials in building envelopes, Contributions to Science 3 (4) (2007) 501–510.

[7] S. Chandra, R. Kumar, S. Kaushik, S. Kaul, Thermal performance of a non-air conditioned building with PCCM thermal storage wall, Energy Conversion and Management 25 (1) (1985) 15–20.