Energy and Buildings 153 (2017) 392–402
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Polyurethane foams with microencapsulated phase change material: Comparative analysis of thermal conductivity characterization approaches C. Amaral a,b,∗ , R. Vicente a , V.M. Ferreira a,b , T. Silva a,b,c a
RISCO, Civil Engineering Department, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal CICECO, Aveiro Institute of Materials, Civil Engineering Department, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal c 2GO OUT Consulting, SANJOTEC, S. João da Madeira, Portugal b
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Article history: Received 21 March 2017 Received in revised form 21 July 2017 Accepted 7 August 2017 Available online 10 August 2017 Keywords: Guarded hot plate Hot box heat flux meter Microencapsulated phase change material (mPCMs) Rigid polyurethane foams (RPU) Thermal conductivity Transient plane source
a b s t r a c t The use of thermal insulation materials is regarded as the most effective passive measure of energy savings in buildings. Rigid polyurethane foams (RPU) are commonly used as the insulation layers of opaque building envelope solutions, as well as for other applications in field of transportation, textile industry and electrical appliances, accounting for almost one-third of the polyurethane market. In the assessment of the energy performance of buildings, insulation materials, such as RPU foams have good insulating properties – low thermal conductivity – however their thermal regulation capacity can be enhanced by the incorporation of phase change materials (PCMs). In this paper, three different approaches (flux meter approach, the guarded hot plate approach and the transient plane source approach) are presented to determine the thermal conductivity of RPU foams with and without the incorporation of PCMs based on steady state method and transient method. In addition, this work presents and discusses the comparison between measurements amongst the three approaches revealing the important factors that should be considered to determinate the thermal conductivity of the RPU foams with PCMs, particularly in the temperature range during PCMs phase change transition (solid/liquid state). © 2017 Elsevier B.V. All rights reserved.
1. Introduction Energy consumption in the residential, commercial and public services sector is responsible for consuming 40% of the total final energy use of the European Union (EU) [1–4]. Therefore, it is necessary that the energy consumption of buildings decreases, but without compromising the living standards and thermal indoor comfort requirements [5]. Thermal energy storage (TES) systems have gained much attention in the last decade, particularly as a potential approach to improve the energy efficiency in buildings. In this context, phase change materials (PCMs) appear as a potential solution to increase the thermal efficiency in buildings since they can store more energy, in the latent form, than the typical sensible energy stored by most common building materials [6–9]. The main advantage of the integration of latent heat thermal energy storage systems (LHTES) using PCMs into building solu-
∗ Corresponding author at: RISCO, Civil Engineering Department, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal. E-mail address:
[email protected] (C. Amaral). http://dx.doi.org/10.1016/j.enbuild.2017.08.019 0378-7788/© 2017 Elsevier B.V. All rights reserved.
tions is the high storage density for small temperature intervals and when coupled with other active systems can increase the energy efficiency in new and refurbished buildings [7,10–14]. This storage capacity increases the building thermal inertia, and it is expected to contribute to solving the time mismatch between the energy supply and demand. One of the most used solutions, to improve the thermal behaviour of building envelopes and enhance the building indoor thermal regulation, is the use of thermal insulation materials. The rigid polyurethane foams (RPU) is one of the most knowledge material that is used on a large different sectors, such as for medicine transportation, for decoration and appliances and also in the building sector, mainly as insulation layers incorporated into opaque envelope building solutions [15,16]. Compared with others known typically insulating materials, the RPU are highly competitive, because their good thermal and physical properties, such as: i) low thermal conductivity, ii) high mechanical and chemical stability and iii) their compatibility and easy form to be incorporated into others facing materials [15]. Therefore, besides of the good insulation properties that the RPU foams have, their thermoregulation capacity can be improved using PCMs [17–20]. In this case, the introduction of PCMs will provide an extra heat capacity to the
