**Energy Storage Heat Pumps Geothermal Energy**

424 Heat Exchangers – Basics Design Applications

[23] Mehrabian, M.A., Poulter, R. (2000), "Hydrodynamics and thermal characteristics of

24, pp. 343-364.

corrugated channels: computational approach", Applied Mathematical Modeling,

**16** 

*Spain* 

**PCM-Air Heat Exchangers: Slab Geometry** 

Energy efficiency and the search for new energy sources and uses are becoming main objectives for the scientific community as well as for society in general. This search is due to various environmental issues and shortages of conventional and non-sustainable energy resources, for example fossil fuels, that are essential to industrial development and to daily life. Free-cooling in buildings, bioclimatic architecture applications, demand and production coupling in renewable energy sources, as solar energy, are examples of thermal energy storage contributions to achieve these objectives. The application of Phase Change Materials (hereafter PCM) in Thermal Energy Storage (hereafter TES) is an expanding field due to the variety of materials being developed. There are four critical considerations for the technical viability of these applications: 1) The features of both the PCM and the encapsulation material must be stable during the system lifetime; 2) A reliable numerical model of the system to simulate different operational conditions; 3) The thermophysical properties of the

Specifically, the solid-liquid phase change phenomenon of the PCM is being widely studied in the field of TES, both experimentally and numerically, because this technology is of great interest among different fields: from applications in electronics, textile, transport... to applications in aerospace or thermo-solar power plants. The incorporation of these materials on the market, as stated before, is conditioned partly by its price. To cope with this situation, manufacturers often sell PCM as non-pure substances or mixtures which, on the one hand, lower their costs but, on the other hand, condition its thermophysical properties so that they are not as well established as in pure substances. Generally, this determining factor leads to a nonlinearity of the temperature dependence of the thermophysical properties of the PCM. This issue is another aspect to consider when simulating the thermal behaviour of these substances. Therefore, it is essential a good determination of these properties as they are input values to the theoretical models that simulate the thermal performance of devices based on these materials, some of which may strongly condition the results of the

When working at ambient temperatures, there are different situations where TES with PCM can be applied. Zalba et al., 2003, presented a comprehensive review on latent heat TES and its applications. The authors remarked that low values of λPCM can lead to real problems in the systems since there could be insufficient capacity to dispose of the stored energy quickly enough. Later, Sharma et al., 2009, presented another review highlighting that there was

**1. Introduction** 

PCM; 4) The cost of the system.

simulations.

Pablo Dolado, Ana Lázaro, José María Marín and Belén Zalba

*University of Zaragoza / I3A - GITSE* 
