2.1. Introduction of Materials and the Wall Structures

A composite phase change thermal storage material is the main research object of this paper. This material can not only effectively overcome the shortcomings of single inorganic or organic phase change materials, but also improve the application effect of phase change materials and expand their application scope. In this paper, decanoic acid is taken as an example. The solid-phase temperature of decanoic acid is 31.5 °C, and the liquid-phase temperature is 38.5 °C. The complete working temperature range of decanoic acid is 31.5 °C < T < 38.5 °C, and its specific thermal parameters are given in Table 1. Furthermore, all materials of the studied PCM wall are listed in Table 1.

Thermal parameters of phase change materials.

The research object of this study is the basic wall component unit composed of a standard wall block and standard mortar, as shown in Figure 1. The length, the width and the height of the block is LWH and the width of masonry joints is d. According to the size of standard wall blocks and the width of standard masonry joints, wall parts consisting of 390 mm × 240 mm × 190 mm blocks and 10 mm wide masonry joints were studied.

Schematic diagram of basic unit of block wall.

Using Abaqus finite element analysis software to simulate the heat transfer of wall parts under steady state can visually show the heat transfer of different materials in different areas of wall parts, indirectly indicating their heat preservation and storage function. To better reflect the heat transfer situation in different areas to obtain more accurate and qualitative analysis results, the research object was chosen to be a three-layer staggered-joint wall. The main body of the studied wall consists of nine blocks, the total volume of which is equal to the block and masonry joints of the unit. There are two horizontal masonry joints between the three-layer walls, and the longitudinal masonry joints are from top to bottom. The three layers are two, three, and two blocks, respectively, as shown in Figure 2.

Schematic diagram of the three-layer staggered-joint wall.

Assuming that the joints between the blocks and mortar are homogeneous materials, basic calculation parameters such as the density, specific heat, thermal conductivity, and latent heat of each material should be provided before the heat transfer simulation in the wall model. In this study, the materials’ parameters of mortar, slag cotton brick, decanoic acid, concrete, lightweight insulating brick were used for comparisons and compounding calculations. All materials’ general thermal parameters are shown in Table 1.