## 4 Experimental Results
### Thermophysical Properties of n-docosane in the Container
Figure 10 gives the curves of temperature step and heat flux values of both heat flux sensors in order to measure the heat of absorption of n-docosane from 42.0 to 43.0 \({}^{\circ}\)C; Figure 10a refers to the lower heating plate, while Figure 10b refers to the upper heating plate. The areal enthalpy of the specimen at the temperature step can be calculated by the area enclosed by the heat flux curve and \(q_{qui}\). Similarly, other temperature step measurement results can be obtained. According to Equations (9)-(14), the results of heat of absorption for full-scale specimen and n-docosane at each temperature step can be calculated, as shown in Figure 11, in which (**a**) presents the heat of absorption per unit temperature step for both full-scale specimen and n-docosane, and (**b**) presents the accumulated total heat of absorption for n-docosane. It can be found that the temperature step was 2 \({}^{\circ}\)C when the temperature was under 40 \({}^{\circ}\)C and above 50 \({}^{\circ}\)C, while the temperature step was 1 \({}^{\circ}\)C between 40 and 50 \({}^{\circ}\)C. The design of this temperature step is intended to not only accurately measure the phase change temperature range but to also effectively save testing time. Figure 11: Testing results for heat of absorption of full-scale specimen and n-docosane. (**a**) Heat of absorption per unit temperature step. (**b**) Total heat of absorption. Figure 10: Curves of temperature step and heat flow values on both plates. (**a**) Bottom plate. (**b**) Top plate. Figure 11 clearly shows that the full-scale specimen has a distinct endothermic zone in the test temperature interval, which is due to the large amount heat of absorption by phase change of n-docosane inside the full-scale specimen. In addition, when the temperature changes from 42 to 43 \({}^{\circ}\)C, the heat of absorption curve begins to deviate and the phase change of n-docosane begins. The initial temperature point of phase change refers to the mean temperature 42.5 \({}^{\circ}\)C. Similarly, the end temperature point of phase change refers to 48.5 \({}^{\circ}\)C.  
In addition, due to the mass of n-docosane being 2.614 kg, the specific heat values of solid and liquid phases are calculated by Equation (14). Figure 12 gives the sensible specific heat value of n-docosane. Then, test results were fit to obtain the baseline, which refers to the sensible specific heat value. Based on the results of Figure 11, it can be concluded that the total enthalpy of n-docosane in the phase change range (42-49 \({}^{\circ}\)C) was 259.92 kJ/kg. The sensible specific heat in the phase change range can be obtained from Figure 12. As such, the total sensible enthalpy, which was 16.46 kJ/kg, was calculated by the area enclosed by the sensible specific heat from 42 to 49 \({}^{\circ}\)C. Therefore, the latent enthalpy of n-docosane was 243.46 kJ/kg. Compared with the published data [7; 28; 29; 30; 31] in which the initial phase change temperature of n-docosane was from 40.67 to 43.15 \({}^{\circ}\)C, and the latent heat is from 194.6 to 241.3 kJ/kg, the measurement results in this paper are reasonable.