Termodinamica

In figures 7c, d, the experimental and theoretical results of the salt temperatures TCa and TMn are compared. TM was 1050C and TL was 250C. The experimentally measured temperature lift ΔT was 180C, white the theoretical result was 190C. The results of ΔT under different operation conditions are listed in Table 5. From figure 7 and Table 5, it was concluded that the theoretical results agreed wellwith the experimental results. Since the head loss during system operation was not considered in the theoretical analysis, there was small difference between the theoretical results and the experimental results.
It was also found from Table 5 that the temperature lift was smaller in the case of the initial states of CaCl2 · 2NH3 and MnCl2·6NH3, compared with that for the initial states of CaCl2· 4NH3 and MnCl2·6NH3. This was due to the fact that at the same TM, the decomposition pressure was higher for the reaction of CaCl2 · 4/8NH3. During the high pressure process PH in the system of operation, the salt of CaCl2 was decomposed and the salt of MnCl2 was synthesized. Since the synthesis pressure of MnCl2 is the same decomposition pressure of CaCl2, as show in Figure 1b, the synthesistemperature of MnCl2 was the higher for the initial states of CaCl2 · 4NH3 and MnCl2·6NH3. Thus, the temperature lift ΔT was larger in this case.
The main focus of this article was the solid-gas reaction in the head transformer system. The results of the reaction degrees x24, x48, and x26 are show in Figure 8. The left and right dotted lines in Figure 8a represent time 1 (at about 5000 s) and time 2(at about 15000 s), respectively; while the left and right dotted lines in Figure 8b represent time 3 (at about 7000 s) and time 4 (at about 23000 s), respectively.
The molar contents of CaCl2 · 2NH3, CaCl2 · 4NH3, and CaCl2 · 8NH3 at the each time are shown in Figure 8c. At times 1 and 2, the salt of CaCl2 is mainly in the form of CaCl2 · 2NH3 and CaCl2 · 4NH3, respectively. The fraction ofCaCl2 · 8NH3 in the reactive block with CaCl2 is small. Therefore, the main reaction in the case shown in Figure 8a was the reaction of CaCl2 ·2/4NH3. Similar to the results at time 1 and 2, the major fraction of the salt of CaCl2 at time 3 and 4 was CaCl2 · 4NH3 and CaCl2 · 8NH3, respectively. Thus, the main reaction in the case shown in Figure 8b was the reaction of CaCl2 · 4/8NH3.
In additionto the main reaction discussed above, the other reaction between CaCl2 and NH3 in the case shown in Figures 8a, b was also found. Therefore, it was concluded that the reactions of CaCl2 ·2/4NH3 and CaCl2 · 4/8NH3 might occur simultaneously in the solid- gas reaction heat transformer system. It was the necessary to investigate the favored conditions for the simultaneous occurrence of multistepreaction between CaCl2 and NH3. In this article, the investigated conditions included the driving temperature TM and the ambient temperature TL, the relative gas volume Vg/VB and the initial charging pressure P0, the specific heat transfer area A/VB and the heat transfer coefficient UMn of MnCl2 during synthesis process. The impacts of the simultaneous occurrence of multistep reactions of the systemperformance indicators, which included the temperature lift ΔT, specific power, and system COP, were also investigated.

Favored conditions for the simultaneous occurrence of multistep reactions
As mentioned earlier, the system operation was composed of two processes: the high pressure process PH and the low pressure process PL. In the high pressure process PH, CaCl2 was decomposed and MnCl2synthesized; and the low pressure process PL, MnCl2 was decomposed and CaCl2 was synthesized. For simplicity, each process was stopped when the reaction degree x reached 0.9 in synthesis or 0.1 in decomposition. The parameters are listed in Table 6, except for those specifically mentioned.
The variation ranges of the reaction degrees x24 and x48 during the system operation were defined as...