A Study on Chemical Heat Pipe with Energy Upgrading Function at High-Temperature level

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The heat excahge characteristics accompanied by an exothermic reaction at heat demand end of a chemical heat pipe system using SO_2/O_2/SO_3 reversible thermochemical reaction was discussed in a lab-scale unit. The effects of the reactant gas composition, the mass flow rate of reactant gas and heat exchange medium on the reaction and the heat exchange characteristics were discussed. Furthermore, a cpmparison between the experimental and calculated results obtained by using a two-dimensional mathematical model, in which the reaction and heat transfer was considered simultaneously, was performed. It was found that the heat exchange characteristics obtained from experiments can be explained tendentiously by the calcutated results. Under the adiabatic conditions, the temperature difference between the outlet and the inlet of the heat exchange medium increased with an increase of the mass flow rate of SO_2 and a decrease of the mass flow rate of the heat exchange medium, while the efficiency on the heat exchange process decreased with an increase of the mass flow rate of SO_2 and a decrease of the mass flow rate of the heat exchange medium.In order to examine the temperature upgrading effect of the proposed chemical heat pipe, a calculation was made to estimate the effect of reaction pressure on the temperature upgrading. It is shown that the temperature difference, that is, the effect of temperature upgrading increased with an increase in both the molar ratio of SO_2 and the pressure in the reactor of heat demand end. On the other hand, it is shown that the value of COP increased with an increase in the molar ratio of SO_2 but decreased slightly with an increase of pressure in reactor of heat demand end. Consequently, it was clear that SO_2/O_2/SO_3 system can be to apply as a chemical heat pipe with chemical heat-pump function.