Reactor Modelling

Steady state modelling of receiver performance for example involves detailed analysis of the energy balance of finite elements of receivers. Taking into account incident flux, re-radiation and reflection to and from all other receiver elements, convective heat loss plus the action of the working fluid. Successful modelling of receivers in this way gives predictions of temperature distributions and overall receiver efficiency. It thus allows alternative receiver geometries to be investigated for performance improvement.

Another line of investigation concerns the optimisation of the heat recovery part of the ammonia based thermochemical system. As part of this investigation, performance modelling of the lab scale synthesis reactor represents a necessary step towards an improved performance of the reactor for further tests with the 1 kW_sol lab scale system. Variation of the outer reactor wall temperature profile, gas inlet temperature and reaction extent inlet leads to optimum conditions for certain massflows and pressures. It was found that the heat recovery is quite sensitive to the reaction extent inlet and rather insensitive to the inlet temperature of the synthesis gas. While the choice of an appropriate average outer reactor wall temperature is important, the influence of its slope is negligible. The optimum average outer reactor wall temperature was obtained for massflows between 0.1 and 1.3 g/s and pressures 10, 20 and 30 MPa and will be used for reference in future laboratory experiments. Further modelling will be carried out for the design of a new reactor, as the system will be scaled up to accept the full 15 kWsol power input from the ANU's 20 m² dish.