Heat Transfer in Moving Bed Heat Exchangers for High Temperature Thermal Energy Storage

Heat transfer inside a moving bed heat exchanger (MBHX) is closely investigated. For this purpose a novel simulation model has been developed whose results are compared to experimental data and theoretical predictions ("penetration theory"). While the penetration theory clearly underestimates heat transfer inside the MBHX, the simulation model shows good agreement with the experimental data, especially at low flow speeds. This result indicates that areas which are supposed to have negligible contribution to heat transfer have in fact to be taken into account and that a precise modelling of the flow field is necessary. Furthermore, it is found that the range of operating velocities of the MBHX lie in an intermediate flow regime where neither the thermal contact resistance from the wall to the first layer of particles nor the thermal penetration resistance of the bulk can be neglected.