Heat exchangers are used for heating, cooling, evaporation or condensation of media at different temperatures. The basic function is to transfer the thermal energy of a medium with a higher temperature level to a medium with a lower temperature level.
Convective heat transfer refers to the transfer of heat between a surface and a fluid. Convective heat transfer processes are associated with fluid flow movements, i.e. convection.
In recuperators, two media flow through simultaneously in a steady state. There is a partition between the media flows, which serves as a transfer surface. The heat is transferred indirectly from the hot medium to the partition and from the partition to the cold medium, without time lag.
Direct-contact heat exchangers bring two media with different temperatures into contact and mix them together. The heat and mass transfer takes place directly.
One special feature is the heat transfer by means of fluidised bed technology, which is investigated using a fluidised bed reactor.