Erwin Theuns

Heat recovery system for dishwashers

In this paper a heat recovery system for a dishwasher is proposed and analysed. The idea is to use the heat coming from the wastewater of the dishwasher to heat the fresh water entering the dishwasher. The potential of energy recovery is studied technically and economically. A prototype was built and experiments on it are discussed. Results of the measurements show the thermal potential. They are also used to validate a design calculation procedure. With this an improved design is proposed. Recovery of the heat in the wastewater is proven to be economically beneficial.

A moving grid model for the pyrolysis of charring materials

This paper describes a one dimensional moving grid model for the pyrolysis of charring materials. In the model, the solid is divided by a pyrolysis front into a char and a virgin layer. Only when the virgin material reaches a critical temperature it starts to pyrolyse. The progress of the front determines the release of combustible volatiles by the surface. The volatiles, which are produced at the pyrolysis front, flow immediately out of the solid. Heat exchange between those volatiles and the char layer is taken into account. Since the model is used here as a stand‐alone model, the external heat flux that heats up the solid, is assumed to be known. In the future, this model will be coupled with a CFD code in order to simulate fire spread. The char and virgin grid move along with the pyrolysis front. Calculations are done on uniform and on non‐uniform grids for the virgin layer. In the char layer only a uniform grid is used. Calculations done with a non‐uniform grid are about 3 times faster than with a uniform gird. The moving grid model is compared with a faster but approximate integral model for several cases. For sudden changes in the boundary conditions, the approximate integral model gives significant errors.