| Summary: | A substantial raise in recuperator effectiveness has been established in the past by
improving the fabricating and joining configurations regarding the manufacturing of
compact recuperators. Further advancement of state-of-the-art recuperators requires
providing for increased temperatures and pressures. 1bis can only be achieved by
incorporating high temperature materials into the recuperator design. Although many
high temperature materials have been identified in past research, less of these can be
utilized in new concepts due to difficulties regarding fabricating and joining. However
recently, in an independent study, a tungsten-copper alloy was identified through detailed
material selection methods as a suitable material for high temperature applications. The
validity of tungsten-copper regarding fabricating and joining, to establish a leak tight
structure still needs to be demonstrated.
The aim of the study is to carry out a comprehensive review of existing recuperator
technologies and design methodologies as well as to investigate the manufacturability of
tungsten-copper for use in a recuperator design of limited size. More specifically, the
objectives entail the following: (1) The comprehensive review of existing recuperator
technologies and recuperator design methodologies, (2) The design and fabrication of a
recuperator of limited size using tungsten-copper as a heat transfer material and (3) The
determination of the feasibility of fabrication of the design and the applicability of the
selected W -eu alloy in the design.
The fabrication technique that is presented in the design entailed the use of 2.Irm tungsten
carbide drill bits to machine the correct recuperator profile, while the recuperator unit
was joined by utilizing a mechanical fastening system. Although diffusion bonding was
initially identified as the ideal joining technique for the recuperator of this research, restrictions and limitations relating to the use of diffusion bonding has lead to the
identification of a fastening system as the technique used. Evaluation of the fabricated
recuperator revealed that several factors were outside the initially specified values, inter
alia the flatness tolerance of recuperator plate geometries and machined slots precision.
These factors contributed to a leaJdng recuperator structure when tested. The most likely
contributing factors for the latter relate to non-conforming tolerances achieved in the
fabricated design, residual stresses induced by the machining process as well as design
issues relating to the recuperator plate geometries.
The design and fabrication of a recuperator of limited size using tungsten-copper as a
heat transfer material, requires re-evaluation. Similar work will ensure a design of a high
quality when provision is made for advanced surface fmishing of machined parts (notably
the recuperator plate geometries), slight modifications to the design as well as stress
relieving of machined components for the purpose of eliminating any residual stresses
thatJnight be present. === Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2009.
|
|---|
