DEVELOPMENT OF TUBULAR Ni WICK USED IN LHP FOR SPACE APPLICATIONS

Present research is focused on porous tubular wick development, which is considered as the heart of the Loop heat pipes (LHP) specifically used for space applications, such as satellites and space craft's. Basic purpose of a wick is to generate capillary pumping pressure required to transport a working fluid along a two-phase heat transfer loop. Wicking structures are generally made of wire meshes or sintered metal powders. Present work establishes Metal Injection Moulding (MIM) as a potential route for the manufacturing of tubular wicks in the near-net shape form, discarding any need of further machining for creating vapour removal channels/grooves on the outer surface. Nickel powder along with polypropylene (PP) powder and thermoplastic binder consisting of paraffin wax (PW) and low density polyethylene (LDPE) are used to produce feedstock for injection moulding. Green compact of tubular wicks prepared by injection moulding is then debound and sintered to get the final porous structure. Further characterization of the tubular wicks sintered at 900 0 C for 60 minutes reveals porosity level of 55 vol%, avg. capillary pore diameter of 2.6µm, permeability of 1.94×10 -12 m 2 and thermal conductivity of 9.37 W/mK. SEM observation of wick samples shows well connected micro porous