An annular control valve was developed for the extrusion of wood slurries and polymers. The objective was to determine the optimal valve geometry: (1) to provide a linear pressure drop across the valve as a function of valve opening and (2) to eliminate the problem of valve plugging caused by the high solid content of the wood slurries. The approach was to model the non-Newtonian flow in a plasticating single-screw extruder. A finite-difference scheme was developed to model the flow through annular surfaces. The two flow equations were solved simultaneously and a parametric study was performed to determine the optimal valve geometry. The valve operability was evaluated for the extrusion of various mixtures of low-density polyethylene, sawdust, wood flour, and vacuum bottom. The experimental results were in good agreement with the model. In general, a linear valve characteristic was observed and the problem of valve plugging was not evident.

published_or_final_version / Architecture / Master / Master of Landscape Architecture