High temperature expanders have always been employed in industrial waste heat recovery systems, where twin-screw expanders were frequently adopted.However, the significant thermal deformation of rotors contributes to much technical difficulty on the designation and manufacturing of high temperature twin-screw expanders. The profile should be optimized with consideration of its thermal deformation in high temperature working conditions. In this article, a novel method for twin-screw expander profile optimization is developed.The thermal deformation of rotors is considered with meshing pair rules and interlobe clearance presetting. Theoretical analysis on interlobe clearance is made any steam inlet temperature from 20 C to 400 C, while experimental facility was built to figure out its reliability at high temperature. The optimized profile proved the effectiveness of this method. The clearance decreases significantly, decreasing from 1.28 mm at the working temperature of 20 C to 0.16 mm at 400 C. The testing results illustrated that the significant thermal deformation of rotors causes much interlobe abrasion once the operating temperature reached 400 C. With clearance of 0.1 mm and the radius correction angle of 0.0758 , the screw expander was proved to be reliably working at 400 C.
For the novel frost-free air source heat pump system (FASHP), the compressor waste heat is used to assist desorption for the desiccant on the surface of the desiccant coated heat exchange (DCHE). It can promote the desorption efficiency of the DCHE in the FASHP and reduce the energy loss, which means the improvement of the stability and performance. In this paper, a DCHE model is established, and its accuracy is verified through experimental data. The model is then used to analyze the effect of working conditions and structural parameters on the adsorption rate, desorption rate, heat exchange and proportion of latent heat in the adsorption and desorption processes. The results show that the latent heat ratio is higher, the heat exchange of the DCHE is lower and the system performance is better when the temperature of the analytical circulating air increases and the velocity decreases to 25 °C/0.5 m/s. In addition, the performance is greatly affected by the fin length and width. With the increase of parameters, the heat exchange and proportion of latent heat can be increased to 115.9 J and 69.0%.
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