Numerical study on the internal characteristics of single screw expanders used in organic Rankine cycle systems

Single screw expanders have been widely studied in middle-low temperature heat recovery power system of organic Rankine cycle, which is significant for the energy-conservation and environment-protection. However, internal irreversible loss including leakage, heat transfer and friction power loss has great influence on the performances of single screw expanders. Although some present researches of single screw expanders have been carried out, few can directly reflect the effect of internal irreversible loss on the performance of expanders. Therefore, it is necessary to research the internal characteristics of the single screw expanders. In this paper, a numerical study of a single screw expander was carried out to analyze its internal irreversible loss. Based on the theory of engineering thermodynamics and hydrodynamics, a thermodynamics working process mathematical model was presented to calculate the flow rate and efficiency of a single screw expander. A separation approach was proposed to solve the above coupling problem, which could be solved by classical fourth-order Runge-Kutta method through MATLAB language programming. Take the organic working fluid R123 for example, the numerical results were verified by experimental results. The numerical results of flow rate, volumetric and isentropic efficiency were in good agreement with the experimental results, and the average relative error are 4.9%, 4.4% and 0.3% at the rotation speed of 3000±10rpm under different intake pressure. Then three organic working fluids R123, R245fa and R134a were chose to simulate the characteristics of single screw expanders. Results show that the highest efficiency is R123, followed by R245fa and the last is R134a at the same rotational speed and intake conditions. The maximum volumetric and isentropic efficiency of R123 is 81.73% and 78.41%, respectively at the rotational speed of 3000rpm. The maximum volumetric and isentropic efficiency of R245fa is 80.63% and 69.67%, respectively at the rotational speed of 3000rpm. The maximum volumetric and isentropic efficiency of R134a is 78.04% and 54.50%, respectively at the rotational speed of 3000rpm

Study on the composition optimization method for improving the fluidity of cast Ti2_2AlNb alloy and its mechanism

In this paper, the effects of Al, Nb main elements, Fe, Mo, W, Co, B, Si and their contents on the fluidity of Ti-22Al-25Nb alloy were investigated. The composition that was beneficial to improve the fluidity was screened through the thermodynamic software calculating thermophysical parameters affecting the fluidity of Ti$_2$AlNb alloy, the numerical simulation test of its fluidity and the verification test of the fluidity of optimized alloys. Finally, the improvement mechanism of the alloy fluidity was discussed. Results showed that the appropriate reduction of Nb element was better than Al element for the improvement of fluidity. The addition of trace Fe, B and Si elements were beneficial to the improvement of fluidity, the improvement effect of B element was best, while the addition of trace Mo, W, Co were not conducive to the improvement of fluidity. The cessation mechanism of Ti$_2$AlNb alloy is the cessation mechanism of the alloy with a wide crystallization temperature range. The composition which was most beneficial to improve the fluidity was Ti-22Al-24Nb-0.1B. The main reasons for the improvement of the fluidity had two sides: on the one hand, the reduction of 1at% Nb and the addition of 0.1at% B not only increased the superheat and crystallization latent heat of the alloy, but also reduced the melt viscosity and thermal conductivity, thus improving the fluidity. On the other hand, the TiB phase refined the grains, the fine grains prevented the dendrite from growing into developed dendrite networks, inhibited the adverse effect of the increase in the width of the solidification zone on the fluidity, reduced the flow resistance of the molten metal, and further improved the fluidity of the alloy.Comment: 23 pages, 14 figures, research pape

Galectin-3 synergizes with CD47 to Suppress Phagocytosis and T cell immunity in Peritoneal Metastases of Gastric Adenocarcinoma

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Numerical and experimental evaluation of nasopharyngeal aerosol administration methods in children with adenoid hypertrophy

Article no 12390