Numerical Study Of Heat Exchanger Structure Based On Organic Rankine Cycle Of Waste Heat Recovery System

In this paper,the software of CFD has been applied to the research of high efficiency heat exchanger based on the organic Rankine cycle of waste heat recovery system.The organic working fluids (R113) occurred in three different heat transfer of liquid single-phase convection heat transfer,boiling heat transfer and gaseous single-phase convective heat transfer process in the heat exchanger. Firstly, this paper studied the influencev of the structure size changes of the corrugated tube on the flow and heat transfer performance of the single-phase liquid R113. Then, the flow and heat transfer performance of single-phase gaseous R113 in the corrugated tube was studied.And the flow and heat transfer performance of liquid refrigerant and gaseous refrigerant were compared under the same structure parameters of corrugated tube. Finally,the flow and heat transfer performance of boiling process of R113 was studied in corrugated tube. The specific research process as follows:(1)The physical model of the corrugated tube was introduced,and the mathematical model was established. The independent of grid was verified to ensure the influence of mesh quality to the accuracy of the calculation results can be ignored. The comprehensive heat transfer performance evaluation index η was introduced to measure the comprehensive heat transfer performance of corrugated tube. The flow and heat transfer performance of light pipe were simulated respectively by RSM model, RNG k-ε model and standard k-ε model. And finally found the results of RSM model is the most close to the empirical formula. So RSM model was selected in this paper.(2)The flow and heat transfer performance of the symmetry type corrugated tube were calculated in different distance of wave P, wave H, trough radius r.The comprehensive heat transfer performance, affected by the distance of wave P, wave H and deep trough radius r of corrugated tube,was analysied from the flow pattern, the pressure distribution, the turbulent kinetic energy, the turbulent dissipation,the velocity contour and etc. perspective. The analysis results show that the comprehensive performance of the corrugated tubes reached the highest when P=40mm,H=4mm and r=5mm.(3)The flow and heat transfer performance of asymmetric orrugated tubes were calculated when the big trough radius was located in the coming flow side and going flow side respectively. The resulte show that the heat transfer performance of the corrugated tube achieve the best when the big trough radius in the coming flow side. The flow and heat transfer characteristics of asymmetric corrugated tube were contrasted when the working medium medium was liquid and gaseous respectively. The results show that the asymmetric corrugated tube was more suitable for the enhancement of gaseous working fluid heat transfer in the same entrance velocity.(4)The internal factors of heat transfer enhancement of corrugated tube was analyzed from the view of flow and heat transfer characteristics. Meanwhile, the heat transfer performance of corrugated tube better than the light tube was explained combine with the field synergy principle.(5) The flow and heat transfer performance of boiling process in corrugated tube was studied and compared with the light pipe in this chapter. The results show that the heat transfer coefficient of corrugated tube was significantly higher than that of smooth tube in the process of boiling,At the same time, the boiling worse point of which was more retarded than the light tube and the more conducive to the boiling heat transfer,but the pressure drop increasesd.