Numerical and experimental studies of heat transfer in particle-laden gas flows through a vertical riser

This paper presents numerical and experimental studies of gas–solid flow with heat transfer during pneumatic transport. The experimental work investigates the flow with two different cases of inlet thermal conditions namely; hot gas with cold solid particles, while the second case is cold gas with hot particles. Crushed limestone particles with different sizes are used in the experimental study. The Eulerian–Lagrangian approach is utilized to simulate the process under consideration. In the present study, the SIMPLE algorithm is extended to compressible flow. The model takes into account the effects of particle–particle and particle wall collisions, gas phase turbulence modulation and turbulence dispersion (i.e., four-way coupling). The effect of wall roughness is simulated using the virtual-wall model. The model is validated with available published experimental data for high speed gas–solid flow and a good agreement is obtained. Also, the model predictions are found to be in a good agreement with the present experimental measurements. The present results show that pressure drop increases in dilute phase and decreases in dense phase pneumatic conveying when hot particles are introduced in cold gas flow, and an opposite effect is obtained when cold particles is introduced in a hot gas stream. In addition, it is noticed that the equilibrium temperature and the distance required to reach equilibrium are greatly affected by the flow conditions. Furthermore, the present results show that gas–solid flows with heat transfer can be accurately modeled using incompressible ideal gas law for low conveying speed, while for high conveying speed; the full compressible model should be used.