Numerical investigation on pre-heating of coal water slurry in shell-and-tube heat exchangers with fold helical baffles

Abstract

Pre-heating process of coal water slurry (CWS) in Integrated Gasification Combined Cycle (IGCC) systems is beneficial to enhance the energy efficiency. In this paper, shell-and-tube heat exchangers with fold helical baffles (STHXsFHB) were firstly used as pre-heating exchanger. Using numerical simulation method, the flow and heat transfer performance of STHXsFHB with different helical angles and overlapped degrees was investigated. CWS with concentration of 62 wt% was shell-side fluid, which is characterized as non-Newtonian fluid and simulated with Bingham model. The numerical results show the temperature of CWS rises obviously, both Nusselt number and friction coefficient increase with helical angle at same shell-side mean velocity, Nu·f−1/3 decreases when helical angle increases. Nusselt number and friction coefficient have a negative correlation with overlapped degree, and Nu·f−1/3 with 50% overlapped degree is 13.8–33.1% and 3.9–8.8% higher than that with 1% and 30% overlapped degree, respectively. The variation of Nusselt number and friction coefficient versus helical angle and overlapped degree of CWS differs from thermal-hydraulic performance of Newtonian fluid in STHXsFHB. It is also found that the comprehensive performance of STHXsFHB is superior to shell-and-tube heat exchangers with segmental baffles.