The deposition of ash particles to the surfaces of the tubes of heat exchangers in lignite utility boilers is a major problem during the operation of the utility resulting in significant reduction in efficiency and increased operational and maintenance costs as well as an adverse environmental effect. The purpose of the proposed research project is to increase heat transfer efficiency while simultaneously minimising fouling of the tube surfaces. The proposed techniques are the use of flow pulsation in the tube bundle and the use of asymmetric tube arrangements and/or non-circular tubes in these. The research will be performed numerically and experimentally with constant guidance and consulting from an industrial partner.
Numerical Approach: Direct numerical simulation, large eddy simulation and advanced turbulence modelling for the unsteady turbulent flow in the tube bundles. Direct modelling of particle trajectories and deposit formation in time and calculation of the effect of deposit formation on the flow field, heat transfer eff1ciency and deposition rate. The numerical simulations will focus on the effect of flow pulsation on heat transfer augmentation and fouling minimisation while asymmetric tube arrangements and non-circular tubes will also be studied.
Experimental Approach: The tube bundle arrangements under investigation will be constructed at laboratory scale and flow, temperature and mass transfer will be measured. The experimental techniques to be used are laser Doppler anemometry, flow visualisation, liquid crystal thermography, spectrofluorimeter and laser particle counting Industrial Guidance: The experience of the industrial partner will provide constant input and guidance and the operational monitoring of the utility will provide insight as to the industrial applicability of the results.
Final Results: The above will lead to an improved knowledge regarding the effects of flow pulsation, asymmetric arrangements and non-circular tubes on heat transfer augmentation and fouling minimisation in heat exchanger tube bundles. A reliable numerical methodology will also be available for the design phase of heat exchanger tube bundles taking into account the requirement of minimum fouling ofthe tube surfaces
Funding SchemeCSC - Cost-sharing contracts
WC2R 2LS London