Two-phase flow patterns and condensation on wetted surfaces for innovative self-cleaning heat exchangers: experiments and numerics

Other conference contribution, 2018

Fouling is a common and pervasive problem in industrial processes that involve the cooling of hydrocarbon-rich gas mixtures and and it is considered responsible for 1%÷2.5% of the global anthropogenic emissions of CO2. One of the major drawbacks related to fouling is that it impedes heat recovery and thereby it considerably limits the efficiency of many industrial processes. We experimentally and numerically have investigated whether self-cleaning surfaces of heat exchangers represent a possible solution to overcome this technological bottleneck.

Hydrophilically and hydrophobically treated corrugated plates of heat exchangers have been experimentally tested in a 2 MW th research-gasifier and their capabilities to resist fouling have been evaluated. Results revealed that hydrophobically treated surfaces exhibit good anti-fouling and self-cleaning properties. By means of numerical Lattice-Boltzmann-based simulations we then unveiled the self-cleaning phenomenon induced by the wetted surfaces: with a similar mechanism to lotus-leaves, small and motile condensed water droplets are able to collect and remove impurities present in the gas and prevent surfaces fouling. Condensation, two-phase flows patterns formation and droplets coalescence all contribute to promote or weaken the self-cleaning effects. Therefore, numerical simulations have been finally used to identify the main mass and heat transport mechanisms that affect self-cleaning and the optimal operative conditions of the heat exchangers.