Fouling of heat transfer surfaces

There are many parameters affecting the fouling deposit on the heat transfer surface. These parameters include flow velocity, surface temperature, fluid bulk temperature, fluid characteristics, surface material and structure. The flow velocity is one of the most important parameters affecting the fouling rate and there is a rarity in literature covering this effect. Therefore, the purpose of the present work is to study the effect of flow velocity on the fouling rate. To carry out this study, an experimental test rig has been designed and constructed. The experimental loop has three 97% Cu-Ni test tubes of 2400 mm length and 16 mm inner diameter. Water with a solid particle concentration of 19 m/lit is used as a test fluid. The test fluid flows through the tubes which are heated by means of steam. The cooling water is arranged in a closed loop to keep constant solid particle concentration. The experiments are carried out under constant surface temperature by using the steam as a heating medium. These experiments have been carried out under different flow velocities (from 0.2 to 1.42 m/s). The experimental loop is a differential one and the runs have been operated for long time (about 200 hrs.) to attain the asymptotic fouling resistance. The obtained experimental results are analyzed, and the effect of flow velocity on the fouling rate and the asymptotic fouling resistance is plotted. From the discussion of these results, it is concluded that; both the fouling resistance and the asymptotic fouling resistance decrease with increasing the flow velocity. The delay time is very small and is seen to approach zero in all the experimental work. The saw tooth effect has been obtained in all runs. Results have shown also essential.10 tabs.,4-8 figs.,71 refs