Calcium carbonate fouling on double-pipe heat exchanger with different heat exchanging surfaces

An experimental setup of double pipe heat exchanger fouling test rig was built to investigate the mineral scale deposition on different heat exchanger pipe surfaces. Progressive fouling deposition on different material surfaces under the similar solution conditions were observed and analyzed. Measurable data on the progressive build-up of scale deposits, deposition rate, as well as the composition and crystal morphology of the deposits were studied after each experimental run by analyzing the deposited scale on the test pipes. In this research the artificial calcium carbonate deposit on different material surfaces is considered as it is one of the major constituents of the most scales found in heat exchanging equipment. Fouling on different smooth test pipes were investigated in the centrally located larger concentric pipe heat exchanger. Uniform flow condition near the pipe surface was maintained by constant flow rate throughout the system. The calcium carbonate deposition rates on five different metal surfaces (Stainless steel 316, brass, copper, aluminium and carbon steel) were investigated. The results illustrated an upward trend for fouling rate with time on the tested specimens. The deposition on the surfaces showed a linear growth with the enhancement of thermal conductivity of the metals. However, deposition on carbon steel metal surfaces did not follow the typical linear trend of thermal conductivity over deposition as its surface was altered by corrosion effects. In addition, temperature, velocity, and concentration effects on fouling deposition were investigated on the SS316 metal surface. It is noted that the fouling deposition increases with the increase of temperature and concentration due to enhanced deposition potential whereas reduces due to the increase of velocity which enhances shear stress. (C) 2017 Elsevier B.V. All rights reserved.