Analysis of skim milk powder deposition on stainless steel tubes in cross-flow

• Skim milk powder deposition on round, elliptical and turned squared tubes is tested.
• Powder deposited almost exclusively on the various tubes' front faces.
• Elliptical tube is shown to be naturally low fouling due to its shape.
• The critical impact angle is a function of particle stickiness and air velocity.

Particulate fouling on the gas side of heat recovery equipment is a common industrial problem. The aim of this study is to characterize the deposition of skim milk powder on a single bare tube in cross-flow. A custom built rig is applied to simulate exhaust air conditions that is experienced in an exhaust exchanger. For a constant airflow rate, increasing particle stickiness resulted in greater deposition coverage around the front of the round and elliptical tubes peaking in the middle, whereas the turned square tube tended to be either clear or covered. Results show that the skim milk powder particle impact angle on the tube, as opposed to the wall shear stress, is an important determinant for deposition. During each test and at the conclusion of each test, which was when fouling reached an asymptote, the amount of deposition coverage and build-up on the tube varied depending on the tube shape, particle stickiness, and air velocity.