Simulation of Suitable Flow Conditions for Reducing Milk Fouling in the Dairy Industry

Abstract

This research proposed to study milk fouling in the flow channels of shell and tube heat exchangers used in the raw milk preheating process. The formation of fouling was classified through changes in the pressure drop across a 2-meter long milk fouling test unit. The effects of flow rates (4,000 l/h, 9,000 l/h and 12,000 l/h) were studied at a controlled hot water temperature (80°C) at a fixed experimental period of 2 hours. It was found that, at higher flow rate, the pressure drop was lower with thinner calculated scale layer thickness ranging from 1.42 cm to 0.53 cm and 0.17 cm, respectively. This might be because the protein ß-Lactoglobulin could not attach and spread out easily on the heat exchanger surface at high flow rates. As a result, the efficiency of the heat exchanger was increased, leading to lower energy consumption and longer production time. In addition, this research proposed to use a theoretical model to link between the calculated scale layer thickness and the reduction of heat transfer. This model was proved by comparing with the actual plant operation and seems to be suitable for economic evaluations regarding process assessment. It was found that by increasing the flow rate from 9,000 l/h to 12,000 l/h, the cleaning cycle could be delayed from every 8 h to every 17 h, leading to significant savings in the dairy industry.