Heat Transfer Performance of Milk Pasteurization Plate Heat Exchangers Using MWCNT/Water Nanofluid

Increasing efficacy of plate heat exchanger (PHE) is a method of reducing energy consumption of milk pasteurization and sterilization in dairy industries. In order to enhance heat transfer capability of water as a hot stream in PHEs, multiwalled carbon nanotubes (MWCNT) were added to water. An experimental setup was designed and manufactured to measure heat transfer coefficient and Nusselt number (Nu) as two key parameters for convective heat transfer. This system had two individual loops for hot and cold fluids. The experimental results clearly indicated that heat transfer coefficient and Nu number of pure water increased by adding MWCNT with weight concentration of less than 1 wt%. With increasing weight concentration of the nanoparticles, heat transfer coefficient and Nu number increased. This augmentation was intensified at higher Peclet numbers which showed more effective presence of them at high flow rates of nanofluids. Moreover, at constant weight concentration, both heat transfer coefficient and Nu number increased. Augmentation of heat transfer capability resulted in more heat exchange with milk fluid in a short time; thus, before occurrence of fouling in plates of exchanger, pasteurization of milk and production of the products would be easier.