Design and Perfomance Evaluation of a Short Recycled Concentric Tube Heat Exchanger for Raw Milk Pastuerization

Abstract

The recycled concentric tube heat exchanger was designed with the principle of recycled heat transfer technique over a short concentric tube, which successfully constrained the heat transfer area of the conventionally long arranged or floating tubes to a reduced size in terms of cycles/minute. Validation was then carried out by experiment to ascertain its viability and the new concept was named cycle pasteurization following its success. The total head loss of both water and milk side of the heat exchanger were so negligible at 0.00002. The rate of heat, area, length, no of cycles, log mean temperature difference and effectiveness of the heat transfer were analyzed with respect to the pasteurizer and has exhibited very good characteristics which have kept the milk composition and it organoleptic properties safe for consumption. The most critical of the thermodynamic properties were coefficient of heat transfer of 1.411 and 4.2319 W/m2 k and fouling factor of 0.7087 and 0.2363m2 ℃/W at the beginning and end of tube heat transfer respectively, which are within the limits of pasteurization theory to keep the milk nutritive values safe for consumption. This valuable equipment with 2 litres capacity for home use and the concept of cycle pasteurization has effectiveness of 0.59 representing 98.3% efficiency of the system. Indeed, the pasteurizer will complement the existing conventional batch and flash pasteurization methods where arrangement of plates and floating long concentric pipes are used which is characterized with the challenge of micro-scale pasteurization.