Thin-Film Evaporation Modelling for the Concentration of Tamarind Juice in a Triple-Effect Evaporator

Tamarind (Tamarindus indica) juice concentrate has applications as a food flavouring, beverage ingredient, and traditional condiment across northern Nigeria, where tamarind trees are extensively cultivated. Efficient concentration by multi-effect evaporation requires accurate modelling of heat and mass transfer in thin-film evaporators to optimise energy consumption and product quality. This study develops a mathematical model for the concentration of tamarind juice in a simulated triple-effect evaporator, using thermophysical property data measured for tamarind juice at solid contents from 12 to 65 degrees Brix. The model incorporates heat transfer coefficients as functions of viscosity, temperature, and flow regime, and accounts for boiling point elevation as a function of concentration. The model was validated using pilot-scale single-effect evaporation data collected at the National Research Institute for Chemical Technology in Zaria, North West Nigeria. Parameters including steam economy, overall heat transfer coefficient, and evaporation rate as a function of temperature profile and juice concentration were computed and validated against experimental results with errors below 7 percent. The optimised triple-effect design achieved a steam economy of 2.6 kg water evaporated per kg of steam, representing a 62 percent energy saving over single-effect concentration. Colour degradation and vitamin C retention were modelled as quality indicators. The study contributes to the food concentration engineering literature for tropical fruit juices and provides a design basis for tamarind concentrate processors. Keywords: evaporation, tamarind juice, triple-effect evaporator, mathematical model, concentration