A plate heat-exchanger is a machine that transfers heat into or out of liquids using a pack of thin, corrugated stainless steel plates clamped in a frame. Product flows through alternate channels while heating or cooling medium flows through the others, the large surface area and turbulent flow giving extremely efficient heat transfer in a compact footprint. In food manufacture, plate heat-exchangers pasteurise milk and juices, cool wort in brewing, and heat sauces, with regeneration sections recovering heat from outgoing product to warm incoming product, slashing energy use. The plates separate for cleaning and inspection, and the hygienic design with food-grade gaskets prevents cross-contamination between product and service fluids. They are the thermal workhorses of liquid food processing, quiet, efficient, and ubiquitous in dairies worldwide.