Liquid-liquid heat exchangers are critical for precise temperature control and efficient heat transfer in demanding applications. They support coolant-to-oil heat transfer, hydraulic fluid cooling, fuel temperature regulation, and process fluid heating. Common types include shell and tube heat exchangers, plate heat exchangers, spiral heat exchangers, and brazed plate heat exchangers. Typical fluid pairings include water-to-glycol for cooling, oil-to-water for lubrication management, and fuel-to-coolant for temperature stabilization.