A plate heat exchanger consists of numerous thin embossed metal plates through which two media flow alternately. The corrugated surface generates turbulent flow, significantly improving heat transfer efficiency. In building services engineering, it is commonly used as a heat interface unit between district heating networks and building heating circuits, or as an evaporator and condenser in refrigeration systems. Compared to shell-and-tube exchangers, it offers high thermal performance in a compact form. Depending on design, plates may be brazed, gasketed, or welded. Regular cleaning prevents fouling and maintains efficiency.