In electronic systems, a heat sink is a heat exchanger that cools a device by dissipating heat into the surrounding medium. A heat sink is designed to maximize its surface area in contact with the cooling medium surrounding it, such as the air. Air velocity, choice of material, protrusion design, and surface treatment are factors that affect the performance of a heat sink. The following model shows a protrusion design using an array of round pins cooled by forced convection (fan).