The heat capacity rate is heat transfer terminology used in thermodynamics and different forms of engineering denoting the quantity of heat a flowing fluid of a certain mass flow rate is able to absorb or release per unit temperature change per unit time. It is typically denoted as C, listed from empirical data experimentally determined in various reference works, and is typically stated as a comparison between a hot and a cold fluid, C h and C c either graphically, or as a linearized equation. It is an important quantity in heat exchanger technology common to either heating or cooling systems and needs, and the solution of many real world problems such as the design of disparate items as different as a microprocessor and an internal combustion engine.