What is Carnot efficiency?
Heat and work are two forms of energy. The first law of thermodynamics states that energy must be conserved: energy can neither be created nor destroyed. Work can readily be converted to heat. The second law thermodynamics sets a limit on the fraction of a given quantity of heat energy that can be converted to work. The production of work from heat requires heat flow from a hot source to a cold sink. Carnot efficiency is the maximum efficiency that can be achieved when heat is transferred from the hot source to the cold sink. Carnot efficiency n is: n = 1- TC/TH, where TH is temperature of the hot source and TC is the temperature of the cold source, and where temperatures are in [K] degrees Kelvin. The portion of the heat that is not converted to work is delivered as low temperature waste heat at the cold sink. Carnot devised an ideal cycle where the heat is received and given up at two definite temperatures. The efficiency of other ideal cycles such as the gas turbine cycle is close t
Carnot efficiency is a term that describes the maximum efficiency that can be reached by a heat engine in converting heat to work. The Carnot efficiency has a simple formula that has been around since the early part of the 19th Century, when young French engineer Sadi Carnot proposed it based on his study of steam engines. (Strangely enough, he put forth his formula when the very nature of heat as molecular motion was still being debated!) The formula is: Efficiency = (Temperaturehigh – Temperaturelow)/Temperaturehigh. Here, the temperatures must be given in the absolute temperature scale — Kelvin degrees, which begins at “absolute zero,” which is some -273°C below 0 °C (the freezing point of water). So, at a typical ambient temperature of 20 °C (approximately 293 K), the Carnot efficiency of an engine operating between that temperature and 273 K (0°C) is (293-273)/293 = 6.8%. For a much more elevated temperature process with a high temperature of say 1,000°C, dumping its waste heat to
