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The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. [1] [2] Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs. The COP is used in thermodynamics.
The above efficiency formulas are based on simple idealized mathematical models of engines, with no friction and working fluids that obey simple thermodynamic rules called the ideal gas law. Real engines have many departures from ideal behavior that waste energy, reducing actual efficiencies below the theoretical values given above. Examples are:
In thermal engineering, exergy efficiency (also known as the second-law efficiency or rational efficiency) computes the effectiveness of a system relative to its performance in reversible conditions. It is defined as the ratio of the thermal efficiency of an actual system compared to an idealized or reversible version of the system for heat ...
In heating mode, the coefficient of performance is the ratio of heat provided to the energy used by the unit. An ideal resistance heater converting 100% of its input electricity to output heat would have COP = 1, equivalent to a 3.4 EER.
In the case of materials, it is often expressed in terms of R-value per metre. R-values are additive for layers of materials, and the higher the R-value the better the performance. The U-factor or U-value (in W/(m 2 ⋅K)) is the overall heat transfer coefficient and can be found by taking the inverse of the R-value. It is a property that ...
Heating seasonal performance factor (HSPF) is a term used in the heating and cooling industry. HSPF is specifically used to measure the efficiency of air source heat pumps . HSPF is defined as the ratio of heat output (measured in BTUs ) over the heating season to electricity used (measured in watt-hours ).
For example, an ideal fuel cell operating at a temperature of 25 °C having gaseous hydrogen and gaseous oxygen as inputs and liquid water as the output could produce a theoretical maximum amount of electrical energy of 237.129 kJ (0.06587 kWh) per gram mol (18.0154 gram) of water produced and would require 48.701 kJ (0.01353 kWh) per gram mol ...
Lift and drag are the two components of the total aerodynamic force acting on an aerofoil or aircraft.. In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air.