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The two most commonly used types of compressed air drying equipment are cryogenic and adsorption types. When discussing the efficiency of dryers, analysis is usually carried out from the perspectives of pressure drop and gas consumption; however, neither sellers nor manufacturers often mention the energy efficiency of these dryers. The calculation methods and standards for the energy efficiency of compressed air dryers (refrigeration type and adsorption type) in this article are based on the Shanghai local standard DB31/T 1143-2019 \"Technical Specifications for Online Monitoring of Energy Efficiency in Air Compressor Systems\". 01 Calculation of the energy efficiency of freeze-dryers The energy efficiency (η) of a freeze-dryer is calculated using the following formula: https://pic.ouryao.com/data/attachment/forum/202012/10/152912tn00xnbp9zpp9u0n.jpg.thumb.jpg Where: η — Energy efficiency of the freeze-dryer ； Mout — output mass flow rate (cumulative value), in kilograms (kg); Hin — specific enthalpy of the incoming airflow, in kJ/kg ； Hout — specific enthalpy of the exhaust gas flow, in kJ/kg ； Ee — energy consumption, in kilowatt-hours (kWh). Parameter explanation: Mass flow rate – refers to the mass of fluid that passes through the effective cross-section of a closed pipe or an open channel per unit of time. Specific enthalpy refers to the total heat contained in the air, usually expressed per unit mass of dry air. In engineering, it refers to the sum of the enthalpy of one kilogram of dry air and the enthalpy of the water vapor corresponding to it. We can determine whether air gains or loses heat based on the change in specific enthalpy of a certain mass of air during the processing. 02 Calculation of the energy efficiency of adsorption dryers: The energy efficiency (η) of refrigeration dryers is calculated using the following formula: https://pic.ouryao.com/data/attachment/forum/202012/10/152945t2w25znh4vnh4d2h.jpg.thumb.jpg Where: η — Energy efficiency of adsorption dryers ； Mout — output mass flow rate (cumulative value), in kilograms (kg); Hin — specific enthalpy of the incoming air flow, in kJ/kg ； Hout — specific enthalpy of the exhaust gas flow, in kJ/kg ； Ee — Energy consumption, in kilowatt-hours (kWh) ； Vin — input volumetric flow rate (cumulative value), in standard cubic meters (Nm3) ； Vout — Output volumetric flow rate (cumulative value), in standard cubic meters (Nm3) ； Pa — standard atmospheric pressure, in kilopascals (kPa) ； Pin — Input the absolute air pressure, in kilopascals (kPa). Volumetric flow rate – The gas volumetric flow rate refers to the volume of gas that passes through a pipeline per unit of time. The volume of a gas can be divided into the volume under operating conditions and the volume under standard conditions. 03 is the benchmark value for the energy efficiency of refrigeration-type dryers, while 04 is the benchmark value for the energy efficiency of adsorption-type dryers