What is the difference between Hermetic and SemiHermetic compressor ?
Semi-hermetic – compressor-motor assembly contained in a casting with no penetration by a rotating shaft and with gasketed cover plates for access to key parts such as valves and connecting rods. Hermetic – compressor-motor assembly contained in a welded steel case, typically used in household refrigerators, residential air conditioners, smaller commercial air conditioning and refrigeration units. For small hermetic compressors (household) f_Q can reach values as high as 75%. For semihermetic compressors the value of f_Q varies between 10 and 25 % and for large compressors between 5 and 15 %. For screw compressors the value can be expected to be higher because of oil cooling. Isentropic efficiency is used to express the energy efficiency of a compressor by comparing its energy consumption with the energy consumption necessary for an ideal (reversible and adiabatic) compression process. Isentropic efficiency can have values between 0 and 1. Typical values are 0.4 to 0.5 for small hermet
