Carbon dioxide (CO2) does not contribute to global warming as much as conventional refrigerants such as CFCs (chlorofluorocarbon) and FCs (fluorocarbon). It is hence gaining increasing usage as an environmentally-friendly refrigerant in modern heat pumps for air conditioning systems, refrigerators and other cooling applications despite its lower efficiency level.
However, due to its high vapor pressure, compressors for heat pumps using CO2 as the refrigerant have to be designed for up to 10 times higher pressures than classical compressors.
Compressors are often placed outdoors and are exposed to adverse environmental conditions such as humidity, pressure, vibration and various chemical influences. At the same time, compressors utilizing CO2 as a refrigerant operate at pressures and temperatures (up to 180ºC) much higher than conventional compressors.
With harsh environmental conditions acting both within and outside of the compressor, it is necessary that the housing is durably and hermetically sealed to ensure the continued safe and reliable performance of the compressor. This is why glass-to-metal sealing (GTMS) technology is the most promising solution for CO2 compressor seals, since GTMS consist only of very resistive materials.
Glass-to-metal compressor seals are electrical feedthroughs consisting of a metal base and glass elements which hermetically seal in metal leads to the base. Compressor sealsprovide an electrical conduction terminal and at the same time function as a hermetic “cover” for the compressor, protecting the internal components of the compressor from undesirable ambient influences, as well as preventing any leakage of the refrigerants from within. The strong hermetic seal is possible due to the compressive stress that the eyelet exerts upon the glass seal.