Ricor manufactures Stirling type rotary and linear, integral and split configurations for miniature cryogenic coolers - serving a wide range of military and commercial applications, mainly thermal imagers or FLIRs.
The Theory Behind the Stirling Engine
The Stirling engine, a particular case of the Carnot heat engine, operates by cyclic compression and expansion of air (or other gases) and the working fluid, at different temperature levels, resulting in the net conversion of heat energy to mechanical work.
The Stirling Engine Patent
In 1816 The Heat Economizer (also known as The Regenerator) was patented by a Scottish reverend, Dr. Robert Stirling (1790-1878). It was a motive power engine which worked on low fuel consumption in contrast to the then current technology of steam. In addition, the engine was safer than steam engines which were susceptible to explosions in their early days.
The patent described the process of what became known as the Stirling Engine Cycle. The external combustion engine was characterized by a power piston, a displacer to move the enclosed air between the hot and cold ends and a regenerator, placed between the hot and cold ends of the displacer cylinder. The end result was enhanced operational efficiency of the engine, leading to a reduction in the amount of energy needed to heat up the working air.
The Stirling refrigerator’s most basic schematics consist of the piston and “Expander” (sometimes “Displacer”). According to the Ideal Gas Law, during the repeated gas expansions the heat is repeatedly absorbed by the expanded gas from its thermally isolated surroundings, making it colder. Analogously, during the repeated gas compressions the heat is repeatedly ejected from the compressed gas through its surroundings into the atmosphere. Proper timing of the compression and expansion phases allows for lifting the heat at the Cold side, transferring it through the Regenerator to the hot side and ejecting it into the atmosphere. For almost 200 years, the basic concept of the Stirling engine has remained unchanged, while advances in regenerator materials, clearance seal technology and flexure bearing designs have made the Stirling engine a highly efficient, reliable and robust machine.
Today, Stirling Engine technology has multiple Cryogenic applications including: IR – Infra Red imagers, vacuum applications, H2O Vapor Cryotraps, Cryopumps, HTSC (High Temperature Super Conductor) applications, RF-filters – Wireless communication, FCL (Fault Current Limiters) – Electricity, SQUID’s - Superconducting QUantum Interference Device, Motors, Generators, Transformers, Magnetic Bearings, Magnetic Separators, Air liquefaction, Cryosurgery, ZBO - zero boil-off storages, and MRI – magnetic resonance imaging.