= Cryogenics
{wiki}
<Cryogenics> studies the production and use of very low <temperatures>. Its experimental challenge is a balance of rates: a <refrigerator> must remove <energy> from a cold region faster than unwanted <heat transfer> supplies it. A low <temperature> reading alone does not establish a useful cooling capacity. A maintained cold <liquid> bath is especially valuable because <latent heat> allows it to absorb <heat> while its <phase fraction> changes at nearly fixed <temperature> and <pressure>.
<Helium liquefaction> illustrates why staged cooling and recovery of a returning stream's cooling capacity matter. A <counterflow heat exchanger> transfers <heat> from the incoming stream to the colder returning stream without mixing them. This reduces the incoming <specific enthalpy> before expansion. The <heat exchanger> recovers cooling already produced; the surrounding <refrigerator> still requires input <work> and rejection of <heat> to a warmer environment.
Back to article page
