| 摘要 |
<p>Apparatus for refrigerating and heating comprising a source of liquid nitrogen arranged to deliver nitrogen selectively through coils of an evaporator or through heating apparatus and then through coils of the evaporator such that nitrogen can be employed for either cooling or heating a cargo compartment. Nitrogen gas exhausted from coils of the evaporator is released to ambient atmosphere outside of the compartment. Temperature sensors are positioned for sensing the temperature of nitrogen gas exhausted to atmosphere and to sense the temperature of air which has been drawn across the evaporator coils. Control apparatus initiates a defrost cycle to cause heated nitrogen vapor to be passed through evaporator coils for defrosting the coils when ice accumulates thereon in sufficient quantity to insulate the coils causing a predetermined temperature differential between the exhaust gas and air drawn across the evaporator coils.</p> |
