31-10-2012, 04:01 PM
ENVIRONMENT FRIENDLY REFRIGERATED CONTAINERS
ABSTRACT
Cryogenics is that branch of physics which deals with the production of very low temperatures and their effect on matter, a formulation which addresses both aspects of attaining low temperatures which do not naturally occur on Earth, and of using them for the study of nature or the human industry. In a more operational way, it is also defined as the science and technology of temperatures below 120 Kelvin.
A cryogenic refrigeration system is used where the journey time is short and it is total loss refrigeration, in which frozen carbon dioxide ice (or sometimes liquid nitrogen) is used for cooling. The cryogenically frozen gas slowly evaporates, and thus cools the container and is vented from it. The container is cooled for as long as there is frozen gas available in the system. These have been used in railcars for many years, providing up to 17 days temperature regulation. Whilst refrigerated containers are not common for air transport, total loss dry ice systems are usually used. These containers have a chamber which is loaded with solid carbon dioxide and the temperature is regulated by a thermostatically controlled electric fan, and the air freight versions are intended to maintain temperature for up to around 100 hours.