ABSTRACT
In an unsteady-state heat transfer process, the tempera-
ture at any location in the system changes with time. The
transfer of heat in this process is unsteady or transient.
Unsteady-state heat transfer is important because of the
large number of heating and cooling problems occurring
in biological systems. In food processing, perishable
foods are heated by immersion in steam baths or chilled
by immersion in cold water in order to increase their shelf
life.[1] Skin burns and frostbite are caused by accidental
heat and cold exposure. In hyperthermia and cryosur-
gery, tissues are heated or cooled rapidly to achieve
controlled destruction of the cancerous growth.[2] The
regular day to night changes in air temperature and
solar radiation cause bulk warming and cooling of
ground.[3] In fact, any time a heat transfer processing
operation is started, there will be a transient or unsteady-
state heat transfer period before steady-state heat transfer
conditions can be reached.
