ABSTRACT
Heat exchangers are routinely employed in numerous food
and agricultural applications to exchange heat between a
hot and a cold medium. Examples include plate-type heat
exchanger for pasteurizing milk and fruit juices, concentric
cylinders for recovery of heat from the waste stream, shell-
and tube-type heat exchanger for making ice and concen-
trating juices, and scraped surface heat exchanger for
heating or cooling viscous foods. Design calculations are
performed to develop or select a heat exchanger for a
new application or to rate the performance of an existing
heat exchanger. Performance rating helps to evaluate the
exit temperature of hot and cold fluids, estimate energy
consumption, and decide about the cleaning and replace-
ment schedules. Because of rising energy costs, the effi-
cient design and operation of heat exchangers are required
for reducing product costs, while remaining profitable.
Although the complete design of a heat exchanger involves
thermal, structural, and economic aspects, this entry focuses
only on thermal calculations. Thermal design may be based
upon either the logmean temperature difference (LMTD) or
the effectiveness-number of transfer units (NTU) method.
This entry focuses on the former method.
