HEAT EXCHANGERS
Heat Transfer
HEAT EXCHANGERS
Heat exchangers are devices that are used to transfer thermal energy
from one fluid to another without mixing the two fluids.
EO 1.11
DESCRIBE the difference in the temperature profiles
for counter-flow and parallel flow heat exchangers.
EO 1.12
DESCRIBE the differences between regenerative and
non-regenerative heat exchangers.
EO 1.13
Given the temperature changes across a heat exchanger,
CALCULATE the log mean temperature difference for
the heat exchanger.
EO 1.14
Given the formulas for calculating the conduction and
convection heat transfer coefficients, CALCULATE the
overall heat transfer coefficient of a system.
Heat Exchangers
The transfer of thermal energy between fluids is one of the most important and frequently used
processes in engineering. The transfer of heat is usually accomplished by means of a device
known as a heat exchanger. Common applications of heat exchangers in the nuclear field include
boilers, fan coolers, cooling water heat exchangers, and condensers.
The basic design of a heat exchanger normally has two fluids of different temperatures separated
by some conducting medium. The most common design has one fluid flowing through metal
tubes and the other fluid flowing around the tubes. On either side of the tube, heat is transferred
by convection. Heat is transferred through the tube wall by conduction.
Heat exchangers may be divided into several categories or classifications. In the most commonly
used type of heat exchanger, two fluids of different temperature flow in spaces separated by a
tube wall. They transfer heat by convection and by conduction through the wall. This type is
referred to as an "ordinary heat exchanger," as compared to the other two types classified as
"regenerators" and "cooling towers."
An ordinary heat exchanger is single-phase or two-phase. In a single-phase heat exchanger, both
of the fluids (cooled and heated) remain in their initial gaseous or liquid states. In two-phase
exchangers, either of the fluids may change its phase during the heat exchange process. The
steam generator and main condenser of nuclear facilities are of the two-phase, ordinary heat
exchanger classification.
HT-02
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