Evaluating the effectiveness of cryogenic heat exchangers
is very important. The effectiveness factor is calculated
by the gas flow temperatures at tube inlet and outlet. The
inlet and outlet temperatures of fluids may be different
from values measured by sensors. This event takes place
when the effect of tube wall longitudinal heat conduction
is neglected and the sensors are placed in inappropriate
axial positions. Therefore, the effectiveness of cryogenic
heat exchangers may be evaluated without considering
errors associated with axial position of sensors and leads
to obtain incorrect values. Although longitudinal heat conduction
has a great importance in the cryogenic engineering,
but almost all investigations have been focused on the
cryogenic heat exchangers.