PERFORMANCE OF PLATE HEAT EXCHANGERS WITH ODD NUMBER OF CHANNELS

'Ilhis paper deals with a numerical analysis of the heat transfer behavior in
gasketed plate heat exchangers with an odd number of parallel arranged
channels (case of half-unsymmetrical channels). The calculations are carried
out under varying the number of transfer units, the heat capacity rate ratios
and the number of channels for both cuses of co-current and countercurrent
flow regimes.
A computer program is established to predict the temperature distribution in
the channels, the heat exchanger effectiveness and the correction factor of the
logarithmic mean temperature dzfference. For this purpose, a com bination of
Jacobian iteration method and Gaussian elimination method is applied to solve
exactly the system of coupled dzflerential equations governing the temperature
distribution in terms of exponential Jirnctions. me computer program is
extended to cover the case of even number of channels (case of complete
unsymmetrical channels) for the sake of comparison. Furthermore, deduced
formulae for predicting the limit values of the correction factor as a finction of
the number of channels and the heat capacity rate ratio are also presented
It is shown that both the effectiveness and the correction factor have high
values in case of counter-$law specially at equal capacity rates than in case of
parallel Jlow. The results indicate also that the correction factor falls slowly
with increasing the eflectiveness, the total number of transfer units and the total
heat qacity rate ratio to reach certain higher limit values in case of counter￾cument flow regimes, while it falls down steeply to approach very low values in
case of co-current flow regimes.
The rate of heat tram$er with plate units of odci number of channels is more
than that with even number in all cases except in units undergoing evaporation
or condensation processes we have the other way round at the limit case. This
means an dition of another thermal plate causes a substantial change in the
heat transfer characteristics of plate heat exchangers.