Waste heat recovery from internal combustion engines (ICEs) is one potential
option to improve overall vehicle efficiency. Rankine cycles based on engine
coolant and exhaust heat sources have demonstrated their effectiveness in
enhancing brake thermal efficiency. Critical to their success is the design of
the heat exchanger for the evaporator, with shell-and-tube heat exchangers
(STHEs) a common hardware choice. However, little experimental data exists
evaluating STHEs with the pulsating flow encountered in the exhaust of ICEs. In
addition, correlations for periodically varying flow do not appear to be used in
the modeling of STHEs. To alleviate this limitation, this study combined
experiments using a pulsating exhaust heat source from an ICE under low loads at
a single engine speed with a one+one-dimensional model to evaluate tube- and
shell-side heat transfer correlations for a STHE without baffles. Four working
fluids, water, ethylene glycol, propylene glycol, and a 50/50 ethylene
glycol–water mixture, were examined. The combined thermodynamic properties of an
ethylene glycol–water mixture were the most effective based on an evaluation of
heat exchanger effectiveness, overall heat transfer coefficient, exergetic
efficiency, and entropy generation. A Pearson correlation analysis identified
the inlet working fluid temperature as the parameter most strongly correlated
with STHE performance due to its higher enthalpy. From a modeling perspective,
the pulsating flow correlation of Al-Haddad and Al-Binally predicted greater
heat transfer rates in the STHE. In combination with all shell-side correlations
tested, simulations still underpredict performance relative to experimental
results. An optimized correlation developed specifically for the geometry of
this unbaffled STHE matched the experimental data more closely but likely
overpredicted shell-side heat transfer. Monte Carlo uncertainty propagation
based on sensor uncertainties showed that the differences in effectiveness and
overall heat transfer coefficient exceeded measurement uncertainty. Furthermore,
sensitivity analysis demonstrated the importance of accurate thermophysical
property values and indicated that the underprediction likely reflects coupled
limitations in both tube- and shell-side formulations, with correlations on each
side exerting a comparable influence on predicted heat transfer.
