Approaches for empirical modeling include regression analysis,
polynomial curve fitting and artificial neural networks [1,2].
These methods involve constructing condenser models from
experimentally obtained input/output data, with no recourse to
any laws concerning the fundamental nature and properties of
the system. In empirical modeling, no a priori knowledge about
the process is necessary, the system is treated like a ‘‘black box,”
and the experimental information gathered from its response to
external stimuli is used to ‘‘identify” what goes on within the
‘‘box”. This type of modeling approaches particularly beneficial
when there is a lack of knowledge required to form the equations
and determine plant parameters but there is an abundance of
process data. However, the model performance will typically degrade
rapidly when it attempts to extrapolate beyond the range
of the training data.
Theoretical modeling, based on physical laws of the condensation
process, may overcome the shortcomings of empirical modeling
methods by providing global description of the heat exchanger
properties. Among the existing methods, Martins Costa and Paris
[3] divided the heat exchanger into three distinct sections: a superheated
section, a two-phase region, and a subcooled section, and
employed the e-NTU approach for each section to predict the performance
of air-cooled condensers. Using the same methodology,
Yohanis, et al. [4] proposed a simple method to calculate heat flow
through a two-phase heat exchanger by eliminating the requirement
of separately simulating each section. Ge and Copper [5,6]
developed steady-state simulation models for fin-and-tube aircooled
condensers by first splitting the condenser into four-section
control volumes in which the two-phase region is further separated
into two sections based on the changes of heat transfer coefficient
(HTC). Then, both distributed parameter and the lumped
parameter methods were suggested to predict 3-D parameter variations
at both air and refrigerant sides. Aprea and Maiorino [7] acquired
a homogeneous model to forecast the performances of the
condenser using the condensing refrigerant. Corberan and Melon