HYSYS Operations Guide

4-94 Heat Exchanger
Steady State Rating Model
The Steady State Rating model is an extension of the End Point
model to incorporate a rating calculation, and uses the same
assumptions as the End Point model. If you provide detailed
geometry information, you can rate the exchanger using this
model. As the name suggests, this model is only available for
steady state rating.
When dealing with linear or nearly linear heat curve problems,
the Steady State Rating model should be used. Due to the
solver method incorporated into this rating model, the Steady
State Rating model can perform calculations exceptionally faster
than the Dynamic Rating model.
Figure 4.60
The following parameters are available on the Parameters page
when the Steady State Rating model is selected:
Parameters Description
Tubeside and
Shellside
Delta P
The pressure drops (DP) for the tube and shell sides of the
exchanger can be specified here. If you do not specify the
Delta P values, HYSYS calculates them from the attached
stream pressures.
UA The product of the Overall Heat Transfer Coefficient, and
the Total Area available for heat transfer. The Heat
Exchanger duty is proportional to the log mean
temperature difference, where UA is the proportionality
factor. The UA can either be specified, or calculated by
HYSYS.
4-94