scope:

ESDU 00042 describes the program EXPRESSplus which provides the rapid approximate design and performance predictions and cost estimates of shell-and-tube heat exchangers. EXPRESSplus complements detailed shell-and-tube heat exchanger design packages such as those available from HTRI and HTFS which are typically used in an iterative fashion. It approximates heat transfer and pressure drop on both tube side and shell side and assumes constant fluid properties. Those restrictions are not of great significance when most heat exchangers are designed as there is uncertainty about the operating conditions. EXPRESSplus is a user-friendly program with simple on-screen prompting for input data. Using EXPRESSplus the designer sets geometry, pressure drop and a thermal duty. From those data the program creates a design space plot of tube count against length on which curves of pressure drop and heat transfer divide the graph into areas in which the exchanger is either under- or over-performing. The effect of changing baffle cut, shell type and number, and other geometric features is instantly shown on the graph and the optimum design is obvious.

A further curve represents, for crude oil, the Ebert-Panchal criterion for the threshold below which no fouling will occur (see ESDU 00016) so that designs not liable to fouling are readily seen. Other fouling curves show the design space for no fouling based on wall temperature limits, useful for waxing and crystalizing duties, and tube flow velocities, useful for biofouling. The cost of the exchanger is also estimated. Response curves that assist in assessing operability are also created by the program showing the variation with tube side or shell side outlet temperature of, firstly, fouling resistance and, secondly, operating conditions expressed as a fraction of design conditions. A final response plot shows the outlet temperatures as a function of flowrate. From these response curves the effect of operational changes can be evaluated and the effect of uncertainties in the data can readily be seen.

Additional discussion of the use of EXPRESSplus to calculate the effect of fouling is found in ESDU 00016. Program INTEGRITY deals with the design of new heat exchanger networks and is described in ESDU 00043.