**2. Methodology**

There are several different variants of heat exchangers, with the common types employed in the industry [27] including:


Illustrations of these heat exchangers and a detailed list of heat exchanger types can be found in Ref. [27].

This paper develops SRTGD-STR. This diagram considers these previously mentioned heat exchanger types in the retrofit design process. The detailed method of implementing the SRTGD-STR is introduced in this section using Example 1 data (Table 1).


**Table 1.** Stream data for Example 1.

Note: *TS* is the supply temperature, (◦C); *TT* is the target temperature, (◦C); *CP* is the heat capacity flow rate, (kW/ ◦C), and *h* is the heat transfer coefficient, (kW/m2· ◦C).

The notation of the heat transfer used in this work for all topology diagrams is the following:

H(number): Utility heater; C(number): Utility cooler; E(number): Recovery heat exchanger.
