A new graphical exergy targeting representation for processes operating above and below ambient temperature

The main purpose of this paper is to introduce an alternative graphical exergy targeting representation for heat recovery systems. The novel diagram uses a new energy quality parameter referred to in this text as exergetic temperature. The new diagram can be extended to systems with change in pressure; however, such systems will not be considered here. For energy and material recovery systems, a clear graphical representation of the sources, sinks, maximum recovery and minimum utility requirements is of great importance; i.e. for heat ( Linnhoff et al., 1982), mass (El-Halwagi and Manousiouthakis, 1989) and water (Wang and Smith, 1994). The proposed exergy diagram uses a composite representation of sources and sinks for the determination of exergy targets. The exergy targets include recovery, requirements, rejection and destruction of exergy. Two previous exergy representations are evaluated and compared with the proposed one.