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2. ENGINEERING AND TECHNOLOGY, Thermodynamics
In various technical plants there are heat transfer rates at temperatures above that of the environment and other simultaneous heat transfer rates at temperatures below the temperature of the environment. This is the case in cryogenic industrial processes where a cooling effect is produced from a heat source. This is also the case for all absorption refrigeration plants or absorption plants that provide refrigeration and heat pumping, notably for air-conditioning of buildings. In these cases exergetic analysis leads to equations in which some terms are positive and others are negative. This can pose problems in the definition of exergetic, or rational, efficiencies. In this paper ways of resolving these difficulties are discussed.
McGovern, James and Pierre Le Goff. (1996) Termes de signes positif et négatif en analyses exergétiques des flux de chaleur. Revue Générale de Thermique 35(418) (1996), 651-655. doi:10.1016/S0035-3159(96)80061-4