This paper deals with the determination of the thermoeconomic optimum conditions for a constant space heat load imposed on the air coil of a combined heating and power (CHP) system using iterative numerical techniques. From the thermodynamic relations and equations derived from the energy balance and heat exchanger characteristics, an objective function and constraining equations are obtained. A computer program is developed based on the Redlich-Kwong equation of state to estimate the thermodynamic properties of the refrigerant fluid R-22. Additional computer subroutines are developed to perform thermodynamic and thermoeconomic optimization. Optimum values of the operating variables are identified at thermodynamic and thermoeconomic optimum conditions. Results show that the total irreversibilities produced in the system and the cost of fuel consumption are minimum at thermodynamic optimum conditions, but the annual cost of owning and operating the system is minimum at the thermoeconomic optimum condition, which is 34% lower than at the thermodynamic optimum condition.

Units: SI