عنوان مقاله [English]
Thermodynamic and Economic Optimization of the cooling System in A Building
Afsaneh Sadeghi, Bachlor science student, school of Mechanical Engineering, Arak university of Technology, Arak,Iran.
Somayeh Davoudabadi Farahani, assistance professor, school of Mechanical Engineering, Arak university of Technology, Arak,Iran.
The purpose of this study is to present a decision - making strategy for the best cooling system for building applications based on the comparison criteria.An air conditioning system for a sample building with an area of a floor 97.1m2 is considered. Three cooling systems with R-134a as the working fluid were considered: normal compression refrigeration system, refrigeration system with economizer, refrigeration system with two compressor. First thermodynamic and economic modeling of each of the cycles has been done, followed by considering performance coefficient as thermodynamic representative and the total income requirement as economic representative. The functional pressures and the ratio of mass flow rate in economizer are chosen as decision variables. The optimization method is Multi objective Genetic algorithm (NSGAII) and choosing the final option is done using the Analytic Hierarchy Process. The economic model takes into account the cost of the components, including amortization and maintenance. In order to deﬁne a cost function, which depends on the optimization parameters of interest, component costs have to be expressed as functions of thermodynamic variables. The cost of installation of economizer has increased the cost of the refrigeration cycle with economizer. In this cycle, the flow rate in the evaporator is low and for achieving the chiller load, the heat exchanger surface is more. The cycle performance with economizer is more than two other cycles, and the cycle cost of the cycle with two compressor is more than two other cycles. In the evaluation of options, the scale of performance of performance coefficient is measured by 2 to 1. As it is observed from results, the normal compression refrigeration system is chosen because it is inexpensive to be cheap to other options and then the system with economizer is chosen as the second option. it should be noted that the system with economizer has a faster and faster system than other systems, and if such a criterion does not enter the options, the system of normal refrigeration cycle and cycle with more serious economizer will be increased, and even depending on the weather conditions in region.
Keywords: Multiobjective optimization, thermodynamic and economic modeling, Choice, Refrigeration cycle.