MODELING AND DESIGN OF AN INDIRECT AIR CONDITIONING SYSTEM OPERATING WITH LOWGWP ZEOTROPIC MIXTURES

摘要

Indirect air conditioning can be considered as one of the technical options to reduce the refrigerant charge in order to minimize the emissions to the atmosphere. However, indirect systems are less efficient than direct ones due to the additional irreversibilities in the heat exchangers and the power consumption of the pumps. This problem can be overcome by the use of energy efficient heat exchangers with reduced approach temperature (1 K) and the choice of an efficient secondary fluid with evaluated thermo-physical properties. This paper deals with the modeling and design of an indirect air-conditioning system adapted to fluids with temperature glide. A particular attention is paid to the design of the primary and secondary heat exchangers by taking advantage of the mini-channels technology. The optimized heat exchanger presents high thermal efficiency, minimized pressure drop, and compactness over a conventional technology. The energy efficiency of the indirect system is calculated and comparison is carried out with a conventional direct system in order to predict the reduction of equivalent CO_2 emissions.