Research and Development of Packaged Air-conditioners Intended to Improve Annual Efficiency

－1st Report: Design of Packaged Air-conditioner

Abstract

We propose a packaged air-conditioner that improves the annual efficiency by 50% compared with that of the conventional one. To achieve this aim, we developed (i) a highly efficient wide-range compressor that improves the heat pump efficiency in the case of 30-40% air-conditioning loads, (ii) a heat exchanger that is optimized for both a vapor compression refrigeration system and refrigerant natural circulation system, (iii) an adaptive controller that suppresses unnecessary start-and-stop compressor operation, and (iv) a refrigerant natural circulation system that enables highly efficient operation under a low ambient temperature condition. We evaluated the annual efficiency of the developed system and proved that it is 1.52 times more efficient compared with that of the conventional one in simulation studies.