Performance optimization of a hybrid cooler combining vapor compression and natural circulation cycles

Abstract

A hybrid cooler combining vapor compression and natural circulation cycles was developed for the cooling of telecommunication equipment in the cabinet-type base station of mobile communication. This hybrid cooler normally operates in the vapor compression mode at high ambient temperatures, but works in the natural circulation mode at low ambient temperatures by the thermosiphon principle. The performance of the hybrid cooler was measured according to the refrigerant charge, outdoor temperature, heat exchanger geometry, and the vertical distance between the condenser and the evaporator. The optimum design conditions for these variables are discussed with respect to the performance of the hybrid cooler in both operating modes. The difference in the optimum refrigerant charge between the two operating modes was solved by installing a liquid receiver. The temperature difference between the indoor and ambient air was introduced as a control parameter for use when changing the operating mode. (C) 2008 Elsevier Ltd and IIR. All rights reserved.