Thermally Powered Small Ejector Cooling System with Refrigerant R600 Butane

Slovak University of Technology, Faculty of Mechanical Engineering, Bratislava

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Abstract

This paper presents the development and prototyping of a small- scale ejector cooling system (ECS) driven entirely by solar thermal energy. A novel axisymmetric minimum-length supersonic nozzle, optimized using the method of characteristics and designed for efficient entrainment, was manufactured via metal 3D printing along with the ejector in a single integrated unit. The system uses R600 butane as a natural refrigerant due to its low environmental impact and favorable thermodynamic properties. The prototype is designed for a cooling capacity of 1.5 kW with an expected energy efficiency ratio (EER) of 0.42. Thermal energy is harvested by three flat-plate solar collectors from Thermosolar, mounted on the experimental facade. This facade serves a dual function: it reduces the building’s thermal load and simultaneously provides the thermal energy required for the cooling system. The proposed setup demonstrates the viability of a fully thermally driven cooling device with no moving parts, minimal electricity use, and strong potential for building integration. It represents a promising solution for passive and active energy-efficient architecture in warm climates.