New aspects in thermal systems at low ambient impact: Experimental study on interconnected natural circulation loops

Significant research efforts are being carried out in this century to reduce the environmental impact of energy production and transportation technologies. The greenhouse effect caused an increase in the average temperature, and one of the targets is to keep it below two degrees Celsius. An interesting technology for transferring thermal energy without active devices (such as a pump or blower) is natural circulation in loops. These thermal circuits find applications in various engineering fields, such as geothermal implants, the cooling of new-generation nuclear reactors, electronic components, and solar systems. This paper presents an experimental study of natural circulation in interconnected loops. In particular, thermo-hydraulic behavior is studied when different parameters, such as power transferred to the fluid and the inclination of the entire loop assembly (referred to as the gravitational field), change. The interaction between multi-connected loops was observed for the first time, showing a direct dependence on the inclination angle and the input power differences of the three circuits. The maximum temperature difference and interaction intensity were observed at the higher inclination angle of 60°.