Experimental parameter studies on a two-phase loop thermosyphon cooling system with R1233zd(E) and R1224yd(Z).

• Experiments on Two-phase loop thermosyphon (TPLT) studying influencing parameters. • Self-regulation compensates changes in heat load, height difference, mass flow rate. • Identification of optimal charge avoiding instabilities and critical temperatures. • Low-GWP refrigerants R1233zd(E) and R1224yd(Z) are suitable for thermosyphons. Two-phase loop thermosyphon (TPLT) is a promising technology looking at highly effective electronics cooling. Due to strong coupling between the internal and external parameters, in this study experimental tests in steady-state are carried out using R1233zd(E) and R1224yd(Z) as a working fluid to investigate the respective influences and resulting design requirements. The relationship between the governing thermal and flow equations is presented to facilitate the interpretation of the test results. The study shows a stable flow and cooling performance over a wide range of heat loads and recooling temperatures. The refrigerant charge is identified as one of the main influencing factors, with an optimum being between excessive subcooling and beginning dry-out. Both tested refrigerants lead to basically similar results, showing minor differences regarding thermal performance and system stability. [ABSTRACT FROM AUTHOR]