Study of the operating characteristics of a pump-driven thermosyphon loop with gas–liquid separation

Abstract

Pump-driven thermosyphon loop (PDTL) is a highly efficient cooling method for air-conditioning systems in data centers. Typically, the refrigerant in gas–liquid two-phase state leads to significant pressure drop in pipes following evaporator, which results in more energy consumption for data centers cooling. This study proposes a novel PDTL with gas–liquid separation (PDTLGLS), aiming to separate the gas–liquid phase refrigerant into liquid phase and gas phase, to reduce pressure drop following evaporator and improve the PDTL performance using a gas–liquid separator. Driven by the pressure difference between the gas–liquid separator and the reservoir, the gas-phase refrigerant is condensed into liquid-phase refrigerant back to the reservoir and the liquid-phase refrigerant returns to a reservoir directly without heat exchanging. This paper firstly conducted a theoretical analysis of PDTLGLS. Then the experiments were conducted using R134a to investigate the influence of refrigerant flow rate and heating power on the performance of PDTLGLS. Furthermore, transient characteristics of the PDTLGLS were experimentally analyzed by varying the heating power. The experimental results show that the PDTLGLS achieves 36.8%-53.3% less heat dissipation temperature difference (from evaporator to condenser) and 28.3%–33.3% higher EER than traditional PDTL, and lower dryness could enlarge the PDTLGLS advantages. Furthermore, both analysis results and experimental results show that the PDTLGLS can adjust to diverse refrigerant mass flow and heating power via the self-regulation of the liquid height in the gas–liquid separator, which implies that the PDTLGLS is an effective way to enhance the traditional PDTL performance and could sustain stable operation across a broad spectrum of operating conditions.