Pulsating heat pipe performance enhancement through porous metallic surfaces produced via physical dealloying

Physical dealloying (PD) is explored in this work as a way of creating a porous layer on metallic surfaces to be used for the enhancement of Pulsating Heat Pipe (PHP) thermal performances. PD can be applied to metal alloys consisting of components with a high difference between their partial vapour pressure, such as copper and zinc. Commercially available brass (Cu/Zn alloy) capillary tubes with OD = 2 mm and ID = 1.3 mm were shaped into a four-turn PHP, with a total length of 949 mm. One standard PHP with the same tube diameter, number of turns and total length was tested as benchmark, while other two PHPs were subjected to PD for 0.5 and 2 h, respectively. All PHPs were tested in the range of heat load between 3 and 40 W at a fixed 50 % filling ratio with ethanol as working fluid. The performed tests show that PHPs after PD display up to 30 °C lower average temperature at the evaporator and up to 7 °C lower average temperature of the condenser compared to the benchmark. PD was capable to lower the PHP thermal resistance by up to 4.2 times, from 11.2 to 2.65 K/W, at low heat powers. Furthermore, in the case of PD-treated PHP, the start-up takes place at lower power and temperatures when compared to untreated PHP. This characteristic holds significant value as it expands the range of applications for PHPs, while simultaneously enhancing their reliability, safety, and overall lifespan when used for thermal management in equipment. It is worth noting that this straightforward approach can be tailored for a wide range of thermal management equipment, including conventional, plate, and micro heat exchangers, as well as HVAC systems. This method is particularly suitable for situations where heat transfer takes place through phase change processes.