Significance of Magnetic Nano Fluids in Pulsating Heat Pipes - A Review

Pulsating heat pipe (PHP) is a unique device for the management of thermal systems having brilliant chances of wide spread applications because of its simple design, low cost, and excellent ability to transfer heat. Numerous research investigations have been carried out for enhancement of heat transfer performances of PHPs taking into account the operation mechanisms and working fluids. The main purpose of this review is to provide a brief summary on the use of ferrofluids as one class of magnetic nanofluids in the PHPs and its impact on enhancement of heat transfer. The influence of working fluid, number of turns, and inclination angle has also been discussed on flow pattern and thermal performances of a PHP. The ferrofluids offer significant heat transfer enhancement due to higher thermal conductivity in the presence of magnetic fields, lower viscosity, and surface tension compared to conventional working fluids and ordinary nanofluids. The ferrofluids exhibit strong influence on the flow regime at increased heat input leading to higher vapor generation which can transform slug plug flow to annular flow resulting in augmented heat transfer rate. The application of magnetic field facilitates the mixing of flow in a turbulent manner which results in increased heat transfer by convection in the vicinity of the magnet. Thus, significantly high heat transfer can be achieved using ferrofluids with higher concentration as working fluids. The recent developments in the application of PHPs in solar heating, electronic cooling and waste heat recovery systems are discussed in the present review. Simultaneously, the challenges and future scope in the application of ferrofluids in PHPs have been highlighted for further investigation.