Design and operation of a Tesla-type valve for pulsating heat pipes

•Designed a new Tesla-valve that was integrated in a pulsating heat pipe.•Performed laminar single phase modelling and steady two-phase flow experiments.•The valve produces diodicity in two-phase flow.•Thermal resistance is reduced by incorporating Tesla valves in the pulsating heat pipe. A new Tesla-type valve is successfully designed for promoting circulation in a pulsating heat pipe (PHP) and improving the thermal resistance. Its functionality and diodicity is tested by laminar single-phase modelling and by steady two-phase flow experiments. The valve is symmetrically integrated in a single-turn PHP, which reduces variabilities to give a more thorough understanding of the behaviour in PHPs. Two transparent bottom-heated PHPs, one with and one without valves, are manufactured and the flow behaviour and thermal performance is studied. The valves produced a diodicity which lead to a difference in velocity of 25% for the different flow directions. Furthermore, a decrease of 14% in thermal resistance was observed due to the addition of the valves.