Investigation on the influence of different heat transmission distances on thermo-hydrodynamic characteristics of pulsating heat pipes

•Partial visualization experiments on PHPs with different heat transmission distances were conducted.•The start-up performance deteriorated with the increase of heat transmission distance.•The flow and heat transfer performance deteriorated with the increase of heat transmission distance.•There was an optimal heat transmission distance that made the anti-dry-out ability of the PHP the best.•The heat transmission distance of 1500 mm was approximately equal to the limit heat transmission distance for the PHP in this work.