Experimental study of water vaporization occurring inside a channel of a smooth plate-type heat exchanger at subatmospheric pressure

•Experimental set-up working as a pump-assisted closed-loop thermosyphon was built.•Water vaporization inside a channel of a plate-type heat exchanger at subatmospheric pressure was observed.•Three main flow regimes were identified.•Influence of these regimes on heat transfer were discussed.•Overall heat transfer coefficients were estimated.