Abstract: Herein is disclosed a dehumidifier for dehumidifying ambient air in an airstream from an inlet to an exhaust from an outlet in a housing. The dehumidifier comprises an evaporator having an evaporator downstream face and an evaporator upstream face; and downstream 5 from the evaporator a condenser having a condenser downstream face and a condenser upstream face. The dehumidifier further has a thermosiphon arrangement configured to be arranged with a thermosiphon evaporator part upstream from the evaporator and a thermosiphon condenser part upstream from the condenser and downstream from the evaporator. The thermosiphon arrangement comprises a thermosiphon block configured for a refrigerant to communicate between a first header and a second header interconnected with a fluid communicator arrangement being multiple tubes, wherein the thermosiphon block is sealed and contains the refrigerant.

Abstract: The present invention relates to transfer of heat by thermosiphon blocks, thermosiphons or thermosiphon systems configured to be used or assembled to transfer heat. Thermosiphon block configured for a refrigerant to circulate between a first header and a second header interconnected with a fluid communicator arrangement comprising multiple MPE-tubes with fins in-between. The first header may have a receiving volume adapted to receive liquid refrigerant and to distribute the liquid refrigerant to the second header via a liquid communicator. The bock may be sealed. The invention also relates to a thermosiphon system comprising at least a first thermosiphon block. The first thermosiphon block may be configured as an evaporator with the receiving volume in the first header connected to a condenser. The thermodynamic system may have a piping between the first thermosiphon block and the condenser. The first thermosiphon block may be configured to be placed inside of a building, housing or a cabinet.