refractory metals etc other materials may also be used for the external casing the wick structure of heat pipe 252 a can be of various kinds in exemplary embodiments a grooved wick structure a screen mesh wick structure or a sintered powder wick structure may be used various materials may be used to make the wick 321 the wick 321 may also be absent in an exemplary embodiment the geometry structure and surface size of the wick 321 the pipe 262 a diameter and length and the type of fluid 311 a influence the heat flux capability of the heat pipe and the angles of operation of the heat pipe for example heat pipes may transport heat both in the direction of gravity and against gravity hence heat pipes may have many orientations as needed inside transformer 240 a heat pipes may be customized for transformer type and power transformer spatial orientation locations inside the transformer etc any type of heat pipes including off the shelf heat pipes may be used for transformer cooling as described in the current application a few exemplary types of heat pipes which may be used for transformer cooling as described in the current invention are described in the.