U.S. patent application 20190175395 (applicant RecensMedical Inc., Ulsan, South Korea):
"The present disclosure provides a device and a method for cooling living tissues for a medical purpose and other purposes. The cooling device comprises: a container configured to accommodate a cooling medium and thermally coupled with the cooling medium by directly contacting the cooling medium; a cooling generator configured to be thermally coupled with the container by a direct contact and thereby to provide cooling energy to the cooling medium; and a heat sink dissipating heat from the cooling generator. ... [The] heat transfer medium  may comprise a heat pipe or a vapor chamber and may include a pipe body and phase change material (PCM) provided inside the pipe body. The pipe body may be made of material having the high thermal conductivity so as to effectively transfer the heat from the cooling generating unit that is in contact with the heat transferring medium to the PCM therein."