Heat transfer module

A heat transfer module comprising an evaporator region, a condenser region, and an adiabatic region disposed between the condenser region and the evaporator region, the heat transfer module comprising:

• an envelope sealed to define an internal volume that contains a working fluid and a wick disposed on an internal surface of the envelope, wherein:
• the wick comprises a first portion extending through the evaporator region and a second portion extending through the adiabatic and condenser regions,
• the first portion of the wick comprise a metal hydride and the second portion of the wick comprises stainless steel or a refractory metal,
• the envelope comprises a first portion extending through the evaporator region and a second portion extending through the adiabatic and condenser regions,
• the first portion of the envelope comprises:
• a metal liner surrounding the first portion of the wick;
• a first diffusion barrier layer disposed between the first portion of the wick and the metal liner;
• and
• a ceramic matrix composite cladding surrounding the metal liner;
• the second portion of the envelope comprises a refractory metal and/or stainless steel.