Heat pipe thermal transfer loop with pumped return conduit

A heat pipe system including;

• a heat pipe loop having a first end and a second end, and comprising first and second arms for transferring working fluid from said first end to said second end;
• a first reservoir in fluid communication with said first end for holding working fluid in liquid form;
• a first heat exchanger at said first end for transmitting thermal energy from a heat source to working fluid from said first reservoir in order to vaporize said fluid;
• a second heat exchanger at said second end for transmitting thermal energy from vaporized working fluid to a heat sink thereby condensing said fluid;
• a second reservoir in fluid communication with said second end for holding condensed working fluid in liquid form before said fluid is returned to said first end of said heat pipe loop;
• a return conduit for returning condensed working fluid from said second reservoir at said second end to said first reservoir at said first end, said return conduit thereby forming a priming loop which is separate from said heat pipe loop;
• and
• a pump for pumping said condensed working fluid from said second end to said first end along said return conduit;
• wherein said heat pipe loop, said return conduit, said first reservoir, and said second reservoir form a hermetically sealed circuit, and
• wherein said pump is located inside said sealed circuit and is configured to be driven from outside said sealed circuit.