Loop Heat Pipe

Loop heat pipes are created from a specially-designed evaporator and a smooth tube that loops from one end of the evaporator to a compensation chamber that feeds into the other end of the evaporator. The smooth tubing is shaped into the condenser, and the evaporator is connected to the heat source. The porosity of the wick structure in the evaporator creates a capillary pumping head that pushes the vapor form of the working fluid into the condenser, where the lower pressure of the smooth tubing allows the liquid form of the working fluid to flow to the compensation chamber. The compensation chamber resupplies the evaporator, where the heat from the heat source turns the fluid into vapor form again.

This single-direction two-phase flow allows the heat from high heat flux sources to be ejected at a remote location from the heat source, and allows thermal transfer over longer distances than standard heat pipes. Since the flow of both phases of the working fluid moves in the same direction, the entrainment limit on thermal performance in conventional heat pipes does not apply to loop heat pipes. Loop heat pipes have several applications in industries that favor lightweight and efficient high heat flux cooling solutions, such as aerospace, micro-gravity and zero-gravity environments, and electronics cooling.

Novark is developing this product to bring it into mass production. Please contact Novark if there is interest in prototype loop heat pipe thermal management solutions. Novark constructs its loop heat pipes from copper and uses copper powder to construct its sintered wick structures.

Below is a case study of a prototype loop heat pipe thermal management solution for PC graphic cards or laptop PC cooling. This miniature loop heat pipe uses a patented evaporator design that combines the compensation chamber with the evaporator in one flat body, creating a low-power thermal cooling solution able to accommodate geometries other cooling solutions cannot address.

Orientation Heat Load Case Temperature Evaporator Temperature Temperature Difference
Horizontal 40 55.9 48.4 7.5
80 61.5 50.7 10.8
150 69.8 54.6 15.2
200 77.4 60 17.4
Vertical 40 57.1 51.5 5.6
80 61.5 50.7 10.8
150 69.8 54.6 15.2
200 77.4 60 17.4
Anti-Gravity 40 59.1 55.6 3.5
80 61.5 50.7 10.8
150 69.8 54.6 15.2
200 77.4 60 17.4
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