Demand-based charging of a heat pipe
A heat pipe includes a reservoir of liquid that is connected to a horizontal portion of the heat pipe via a capillary connection. The heat pipe includes a temperature sensor in proximity to a heat interface in the horizontal portion and a controller that controls a heater for the reservoir. As power into the heat pipe increases, the controller turns on the heater, causing the temperature of the liquid in the reservoir to rise. Liquid then passes from the reservoir through the capillary connection into the horizontal portion, thereby dynamically increasing the amount of liquid in the heat pipe, which increases performance of the heat pipe at higher power levels. When the heater is off, as the heat pipe cools, the liquid condenses and flows back through the capillary connection into the reservoir. The result is a heat pipe that provides demand-based charging of the liquid based on power level.
1. A method for dynamically charging a heat pipe with a liquid, the method comprising:
providing the heat pipe comprising:
an interface for thermally coupling a heat source to the heat pipe;
a substantially horizontal portion charged with a first quantity of liquid and coupled to the interface;
a reservoir that contains a second quantity of the liquid, the reservoir overlying the substantially horizontal portion and having a width and a height, where the width is substantially greater than the height;
a capillary connection that connects the reservoir to the substantially horizontal portion, wherein the capillary connection has a diameter of 0.1 millimeters (mm) to 0.3 mm;
a heater thermally coupled to the reservoir;
a temperature sensor in proximity to the interface; and
a controller coupled to the heater and the temperature sensor;
detecting when a temperature detected by the temperature sensor exceeds a predetermined threshold; and
in response to the detecting when the temperature detected by the temperature sensor exceeds the predetermined threshold, turning on the heater to cause at least a portion of the second quantity of liquid in the reservoir to pass from the reservoir through the capillary connection into the substantially horizontal portion;
detecting when the temperature detected by the temperature sensor is less than the predetermined threshold; and
in response to the detecting when the temperature detected by the temperature sensor is less than the predetermined threshold, turning off the heater to cause at least a portion of the second quantity of liquid in the substantially horizontal portion to pass from the substantially horizontal portion through the capillary connection into the reservoir via capillary action as the reservoir cools.
2. The method of claim 1 wherein the heat pipe further comprises at least one vertical member connected with the substantially horizontal portion.
3. The method of claim 1 wherein the heat pipe further comprises a plurality of fins that dissipate heat.
4. The method of claim 1 wherein the substantially horizontal portion of the heat pipe overlies the interface.
5. The method of claim 1 wherein the substantially horizontal portion, the reservoir, and the capillary connection are made of copper.
6. The method of claim 5 wherein the liquid comprises water.
7. The method of claim 1 wherein the capillary connection has a hydrophobic coating.
8. A method for manufacturing a heat sink comprising:
constructing a heat pipe comprising:
an interface for thermally coupling a heat source to the heat pipe;
a substantially horizontal portion charged with a first quantity of liquid and coupled to the interface;
a reservoir that contains a second quantity of the liquid, the reservoir overlying the substantially horizontal portion and having a width and a height, where the width is substantially greater than the height;
a capillary connection that connects the reservoir to the substantially horizontal portion and draws liquid from the substantially horizontal portion into the reservoir via capillary action when a temperature of the reservoir is less than a temperature of the substantially horizontal portion, wherein the capillary connection has a diameter of 0.1 millimeters (mm) to 0.3 mm;
a heater thermally coupled to the reservoir;
a temperature sensor in proximity to the interface; and
a controller coupled to the heater and the temperature sensor; and
thermally coupling a plurality of thermally-conductive fins to the heat pipe.
9. The method of claim 8 wherein the capillary connection has a hydrophobic coating.