Temperature Actuated Capillary Valve for Loop Heat Pipe System

• US 20150345872A1
• Filed: 08/10/2015
• Published: 12/03/2015
• Est. Priority Date: 05/16/2012
• Status: Active Grant

• Current Assignee: U.S. Government As Represented By The Seceretary Of The Navy
• Original Assignee: The Government Of The United States Of America, As Represented By The Secretary Of The Navy
• Inventors: Hoang, Triem T.
• Granted Patent: US 10,030,914 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F28D 15/043 forming loops, e.g. capillary pumped loops
• CPC Class Codes: F28D 15/06 Control arrangements therefor

Abstract

A capillary flow valve for use in a two phase heat transfer system such as a loop heat pipe, including an inlet port for receiving working fluid in a vapor-phase, an outlet port for outputting working fluid in a vapor-phase, and a porous wick material extending across the interior of the valve. Heating the wick evaporates liquid-phase working fluid from the wick and allows the vapor-phase working fluid to pass through the wick to the outlet port. Removing the heat allows liquid to condense in the wick, preventing flow of the vapor-phase working fluid through the wick to the outlet port.

Claims

1. A method for controlling the flow of vapor-phase working fluid through a temperature-actuated capillary flow valve into a condenser in a two-phase heat transfer system having a working fluid with a liquid-phase and a vapor-phase, comprising:

providing the temperature-actuated capillary flow valve having an inlet port, an outlet port, a housing extending between the inlet port and the outlet port, the housing defining a flow passage, and a porous wick material within the housing and extending across the flow passage;

introducing the vapor-phase working fluid into the inlet port of the capillary flow valve; and

controlling flow of the vapor-phase working fluid through the capillary flow valve by heating the housing to evaporate liquid-phase working fluid from the wick and allow the vapor-phase working fluid to pass from the inlet port through the wick to the outlet port, or by removing the heat source to allow the vapor-phase working fluid in the wick to condense and prevent flow of the vapor-phase working fluid from the inlet port through the wick to the outlet port.

2. The method according to claim 1, wherein the capillary valve is positioned with the output port at a fluid entrance to an evaporator in the two-phase heat transfer system.

3. The method according to claim 1, wherein the capillary flow valve is cold-biased by a thermal strap to a heat sink.

4. The method according to claim 1, wherein said heating the housing comprises activating an electrical resistance heating element adhered to the housing.

5. The method according to claim 1, wherein the capillary flow valve is cold-biased by a thermal strap, said heating the housing comprises activating an electrical resistance heating element adhered to the capillary valve housing, and the electrical resistance heater is positioned closer to the inlet port than the thermal strap.

6. The method of claim 1, wherein the heat source is an electrical resistance heating element adhered to the valve housing at a location along the housing between the outlet port and the thermal strap, and the thermal strap is located between the inlet port and the heating element.

7. The method according to claim 1, wherein the working fluid comprises ammonia.

8. The method of claim 1, wherein the exterior surface of the porous wick material is smooth, with a close fit to the interior surface of the housing.

9. The method of claim 1, wherein the exterior surface of the porous wick material has at least one longitudinal groove extending the length of the wick.

10. A two-phase heat transfer system comprising:

at least one two-phase loop heat pipe capillary pump;

at least one condenser;

a vapor conduit joining the outlet of the capillary pump to the inlet of the condenser;

a liquid conduit joining the outlet of the condenser to the inlet of the capillary pump; and

a thermally-actuated capillary flow valve having an inlet, an outlet, a thermal connection to a heat sink for cold biasing the capillary valve, a porous wick extending across the flow passageway of the flow valve, and a heater thermally connected to the capillary flow valve, wherein actuation of the heater evaporates liquid in the wick, thereby allowing passage of vapor through the capillary flow valve.

11. A two-phase heat transfer system comprising:

at least one two-phase loop heat pipe capillary pump;

a plurality of condensers, each condenser having a thermal connection to a cold sink at an external face of the spacecraft;

a vapor conduit joining the outlet of the capillary pump to the inlets of the condensers;

a liquid conduit joining the outlets of the condensers to the inlet of the capillary pump; and

a plurality of thermally-actuated capillary flow valves, each arranged in the vapor line at an inlet of each condenser,

each thermally-actuated capillary flow valve having an inlet, an outlet, a thermal connection to a heat sink for cold biasing the capillary valve, a porous wick extending across the flow passageway of the flow valve, and a heater thermally connected to the capillary flow valve, wherein actuation of the heater evaporates liquid in the wick, thereby allowing passage of vapor through the capillary flow valve to the condenser.