Temperature Actuated Capillary Valve for Loop Heat Pipe System

• US 20130306278A1
• Filed: 08/09/2012
• Published: 11/21/2013
• Est. Priority Date: 05/16/2012
• Status: Active Grant

• Current Assignee: The Government Of The United States Of America, As Represented By The Secretary 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 9,146,059 B2
• Time in Patent Office: Days
• US Class Current: 165/104.26
• 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 temperature-actuated capillary flow valve for use in a two phase heat transfer system, the valve comprising:

inlet port for receiving working fluid in a vapor-phase;

an outlet port;

and a housing extending between the inlet port and the outlet port, the housing defining a flow passage; and

a porous wick material extending across the flow passage,

the housing configured to be heated by a heat source to evaporate liquid-phase working fluid from the wick and allow the vapor-phase working fluid to pass through the wick to the outlet port, wherein removal of the heat source allows liquid to condense in the wick,

thereby preventing flow of the vapor-phase working fluid through the wick to the outlet port.

2. The flow valve of claim 1, wherein said flow valve is cooled by a thermal strap configured to transfer heat from the valve housing to a heat sink.

3. The flow valve of claim 1, wherein the thermal strap and the heat source are positioned on the housing, with the thermal strap closer to the outlet port and the heat source closer to the inlet port.

4. The flow valve of claim 1, wherein the wick is a sintered porous metal.

5. The flow valve of claim 1, wherein the working fluid is ammonia.

6. The flow valve of claim 1, wherein the heat source is an electrical resistance heating element adhered to the valve housing.

7. The valve of claim 1, in fluid combination with a two-phase capillary pump and with a condenser in a loop heat pipe system.

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

9. The valve of claim 1, wherein the exterior surface of the wick 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.