Phase change actuated valve for use in heat pipe applications

1. A heat exchanger comprising:

a plurality of heat pipes, each of the heat pipes having a thermally actuate control valve;

each thermally actuate passive control valve comprising:

a housing having a first end and a second end, a first opening extending through the first end for receiving a condenser portion of a respective heat pipe therein, a second opening extending through the second end for receiving an evaporator portion of the respective heat pipe therein, a passage extending through the housing from the first opening to the second opening, the passage configured to receive working fluid from the heat pipe therein;

a phase change material actuator positioned in the housing, the phase change material actuator having a sealed chamber with phase change material positioned therein;

a passage closing member positioned in the housing proximate to or in the passage and proximate to the phase change material actuator, the passage closing member having a surface which cooperates with a wall of the passage;

wherein as the temperature of the phase change material reaches a designed temperature, the phase change material melts and expands causing the passage closing member to move into the passage to a closed position, preventing the flow of the working fluid through the valve and into the evaporator portion of the heat pipe, thereby preventing heat transfer between the condenser portion and the evaporator portion when the design temperature is reached or exceeded;

the phase change material of first respective thermally actuate passive control valves positioned in first heat pipes of the plurality of heat pipes is activated or melted at a different temperature than the phase change material of second respective thermally actuate passive control valves positioned in second heat pipes of the plurality of heat pipes.

2. The heat exchanger as recited in claim 1 , wherein the passage closing member is a tapered plug.

3. The heat exchanger as recited in claim 2 , wherein the tapered plug has a tapered section, the tapered section cooperates with a tapered surface of the passage when the tapered plug is moved to the closed position to create a seal between the tapered section of the tapered plug and the tapered surface of the passage, whereby the flow of the working fluid through the valve is prevented.

4. The heat exchanger as recited in claim 1 , wherein the phase change material is a wax.

5. The heat exchanger as recited in claim 1 , wherein the phase change material actuator include a deformable seal at one end of the sealed chamber and a piston, whereby as the phase change material expands, the phase change material deforms the seal and drives the piston outward toward the passage closing member.

6. The heat exchanger as recited in claim 1 , wherein the phase change material actuator is an insert which is positioned in the housing.

7. The heat exchanger as recited in claim 1 , wherein the phase change material actuator is molded in the housing.

8. A heat exchanger for use in a two-phase system, the heat exchanger comprising:

a plurality of heat pipes, each of the heat pipes having a thermally actuate control valve;

each thermally actuate passive control valve comprising:

a housing having a first end and a second end, a first opening extending through the first end for receiving a condenser portion of a respective heat pipe of plurality of heat pipes, a second opening extending through the second end for receiving an evaporator portion of the respective heat pipe of the plurality of heat pipes therein, a passage extending through the housing from the first opening to the second opening, the passage configured to receive working fluid from the respective heat pipe therein;

a phase change material actuator positioned in the housing, the phase change material actuator having a sealed chamber with phase change material positioned therein;

a passage closing member positioned in the housing proximate to or in the passage and proximate to the phase change material actuator, the passage closing member having a surface which cooperates with a wall of the passage;

a return spring cooperates with passage closing member to move the passage closing member to an open position after a temperature of the working fluid drops below the melting point of the phase change material of the phase change material actuator, allowing the working fluid to flow through the passage and the valve, the return spring having sufficient spring force to recompress the solidified phase change material within the phase change material actuator;

a relief spring proximate to the phase change material actuator, the relief spring cooperates with the phase change material actuator to allow additional expansion of the phase change material actuator after the passage closing member is fully closed, the relief spring having a greater spring force than a return spring;

wherein the phase change material of first respective thermally actuate passive control valves positioned in first heat pipes of the plurality of heat pipes has a different melting point than the phase change material of second respective thermally actuate passive control valves positioned in second heat pipes of the plurality of heat pipes.

9. The heat exchanger as recited in claim 8 , wherein the phase change material is located proximate the evaporator portion of the heat pipe.

10. The heat exchanger as recited in claim 8 , wherein the phase change material is located proximate the condenser portion of the heat pipe.