Method of providing stable pump operation in a two-phase cooling system

Abstract

A method of providing stable pump operation in a two-phase cooling system is disclosed. The method can include providing a cooling system with a reservoir fluidly connected to a pump. The reservoir can include a liquid-vapor interface when partially filled with liquid coolant. The liquid-vapor interface can separate an amount of liquid coolant from an amount of vapor coolant. The method can include delivering two-phase bubbly flow to an upper portion of the reservoir above the liquid-vapor interface. The two-phase bubbly flow can include vapor bubbles of coolant dispersed in liquid coolant. The vapor bubbles can condense upon interacting with and transferring heat to subcooled liquid coolant in the reservoir. The method can include delivering a continuous outlet flow of single-phase liquid coolant from the reservoir to the pump, thereby ensuring stable pump operation despite the presence of two-phase flow in certain portions of the cooling system.

What is claimed is: 
     
         1 . A method of providing a continuous flow of single-phase liquid to a pump in a cooling apparatus in which two-phase flow is present but is condensed upstream of the pump to provide stable pump operation, the method comprising:
 providing a cooling apparatus comprising a reservoir fluidly connected to a pump, the reservoir configured to store an amount of coolant, the reservoir comprising a liquid-vapor interface in an upper portion of the reservoir when partially filled with liquid coolant, the liquid-vapor interface separating an amount of substantially liquid coolant from an amount of substantially vapor coolant;   delivering an inlet flow of single-phase liquid coolant to the reservoir;   delivering two-phase bubbly flow to an upper portion of the reservoir above the liquid-vapor interface, the two-phase bubbly flow of coolant comprising vapor bubbles of coolant dispersed in liquid coolant, wherein the vapor bubbles condense upon interacting with and transferring heat to the amount of liquid coolant in the reservoir; and   delivering a continuous outlet flow of single-phase liquid from a lower portion of the reservoir to a pump to provide stable pump operation, the lower portion being located below a midpoint of the reservoir.   
     
     
         2 . The method of  claim 1 , wherein the inlet flow of single-phase liquid coolant has a first flow rate and the two-phase bubbly flow has a second flow rate, the first flow rate being equal to or greater than the second flow rate. 
     
     
         3 . The method of  claim 1 , wherein the amount of liquid coolant in the reservoir occupies about 50-90, 60-80, or 65-75 percent of an interior volume of the reservoir. 
     
     
         4 . The method of  claim 1 , wherein providing the flow of single-phase liquid coolant to the reservoir comprises providing a flow of single-phase liquid coolant that is subcooled below its saturation temperature. 
     
     
         5 . The method of  claim 4 , wherein providing the flow of single-phase liquid coolant that is subcooled below its saturation temperature comprises providing a flow of single-phase liquid coolant that is subcooled about 2-8, 5-12, or 10-15 degrees C. below its saturation temperature. 
     
     
         6 . The method of  claim 1 , wherein providing the flow of single-phase liquid coolant to the reservoir comprises providing a flow of single-phase liquid coolant at a pressure of about 10-20, 15-25, 20-30, or 25-40 psia. 
     
     
         7 . The method of  claim 1 , wherein providing the flow of single-phase liquid coolant to reservoir comprises providing a flow of single-phase coolant comprising a dielectric coolant with a boiling point of about 10-35, 20-45, 30-55, or 40-65 degrees C. determined at a pressure of 1 atmosphere. 
     
     
         8 . A method of providing stable operation of a pump in a two-phase cooling apparatus by condensing a two-phase flow upstream of the pump and providing substantially single-phase liquid coolant to the pump to ensure stable pump operation, the method comprising:
 providing a first flow of coolant comprising a two-phase bubbly flow of coolant comprising vapor bubbles of coolant dispersed in liquid coolant, the first flow of coolant having a first flow quality greater than zero;   providing a second flow of coolant comprising a single-phase flow of coolant, the second flow of coolant having a second flow quality of about zero;   mixing the first flow of coolant and the second flow of coolant to form a return flow of coolant, wherein mixing the first flow of coolant and the second flow of coolant causes heat transfer from the first flow of coolant to the second flow of coolant and causes at least a portion of the vapor bubbles of coolant within first flow of coolant to condense, wherein the return flow of coolant has a return flow quality that is less than the first flow quality of the first flow of coolant;   delivering the return flow of coolant to a reservoir comprising a supply of subcooled single-phase liquid coolant, wherein mixing the return flow with the supply of subcooled single-phase liquid coolant causes heat transfer from the return flow to the supply of subcooled single-phase liquid coolant thereby condensing any remaining vapor bubbles in the return flow; and   providing an outlet flow of subcooled single-phase liquid coolant from the reservoir to a pump to ensure stable pump operation.   
     
     
         9 . The method of  claim 8 , further comprising delivering a third flow of coolant to the reservoir, the third flow of coolant comprising a single-phase flow of coolant, the third flow of coolant passing through a heat exchanger and being subcooled to about 10-15, 12-20, or 15-30 degrees C. below its saturation temperature before being delivered to the reservoir. 
     
     
         10 . The method of  claim 8 , wherein providing the outlet flow of subcooled single-phase liquid coolant from the reservoir to the pump comprises providing a flow of single-phase liquid coolant that is subcooled about 2-8, 5-12, or 10-15 degrees C. below its saturation temperature. 
     
     
         11 . The method of  claim 8 , wherein delivering the return flow of coolant to the reservoir comprises delivering the return flow of coolant to an upper portion of the reservoir above a liquid-vapor interface in the reservoir, the liquid-vapor interface separating an amount of substantially liquid coolant from an amount of substantially vapor coolant. 
     
     
         12 . The method of  claim 8 , wherein the first flow quality of the first flow of coolant is greater than zero and less than about 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5. 
     
     
         13 . The method of  claim 8 , wherein the reservoir is in thermal communication with a heat exchanger, the heat exchanger configured to subcool coolant within the reservoir to about 2-8, 5-12, or 10-15 degrees C. below its saturation temperature. 
     
     
         14 . The method of  claim 8 , wherein delivering the return flow of coolant to the reservoir comprises directing the return flow of coolant against an inner surface of the reservoir to promote condensing of the vapor bubbles in the return flow of coolant. 
     
     
         15 . A method of providing stable operation of a pump in a two-phase cooling apparatus by condensing a two-phase flow upstream of the pump and providing substantially single-phase liquid coolant to the pump to ensure stable pump operation, the method comprising:
 providing a cooling apparatus comprising: an inlet manifold, an outlet manifold, a cooling line extending from the inlet manifold to the outlet manifold, and a bypass extending from the inlet manifold to the outlet manifold, wherein the cooling line is fluidly connected to a heat sink module that is mounted on a heat-providing surface;   providing a flow of single-phase liquid coolant to the inlet manifold;   flowing a first flow portion of the flow of single-phase liquid coolant through the cooling line from the inlet manifold to the outlet manifold, wherein the first flow portion passes through the heat sink module and absorbs a sufficient amount of heat from the heat-providing surface to cause a fraction of the first flow portion to change phase from a liquid to a vapor thereby forming a two-phase bubbly flow of coolant;   flowing a second flow portion of the flow of single-phase liquid coolant through the bypass from the inlet manifold to the outlet manifold;   mixing the first flow portion and the second flow portion in the outlet manifold to form a mixed flow, wherein mixing the first and second flow portions causes heat transfer from the first flow portion to the second flow portion thereby condensing at least a portion of the vapor from the first flow portion;   delivering the mixed flow to a reservoir containing a supply of subcooled liquid coolant wherein any remaining vapor from the mixed flow is condensed to liquid; and   providing an outlet flow of substantially liquid coolant from a lower portion of the reservoir to a pump to provide stable pump operation.   
     
     
         16 . The method of  claim 14 , wherein flowing the first flow portion of the flow of single-phase liquid coolant through the cooling line comprises flowing a first flow rate of about 0.1-10, 0.2-5, 0.3-2.5, 0.6-1.2, or 0.8-1.1 liters per minute of coolant through the first cooling line, and wherein flowing the second flow portion of the flow of single-phase liquid coolant through the bypass comprises flowing a second flow rate through the bypass, the second flow rate being greater than or equal to the first flow rate. 
     
     
         17 . The method of  claim 14 , wherein providing the flow of single-phase liquid coolant to the inlet manifold comprises providing a flow of single-phase liquid coolant that is subcooled about 2-8, 5-10, or 12-15 degrees C. below its saturation temperature. 
     
     
         18 . The method of  claim 14 , wherein providing the flow of single-phase liquid coolant to the inlet manifold comprises providing a flow of single-phase liquid coolant at a pressure of about 10-20, 15-25, 20-30, or 25-45 psia. 
     
     
         19 . The method of  claim 14 , wherein providing the flow of single-phase liquid coolant to the inlet manifold comprises providing a flow of single-phase coolant comprising HFE-7000, HFE-7100, or R-245fa. 
     
     
         20 . The method of  claim 14 , further comprising routing a third flow portion of the flow of single-phase liquid coolant from the reservoir through a heat exchanger and back to the reservoir to provide a flow of subcooled single-phase liquid coolant to the reservoir, the third flow portion being subcooled about 10-15, 12-20, or 15-30 degrees C. below its saturation temperature upon exiting the heat exchanger and returning to the reservoir.