Heat pipe with controlled fluid charge and hydrophobic coating

Abstract

The present invention is a heat pipe having a specified volume of working fluid determined in relation to the interior volume of the heat pipe and a target temperature T T , to provide self-temperature regulation and pressure management. The heat pipe comprises at least a evaporator region and a condenser region having a known interior volume V and a mass of working fluid given by the relationship M wf =D wf at T T ×V where D wf is the density of the saturated vapor of the fluid at temperature T T plus an amount of additional working fluid sufficient to have the rate of evaporation about equal to the rate of condensation for the particular heat pipe configuration. The heat pipe has at least the condenser region having an interior coating of a hydrophobic material.

What is claimed is: 
     
         1 . A heat pipe for providing heat transfer to a heat recipient at a temperature of about T T  comprising at least a evaporator region and a condenser region having a known interior volume V and a determined mass of working fluid at least equal to M wf , whereby the mass of working fluid is determined by the relationship
     M   wf   =D   wf  at  T×V      where D wf  is the density of the saturated vapor of the fluid at temperature T T      
       and at least a portion of the interior volume has vessel walls coated with hydrophobic material. 
     
     
         2 . The heat pipe of  claim 1  wherein the working fluid comprises M wf  plus an additional amount of fluid that, at the temperature of about T T ,
 a. evaporation from the evaporator region is about equal to condensation, and 
 b. rate of supply of condensate to the evaporation region is about equal to rate of evaporation from the evaporation region. 
 
     
     
         3 . The heat pipe of  claim 2  wherein the mass of working fluid is further characterized as an amount sufficient, at about T T , for initiating a gas bubble in the evaporation region when heat is transferred to the heat recipient. 
     
     
         4 . The heat pipe of  claim 3  wherein the mass of the working fluid ranges from about M wf  to about 200% M wf . 
     
     
         5 . The heat pipe of  claim 4  wherein the mass of the working fluid ranges from about M wf  to about 150% M wf . 
     
     
         6 . The heat pipe of  claim 1  wherein the hydrophibic material comprises: hydrocarbon chains, fluorocarbons and/or non-polar siloxane, Teflon and the like. 
     
     
         7 . A method for controlling temperature T T  of heat transfer in a heat pipe having at least an evaporation region and a condenser region, from a heat source to a heat recipient, comprising:
 a. determining interior volume of the heat pipe,   b. selecting a working fluid for the heat pipe having a known density D wf  of its saturated vapor at T T      c. determining a mass of working fluid according to the relationship
     M   wf   =D   wf  at  T   T   ×V,    
   d. supplying at least the mass of working fluid of step c to the heat pipe.   
     
     
         8 . The method of  claim 7  wherein a sufficient amount of working fluid is added to initiate a gas bubble in the evaporation region whenever the temperature of the evaporation zone is above about T T . 
     
     
         9 . The method of  claim 8  wherein the mass of the working fluid ranges from about M wf  to about 200% M wf . 
     
     
         10 . The method of  claim 9  wherein the mass of the working fluid ranges from about M wf  to about 150% M wf .