Method for manufacturing a heat exchanger

Abstract

Heat exchange plates are stacked, with a pressing force applied to the plates so as to maintain parallelism of them and prevent deformation of them during a diffusion bonding process. The stacking condition is maintained and adjacent plates come into contact with each other at projections and peripheral edges. Space surrounding the contact portions of the plates is put in a vacuum or low pressure state in which only an inner gas atmosphere exists. The plates are kept at a temperature at which the diffusion bonding occurs by a predetermined period of time to diffusion-bond portions of the plates, which are only brought into contact with each other and have not been bonded together.

1 . A method for manufacturing a heat exchanger comprising the steps of: placing a plurality of heat exchange plates one upon another, each of which is formed of a metallic plate member having a predetermined pattern of irregularity and combining the plates into a heat exchanger, in which each of the heat exchange plates is formed into a predetermined shape by a press-forming process so that each of the heat exchange plates includes on at least part thereof a heat transfer section having the pattern of irregularity and first and second opposite surfaces with which first and second heat exchange fluids come into contact, respectively, the heat exchange plates as combined come into contact with each other on at least one part of peripheries thereof, and first gap portions through which the first heat exchange fluid is to pass and second gap portions through which the second heat exchange fluid is to pass are provided alternately between the heat exchange plates, wherein, the method further comprising the steps of: 
 placing a predetermined number of the heat exchange plates one upon another to apply a pressing force to the heat exchange plates in a stacking direction thereof to an extent that at least parallelism of the heat exchange plates as placed is maintained and the heat exchange plates are not plastically deformed even when a temperature thereof increases to a predetermined temperature at which a diffusion bonding associated with material of the heat exchange plates occurs, maintaining such a stacking condition and bringing adjacent plates at projections and peripheral edges that protrude from the heat exchange plates into contact with each other; and    putting space surrounding at least contact portions of the plates in a vacuum state or a low pressure state in which only an inner gas atmosphere exists, keeping the plates at a predetermined temperature at which the diffusion bonding occurs by a predetermined period of time and diffusion-bonding portions of the plates, which are only brought into contact with each other and have not been bonded together.    
   
   
       2 . The method as claimed in  claim 1 , further comprising the steps of: 
 welding, at a stage of the step of placing the heat exchange plates one upon another, the adjacent plates at the peripheral edges thereof to form a welded assembly in which no variation in a positional relationship between the plates occurs; and    placing the welded assembly in a vacuum state or a low pressure state in which only an inner gas atmosphere exists, keeping the plates at a predetermined temperature at which the diffusion bonding occurs by a predetermined period of time and diffusion bonding portions of the plates, which are only brought into contact with each other and have not been bonded together.    
   
   
       3 . The method as claimed in  claim 2 , wherein: 
 the step of welding the heat exchange plates is carried out to combine the plates into the welded assembly so that each of the first and second gap portions is isolated from outside, excluding first fluid inlet and outlet portions communicating with the first gap portion and second fluid inlet and outlet portions communicating with the second gap portion, and    the method further comprising the steps of:    connecting first supply/discharge conduits, which permit supply of a fluid into the first gap portion and/or discharge of the fluid therefrom, to the first inlet and out let portions, and connecting second supply/discharge conduits, which permit supply of a fluid into the second gap portion and/or discharge of the fluid therefrom;    removing a gas from the first gap portion through the first supply/discharge conduits to provide the vacuum state therein or supplying an inert gas into the first gap portion while removing a gas therein, through the first supply/discharge conduits, to provide the low pressure state, and supplying an inert gas having a predetermined high temperature and a predetermined pressure into the second gap portion while removing a gas therein, through the second supply/discharge conduits, to provide a higher pressure state than the first gap portion, and then keeping the contact portions of the projections, which are placed in the heat transfer section of each of the plates and exist in the first gap portion, at the predetermined temperature at which the diffusion bonding occurs by the predetermined period of time and diffusion-bonding the contact portions of the plates; and then,    removing a gas from the second gap portion through the second supply/discharge conduits to provide the vacuum state therein or supplying an inert gas into the second gap portion while removing a gas therein, through the second supply/discharge conduits, to provide the low pressure state, and supplying an inert gas having a predetermined high temperature and a predetermined pressure into the first gap portion while removing a gas therein, through the first supply/discharge conduits, to provide a higher pressure state than the second gap portion, and then keeping the contact portions of the projections, which are placed in the heat transfer section of each of the plates and exist in the second gap portion, at the predetermined temperature at which the diffusion bonding occurs by the predetermined period of time and diffusion-bonding the contact portions of the plates.    
   
   
       4 . The method as claimed in  claim 1 , further comprising the steps of: 
 placing the heat exchange plates as combined, in a vessel that is flexibly deformable at least in the stacking direction of the plates and has air inlet and outlet portions, the vessel providing an air-tight property, excluding the air inlet and outlet portions;    applying the pressing force to the plates in the stacking direction thereof and discharging a gas in the vessel through the air inlet and outlet portions; and then    closing the air inlet and outlet portions to keep an inside of the vessel, which includes the space surrounding the contact portions of the plates, in the vacuum state or the low pressure state. portions of the plates.    
   
   
       5 . The method as claimed in  claim 2 , further comprising the steps of: 
 placing the heat exchange plates as combined, in a vessel that is flexibly deformable at least in the stacking direction of the plates and has air inlet and outlet portions, the vessel providing an air-tight property, excluding the air inlet and outlet portions;    applying the pressing force to the plates in the stacking direction thereof and discharging a gas in the vessel through the air inlet and outlet portions; and then    closing the air inlet and outlet portions to keep an inside of the vessel, which includes the space surrounding the contact portions of the plates, in the vacuum state or the low pressure state.    
   
   
       6 . The method as claimed in  claim 1 , comprising the steps of: 
 causing the heat exchange plate placed on one end side in the stacking direction of the heat exchange plates as combined to be electrically connectable to one electrode of an electric power supply for heating through current application, and causing the heat exchange plate placed on another end side in the stacking direction thereof to be electrically connectable to another electrode of the electric power supply; and    applying electric current to the plates placed on the opposite end sides in the stacking direction of the plates to pass a current through all the heat exchange plates, while keeping the space surrounding at least the contact portions of the plates in the vacuum state or the low pressure state, keeping the plates at a predetermined temperature at which the diffusion bonding occurs through heating through current application by a predetermined period of time and diffusion-bonding the portions of the plates, which are only brought into contact with each other and have not been bonded together.    
   
   
       7 . The method as claimed in  claim 2 , comprising the steps of: 
 causing the heat exchange plate placed on one end side in the stacking direction of the heat exchange plates as combined to be electrically connectable to one electrode of an electric power supply for heating through current application, and causing the heat exchange plate placed on another end side in the stacking direction thereof to be electrically connectable to another electrode of the electric power supply; and    applying electric current to the plates placed on the opposite end sides in the stacking direction of the plates to pass a current through all the heat exchange plates, while keeping the space surrounding at least the contact portions of the plates in the vacuum state or the low pressure state, keeping the plates at a predetermined temperature at which the diffusion bonding occurs through heating through current application by a predetermined period of time and diffusion-bonding the portions of the plates, which are only brought into contact with each other and have not been bonded together.    
   
   
       8 . The method as claimed in  claim 4 , comprising the steps of: 
 causing the heat exchange plate placed on one end side in the stacking direction of the heat exchange plates as combined to be electrically connectable to one electrode of an electric power supply for heating through current application, and causing the heat exchange plate placed on another end side in the stacking direction thereof to be electrically connectable to another electrode of the electric power supply; and    applying electric current to the plates placed on the opposite end sides in the stacking direction of the plates to pass a current through all the heat exchange plates, while keeping the space surrounding at least the contact portions of the plates in the vacuum state or the low pressure state, keeping the plates at a predetermined temperature at which the diffusion bonding occurs through heating through current application by a predetermined period of time and diffusion-bonding the portions of the plates, which are only brought into contact with each other and have not been bonded together.    the plates, in the vacuum state or the low pressure state.    
   
   
       9 . The method as claimed in  claim 5 , comprising the steps of: 
 causing the heat exchange plate placed on one end side in the stacking direction of the heat exchange plates as combined to be electrically connectable to one electrode of an electric power supply for heating through current application, and causing the heat exchange plate placed on another end side in the stacking direction thereof to be electrically connectable to another electrode of the electric power supply; and    applying electric current to the plates placed on the opposite end sides in the stacking direction of the plates to pass a current through all the heat exchange plates, while keeping the space surrounding at least the contact portions of the plates in the vacuum state or the low pressure state, keeping the plates at a predetermined temperature at which the diffusion bonding occurs through heating through current application by a predetermined period of time and diffusion-bonding the portions of the plates, which are only brought into contact with each other and have not been bonded together.    
   
   
       10 . The method as claimed in  claim 1 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       11 . The method as claimed in  claim 2 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       12 . The method as claimed in  claim 3 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       13 . The method as claimed in  claim 4 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       14 . The method as claimed in  claim 5 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       15 . The method as claimed in  claim 6 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       16 . The method as claimed in  claim 7 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       17 . The method as claimed in  claim 8 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       18 . The method as claimed in  claim 9 , further comprising the steps of: 
 holding the heat exchange plates as stacked, between cooling plates in the stacking direction of the heat exchange plates, each of the cooling plates being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates, and having a hollow structure, ensuring a state in which heat transfer occurs between the cooling plates and the heat exchange plates, and connecting cooling conduits to the cooling plates so as to enable cooling fluid to be supplied into the cooling plates and discharged therefrom; and    supplying, after completion of diffusion bonding between the heat exchange plates, the cooling fluid into the cooling plates to decrease temperature of the heat exchange plates, while keeping the vacuum state or the low pressure state in which only the inner gas atmosphere exists.    
   
   
       19 . The method as claimed in any one of  claims 1  to  18 , further comprising the steps of: 
 placing, during combining the heat exchange plates together or in a combined state thereof, a spacer between a pair of contact edges of the heat exchange plates and another adjacent pair of contact edges thereof on opposite sides of the combined heat exchange plates, to apply a uniform pressure to the pairs of contact edges of the heat exchange plates, said spacer being made of material, which does not diffusion-bond to the heat exchange plates under diffusion bonding conditions of the heat exchange plates.