Plate Heat Exchanger

Abstract

A plate heat exchanger has openings in the plates defining supply and return ducts extending through a plate stack. The supply and return ducts are hydraulically connected to flow ducts located between the plates and to a tube arranged coaxially in each of the supply and return duct. The tubes have holes in the tube wall in order to provide the hydraulic connection to the flow ducts. A simple and cost-effective plate heat exchanger which can withstand high pressures is achieved by the tubes extending through the entire stack to form a tie rod between a top side and an underside of the plate stack. The tube has a diameter corresponding to the diameter of the openings in the plates such that the tube wall is firmly metallurgically connected to at least some edges of the openings.

What is claimed is: 
     
         1 . A plate heat exchanger comprising:
 a plurality of plates arranged to form a plate stack, first openings of the plates aligned to form a supply duct extending through the plate stack and second openings of the plates aligned to form a return duct extending through the plate stack, flow ducts being located between the plates to hydraulically connect the supply and return ducts;   a first tube arranged within the supply duct and extending through the entire plate stack, a first end of the first tube being metallurgically joined to a top side of the plate stack and a second end of the first tube being metallurgically joined to a bottom side of the plate stack in order to function as a first tie-rod connection through the plate stack; and   a second tube arranged within the return duct and extending through the entire plate stack, a first end of the second tube being metallurgically joined to a top side of the plate stack and a second end of the second tube being metallurgically joined to a bottom side of the plate stack in order to function as a second tie-rod connection through the plate stack.   
     
     
         2 . The plate heat exchanger of  claim 1 , further comprising:
 a first thick-walled flange arranged at the top side of the plate stack and joined to an uppermost plate of the plate stack, the inlet duct extending through the first thick-walled flange, wherein the metallurgical joint at the first end of the first tube is located within the first thick-walled flange; and   a second thick-walled flange arranged at the top side of the plate stack and joined to the uppermost plate of the plate stack, the return duct extending through the second thick-walled flange, wherein the metallurgical joint at the first end of the second tube is located within the second thick-walled flange.   
     
     
         3 . The plate heat exchanger of  claim 2 , wherein the metallurgical joints a the first end of the first and second tubes comprise braze material arranged in one or more gaps between the first end of the first and second tubes and the first and second thick-walled flanges, respectively. 
     
     
         4 . The plate heat exchanger of  claim 1 , wherein the first and second tubes each comprise a closure cap metallurgically connected to the second end of said tube. 
     
     
         5 . The plate heat exchanger of  claim 1 , wherein:
 at least some of the first openings are provided with first flanges defining a diameter of said first openings that corresponds with a diameter of the first tube, the first tube being metallurgically joined to the first flanges; and   at least some of the second openings are provided with second flanges defining a diameter of said second openings that corresponds with a diameter of the second tube, the second tube being metallurgically joined to the second flanges.   
     
     
         6 . The plate heat exchanger of  claim 5 , wherein:
 the first tube includes a plurality of first holes arranged in a wall of the first tube, the plurality of first holes being arranged between those locations where the first tube is metallurgically joined to the first flanges in order to provide a hydraulic connection between the supply duct and the flow ducts; and   the second tube includes a plurality of second holes arranged in a wall of the second tube, the plurality of second holes being arranged between those locations where the second tube is metallurgically joined to the second flanges in order to provide a hydraulic connection between the return duct and the flow ducts.   
     
     
         7 . The plate heat exchanger of  claim 6 , wherein the first and second tubes each include a circumferential wall portion, directed in a longitudinal direction of the plate heat exchanger, that is without any of the first and second holes. 
     
     
         8 . The plate heat exchanger of  claim 6 , wherein the pluralities of first and second holes are arranged so that a considerable quantity of fluid received into the supply duct is initially forced to flow around the supply duct before flowing in a longitudinal direction of the plate heat exchanger and a considerable quantity of fluid received from the flow ducts is initially forced to flow around the return duct before being received into the return duct. 
     
     
         9 . The plate heat exchanger of  claim 5 , wherein at least some of the first openings are of a diameter that is larger than the diameter of the first tube and wherein at least some of the second openings are of a diameter that is larger than the diameter of the second tube. 
     
     
         10 . The plate heat exchanger of  claim 9 , wherein the flow ducts are hydraulically isolated from cooling fluid flow ducts arranged between the flow ducts by metallurgical joints between plates having a first flange and plates having a first opening of a diameter that is larger than the diameter of the first tube, and by metallurgical joints between plates having a second flange and plates having a second opening of a diameter that is larger than the diameter of the second tube. 
     
     
         11 . The plate heat exchanger of  claim 10 , wherein those first openings having a diameter that is larger than the diameter of the first tube are provided with third flanges, at least some of those third flanges being metallurgically bonded to the first flanges. 
     
     
         12 . The plate heat exchanger of  claim 10 , wherein those second openings having a diameter that is larger than the diameter of the second tube are provided with third flanges, at least some of those third flanges being metallurgically bonded to the second flanges. 
     
     
         13 . A plate heat exchanger comprising:
 a plurality of plates arranged to form a plate stack, adjacent plates in the plate stack being spaced apart to provide a first plurality of closed flow ducts for a flow of oil through the plate heat exchanger and a second plurality of open flow ducts for a flow of liquid coolant through the plate heat exchanger, the first and second pluralities of flow ducts being arranged in alternating sequence;   a first tube extending through the entire plate stack to provide a supply duct for the flow of oil, the first tube having a plurality of holes to hydraulically connect the first plurality of flow ducts to the supply duct; and   a second tube extending through the entire plate stack to provide a return duct for the flow of oil, the second tube having a plurality of holes to hydraulically connect the first plurality of flow ducts to the return duct, wherein at least some of the plurality of plates are metallurgically joined to the first tube and the second tube.   
     
     
         14 . The plate heat exchanger of  claim 13 , wherein the pluralities of holes in the first and second tubes are arranged in intervals along a stacking direction of the plate stack, the metallurgical joints between said at least some of the plurality of plates and the first and second tubes being located between the intervals. 
     
     
         15 . The plate heat exchanger of  claim 14 , wherein the first and second tubes each include a circumferential wall portion, directed in a longitudinal direction of the plate heat exchanger, that is without any of the holes. 
     
     
         16 . The plate heat exchanger of  claim 14 , wherein the pluralities of holes are arranged so that a considerable quantity of oil received into the supply duct is initially forced to flow around the supply duct before flowing in a longitudinal direction of the plate heat exchanger and a considerable quantity of oil received from the closed flow ducts is initially forced to flow around the return duct before being received into the return duct. 
     
     
         17 . The plate heat exchanger of  claim 13 , wherein each of the plates includes a first opening coaxially aligned with the first tube and a second opening coaxially aligned with the second tube, at least some of the plurality of plates being provided with a flange along a continuous edge of the first opening, at least some of the plurality of plates being provided with a flange along a continuous edge of the second opening, the metallurgical joints between the plates and the first and second tubes being provided at the flanges. 
     
     
         18 . The plate heat exchanger of  claim 17 , wherein the plurality of plates comprises:
 a plurality of first plates, each of which is provided with a flange along a continuous edge of at least one of the first and second opening, said flange being metallurgically joined to the corresponding one of the first and second tubes; and   a plurality of second plates interleaved with the first plates, each of the second plates being metallurgically joined to an adjacent one of the plurality of first plates at a first location adjacent to and radially outward of the first tube and at a second location adjacent to and radially outward of the second tube in order to hydraulically separate the first plurality of closed flow ducts from the second plurality of open flow ducts.   
     
     
         19 . The plate heat exchanger of  claim 18 , wherein at least some of said metallurgical joints between the first plates and the second plates are located at said flanges. 
     
     
         20 . The plate heat exchanger of  claim 13 , further comprising:
 a first thick-walled flange arranged at a top side of the plate stack and joined to an uppermost plate of the plate stack, the inlet duct extending through the first thick-walled flange, an end of the first tube being metallurgically joined to the first thick-walled flange; and   a second thick-walled flange arranged at the top side of the plate stack and joined to the uppermost plate of the plate stack, the return duct extending through the second thick-walled flange, an end of the second tube being metallurgically joined to the second thick-walled flange.