Water craft jet pump heat exchanger

Abstract

A water jet propelled water craft has a jet pump impeller ( 24 ) mounted in a jet tube ( 18 ) and driven by a water cooled engine ( 16 ). A heat exchanger ( 30′ ) for the engine coolant is incorporated into a housing for the jet pump impeller ( 24 ) and takes the form of a chamber surrounding a through bore of the jet tube ( 18 ). The chamber has an inlet and an outlet for the flow of coolant and contains a series of staggered baffles that define an oscillatory and circumferential flow path for the coolant between the inlet and outlet.

1 . A heat exchanger for use in association with a jet tube of jet propulsion water craft, the heat exchanger comprising a chamber which, in use, is disposed around the jet tube or forms a peripheral part of the jet tube, and has an inlet and an outlet for fluid to pass through the heat exchange chamber in use, and a series of staggered radial baffles in the chamber defining an oscillatory and circumferential flow path for the fluid between the inlet and outlet. 
     
     
         2 . A heat exchanger as claimed in  claim 1  in which the chamber has opposite end walls and the staggered baffles comprise an alternating series of first and second baffles comprising a first series of baffles that extend from one end wall towards the opposite end wall and a second series of baffles that extend from the opposite end wall toward said one end wall. 
     
     
         3 . A heat exchanger as claimed in  claim 1  or  2  in which the baffles define an oscillatory and circumferential flow channel between and the inlet and outlet. 
     
     
         4 . A heat exchanger as claimed in  claim 1 ,  2  or  3  in which the chamber extends by up to 360° around the through bore. 
     
     
         5 . A heat exchanger as claimed in any one of  claims 1  to  4  in which the heat exchanger includes an aperture opening into the through bore which serves as a fluid pick up point for a secondary coolant system. 
     
     
         6 . A heat exchanger as claimed in any one of  claims 1  to  5  in which the baffles are parallel to one another and extend parallel to the through bore axis. 
     
     
         7 . A jet pump assembly for a water craft, the jet pump assembly comprising a housing having a through bore accommodating a pump impeller and a heat exchanger according to any of  claims 1  to  6 . 
     
     
         8 . A water jet propelled water craft having an engine driven pump impeller disposed in a jet tube and a heat exchanger according to any of  claims 1  to  6 . 
     
     
         9 . A heat exchanger constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings of  FIGS. 3 ,  4  and  5  when modified to exclude the pump impeller. 
     
     
         10 . A jet pump assembly constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings of  FIGS. 3 ,  4  and  5 . 
     
     
         11 . A water jet propelled water craft constructed and arranged substantially as hereinbefore described with reference to the accompanying drawing of  FIG. 2  or as modified according to  FIGS. 3 ,  4  and  5 . 
     
     
         12 . The water jet propelled watercraft of  claim 8 , wherein the water craft is a RIB, comprising a rigid hull portion and an inflatable tube extending around the rigid hull portion to form gunwales. 
     
     
         13 . The water jet propelled watercraft of  claim 8  or  claim 12 , comprising an internatl combustion engine operatively connected to a pump impeller located within the jet tube, the engine comprising a liquid-cooled engine comprising a pump adapted to circulate engine coolant through the heat exchanger. 
     
     
         14 . The water jet propelled watercraft of  claim 13 , wherein the pump is adapted to circulate coolant through a closed coolant circuit. 
     
     
         15 . The water jet propelled watercraft of  claims 12 ,  13 , and  14 , therein the RIB comprises a central passenger area and a main deck upon which users can stand or upon which cargo can be placed, and wherein the jet tube is located below the main deck and comprises a sea water inlet and an outlet. 
     
     
         16 . The water jet propelled watercraft of  claims 12  to  15 , wherein the internal combustion engine is mounted in the hull and comprises a prop shaft configured to drives a pump impeller mounted for rotation within the jet tube. 
     
     
         17 . The water jet propelled watercraft of  claim 15  or  16 , further comprising a steering nozzle located downstream of the outlet end of the jet tube.