Outer shell structure for a heat exchanger

An outer shell structure for a heat exchanger, with which a heat exchange unit having a plurality of heat exchange plates formed of a square or rectangular metallic plate is surrounded, said heat exchange plates being placed in parallel with each other so that there are repeated a first connecting relationship in which external surfaces of adjacent two heat exchange plates face each other and welded together at a first pair of side edges thereof over an entire length thereof to form a first gap portion therebetween and a second connecting relationship in which internal surfaces of other adjacent two heat exchange plates face each other and welded together at a second pair of side edges thereof rectangular to said first pair of side edges over an entire length thereof excepting welded portions of the first pair of side edges to form a second gap portion therebetween, so as to provide a combined body for the heat exchange unit, having a pair of first opposite planes that are in parallel with the heat exchange plates, a pair of second opposite planes that are placed on opening sides of said first gap portion and a pair of third opposite planes that are placed on opening sides of said second gap portion, said outer shell structure ensuring separate flow of a first heat exchange fluid flowing through said first gap portion and a second heat exchange fluid flowing through said second gap portion and preventing external leakage of the first and second heat exchange fluids, said outer shell structure comprising:

• a pair of opposite end walls placed on the pair of first opposite planes of the heat exchange unit, respectively, so as to cover the pair of first opposite planes thereof;
• a pair of opposite first walls with an opening placed outside apart from the pair of second opposite planes of the heat exchange unit, respectively, said first walls being connected water-tightly to edges of said end walls so as to isolate an opening of said first gap portion from an outside, except for an inlet and an outlet for said first heat exchange fluid;
• a pair of opposite second walls with an opening placed outside apart from the pair of third opposite planes of the heat exchange unit, respectively, said second walls being connected water-tightly to edges of said end walls so as to isolate an opening of said second gap portion from the outside, except for an inlet and an outlet for said second heat exchange fluid;
• one or more gap closure members for closing a gap between said second walls and said heat exchange unit, other than regions of the inlet and outlet for the second heat exchange fluid, to prevent the heat exchange fluid from flowing in a direction along which the gap portion extends, in parallel with a side of the heat exchange plates;
• four sets of corner ridge members welded to the opposite end walls and the heat exchange plates, each of said corner ridge members comprising an outer plate section and an inner plate section, each of said outer and inner plate sections being provided at a longitudinal side thereof with a serration portion having serrations that are formed at same intervals as the heat exchange plates aligned with a same orientation of said plurality of heat exchange plates, said serration portion of said outer plate section being inserted into gaps between a plural pairs of heat exchange plates that are welded together at said first pair of side edges thereof over the entire length thereof, of said heat exchange unit, and said serration portion of said inner plate section being inserted into the openings of the first gap portions by a predetermined length;
• and
• said end walls being connected water-tightly to opposite end portions of each of said corner ridge members in a direction along which the heat exchange plates are placed.