Plate type heat exchanger tube pass

In an elongated heat exchanger single tube pass formed by a pair of plates with edge portions joined together and midportions spaced apart to form a fluid enclosure for single pass flow therebetween and wherein opposite ends of the plates have outward offsets from the plane of the midportions to define inlet and outlet manifold enclosures and to form offset surfaces on adjacent tube passes for engagement together when in stacked relation to form airflow passages between adjacent midportions of the tube passes, the improvement comprising:

• a plurality of transverse rows of separated ribs formed in the midportion of each plate and extending transversely substantially the width thereof and with the ribs in each transverse row angled obliquely to the length and width thereof, the ribs in each transverse row being unconnected with each other and overlapping and staggered with respect to the ribs in the same row and to ribs in the adjacent row and spaced from the edge portions of the plate so as to prevent a direct linear flow path across all the transverse rows while forming uninterrupted by-pass flow paths past the ends thereof between the inlet and outlet enclosures, alternate ones of the transverse rows having two centrally located partial length ribs which form a linear flow path therebetween through these rows that is interrupted by the ribs in the other rows to thereby form an interrupted linear flow path centrally across the transverse rows between the inlet and outlet enclosures, and the angled ribs of one plate extending across the corresponding and adjacent angled ribs of the other plate of the tube pass to form multiple contacts and thus provide a tortuous flow path over and around the ribbed surfaces and contact points therebetween wherein the centrally located interrupted linear flow path between the inlet and outlet enclosures forces fluid distribution across the transverse rows while providing interrupted linear flow thereacross to improve the heat transfer efficiency of the tube pass while cooperating with the by-pass flow paths to minimize the pressure drop therein.