plattfoeraangare daer aatminstone one plate in a foeraangningspassage aer divided into faelt arranged next to each other between the plate laangsidor, which faelt exhibit mutually different korrugeringsmoenster saa to stroemningsmotstaandet gradually reduces fraan one side to the other

摘要

PCT No. PCT/SE91/00303 Sec. 371 Date Sep. 16, 1991 Sec. 102(e) Date Sep. 16, 1991 PCT Filed Apr. 29, 1991 PCT Pub. No. WO91/17406 PCT Pub. Date Nov. 14, 1991.In a plate heat exchanger for climbing film evaporating of a fluid, vertically arranged heat transfer plates (1, 2) delimit evaporating passages (4) and condensating passages (7) between themselves. Each evaporating passage (4) has a fluid inlet (5) at its lower portion and an outlet (6) for concentrated fluid and generated vapor at its upper portion, which outlet (6) is located at one vertical side of the heat transfer plates. To provide a desired distribution of the fluid and the vapor in each of the evaporating passages (4), at least alternate heat transfer plate (1), in its lower portion (17A) closest to the inlet (5) for fluid, has been provided with a number of zones (23A-26A), having different pressing pattern of corrugation ridges and grooves. The corrugation ridges and grooves form different angles to the main flow direction of the fluid in the evaporating passages (4), which angles are chosen such that the ridges and grooves of the heat transfer plates (1, 2), according to their different directions, cooperate to provide in each evaporating passage a flow resistance for the fluid in its main flow direction, which gradually decreases from said ones vertical sides to the other vertical sides of the heat transfer plates (1, 2), The varying flow resistance laterally to the evaporating passages (4) is preferably concentrated to the lower portion of the evaporating passages.