plate heat exchangers

PCT No. PCT/SE96/00701 Sec. 371 Date Apr. 4, 1998 Sec. 102(e) Date Apr. 4, 1998 PCT Filed May 30, 1996 PCT Pub. No. WO97/00415 PCT Pub. Date Jan. 3, 1997In a plate heat exchanger the plate interspaces form first flow passages (13, 15; 15a) for a first fluid and other flow passages (14) for a second fluid. The plates have openings which for one of the fluids form one inlet channel (10) and one outlet channel (10a) through the plate package, the channels communicating with each other through the first flow passages (13, 15; 15a). A by-pass passage (15; 15a) is formed by at least one of the first flow passages and gives a through flow resistance that is substantially smaller than that given by each one of the other (13) first flow passages. In the inlet channel (10) or the outlet channel (10a), or in both channels, a valve member (17; 18; 26) is arranged for setting of a desired flow through the by-pass passage (15; 15a).