A plate heat exchanger includes a number of first heat exchanger plates (A) and second heat exchanger plates (B). The plates include a first plate interspace (1) between each pair of adjacent plates (A) and (B), and a second plate interspace (2) between each pair of adjacent plates (B) and (A). The first and second plate interspaces are separated from each other and provided beside each other in an alternating order. The heat exchanger plates have a porthole, which forms an inlet channel (6) to the first plate interspaces. The plate heat exchanger includes a separate space (11) for each plate interspace. The space (11) is closed to the second plate interspaces. The space (11) communicates with the inlet channel via an inlet nozzle (13), which forms a throttling, and with the respective first plate interspace via an outlet nozzle (14), which forms a throttling.