Plate heat exchanger and heat pump apparatus

A heat pump apparatus comprising:

• a refrigerant circuit including a compressor, a first heat exchanger, an expansion mechanism, and a second heat exchanger that are connected with pipes,
• wherein the first heat exchanger included in the refrigerant circuit is
• a plate heat exchanger including a plurality of plates each having, at four corners thereof, respective passage holes each serving as an inlet or an outlet for a first fluid or a second fluid, the plates being stacked such that first passages each defined by adjacent two of the plates and through which the first fluid flows and second passages each defined by adjacent two of the plates and through which the second fluid flows are provided alternately in a stacking direction,
• wherein the first passage allows the first fluid having flowed therein from an inlet as one of the passage holes that is provided on one side of each of the plates in a long-side direction to be discharged from an outlet as one of the passage holes that is provided on the other side of the plate in the long-side direction,
• wherein the first passage includes a heat-exchanging passage provided between the inlet and the outlet and in which the second fluid that flows through the second passage adjacent to the first passage and the first fluid exchange heat therebetween,
• wherein the first passage includes an upstream-side bypass passage extending-along an upstream-side adjacent hole, which is another one of the passage holes that is provided on the one side in the long-side direction and is different from the inlet,
• wherein the upstream-side bypass passage is connected to the heat-exchanging passage from an inlet peripheral portion, which is an area around the inlet to a long-side-peripheral portion, which is an area around a long side of the plate that is nearer to-the upstream-side adjacent hole,
• wherein the upstream-side bypass passage allows some of the first fluid having flowed therein from the inlet to flow from the long-side-peripheral portion into the heat-exchanging passage,
• wherein the upstream-side bypass passage flows around an arc which directs the flow downward and then upward, wherein the arc is greater than 90°, and
• wherein the upstream-side bypass passage has a cross-sectional passage area that is reduced toward the long-side-peripheral portion.