Plate heat exchanger and water heater including same
A plate heat exchanger includes a plurality of plates stacked so that a liquid flow passage is formed on the inside thereof, and a gas flow passage through which heating gas passes, the gas flow passage being formed between the plurality of plates and including a gas inflow opening portion and a gas outflow opening portion positioned on an opposite side to the gas inflow opening portion, wherein the gas outflow opening portion has a smaller opening area than the gas inflow opening portion. Thus, when the heating gas passes through the gas flow passage, even if the volumetric flow thereof decreases due to a reduction in temperature or condensation, a reduction in the flow velocity of the heating gas can be suppressed. Hence, a reduction in a heat transfer coefficient can be suppressed, leading to an improvement in heat transfer efficiency, and as a result, reductions in overall size, weight, and manufacturing cost can be achieved appropriately.
1. A plate heat exchanger comprising:
a plurality of plates stacked so that a liquid flow passage is formed on the inside thereof; and
a gas flow passage through which heating gas passes, the gas flow passage being formed between the plurality of plates and including a gas inflow opening portion and a gas outflow opening portion positioned on an opposite side to the gas inflow opening portion, wherein
the gas outflow opening portion has a smaller opening area than the gas inflow opening portion,
each of the plates has a smaller width on the gas outflow opening portion side than the gas inflow opening portion side,
each of the plates is provided in an upright attitude in an up-down height direction,
an inflow port of the liquid flow passage is provided in a lower portion of each of the plates adjacent to a first side end portion in a width direction, while an outflow port of the liquid flow passage is provided in an upper portion of each of the plates adjacent to a second side end portion, the second side end portion opposing the first side end portion in the width direction,
the first side end portion of each of the plates extends in an up-down height direction and is not inclined,
the second side end portion of each of the plates is inclined to a position where the second side end portion of each of the plates meets a lower end portion of each of the plates,
a first distance, in the width direction, between the position where the second side end portion of each of the plates meets the lower end portion of each of the plates and a center of the lower end portion of each of the plates is smaller than a second distance, in the width direction, between an outermost edge of the second side end portion of each of the plates and the center of the lower end portion of each of the plates, and
the first distance is smaller than a third distance, in the width direction, between the outflow port and the center of the lower end portion of each of the plates.
2. The plate heat exchanger according to claim 1 , wherein
an upper end portion of each of the plates is inclined so that the second side end portion has a greater height than the first side end portion.
3. The plate heat exchanger according to claim 1 , wherein
an upper end portion and the lower end portion of each of the plates are positioned respectively on an upstream side and a downstream side in a heating gas flow direction, and
the liquid flow passage includes a first region that surrounds the inflow port and a first flow passage that extends linearly from the first region toward the upper end portion of the plate.
4. The plate heat exchanger according to claim 1 , wherein
the liquid flow passage includes a second region that surrounds the outflow port and a second flow passage that extends linearly from the second region toward the lower end portion of the plate.
5. The plate heat exchanger according to claim 1 , wherein
outer peripheral end portions of the plurality of plates opposing each other on opposite sides of the gas flow passage are bonded to each other except in regions of the gas inflow opening portion and the gas outflow opening portion.
6. The plate heat exchanger according to claim 1 , wherein
adjacent plates, among the plurality of plates, are brazed to each other, whereas regions near the center of plates that oppose each other on opposite sides of the gas flow passage are not brazed and therefore remain in a non-bonded state.
7. The plate heat exchanger according to claim 1 , further comprising:
a flow-straightening member that covers a region of the outer periphery of the plurality of plates excluding the gas inflow opening portion and the gas outflow opening portion and prescribes respective opening widths of the gas inflow opening portion and the gas outflow opening portion.
8. The plate heat exchanger according to claim 1 , wherein
a plurality of gas flow passages are provided as the gas flow passage, and
the gas outflow opening portion of each of the gas flow passages has a narrower width than the gas inflow opening portion.
9. A water heater comprising:
the plate heat exchanger according to claim 1 .
10. The water heater according to claim 9 , further comprising:
an exhaust gas guide member that is connected to a downstream side of the plate heat exchanger in a heating gas flow direction in order to cause heating gas that has passed through the plate heat exchanger to flow in a first direction, a vector of the first direction intersects a vector of the heating gas flow direction through the plate heat exchanger, wherein
the plate heat exchanger is set so that a stacking direction of the plurality of plates corresponds to a second direction, and a vector of the second direction intersects the vector of the first direction.