JPH062944A - By-pass mixing type hot water supplying apparatus - Google Patents

Abstract

PURPOSE:To prevent inconvenience of temporary flow-out of chilled water from a faucet at the time of resupplying hot water immediately after stopping of supplying hot water. CONSTITUTION:A by-pass mixing type hot water supplying apparatus comprises a water passage 1 connected to a place to be supplied with hot water, a heat exchanger 2 arranged at the passage 1, and a by-pass circuit 3 for connecting an upper passage of the exchanger 2 to a lower passage of the exchanger 2 at the passage 1 and formed under the exchanger 2, and mixes chilled water from the circuit 3 to warm water heated by the exchanger 2 to output warm water of a desired temperature. A confluent point 31 of the passage 1 and a branch point 32 of the circuit 3 to be disposed at a downstream side of the point 32 is set in height to higher than the point 32 in the apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater, and more particularly to a bypass mixing type water heater, which is intended to prevent the inconvenience of the temporary outflow of cold water from the faucet when the hot water is again discharged immediately after the hot water is stopped.

[0002]

2. Description of the Related Art By-pass mixing method capable of immediately taking out hot water of a desired temperature by preventing a boil-off phenomenon in which hot water temporarily flows out and a so-called cold water sand phenomenon in which cold water flows out at the time of re-melting immediately after the hot water is stopped Schematic of the water heater
It has the structure shown in. A heat exchanger equipped with heat absorption fins (20) for absorbing the heat generated by the gas burner (6) in the water passage (1).
(2), hot water supply temperature sensor (21) and further faucet (22) are arranged in this order in the downstream side, and the upstream side of the heat exchanger (2) in the water passage (1). And the bypass circuit on the downstream side (3)
Are connected by.

At the branch point (32) between the bypass circuit (3) and the water passage (1), a distributor (4) for controlling the distribution ratio of the feed water to the heat exchanger (2) and the bypass circuit (3). ) Is inserted, and the operation of the distributor (4) is controlled by the control circuit (5) that determines the output of the hot water temperature sensor (21) and the hot water temperature setting device (41). In this case, when the tap (22) is opened and hot water is discharged, a water flow switch (not shown) detects the water flow in the water passage (1) at this time and the gas burner (6)
Is burned, whereby high-temperature water (generally, hot water having a temperature about 55 deg higher than the supply water temperature) is boiled in the heat exchanger (2) portion to start the hot water supply operation.

When hot water, which is a mixture of high-temperature water generated in the heat exchanger (2) and cold water from the bypass circuit (3), flows to the hot water supply temperature sensor (21) on the downstream side, the hot water temperature The control circuit (5) determines the temperature detected by the sensor (21) and the set temperature of the hot water temperature setting device (41), and the control circuit (5) sets the hot water temperature sensor (21) to detect the hot water temperature. The distribution ratio of the feed water to the heat exchanger (2) and the bypass circuit (3) is adjusted while controlling the distributor (4) so that it becomes equal to the set temperature of the device (41). That is, the water passage (1) on the downstream side of the heat exchanger (2) and the bypass circuit.
By adjusting the mixing ratio of the cold water from the bypass circuit (3) supplied to the confluence point (31) with the hot water (2) from the heat exchanger (2), the hot water temperature sensor (21) The hot water temperature detected by) is made equal to the set temperature of the hot water temperature setting device (41).

In this case, a so-called post-boiling phenomenon occurs when hot water is stopped with the faucet (22) closed, and a water passage in the heat exchanger (2) portion is generated.
(1) Even if hot water may stay inside, hot water due to the post-boiling phenomenon is mixed with the hot water due to the post-boiling phenomenon, so that the hot water due to the post-boiling phenomenon remains unchanged. It is possible to prevent the inconvenience from flowing out from the faucet (22). In addition, the amount of cold water that does not enter the heat exchanger (2) and is not heated before the start of combustion of the gas burner (6) at the time of re-hot water can be suppressed, and the so-called cold water sand phenomenon is prevented, so It is possible to prevent the inconvenience from flowing out from the faucet (22).

However, the above-mentioned conventional one has a problem in that if hot water is again tapped immediately after the hot water is stopped, cold water will flow out from the faucet (22) for a reason other than the cold water sand. This problem occurs because the cold water in the bypass circuit (3) flows backward from the confluence point (31) toward the heat exchanger (2) when hot water is stopped.

The above problems will be described in more detail. Regarding the water temperature in the water passage (1) during the hot water discharge operation, the temperature of the downstream side of the heat exchanger (2) is higher than the temperature of the cold water in the upstream side and in the bypass circuit (3). Therefore, branch point (32) of water passage (1) and bypass circuit (3) → heat exchanger (2) → confluence point
(31) → Bypass circuit (3) → Focusing on the loop-shaped closed circuit (12) connected to the branch point (32), the boundary between hot water heated in the heat exchanger (2) and cold water not heated There are two points (hereinafter referred to as temperature boundary points). That is, one temperature boundary point (B) exists at the confluence point (31) and the other temperature boundary point (A) exists at the heat absorption inlet (23) of the heat exchanger (2). Therefore, when tapping is stopped, the above temperature boundary points (A) (B)
The cold water and hot water in the closed circuit (12) separated by the boundary flow so as to rotate in the closed circuit (12) as a whole due to the specific gravity difference between the cold water and the hot water, whereby the boundary point (A) Stabilizes when (B) is at the same height. That is, since the cold water in the bypass circuit (3) existing up to the confluence point (31) at the moment when the tapping is stopped, flows back to the heat exchanger (2) side after the tapping is stopped and stabilizes at a predetermined height. is there. Then, this stable point (35)
Cold water is retained in the water passage (1) from the above to the confluence point (31), and when the faucet (22) is reopened, the cold water is mixed with the cold water from the bypass circuit (3). Faucet (22)
The hot water of the desired temperature cannot be taken out.

In the above-mentioned conventional one, the mixing ratio of the hot water from the heat exchanger (2) and the cold water from the bypass circuit (3) is adjusted by utilizing the distributor (4). Even if a temperature sensitive pellet type regulating valve is inserted at the confluence point (31) to adjust the mixing ratio of the hot water and the cold water, the same problem as described above occurs. [Invention of Claim 1] The invention of Claim 1 is made in view of the above-mentioned point.
(1), the heat exchanger (2) arranged in the water passage (1) and the upper and lower flow passages of the heat exchanger (2) in the water passage (1) are connected. Further, a bypass circuit (3) formed below the heat exchanger (2) is provided, and hot water boiled in the heat exchanger (2) is mixed with cold water from the bypass circuit (3) to obtain a desired temperature. It is an object of the present invention to prevent inconvenience that cold water flows out when hot water is discharged again after the hot water is stopped in a “bypass mixing type water heater for taking hot water”.

[0009]

[Technical Means] To solve the above-mentioned problems, the technical means of the invention of claim 1 is that "a heat exchanger (2), a bypass circuit (3) for bypassing the heat exchanger (2), and a water passage (1) connecting them are provided. Of the two paths formed by connecting the highest position b and the lowest position a of the looped closed circuit (12) to the left and right, the left side is the first water passage and the right side is the second water passage, and when hot water is stopped, Any height y1, y in the first and second water passages
The specific gravities of the accumulated water in 2 are ρ1 and ρ2, the vertical heights of the channels are dy1 and dy2, respectively, and the integration range is from the height of the lowest position a to the height of the highest position b. When set, the height of the confluence point (31) of the downstream water passage of the heat exchanger (2) and the bypass circuit (3) is selected so that ∫ρ1 dy1 and ∫ρ2 dy2 are almost equal. ” is there.

[0010]

The above technical means operates as follows. A closed loop circuit formed by a heat exchanger (2), a bypass circuit (3) that bypasses the heat exchanger (2), and a water passage (1) that connects them.
In the inside of (12), the temperature distribution at the moment when the tapping is stopped is uneven due to its height. That is, at the moment the hot water is stopped, the upper heat exchanger (2) is at a higher temperature than the accumulated water in the water passage (1) and the bypass circuit (3) located below it. .

Therefore, the specific gravity of the accumulated water depending on the water temperature is not constant due to the height of each part in the closed circuit (12). However, according to the above technical means, the downstream water passage of the heat exchanger (2) and the bypass circuit (3) are merged so that ∫ρ1 dy1 = ∫ρ2 dy2 (A) when the hot water is stopped. The height of the point is set.

However, the integration on the left side is the integration along the first water passage on the left side of the path formed on the left and right by connecting the highest position b and the lowest position a of the closed circuit (12), and the right side is the right side. Is an integral along the second waterway of Further, ρ1 and ρ2 in the above equation (A) are specific gravities of water at arbitrary heights y1 and y2 in the first water passage and the second water passage at the moment when the hot water is stopped.

Therefore, the value obtained by multiplying each side of the above equation (A) by the acceleration G of gravity is the lowest position of each water passage (closed circuit (12)) due to the accumulated water in the first and second water passages. It indicates the water pressure generated at the lowest position a). Since this water pressure is the same in the first and second water passages, the water existing at the lowest position a of the closed circuit (12) when the hot water is stopped is discharged to either of the first and second water passages. Also keeps stopped without flowing. That is, the closed circuit (12) when the hot water is stopped
The water inside does not totally rotate in any direction within the closed circuit (12), and the whole state is stopped.

Therefore, when the hot water is stopped, the cold water in the bypass circuit (3) does not flow backward toward the heat exchanger (2) side, and the cold water stays in the water passage downstream of the heat exchanger (2). There is no such thing.

[0015]

The invention of claim 1 has the following unique effect. Since cold water does not stay in the water passage (1) on the downstream side of the heat exchanger (2) when the hot water is stopped, it is possible to prevent the inconvenience that the cold water is sent to the hot water supply place even if the hot water is again discharged after that.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the invention of claim 1 will be described in detail with reference to the drawings. As shown in Fig. 1, the water flow path (1) is connected to the water flow switch (15) and the water temperature sensor (1) from the upstream side.
6), distributor (4), heat exchanger (2), heat exchanger sensor (17) for detecting the temperature of hot water boiled in the heat exchanger (2), hot water supply temperature sensor (21) and faucet (22) ) Are arranged in this order.

The water passage (1) on the downstream side of the distributor (4) is wound around the outer circumference of the can body (25) for the heat exchanger (2) and then the heat exchanger (2).
The endothermic fin (20) located above (2) is penetrated in a meandering state. A gas valve (61) is inserted in the gas circuit (60) to the gas burner (6) that heats the heat exchanger (2), and
The electric components such as the gas valve (61) and the water flow switch (15) described above are connected to the control circuit (5) together with the hot water temperature setting device (41) for setting the hot water temperature. In addition, the heat exchange sensor (17) and hot water temperature sensor installed in the water passage (1) on the downstream side of the heat exchanger (2).
Between the (21) and the distributor (4) above is the bypass circuit (3)
Are connected by.

Next, a confluence point (31) between the water passage between the heat exchange sensor (17) and the hot water supply temperature sensor (21) and the bypass circuit (3).
The height position of will be described. Heat exchanger (2), bypass circuit (3) for bypassing it, and water passage (1) connecting them
The first water passage is on the left side of the two paths formed on the left and right by connecting the highest position b and the lowest position a of the closed circuit (12) constituted by
The right side is the second waterway. For example, in FIG. 1, from the highest position b near the outlet of the heat exchanger (2), through the water passage (1), from the confluence point (31) to the lowest position a via the bypass circuit (3).
The left water passage connected to the distributor (4) is the first water passage, and the right water passage on the opposite side is the second water passage. Then, the specific gravity of the accumulated water at arbitrary heights y1 and y2 in the first water passage and the second water passage at the moment when the hot water is stopped is set to ρ1 and ρ2, respectively, and the water passage in that portion is set. If the vertical heights of are set to dy1 and dy2, respectively, and the integration range is set from the height of the lowest position a to the height of the highest position b, then ∫ρ1 dy1 and ∫ρ2 dy2 will be equal. , Set the height of the confluence point (31) of the downstream water passage of the heat exchanger (2) and the bypass circuit (3).

In FIG. 1, the portion of the distributor (4) is set to the lowest position a. However, for example, when the bypass circuit (3) is curved downward, the lowest point of the curved portion is the lowest position. a. Needless to say, the same modification can be considered for the highest position b. Confluence point for equalizing the two integrated values corresponding to the first water passage and the second water passage
The height of (31) is the integral equation “∫ρ1 dy1 = ∫ρ2 dy2” under the above conditions after obtaining the temperature distribution in the heat exchanger (2).
Can be found by solving, but it can also be found by experiments.

That is, a test flow meter is inserted in the bypass circuit (3), and when the faucet (22) is closed, the flow rate measured by the flow meter is maintained at "0". Adjust the height of. That is, an experiment is repeated by repeatedly bending the pipe for the water passage (1) to adjust the height of the confluence point (31) and stopping the tapping to keep the flow meter at "0". Of. As a result, ∫ρ1 dy1 and ∫ρ2 d
We can find the height of the confluence point (31) to make y2 equal.

Next, the hot water supply operation of the water heater will be described. When the faucet (22) is opened by setting the temperature with the hot water temperature setting device (41), the water flow switch (15) is turned on by the water flow generated at this time.
A signal is emitted, which drives an ignition device (not shown) to ignite the gas burner (6). Next, the opening of the gas valve (61) is adjusted so that the difference between the incoming water temperature detected by the incoming water temperature sensor (16) and the temperature detected by the heat exchange sensor (17) becomes a constant temperature (55 deg in this embodiment). To control the combustion amount of the gas burner (6).

Thereafter, the distributor (4) is the same as the conventional one described above.
Control the hot water temperature sensor (21) and the hot water temperature setting device (4
Adjust the distribution ratio of the amount of water supplied to the bypass circuit (3) and the heat exchanger (2) so that the set temperatures of (1) are the same, so that the hot water at the temperature set by the hot water temperature setter (41) is adjusted. Is supplied to the faucet (22). Next, when the faucet (22) is closed, the gas burner (6) is extinguished and hot water of a predetermined temperature is retained in the water passage (1) of the heat exchanger (2).

In the above water heater, when the hot water is stopped,
The value of "∫ρ2 dy2" in the second waterway from the distributor (4) to the top of the heat exchanger (2) and the heat exchanger (2) → confluence (31) → bypass circuit ( 3) → 1st connected with distributor (4)
The height of the confluence point (31) is set so that the value of "∫ρ1dy1" in the water passage becomes equal. Therefore,
The water pressures acting on the respective lowest positions of the first and second water passages (corresponding to the lowest position a of the closed circuit (12)) become equal,
There is no water flow in the closed circuit (12). That is,
Cold water in the bypass circuit (3) flows from the confluence (31) to the heat exchanger
The phenomenon of backflow to the (2) side does not occur. [Claim 2 Regarding Invention]

[0024]

[Technical Means] The invention according to claim 2 solves the same problem as that of the invention according to claim 1 and is adopted for that purpose.
The technical means of the invention of 'is the "bypass circuit (3) and heat exchanger".
The height of the confluence point (31) where the downstream water passage (1) of (2) merges is set to be approximately the same height as the inlet of the heat exchanger (2). "
That is.

[0025]

[Operations and effects] According to the above technical means, the heat exchanger (2)
The hot water generated by the heat exchanger (2) accumulates in the water passage from the inlet of the heat exchanger (2) to the confluence point (31), and the confluence point (31) → bypass circuit (3) → Waterway (1)
→ Cold water that is not heated by the heat exchanger (2) stays in the water passage connecting to the inlet. Then, at the confluence point (3
Since 1) is set to almost the same height, the heat exchanger (2) and a bypass circuit that bypasses this when the hot water supply is stopped.
Hot water with a small specific gravity stays in the upper part of the closed circuit (12) composed of the water passage (1) connecting with (3) (the area above the horizontal line connecting the inlet and the confluence point (31)), In the following region, cold water with a large specific gravity stays in a mechanically stable state.
Therefore, when hot water is stopped, there is no flow of water in the closed circuit (12), and cold water in the bypass circuit (3) flows backward from the confluence point (31) to the heat exchanger (2) side. Absent. Therefore, there is no inconvenience that cold water is supplied to the downstream side when tapping again after tapping. [Invention of Claim 3]

[0026]

[Technical Means] The invention of claim 3 solves the same problem as the inventions of claims 1 and 2, and the technical means of the invention of claim 3 adopted for that purpose is to 1) is the height position of the most upstream part S of the region where the heat absorbing fin (20) for the heat exchanger (2) penetrates, the bypass circuit (3) and the water passage (1)
The height positions of the confluence points (31) at which the merging points are substantially matched with each other.

[0027]

[Operation / Effect] The above technical means has the following operation / effect. The water in the water passage (1) flows through the heat-absorbing fins (2
When passing through the 0) portion, the temperature is raised by heating. Therefore,
When the hot water operation is stopped, the water passage (1) is
Heat exchanger (2) from the most upstream part S of the area penetrating (20)
The hot water that has been heated and heated accumulates in the water passage that passes through the flow path and reaches the confluence point (31), and the closed circuit (1
Cold water having a temperature lower than that of the above high temperature water stays in 2).

Since the uppermost stream portion S and the confluence point (31) are set at substantially the same height, the heat exchanger (2) and the bypass circuit (3) bypassing the heat exchanger (2) at the moment when the tapping is stopped. Hot water with a small specific gravity is located in the upper part of the closed circuit (12) (the area above the horizon that passes through the confluence point (31)) that is composed of the water passage (1) that connects them, and in the area below that. Cold water with a large specific gravity is accumulated. Therefore, when the hot water is stopped, the accumulated water in the closed circuit (12) does not flow so as to rotate as a whole in the closed circuit (12), and the cold water in the bypass circuit (3) flows from the confluence point (31). There is no inconvenience of backflow to the heat exchanger (2) side. Therefore, cold water is not supplied to the downstream side when the hot water is re-poured.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment corresponding to the inventions of claims 2 and 3 will be described with reference to FIG. In this embodiment, the height position of the most upstream portion S in the region where the water passage (1) penetrates the heat absorbing fins (20) of the heat exchanger (2) and the bypass circuit
It is constructed in the same manner as the embodiment of the invention described in claim 1 except that the height positions of the confluence point (31) of the water passage (1) and (3) are matched.

In this case, most of the heat generated in the gas burner (6) is transferred to the water in the water passage (1) at the heat absorbing fins (20). Therefore, when the faucet (22) is closed,
The heat exchanger (2) is used for the inside of the closed circuit (12) above the horizontal line (R) connecting the uppermost stream part S of the area where (1) penetrates the heat absorbing fins (20) and the confluence point (31). High temperature water generated by heating stays,
In the closed circuit (12) at a position lower than the horizontal line (R) (confluence point (31)
→ Bypass circuit (3) → Distributor (4) → Cooling water that is not heated stays in the water passage connected to the heat absorption fins (20) and becomes a mechanically stable state. Therefore, when hot water is stopped with the faucet (22) closed, the cold water in the bypass circuit (3) is confluent (3
There will be no backflow from 1) to the heat exchanger (2) side. Therefore, it is possible to prevent the inconvenience that cold water flows out from the faucet (22) when the faucet (22) is reopened.

In the above, the water passage wound around the can body (25) for the heat exchanger (2) upstream of the heat absorbing fins (20).
Considering that the temperature of (1) is almost not heated and raised,
The water passing through the portion was treated as cold water, and the height position of the uppermost stream portion S and the height of the confluence point (31) were matched. However, the temperature rise of the water flowing through the wound water passage (1) may be about 10% of the whole depending on the degree of close contact with the can body (25) and the winding length. Considering the temperature, the pressure on the side of the second water passage becomes small, and there is a risk that the hot water boiled in the heat exchanger (2) will slightly enter the bypass circuit (3) from the confluence point (31) when the hot water is stopped. is there. Therefore, in order to prevent this, the height of the confluence point (31) may be set slightly lower than the height of the uppermost stream portion S.

When the inlet / outlet of the water passage (1) penetrating the heat absorbing fins (20) in the heat exchanger (2) has a width in the height direction (when the inlet / outlet has a height difference), the inlet When considering the temperature gradient from the outlet to the outlet, if the heights are matched as described above, the pressure on the side of the second water passage increases. Therefore, the cold water in the bypass circuit (3) may slightly flow back from the confluence point (31) to the heat exchanger (2) side. Therefore, in order to prevent this, the height of the confluence point (31) may be set to be slightly higher than the height position of the uppermost stream portion S.

Then, as described above, the temperature rise amount of the water passage (1) part wound around the can body (25) of the heat exchanger (2) and the temperature gradient of the part penetrating the heat absorbing fins (20) are set. The height of the confluence point (31) set in consideration (a region having a width slightly in the vertical direction from the uppermost stream portion S) corresponds to the "inlet portion" described in claim 2. As shown in FIG. 3, if the coil (99) is inserted on the downstream side of the confluence point, the hot water and the cold water that confluence at the confluence point (31) will be agitated when passing through this part to ensure the mixing. It is possible to prevent erroneous detection by the hot water supply temperature sensor (21).

Further, if the water passage (1) in the portion where the coil (99) is inserted is bent, the water flow is further disturbed, so that the cold water and the hot water can be mixed more reliably. It should be noted that the coil (99) is improved in mixing degree when it is inserted at a long distance in the water passage (1). Therefore, as in the present invention,
If (31) is set near the end of the heat exchanger (2) where the heat absorbing fins (20) are installed, a relatively long distance between the confluence point (31) and the hot water temperature sensor (21) can be obtained without increasing the size of the water heater. Therefore, it is possible to perform mixing using a long coil without increasing the size of the water heater.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the invention of claim 1.

FIG. 2 is an explanatory diagram of an embodiment of the invention of claims 2 and 3;

[Fig. 3] Water passage between the confluence (31) and the hot water temperature sensor (21)
(1) Explanatory drawing when the coil (99) is loaded in the part

FIG. 4 is an explanatory diagram of a conventional example.

[Explanation of symbols] (1) ・ ・ Water passage (2) ・ ・ ・ Heat exchanger (3) ・ ・ ・ Bypass circuit (12) ・ ・ ・ Closed circuit (20) ・ ・ ・ Heat absorbing fin

Claims (3)

[Claims] 1. A water passage (1) connected to a hot water supply place, a heat exchanger (2) arranged in the water passage (1), and the heat exchanger (2) in the water passage (1). ) Has a bypass circuit (3) formed below the heat exchanger (2) that connects both the upper and lower flow passages to the hot water boiled in the heat exchanger (2).
In a bypass mixing type water heater that mixes cold water from (3) to extract hot water of a desired temperature, a heat exchanger (2), a bypass circuit (3) that bypasses this heat exchanger, and a water passage (1) that connects them are used. Of the two paths formed by connecting the highest position b and the lowest position a of the looped closed circuit (12) to the left and right, the left side is the first water passage and the right side is the second water passage, and when hot water is stopped, The specific gravity of the accumulated water at arbitrary heights y1 and y2 in the first water passage and the second water passage is ρ1 and
ρ2, and the vertical heights of the water channels are dy1
, Dy2, and when the integration range is set from the height of the lowest position a to the height of the highest position b, ∫ρ1 dy1
And ∫ρ2 dy2 are almost equal, heat exchanger (2)
A bypass mixing type water heater that selects the height of the confluence point (31) between the downstream water passage and the bypass circuit (3). 2. A water passage (1) connected to a hot water supply place, a heat exchanger (2) arranged in the water passage (1), and the heat exchanger (2) in the water passage (1). ) Has a bypass circuit (3) formed below the heat exchanger (2) that connects both the upper and lower flow passages to the hot water boiled in the heat exchanger (2).
In the bypass mixing type water heater that mixes the cold water from (3) to take out hot water of the desired temperature, the bypass circuit
Bypass where the height of the confluence point (31) where the (3) and the downstream water passage (1) of the heat exchanger (2) meet is set to approximately the same height as the inlet of the heat exchanger (2). Mixing type water heater. 3. A water passage (1) connected to a hot water supply place, a heat exchanger (2) arranged in the water passage (1), and the heat exchanger (2) in the water passage (1). ) Has a bypass circuit (3) formed below the heat exchanger (2) that connects both the upper and lower flow passages to the hot water boiled in the heat exchanger (2).
In a bypass mixing type water heater that mixes cold water from (3) to extract hot water of a desired temperature, the water passage (1) is located in the area where the water passage (1) penetrates the heat absorbing fins (20) for the heat exchanger (2). Height position of the most upstream part, bypass circuit (3) and heat exchanger (2)
A bypass mixing type water heater in which the height positions of the confluence points (31) where the downstream side water passages (1) of (1) meet are substantially matched.