JP4252971B2 - 1 can type combined heat source machine - Google Patents

Description

  The present invention includes a single can body, a first and second pair of burners provided side by side in the can body, and a first and second pair provided side by side on the top of the can body. The present invention relates to a single can type combined heat source apparatus including a heat exchanger.

  Conventionally, as a single can type combined heat source machine of this type, the space between the first and second burners and the first and second heat exchangers in the can is transferred from the first burner to the first heat exchange. A partition wall that divides into a first combustion chamber leading to the furnace and a second combustion chamber leading from the second burner to the second heat exchanger, and burns only one of the burners, for example, the second burner to perform the second heat exchange It is known that the problem that combustion exhaust of the second burner flows to the first heat exchanger side and the first heat exchanger is heated at the time of single operation for heating the heat exchanger can be prevented (for example, Patent Document 1). In this case, an air supply chamber partitioned by a distribution plate is defined at the lower part of the can body, and the first and second air supply holes are formed through distribution holes formed in the distribution plate by the combustion air from the combustion fan. The fuel is supplied to both combustion chambers.

By the way, when providing a partition wall in a can, the partition wall is heated by the combustion heat of each of the first and second burners and becomes extremely high, and securing the heat resistance of the partition wall becomes a problem. In the above conventional example, a part of the air flowing into each combustion chamber from the air supply chamber through the distribution hole of the distribution plate flows along the outer wall surface of the partition wall. A small amount of air flowing in from the distribution holes near the partition wall flows, and the partition wall cannot be cooled sufficiently. For this reason, it is necessary to widen the lateral interval between the partition wall and each burner to reduce the thermal influence from each burner on the partition wall, and there is a problem that the heat source machine becomes large.
Japanese Patent Publication No. 2-17784 (FIGS. 3 and 6)

In view of the above points, the present invention provides a single can type combined heat source that can ensure the heat resistance of the partition wall without widening the lateral spacing between the partition wall and each burner, and can be downsized. The challenge is to provide a machine.

In order to solve the above-mentioned problems, a single can body, a first and second pair of burners provided side by side in the can body, and a first and second side by side provided on the top of the can body, A space between the second pair of heat exchangers, the first and second burners in the can, and the first and second heat exchangers reaches from the first burner to the first heat exchanger. A partition wall that divides the first combustion chamber and the second combustion chamber from the second burner to the second heat exchanger, and defines an air supply chamber partitioned by a distribution plate at a lower portion of the can body. In a one-can type combined heat source machine in which combustion air from a combustion fan is supplied to both the first and second combustion chambers through distribution holes formed in the distribution plate , according to the present invention , the partition wall Is constituted by two plates facing each other in the lateral direction with a gap therebetween, and air from the air supply chamber is caused to flow through the gap between the two plates.

Further , according to the present invention, the air from the air supply chamber flows into the space between the two plates constituting the partition wall, that is, the internal space of the partition wall, and the partition wall is efficiently cooled from the inside. Become. Therefore, the heat resistance of the partition wall can be ensured and the heat source machine can be reduced in size without increasing the horizontal interval between the partition wall and each burner to the left.

  By the way, air column vibration is generated in the can. Here, both the first and second combustion chambers communicate with each other through both the first and second heat exchangers so as to be able to ventilate. Occurs and the natural frequency of the air column vibration is lowered. When the natural frequency of the air column vibration is lowered, the flame is likely to resonate and the combustion noise is increased. In this case, if a sealing portion is provided at the side end of each heat exchanger facing the boundary between both heat exchangers to seal the gap between the heat sink fins constituting each heat exchanger, both heat exchange Ventilation between the chambers is blocked, and communication between both combustion chambers via both heat exchangers is cut off. Further, when the partition wall is constituted by two plates as described above, both plates are brought into contact with the sealing portions of both heat exchangers at the upper end portions of both plates inserted into the boundary portion of both heat exchangers. Then, the communication between both combustion chambers through the gap between each plate and each heat exchanger is also cut off. Accordingly, the air column vibration is generated individually in each combustion chamber, and the natural frequency of the air column vibration is increased. As a result, the resonance vibration of the flame is effectively prevented and the combustion noise is reduced.

In addition, when the air blowing holes are opened in the two plates constituting the partition wall , the two combustion chambers communicate with each other via the air blowing holes and the gap between the two plates, and the air column vibration straddling both the combustion chambers is generated. appear. In this case, if an intermediate partition plate that bisects the gap between the two plates in the lateral direction from the distribution plate to the upper end of the partition wall is interposed between the two plates constituting the partition wall, the communication between the two combustion chambers is achieved. Is cut off by the partition plate. Therefore, no air column vibration straddling both combustion chambers is generated, and an increase in combustion noise due to a decrease in the natural frequency of the air column vibration can be reliably prevented.

FIG. 1 shows that a first burner 2-1 and a second burner 2-2 are arranged in a horizontal direction in a single can 1 and heated by the first burner 2-1 at the top of the can 1. 1 can type combined heat source apparatus in which a first heat exchanger 3-1 for hot water supply and a second heat exchanger 3-2 for heating heated by the second burner 2-2 are arranged side by side in the horizontal direction A reference example is shown.

  In the lower part of the can body 1, an air supply chamber 5 partitioned by a distribution plate 4 with respect to the space in the can body 1 is defined. And the combustion fan 6 connected to the air supply chamber 5 is provided, and the combustion air from the combustion fan 6 is supplied into the can 1 through the distribution holes 4 a formed in the distribution plate 4 from the air supply chamber 5. Like to do.

  Each of the burners 2-1 and 2-2 is configured by arranging a plurality of longitudinal unit burners 2 a in the horizontal direction in the depth direction of the can 1 (the direction orthogonal to the plane of FIG. 1). As shown in FIG. 2, each unit burner 2 a includes a mixing tube portion 2 b extending on the back side (rear side) of the can body 1. Then, the rear part of the distribution plate 4 is offset upward, a rising part 5a is formed at the rear part of the air supply chamber 5, and the inflow end of the mixing pipe part 2b of each unit burner 2a faces the rising part 5a. . Further, the gas manifold 2c for each burner 2-1 and 2-2 is accommodated in the rising portion 5a of the air supply chamber 5, and gas is supplied from the nozzle 2d provided in the gas manifold 2c to the mixing tube portion 2b of each unit burner 2a. Is supplied, and primary air for combustion is supplied from the air supply chamber 5 to the mixing tube portion 2b. Since hot water supply is required to have a larger heating capacity than heating, the number of unit burners 2a constituting each burner 2-1 and 2-2 is greater in the first burner 2-1.

  Each of the heat exchangers 3-1 and 3-2 includes a heat absorption fin 3a in which a large number of the heat absorption fins 3a are stacked in the depth direction of the can 1 and a meandering heat absorption tube 3b penetrating the heat absorption fins 3a. The Although not shown, an upstream water supply pipe and a downstream hot water discharge pipe are connected to the heat absorption pipe 3b of the first heat exchanger 3-1, and the first hot water tap at the downstream end of the hot water discharge pipe is opened. When water is passed through the heat exchanger 3-1, the first burner 2-1 is ignited, and hot water having a set temperature is discharged from the hot water tap. Although not shown, the heat absorption pipe 3b of the second heat exchanger 3-2 is connected to a heating circuit (not shown) such as floor heating via an outgoing pipe and a return pipe, and the second heat is supplied to the heating circuit. Heating is performed by circulating hot water through the exchanger 3-2.

  Further, in the can 1, a space between the first and second burners 2-1 and 2-2 and the first and second heat exchangers 3-1 and 3-2 is provided. The first combustion chamber 7-1 from the first burner 2-1 to the first heat exchanger 3-1 and the second combustion chamber 7-2 from the second burner 2-2 to the second heat exchanger 3-2. A partition wall 8 for partitioning is provided. Thus, the combustion exhaust from the first burner 2-1 is led to the first heat exchanger 3-1 via the first combustion chamber 7-1, and the combustion exhaust from the second burner 2-2 is sent to the second combustion chamber 7-. 2 to the second heat exchanger 3-2. The combustion exhaust heat-exchanged by the first and second heat exchangers 7-1 and 7-2 flows into the exhaust hood 9 above the heat exchangers 3-1 and 3-2 and is formed in the exhaust hood 9. It is discharged to the outside through the exhaust port 9a.

In the reference example shown in FIG. 1 , not only the space between both burners 2-1 and 2-2 and both heat exchangers 3-1 and 3-2 but also the arrangement of both burners 2-1 and 2-2. The partition wall 8 extends in the vertical direction across the distribution plate 4 from the gap at the boundary between the heat exchangers 3-1 and 3-2 so that the portion is also divided into two. On the distribution plate 4, a hollow air guide member 10 having a lateral width wider than that of the partition wall 8 is disposed in accordance with the position of the partition wall 8. In detail, the pair of side plates 10a and 10a are erected on the distribution plate 4 on both lateral sides of the partition wall 8, and the air guide member 10 is configured by the side plates 10a and 10a. Yes. And the space | gap between each side plate 10a and the partition wall 8, ie, the internal space | gap of the air guide member 10, is connected to the air supply chamber 5 via the communication hole 4b formed in the distribution plate 4. FIG. The communication hole 4b is a long hole elongated in the front-rear direction as shown in FIG. 3, and the opening area per unit area is larger than the distribution hole 4a.

  In addition, the partition wall 8 is composed of two plates 8a and 8a that are opposed to each other in the lateral direction with a space therebetween. The space between the plates 8a and 8a, that is, the internal space of the partition wall 8 is distributed to the distribution plate. The air supply chamber 5 is communicated with the air supply chamber 5 through a communication hole 4 c formed in 4. The communication hole 4b is a long hole elongated in the front-rear direction, similar to the communication hole 4b, and the opening area per unit area is larger than the distribution hole 4a.

  Thus, a relatively large amount of air is supplied from the air supply chamber 5 to the internal space of the air guide member 10, and the air blown from the upper end of the air guide member 10 moves upward along the outer wall surfaces on both sides in the lateral direction of the partition wall 8. A flowing cooling air flow a is generated, and a relatively large amount of air is supplied from the air supply chamber 5 to the internal space of the partition wall 8. Therefore, the partition wall 8 is efficiently air-cooled from inside and outside by the cooling air flow b flowing through the internal gap and the cooling air flow a flowing along the outer wall surface. Therefore, the horizontal interval between the unit burner 2a near the partition wall 8 of each of the first and second burners 2-1 and 2-2 and the partition wall 8 is narrow, and each burner 2-1 is placed on the partition wall 8. Even if the combustion heat of 2-2 becomes easy to reach, the temperature of the partition wall 8 does not increase to the left, and heat resistance is ensured. Thus, since the horizontal direction space | interval between each burner 2-1 and 2-2 and the partition wall 8 can be narrowed, size reduction of a heat source machine can be achieved.

  If the air guide member 10 extends above the upper ends of the burners 2-1 and 2-2, the combustion heat of the burners 2-1 and 2-2 reaches the air guide member 10. It becomes difficult to ensure the heat resistance of the. If the height of the upper end of the air guide member 10 is lower than the upper ends of the burners 2-1, 2-2, a part of the air blown from the upper end of the air guide member 10 is burned. The amount of cooling air that flows to the −2 side and is used as secondary air for combustion and flows along the outer wall surface of the partition wall 8 decreases. Therefore, in the present embodiment, the height of the upper end of the air guide member 10 is set to each of the burners 2-1 and 2- in order to ensure the heat resistance of the air guide member 10 and to prevent the amount of cooling air from decreasing. 2 is set to the same height as the upper end.

Further, in FIG. 4 shown to如 rather as another reference example, the case where the partition wall 8 and one plate structure, like the reference example shown in FIG. 1, a pair of side plates 10a erected on the distribution plate 4, An air guide member 10 configured by 10 a is provided, and air from the air supply chamber 5 is blown out from the upper end of the air guide member 10 through the communication hole 4 b and the internal space of the air guide member 10, A cooling air flow a flowing upward along the outer wall surfaces on both sides in the direction is generated. In the second embodiment, the height of the upper end of the air guide member 10 is set to each of the burners 2-1, so as to ensure the heat resistance of the air guide member 10 and prevent the cooling air amount from decreasing. Set to the same height as the upper end of 2-2.

FIG. 5 shows a first embodiment of the present invention . In this structure, the partition wall 8 is formed in a hollow structure composed of two plates 8a and 8a, and a pair of shoulder portions 10b projecting outwardly in the lateral direction by bending each plate 8a at the lower part of the partition wall 8. , 10b and a pair of side plate portions 10c, 10c extending downward from the shoulder portions 10b, 10b toward the distribution plate 4. Thus, the hollow air guide member 10 integrated with the partition wall 8 is constituted by the shoulder portions 10b, 10b and the side plate portions 10c, 10c. The internal air gap of the air guide member 10 is communicated with the air supply chamber 5 through a communication hole 4b formed in the distribution plate 4 and having an opening area per unit area larger than the distribution hole 4a. Further, as shown in FIG. 6, a plurality of air blowing holes 10 d that open upward are formed in both shoulder portions 10 b and 10 b that are the upper ends of the air guide member 10.

According to this, a relatively large amount of air is supplied from the air supply chamber 5 to the internal space of the air guide member 10, and a part of this air flows into the space between the two plates 8 a and 8 a of the partition wall 8. The cooling air flow b is generated inside the partition wall 8 and the cooling air flow a flowing upward along the outer wall surface of the partition wall 8 is generated by the air blown from the air blowing hole 10d of the shoulder 10b. . Therefore, specifications outright wall 8 can be efficiently cooled from the inside and outside. And in 1st Embodiment, since the air guide member 10 is integrated with the partition wall 8, a number of parts can be reduced and cost reduction can be aimed at.

The height of the shoulder 10b is the same height as the upper ends of the burners 2-1 and 2-2 so as to ensure the heat resistance of the air guide member 10 and to prevent a decrease in the amount of cooling air. Set to. In the first embodiment, the partition wall 8 has a hollow structure composed of two plates 8a and 8a. However, the partition wall 8 has a single-plate structure, and only the lower part of the partition wall 8 is bifurcated. It is also possible to branch to form the air guide member 10 composed of the shoulder portions 10b and 10b and the side plate portions 10c and 10c. However, in this case, it is necessary to form the partition wall 8 by a special manufacturing method such as extrusion molding. On the other hand, if comprised like 1st Embodiment, since the shoulder part 10b and the side-plate part 10c can be formed by the simple bending process of the two board | plates 8a and 8a which comprise the partition wall 8, processing cost is cheap. In addition, the partition wall 8 can be air-cooled from the inside and outside to improve the cooling performance, which is advantageous.

Further, in the first embodiment shown in FIG. 5, measures are taken to reduce combustion noise. Here, the first and second combustion chambers 7-1 and 7-2 communicate with each other through the first and second heat exchangers 3-1 and 3-2 and the partition wall 8 so as to allow ventilation. If so, air column vibrations are generated using the combustion chambers 7-1 and 7-2 as one continuous vibration space. The natural frequency F of the air column vibration is F = C / 2L where C is the speed of sound and L is the length of the vibration space. When both combustion chambers 7-1 and 7-2 become one continuous vibration space, if the lateral width of the can 1 is, for example, 31 cm, L becomes about 37 cm due to the influence of the partition wall 8. Moreover, the average temperature in the can 1 at the time of combustion will be about 170 degreeC, and C will be 435 m / sec at this time. The natural frequency F of the air column vibration generated as one continuous vibration space between the combustion chambers 7-1 and 7-2 is 590 Hz. At such a low frequency, the flame easily resonates and generates a large combustion noise.

For this reason, in the first embodiment, the side ends of the heat exchangers 3-1 and 3-2 facing the boundary between the first and second heat exchangers 3-1 and 3-2 are shown in FIG. As shown in FIG. 2, a sealing portion 3c is provided for sealing the gap between the heat absorbing fins 3a of the heat exchangers 3-1, 3-2. And the two plates 8a and 8a which comprise the partition wall 8 are both heat exchanger 3 in the upper end part of both plates 8a and 8a inserted in the boundary part of both heat exchangers 3-1 and 3-2. -1 and 3-2 are in contact with the sealing portions 3c and 3c. According to this, ventilation between both heat exchangers 3-1 and 3-2 is blocked by the sealing part 3c, and both heat exchangers 3-1 and 3-2 of both combustion chambers 7-1 and 7-2 are blocked. The communication between the combustion chambers 3-1 and 3-2 via the gap between the partition wall 8 and the heat exchangers 3-1 and 3-2 is also cut off. It is. In addition, although the sealing part 3c is formed by the bending part formed in the side edge part of the heat absorption fin 3a, it is also possible to comprise the sealing part 3c with the board | plate material separate from the heat absorption fin 3a. .

Further, since the air blowing holes 10d are formed in the respective shoulder portions 10b of the two plates 8a and 8a constituting the partition wall 8, the air blowing hole 10d and the gap between the plates 8a and 8a are not changed as they are. Both combustion chambers 7-1 and 7-2 communicate with each other. Therefore, an intermediate partition plate 8b that bisects the gap between the plates 8a and 8a in the lateral direction from the distribution plate 4 to the upper end of the partition wall 8 is interposed between the plates 8a and 8a. As a result, the communication between the combustion chambers 7-1 and 7-2 via the air blowing hole 10d and the gap between the plates 8a and 8a is also cut off. In addition, joining flanges 8d and 8d are formed at the uppermost ends of both plates 8a and 8a with standing bent portions 8c and 8c extending inward in the lateral direction. Are joined so as to sandwich the upper end of the partition plate 8b. Then, as shown in FIG. 7, a vent hole 8e is formed in the bent portions 8c and 8c at the upper ends of both plates 8a and 8a, and the air flowing into the gap between the plates 8a and 8a is heated from the vent hole 8e. It flows out to the boundary part of the exchangers 3-1 and 3-2.

  When the communication between the combustion chambers 7-1 and 7-2 is interrupted as described above, the generation of air column vibrations that make both the combustion chambers 7-1 and 7-2 one continuous vibration space is prevented. Column vibration is generated individually in each of the combustion chambers 7-1 and 7-2, and the natural frequency of the air column vibration is increased. For example, when the width of the first combustion chamber 7-1 is 23 cm and the width of the second combustion chamber 7-2 is 7 cm, the natural frequency of the air column vibration generated in each of the combustion chambers 7-1 and 7-2 is The first combustion chamber 7-1 has a frequency of 950 Hz, and the second combustion chamber 7-2 has a frequency of 3100 Hz. When the natural frequency reaches such a high value, the flame hardly resonates and combustion noise is reduced.

FIG. 8 shows a second embodiment which is a modification of the first embodiment. The can body 1 and the heat exchangers 3-1 and 3-2 of the second embodiment are the same as those of the first embodiment. However, in order to reduce the rated combustion amount of the second burner 2-2, the first The innermost unit burner 2a of the second burner 2-2 in the embodiment is removed. Then, the side plate portion 10c on the second burner 2-2 side (left side in FIG. 8) is displaced to the left side by the amount of the removed unit burner 2a. On the other hand, since both the heat exchangers 3-1 and 3-2 are the same as those of the first embodiment, the upper end portion of the partition wall 8 inserted in the boundary portion between the both heat exchangers 3-1 and 3-2. The position of does not change. As a result, the lateral distance between the upper end portion of the left plate 8a of the partition wall 8 and the left side plate portion 10c increases. In this case, if the lateral width of the left shoulder portion 10b formed on the left plate 8a at the same height as the upper end of the second burner 2-2 is set equal to the lateral distance, the upper portion of the left shoulder portion 10b. Thus, a low pressure recirculation zone is generated, and the flame of the second burner 2-2 is tilted toward the recirculation zone to make combustion unstable. In order to prevent this, it is conceivable to increase the opening area of the air blowing hole 10d formed in the left shoulder 10b. However, this causes excessive air, and the second heat exchanger 3-2 is cooled with air. Thermal efficiency will deteriorate.

Therefore, in the second embodiment, the lateral width of the left shoulder 10b is set to be narrower than the lateral distance, and the left plate 8a has a height equivalent to the upper end of the flame at the time of maximum combustion of the second burner 2-2. A step portion 8f having a lateral width that is a difference between the lateral distance and the lateral width of the left shoulder 10b is formed at the portion that becomes the thickness. According to this, the portion between the shoulder portion 10b and the step portion 8f of the left plate 8a approaches the second burner 2-2 side. Therefore, even if the opening area of the air blowing hole 10d opened in the left shoulder portion 10b is not increased, a reflux region does not occur immediately above the shoulder portion 10b, and the inclination of the flame is prevented and the combustion is stabilized. .

  Here, in order to ensure the stability of combustion even at the time of maximum combustion, it is necessary to set the position of the step portion 8f to the same height as the upper end of the flame at the time of maximum combustion. On the other hand, when the position of the step portion 8f is increased, the vertical distance between the step portion 8f and the second heat exchanger 3-2 is shortened, and the second heat exchanger 3 located immediately above the step portion 8f. It becomes difficult for combustion exhaust gas to flow in the portion -2, and thermal efficiency is lowered. If the step portion 8f is formed at a height equivalent to the upper end of the flame at the time of maximum combustion of the second burner 2-2 as in the fourth embodiment, both combustion stability and thermal efficiency can be successfully achieved.

In the second embodiment, the step portion 8f is formed horizontally. However, in order to make it easy to guide the combustion exhaust to the portion of the second heat exchanger 3-2 located immediately above the step portion 8f, the step portion 8f is formed horizontally. The step portion 8f may be formed so as to incline upward toward the inner side in the direction. When the innermost unit burner 2a in the lateral direction of the first burner 2-1 is removed and the position of the right side plate portion 10c is displaced to the right by the amount of the removed unit burner 2a, the right plate 8a Also, a step is formed in the same manner as the left plate 8a.

  As mentioned above, although embodiment which applied this invention to the 1 can type | mold composite heat source machine which has the 1st heat exchanger 3-1 for hot-water supply and the 2nd heat exchanger 3-2 for heating was described, 2nd heat When the exchanger 3-2 is a heat exchanger for retreating a bath in which a bath endothermic pipe that circulates the hot water of the bath is passed through the endothermic fin, or the endothermic pipe and the endothermic pipe are passed through the endothermic fin In the case of a heat exchanger for heating and bathing, the first heat exchanger 3-1 is also used for hot water and bathing in which the heat-absorbing fin penetrates the hot-water heat-absorbing tube and the bath heat-absorbing tube. The present invention can be similarly applied to a case where the heat exchanger is a heat exchanger or a heat exchanger other than for hot water supply. In addition, the first and second heat exchangers 3-1 and 3-2 are completely separated in any of the above embodiments, but the first and second heat exchangers 3-1 are both separated. , 3-2 can be constituted by a continuous common fin.

The typical cutting front view showing the composition of the heat source machine as a reference example . FIG. 2 is a cut side view taken along line II-II in FIG. 1. The cut side view cut | disconnected by the III-III line | wire of FIG. The typical cutting front view showing the composition of the heat source machine as other reference examples . The typical cutting front view showing composition of a 1st embodiment of the present invention heat source machine. The perspective view which shows the partition wall of 1st Embodiment. The expansion cutting top view cut | disconnected by the VII-VII line of FIG. The typical cutting front view showing composition of a 2nd embodiment of the present heat source machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Can body, 2-1 ... 1st burner, 2-2 ... 2nd burner, 2a ... Unit burner, 3-1 ... 1st heat exchanger, 3-2 ... 2nd heat exchanger, 4 ... Distribution board 4a ... distribution hole, 5 ... supply chamber, 6 ... combustion fan, 7-1 ... first combustion chamber, 7-2 ... second combustion chamber, 8 ... partition wall, 8a ... plate, 8b ... partition plate, 1 0d: Air blowing hole.

Claims (1)

A single can body, a first and second pair of burners provided side by side in the can body, and a first and second pair of heat exchangers provided side by side on the top of the can body And a first combustion chamber and a second burner extending from the first burner to the first heat exchanger in a space between the first and second burners and the first and second heat exchangers in the can. And a second combustion chamber extending from the first heat exchanger to the second heat exchanger, and defining a supply chamber partitioned by a distribution plate at a lower portion of the can body, and combustion air from the combustion fan In a single can type combined heat source machine that supplies the first and second combustion chambers through distribution holes formed in the distribution plate,
The partition wall is composed of two plates facing each other in the lateral direction with a gap through which air flows from the air supply chamber ,
The side wall of each heat exchanger facing the boundary between the two heat exchangers is provided with a sealing portion for sealing a gap between the heat absorption fins constituting each heat exchanger, and constitutes the partition wall. The two plates are brought into contact with the sealing portions of both heat exchangers at the upper end portions of both plates inserted into the boundary portion of both heat exchangers,
An air blowing hole is opened in the two plates constituting the partition wall,
A single can type combined heat source machine, characterized in that an intermediate partition plate that bisects the gap between the two plates in the lateral direction from the distribution plate to the upper end of the partition wall is interposed between the two plates .

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