Stainless steel heat exchanger for wall-mounted water heater

Abstract

This invention discloses a stainless steel heat exchanger for wall-mounted water heaters, belonging to the technical field of gas water heaters. A flue gas adaptive mechanism is installed within the annular flue gas channel between the burner and the heat exchange coil. This mechanism includes a cylindrical mounting frame and several heat-deformation strips on its circumference, forming flue gas flow gaps between the heat-deformation strips. Each heat-deformation strip includes a fixed section and a deformable section made of bimetallic composite material. The fixed section has a sliding port, and the deformable section has a T-shaped head that engages with the sliding port. At high temperatures, the deformable section bulges outwards from the mounting frame, widening the flue gas flow gap to reduce resistance; at low temperatures, the deformation recovers, narrowing the flue gas flow gap to increase speed. This invention utilizes the heat deformation characteristics of bimetal to achieve adaptive adjustment of the flow cross-sectional area according to the load, requiring no external power, and effectively solving the contradiction between carbon buildup under low loads and high resistance under high loads.

Description

Technical Field

[0001] This invention relates to the field of gas water heater technology, and more specifically to a stainless steel heat exchanger for a wall-mounted water heater. Background Technology

[0002] In a fully premixed condensing wall-mounted gas water heater, the air required for combustion is forcibly supplied by a fan and premixed with the gas. The flue gas produced by combustion flows sequentially through the main combustion chamber, heat exchange tube bundle, and condensing section before being discharged. A typical heat exchanger structure is as follows: a cylindrical shell with a cylindrical burner at its center, surrounded by stacked spiral heat exchange flat tubes, with gaps between adjacent flat tubes serving as flue gas flow channels; a baffle is located in the middle of the burner mounting cavity, dividing the entire cavity into the main combustion chamber and the condensing section. The flue gas flow path is roughly as follows: combustion is completed in the main combustion chamber first, then it flows radially outward through the gaps between the heat exchange coils, then flows axially along the shell, then flows through the coil gaps again to converge at the center, and finally is discharged from the exhaust port at the other end of the shell. A ring-shaped flue gas passage is formed between the burner and the heat exchange coil. In existing designs, this passage is usually an open and unobstructed structure with a fixed and relatively ample flow cross-sectional area. Theoretically, this structure is most advantageous under high-load conditions—low flue gas flow resistance and smooth flow.

[0003] However, this design reveals significant flaws under low-load conditions: the system heat load is low, the gas supply is correspondingly reduced, and the fan speed must be reduced accordingly to match the air volume required for this condition; the speed cannot be increased solely to improve the flue gas velocity. Due to the fixed and relatively large cross-sectional area of ​​the channel, the flue gas velocity is low under low load, resulting in insufficient scouring force on the heat exchange tube walls. Trace amounts of carbon black and byproducts generated during combustion easily deposit on the tube wall surface, and long-term accumulation reduces heat exchange efficiency and affects overall system reliability. An intuitive solution is to add a narrowing structure within the annular channel to increase local flow velocity. However, if a fixed narrowing is used, a new contradiction arises under high-load conditions—the narrowing structure becomes a flow bottleneck as the flue gas flow increases, causing a sharp increase in resistance and sacrificing the low-resistance advantage of the originally open channel under high load.

[0004] It is evident that at low loads, a narrower diameter is needed to increase flow velocity and enhance scouring, while at high loads, a wider diameter is needed to reduce resistance and maintain smooth flow. These two requirements place diametrically opposed demands on the flow cross-section of the annular channel, and existing open channel structures cannot achieve a balance. Therefore, there is an urgent need for an adaptive device that can automatically adjust the flow cross-section of the annular channel according to the load. At low loads, a smaller flow cross-section should be used to increase flow velocity and enhance scouring, while at high loads, the diameter should be automatically expanded to reduce resistance and restore smooth flow. Summary of the Invention

[0005] The purpose of this invention is to provide a stainless steel heat exchanger for a wall-mounted water heater, wherein a variable cross-section adjustment structure is provided in the annular flue gas channel around the burner. At high temperatures, the middle section expands outward to increase the flow area and reduce resistance, while at low temperatures it returns to a straight line to reduce the flow area and increase the flow rate, thereby achieving adaptive adjustment across the entire load range.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a stainless steel heat exchanger for a wall-mounted water heater, comprising a cylindrical outer shell, and a burner and a heat exchange coil disposed within the outer shell; the outer shell is provided with a water inlet, a water outlet, and a flue gas outlet; the heat exchange coil is formed by bending stainless steel flat tubes that extend in a stacked spiral pattern, with a heat exchange gas gap formed between two adjacent coils; the heat exchange coil is coaxially disposed within the outer shell, and a combustion chamber is formed at the center of the heat exchange coil; an annular flue gas channel is formed between the heat exchange coil and the inner wall of the outer shell, and the annular flue gas channel communicates with the flue gas outlet; both ends of the heat exchange coil extend and are respectively encapsulated at the water inlet and water outlet of the outer shell; the burner is disposed on the inner surface of the front of the outer shell, and a premixed air inlet pipe connected to the burner is disposed on the outer surface; The combustion chamber is also equipped with a flue gas adaptive mechanism. When the burner is running at low load, the flue gas adaptive mechanism can reduce the diameter of the flue gas flow path between the combustion chamber and the heat exchange gas gap to accelerate the flue gas under low load conditions. When the burner is running at high load, the mechanism can expand the diameter of the flue gas flow path between the combustion chamber and the heat exchange gas gap to reduce the flue gas drag under high load conditions.

[0007] Preferably, the flue gas adaptive mechanism includes a cylindrical mounting frame and a plurality of heat-deformable strips extending along the length of the mounting frame on the circumference of the mounting frame, wherein the heat-deformable strips form a flue gas flow gap. The heat-deformable strip has at least one deformable section. Under high-load conditions of the burner, the deformable section can expand the flue gas flow gap between adjacent heat-deformable strips by radial expansion along the mounting frame to reduce flue gas drag. Under low-load conditions of the burner, the deformable section can reduce the flue gas flow gap between adjacent heat-deformable strips by a smaller radial expansion deformation compared to the high-load conditions to accelerate the flue gas flow.

[0008] Preferably, the heat-deformable strip includes multiple fixed sections fixed to the mounting frame and multiple deformable sections disposed between the fixed ends; the ends of the fixed sections and the deformable sections are movably connected and can slide relative to each other; the deformable sections are composed of a low thermal expansion metal layer located in the inner layer and a high thermal expansion metal layer located in the outer layer, which are hot-rolled and melted together.

[0009] Preferably, a sliding opening extending along the length of the fixed section is provided on the fixed section opposite to the deformable section, and a T-shaped head is provided on the deformable section that passes through and is engaged with the sliding opening; the outer end of the sliding opening is provided with a notch extending to the end of the fixed section. (The T-shaped head is vertically inserted through the notch and twisted to form an assembly. In addition to allowing the deformable section to slide, the sliding opening can also expose the notch after the deformable section bulges due to the bending of both ends. At this time, the notch can allow airflow to a certain extent, forming a better turbulent and uniform flow distribution effect.) Preferably, the mounting frame includes multiple longitudinal rods evenly distributed in a ring around the axis of the mounting frame, and multiple ring rods sequentially sleeved around the longitudinal rods along the axial direction of the mounting frame and welded to the longitudinal rods; the fixing section is provided on the ring rods; and an annular disc fixedly connected to the longitudinal rods is provided at one end of the mounting frame near the front of the outer shell.

[0010] Preferably, a fire baffle is provided in the combustion chamber, and the fire baffle divides the combustion chamber into a main combustion section and a condensation section; the flue gas adaptive mechanism is located in the main combustion section; a smoke collection chamber communicating with the exhaust port is provided at the rear of the outer shell, and the smoke collection chamber is communicating with the condensation section.

[0011] Preferably, the burner is a metal mesh woven burner or a stainless steel cylindrical burner.

[0012] Preferably, the water flow direction inside the heat exchange coil is opposite to the flue gas flow direction inside the outer casing.

[0013] Preferably, the front of the outer casing is formed by a cover, the inner surface of which is provided with a burner and the outer surface of which is provided with a premixed air intake pipe; the cover is detachably connected to the outer casing by cover plate bolts.

[0014] Preferably, the inner surface of the cover is further provided with a positioning groove that cooperates with the annular disk. The annular disk is disposed in the positioning groove and connected to the cover by a frame bolt.

[0015] The beneficial effects of this invention are mainly reflected in: 1. This invention, by setting a variable cross-section adjustment mechanism composed of heat-deformable strips in the annular flue gas channel around the burner, utilizes the autonomous bending deformation of bimetallic strips under temperature changes to achieve adaptive adjustment of the flow cross-sectional area with the load—reducing the diameter and speed at low loads to enhance the scouring of the heat exchange tube wall and prevent carbon black deposition, and expanding the diameter and reducing resistance at high loads to maintain smooth flue gas flow, thereby effectively solving the contradiction that existing fixed cross-section channels cannot meet the requirements of full-load conditions.

[0016] 2. This invention designs the heat-deformable strips as a structure with fixed and deformable sections that are connected in a movable manner. The deformable section is composed of an inner layer of low-thermal-expansion metal and an outer layer of high-thermal-expansion metal. At high temperatures, the outer layer expands more than the inner layer, and the deformable section automatically bends towards the low-expansion side, that is, it bulges outward towards the outside of the mounting frame, causing the diameter of the ring formed by multiple heat-deformable strips to increase locally, and the flue gas flow gap between adjacent heat-deformable strips to widen accordingly. At low temperatures, the deformation recovers, and the flow gap narrows accordingly. This structure achieves passive adaptive adjustment entirely based on the physical properties of the material itself, without the need for external power or additional control intervention.

[0017] 3. The present invention features a movable connection method in which a sliding port is provided on the fixed section and a T-shaped head is provided on the deformable section. This allows the deformable section to slide freely along the length of the fixed section during expansion and recovery to release thermal deformation stress, avoiding the accumulation of internal stress and attenuation of deformation caused by the fixed constraints at both ends. Furthermore, the locking and cooperation between the T-shaped head and the sliding port ensures that the deformable section will not detach from the fixed section, thus ensuring the integrity of the structure and the consistency of its operation during long-term use. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a schematic diagram of the internal structure of the present invention; Figure 3 A three-dimensional structural diagram for installing the frame; Figure 4 This is a schematic diagram showing the installation of the heat-deformable strip on the mounting frame in its unfolded state. Figure 5 This is a structural diagram of the fixed section and the deformable section; Figure 6 These are schematic diagrams of the structure under two states of deformation. Figure 7 This is a schematic diagram of the structure of the heat-deformation strip; Figure 8 for Figure 7 A schematic diagram of the state of a heat-deformable strip under high load conditions.

[0019] Figure label: 1-Outer shell, 2-Burner, 3-Heat exchange coil, 4-Water inlet, 5-Water outlet, 6-Flue gas outlet, 7-Heat exchange gas slit, 8-Combustion chamber, 9-Annular flue gas passage, 10-Premixed air inlet pipe, 11-Flue gas adaptive mechanism, 12-Mounting frame, 13-Thermal deformation strip, 14-Flue gas flow slit, 15-Deformation section, 16-Fixed section, 17-Sliding port, 18-T-head, 19-Notch, 20-Longitudinal rod, 21-Ring rod, 22-Annular disc, 23-Fireproof plate, 24-Main combustion section, 25-Condensation section, 26-Flue gas collection chamber, 27-Sealing cover, 28-Cover plate bolt, 29-Positioning groove, 30-Frame bolt. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be understood that the terms "center", "axial", "radial", "front", "rear", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0022] Combination Figures 1 to 8 As shown, this embodiment specifically discloses a stainless steel heat exchanger for a wall-mounted water heater, which is fully compatible with a premixed condensing wall-mounted gas water heater. It mainly includes a cylindrical outer shell 1, a burner 2, a heat exchange coil 3, and a flue gas adaptive mechanism 11. The outer shell 1 has an inlet 4, an outlet 5, and a flue gas outlet 6. The heat exchange coil 3 is formed by continuously bending stainless steel flat tubes into a layered spiral axially extending structure. A through-flow heat exchange gas slit 7 is formed between adjacent coils of stainless steel flat tubes, providing a stable flow path for flue gas heat exchange. The heat exchange coil 3 is coaxially assembled inside the outer shell 1, with a combustion chamber 8 formed at its center. An annular flue gas channel 9 is formed between the outer wall of the heat exchange coil 3 and the inner wall of the outer shell 1. The end of the annular flue gas channel 9 connects to the flue gas outlet 6, achieving unified convergence and discharge of the flue gas after heat exchange. The two ends of the heat exchange coil 3 are respectively connected and sealed at the inlet 4 and the outlet 5, forming a complete water circulation heat exchange loop.

[0023] A removable cover 27 is provided on the front of the outer casing 1. The cover 27 is locked to the outer casing 1 by multiple sets of cover bolts 28, which is convenient for disassembly and assembly, and facilitates the assembly of internal components and subsequent maintenance. The burner 2 is centrally mounted on the inner surface of the cover 27. In this embodiment, the burner 2 is preferably a metal mesh woven burner or a stainless steel cylindrical microporous burner, which can achieve uniform premixed combustion of gas and air. The outer surface of the cover 27 is fixedly connected to the premixed air inlet pipe 10 for conveying the premixed gas mixture of gas and air. A fire baffle 23 is fixedly installed inside the combustion chamber 8. The fire baffle 23 precisely divides the combustion chamber 8 axially into a front main combustion section 24 and a rear condensation section 25. The rear end of the outer casing 1 integrates a smoke collection chamber 26, which connects the condensation section 25 and the exhaust port 6 to ensure the orderly flow and discharge of flue gas after heat exchange, as well as the effective recovery of preheated flue gas, thereby achieving preheating of water. The water flow direction inside the heat exchange coil 3 is arranged in a counter-current manner to the flue gas flow direction inside the shell 1, which effectively improves the temperature difference between the hot and cold media and greatly optimizes the condensation heat exchange efficiency.

[0024] To address the technical shortcomings of existing fixed-section flue gas channels that cannot accommodate both high and low load conditions, this invention incorporates a flue gas adaptive mechanism 11 within the combustion chamber 8 of the main combustion section 24 and within the annular flue gas channel 9 between the burner 2 and the heat exchange coil 3. This mechanism is a passive thermal deformation adaptive adjustment structure that requires no electrical control or power drive. It can adaptively adjust the flue gas flow cross-sectional area in real time according to the flue gas temperature, perfectly adapting to the full-load operation of the water heater.

[0025] Specifically, such as Figure 2 As shown, the flue gas adaptive mechanism 11 includes a cylindrical hollow structure mounting frame 12 and multiple sets of axially extending heat-deformable strips 13. Figure 3 As shown, the mounting frame 12 is welded together from multiple longitudinal rods 20 evenly distributed in a ring along the axis and multiple ring rods 21 arranged equidistantly along the axis. It has a high overall perforation rate and low flue gas obstruction, thus avoiding additional ventilation resistance. The ring rods 21 are fixedly sleeved on the outside of the longitudinal rods 20, resulting in high overall structural strength and good coaxiality, allowing it to withstand long-term high-temperature flue gas conditions without deformation. An annular disc 22 is fixedly welded to the front end of the mounting frame 12 near the cover 27. A positioning groove 29 matching the annular disc 22 is formed on the inner surface of the cover 27. The annular disc 22 is embedded in the positioning groove 29 and locked in place by the frame bolts 30, achieving precise coaxial fixation of the mounting frame 12 and preventing operational deviation and vibration.

[0026] Multiple heat-deformable strips 13 are evenly spaced around the mounting frame 12 and extend parallel to the axial direction of the mounting frame 12 throughout. A through-flow flue gas joint 14 is formed between adjacent heat-deformable strips 13, and all flue gas joints 14 together constitute the effective flow area of ​​the annular flue gas channel 9. Each heat-deformable strip 13 adopts a segmented combination structure, including at least one deformable segment 15, such as... Figure 7and 8 As shown, there are 3 deformable sections 15 and 4 fixed sections 16. The deformable sections 15 are connected between two adjacent fixed sections 16. The fixed sections 16 are rigidly fixed to the mounting frame 12 without relative displacement. The deformable sections 15 are free deformation functional areas that can undergo radial expansion and convex deformation with temperature changes.

[0027] The deformable segment 15 is the core adaptive functional component, integrally formed using a double-layer dissimilar alloy hot rolling, pressing, melting, and diffusion composite process. The two metal layers achieve metallurgical bonding through high-temperature solid-state atomic diffusion, eliminating the brittle weld layer and resulting in high bonding strength and excellent resistance to thermal fatigue, making it suitable for the frequent start-stop and high-low temperature alternating operating conditions of water heaters. Specifically, the inner layer of the deformable segment 15 is a low thermal expansion coefficient alloy layer, while the outer layer is a high thermal expansion coefficient alloy layer. Based on the physical characteristics of bimetallic thermal deformation, the difference in thermal expansion between the two metal layers is minimal at low temperatures, allowing the deformable segment 15 to maintain a basically straight state, or in other words, to have a relatively small amount of bulging deformation. At high temperatures, the thermal elongation of the outer high-expansion alloy is much greater than that of the inner low-expansion alloy, forcing the deformable segment 15 to radially bulge and bend towards the high-expansion outer side, achieving adaptive shape change.

[0028] To address the issues of stress accumulation, deformation jamming, and structural detachment during thermal deformation, a long, narrow sliding opening 17 is provided along the length of the sidewall of the fixed section 16. A notch 19 extending to the end of the fixed section 16 is provided at the outer end of the sliding opening 17. T-shaped heads 18 are integrally formed at both ends of the deformable section 15. During assembly, the T-shaped heads 18 are vertically aligned with the notch 19 and inserted. After insertion, the deformable section 15 is twisted, causing the T-shaped heads 18 to laterally engage with the sliding opening 17, completing the movable assembly. This assembly structure allows for axial relative sliding between the deformable section 15 and the fixed section 16. When the deformable section 15 undergoes radial expansion deformation, the sliding opening 17 can adaptively slide to compensate for thermal deformation stress, completely avoiding problems such as deformation restriction, stress cracking, and deformation attenuation caused by rigid fixing at both ends, ensuring deformation accuracy and structural service life. Simultaneously, after the deformable section 15 expands and bends outward, the notch 19 is naturally exposed, which can assist in diverting flue gas, breaking the local laminar flow state, improving the circumferential uniformity of flue gas distribution, and further optimizing heat transfer consistency.

[0029] The specific adaptive working process of this invention is as follows: When the water heater is in low-load, low-fire mode, the gas supply and fan speed decrease simultaneously, resulting in low overall flue gas temperature, small flow rate, and slow velocity. At this time, the thermal expansion difference between the two layers of metal in the deformed section 15 is negligible, and the overall structure remains flat. Figure 6As shown in the upper view, the heat-deformable strip 13 is closely attached to the mounting frame 12, the opening of the flue gas flow gap 14 between adjacent heat-deformable strips 13 is at its minimum, and the overall effective flow cross-sectional area of ​​the annular flue gas channel 9 is reduced. Under the premise of reduced flue gas flow, the contracted flow channel can significantly increase the radial flue gas velocity, strengthen the scouring force of flue gas on the inner wall of the heat exchange gas gap 7, completely eliminate the low-speed stagnation area in the channel, effectively inhibit the deposition and adhesion of carbon black particles and sticky by-products generated by combustion, and fundamentally solve the problems of low-load ash and carbon accumulation and heat exchange efficiency decline.

[0030] When the water heater is under high load and high flame conditions, the gas is fully combusted, resulting in high flue gas temperature and large flow rate. At this time, the outer high-expansion alloy layer of the deformable section 15 elongates significantly, while the inner low-expansion alloy layer deforms only slightly. This drives the deformable section 15 to bulge and bend radially outward, causing the entire heat-deformed strip 13 to expand outward. This causes the opening of the flue gas flow gap 14 between adjacent heat-deformed strips 13 to increase synchronously, and the overall effective flow cross-sectional area of ​​the annular flue gas channel 9 to automatically expand. The expanded flow channel has no throttling bottleneck, significantly reducing the flow resistance of large-flow flue gas and ensuring smooth flue gas discharge under high load conditions, while retaining the advantages of low resistance in traditional open channels. At the same time, the circumferentially uniformly bulging heat-deformed strip 13 can evenly distribute and guide the central flue gas, avoiding localized concentrated impact of flue gas on the heat exchange coil 3, ensuring uniform flue gas load in each circumferential heat exchange gap 7, and eliminating the problem of localized overload and blockage.

[0031] When the water heater is under medium load steady-state operation, the flue gas temperature is moderate, the deformation section 15 maintains a stable central convex arc, the opening of the flue gas flow gap 14 remains constant, the flow field is stable, and the anti-deposition and low-resistance flow effects are taken into account, achieving adaptive balance under all operating conditions.

[0032] In summary, this invention, through a passive bimetallic thermal deformation structure, precisely solves the technical problem of conflicting flow field requirements under high and low load conditions in traditional heat exchangers without manual intervention or electronic control adjustment. It features a simple and reliable structure, convenient assembly, and strong adaptability, effectively extending the heat exchanger's cleaning-free operation cycle and improving the overall operational stability and heat exchange efficiency. It possesses extremely high practical value and promising prospects for widespread application.

Claims

1. A stainless steel heat exchanger for a wall-mounted water heater, comprising a cylindrical outer shell (1), and a burner (2) and a heat exchange coil (3) disposed within the outer shell (1); the outer shell (1) is provided with a water inlet (4), a water outlet (5), and a flue gas outlet (6); the heat exchange coil (3) is formed by bending stainless steel flat tubes that extend in a stacked spiral shape, with a heat exchange gas gap (7) formed between two adjacent turns of stainless steel flat tubes; the heat exchange coil (3) is coaxially disposed within the outer shell (1). The heat exchange coil (3) forms a combustion chamber (8) at its center, and an annular flue gas passage (9) is formed between the heat exchange coil (3) and the inner wall of the outer shell (1). The annular flue gas passage (9) is connected to the exhaust port (6). The two ends of the heat exchange coil (3) extend and are encapsulated at the water inlet (4) and water outlet (5) of the outer shell (1), respectively. A burner (2) is provided on the inner surface of the front of the outer shell (1), and a premixed air inlet pipe (10) connected to the burner (2) is provided on the outer surface. Its features are: The combustion chamber (8) is also equipped with a flue gas adaptive mechanism (11). When the burner (2) is running at low load, the flue gas adaptive mechanism (11) can reduce the diameter of the flue gas flow path between the combustion chamber (8) and the heat exchange gas gap (7) to achieve flue gas acceleration under low load conditions. When the burner (2) is running at high load, it can expand the diameter of the flue gas flow path between the combustion chamber (8) and the heat exchange gas gap (7) to achieve flue gas drag reduction under high load conditions.

2. The stainless steel heat exchanger for a wall-mounted water heater according to claim 1, characterized in that: The flue gas adaptive mechanism (11) includes a cylindrical mounting frame (12) and several heat-deformable strips (13) extending along the length of the mounting frame (12) on the circumference of the mounting frame (12), and the heat-deformable strips (13) form a flue gas flow gap (14). The heat-deformable strip (13) has at least one deformable section (15). Under high-load conditions of the burner (2), the deformable section (15) expands radially along the mounting frame (12) to widen the flue gas flow gap (14) between adjacent heat-deformable strips (13) to reduce flue gas drag. Under low-load conditions of the burner (2), the deformable section (15) has a smaller radial expansion deformation amount compared to the high-load conditions to relatively narrow the flue gas flow gap (14) between adjacent heat-deformable strips (13) to accelerate the flue gas.

3. The stainless steel heat exchanger for a wall-mounted water heater according to claim 2, characterized in that: The heat-deformable strip (13) includes multiple fixed sections (16) fixed on the mounting frame (12) and multiple deformable sections (15) disposed between the fixed ends; the ends of the fixed sections (16) and the deformable sections (15) are movably connected and can slide relative to each other; the deformable section (15) is composed of a low thermal expansion metal layer located in the inner layer and a high thermal expansion metal layer located in the outer layer, which are hot-rolled and melted together.

4. The stainless steel heat exchanger for a wall-mounted water heater according to claim 3, characterized in that: A sliding opening (17) extending along the length of the fixed section (16) is provided on the fixed section (16) at a position opposite to the deformable section (15). A T-shaped head (18) is provided on the deformable section (15) and passes through and is locked on the sliding opening (17). A notch (19) extending to the end of the fixed section (16) is provided at the outer end of the sliding opening (17).

5. The stainless steel heat exchanger for a wall-mounted water heater according to claim 4, characterized in that: The mounting frame (12) includes multiple longitudinal rods (20) evenly distributed in a ring around the axis of the mounting frame (12), and multiple ring rods (21) sequentially sleeved on the longitudinal rods (20) and welded to the longitudinal rods (20) along the axial direction of the mounting frame (12); the fixing section (16) is provided on the ring rods (21); the mounting frame (12) is provided with an annular disk (22) fixedly connected to the longitudinal rods (20) at one end near the front of the outer shell (1).

6. The stainless steel heat exchanger for a wall-mounted water heater according to claim 1, characterized in that: The combustion chamber (8) is provided with a fire baffle (23), which divides the combustion chamber (8) into a main combustion section (24) and a condensation section (25). The flue gas adaptive mechanism (11) is located in the main combustion section (24). The rear part of the outer shell (1) is provided with a smoke collection chamber (26) that communicates with the exhaust port (6), and the smoke collection chamber (26) communicates with the condensation section (25).

7. The stainless steel heat exchanger for a wall-mounted water heater according to claim 1, characterized in that: The burner (2) is a metal mesh woven burner or a stainless steel cylindrical burner.

8. The stainless steel heat exchanger for a wall-mounted water heater according to claim 1, characterized in that: The direction of water flow in the heat exchange coil (3) is opposite to the direction of flue gas flow in the outer shell (1).

9. The stainless steel heat exchanger for a wall-mounted water heater according to claim 5, characterized in that: The front of the outer shell (1) is formed by a cover (27), the inner surface of which is provided with a burner (2) and the outer surface of which is provided with a premixed air inlet pipe (10); the cover (27) is detachably connected to the outer shell (1) by cover bolts (28).

10. The stainless steel heat exchanger for a wall-mounted water heater according to claim 9, characterized in that: The inner surface of the cover (27) is also provided with a positioning groove (29) that cooperates with the annular disk (22). The annular disk (22) is set in the positioning groove (29) and is connected to the cover (27) by a skeleton bolt (30).

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