Energy saving dishwasher

Abstract

This utility model provides an energy-saving dishwasher, including a frame with a cleaning chamber at the upper end; a water tank, a main water inlet pipe, a water pump, and a heating unit at the lower end of the frame. A lower spray arm is located inside the water tank, and an upper spray arm and a steam heat recovery assembly are located at the upper end of the cleaning chamber. The steam heat recovery assembly includes a first heat exchange coil, which is bent in a zigzag pattern along the front-to-back direction of the frame. The inlet and outlet ends of the heat exchange coil are connected to a mounting bracket, which also has a cover surrounding the heat exchange coil with an opening at the bottom to form a steam absorption channel. The inlet end is connected to the main water inlet pipe, and the outlet end passes sequentially through the heating unit and the water pump to the upper and lower spray arms. This energy-saving dishwasher utilizes waste steam heat for heat exchange with freshly introduced clean water on the outer wall, preheating the water before it enters the heating element, reducing heating time and saving energy.

Description

Technical Field

[0001] This utility model relates to the field of commercial dishwasher technology, and more specifically, to an energy-saving dishwasher. Background Technology

[0002] Commercial dishwashers are a new type of kitchen dishwashing equipment, mainly used in kitchens of schools, hotels, businesses, military units, and dishwashing disinfection companies where the volume of dishwashing is high. Compared to manual washing, commercial dishwashers have advantages such as high washing efficiency, reduced labor costs, and solving the problem of insufficient dishwashing supply.

[0003] Commercial dishwashers are mainly divided into: undermount dishwashers, top-loading dishwashers, aisle dishwashers, and long-line dishwashers. Among them, the workflow of a top-loading dishwasher mainly includes a main wash and a rinse process. Main wash: The main wash pump draws water from the main wash tank and sprays it directly onto the surface of the dishes through the washing arms, rinsing away food residue and grease. The water then returns to the main wash tank for reuse. Rinse: Tap water enters the dishwasher's heating element and is heated by a high-powered heating element to quickly reach a temperature above 80℃. The hot water from the heating element is then forced through the inlet and sprayed onto the surface of the dishes through the rinse spray arms, finally falling back into the main wash tank.

[0004] Existing top-loading dishwashers typically use external water heated directly by a heating element before spraying the dishes through a spray arm. This method requires a long time to heat the water from room temperature to above 80°C, resulting in high energy consumption. Furthermore, the hot water generates a large amount of steam during the first main wash cycle in the washing chamber, which is currently directly released, failing to fully utilize the heat energy and causing energy waste. Summary of the Invention

[0005] To overcome at least one of the defects in the prior art, this utility model provides a wastewater heat recovery component and an energy-saving dishwasher. By recovering and utilizing the waste heat of steam to exchange heat with the fresh water entering the outer wall, the water is preheated before entering the heating pack, reducing the heating time of the heating pack and saving energy.

[0006] The technical solution adopted by this utility model is as follows: An energy-saving dishwasher is provided, including a frame. A mounting bracket is provided at the rear end of the top of the frame. A cover that can move up and down is connected to the front side of the mounting bracket. The cover, the mounting bracket, and the upper end of the frame form a cleaning chamber. A water tank, a main water inlet pipe, a water pump, and a heating unit are provided at the lower end of the frame. A lower spray arm is provided inside the water tank. An upper spray arm is provided at the upper end of the mounting bracket. A steam heat recovery assembly is also provided at the upper end of the mounting bracket. The steam heat recovery assembly includes a first heat exchange coil, which is bent in a folding manner along the front-back direction of the frame. The inlet and outlet ends of the heat exchange coil are both connected to the mounting bracket. A cover surrounding the heat exchange coil is also connected to the mounting bracket, and the lower part of the cover is open to form a steam absorption channel. The inlet end is connected to the main water inlet pipe, and the outlet end passes sequentially through the heating unit and the water pump to the upper and lower spray arms.

[0007] Furthermore, the lower end of the frame is also provided with a wastewater heat recovery assembly, which includes a wastewater tank and a second heat exchange coil. One side wall of the wastewater tank along its length is provided with a wastewater inlet communicating with its inner cavity and a clean water inlet connected to one end of the second heat exchange coil. The other side wall of the wastewater tank is provided with a wastewater outlet communicating with its inner cavity and a clean water outlet connected to the other end of the second heat exchange coil. The outlet is connected to the clean water inlet, the clean water outlet is connected to the heating unit, the wastewater inlet is connected to the overflow port of the tank, and the wastewater outlet is connected to the external drain.

[0008] As an improvement, the wastewater tank is further provided with a plurality of fins arranged at intervals along its length, the plurality of fins being used to divide the wastewater tank into a plurality of chambers, and the chambers being interconnected; each of the fins is provided with a connection hole for the second heat exchange coil to pass through.

[0009] In a further improvement, the wastewater tank includes a tank body with an opening at the top. Multiple symmetrical and vertically extending insertion slots are provided on the inner walls of the two side plates of the tank body in the width direction. Multiple fins are respectively inserted and fitted into the corresponding insertion slots. The top of the tank body is connected to a top plate, and the upper and lower ends of each fin abut against the top plate and the bottom of the tank body, respectively.

[0010] In a further improvement, water passage holes with staggered vertical alignment are sequentially opened on each pair of adjacent fins, and multiple grooves and / or protrusions are provided on the surface of each fin.

[0011] Furthermore, the second heat exchange coil is one of a spiral coil, a serpentine coil, or a loop coil, and the second heat exchange coil is formed by bending a metal corrugated pipe.

[0012] Furthermore, the heating unit includes a cylinder and a PTC heating tube. The cylinder is divided into an inlet chamber, a mixing chamber, and an outlet chamber along its length. The side wall of the cylinder is provided with an inlet pipe communicating with the inlet chamber and an outlet pipe communicating with the outlet chamber. Adjacent chambers in the inlet chamber, mixing chamber, and outlet chamber have water passages. The PTC heating tube is detachably connected to the cylinder and extends axially to the inlet chamber, mixing chamber, and outlet chamber. The side wall of the cylinder is also connected to a first detection element and a second detection element for detecting the water temperature of the inlet chamber and the outlet chamber, respectively. When the water temperature in the inlet chamber is lower than a first set value, the PTC heating tube starts heating. When the water temperature in the outlet chamber is higher than a second set value, the PTC heating tube stops heating.

[0013] Furthermore, the inner wall of the cylinder is connected to two partitions spaced apart along its length to divide the inner cavity of the cylinder into an inlet chamber, a mixing chamber, and an outlet chamber. The middle of each partition is provided with a first mounting hole for the PTC heating tube to pass through, and each partition is also provided with multiple connecting holes to form the water passage.

[0014] Furthermore, the cylinder includes a hollow circular tube, with end caps connected to both ends of the circular tube. Each end cap has a second mounting hole for the PTC heating tube to pass through, and one end of the PTC heating tube is connected to a connecting flange. The connecting flange is detachably connected to the end cap with the second mounting hole.

[0015] Preferably, both the first and second detection elements are temperature probes, and the detection ends of the two temperature probes extend through the side wall of the cylinder to the water inlet chamber and the water outlet chamber, respectively.

[0016] Compared with the prior art, the energy-saving dishwasher of this utility model has the following advantages: 1. A first heat exchange coil was added to the upper end of the cleaning chamber to absorb the heat of the steam, so that the clean water in the first heat exchange coil is preheated for the first time before entering the main heating unit for heating, which can reduce the heating time and save energy. 2. Based on steam heat recovery, a hot water heat recovery component is also installed at the lower end of the frame. External clean water first passes through the first heat exchange coil to exchange heat with steam for the first preheating. Then it flows through the wastewater heat recovery component to exchange heat with hot wastewater for the second preheating. Finally, it enters the main heating unit to achieve heating. Because the clean water has undergone two preheatings, the time required to heat to the preset temperature in the heating unit is shorter and the energy consumption is lower. According to experimental statistics, this double preheating can save 50%-60% of energy consumption.

[0017] 3. Multiple finned structures were added to the wastewater tank, dividing the tank's interior into interconnected chambers. This effectively extends the residence time of hot wastewater within the tank, allowing for better heat exchange between the clean water and the hot wastewater in the heat exchange tubes. This improves preheating efficiency, reduces heating time in the subsequent main heating stage, and lowers energy consumption. Furthermore, the fins themselves quickly absorb heat from the wastewater and conduct it to the heat exchange tubes, thereby heating the clean water. The second heat exchange coil is made of a corrugated metal structure, which increases the heat exchange area and improves efficiency compared to a straight-wall coil. Additionally, the corrugated structure inside the tube creates a turbulent flow of water, eliminating dead zones and reducing scaling. 4. The dishwasher's structure also features an improved heating unit, employing a PTC heating element. Its heat conversion efficiency reaches 99%, a 25% improvement compared to the approximately 75% efficiency of older resistance wire heating elements. Furthermore, the PTC heating element is designed to prevent dry burning and is less prone to damage. Heating begins once the drum is filled with water and continues until the desired temperature is reached, at which point hot water is released from the outlet. The entire system is divided into three zones by a perforated partition: a low-temperature zone, a mixing zone, and a high-temperature zone. When the temperature probe in the low-temperature zone reads a value below a certain threshold, the PTC heating element activates; conversely, when the temperature in the high-temperature zone exceeds a certain threshold, the PTC heating element stops heating, thus saving energy. This design also ensures that the temperature of the water outlet remains constant within a certain range.

[0018] Other improvements and advantages of this invention will be set forth in the detailed description that follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained through the structures particularly pointed out in the description and drawings. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural view of the energy-saving dishwasher of this utility model; Figure 2 This is a structural diagram of the wastewater heat recovery device of this utility model; (without cover plate). Figure 3 This is a structural diagram of the wastewater heat recovery device in this utility model without the outer casing. Figure 4 for Figure 3 Another perspective view of the structure; Figure 5 This is a structural diagram of the heating component in this utility model; Figure 6 This is a cross-sectional view of the heating component in this utility model.

[0020] Explanation of reference numerals in the attached figures: 1. Frame; 2. Mounting bracket; 3. Main washing tank; 4. Water pump; 5. Lower spray arm; 6. Upper spray arm; 7. First heat exchange coil; 8. Cover; 9. Wastewater tank; 10. Second heat exchange coil; 11. Wastewater inlet; 12. Clean water inlet; 13. Wastewater outlet; 14. Clean water outlet; 15. Fins; 16. Water passage hole; 17. Mixing chamber; 18. Water outlet chamber; 19. Water inlet pipe; 20. Water outlet pipe; 21. Connecting hole; 22. First detection element; 23. Second detection element; 24. Partition plate; 25. Round tube; 26. End cover plate; 27. Connecting flange; 28. Drain bolt; 29. ​​Mounting base; 30. Fixing clip; 31. PTC heating tube; 32. Water inlet chamber. Detailed Implementation

[0021] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0022] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "fixed" and "connected" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0023] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] See Figures 1-6 As shown in the figure, this application discloses an energy-saving dishwasher, including a frame 1. A mounting bracket 2 is provided at the rear end of the top of the frame 1. A cover that can move up and down is connected to the front side of the mounting bracket 2. The cover, the mounting bracket 2 and the upper end of the frame 1 form a closed cleaning chamber. A water tank, a main water inlet pipe, a water pump 4 and a heating unit are provided at the lower end of the frame 1. A lower spray arm 5 is provided in the water tank. An upper spray arm 6 and a steam heat recovery assembly are provided at the upper end of the mounting bracket 2. The steam heat recovery assembly includes a first heat exchange coil 7. The first heat exchange coil 7 is bent in a folding manner along the front and rear direction of the frame 1. The water inlet and outlet of the heat exchange coil are both connected to the mounting bracket 2, which facilitates the installation and layout of the connecting pipes on the mounting bracket 2.

[0025] Additionally, a cover 8 surrounding the heat exchange coil is connected to the mounting bracket 2, and the lower part of the cover 8 is open to form a steam absorption channel. The water inlet end of the first heat exchange coil 7 is connected to the main water inlet pipe, and the water outlet end is connected to the upper spray arm 6 and the lower spray arm 5 in sequence through the heating unit and the water pump 4.

[0026] In this structure, a first heat exchange coil 7 is added to the mounting frame 2. This first heating coil is used to absorb the heat of the steam in the cleaning chamber to achieve the first preheating of the clean water. The preheated clean water then enters the heating unit for heating. Compared with external clean water directly entering the heating unit to be heated to the set temperature, the heating time required is shorter, saving energy. In addition, a cover 8 with a lower opening is added to the outside of the first heat exchange coil 7, which allows the steam to be better concentrated on the outer periphery of the first heat exchange coil 7, improving the heat exchange efficiency. The cover 8 also serves to protect the first heat exchange coil 7.

[0027] To further improve energy efficiency and make full use of waste heat, in this embodiment, a wastewater heat recovery assembly is connected to the lower end of the frame 1. The assembly includes a rectangular wastewater tank 9, a second heat exchange coil 10, and multiple fins 15 spaced apart along the length of the wastewater tank 9. The multiple fins 15 are used to divide the inner cavity of the wastewater tank 9 into multiple independent chambers, and the chambers are interconnected. The second heat exchange coil 10 is a coil structure, and each fin 15 has a connection hole for the second heat exchange coil 10 to pass through. A wastewater inlet 11 communicating with the inner cavity and a clean water inlet 12 connected to one end of the second heat exchange coil 10 are provided on one side wall along the length of the wastewater tank 9. A wastewater outlet 13 communicating with the inner cavity and a clean water outlet 14 connected to the other end of the second heat exchange coil 10 are provided on the other side wall of the wastewater tank 9. In this structure, hot wastewater enters the wastewater tank 9 from the wastewater inlet 11, passes through multiple chambers in sequence, and is discharged from the wastewater outlet 13. Clean water enters the second heat exchange coil 10 from the water inlet and flows out from the clean water outlet 14. In the wastewater tank 9, the hot wastewater transfers heat to the second heat exchange coil 10, thereby preheating the clean water in the second heat exchange coil 10. The multiple chambers can slow down the circulation speed of the hot wastewater and improve the heat exchange efficiency. In addition, the multiple fins 15 can also quickly absorb the heat in the hot wastewater and then conduct it to the second heat exchange coil 10 to preheat the clean water. In the entire dishwasher water circulation system, external clean water first undergoes a first preheating process by exchanging heat with steam in the first heat exchange coil 7. Then, it flows through the wastewater heat recovery component to exchange heat with hot wastewater for a second preheating process. Finally, it enters the main heating unit for heating. Because the clean water undergoes two preheating processes, the time required to heat it to the preset temperature in the heating unit is shorter, and energy consumption is lower. According to experimental statistics, this double preheating process can save 50%-60% of energy consumption.

[0028] Specifically, in this embodiment, the wastewater tank 9 includes a box body with an opening at the top. Multiple symmetrical and vertically extending insertion slots are provided on the inner walls of the two side plates in the width direction of the box body. Multiple fins 15 are inserted and fitted into the corresponding insertion slots from top to bottom. The top of the box body is connected to a top plate, and the upper and lower ends of each fin 15 abut against the top plate and the bottom of the box body, respectively, so that the inner cavity of the wastewater tank 9 is divided into multiple independent chambers. Moreover, the size of the chambers can be customized and the spacing of the fins 15 can be adjusted according to actual needs. Furthermore, the insertion form of the fins 15 simplifies the installation process. During assembly, it is convenient to connect the second heat exchange coil 10 to each fin 15 first and then install it into the inner cavity of the wastewater tank 9 as a whole, thereby improving production efficiency.

[0029] Of course, in some other embodiments, each fin 15 can also be directly fixed to the inner wall of the wastewater tank 9 by welding or screwing.

[0030] Furthermore, in the above structure of this embodiment, the participants in the appendix Figure 6 Each pair of adjacent fins 15 has staggered water passage holes 16. This arrangement can further extend the residence time of hot wastewater in the wastewater tank 9, so that heat can be better transferred to the clean water in the second heat exchange coil 10, thereby improving the preheating effect. Preferably, multiple grooves and / or ridges are provided on the surface of each fin 15, which can improve the heat absorption efficiency of the fins 15 and improve the preheating efficiency of clean water from another perspective.

[0031] Furthermore, in the above structure, the second heat exchange coil 10 is one of a spiral coil, a serpentine coil, or a loop coil, and the second heat exchange coil 10 is formed by bending a metal corrugated tube. Preferably, a stainless steel corrugated tube is used to make the second heat exchange coil 10. The inner wall of the corrugated tube has a corrugated structure, which increases the heat exchange area and improves efficiency compared to a straight-walled coil structure. In addition, the corrugated structure inside the corrugated tube makes the water flow in a "turbulent" state inside the tube, with no dead corners and less prone to scaling. To reduce heat loss, an additional layer of insulation cotton is added to the outside of the wastewater tank 9 in this embodiment.

[0032] For others, see Appendix Figure 5 and 6The heating unit in this embodiment includes a cylindrical body, which is sequentially divided along its length into an inlet chamber 32, a mixing chamber 17, and an outlet chamber 18. An inlet pipe 19 communicating with the inlet chamber 32 and an outlet pipe 20 communicating with the outlet chamber 18 are provided on the side wall of the cylindrical body. Water passages exist between adjacent chambers in the inlet chamber 32, mixing chamber 17, and outlet chamber 18. Additionally, a PTC heating pipe 31 is detachably connected to the cylindrical body, extending axially to the inlet chamber 32, mixing chamber 17, and outlet chamber 18. A first detection element 22 and a second detection element 23 are also connected to the side wall of the cylindrical body for detecting the water temperature in the inlet chamber 32 and outlet chamber 18, respectively. Specifically, a corresponding controller is also set in the entire heating unit, and the first detection element 22, the second detection element 23, and the PTC heating tube 31 are all electrically connected to the controller. That is, when the first detection element 22 detects that the water temperature in the inlet chamber 32 is lower than the first set value, it will transmit a signal to the controller, and the controller will control the PTC heating tube 31 to start heating. When the second detection element 23 detects that the water temperature in the outlet chamber 18 is higher than the second set value, the second detection element 23 will feed back a signal to the controller, and the controller will control the PTC heating tube 31 to stop heating, thereby ensuring that the temperature of the outlet pipe 20 remains constant within a certain range.

[0033] Furthermore, in the above structure, the chamber inside the cylinder is divided into three areas: a low-temperature zone, a mixing zone, and a high-temperature zone. The high-temperature zone is equipped with a water outlet pipe 20 connected to the upper and lower spray arms 5 on the side wall of the cylinder, which ensures that the spray water temperature is constant within a certain range. At the same time as water is discharged from the water outlet pipe 20, cold water is added by the water inlet pipe 19. The added cold water does not directly mix into the high-temperature zone, but flows slowly into the mixing zone first. Therefore, the addition of external cold water will not cause excessive fluctuations in the temperature of the high-temperature zone. Moreover, when the temperature of the low-temperature zone drops below the first set value as cold water is added by the water inlet pipe 19, the PTC heating tube 31 will start working. Under the action of the second detection element 23, the PTC heating tube 31 will not heat continuously, but will stop heating when the temperature of the high-temperature zone reaches the second set value. This can better ensure the constant temperature of the water outlet pipe 20 with a very small fluctuation range.

[0034] In this embodiment, please refer again to the appendix. Figure 6Two partition plates 24, spaced apart along their length, are connected to the inner wall of the cylinder. These two partition plates 24 are welded and fixed to the inner wall of the cylinder. The two partition plates 24 divide the inner cavity of the cylinder into an independent inlet chamber 32, a mixing chamber 17, and an outlet chamber 18. Each partition plate 24 has a first mounting hole in its center for the PTC heating tube 31 to pass through. Each partition plate 24 also has multiple connecting holes 21 to form a water passage. Preferably, the connecting holes 21 are through holes with a diameter controlled between 0.5 and 1 cm. The area of ​​the water passage should not be too large to slow down the time it takes for cold water in the inlet chamber 32 to enter the mixing chamber 17 and the outlet chamber 18, thus preventing large fluctuations in the stability of the outlet chamber 18.

[0035] In this embodiment, preferably, the cylinder includes a hollow circular tube 25, with end caps 26 connected to both ends of the tube 25. Specifically, both end caps 26 are welded and fixed to both ends of the circular tube 25, and a second mounting hole for the PTC heating tube 31 to pass through is provided on either end cap 26. One end of the PTC heating tube 31 is connected to a connecting flange 27, which is detachably connected to the end cap 26 with the second mounting hole. This allows for a detachable connection between the PTC heating tube 31 and the cylinder, facilitating the removal of the PTC heating tube 31 for cleaning its outer wall and ensuring heating efficiency. More specifically, corresponding mounting holes are provided at the center of the two end caps 26 and the two partitions 24 to ensure that the PTC heating tube 31 is located in the center of the cylinder after installation, enabling it to heat the water in each chamber more evenly.

[0036] In addition, in the above structure, the first detection element 22 and the second detection element 23 are both cylindrical temperature probes, and the two temperature probes are connected along the direction of the outer wall of the vertical circular tube 25. The detection ends of the two temperature probes extend through the side wall of the cylinder to the center of the water inlet chamber 32 and the water outlet chamber 18, respectively, so as to obtain the real-time water temperature of the water inlet chamber 32 and the water outlet chamber 18 more accurately.

[0037] In this embodiment, when the heating unit is working, the cylinder is horizontally arranged along its length and is connected and fixed to the dishwasher frame 1 by a corresponding fixed base on its exterior. The side wall at the bottom of the cylinder is also provided with a drain bolt 28 that communicates with any of the chambers. When the heating unit is not used for a long time, the water in the cylinder can be drained in time through the drain bolt 28, thereby improving the service life of the device.

[0038] In the description of this application, the references to terms such as "this embodiment," "some embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0039] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An energy-saving dishwasher, comprising a frame (1), wherein a mounting bracket (2) is provided at the rear end of the top of the frame (1), and a cover that can move up and down is connected to the front side of the mounting bracket (2), the cover, the mounting bracket (2) and the upper end of the frame (1) forming a cleaning chamber; a main washing tank (3), a main water inlet pipe, a water pump (4) and a heating unit are provided at the lower end of the frame (1), a lower spray arm (5) is provided in the main washing tank (3), and an upper spray arm (6) is provided at the upper end of the mounting bracket (2), characterized in that: The upper end of the mounting frame (2) is also provided with a steam heat recovery assembly, which includes a first heat exchange coil (7). The first heat exchange coil (7) is bent in a folding manner along the front and rear direction of the frame (1). The water inlet and water outlet of the heat exchange coil are both connected to the mounting frame (2). The mounting frame (2) is also connected with a cover (8) surrounding the heat exchange coil. The lower part of the cover (8) is open to form a steam absorption channel. The water inlet is connected to the main water inlet pipe, and the water outlet passes through the heating unit and the water pump (4) in sequence to connect to the upper spray arm (6) and the lower spray arm (5).

2. The energy-saving dishwasher according to claim 1, characterized in that: The lower end of the frame (1) is also provided with a wastewater heat recovery assembly, which includes a wastewater tank (9) and a second heat exchange coil (10). A wastewater inlet (11) communicating with its inner cavity and a clean water inlet (12) connected to one end of the second heat exchange coil (10) are provided on one side wall of the wastewater tank (9) along its length. A wastewater outlet (13) communicating with its inner cavity and a clean water outlet (14) connected to the other end of the second heat exchange coil (10) are provided on the other side wall of the wastewater tank (9). The outlet end is connected to the clean water inlet (12), the clean water outlet (14) is connected to the heating unit, the wastewater inlet (11) is connected to the overflow port of the water tank, and the wastewater outlet (13) is connected to the external drain.

3. The energy-saving dishwasher according to claim 2, characterized in that: The wastewater tank (9) is also provided with a plurality of fins (15) arranged at intervals along its length. The plurality of fins (15) are used to divide the wastewater tank (9) into a plurality of chambers, and the chambers are interconnected. Each of the fins (15) is provided with a connection hole for the second heat exchange coil (10) to pass through.

4. The energy-saving dishwasher according to claim 3, characterized in that: The wastewater tank (9) includes a box body with an opening at the top. Multiple symmetrical and vertically extending insertion slots are provided on the inner walls of the two side plates in the width direction of the box body. Multiple fins (15) are respectively inserted and fitted into the corresponding insertion slots. The top of the box body is connected to a top plate, and the upper and lower ends of each fin (15) abut against the top plate and the bottom of the box body, respectively.

5. The energy-saving dishwasher according to claim 4, characterized in that: Each pair of adjacent fins (15) has water passage holes (16) that are staggered vertically, and each fin (15) has multiple grooves and / or protrusions on its surface.

6. The energy-saving dishwasher according to claim 2, characterized in that: The second heat exchange coil (10) is one of a spiral coil, a serpentine coil or a loop coil, and the second heat exchange coil (10) is formed by bending a metal corrugated pipe.

7. The energy-saving dishwasher according to any one of claims 1 to 6, characterized in that: The heating unit includes a cylinder and a PTC heating tube (31). The cylinder is divided into an inlet chamber (32), a mixing chamber (17), and an outlet chamber (18) along its length. The side wall of the cylinder is provided with an inlet pipe (19) communicating with the inlet chamber (32) and an outlet pipe (20) communicating with the outlet chamber (18). Adjacent chambers in the inlet chamber (32), mixing chamber (17), and outlet chamber (18) have water passages. The PTC heating tube (31) and the... The cylinder is detachably connected and extends axially to the water inlet chamber (32), the mixing chamber (17), and the water outlet chamber (18); the side wall of the cylinder is also connected to a first detection element (22) and a second detection element (23) for detecting the water temperature of the water inlet chamber (32) and the water outlet chamber (18) respectively; when the water temperature in the water inlet chamber (32) is lower than the first set value, the PTC heating tube (31) starts heating, and when the water temperature in the water outlet chamber (18) is higher than the second set value, the PTC heating tube (31) stops heating.

8. The energy-saving dishwasher according to claim 7, characterized in that: The inner wall of the cylinder is connected to two partitions (24) spaced apart along its length to divide the inner cavity of the cylinder into a water inlet chamber (32), a mixing chamber (17) and a water outlet chamber (18). The middle of each of the two partitions (24) is provided with a first mounting hole for the PTC heating tube (31) to pass through, and each partition (24) is also provided with a plurality of connecting holes (21) to form the water passage.

9. The energy-saving dishwasher according to claim 7, characterized in that: The cylinder includes a hollow circular tube (25), and end caps (26) are connected to both ends of the circular tube (25). A second mounting hole is provided on any one of the end caps (26) for the PTC heating tube (31) to pass through. A connecting flange (27) is connected to one end of the PTC heating tube (31). The connecting flange (27) is detachably connected to the end cap (26) with the second mounting hole.

10. The energy-saving dishwasher according to claim 7, characterized in that: The first detection element (22) and the second detection element (23) are both temperature probes, and the detection ends of the two temperature probes extend through the side wall of the cylinder to the water inlet chamber (32) and the water outlet chamber (18), respectively.

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