Device for preventing reactant heating system from frost cracking

Abstract

The utility model discloses a device for preventing a reactant heating system from frost cracking, which comprises at least one pressure release valve arranged on a coil pipe, the pressure release valve is arranged in an area which is 1 / 3-1 / 2 of the height of the coil pipe, and the pressure release valve is used for enabling circulating water in the coil pipe to flow into a urea box to realize pressure release. According to the utility model, at least one pressure relief valve is arranged at the part, where the cooling is slowest, of the coil pipe and the runner communicated with the coil pipe, so that the pressure of circulating water, namely a heating medium, in the coil pipe and the runner can be released, and the heating system, including the coil pipe, the runner and other parts related to the coil pipe and the runner, is prevented from being frozen and cracked due to freezing and volume expansion of the circulating water.

Description

Technical Field

[0001] The utility model relates to the technical field of a reactant heating system of an internal combustion engine tail gas purification post-processing system, and more specifically, to a device for preventing a reactant heating system from freezing and cracking. Background Art

[0002] The current internal combustion engine exhaust purification system, especially the lean-burn internal combustion engine, such as diesel engine exhaust purification, requires the addition of a reactant, such as a urea aqueous solution reactant (hereinafter referred to as "reactant"), in the exhaust system, i.e., the after-processor, to reduce nitrogen oxides (NOx). The national standard reactant is a 32.5% urea aqueous solution. In engineering applications, the reactant is contained in a urea tank and carried on the vehicle. Under the control of the DCU (after-treatment controller), the urea pump extracts and sprays it into the after-processor, such as the SCR system, according to the vehicle engine operating conditions. However, the above national standard reactant will freeze in cold weather, such as -11°C. Therefore, a heating system is required to heat and thaw the reactant. One of the most common methods is to use the engine cooling circulating water as a heating medium, hereinafter referred to as "circulating water", by arranging a heat exchanger in the urea tank, hereinafter referred to as "coil", and introducing the circulating water into the coil for circulation; in this way, the heat brought by the circulating water from the engine is transferred to the reactant to achieve heating and freezing.

[0003] Figure 1 and Figure 2 This is a schematic diagram of the most common reactant heating system. The heating function of this system is mainly completed by the heating unit, that is, the heat exchanger, commonly known as the coil 100. The above coil is placed in the urea tank 200. There is a urea reactant 220 in the urea tank, and a urea quality (concentration) sensor 240 is arranged at the bottom. The urea tank is connected to the urea tank cover 400 through a buckle 300. A circulating water inlet pipe joint 410 and a circulating water outlet pipe joint 420 are arranged inside (on) the urea tank cover, which are respectively connected to the inlet pipe 110 and the outlet pipe 120 of the coil 100 through the flow channel inside the urea tank cover (not shown in the figure); the inlet pipe joint 410 and the outlet pipe joint 420 are respectively connected to the circulating water supply pipeline and the return pipeline at the engine end (not shown). A switch valve (not shown) is arranged on the circulating water supply pipeline or in the flow channel inside (on) the urea tank cover 400. In this way, when the reactants in the urea tank need to be heated, the DCU (not shown) can open the switch valve so that the circulating water can continuously flow into the coil 100 to achieve heat exchange, transfer the heat of the circulating water to the reactants, and heat and thaw them.

[0004] Under normal circumstances, the circulating water in the engine is antifreeze liquid and will not freeze in cold weather. However, in the market, many users do not use antifreeze, but directly use natural water, such as tap water. Water can freeze when the temperature is below 0℃. When the circulating water freezes, the volume expands, causing the coil, especially the connection between the coil and the urea tank cover or the flow channel inside the urea tank cover to swell and crack, commonly known as freeze cracking.

[0005] The main technical problem to be solved by the present application is to prevent the above-mentioned freezing and cracking phenomenon from occurring. To this end, the present application discloses the following technical solutions. Utility Model Content

[0006] One purpose of the utility model is to provide a device for preventing a reactant heating system from freezing and cracking. At least one pressure release valve is arranged at the position where the coil and the flow channel connected thereto cool the slowest, so as to release the pressure of the circulating water, i.e., the heating medium, in the coil and the flow channel, and prevent the heating system (including the coil and the flow channel and other parts related thereto) from freezing and cracking due to the freezing and volume expansion of the circulating water.

[0007] In order to solve the above technical problems, the utility model provides a device for preventing the freezing and cracking of the reactant heating system, including at least one pressure relief valve arranged on the coil, which is arranged in the area of ​​1 / 3 to 1 / 2 of the coil height, and the pressure relief valve is used to flow the circulating water in the coil into the urea tank to achieve pressure relief.

[0008] Preferably, two pressure relief valves are provided, which are respectively arranged on the liquid inlet pipe and the liquid outlet pipe of the coil.

[0009] Preferably, the pressure relief valve on the liquid inlet pipe is arranged at a height of 1 / 3 to 1 / 2 of the liquid inlet pipe, and the pressure relief valve on the liquid outlet pipe is arranged on a straight pipe of the coil close to the spiral pipe.

[0010] Preferably, a pressure relief valve is provided on the coil within the liquid level range of 10-20% of the reactant, which is provided on the spiral tube of the coil and is also used to release the circulating water in the coil into the urea tank to achieve pressure relief.

[0011] Preferably, at least one pressure relief valve is further provided on the urea tank cover, which is used to discharge the circulating water in the circulating water flow channel inside the urea tank cover to the outside.

[0012] Preferably, the pressure relief valve on the urea tank cover includes a hollow shell and a valve core and a spring arranged in the shell, the shell has two openings that respectively penetrate the outside and the circulating water channel, and the valve core blocks the opening that penetrates the circulating water channel through the spring.

[0013] Preferably, a pressure relief hole is provided on the coil at a position corresponding to the pressure relief valve, and the pressure relief valve has an elastic structure, which is sealed at the pressure relief hole and deforms when the design pressure is exceeded to leak out of the pressure relief hole to achieve liquid overflow to the outside of the coil to achieve pressure relief.

[0014] Preferably, the pressure relief valve is an elastic O-ring or sleeve, and its sealing sleeve is arranged at the pressure relief hole of the coil;

[0015] Or the pressure relief valve is a sheet-shaped plug, which is elastic and sealed at the pressure relief hole, and the sheet-shaped plug is fixed by a fixing member; the fixing member is an upper fixing ring and a lower fixing ring arranged at the upper and lower ends of the sheet-shaped plug, or a fixing strip arranged at the left and right ends of the sheet-shaped plug;

[0016] Or the sheet-shaped plug is rigid, and at least one of the corresponding upper fixing ring or lower fixing ring is elastic, or at least one of the corresponding fixing strips is elastic.

[0017] Preferably, the O-ring, sleeve or sheet-shaped plug has a boss which extends into the pressure relief hole.

[0018] Preferably, the top and bottom of the O-ring, sleeve or sheet-shaped plug are provided with limiting members, and preferably, the limiting members are limiting rings sleeved on the coil or limiting blocks fixed on the coil.

[0019] The utility model at least has the following beneficial effects:

[0020] 1. The utility model arranges at least one pressure release valve at the slowest cooling position of the coil and the flow channel connected thereto, so as to release the pressure of the circulating water, i.e., the heating medium, in the coil and the flow channel, and prevent the heating system (including the coil and the flow channel and other parts related thereto) from being frozen and cracked due to the freezing and volume expansion of the circulating water.

[0021] 2. The utility model uses a simple pressure relief valve structure to set it at different positions according to different environments, and it is always set at the place where the heating medium is last frozen. In addition, a pressure relief valve is also set on the urea tank cover to prevent the reactant heating system from freezing and cracking in all directions.

[0022] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a schematic diagram of the structure of the most common reactant heating system mentioned in the background technology of the utility model, a schematic diagram of a heating system that uses a heating medium, namely engine cooling circulating water (hereinafter referred to as "circulating water") to heat the SCR urea reactant, wherein there are more reactants in the urea tank, namely the liquid level is higher.

[0024] Figure 2 This is a schematic diagram of the structure of the most common reactant heating system mentioned in the background technology of the present utility model, in which there are fewer reactants in the urea tank, that is, the liquid level is low.

[0025] Figure 3 Two pressure relief valves are installed on the coil 100 of the utility model: one is on the liquid inlet pipe 110, namely the pressure relief valve 500; and the other is on the liquid outlet pipe 120, namely the pressure relief valve 600, both of which are located in the area III, namely the place where ice is formed last.

[0026] Figure 4 The utility model coil 100 is equipped with three pressure relief valves. Figure 3 The difference is that a pressure relief valve 700 is added to the bottom spiral pipe of the coil 100 .

[0027] Figure 5 According to the utility model, a one-way valve (pressure relief valve) is installed on the upper part of the circulating water flow channel inside (on) the urea tank cover 400; the pressure relief valve has a shell 430, and the shell has two holes, one hole 440 is connected to the circulating water flow channel (coil 100 and liquid inlet pipe 410); the other hole 450 is connected to the outside of the urea tank cover; the shell 430 has a valve core 560 and a spring 470 built in.

[0028] Figure 6 The utility model is a Figure 5 A similar device, except that the pressure relief valve is installed in a different position and direction, and part of the flow path of the circulating water itself is used as the valve housing.

[0029] Figures 7-8 The utility model is a simple pressure relief valve structure: a pressure relief hole 510 is opened on the coil 100, and then an elastic O-ring 520 is put on the coil to block the pressure relief hole, and the installation and pressure relief state diagrams are respectively shown.

[0030] Figures 9-10 Another simple pressure relief valve structure of the utility model is as follows: a pressure relief hole 510 is opened on the coil 100, and then an elastic sleeve 520 is put on the coil to block the pressure relief hole, as shown in the installation and pressure relief state diagrams respectively.

[0031] Figures 11-12The utility model is a pressure relief valve structure: a pressure relief hole 510 is opened on the coil 100, and an elastic sheet 520 blocks the pressure relief hole. The plug 520 is fixed to the coil 100 by fixing rings 530 and 540, and the fixing rings 530 and 540 can also be the same part; the installation and pressure relief state diagrams are respectively shown.

[0032] Figures 13-14 The utility model is a Figures 11-12 Similar to the pressure relief valve structure: the difference is that the plug 520 does not deform, and the fixing rings 530 and 540 have elastic deformation, such as O-rings; the installation and pressure relief state diagrams are respectively shown.

[0033] Figures 15-16 The structural details of a valve core 520 of the utility model are as follows: a boss extends into the pressure relief hole so that the valve core 520 can automatically and accurately reset when it moves left and right to avoid sliding up and down; two different forms of the boss are shown respectively.

[0034] Fig.17 This is a relatively complex structural detail of the pressure relief valve of the utility model: limit rings 550 are arranged at the upper and lower ends of the valve to prevent the pressure relief valve from sliding up and down. DETAILED DESCRIPTION

[0035] In order to better understand the purpose, structure and function of the utility model, the utility model is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement it according to the description.

[0036] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0037] The present application discloses a device that utilizes a pressure relief valve to prevent a reactant heating system, especially utilizes the internal combustion engine cooling water (circulating water) circulation to prevent the reactant of its post-treatment system, such as SCR urea reactant, from being frozen and cracked due to the freezing of the above-mentioned circulating water. At least one one-way valve, i.e., a pressure relief valve, is arranged at a location on the flow channel through which the above-mentioned circulating water freezes relatively late. When the circulating water freezes and expands in volume, and the internal pressure of the circulating water flow channel exceeds the normal working pressure, the above-mentioned pressure relief valve can be forcibly opened to allow the circulating water to flow out and release the pressure, thereby preventing the circulating water flow channel from freezing and cracking.

[0038] Example 1

[0039] Figure 3 and Figure 4 A urea reactant heating system is shown. The system is mainly composed of a heat exchanger, namely a coil 100. The coil is connected to the urea tank cover 400 through a buckle 300 to form a component, commonly known as a heating system, also known as a sensor component, because in actual applications, it also includes a reactant level sensor (not shown) and a quality sensor 240 ( Figure 1 ) is installed together with it.

[0040] The above heating system is also connected to the urea tank via a buckle 300 ( Figures 1-2 ), so that the coil 100 is actually in the urea tank 200, partially or completely immersed in the reactant 220. The liquid inlet pipe 110 and the liquid outlet pipe 120 of the coil 100 are connected to the liquid inlet pipe joint 410 and the liquid outlet pipe joint 420 through the flow channel inside the urea tank cover 100 ( Figure 1 ). The above-mentioned circulating water inlet pipe joint and outlet pipe joint are respectively connected to the water supply end and return end of the engine cooling circulating water. A switch valve (not shown) is generally arranged on the circulating water liquid path. In this way, when necessary, the valve is opened, and the circulating water will continuously transfer the heat of the circulating water to the reactant through the coil to achieve heating and thawing of the reactant.

[0041] When the engine is shut down, the after-treatment system stops working, the above-mentioned circulating water heating system stops working, and the vehicle is placed in a cold environment, the temperature inside and outside the urea tank begins to drop. That is, in cold weather, the above-mentioned heating system will cool down along with the ambient temperature. At this time, the reactants in the urea tank cool down the slowest (latest) because their latent heat is much greater than that of the air. The time for the above-mentioned circulating water to cool down and freeze is different in different places (regions) inside and outside the urea tank and above and below. The applicant of this application, based on finite element simulation calculations and experimental verification results, based on finite element simulation of the system and actual measurement results, divides this application into the following four regions according to the order of cooling of each part, namely, Figure 1 and Figure 3The cooling order is: area I, area II, area IV, area III, that is, the circulating water in the coil in area III is the last to freeze.

[0042] When the circulating water is not antifreeze but pure water, the circulating water will freeze itself in the cold winter and expand in volume, causing the internal pressure of the coil 100 and other circulating water channels to increase or even rupture.

[0043] In order to avoid the rupture of the coil and other circulating water channels connected thereto, the present application discloses a method of pressure relief, such as Figures 3-4 As shown, in area III, ie, the final cooling and freezing area, two pressure relief valves 500 and 600 are arranged on the liquid inlet pipe 110 and the liquid outlet pipe 120 of the coil, respectively.

[0044] After a lot of experiments, the applicant found that arranging the pressure relief valve in area III can achieve a very ideal anti-freeze cracking effect; and the most ideal installation position of the pressure relief valve should be near the middle of area III. Obviously, the height and range of the area III will vary with the liquid level of the reactant in the urea tank. Figures 1-2 As shown. In general, region III is approximately located at 1 / 3 to 1 / 2 of the height of the entire coil 100. In practical applications, for ease of installation, preferably, the pressure relief valve 600 can be installed on the straight pipe closest to the spiral pipe ( Figures 3-4 ); if convenient, the pressure relief valve 500 is preferably arranged in the middle of the region III, generally about 1 / 3 to 1 / 2 of the height of the straight pipe 110, which is the most ideal ( Figures 3-4 ).

[0045] The applicant has also found through a large number of experiments that the effect of installing the same pressure relief valve in any other area, that is, not in area III, is far less than that in area III. The reason is that other areas freeze before area III, so that the pressure relief hole of the pressure relief valve is blocked prematurely. When the circulating water in area III freezes, it cannot continue to release pressure, which may still cause freezing and cracking damage, especially when the coil structure is large and long (high) or the reactant in the urea tank is full ( Figure 1 and Figure 3 ).

[0046] Although the above results have been proven to be very ideal in a large number of experiments, they are only applicable to the state where the liquid level of the reactant in the urea tank is relatively normal, that is, the liquid level in the urea tank is at least 30% ( Figure 1 and Figure 3 ). When the liquid level of the reactant in the urea tank is extremely low, for example, less than 30%, region III moves downward as the liquid level decreases, so that region IV disappears, leaving only regions I to III ( Figure 2 and Figure 4 ), the order of freezing is: I, II, III. Obviously, if Figure 4 As shown, the two pressure relief valves 500 and 600 arranged on the straight pipe above the spiral pipe of the present application both fall into region II, and not in region III which freezes last. The applicant found in the experiment that at this time, although the coil and the urea tank cover and their joints were not frozen and cracked, the coil itself was obviously deformed. This is because the pressure relief valves 500 and 600 arranged in region II lost their pressure relief function due to freezing earlier than the coils in region III, resulting in the inability to release the internal pressure of the coils in region III when they freeze, resulting in severe deformation, causing the entire coil to twist. If this relatively serious twisting deformation occurs repeatedly, it may cause the coil itself to rupture or the junction of the coil 100 and the urea tank cover 400 to detach.

[0047] In order to ensure that the coil is sufficiently and continuously relieved of pressure during the entire freezing process in the special case where the reagent level in the urea tank is extremely low, and to minimize the deformation of the coil, as an option, the present application adds a pressure relief valve 700 at a convenient location near the bottom of the coil, preferably on the spiral tube, such as Figure 4 In this way, even if the pressure relief valves 500 and 600 are frozen, the pressure relief valve 700 can still continue to release pressure; when the liquid level of the reactant in the urea tank is high, the pressure relief valve 700 falls into the area IV, earlier than the pressure relief valves 500 and 600 freeze, and the pressure relief valves 500 and 600 do not need the pressure relief valve 700 to complete the pressure relief task.

[0048] Considering that when the liquid level of the reagent in the urea tank drops to a certain level, the post-processing OBD system will alarm according to relevant national regulations to remind the driver to add the reagent. Otherwise, when the OBD system reports a reagent empty fault, the vehicle will be torque-limited and cannot operate normally. In this way, we can install the pressure relief valve 700 just near this liquid level or slightly above this liquid level, such as between 10% and 20% of the liquid level.

[0049] At the same time, for the following reasons, the pressure relief valve 700 should preferably also be arranged on the spiral tube. This is because the finite element analysis results show that the deformation of the spiral coil part is the main cause of the deformation of the entire coil. In addition, when the reactant liquid level is high enough, such as when it is significantly higher than the bottom of the coil, it is not ruled out that the bottom of the coil will freeze earlier than the spiral tube, blocking the passage between the liquid inlet pipe and the liquid outlet pipe. In order to ensure the pressure relief of the spiral tube, the pressure relief valve 700 is preferably able to avoid the bottom of the coil, and preferably on the spiral tube close to the bottom. Of course, other devices such as quality sensors, temperature sensors, reactant filters, etc. may also be installed at the bottom of the coil, which is already very crowded.

[0050] In summary, for heating systems with relatively short coils, such as systems with a urea tank volume of less than 30L, two pressure relief valves can be arranged at 1 / 3 to 1 / 2 of the height of the inlet pipe 110 and the outlet pipe 120, respectively. However, in actual engineering applications, for ease of installation, the pressure relief valve can be installed on a straight pipe close to the spiral pipe. Figure 3 shown.

[0051] However, for a heating system with a relatively high (long) coil, such as a system with a urea tank volume greater than 30L, in addition to the two pressure relief valves 500 and 600 arranged above, it is preferred to add a pressure relief valve 700 and arrange it at a position corresponding to 10-20% of the reactant liquid level, preferably, on a spiral tube that is more convenient to arrange.

[0052] Example 2

[0053] Although the applicant has found in the experiment that the pressure relief valve arranged in Example 1 has basically met the anti-freezing cracking effect in most usage conditions, there are some urea tank covers with relatively complex structures, especially those with urea pumps, DCU (post-processing controller) and other devices integrated on the urea tank cover, and in order to heat these devices, many complex circulating water flow channels are arranged in the urea tank cover. In this case, relying solely on the pressure relief valve on the coil sometimes cannot prevent the flow channel inside the urea tank cover from being frozen and cracked.

[0054] In view of this situation, the present application also discloses a pressure relief valve that can be installed in the urea tank cover, at least one pressure relief valve is provided, such as Figures 5-6 As shown. This pressure relief valve is actually also a one-way valve, and its structure can be any one, but they all have the following common features: there is a shell 430, the inner cavity of the shell is connected to the circulating water channel through an opening 440, and is connected to the outside through another opening 450, and there is a valve core 460 blocking the opening 440, and the valve core is supported by a spring 470. In some cases, the shell 430 can be partially or completely composed of the shell of the urea tank cover or other devices integrated in the urea tank cover, such as part of the circulating water channel, the circulating water filter cavity, etc. ( Figure 6 ).

[0055] When the pressure on the valve core 460 exceeds a certain value, the pressure relief valve will be squeezed open (pushed open), allowing the circulating water to overflow to the outside through the opening 440 (overflow hole), thereby achieving a pressure relief effect.

[0056] Example 3

[0057] The pressure relief valve in the above-mentioned embodiments 1-2, especially the pressure relief valve installed on a circular pipe, such as the coil 100, can be provided with an elastic O-ring 520 ( Figure 7 ) or sleeve 520( Fig. 9) blocks the opening 510 (overflow hole or pressure relief hole) on the pipeline to achieve the effect of a one-way valve. When the pressure in the coil 100 exceeds the normal working pressure, the hydraulic pressure pushes the O-ring 520 ( Figure 8 ) or sleeve 520( Fig.10 ) squeeze (push open) to allow the circulating water to flow out, achieving the purpose of pressure relief.

[0058] Example 4

[0059] The pressure relief valve in the above-mentioned embodiments 1-2, especially the pressure relief valve installed on a circular pipe, such as the coil 100, can also be provided with a sheet-shaped plug 520 ( Fig.11 ) blocks the pressure relief hole 510 on the pipeline to achieve the effect of a one-way valve. The plug is fixed to the coil by a certain structure, such as an upper fixing ring 530 and a lower fixing ring 540, at the upper and lower ends, or at the left and right fixing strips at the left and right ends (not shown in the figure). When the pressure in the coil 100 exceeds the normal working pressure, the hydraulic pressure forcibly squeezes and deforms the plug 520 ( Fig.12 ) allows the circulating water to overflow outside the coil to achieve the purpose of pressure relief.

[0060] Example 5

[0061] Another form of the pressure relief valve in the above-mentioned embodiment 4: In this case, the plug 520 is a rigid body, such as a rigid sheet plug, and does not deform, but at least one of the fixing rings 530 and 540 has elasticity, such as a spring or an O-ring ( Fig.13 ); or at least one of the fixing strips is elastic. When the pressure in the coil 100 exceeds the normal working pressure, the hydraulic pressure causes the fixing ring to deform ( Fig.14 ), so that the circulating water overflows to the outside of the coil to achieve the purpose of pressure relief.

[0062] Example 6

[0063] All the O-rings or sleeves or sheet-shaped plugs 520 in the above-mentioned embodiments 1 to 5 can preferably have a boss of any shape and size, extending into the pressure relief hole of the coil wall, such as Figures 15-16 As shown, the plug 520 can automatically reset after each overflow task is completed to prevent the plug from sliding up and down.

[0064] Example 7

[0065] In the above embodiments 1 to 6, in order to further prevent the O-ring or sleeve or sheet plug 520 from sliding up and down on the coil, as an option, a stop ring 550 ( Fig.17 ), or it can be a limit block fixed on the coil.

[0066] The cross-sections of all the rings, loops and the like in the above-mentioned implementation cases can be of any shape, not limited to circular, square, rectangular and the like.

[0067] In all the above implementation cases, any case where circulating water overflows into the urea tank will more or less dilute the reactants in the urea tank. The applicant has measured in the experiment that each time the circulating water is completely frozen, 2 to 9 mL of circulating water overflows into the urea tank (10 to 45 L urea tank), which means that 0.02% dilution occurs each time. In general, vehicles are filled with urea at least once a month. If the vehicle is completely frozen once a night on average, a cumulative dilution of 0.6% will occur in 30 days. Therefore, in general, this dilution can be completely ignored.

[0068] In addition, if necessary, the DCU can compensate and correct the reactant consumption according to the data read from the reactant quality (concentration) sensor 240, so that the SCR post-treatment effect is not affected by the pressure relief device and method of the present application. For example, if it is found that the urea in the urea tank is diluted by 1%, the urea injection amount can be increased by 1% to achieve the same post-treatment effect.

[0069] Finally, in order to prevent the impurities brought by the circulating water from affecting the cleanliness of the reactants in the urea tank, a filter screen (not shown) is configured for all circulating water inlet pipe interfaces to ensure the cleanliness of the circulating water entering the above-mentioned heating system. Moreover, the inlet pipe and the outlet pipe of the circulating water coil part in this application are relative and interchangeable. That is to say, the flow direction of the circulating water can be changed in the coil, the outlet pipe can become the inlet pipe, and the inlet pipe can become the outlet pipe.

[0070] It can be understood that the present invention is described by some embodiments, and those skilled in the art know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation mode. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, other modifications can be easily realized. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the illustrations shown and described here.

Claims

1. A device for preventing a reactant heating system from freezing and cracking, characterized in that: It includes at least one pressure relief valve arranged on the coil, which is arranged in the area of ​​1 / 3 to 1 / 2 of the coil height. The pressure relief valve is used to release the circulating water in the coil into the urea tank to achieve pressure relief.

2. The device for preventing the freezing and cracking of the reactant heating system according to claim 1, characterized in that: Two pressure relief valves are provided, which are respectively arranged on the liquid inlet pipe and the liquid outlet pipe of the coil.

3. The device for preventing the freezing and cracking of the reactant heating system according to claim 2, characterized in that: The pressure relief valve on the liquid inlet pipe is arranged at a height of 1 / 3 to 1 / 2 of the liquid inlet pipe, and the pressure relief valve on the liquid outlet pipe is arranged on a straight pipe of the coil close to the spiral pipe.

4. The device for preventing the freezing and cracking of the reactant heating system according to claim 2, characterized in that: A pressure relief valve is also provided on the coil within the liquid level range of 10-20% of the reactant. The pressure relief valve is provided on the spiral tube of the coil and is also used to discharge the circulating water in the coil into the urea tank to achieve pressure relief.

5. The device for preventing a reactant heating system from freezing and cracking according to any one of claims 1 to 4, characterized in that: At least one pressure relief valve is also provided on the urea tank cover, which is used to discharge the circulating water in the circulating water flow channel inside the urea tank cover to the outside.

6. The device for preventing the freezing and cracking of the reactant heating system according to claim 5, characterized in that: The pressure relief valve on the urea tank cover includes a hollow shell and a valve core and a spring arranged in the shell. The shell has two openings that respectively penetrate the outside and the circulating water flow channel. The valve core blocks the opening that penetrates the circulating water flow channel through the spring.

7. The device for preventing a reactant heating system from freezing and cracking according to any one of claims 1 to 4, characterized in that: A pressure relief hole is provided on the coil corresponding to the position where the pressure relief valve is provided. The pressure relief valve has an elastic structure, which is sealed at the pressure relief hole and deforms when the design pressure is exceeded to leak out of the pressure relief hole to enable liquid to overflow to the outside of the coil to achieve pressure relief.

8. The device for preventing the freezing and cracking of the reactant heating system according to claim 7, characterized in that: The pressure relief valve is an elastic O-ring or sleeve, and its sealing sleeve is arranged at the pressure relief hole of the coil; Or the pressure relief valve is a sheet-shaped plug, which is elastic and sealed at the pressure relief hole, and the sheet-shaped plug is fixed by a fixing member; the fixing member is an upper fixing ring and a lower fixing ring arranged at the upper and lower ends of the sheet-shaped plug, or a fixing strip arranged at the left and right ends of the sheet-shaped plug; Or the sheet-shaped plug is rigid, and at least one of the corresponding upper fixing ring or lower fixing ring is elastic, or at least one of the corresponding fixing strips is elastic.

9. The device for preventing the freezing and cracking of the reactant heating system according to claim 8, characterized in that: The O-ring, sleeve or sheet-shaped plug all have a boss which extends into the pressure relief hole.

10. The device for preventing a reactant heating system from freezing and cracking as claimed in claim 8, characterized in that: The top and bottom of the O-ring, sleeve or sheet-shaped plug are provided with limiting pieces, and the limiting pieces are limiting rings sleeved on the coil or limiting blocks fixed on the coil.

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