A waste heat recovery method and apparatus based on steam injection

Abstract

This invention relates to the field of waste heat recovery technology, and more particularly to a waste heat recovery method and apparatus based on steam jetting. The method includes: monitoring the flow rate and temperature of cold water in a water heater using flow sensors and temperature sensors respectively; preheating the cold water using a heater; and raising the water temperature to a standard temperature using a waste heat recovery heat exchanger; introducing the hot water at the standard temperature into the mixing chambers of several steam jets; drawing different volumes of cold water into different mixing chambers to output hot water at different temperatures; and discharging the hot water at different temperatures from the nozzles of each steam jet; determining the stability of waste heat recovery based on the average delay time of the water heater's control response; adjusting the heating time interval of the water heater if the stability of waste heat recovery does not meet the requirements; and adjusting the injection pressure difference of the steam jets if the control accuracy does not meet the requirements. This invention improves the stability of waste heat recovery.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology, and in particular to a waste heat recovery method and apparatus based on steam injection. Background Technology

[0002] In existing technologies, traditional water heaters have many shortcomings in water temperature control. Some simple water heaters only have basic heating functions and cannot flexibly adjust the water temperature according to actual water usage and user needs, often resulting in water temperatures that are too high or too low, seriously affecting the user experience. While some slightly more complex water heaters can adjust the water temperature to a certain extent, the control methods they use are relatively crude and cannot achieve precise temperature control. With the improvement of people's living standards and the continuous improvement of their requirements for hot water use, the demand for waste heat recovery devices is growing. Waste heat recovery devices must not only be able to meet the hot water needs in different scenarios, but also have precise temperature control capabilities to ensure a stable output of hot water at the user's desired temperature under various operating conditions.

[0003] Chinese Patent Publication No. CN105277004A discloses a two-step waste heat recovery device and method for high-temperature molten slag. The method includes: First, using saturated steam as the injection medium, the saturated steam is introduced into a jet granulator, which jets and granulates the high-temperature molten slag into slag particles. During the granulation process, the saturated steam exchanges heat with the high-temperature molten slag to generate superheated steam, achieving high-grade waste heat recovery. Second, the granulated slag particles, before solidification, fall into a water slag pool for water quenching, achieving low-grade waste heat recovery during the water quenching process. It is evident that the aforementioned two-step waste heat recovery device and method for high-temperature molten slag suffer from a problem: minerals in the water form scale during heating, which gradually deposits on the nozzle of the steam jet granulator, causing blockage and extending the control response time, thus reducing the stability of waste heat recovery. Summary of the Invention

[0004] To address this issue, the present invention provides a waste heat recovery method and apparatus based on steam jetting, which overcomes the problem in the prior art where minerals in the water form scale during the heating process, which gradually deposits on the nozzle of the steam jetting, causing blockage of the steam jetting and resulting in prolonged control response time and decreased stability of waste heat recovery.

[0005] To achieve the above objectives, the present invention provides a waste heat recovery method based on steam jetting, comprising: monitoring the cold water flow rate and water temperature in a water heater using flow sensors and temperature sensors respectively; preheating the cold water using a heater and raising the water temperature to a standard water temperature using a waste heat recovery heat exchanger; introducing the hot water at the standard water temperature into the mixing chambers of several steam jets; drawing different volumes of cold water into different mixing chambers to output hot water at different temperatures; the hot water at different temperatures being discharged from the nozzles of each steam jet; acquiring the response delay time of the water heater control within several control cycles; determining the stability of waste heat recovery based on the average delay time of the water heater control response; if the stability of waste heat recovery does not meet the requirements, adjusting the heating time interval of the water heater, or determining the control accuracy of the water heater ejector temperature variation based on the fluctuation range of the water flow rate of the water heater; if the control accuracy does not meet the requirements, adjusting the ejector pressure difference of the steam jets, or adjusting the heating power of the water heater based on the rate of increase of the water temperature in the water heater.

[0006] Furthermore, the system includes connecting several steam ejectors via connecting valves before the operation of several steam ejectors.

[0007] Further, determining the stability of the waste heat recovery includes:

[0008] The average delay time of the water heater's control response is compared with the preset first delay time;

[0009] If the average delay time of the water heater's control response is greater than the preset first delay time, then the stability of waste heat recovery is determined to be unsatisfactory.

[0010] Furthermore, determining the precision of the water heater's ejector temperature control includes:

[0011] The average delay time of the water heater control response is compared with the preset first delay time and the preset second delay time, respectively;

[0012] If the average delay time of the water heater's control response is greater than the preset first delay time and less than or equal to the preset second delay time, it is preliminarily determined that the control accuracy of the water heater's ejector temperature change does not meet the requirements, and the control accuracy of the water heater's ejector temperature change is determined based on the fluctuation range of the water heater's outlet flow rate.

[0013] Furthermore, adjusting the heating time interval of the water heater includes:

[0014] The average delay time of the water heater control response is compared with the preset second delay time;

[0015] If the average delay time of the water heater's control response is greater than the preset second delay time, then the heating time interval of the water heater will be increased.

[0016] The increase in the heating time interval of the water heater is determined by the difference between the average delay time of the water heater's control response and the preset second delay time.

[0017] Furthermore, adjusting the ejector pressure differential of the steam ejector includes:

[0018] The fluctuation range of the water flow rate of the water heater is compared with the preset first fluctuation range and the preset second fluctuation range respectively;

[0019] If the fluctuation range of the water flow rate of the water heater is greater than the preset first fluctuation range, it is determined that the control accuracy of the water heater's ejector temperature regulation does not meet the requirements.

[0020] If the fluctuation range of the water flow rate of the water heater is greater than the preset first fluctuation range and less than or equal to the preset second fluctuation range, then the injection pressure difference of the steam ejector is increased.

[0021] If the fluctuation range of the water flow rate of the water heater is greater than the preset second fluctuation range, it is initially determined that the sensitivity of the water heater temperature adjustment does not meet the requirements, and the sensitivity of the water heater temperature adjustment is determined according to the rate of increase of the water temperature in the water heater.

[0022] Furthermore, the increase in the ejector pressure difference of the steam ejector is determined by the difference between the fluctuation range of the water flow rate of the water heater and a preset first fluctuation range.

[0023] Furthermore, adjusting the heating power in the water heater includes:

[0024] Compare the rate at which the water temperature rises in the water heater with the preset rate of temperature rise;

[0025] If the rate of increase of water temperature in the water heater is less than the preset rate of increase, it is determined that the sensitivity of the water heater temperature adjustment does not meet the requirements, and the heating power of the water heater is increased.

[0026] Furthermore, the increase in the heating power of the water heater is determined by the difference between the preset rate of increase and the rate of increase of the water temperature in the water heater.

[0027] The present invention also provides a waste heat recovery device based on steam injection, comprising:

[0028] Water heater casing;

[0029] The heating module, which is located inside the outer casing of the water heater, is used to heat cold water. It includes a water tank for storing the cold water, a heater connected to the water tank for heating the cold water to output hot water, and a waste heat recovery heat exchanger connected to the water tank for further heating the hot water.

[0030] An ejector module, which is connected to the heating module, is used to mix the further heated hot water into hot water of different temperatures through several steam ejectors and then discharge it. It includes several mixing chambers for mixing the cold water and the hot water to output hot water of different temperatures and several nozzles connected to the mixing chambers for discharging the hot water of different temperatures.

[0031] The detection module, which is connected to the heating module, includes a temperature sensor connected to the water tank for detecting the water temperature in the water tank and a flow sensor connected to the outlet of the water tank for detecting the outflow rate of the water.

[0032] The display module is connected to the outer casing of the water heater and is used to display water temperature information.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The method of the present invention adjusts the heating time interval of the water heater based on the average delay time of the water heater's control response. Since minerals in the water form scale during the heating process, which gradually deposits on the nozzle of the steam ejector, causing blockage and thus prolonging the control response time, increasing the heating time interval of the water heater reduces the speed and extent of scale formation at high temperatures, thereby slowing down the scale deposition rate at the steam ejector nozzle and preventing further deterioration of the blockage. This helps maintain the normal working condition of the steam ejector, thus shortening the control response time. The method also adjusts the ejector pressure difference of the steam ejector based on the fluctuation range of the water flow rate of the water heater. Due to prolonged use, the electrical current in the flow sensor... Loose solder joints on the circuit board caused signal transmission interruption, resulting in inaccurate data transmission to the control unit. Increasing the ejector pressure differential of the steam ejector allows for more powerful extraction of cold water, increasing the amount of cold water ejected and thus better mixing with hot water, lowering the hot water temperature. The heating power of the water heater is adjusted according to the rate of temperature increase in the water unit. Because scale may form inside the waste heat recovery heat exchanger in the water heater, increasing thermal resistance and reducing heat transfer efficiency, the temperature rise of the hot water before entering the ejector mixing stage is insufficient, resulting in insignificant temperature changes. Increasing the heating power of the water heater increases the heat generated per unit time, compensating for the heat loss due to increased thermal resistance, allowing the hot water to obtain more heat, thereby raising the temperature and improving the stability of waste heat recovery.

[0034] Furthermore, the method of the present invention adjusts the heating time interval of the water heater by setting a preset first delay time and a preset second delay time. Since minerals in the water will form scale during the heating process and gradually deposit on the nozzle of the steam ejector, causing the steam ejector to become blocked, the control response time is prolonged. By increasing the heating time interval of the water heater, the speed and extent of scale formation of minerals in the water at high temperature can be reduced, thereby slowing down the deposition rate of scale at the nozzle of the steam ejector and preventing the blockage of the steam ejector from worsening. This helps to maintain the normal working state of the steam ejector, thereby shortening the control response time and further improving the stability of waste heat recovery.

[0035] Furthermore, the method of the present invention adjusts the ejector pressure difference of the steam ejector by setting a preset first fluctuation amplitude and a preset second fluctuation amplitude. Due to prolonged use, the solder joints of the circuit board in the flow sensor become loose, causing signal transmission interruption and resulting in some data not being accurately transmitted to the control unit, leading to inaccurate data. By increasing the ejector pressure difference of the steam ejector, the steam ejector can more powerfully draw cold water, increasing the ejection volume of cold water, thereby mixing it better with hot water, reducing the hot water temperature, and further improving the stability of waste heat recovery.

[0036] Furthermore, the method of the present invention adjusts the heating power of the water heater by setting a preset rise rate. Since scale may form inside the waste heat recovery heat exchanger of the water heater, increasing thermal resistance and reducing heat transfer efficiency, the temperature rise of the hot water before entering the ejector mixing is insufficient, resulting in insignificant temperature changes. By increasing the heating power of the water heater, the heat generated per unit time can be increased to compensate for the heat loss due to increased thermal resistance, allowing the hot water to obtain more heat, thereby increasing the temperature and further improving the stability of waste heat recovery. Attached Figure Description

[0037] Figure 1 This is an overall flowchart of the waste heat recovery method based on steam injection according to an embodiment of the present invention;

[0038] Figure 2 This is an overall structural block diagram of the waste heat recovery device based on steam injection according to an embodiment of the present invention;

[0039] Figure 3 This is a logic flowchart illustrating the process of adjusting the heating time interval of a water heater using a waste heat recovery method based on steam injection, as described in an embodiment of the present invention.

[0040] Figure 4 This is a logic flowchart illustrating the process of adjusting the ejector pressure difference of a steam ejector in a waste heat recovery method based on steam injection according to an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0042] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0043] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0044] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] Please see Figure 1 , Figure 2 , Figure 3 as well as Figure 4 The diagrams shown are, respectively, an overall flowchart, an overall structural block diagram, a logic flowchart for adjusting the heating time interval of the water heater, and a logic flowchart for adjusting the ejector pressure difference of the steam ejector, all representing embodiments of the waste heat recovery method and apparatus based on steam injection according to embodiments of the present invention. The present invention provides a waste heat recovery method based on steam injection, comprising:

[0046] Step S1: Use a flow sensor and a temperature sensor to monitor the cold water flow and temperature in the water heater, use a heater to preheat the cold water, and use a waste heat recovery heat exchanger to raise the water temperature to the standard water temperature.

[0047] Step S2: The hot water at the standard water temperature is introduced into the mixing chamber of several steam ejectors, and different volumes of cold water are drawn into different mixing chambers to output hot water at different temperatures. The hot water at different temperatures is discharged from the nozzles of each steam ejector.

[0048] Step S3: Obtain the response delay duration of the water heater control within several control cycles;

[0049] Step S4: Determine the stability of waste heat recovery based on the average delay time of the water heater's control response;

[0050] Step S5: If the stability of the waste heat recovery does not meet the requirements, the heating time interval of the water heater is adjusted, or the control accuracy of the water heater ejector temperature is determined based on the fluctuation range of the water flow rate of the water heater.

[0051] Step S6: If the control precision does not meet the requirements, the ejector pressure difference of the steam ejector is adjusted, or the heating power of the water heater is adjusted based on the rate of increase of the water temperature in the water heater.

[0052] Specifically, the standard water temperature can be set according to the actual situation. For example, a waste heat recovery heat exchanger can be used to raise the water temperature to 85°C.

[0053] Specifically, the process of drawing different volumes of cold water into different mixing chambers to output hot water at different temperatures is as follows: First, hot water at 85°C is introduced into the three mixing chambers. Then, cold water at 10°C is drawn into the first mixing chamber until the temperature of the hot water in the mixing chamber reaches 60°C. Next, cold water at 10°C is drawn into the second mixing chamber until the temperature of the hot water in the mixing chamber reaches 45°C. Finally, cold water at 10°C is drawn into the third mixing chamber until the temperature of the hot water in the mixing chamber reaches 82°C.

[0054] Specifically, the temperature of the hot water mixed in the different mixing chambers can be set according to the actual situation.

[0055] In practice, the method of this invention adjusts the heating time interval of the water heater based on the average delay time of the water heater's control response. Since minerals in the water form scale during heating, which gradually deposits on the nozzles of the steam ejector, causing blockage and thus prolonging the control response time, increasing the heating time interval reduces the rate and extent of scale formation at high temperatures, thereby slowing down the scale deposition rate at the steam ejector nozzles and preventing further blockage. This helps maintain the normal operation of the steam ejector, thus shortening the control response time. The method also adjusts the ejector pressure difference of the steam ejector based on the fluctuation range of the water flow rate. However, prolonged use can cause the solder joints on the circuit board of the flow sensor to loosen. This can lead to signal transmission interruptions, causing some data to be inaccurately transmitted to the control unit, resulting in inaccurate data. By increasing the ejector pressure difference of the steam ejector, the steam ejector can more powerfully draw cold water, increasing the ejection volume of cold water, thereby mixing it better with hot water and lowering the hot water temperature. The heating power of the water heater is adjusted according to the rate of increase of the water temperature in the water heater. Because scale may form inside the waste heat recovery heat exchanger in the water heater, increasing thermal resistance and reducing heat transfer efficiency, the temperature rise of the hot water before entering the ejector mixing is insufficient, resulting in insignificant temperature changes. By increasing the heating power of the water heater, the heat generated per unit time can be increased to compensate for the heat lost due to increased thermal resistance, allowing the hot water to obtain more heat, thereby increasing the temperature and improving the stability of waste heat recovery.

[0056] Specifically, the process includes connecting several steam ejectors via connecting valves before the operation of several steam ejectors.

[0057] Specifically, determining the stability of the waste heat recovery includes:

[0058] Obtain the response delay time of the water heater control within several control cycles, and calculate the average delay time of the water heater control response;

[0059] The average delay time of the water heater control response is compared with a preset first delay time;

[0060] If the average delay time of the water heater's control response is greater than the preset first delay time, then the stability of waste heat recovery is determined to be unsatisfactory.

[0061] Specifically, determining the accuracy of the temperature control of the water heater's ejector valve includes:

[0062] The average delay time of the water heater control response is compared with the preset first delay time and the preset second delay time, respectively;

[0063] If the average delay time of the water heater's control response is greater than the preset first delay time and less than or equal to the preset second delay time, it is preliminarily determined that the control accuracy of the water heater's ejector temperature change does not meet the requirements, and the control accuracy of the water heater's ejector temperature change is determined based on the fluctuation range of the water heater's outlet flow rate.

[0064] It is understandable that the three intervals divided by the preset first delay duration and the preset second delay duration correspond to three different scenarios:

[0065] The first interval is when the average delay time of the water heater's control response is less than or equal to the preset first delay time, which corresponds to the situation where the stability of waste heat recovery meets the requirements.

[0066] The second interval is the average delay time of the water heater control response, which is greater than the preset first delay time and less than or equal to the preset second delay time. The corresponding situation is: due to long-term use, the solder joints of the circuit board in the flow sensor become loose, which causes the signal transmission to be interrupted, resulting in some data not being accurately transmitted to the control unit, resulting in inaccurate data.

[0067] The third interval is when the average delay time of the water heater's control response is greater than the preset second delay time. The corresponding situation is that minerals in the water will form scale during the heating process, which will gradually deposit on the nozzle of the steam ejector, causing the steam ejector to become blocked, thus prolonging the control response time.

[0068] In practice, the preset first delay duration is generally selected in the range of [2s, 4s], and the preset second delay duration is generally selected in the range of [5s, 7s].

[0069] Preferably, the first delay duration is 3 seconds in a preferred embodiment, and the second delay duration is 6 seconds in a preferred embodiment.

[0070] Specifically, the average delay time of the water heater's control response is the ratio of the total delay time of the water heater's control response over several control cycles to the number of control cycles.

[0071] In practice, the method of the present invention determines the stability of waste heat recovery by setting a preset first delay time and a preset second delay time, thereby reducing the impact of inaccurate determination of the stability of waste heat recovery leading to a decrease in the control accuracy of the water heater's ejector temperature, and further improving the stability of waste heat recovery.

[0072] Specifically, adjusting the heating time interval of the water heater includes:

[0073] The average delay time of the water heater control response is compared with the preset second delay time;

[0074] If the average delay time of the water heater's control response is greater than the preset second delay time, then the heating time interval of the water heater will be increased.

[0075] Specifically, the increase in the heating time interval of the water heater is determined by the difference between the average delay time of the water heater's control response and the preset second delay time.

[0076] Specifically, when the difference between the average delay time of the water heater's control response and the preset second delay time is within 2 seconds, the heating time interval of the water heater is increased to 1.1 times the original value. When the difference between the average delay time of the water heater's control response and the preset second delay time exceeds 2 seconds, in addition to increasing to 1.1 times the original value, the heating time interval of the water heater is increased by 0.5 minutes for every 1 second exceeding the original value. For example, if the difference between the average delay time of the water heater's control response and the preset second delay time is 4 seconds, and the current heating time interval of the water heater is 10 minutes, the increased heating time interval of the water heater will be 10 × 1.1 + 0.5 × 2 = 12 minutes.

[0077] In practice, the method of the present invention adjusts the heating time interval of the water heater by setting a preset first delay time and a preset second delay time. Since minerals in the water will form scale during the heating process and gradually deposit on the nozzle of the steam ejector, causing the steam ejector to become blocked, the control response time is prolonged. By increasing the heating time interval of the water heater, the speed and extent of scale formation of minerals in the water at high temperature can be reduced, thereby slowing down the deposition rate of scale at the nozzle of the steam ejector and preventing the blockage of the steam ejector from worsening. This helps to maintain the normal working state of the steam ejector, thereby shortening the control response time and further improving the stability of waste heat recovery.

[0078] Specifically, adjusting the ejector pressure differential of the steam ejector includes:

[0079] Obtain the water flow rate of the water heater within a single cycle and calculate the fluctuation range of the water flow rate of the water heater.

[0080] The fluctuation range of the water flow rate of the water heater is compared with the preset first fluctuation range and the preset second fluctuation range, respectively;

[0081] If the fluctuation range of the water flow rate of the water heater is greater than the preset first fluctuation range, it is determined that the control accuracy of the water heater's ejector temperature regulation does not meet the requirements.

[0082] If the fluctuation range of the water flow rate of the water heater is greater than the preset first fluctuation range and less than or equal to the preset second fluctuation range, then the injection pressure difference of the steam ejector is increased.

[0083] If the fluctuation range of the water flow rate of the water heater is greater than the preset second fluctuation range, it is initially determined that the sensitivity of the water heater temperature adjustment does not meet the requirements, and the sensitivity of the water heater temperature adjustment is determined according to the rate of increase of the water temperature in the water heater.

[0084] It is understandable that the three intervals defined by the preset first fluctuation range and the preset second fluctuation range correspond to three different scenarios:

[0085] The first interval is when the fluctuation range of the water flow rate of the water heater is less than or equal to the preset first fluctuation range, which corresponds to the situation that the control accuracy of the water heater's ejector temperature regulation meets the requirements.

[0086] The second range is when the fluctuation range of the water flow rate of the water heater is greater than the preset first fluctuation range and less than or equal to the preset second fluctuation range. The corresponding situation is: due to long-term use, the solder joints of the circuit board in the flow sensor become loose, resulting in signal transmission interruption, which causes some data to be unable to be accurately transmitted to the control unit, resulting in inaccurate data.

[0087] The third range is when the fluctuation of the water flow rate of the water heater is greater than the preset second fluctuation range. The corresponding situation is that scale may form inside the waste heat recovery heat exchanger in the water heater, increasing the thermal resistance and reducing the heat transfer efficiency, resulting in insufficient temperature rise of the hot water before entering the ejector mixing, thus making the temperature change insignificant.

[0088] In practice, the preset first fluctuation amplitude is generally selected in the range of [0.5L / min, 1.5L / min], and the preset second fluctuation amplitude is generally selected in the range of [2L / min, 3L / min].

[0089] Preferably, the preferred embodiment of the preset first fluctuation range is 1L / min, and the preferred embodiment of the preset second fluctuation range is 2.5L / min.

[0090] Specifically, the fluctuation range of the water flow rate of the water heater is the difference between the maximum and minimum water flow rate of the water heater within a single cycle.

[0091] In practice, the method of the present invention determines the accuracy of the control of the water heater's ejector temperature by setting a preset first fluctuation amplitude and a preset second fluctuation amplitude, thereby reducing the impact of the decrease in the stability of waste heat recovery caused by the inaccuracy in determining the accuracy of the control of the water heater's ejector temperature and further improving the stability of waste heat recovery.

[0092] Specifically, the increase in the ejector pressure difference of the steam ejector is determined by the difference between the fluctuation range of the water flow rate of the water heater and a preset first fluctuation range.

[0093] Specifically, when the difference between the fluctuation range of the water flow rate of the water heater and the preset first fluctuation range is within 1.5 L / min, the ejector pressure difference of the steam ejector increases to 1.2 times the original value. When the difference between the fluctuation range of the water flow rate of the water heater and the preset first fluctuation range exceeds 1.5 L / min, in addition to increasing to 1.2 times the original value, for every 0.5 L / min exceeding the preset first fluctuation range, the ejector pressure difference of the steam ejector increases by 1 kPa. For example, if the difference between the fluctuation range of the water flow rate of the water heater and the preset first fluctuation range is 2.5 L / min, and the current ejector pressure difference of the steam ejector is 20 kPa, the increased ejector pressure difference of the steam ejector will be 20 × 1.2 + 1 × 2 = 26 kPa.

[0094] In practice, the method of the present invention adjusts the ejector pressure difference of the steam ejector by setting a preset first fluctuation amplitude and a preset second fluctuation amplitude. Due to long-term use, the solder joints of the circuit board in the flow sensor become loose, causing signal transmission interruption and some data to be inaccurately transmitted to the control unit, resulting in inaccurate data. By increasing the ejector pressure difference of the steam ejector, the steam ejector can more powerfully draw cold water, increase the ejection volume of cold water, thereby better mixing with hot water, reducing the temperature of hot water, and further improving the stability of waste heat recovery.

[0095] Specifically, adjusting the heating power in the water heater includes:

[0096] Obtain the water temperature in the water heater within a single cycle and calculate the rate of increase of the water temperature in the water heater;

[0097] The rate of increase of water temperature in the water heater is compared with the preset rate of increase;

[0098] If the rate of increase of water temperature in the water heater is less than the preset rate of increase, it is determined that the sensitivity of the water heater temperature adjustment does not meet the requirements, and the heating power of the water heater is increased.

[0099] It is understandable that the two intervals defined by the preset rate of increase correspond to two different scenarios:

[0100] The first interval is when the rate of increase of water temperature in the water heater is less than the preset rate of increase. The corresponding situation is that scale may form inside the waste heat recovery heat exchanger in the water heater, increasing thermal resistance and reducing heat transfer efficiency, resulting in insufficient temperature rise of the hot water before entering the ejector mixing, thus making the temperature change insignificant.

[0101] The second range is when the rate of increase in water temperature in the water heater is greater than or equal to the preset rate of increase, which corresponds to the condition that the sensitivity of the water heater's temperature adjustment meets the requirements.

[0102] In practice, the preset rise rate is generally selected in the range of [2℃ / min, 4℃ / min].

[0103] Preferably, the preset rate of increase is 3°C / min.

[0104] Specifically, the rate of increase of water temperature in the water heater is the ratio of the difference between the water temperature at the end of a single cycle and the water temperature at the beginning of a single cycle to the duration of a single cycle.

[0105] In practice, the method of the present invention determines the sensitivity of the water heater temperature regulation by setting a preset rise rate, thereby reducing the impact of inaccurate determination of the sensitivity of the water heater temperature regulation on the stability of waste heat recovery and further improving the stability of waste heat recovery.

[0106] Specifically, the increase in the heating power of the water heater is determined by the difference between the preset rate of increase and the rate of increase of the water temperature in the water heater.

[0107] Specifically, when the difference between the preset heating rate and the actual water temperature rise rate in the water heater is within 2℃ / min, the heating power of the water heater increases to 1.2 times the original value. When the difference exceeds 2℃ / min, in addition to increasing to 1.1 times the original value, the heating power increases by 0.5kW for every 1℃ / min increase. For example, if the difference between the preset heating rate and the actual water temperature rise rate is 4℃ / min, and the current heating power of the water heater is 5kW, the increased heating power of the water heater will be 5×1.2+0.5×2=7kW.

[0108] In practice, the method of the present invention adjusts the heating power of the water heater by setting a preset rise rate. Since scale may form inside the waste heat recovery heat exchanger of the water heater, increasing thermal resistance and reducing heat transfer efficiency, the temperature rise of the hot water before entering the ejector mixing is insufficient, resulting in insignificant temperature changes. By increasing the heating power of the water heater, the heat generated per unit time can be increased to compensate for the heat loss due to increased thermal resistance, allowing the hot water to obtain more heat, thereby raising the temperature and further improving the stability of waste heat recovery.

[0109] A waste heat recovery device based on steam injection, comprising:

[0110] Water heater casing;

[0111] The heating module, which is located inside the outer casing of the water heater, is used to heat cold water. It includes a water tank for storing the cold water, a heater connected to the water tank for heating the cold water to output hot water, and a waste heat recovery heat exchanger connected to the water tank for further heating the hot water.

[0112] An ejector module is used to mix the further heated hot water into hot water of different temperatures through several steam ejectors and then discharge it. It includes several mixing chambers for mixing the cold water and the hot water to output hot water of different temperatures and several nozzles connected to the mixing chambers for discharging the hot water of different temperatures.

[0113] The detection module, which is connected to the heating module, includes a temperature sensor connected to the water tank for detecting the water temperature in the water tank and a flow sensor connected to the outlet of the water tank for detecting the outflow rate of the water.

[0114] The display module is connected to the outer casing of the water heater and is used to display water temperature information.

[0115] Specifically, the water temperature information includes the current water temperature, the set temperature, and abnormal temperature warnings.

[0116] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A waste heat recovery method based on steam injection, characterized in that, include: The flow rate and temperature of the cold water in the water heater are monitored by a flow sensor and a temperature sensor, respectively. The cold water is initially heated by a heater and the water temperature is raised to the standard temperature by a waste heat recovery heat exchanger. Hot water at the standard water temperature is introduced into the mixing chamber of several steam ejectors, and different volumes of cold water are drawn into different mixing chambers to output hot water at different temperatures. The hot water at different temperatures is discharged from the nozzles of each steam ejector. Obtain the response delay time of the water heater control within several control cycles; The stability of waste heat recovery is determined based on the average delay time of the water heater's control response; If the stability of the waste heat recovery does not meet the requirements, the heating time interval of the water heater shall be adjusted, or the control accuracy of the water heater ejector temperature shall be determined based on the fluctuation range of the water flow of the water heater. If the control precision does not meet the requirements, the ejector pressure difference of the steam ejector is adjusted, or the heating power of the water heater is adjusted based on the rate of increase of the water temperature in the water heater. Determining the stability of the waste heat recovery includes: The average delay time of the water heater's control response is compared with the preset first delay time; If the average delay time of the water heater control response is greater than the preset first delay time, then it is determined that the stability of waste heat recovery does not meet the requirements. Determining the accuracy of the temperature control of the water heater's ejector valve includes: The average delay time of the water heater control response is compared with the preset first delay time and the preset second delay time, respectively; If the average delay time of the water heater's control response is greater than the preset first delay time and less than or equal to the preset second delay time, it is preliminarily determined that the control accuracy of the water heater's ejector temperature change does not meet the requirements, and the control accuracy of the water heater's ejector temperature change is determined based on the fluctuation range of the water heater's outlet flow rate. Adjusting the heating time interval of the water heater includes: The average delay time of the water heater control response is compared with the preset second delay time; If the average delay time of the water heater's control response is greater than the preset second delay time, then the heating time interval of the water heater will be increased. The increase in the heating time interval of the water heater is determined by the difference between the average delay time of the water heater's control response and the preset second delay time. Because minerals in the water form scale during the heating process, which gradually deposits on the nozzles of the steam ejector, causing blockage and extending the control response time. By increasing the heating interval of the water heater, the speed and extent of scale formation by minerals in the water at high temperatures can be reduced, thereby slowing down the deposition rate of scale at the steam ejector nozzles and preventing the blockage from worsening. This helps maintain the normal working condition of the steam ejector and shortens the control response time.

2. The waste heat recovery method based on steam injection according to claim 1, characterized in that, The system also includes connecting several steam ejectors via connecting valves before several steam ejectors are put into operation.

3. The waste heat recovery method based on steam injection according to claim 2, characterized in that, Adjusting the ejector pressure differential of the steam ejector includes: The fluctuation range of the water flow rate of the water heater is compared with the preset first fluctuation range and the preset second fluctuation range respectively; If the fluctuation range of the water flow rate of the water heater is greater than the preset first fluctuation range, it is determined that the control accuracy of the water heater's ejector temperature regulation does not meet the requirements. If the fluctuation range of the water flow rate of the water heater is greater than the preset first fluctuation range and less than or equal to the preset second fluctuation range, then the injection pressure difference of the steam ejector is increased. If the fluctuation range of the water flow rate of the water heater is greater than the preset second fluctuation range, it is initially determined that the sensitivity of the water heater temperature adjustment does not meet the requirements, and the sensitivity of the water heater temperature adjustment is determined according to the rate of increase of the water temperature in the water heater.

4. The waste heat recovery method based on steam injection according to claim 3, characterized in that, The increase in the ejector pressure difference of the steam ejector is determined by the difference between the fluctuation range of the water flow rate of the water heater and the preset first fluctuation range.

5. The waste heat recovery method based on steam injection according to claim 4, characterized in that, Adjusting the heating power in the water heater includes: Compare the rate at which the water temperature rises in the water heater with the preset rate of temperature rise; If the rate of increase of water temperature in the water heater is less than the preset rate of increase, it is determined that the sensitivity of the water heater temperature adjustment does not meet the requirements, and the heating power of the water heater is increased.

6. The waste heat recovery method based on steam injection according to claim 5, characterized in that, The increase in the heating power of the water heater is determined by the difference between the preset rate of increase and the rate of increase of the water temperature in the water heater.

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