Waste heat recovery method and device based on steam injection

Abstract

The invention relates to the technical field of waste heat recovery, in particular to a waste heat recovery method and device based on steam jetting. The method comprises the steps that a flow sensor and a temperature sensor are used for monitoring the flow and the water temperature of cold water in a water heater, and a heater is used for primarily heating the cold water; the waste heat recovery heat exchanger is used for increasing the water temperature to the standard water temperature; the hot water with the standard water temperature is introduced into mixing cavities of a plurality of steam ejectors, cold water with different volumes is sucked into different mixing cavities so as to output hot water with different temperatures, and the hot water with different temperatures is discharged through nozzles of the steam ejectors; determining the stability of waste heat recovery based on the average delay duration of the regulation response of the water heater; if the stability of waste heat recovery does not meet the requirement, the heating time interval of the water heater is adjusted; and if the regulation and control accuracy does not meet the requirement, the injection pressure difference of the steam ejector is adjusted. The waste heat recovery stability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery, and particularly to a waste heat recovery method and device based on steam injection. Background Art

[0002] In the prior art, there are many deficiencies in the water temperature regulation of traditional water heaters. Some simple water heaters only have basic heating functions and cannot flexibly adjust the water temperature according to the actual water usage situation and user needs. Often, the water temperature is too high or too low, seriously affecting the user experience. And some slightly more complex water heaters can adjust the water temperature to a certain extent, but the adopted regulation method is relatively rough and cannot achieve precise temperature control. With the improvement of people's living quality and the continuous increase in the requirements for hot water use, the demand for waste heat recovery devices is growing day by day. The waste heat recovery device should not only be able to meet the hot water requirements in different scenarios, but also have precise temperature regulation capabilities to ensure that hot water meeting the expected temperature of users can be stably output under various working conditions.

[0003] Chinese Patent Publication No.: CN105277004A discloses a two-step waste heat recovery device and waste heat recovery method for high-temperature molten slag. The method includes: in the first step, using saturated steam as the injection medium, introducing the saturated steam into the injection granulator, and the injection granulator sprays and granulates the high-temperature molten slag into slag particles. During the granulation process of the high-temperature molten slag, the saturated steam exchanges heat with the high-temperature molten slag to generate superheated steam, realizing high-grade waste heat recovery; in the second step, the granulated slag particles fall into the water slag pool for water quenching treatment when they have not solidified yet. During the water quenching treatment of the slag particles, low-grade waste heat recovery is realized. It can be seen that the two-step waste heat recovery device and waste heat recovery method for high-temperature molten slag have the problem that the minerals in the water will form scale during the heating process and gradually deposit on the nozzle of the steam injector, resulting in the blockage of the steam injector, the extension of the regulation response time, and thus the decline in the stability of waste heat recovery. Summary of the Invention

[0004] Therefore, the present invention provides a waste heat recovery method and device based on steam injection to overcome the problem in the prior art that the minerals in the water will form scale during the heating process and gradually deposit on the nozzle of the steam injector, resulting in the blockage of the steam injector, the extension of the regulation response time, and thus the decline in the stability of waste heat recovery.

[0005] To achieve the above object, the present invention provides a waste heat recovery method based on steam injection, including: respectively using a flow sensor and a temperature sensor to monitor the cold water flow rate and water temperature in a water heater, using a heater to preliminarily heat the cold water, and using a waste heat recovery heat exchanger to raise the water temperature to a standard water temperature; introducing the hot water at the standard water temperature into the mixing chambers of a plurality of steam ejectors, sucking 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 the respective steam ejectors; obtaining the response delay duration of the water heater regulation within a plurality of regulation cycles; determining the stability of waste heat recovery based on the average delay duration of the water heater regulation response; if the stability of the waste heat recovery does not meet the requirements, adjusting the heating time interval of the water heater, or determining the regulation accuracy of the water heater for ejecting variable temperature based on the fluctuation range of the water outlet flow rate of the water heater; if the regulation accuracy does not meet the requirements, adjusting the ejector pressure difference of the steam ejector, or adjusting the heating power of the water heater based on the water temperature rise rate in the water heater.

[0006] Further, before the operation of a plurality of steam ejectors, it further includes connecting the plurality of steam ejectors through a connecting valve.

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

[0008] Comparing the average delay duration of the water heater regulation response with a preset first delay duration;

[0009] If the average delay duration of the water heater regulation response is greater than the preset first delay duration, it is determined that the stability of the waste heat recovery does not meet the requirements.

[0010] Further, determining the regulation accuracy of the water heater for ejecting variable temperature includes:

[0011] Comparing the average delay duration of the water heater regulation response with the preset first delay duration and a preset second delay duration respectively;

[0012] If the average delay duration of the water heater regulation response is greater than the preset first delay duration and less than or equal to the preset second delay duration, it is preliminarily determined that the regulation accuracy of the water heater for ejecting variable temperature does not meet the requirements, and it is determined whether the regulation accuracy of the water heater for ejecting variable temperature meets the requirements according to the fluctuation range of the water outlet flow rate of the water heater.

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

[0014] Comparing the average delay duration of the water heater regulation response with the preset second delay duration;

[0015] If the average delay duration of the hot water machine control response is greater than the preset second delay duration, increase the heating time interval of the hot water machine;

[0016] Among them, the increase amplitude of the heating time interval of the hot water machine is determined by the difference between the average delay duration of the hot water machine control response and the preset second delay duration.

[0017] Further, adjusting the entrainment pressure difference of the steam ejector includes:

[0018] Compare the fluctuation amplitude of the water outlet flow rate of the hot water machine with the preset first fluctuation amplitude and the preset second fluctuation amplitude respectively;

[0019] If the fluctuation amplitude of the water outlet flow rate of the hot water machine is greater than the preset first fluctuation amplitude, it is determined that the control accuracy of the hot water machine entrainment temperature change does not meet the requirements;

[0020] If the fluctuation amplitude of the water outlet flow rate of the hot water machine is greater than the preset first fluctuation amplitude and less than or equal to the preset second fluctuation amplitude, increase the entrainment pressure difference of the steam ejector;

[0021] If the fluctuation amplitude of the water outlet flow rate of the hot water machine is greater than the preset second fluctuation amplitude, it is initially determined that the sensitivity of the hot water machine temperature regulation does not meet the requirements, and it is determined whether the sensitivity of the hot water machine temperature regulation meets the requirements according to the water temperature increase rate in the hot water machine.

[0022] Further, the increase amplitude of the entrainment pressure difference of the steam ejector is determined by the difference between the fluctuation amplitude of the water outlet flow rate of the hot water machine and the preset first fluctuation amplitude.

[0023] Further, adjusting the heating power in the hot water machine includes:

[0024] Compare the water temperature increase rate in the hot water machine with the preset increase rate;

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

[0026] Further, the increase amplitude of the heating power of the hot water machine is determined by the difference between the preset increase rate and the water temperature increase rate in the hot water machine.

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

[0028] Hot water machine housing;

[0029] A heating module, which is arranged inside the housing of the water heater and is used to heat cold water, 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 ejecting module, which is connected to the heating module and is used to discharge the hot water after further heating as hot water at different temperatures by mixing it through a plurality of steam ejectors, includes a plurality of mixing chambers for mixing the cold water and the hot water to output hot water at different temperatures and a plurality of nozzles connected to the mixing chambers for discharging the hot water at different temperatures;

[0031] A 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 water flow rate;

[0032] A display module, which is connected to the housing of the water heater and is used to display the 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 according to the average delay duration of the water heater's regulation response. Since minerals in the water will form scale during the heating process and gradually deposit on the nozzles of the steam ejectors, resulting in the blockage of the steam ejectors, thus prolonging the regulation response time. By increasing the heating time interval of the water heater, the speed and degree of scale formation by minerals in the water at high temperature can be reduced, thereby slowing down the deposition speed of scale at the nozzles of the steam ejectors and preventing the blockage situation of the steam ejectors from deteriorating further, which helps to maintain the normal working state of the steam ejectors, thereby shortening the regulation response time. The ejecting pressure difference of the steam ejectors is adjusted according to the fluctuation amplitude of the water flow rate of the water heater. Due to the loosening of the solder joints of the circuit board in the flow sensor caused by long-term use, signal transmission is interrupted, resulting in inaccurate transmission of some data to the control unit, leading to inaccurate data. By increasing the ejecting pressure difference of the steam ejectors, the steam ejectors can extract cold water more powerfully, increase the entrainment amount of cold water, so as to mix better with the hot water and reduce the hot water temperature. The heating power of the water heater is adjusted according to the rising rate of the water temperature in the water heater. Since scale may form inside the waste heat recovery heat exchanger in the water heater, the thermal resistance increases, and the heat transfer efficiency decreases, resulting in insufficient temperature rise of the hot water before entering the ejecting and mixing process, so that the temperature change is not obvious. By increasing the heating power of the water heater, the heat generated per unit time can be increased to make up for the heat loss due to the increase in thermal resistance, enabling the hot water to obtain more heat, thereby raising the temperature and improving the stability of waste heat recovery.

[0034] Furthermore, in the method of the present invention, by setting a preset first delay duration and a preset second delay duration, the heating time interval of the water heater is adjusted. Since minerals in the water 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 degree of scale formation by minerals in the water at high temperatures 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 deteriorating further. 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, in the method of the present invention, by setting a preset first fluctuation amplitude and a preset second fluctuation amplitude, the entrainment pressure difference of the steam ejector is adjusted. Due to the long-term use, the solder joints of the circuit board in the flow sensor become loose, resulting in signal transmission interruption, and some data cannot be accurately transmitted to the control unit, leading to inaccurate data. By increasing the entrainment pressure difference of the steam ejector, the steam ejector can draw cold water more powerfully, increasing the entrainment amount of cold water, so as to better mix with hot water and reduce the hot water temperature, further improving the stability of waste heat recovery.

[0036] Furthermore, in the method of the present invention, by setting a preset rising rate, the heating power of the water heater is adjusted. Since scale may form inside the waste heat recovery heat exchanger in the water heater, the thermal resistance increases, and the heat transfer efficiency decreases, resulting in insufficient temperature rise of the hot water before entering the entrainment mixing, and thus the temperature change is not obvious. By increasing the heating power of the water heater, the amount of heat generated per unit time can be increased to make up for the heat loss due to the increase in thermal resistance, enabling the hot water to obtain more heat, thereby raising the temperature and further improving the stability of waste heat recovery. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] Figure 2 is the 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 is the logical flowchart of the process of adjusting the heating time interval of the water heater in the waste heat recovery method based on steam injection according to an embodiment of the present invention;

[0040] Figure 4 is the logical flowchart of the process of adjusting the entrainment pressure difference of the steam ejector in the waste heat recovery method based on steam injection according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] In order to make the objectives and advantages of the present invention more clear and understandable, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and do not limit the protection scope of the present invention.

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

[0044] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0045] Please refer to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 shown, which are respectively the overall flowchart, the overall structure block diagram, the logic flowchart of the process of adjusting the heating time interval of the water heater, and the logic flowchart of the process of adjusting the entrainment pressure difference of the steam ejector of the method and device for waste heat recovery based on steam injection according to the embodiments of the present invention. A method for waste heat recovery based on steam injection according to the present invention includes:

[0046] Step S1, respectively using a flow sensor and a temperature sensor to monitor the cold water flow rate and water temperature in the water heater, using a heater to preliminarily heat the cold water, and using a waste heat recovery heat exchanger to raise the water temperature to the standard water temperature;

[0047] Step S2, introducing the hot water at the standard water temperature into the mixing chambers of a plurality of steam ejectors, sucking 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 ejector;

[0048] Step S3, obtaining the response delay duration of the regulation of the water heater within a plurality of regulation cycles;

[0049] Step S4, determine the stability of waste heat recovery based on the average delay duration of the hot water machine's regulation response;

[0050] Step S5, if the stability of the waste heat recovery does not meet the requirements, adjust the heating time interval of the hot water machine, or determine the regulation accuracy of the hot water machine's ejector temperature change based on the fluctuation range of the hot water machine's water output flow rate;

[0051] Step S6, if the regulation accuracy does not meet the requirements, adjust the ejector pressure difference of the steam ejector, or adjust the heating power of the hot water machine based on the water temperature rise rate in the hot water machine.

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

[0053] Specifically, the process of sucking cold water of different volumes into different mixing chambers to output hot water of different temperatures is as follows: First, introduce 85°C hot water into the three mixing chambers, and then suck cold water at a temperature of 10°C into the first mixing chamber until the temperature of the hot water in the mixing chamber reaches 60°C; suck cold water at a temperature of 10°C into the second mixing chamber until the temperature of the hot water in the mixing chamber reaches 45°C; suck cold water at a temperature of 10°C 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 after mixing in the above different mixing chambers can be set by itself according to the actual situation.

[0055] In implementation, the method of the present invention adjusts the heating time interval of the water heater according to the average delay duration of the regulation response of the water heater. Since minerals in the water form scale during the heating process and gradually deposit on the nozzle of the steam ejector, causing the steam ejector to become blocked, the regulation response time is prolonged. By increasing the heating time interval of the water heater, the speed and degree of scale formation by minerals in the water at high temperatures 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 deteriorating further, which helps to maintain the normal working state of the steam ejector and thus shorten the regulation response time. The ejector pressure difference of the steam ejector is adjusted according to the fluctuation range of the water outlet flow rate of the water heater. Due to the long-term use, the solder joints of the circuit board in the flow sensor become loose, resulting in signal transmission interruption, causing some data to be unable to be accurately transmitted to the control unit, leading to inaccurate data. By increasing the ejector pressure difference of the steam ejector, the steam ejector can extract cold water more powerfully, increase the injection amount of cold water, so as to better mix with hot water and reduce the hot water temperature. The heating power of the water heater is adjusted according to the rising rate of the water temperature in the water heater. Since scale may form inside the waste heat recovery heat exchanger in the water heater, the thermal resistance increases, and the heat transfer efficiency decreases, resulting in insufficient temperature rise of the hot water before entering the injection mixing, so that the temperature change is not obvious. By increasing the heating power of the water heater, the amount of heat generated per unit time can be increased to make up for the heat loss due to the increase in thermal resistance, enabling the hot water to obtain more heat and thus raising the temperature, improving the stability of waste heat recovery.

[0056] Specifically, before several steam ejectors operate, it also includes connecting several steam ejectors through a connecting valve.

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

[0058] Obtain the response delay durations of the water heater regulation within several regulation cycles, and calculate the average delay duration of the water heater regulation response;

[0059] Compare the average delay duration of the water heater regulation response with a preset first delay duration;

[0060] If the average delay duration of the water heater regulation response is greater than the preset first delay duration, it is determined that the stability of the waste heat recovery does not meet the requirements.

[0061] Specifically, determining the regulation accuracy of the water heater injection temperature change includes:

[0062] Compare the average delay duration of the water heater regulation response with the preset first delay duration and the preset second delay duration respectively;

[0063] If the average delay duration of the hot water machine's regulation response is greater than the preset first delay duration and less than or equal to the preset second delay duration, it is preliminarily determined that the regulation accuracy of the hot water machine's ejector temperature change does not meet the requirements, and it is determined whether the regulation accuracy of the hot water machine's ejector temperature change meets the requirements according to the fluctuation range of the hot water machine's water outlet flow rate.

[0064] It can be understood that the three intervals divided by the preset first delay duration and the preset second delay duration respectively correspond to three situations:

[0065] The first interval is that the average delay duration of the hot water machine's regulation response is less than or equal to the preset first delay duration, and the corresponding situation is: it is determined that the stability of waste heat recovery meets the requirements;

[0066] The second interval is that the average delay duration of the hot water machine's regulation response is greater than the preset first delay duration and less than or equal to the preset second delay duration, and 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, resulting in inaccurate transmission of some data to the control unit, resulting in inaccurate data;

[0067] The third interval is that the average delay duration of the hot water machine's regulation response is greater than the preset second delay duration, and the corresponding situation is: since minerals in the water will form scale during the heating process and gradually deposit on the nozzle of the steam ejector, resulting in blockage of the steam ejector, thus prolonging the regulation response time.

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

[0069] Preferably, the preferred embodiment of the preset first delay duration is 3s, and the preferred embodiment of the preset second delay duration is 6s.

[0070] Specifically, the average delay duration of the hot water machine's regulation response is the ratio of the total delay duration of the hot water machine's regulation response in several regulation cycles to the number of regulation cycles.

[0071] In implementation, the method of the present invention determines the stability of waste heat recovery by setting the preset first delay duration and the preset second delay duration, reduces the impact of inaccurate determination of the stability of waste heat recovery on the regulation accuracy of the hot water machine's ejector temperature change, and further improves the stability of waste heat recovery.

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

[0073] Comparing the average delay duration of the hot water machine's regulation response with the preset second delay duration;

[0074] If the average delay duration of the hot water machine control response is greater than the preset second delay duration, increase the heating time interval of the hot water machine.

[0075] Specifically, the increase amplitude of the heating time interval of the hot water machine is determined by the difference between the average delay duration of the hot water machine control response and the preset second delay duration.

[0076] Specifically, when the difference between the average delay duration of the hot water machine control response and the preset second delay duration is within 2 s, the heating time interval of the hot water machine is increased to 1.1 times the original; when the difference between the average delay duration of the hot water machine control response and the preset second delay duration exceeds 2 s, on the basis of increasing to 1.1 times the original, for every 1 s exceeded, the heating time interval of the hot water machine is increased by 0.5 min. For example, if the difference between the average delay duration of the hot water machine control response and the preset second delay duration is 4 s and the current heating time interval of the hot water machine is 10 min, the increased heating time interval of the hot water machine is 10×1.1 + 0.5×2 = 12 min.

[0077] In implementation, by setting the preset first delay duration and the preset second delay duration, the method of the present invention adjusts the heating time interval of the hot water machine. Since minerals in water will form scale during the heating process and gradually deposit on the nozzle of the steam ejector, resulting in the blockage of the steam ejector, thereby prolonging the control response time. By increasing the heating time interval of the hot water machine, the speed and degree of scale formation by minerals in water at high temperature can be reduced, thereby slowing down the deposition speed of scale at the nozzle of the steam ejector, preventing the further deterioration of the blockage situation of the steam ejector, helping 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 entrainment pressure difference of the steam ejector includes:

[0079] Obtain the water outlet flow rate of the hot water machine in a single cycle and calculate the fluctuation amplitude of the water outlet flow rate of the hot water machine;

[0080] Compare the fluctuation amplitude of the water outlet flow rate of the hot water machine with the preset first fluctuation amplitude and the preset second fluctuation amplitude respectively;

[0081] If the fluctuation amplitude of the water outlet flow rate of the hot water machine is greater than the preset first fluctuation amplitude, it is determined that the control accuracy of the entrainment temperature change of the hot water machine does not meet the requirements;

[0082] If the fluctuation amplitude of the water outlet flow rate of the hot water machine is greater than the preset first fluctuation amplitude and less than or equal to the preset second fluctuation amplitude, increase the entrainment pressure difference of the steam ejector;

[0083] If the fluctuation range of the hot water output flow rate of the hot water machine is greater than a preset second fluctuation range, it is preliminarily determined that the sensitivity of the temperature regulation of the hot water machine does not meet the requirements, and it is determined whether the sensitivity of the temperature regulation of the hot water machine meets the requirements according to the water temperature rising rate in the hot water machine.

[0084] It can be understood that the three intervals divided by the preset first fluctuation range and the preset second fluctuation range respectively correspond to three situations:

[0085] The first interval is that the fluctuation range of the hot water output flow rate of the hot water machine is less than or equal to the preset first fluctuation range, and the corresponding situation is: it is determined that the regulation accuracy of the ejector variable temperature of the hot water machine meets the requirements;

[0086] The second interval is that the fluctuation range of the hot water output flow rate of the hot water machine is greater than the preset first fluctuation range and less than or equal to the preset second fluctuation range, and 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, resulting in inaccurate transmission of some data to the control unit, resulting in inaccurate data;

[0087] The third interval is that the fluctuation range of the hot water output flow rate of the hot water machine is greater than the preset second fluctuation range, and the corresponding situation is: due to possible scaling inside the waste heat recovery heat exchanger in the hot water machine, the thermal resistance increases, the heat transfer efficiency decreases, resulting in insufficient temperature rise of the hot water before entering the ejector mixing, so that the temperature change is not obvious.

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

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

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

[0091] In implementation, the method of the present invention determines the regulation accuracy of the ejector variable temperature of the hot water machine by setting the preset first fluctuation range and the preset second fluctuation range, reduces the influence of the decline in the stability of waste heat recovery caused by inaccurate determination of the regulation accuracy of the ejector variable temperature of the hot water machine, and further improves the stability of waste heat recovery.

[0092] Specifically, the increase amplitude of the ejector pressure difference of the steam ejector is determined by the difference between the fluctuation range of the hot water output flow rate of the hot water machine and the preset first fluctuation range.

[0093] Specifically, when the difference between the fluctuation range of the hot water output flow of the hot water machine and the preset first fluctuation range is within 1.5 L / min, the entrainment pressure difference of the steam ejector increases to 1.2 times the original value; when the difference between the fluctuation range of the hot water output flow of the hot water machine and the preset first fluctuation range exceeds 1.5 L / min, on the basis of increasing to 1.2 times the original value, for every 0.5 L / min exceeded, the entrainment pressure difference of the steam ejector increases by 1 kPa. For example, when the difference between the fluctuation range of the hot water output flow of the hot water machine and the preset first fluctuation range is 2.5 L / min and the current entrainment pressure difference of the steam ejector is 20 kPa, the increased entrainment pressure difference of the steam ejector is 20×1.2 + 1×2 = 26 kPa.

[0094] In implementation, by setting the preset first fluctuation range and the preset second fluctuation range, the method of the present invention adjusts the entrainment pressure difference of the steam ejector. Due to the loosening of the solder joints of the circuit board in the flow sensor caused by long-term use, the signal transmission is interrupted, resulting in some data being unable to be accurately transmitted to the control unit, leading to inaccurate data. By increasing the entrainment pressure difference of the steam ejector, the steam ejector can extract cold water more powerfully, increase the entrainment amount of cold water, so as to better mix with hot water, reduce the hot water temperature, and further improve the stability of waste heat recovery.

[0095] Specifically, the adjustment of the heating power in the hot water machine includes:

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

[0097] Compare the rate of increase in the water temperature in the hot water machine with the preset rate of increase;

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

[0099] It can be understood that the two intervals divided by the preset rate of increase respectively correspond to two situations:

[0100] The first interval is that the rate of increase in the water temperature in the hot water machine is less than the preset rate of increase, and the corresponding situation is: due to possible scaling inside the waste heat recovery heat exchanger in the hot water machine, the thermal resistance increases, and the heat transfer efficiency decreases, resulting in insufficient temperature rise of the hot water before entering the entrainment mixing, so that the temperature change is not obvious;

[0101] The second interval is that the rate of increase in the water temperature in the hot water machine is greater than or equal to the preset rate of increase, and the corresponding situation is: it is determined that the sensitivity of the hot water machine temperature adjustment meets the requirements.

[0102] In practice, the generally selected range of the preset heating rate is [2 °C / min, 4 °C / min].

[0103] Preferably, a preferred embodiment of the preset heating rate is 3 °C / min.

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

[0105] In implementation, the method of the present invention determines the sensitivity of the water heater temperature adjustment by setting a preset heating rate, reducing the impact of the decrease in the stability of waste heat recovery caused by inaccurate determination of the sensitivity of the water heater temperature adjustment, and further improving the stability of waste heat recovery.

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

[0107] Specifically, when the difference between the preset heating rate and the heating rate of the water temperature in the water heater is within 2 °C / min, the heating power of the water heater increases to 1.2 times the original; when the difference between the preset heating rate and the heating rate of the water temperature in the water heater exceeds 2 °C / min, on the basis of increasing to 1.1 times the original, for every 1 °C / min exceeded, the heating power of the water heater increases by 0.5 kW. For example, when the difference between the preset heating rate and the heating rate of the water temperature in the water heater is 4 °C / min and the current heating power of the water heater is 5 kW, the increased heating power of the water heater is 5×1.2 + 0.5×2 = 7 kW.

[0108] In implementation, the method of the present invention adjusts the heating power of the water heater by setting a preset heating rate. Since scale may form inside the waste heat recovery heat exchanger in the water heater, the thermal resistance increases, and the heat transfer efficiency decreases, resulting in insufficient temperature rise of the hot water before entering the ejector mixing, so that the temperature change is not obvious. By increasing the heating power of the water heater, the heat generated per unit time can be increased to make up for the heat loss due to the increase in thermal resistance, enabling the hot water to obtain more heat, thereby increasing the temperature and further improving the stability of waste heat recovery.

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

[0110] A water heater housing;

[0111] A heating module, which is arranged inside the housing of the water heater and is used to heat cold water, 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 ejecting module, which is used to discharge the hot water after further heating as hot water at different temperatures by means of a plurality of steam ejectors, includes a plurality of mixing chambers for mixing the cold water and the hot water to output hot water at different temperatures and a plurality of nozzles connected to the mixing chambers for discharging the hot water at different temperatures;

[0113] A 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 water flow rate;

[0114] A display module, which is connected to the housing of the water heater and is used to display the water temperature information.

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

[0116] So far, the technical solution of the present invention has been described in combination with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle 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 protection scope of the present invention.

Claims

1. A waste heat recovery method based on steam injection, characterized in that: include: A flow sensor and a temperature sensor are used to monitor the cold water flow and water temperature in the water heater respectively, a heater is used to preliminarily heat the cold water, and a waste heat recovery heat exchanger is used to raise the water temperature to the standard water temperature; The hot water of the standard water temperature is introduced into the mixing chambers of a plurality of steam ejectors, and different volumes of cold water are sucked into different mixing chambers to output hot water of different temperatures, and the hot water of different temperatures is discharged from the nozzles of each steam ejector; Obtaining the response delay duration of the water heater control within several control cycles; Determine the stability of waste heat recovery based on the average delay time of the water heater control response; 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 induced temperature change is determined based on the fluctuation amplitude of the water outlet flow of the water heater; If the control accuracy does not meet the requirement, the injection 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.

2. The waste heat recovery method based on steam injection according to claim 1, characterized in that: Before the plurality of steam ejectors are operated, the method further comprises connecting the plurality of steam ejectors through a connecting valve.

3. The waste heat recovery method based on steam injection according to claim 2, characterized in that: Determining the stability of the waste heat recovery includes: Comparing the average delay time of the water heater control response 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, it is determined that the stability of waste heat recovery does not meet the requirements.

4. The waste heat recovery method based on steam injection according to claim 3 is characterized in that: Determining the control accuracy of the water heater injection temperature change includes: Comparing the average delay time of the water heater control response with the preset first delay time and the preset second delay time respectively; If the average delay duration of the water heater control response is greater than the preset first delay duration and less than or equal to the preset second delay duration, it is preliminarily determined that the control accuracy of the water heater induced temperature change does not meet the requirements, and whether the control accuracy of the water heater induced temperature change meets the requirements is determined based on the fluctuation amplitude of the water outlet flow of the water heater.

5. The waste heat recovery method based on steam injection according to claim 4, characterized in that: The heating time interval of the water heater is adjusted, comprising: Comparing the average delay time of the water heater control response with the preset second delay time; If the average delay time of the water heater control response is greater than the preset second delay time, increasing the heating time interval of the water heater; The increase range of the heating time interval of the water heater is determined by the difference between the average delay time of the water heater control response and the preset second delay time.

6. The waste heat recovery method based on steam injection according to claim 5, characterized in that: The injection pressure difference of the steam ejector is adjusted, including: Comparing the fluctuation amplitude of the water outlet flow of the water heater with the preset first fluctuation amplitude and the preset second fluctuation amplitude respectively; If the fluctuation amplitude of the water flow rate of the water heater is greater than the preset first fluctuation amplitude, it is determined that the control accuracy of the water heater induced temperature change does not meet the requirements; If the fluctuation amplitude of the water flow rate of the water heater is greater than the preset first fluctuation amplitude and less than or equal to the preset second fluctuation amplitude, increasing the injection pressure difference of the steam ejector; If the fluctuation amplitude of the water outlet flow of the water heater is greater than the preset second fluctuation amplitude, it is preliminarily determined that the sensitivity of the temperature regulation of the water heater does not meet the requirements, and whether the sensitivity of the temperature regulation of the water heater meets the requirements is determined based on the rate of increase of the water temperature in the water heater.

7. The waste heat recovery method based on steam injection according to claim 6, characterized in that: The increase range of the injection pressure difference of the steam ejector is determined by the difference between the fluctuation range of the water outlet flow rate of the water heater and the preset first fluctuation range.

8. The waste heat recovery method based on steam injection according to claim 7, characterized in that: The heating power in the water heater is adjusted, comprising: Comparing the rate of increase of the water temperature in the water heater with a preset rate of increase; If the rate of increase of the water temperature in the water heater is less than the preset rate of increase, it is determined that the sensitivity of the temperature adjustment of the water heater does not meet the requirement, and the heating power of the water heater is increased.

9. The waste heat recovery method based on steam injection according to claim 8, characterized in that: The increase range of the heating power of the water heater is determined by the difference between a preset increase rate and a rate of increase of the water temperature in the water heater.

10. A waste heat recovery device using the waste heat recovery method based on steam injection according to any one of claims 1 to 9, characterized in that: include: Water heater housing; A heating module, which is arranged inside the water heater housing and is used to heat cold water, including 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; An ejection module, which is connected to the heating module and is used to mix the further heated hot water into hot water of different temperatures through a plurality of steam ejectors and then discharge the hot water, comprising a plurality of mixing chambers for mixing the cold water and the hot water to output hot water of different temperatures and a plurality of nozzles connected to the mixing chambers for discharging the hot water of different temperatures; A detection module connected to the heating module, comprising 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 water flow rate; A display module is connected to the water heater housing and is used to display water temperature information.

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