Constant temperature control method for water heater and water heater

Abstract

The present invention relates to a constant temperature control method for a water heater, the water heater comprising a water inlet pipe, a heat exchanger, a burner, and a water outlet pipe, the water inlet pipe being connected to the water inlet of the heat exchanger, the water outlet pipe being connected to the water outlet of the heat exchanger, the burner being arranged corresponding to the heat exchanger and being used to heat water flowing through the heat exchanger, and the method being characterized in that after the water in the water heater is turned off, the heating load of the burner is controlled to be increased to continue heating, so that the water temperature in the water outlet pipe and the heat exchanger is higher than the set water outlet temperature T0. The constant temperature control method has low energy consumption and can improve the temperature stability of the outlet water temperature. The present invention also relates to a water heater using the constant temperature control method, which does not require an additional heating device, thus reducing costs and avoiding excessive energy waste. The outlet water temperature is stable when the water is turned off and then on again.

Description

Technical Field

[0001] The present invention relates to a constant temperature control method for a water heater and also relates to a water heater applying the constant temperature control method. Background Art

[0002] When the water heater is turned off and then on again, the heating energy cannot be instantly increased from the ignition energy to the target load due to the instantaneous re-ignition of the water heater. Furthermore, there is a fan cleaning process before ignition, during which the fan rotates to discharge exhaust gas. During this process, the water in the pipe is flowing but has not yet been ignited. These two factors cause the water temperature to drop sharply, ultimately causing users to experience fluctuating water temperatures at the water end, which is a very poor user experience, especially in winter. Based on this, the existing technology mainly uses the following two technical means to solve this problem.

[0003] The first method is to set up a circulation pipeline and start the water circulation after the water heater is turned off, so that the water heater is in a continuous working state, thereby ensuring that the water temperature is maintained at a constant temperature. For example, in the Chinese invention patent application "Control Method and Water Heater System" with publication number CN113124571A (application number 201911426187.0), the water heater system disclosed therein controls the water preheated by the gas water heater to circulate in the preheating circulation loop composed of the hot water pipe, return water device, tap water pipe and water heater for circulation preheating when the preheating function of the gas water heater is turned on, obtains a water outlet signal again, controls the water heater system to start the preheating function before the electric control valve is closed, obtains a signal for the gas water heater to start the preheating function for the first time, detects the return water temperature at the water inlet end of the water inlet pipe of the gas water heater; confirms that the return water temperature at the water inlet end reaches a first preset temperature, controls the gas water heater to stop preheating, and obtains the first preheating time of the gas water heater; confirms the circulation preheating time of the water heater according to the first preheating time; obtains a signal for the gas water heater to start the preheating function again, and controls the water heater to perform circulation preheating according to the circulation preheating time of the gas water heater. This type of water heater cannot completely solve the problem of constant water temperature, and also has problems of high energy consumption and slow initial heating.

[0004] The second way to solve this problem is to set up an additional heating device. For example, the Chinese invention patent "Water heater and its water outlet control system, water supply system" with authorization announcement number CN112443984B (application number 202011348327.X) discloses a water heater that is additionally provided with a thermal pool for storing water, and a heating module is provided in the thermal pool. The heating module is used to heat the water in the thermal pool to a set temperature range. After the water is turned off and then turned on again, a small section of cold water output by the water heater is neutralized by mixing to ensure the constant temperature of the output water. The Chinese invention patent application "Control method of gas water heater and gas water heater" with application publication number CN113154689A (application number 202110443048.X) discloses a water heater that is provided with an additional electric heating module. When the water heater is turned off and then turned on for water use, auxiliary heating is performed by the electric heating module, thereby reducing the temperature fluctuation range. A water heater with this structure has high structural cost, high energy consumption, and slow initial heating. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a constant temperature control method for a water heater with low cost and capable of ensuring a constant output temperature when the water is turned off and then on, in view of the above-mentioned prior art.

[0006] The second technical problem to be solved by the present invention is to provide a water heater that can output water at a constant temperature when the water is turned off and then on again, in response to the above-mentioned prior art.

[0007] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a constant temperature control method for a water heater, the water heater includes a water inlet pipe, a heat exchanger, a burner and a water outlet pipe, the water inlet pipe is connected to the water inlet of the heat exchanger, the water outlet pipe is connected to the water outlet of the heat exchanger, and the burner is set corresponding to the heat exchanger and is used to heat the water flowing through the heat exchanger. It is characterized in that: after the water of the water heater is turned off, the heating load of the burner is controlled to increase to continue heating, so that the water temperature in the water outlet pipe and the heat exchanger is higher than the set water outlet temperature T0.

[0008] In order to avoid the outlet water temperature being too high when the water is turned on when the ambient temperature is high, the water inlet temperature Tj at the water inlet end of the water inlet pipe is detected when the water heater is working; if Tj ≥ Ts, where Ts is the set temperature threshold, there is no need to control the burner to continue heating after the water supply of the water heater is stopped; if Tj < Ts, when the water supply of the water heater is turned off, the heating load of the burner is controlled to increase and continue heating.

[0009] Preferably, the heating load condition for the burner to continue heating after the water is turned off is: the water temperature in the water outlet pipe and the heat exchanger is maintained above T0+Tx within a first set time t1, where Tx is a positive number.

[0010] Preferably, different heating loads of the burner after water is turned off corresponding to different water inlet temperatures are initialized;

[0011] When the water heater is working, the water inlet temperature Tj at the water inlet end of the water inlet pipe is detected, and the heating load Q of the burner after the water supply of the water heater is cut off is determined according to the water inlet temperature Tj. When the water supply of the water heater is turned off, the burner is controlled to work according to the heating load Q for the second set time t0, t0<t1.

[0012] Preferably, 2 minutes ≤ t1 ≤ 4 minutes.

[0013] The technical solution adopted by the present invention to solve the above-mentioned second technical problem is: a water heater, including a water inlet pipe, a heat exchanger, a burner and a water outlet pipe, the water inlet pipe is connected to the water inlet of the heat exchanger, the water outlet pipe is connected to the water outlet of the heat exchanger, the burner is arranged corresponding to the heat exchanger and is used to heat the water flowing through the heat exchanger, the water heater also includes a memory and a processor, and is characterized in that: the memory also stores a program for implementing the constant temperature control method as mentioned above, and the processor can call and execute the program in the memory.

[0014] In order to achieve further water mixing in the early stage of re-boiling water so that the temperature of the output water is closer to the set water outlet temperature, a water tank is further provided on the water outlet pipe.

[0015] Compared with the prior art, the advantages of the present invention are as follows: the constant temperature control method of the water heater of the present invention increases the heating load of the burner after the water is turned off, so that the water temperature in the water outlet pipe and heat exchanger is higher than the set water outlet temperature T0. In this way, even if the water temperature drops in the water outlet pipe and heat exchanger when the water is turned on again in a short period of time, it can be maintained within the allowable fluctuation range of the set water outlet temperature. At the same time, the heat of the water in the water outlet pipe and heat exchanger can also raise the temperature of the pipe wall, so that the low-temperature water output in the early stage of the water turning on again can absorb the heat from the water outlet pipe and heat exchanger to increase the temperature, thereby maintaining the outlet water temperature within the allowable fluctuation range of the set water outlet temperature, thus ensuring the constant temperature of the water outlet temperature when the water is turned off and then turned on again.

[0016] The water heater using this method does not need to set up an additional heating device, which reduces costs and does not waste excessive energy. The water outlet temperature is stable when the water is turned off and then on again. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the water heater in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0019] Example 1

[0020] like Figure 1As shown, the water heater in this embodiment includes a water inlet pipe 1, a heat exchanger 2, a burner 3, and a water outlet pipe 4. The water inlet pipe 1 is connected to the water inlet of the heat exchanger 2, and the water outlet pipe 4 is connected to the water outlet of the heat exchanger 2. The burner 3 in this embodiment is a gas burner 3. Depending on the specific type of water heater, the burner 3 can also be other types of heating equipment or other fuel burners 3. The burner 3 is arranged corresponding to the heat exchanger 2 and is used to heat the water flowing through the heat exchanger 2. During operation, water is supplied to the water in the water inlet pipe 1. When the water in the water inlet pipe 1 flows through the heat exchanger 2, the burner 3 heats the water in the heat exchanger 2.

[0021] The water heater further includes a memory and a processor, wherein the memory further stores a program for implementing the following constant temperature control method, and the processor can retrieve and execute the program in the memory. The water heater operates using the following constant temperature control method.

[0022] When using a water heater, it's common to shut off the water and then turn it back on again shortly afterward. This can occur, for example, when washing dishes or bathing. The time between shutting off and turning it back on typically takes less than three minutes. When the water heater is turned off and then turned back on, the heating energy cannot instantly increase from the ignition energy to the target load because the water heater re-ignites the instant the water turns on. Furthermore, there's a fan cleaning process before ignition, during which the fan rotates to expel exhaust gases. During this process, the water in the pipes is flowing but not yet ignited. These two factors cause the water temperature to drop sharply. Based on this situation, the constant temperature control method for the water heater in this embodiment is as follows: after the water heater is shut off, the heating load of the burner 3 is increased to continue heating, so that the water temperature in the water outlet pipe 4 and heat exchanger 2 is higher than the set outlet water temperature T0. This way, even if the water in the water outlet pipe 4 and heat exchanger 2 cools down, it can still be maintained within the allowable fluctuation range of the set outlet water temperature. The human body is generally insensitive to temperature changes within a range of 3°C. Therefore, 3°C can be used as the allowable fluctuation range of the outlet water temperature, that is, the outlet water temperature can be maintained within a range of ±3°C of the set outlet water temperature, achieving constant outlet water temperature control. When the water is turned back on within a short period of time, based on the temperature increase of the water in the outlet pipe 4 and heat exchanger 2 after the water was previously shut off, the water in the outlet pipe 4 and heat exchanger 2 can still be maintained above the set outlet water temperature when the water is turned back on. In this way, the outlet water temperature of the water heater will not drop sharply in the early stage of turning the water back on, ensuring the constant outlet water temperature. In addition, while the temperature of the water in the outlet pipe 4 and heat exchanger 2 is increased based on the temperature increase of the water in the outlet pipe 4 and heat exchanger 2 after the water was previously shut off, the heat from the water in the outlet pipe 4 and heat exchanger 2 can also heat the pipe walls, allowing the low-temperature water output in the early stage of turning the water back on to absorb the heat from the outlet pipe 4 and heat exchanger 2 to increase its temperature, thereby maintaining the outlet water temperature within the allowable fluctuation range of the set outlet water temperature, ensuring the constant outlet water temperature in the case of turning the water back on.

[0023] The heating load condition for burner 3 to continue heating after the water is turned off is that the water temperature in the water outlet pipe 4 and heat exchanger 2 is maintained above T0 + Tx for a first set time duration t1, where Tx is a positive number. This first set time duration t1 is typically based on the empirically determined time interval from water shutoff to water re-opening, with a range of 2 minutes ≤ t1 ≤ 4 minutes. In this embodiment, t1 = 3 minutes. Tx is determined based on previous experimental testing. Based on this value, it is ensured that during the initial water-on period, the outlet temperature of new water entering the water inlet pipe 1, after passing through the heat exchanger 2 and the water outlet pipe 4, reaches a minimum of T0 - 3°C.

[0024] Based on the test in the product development stage, different heating loads of the burner 3 after the water supply is turned off corresponding to different water inlet temperatures can be initialized to achieve the aforementioned heating load condition that the burner 3 continues to heat after the water supply is turned off.

[0025] Based on this, when the water heater is working, the water inlet temperature Tj at the water inlet end of the water inlet pipe 1 is detected, and the heating load Q of the burner 3 after the water of the water heater is cut off is determined according to the water inlet temperature Tj. When the water of the water heater is turned off, the burner 3 is controlled to work according to the second set time t0 according to the heating load Q, t0<t1.

[0026] The outlet water temperature when the water heater is turned off and then turned back on often occurs when the ambient temperature is low, that is, when the inlet water temperature is low, resulting in large temperature fluctuations. When the inlet water temperature is high, if the water in the outlet pipe 4 and heat exchanger 2 is heated to a temperature higher than the set outlet water temperature after the water heater is turned off, the outlet water temperature may be too high when the water is turned back on, which also wastes heating energy. Therefore, to avoid excessively high outlet water temperatures when the water is turned back on when the ambient temperature is high, the water heater detects the inlet water temperature Tj at the inlet end of the inlet pipe 1 during operation. If Tj ≥ Ts, where Ts is the set temperature threshold, there is no need to control the burner 3 to continue heating after the water heater is turned off. If Tj < Ts, after the water heater is turned off, the heating load of the burner 3 is increased to continue heating. Tj is determined based on specific testing. For example, if Tj is set to 20°C, the ambient temperature is often high in the summer. At this time, when the water heater is turned off and then on again, even if the water in the outlet pipe 4 and heat exchanger 2 is not heated after the water is turned off, the outlet water temperature drop is minimal. Furthermore, given the high ambient temperature, the human body is less sensitive to changes in water temperature. Even if a temperature drop occurs, the user will not experience noticeable discomfort. Therefore, to save energy, the inlet water temperature Tj is used to determine whether burner 3 should continue heating after the water is turned off.

[0027] The constant temperature control method for a water heater according to the present invention increases the heating load of the burner 3 after the water is turned off, thereby raising the water temperature in the water outlet pipe 4 and the heat exchanger 2 above the set water outlet temperature T0. Thus, even if the water temperature drops within the water outlet pipe 4 and the heat exchanger 2 when the water is turned back on within a short period of time, the water can be maintained within the permissible fluctuation range of the set water outlet temperature. Simultaneously, the heat generated by the water in the water outlet pipe 4 and the heat exchanger 2 can also raise the temperature of the pipe walls, allowing the low-temperature water output before the water is turned back on to absorb the heat from the water outlet pipe 4 and the heat exchanger 2 to raise its temperature. This in turn maintains the water outlet temperature within the permissible fluctuation range of the set water outlet temperature, thus ensuring the constant temperature of the water outlet temperature when the water is turned off and then turned back on.

[0028] The water heater using this method does not need to set up an additional heating device, which reduces costs and does not waste excessive energy. The water outlet temperature is stable when the water is turned off and then on again.

[0029] Example 2

[0030] The only difference between this embodiment and the first embodiment is that a water tank 5 is further provided on the water outlet pipe 4. After the water heater is turned off, the heat output by the burner 3 can raise the temperature of the water in the heat exchanger 2, the water outlet pipe 4, and the water tank 5. Therefore, when the water heater is turned off and then turned on again, the water in the water tank 5 flows out slowly. In the early stage of the water heater being turned on again, the water newly entering the water inlet pipe 1 is heated by the heat exchanger 2 and flows into the water tank 5. This cooler water mixes with the warmer water in the water tank 5, reducing fluctuations in the output water temperature, making the output water temperature closer to the set output water temperature, and improving the constant temperature performance of the water heater.

Claims

1. A constant temperature control method for a water heater, the water heater comprising a water inlet pipe (1), a heat exchanger (2), a burner (3) and a water outlet pipe (4), the water inlet pipe (1) being connected to the water inlet of the heat exchanger (2), the water outlet pipe (4) being connected to the water outlet of the heat exchanger (2), the burner (3) being arranged corresponding to the heat exchanger (2) and used for heating water flowing through the heat exchanger (2), characterized in that: After the water heater is turned off, the heating load of the burner (3) is controlled to increase and continue heating, so that the water temperature in the water outlet pipe (4) and the heat exchanger (2) is higher than the set water outlet temperature T0; The heating load condition for the burner (3) to continue heating after the water is turned off is: the water temperature in the water outlet pipe (4) and the heat exchanger (2) is maintained above T0+Tx within a first set time length t1, Tx is a positive number; 2 minutes ≤ t1 ≤ 4 minutes.

2. The constant temperature control method for a water heater according to claim 1, characterized in that: When the water heater is working, the water inlet temperature Tj at the water inlet end of the water inlet pipe (1) is detected; if Tj≥Ts, where Ts is a set temperature threshold, after the water supply of the water heater is stopped, there is no need to control the burner (3) to continue heating; if Tj<Ts, when the water supply of the water heater is turned off, the heating load of the burner (3) is controlled to increase to continue heating.

3. The constant temperature control method for a water heater according to claim 1 or 2, characterized in that: Initialize different heating loads of the burner (3) after the water heater is shut off corresponding to different water inlet temperatures; When the water heater is operating, the water inlet temperature Tj at the water inlet end of the water inlet pipe (1) is detected, and the heating load Q of the burner (3) after the water supply of the water heater is turned off is determined according to the water inlet temperature Tj. When the water supply of the water heater is turned off, the burner (3) is controlled to operate for a second set time duration t0 according to the heating load Q, t0 < t1.

4. A water heater comprising a water inlet pipe (1), a heat exchanger (2), a burner (3) and a water outlet pipe (4), wherein the water inlet pipe (1) is connected to the water inlet of the heat exchanger (2), the water outlet pipe (4) is connected to the water outlet of the heat exchanger (2), the burner (3) is arranged corresponding to the heat exchanger (2) and is used to heat water flowing through the heat exchanger (2), and the water heater further comprises a memory and a processor, characterized in that: The memory also stores a program for implementing the constant temperature control method according to any one of claims 1 to 3, and the processor can call and execute the program in the memory.

5. The water heater according to claim 4, characterized in that: A water tank (5) is also provided on the water outlet pipe (4).

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