JP2007078231A - Water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water heater capable of preventing overshoot of hot water supply temperature to a target hot water supply temperature when in-coming water quantity is reduced. <P>SOLUTION: The water heater is equipped with a bypass ratio control means 32 which estimates waste heat quantity in a heat exchanger 4 on the basis of the difference between the first heating quantity and the second heating quantity, and controls a bypass ratio as a ratio of a flow rate of the water circulating in a bypass pipe 5 to a flow rate of the water circulating in the heat exchanger 4 by a bypass proportional valve 13 of a bypass ratio control means 32 to cancel the rise of hot water supply temperature of the heat exchanger 4 by the waste heat quantity when a flow rate detected by a flow rate sensor 12 is reduced during the execution of hot water supply operation, and heating quantity of a gas burner 20 is controlled to be reduced from a first heating quantity to a second heating quantity by a hot water supply control means 31. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hot water supply apparatus that mixes hot water discharged from a heat exchanger with water supplied from a bypass pipe that bypasses the heat exchanger, and supplies hot water at a desired temperature, particularly when the amount of incoming water is reduced. It relates to suppression of fluctuations in hot water supply temperature.

  Conventionally, as shown in FIG. 4, in order to prevent low-temperature corrosion of the heat exchanger 102, a bypass pipe 103 that bypasses the heat exchanger 102 is provided so as to keep the tapping temperature of the heat exchanger 102 high. A hot water supply apparatus is known (see, for example, Patent Document 1).

  In such a hot water supply apparatus, the controller 108 detects the temperature of the water supplied from the water supply pipe 100 detected by the incoming water temperature sensor 104, the amount of incoming water from the water supply pipe 100 detected by the flow sensor 107, and a predetermined target hot water supply. Based on the temperature, the target combustion amount of the burner 111 necessary for supplying hot water at the target hot water supply temperature from the hot water supply pipe 101 is determined. Then, the controller 108 controls the combustion amount of the burner 111 to the target combustion amount and executes the “hot water supply operation”. Moreover, the controller 108 controls the opening degree of the bypass proportional valve 106 so that the hot water temperature of the heat exchanger 102 becomes equal to or higher than the lower limit temperature for preventing low temperature corrosion.

  Here, when the currant 110 is operated during execution of the “hot water supply operation” and the amount of water entering from the water supply pipe 100 decreases, the controller 108 changes the target combustion amount of the burner 111 accordingly and the combustion of the burner 111 is performed. Reduce the amount. However, even if the combustion amount of the burner 111 is reduced in this way, the heating amount in the heat exchanger 102 is not immediately reduced due to the residual heat due to the heat capacity of the heat exchanger 102.

For this reason, there is a disadvantage that a so-called overshoot occurs in which the temperature of the hot water in the heat exchanger 102 rises rapidly and the temperature of the hot water supplied from the hot water supply pipe 101 to the currant 110 becomes higher than the target hot water temperature.
Japanese Patent Laid-Open No. 6-288637

  An object of the present invention is to provide a hot water supply apparatus that eliminates the above inconvenience and suppresses the occurrence of overshooting of the hot water supply temperature with respect to the target hot water supply temperature when the amount of incoming water decreases.

  The present invention has been made to achieve the above object, and is connected to a water supply pipe and a hot water supply pipe, heats the water supplied from the water supply pipe, and discharges the hot water to the hot water supply pipe, Heating means for heating the heat exchanger, a bypass pipe that bypasses the heat exchanger and connects the water supply pipe and the hot water supply pipe, and the bypass pipe that circulates with respect to the flow rate of water flowing through the heat exchanger Bypass ratio changing means for changing a bypass ratio that is a ratio of water flow rate, incoming water temperature detecting means for detecting the temperature of water supplied from the water supply pipe to the heat exchanger, and from the water supply pipe to the heat exchanger And the flow rate detection means for detecting the total flow rate of the water supplied to the bypass pipe, and the temperature of hot water supplied to the downstream side of the location where the hot water pipe is connected to the bypass pipe are set to a predetermined target hot water temperature. The detected temperature of the incoming water temperature detecting means and the previous temperature Based on the detected flow rate of the flow rate detecting unit, an improvement of the water heater with a hot water supply control means for executing the hot water supply operation for controlling the heating amount of said heating means.

  During the hot water supply operation, the detected flow rate of the flow rate detecting means decreases, and the hot water supply control means controls the heating amount of the heating means to be reduced from the first heating amount to the second heating amount. When it is made, the amount of remaining heat in the heat exchanger is estimated according to the difference between the first amount of heating and the second amount of heating, and the rise in the tapping temperature of the heat exchanger due to the amount of remaining heat is calculated. A hot water supply apparatus comprising a bypass ratio control means for controlling the bypass ratio via the bypass ratio changing means so as to cancel.

  In the present invention, the amount of water entering the water supply pipe decreases during execution of the hot water supply operation, and the heating amount of the heating means is changed from the first heating amount to the second heating amount by the hot water supply control means. When the decrease control is performed, due to the heat capacity of the heat exchanger, the amount of heating in the heat exchanger becomes the second heating amount superimposed with the remaining heat due to the first heating amount. . Therefore, heating of water in the heat exchanger becomes excessive due to the residual heat.

  Therefore, the bypass ratio control means estimates the amount of remaining heat in the heat exchanger according to the difference between the first heating amount and the second heating amount, and increases the tapping temperature of the heat exchanger due to the remaining heat amount. By controlling the bypass ratio by the bypass ratio changing means so as to cancel out the minute, the temperature of the hot water supplied from the hot water supply pipe is maintained in the vicinity of the target hot water temperature, and an overshoot with respect to the target hot water temperature is prevented. It is possible to suppress the occurrence.

  Further, the bypass ratio control means, from the time when the detected flow rate of the flow rate detecting means decreases, until all the hot water located in the heat exchanger at that time is discharged from the heat exchanger, The bypass ratio is controlled via the bypass ratio changing means so as to cancel out the rise in the hot water temperature of the heat exchanger due to the residual heat amount.

  According to the present invention, when the detected flow rate of the flow rate detecting means decreases, the hot water existing in the heat exchanger is heated by the residual heat due to the first heating amount, and the heat exchanger It is made out of hot water. Therefore, from the time when the detected flow rate of the flow rate detecting means decreases until the hot water located in the heat exchanger at that time is completely discharged from the heat exchanger, the heat exchange by the residual heat amount is performed. By controlling the bypass ratio by the bypass ratio control means so as to cancel out the rise in the hot water temperature of the boiler, overshooting of the hot water supply temperature due to residual heat can be more reliably suppressed.

  Further, the bypass ratio control means, via the bypass ratio change means, in such a range that the bypass ratio is equal to or less than a predetermined upper limit so as to cancel the rise in the hot water temperature of the heat exchanger due to the remaining heat amount. And controlling the bypass ratio.

  According to the present invention, the flow rate of water flowing through the heat exchanger is extremely reduced by setting the bypass ratio too large, and boiling can be prevented from occurring in the heat exchanger. It is possible to prevent the heat exchanger from deteriorating due to boiling.

  Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a hot water supply apparatus of the present invention, FIG. 2 is a flowchart of hot water supply operation, and FIG.

  Referring to FIG. 1, a hot water supply apparatus 1 according to the present embodiment includes a heat exchanger 4 connected to a water supply pipe 2 and a hot water supply pipe 3, and bypasses the heat exchanger 4 to provide a water supply pipe 2 and a hot water supply pipe 3. Downstream side of the connection between the bypass pipe 5 that communicates, the incoming water temperature sensor 10 that detects the temperature of the water supplied to the water supply pipe 2 (corresponding to the incoming water temperature detection means of the present invention), and the bypass pipe 5 of the hot water supply pipe 3 A hot water supply temperature sensor 11 for detecting the temperature of hot water supplied to the water supply, a flow rate sensor 12 for detecting the flow rate of water supplied to the water supply pipe 2 (corresponding to the flow rate detection means of the present invention), and the heat exchanger 4 are circulated. A bypass proportional valve 13 (corresponding to the bypass ratio changing means of the present invention) for changing the ratio of the flow rate of water and the flow rate of water flowing through the bypass pipe 5, the gas burner 20 for heating the heat exchanger 4, and the gas burner 20 Gas proportional valve 21 for adjusting the supply amount of fuel gas, gas Gas source valve 22 for switching supply / cutoff of fuel gas to burner 20, ignition electrode 23 for igniting gas burner 20, combustion fan 24 for adjusting the supply amount of combustion air to gas burner 20, and hot water supply device 1 as a whole A controller 30 for controlling a typical operation and a remote controller 40 for setting a target hot water supply temperature and the like are provided.

  The controller 30 receives a temperature detection signal of the incoming water temperature sensor 10, a temperature detection signal of the hot water supply temperature sensor 11, and a flow rate detection signal of the flow rate sensor 12. Further, the operations of the bypass proportional valve 13, the gas proportional valve 21, the gas main valve 22, the ignition electrode 23, and the combustion fan 24 are controlled by a control signal output from the controller 30. The remote controller 40 is communicably connected to the controller 30, and various setting signals are transmitted from the remote controller 40 to the controller 30, and signals indicating the operating status of the hot water supply device 1 are transmitted from the controller 30 to the remote controller 40. Is sent.

  Then, the controller 30 is configured so that the temperature of hot water supplied to the downstream side of the location where the hot water supply pipe 3 is connected to the bypass pipe 5 (hereinafter referred to as hot water supply temperature) becomes the target hot water temperature set by the remote controller 40. The hot water supply control means 31 for executing the “hot water supply operation” for controlling the heating amount (combustion amount) of the gas burner 20, and the bypass proportional valve 13 when the amount of water entering the water supply pipe 2 decreases during the execution of the “hot water supply operation”. Bypass ratio control means 32 for performing control to change the bypass ratio, which is the ratio of the flow rate of water flowing through the bypass pipe 4 to the flow rate of water flowing through the heat exchanger 4, and to suppress overshoot of the hot water supply temperature; It has.

  Hereinafter, the execution procedure of the “hot water supply operation” will be described with reference to the flowchart shown in FIG. 2. When the hot water supply device 1 is in an operation state in which the “hot water supply operation” can be executed by the operation of the remote controller 40 by the user, the controller 30 detects the water entering the water supply pipe 2 by the flow sensor 12 in STEP 1 of FIG. Wait for it.

  When the user opens the currant 6 connected to the tip of the hot water supply pipe 3 and the flow sensor 12 detects water entering the water supply pipe 2, the hot water supply control means 31 proceeds to STEP 2 and proceeds to the burner 20. Ignition processing is performed. The ignition process of the burner 20 is performed by opening the gas source valve 22 and the gas proportional valve 21 with the spark discharge generated in the ignition electrode 23 after the combustion fan 24 is operated.

  In subsequent STEP 3, the hot water supply control means 31 controls the combustion amount of the gas burner 20 by adjusting the opening of the gas proportional valve 21 and the rotational speed of the combustion fan 24 so that the hot water supply temperature becomes the target hot water supply temperature. Specifically, for example, when the detected temperature of the incoming water temperature sensor 10 is 10 ° C., the target hot water supply temperature is 40 ° C., and the incoming water amount detected by the flow rate sensor 12 is 20 l / min, it is indicated by X in FIG. In this way, by controlling the combustion amount of the gas burner 20 with the target heating amount of the gas burner 20 set to 600 kcal / min, the hot water supply temperature Ts is set to 40 ° C. as shown in the following equation (1).

Ts = 600 (kcal / min) / 20 (l / min) + 10 (° C) = 40 (° C) (1)
The bypass ratio is set so that the temperature of the hot water of the heat exchanger 4 is not less than a preset lower limit temperature (for example, 50 ° C.) in order to prevent low temperature corrosion, and is set to 0.33 in X of FIG. Has been. The hot water supply control means 31 corrects the target combustion amount of the gas burner 20 when the hot water supply temperature detected by the hot water supply temperature sensor 11 deviates from the target hot water supply temperature.

  In subsequent STEP 4, the hot water supply control means 31 determines whether or not the incoming water amount Fl detected by the flow sensor 12 has decreased by a predetermined level (for example, 10%) or more. When the incoming water flow rate Fl decreases by more than the predetermined level, the process branches to STEP10.

  STEP10 to STEP13 are processes by the bypass ratio control means 32, and the bypass ratio control means 32 calculates a corrected bypass ratio Brc for correcting the hot water supply temperature in STEP10. Here, when the incoming water flow rate Fl decreases, the hot water supply control means 31 decreases the heating amount of the gas burner 20 by the temperature control of STEP 3 accordingly.

  In addition, the overshoot of the hot water supply temperature increases as the degree of decrease in the incoming water amount Fl increases. Therefore, the determination condition for the decrease in the incoming water amount Fl in STEP 4 is performed by setting the degree of decrease in the incoming water amount Fl further, for example, when the incoming water amount Fl is reduced by 50%. You may make it suppress extreme overshoot.

  For example, as shown in Y of FIG. 3, in the state where the temperature control is executed in the state of X, when the incoming water amount Fl is halved from 20 l / min to 10 l / min, the hot water supply temperature is set to 40 ° C. The necessary heating amount of the gas burner 20 is also halved from 600 kcal / min (corresponding to the first heating amount of the present invention) to 300 kcal / min (corresponding to the second heating amount of the present invention). However, even if the heating amount of the gas burner 20 is reduced in this way, the heating amount with respect to the water flowing through the heat exchanger 20 is immediately 300 kcal / min due to the influence of the residual heat due to the heat capacity of the heat exchanger 20. Will not decrease.

  Therefore, heating of the water in the heat exchanger 20 becomes excessive, and as shown by Y, the tapping temperature from the heat exchanger 4 becomes 90 ° C. which is increased by the heating amount (40 kcal / l · min) due to the residual heat. . As a result, the hot water supply temperature is about 70 ° C. according to the following equation (2), and greatly overshoots the target hot water supply temperature of 40 ° C.

Ts = 1 / 1.33 × 90 (° C.) + 0.33 / 1.33 × 10 (° C.)
= 70.14 (℃) (2)
Therefore, the bypass ratio control means 32 performs control to change the bypass ratio by the bypass proportional valve 13 and suppress the overshoot. Specifically, first, in STEP 10, a corrected bypass ratio Brc that can maintain the hot water supply temperature Ts near the target hot water supply temperature is calculated. For example, when the amount of incoming water is halved (20 l / min → 10 l / min) from the state X in FIG. min) to be estimated at 300 kcal / min.

By該余heat, hot water temperature T _HEX of the heat exchanger 4, the following equation (3) is assumed to be a 90 ° C..

T _HEX = 10 (℃) + 40 (kcal / l ・ min) (for gas burner)
+ 40 (kcal / l · min) (remaining heat) (3)
Then, when the tapping temperature of the heat exchanger 4 is 90 ° C., a corrected bypass ratio Brc at which the hot water supply temperature Ts becomes 40 ° C. which is the target hot water supply temperature is calculated by the following equation (4).

40 (° C.) = 1 / (1 + Brc) × 90 (° C.) + Brc / (1 + Brc) × 10 (° C.)
(4)
From the above equation (4), Br = 1.67 is obtained. Further, in subsequent STEP 11, the bypass ratio control means 32 calculates a correction time tb with the bypass ratio as the correction bypass ratio Brc by the following equation (5).

tb = V _HEX ÷ {10 (l / mim) × (1 / (1 + Brc) / 60) (5)
Where V _HEX is the amount of water held in the heat exchanger 4 and Brc is the corrected bypass ratio.

  In this case, the correction time tb is a time required until all the water located in the heat exchanger 4 is discharged when the incoming water amount Fl decreases.

  Then, the bypass ratio control means 32 sets the bypass ratio to the corrected bypass ratio Brc in STEP 12 and executes a loop composed of STEP 13 and STEP 20. Then, when the correction time tb has passed in STEP13, the process returns to STEP3. Moreover, when the water flow sensor 12 no longer detects water entering the water supply pipe 2 in STEP 20, the process proceeds to STEP 6. In this case, the hot water supply control means 31 extinguishes the gas burner 20 and ends the “hot water supply operation”.

In this way, by setting the bypass ratio to the corrected bypass ratio Br until the bypass correction time t _B elapses, it is located in the heat exchanger 4 when the incoming water amount Fl decreases, and is heated excessively due to residual heat. The flow rate of hot water discharged from the exchanger 4 decreases, and the hot water supply temperature is maintained near the target hot water supply temperature. Therefore, it is possible to suppress the occurrence of overshoot of the hot water supply temperature with respect to the target hot water supply temperature.

  In order to prevent boiling in the heat exchanger 4 due to a decrease in the flow rate of water flowing through the heat exchanger 4, an upper limit (for example, 2.0) is provided in the bypass ratio, and the upper limit is not exceeded. The bypass ratio may be controlled by the bypass ratio control means 32 within the range. Furthermore, the time for controlling the bypass ratio may be limited according to the setting of the upper limit of the bypass ratio. For example, when the upper limit of the bypass ratio is 2.5, the time for controlling the bypass ratio is limited to within 3 seconds, and when the upper limit of the bypass ratio is 2.6, the time for controlling the bypass ratio is 2 When the upper limit of the bypass ratio is 2.8, the time for controlling the bypass ratio may be limited to within one second.

  Moreover, in this Embodiment, although the incoming water temperature sensor 10 was provided as an incoming water temperature detection means of this invention, the incoming water temperature to the feed water pipe 2 is estimated from the detected temperature of the hot water supply temperature sensor 11, and the heating amount of the gas burner 20. The incoming water temperature detecting means of the present invention may be constituted by the means to do.

  Moreover, although the hot water supply apparatus which heats the heat exchanger 4 with the gas burner 20 was shown in this Embodiment, with respect to the hot water supply apparatus which heats a heat exchanger with another kind of heating means, such as an oil burner and an electric heater. The present invention can also be applied.

The whole hot-water supply apparatus block diagram of this invention. The flowchart of a hot water supply driving | operation. Explanatory drawing of the setting of the bypass ratio at the time of the amount of incoming water reduction. The whole block diagram of the conventional hot-water supply apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Hot water supply apparatus, 2 ... Water supply pipe, 3 ... Hot water supply pipe, 4 ... Heat exchanger, 5 ... Bypass pipe, 10 ... Incoming water temperature sensor (incoming water temperature detection means), 12 ... Flow rate sensor, 13 ... Bypass proportional valve (bypass) Ratio changing means), 20 ... gas burner, 30 ... controller, 31 ... hot water supply control means, 32 ... bypass ratio control means

Claims (3)

A heat exchanger connected to a water supply pipe and a hot water supply pipe for heating the water supplied from the water supply pipe and discharging the hot water to the hot water supply pipe, heating means for heating the heat exchanger, and bypassing the heat exchanger A bypass pipe for communicating the water supply pipe and the hot water supply pipe, and a bypass ratio changing means for changing a bypass ratio which is a ratio of a flow rate of water flowing through the bypass pipe to a flow rate of water flowing through the heat exchanger And an incoming water temperature detecting means for detecting a temperature of water supplied from the water supply pipe to the heat exchanger, and a flow rate for detecting a total flow of water supplied from the water supply pipe to the heat exchanger and the bypass pipe. Detection means;
The detected temperature of the incoming water temperature detecting means and the detected flow rate of the flow rate detecting means so that the temperature of hot water supplied to the downstream side of the hot water pipe connected to the bypass pipe becomes a predetermined target hot water temperature. A hot water supply device comprising a hot water supply control means for executing a hot water supply operation for controlling the heating amount of the heating means,
During execution of the hot water supply operation, the detected flow rate of the flow rate detecting means is reduced, and the hot water supply control means is controlled to reduce the heating amount of the heating means from the first heating amount to the second heating amount. Sometimes, the amount of remaining heat in the heat exchanger is estimated in accordance with the difference between the first amount of heating and the second amount of heating, and the increase in the tapping temperature of the heat exchanger due to the amount of remaining heat is cancelled. Further, a hot water supply apparatus comprising a bypass ratio control means for controlling the bypass ratio via the bypass ratio changing means.   The bypass ratio control means starts from the time when the detected flow rate of the flow rate detecting means decreases until the hot water existing in the heat exchanger at that time is discharged from the heat exchanger. The hot water supply apparatus according to claim 1, wherein the bypass ratio is controlled via the bypass ratio changing means so as to cancel out the rise in the temperature of the hot water discharged from the heat exchanger due to the amount of heat.   The bypass ratio control means includes the bypass ratio changing means via the bypass ratio changing means so as to cancel the rise in the temperature of the hot water discharged from the heat exchanger due to the amount of residual heat in a range where the bypass ratio is equal to or less than a predetermined upper limit. The hot water supply apparatus according to claim 1 or 2, wherein a bypass ratio is controlled.

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