JPH07190395A - Hot water supply heater - Google Patents

Abstract

PURPOSE:To make it possible to use a heat exchanger at a low-temperature corrosion region or a proper temperature range which is out of a boiling region and improve water output properties when resupplying hot water as,well CONSTITUTION:To comply with hot water supply requirements, a control means 9 adds up a required definite value to a setting temperature and computes so as to set a target boiling up temperature of a heat exchanger 1 to a proper range which is out of a low temperature corrosion region or a boiling up region and further computes a target distribution ratio between hot water from the heat exchanger 1 and water from a bypass line 4 based on the computed target boiling up temperature, the setting temperature and a water inlet temperature and provides a function which controls the opening of a bypass valve 8 based on the target distribution ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called bypass mixing type water heater that mixes hot water from a heat exchanger with water from a bypass to discharge hot water at an arbitrary set temperature,
Particularly, the present invention relates to improvement of a device provided with a bypass valve for varying the amount of bypass water.

[0002]

2. Description of the Related Art A general structure of a bypass mixing type water heater is shown in FIG. In the figure, 50 is a heat exchanger, 51 is a water inlet, 52 is a hot water outlet, 53 is a bypass, 54 is a confluence section, 55 is a burner, 56 is a plug such as a calan, 57 is a bypass valve, and 58 is a control means. Is. A water inlet path 51 is connected to the water inlet end of the heat exchanger 50, and a hot water outlet 52 is connected to the discharge end of the heat exchanger 50, and a bypass passage 53 is connected to the water inlet 51 and the hot water outlet 52. Has been done. The joining portion of the tap passage 52 and the bypass passage 53 is the merging portion 5.
It is 4. The bypass valve 57 is provided in the middle of the bypass passage 53 and variably adjusts the amount of bypass water. The control means 58 controls the heating temperature by the heat exchanger 50 and the opening degree of the bypass valve 57.

By the way, the applicant of the present application has proposed the following method for controlling the hot water supply request. It feed-forwards the combustion capacity of the burner 54 so that the mixed tap water temperature at a distribution ratio (for example, hot water: water = 1: 1) that makes the amount of bypass water by the bypass valve 57 constant becomes the set temperature required by the user. In addition to the control, the amount of bypass water by the bypass valve 57 is feedback-controlled based on the deviation between the set temperature and the actual mixed hot water temperature, so that the hot water is discharged at about the set temperature. The reason why the distribution ratio is fixed by the feedforward control is that the operation response speed of the bypass valve 57 is slow.

[0004]

In the case of the above-mentioned conventional device,
The target heating temperature of the heat exchanger 50 is set to be considerably low in the summer when the incoming water temperature is high, while the target heating temperature is set to be considerably high in the winter when the incoming water temperature is low. In extreme cases, heat exchanger 50 during summer
The target heating temperature of is set to a low temperature corrosion range (a temperature range where the heat exchanger is likely to be condensed), and in winter, the target heating temperature of the heat exchanger 50 is set to a boiling range.
There is concern that the safety and durability of the equipment may decrease.

Further, in the conventional apparatus, the hot and cold water phenomenon peculiar to the bypass mixing type water heater, that is, when the hot water is temporarily stopped and then reheated, the heat exchanger 50 is post-heated or spontaneously dissipates heat. Even if the mixed hot water temperature from 56 temporarily rises or falls, the feedback control for increasing or decreasing the opening of the bypass valve 57 functions to improve the hot water discharge characteristics. However, especially in summer or winter when the water temperature is high, a certain distribution ratio (for example, hot water: water = corresponding to the target heating temperature).
Since it is necessary to increase the amount of change from 1: 1) to a distribution ratio by feedback control during re-hot water supply (for example, water side fully open or water side fully closed), the operation of the bypass valve 57 cannot follow and the cold temperature is maintained. There is concern that the effect of suppressing the water phenomenon will be insufficient.

In view of such circumstances, the present invention makes it possible to use the heat exchanger in an appropriate temperature range outside the low temperature corrosion area or the boiling area regardless of whether the incoming water temperature is high or low. The challenge is to be able to improve the characteristics.

[0007]

According to the present invention, hot water from a heat exchanger is mixed with water from a bypass passage to discharge hot water at an arbitrary set temperature. The bypass passage is provided in the middle of the bypass passage. In a bypass mixing type hot water supply device comprising a bypass valve for variably controlling the amount of water, and a control means for controlling the heating temperature by the heat exchanger and the opening degree of the bypass valve,
Configure as follows.

In the present invention, the control means adds a required constant value to the set temperature so that the target heating temperature of the heat exchanger becomes an appropriate range outside the low temperature corrosion region or the boiling region in response to the hot water supply request. The target distribution ratio between the hot water from the heat exchanger and the water from the bypass passage is calculated based on the calculated target heating temperature, the set temperature, and the incoming water temperature, and based on this target distribution ratio. It has a function of controlling the opening degree of the bypass valve.

[0009]

According to the present invention, while the distribution ratio is variably controlled when hot water is requested, the target heating temperature of the heat exchanger is set to a predetermined constant value so as to be in an appropriate range outside the low temperature corrosion range or the boiling range. Is set, and the target distribution ratio is calculated in consideration of the target heating temperature, so that the target distribution ratio is set to an intermediate range that is neither too large nor too small.

As a result, the target heating temperature of the heat exchanger does not need to be set too low or too high even in summer or low winter when the water temperature is high, and the distribution ratio at the time of re-hot water supply can be reduced. The amount of change can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the embodiments shown in FIGS. FIG. 1 is a schematic configuration diagram of a water heater, FIG. 2 is a graph showing a change in hot water temperature of a heat exchanger, and FIG. 3 is a graph showing a relationship between a distribution ratio of a bypass valve and a driving step number of the bypass valve. . In this embodiment, an example in which the basic configuration is the same as that of the conventional example is given.

In the figure, 1 is a heat exchanger, 2 is a water inlet channel, 3 is a hot water outlet channel, 4 is a bypass channel, 5 is a confluence section, 6 is a burner, 7 is a front plug such as a calan, 8 is a bypass valve, 9 Is a control means. Reference numeral 10 is a water amount sensor, 11 is an incoming water temperature sensor, 12 is a can body outlet hot water temperature sensor provided on the discharge side of the heat exchanger 1, 1
Reference numeral 3 is a mixed hot water temperature sensor provided in the hot water discharge path 3 downstream of the confluence section 5. Water inlet 2 at the water inlet end of heat exchanger 1.
However, the hot water outlet 3 is connected to the discharge end of the heat exchanger 1, and the bypass passage 4 is connected to the water inlet 2 and the hot water outlet 3.
Are connected respectively. A connecting portion between the hot water passage 3 and the bypass passage 4 forms a merging portion 5. The bypass valve 8 is driven to be opened and closed by a stepping motor (not shown), and the relationship between the opening degree, that is, the number of steps of the stepping motor and the distribution ratio is as shown in FIG.

In this embodiment, the distribution ratio (mixing ratio of hot water from the heat exchanger 1 and water from the bypass 4) is variably controlled when hot water is requested, but the distribution ratio is too large or too small. It is characterized in that it is devised so that it is set to fall within the intermediate range.

Specifically, the control means 9 controls the target heating temperature KTs of the heat exchanger 1, that is, when the hot water supply request is made, that is, when the water input amount Qs detected by the water amount sensor 10 is larger than a predetermined minimum operating water amount MOQ. Calculate by adding the required constant value β (for example, 25 ° C) to the set temperature Ts so that the temperature of the hot water discharged from the can is out of the low temperature corrosion range and the boiling range (see the following formula or reference), and this target heating Detection can body hot water temperature T detected by the can body hot water temperature sensor 12 to the temperature KTs
The gas amount G of the burner 6 is calculated and set by an equation so as to match h, the target distribution ratio ρ is calculated by the following formula, and the opening degree of the bypass valve 8 is controlled based on this target distribution ratio ρ. Yes (feedforward control).
Then, when a deviation occurs between the set temperature Ts and the actual mixed hot water temperature (output of the mixed hot water temperature sensor 13) Tm, the control means 9 determines the bypass valve 8 based on this deviation.
The opening degree of is corrected (feedback control). Further, when the hot water supply is stopped and the hot water is supplied again after a required time has elapsed, the control means 9 performs control for suppressing the cold / hot water phenomenon associated with the hot water supply.

KTs = Ts + β (where β is a constant) ρ = (KTs−Ts) / (Ts−Tc) = β / (Ts−Tc) KTs = ρ · (Ts−Tc) + Ts G = (KTs−Tc ) · Qs If the target distribution ratio ρ calculated by the formula falls within a predetermined range (ρmin ≦ ρ ≦ ρmax), the opening degree of the bypass valve 8 is controlled based on the calculation result, If it doesn't fit into (ρmin>ρ> ρm
As in the conventional case, ax) is such that the target distribution ratio ρ is constant at α (constant), the target heating temperature KTs is calculated by an equation, and the combustion capacity of the burner 6 is controlled based on the calculation result. This means that if the distribution ratio is too small (ρm
If the distribution ratio is too large (exceeds ρmax), the amount of bypass water will increase by a certain amount or more, while the amount of bypass water will decrease by a certain amount or more, and the required hot water supply amount will not be obtained. In addition, it is difficult to suppress the overshoot phenomenon during hot water resupply. Then, the aforementioned ρmin is 0.5, and ρmax is
It is set empirically to 1.3.

Here, an example in which the target heating temperature or distribution ratio of the present embodiment is compared with the conventional example (where the distribution ratio ρ is fixed) will be described.

(1) Set temperature Ts = 50 ° C., incoming water temperature T
When c = 5 ° C., fixed distribution ratio ρ = 1 in the conventional example
Then, the target heating temperature KTs = 95 ° C. is set in the boiling region, and an undershoot phenomenon is likely to occur during re-hot water supply after waiting for a long time. On the other hand, in the case of the present embodiment, the target heating temperature KTs = 75 ° C. and the distribution ratio ρ =
The value is 0.56, and it is not necessary to reach the boiling range, and the response is quick even during re-hot water supply after waiting for a long time, and the undershoot phenomenon is less likely to occur.

(2) Set temperature Ts = 40 ° C., incoming water temperature T
When c = 20 ° C., fixed distribution ratio ρ =
When it is set to 1, the target heating temperature KTs = 60 ° C., which is a low temperature corrosion region, and an overshoot phenomenon is likely to occur during hot water re-supply after a short period of standby. On the other hand, in the case of the present embodiment, the target heating temperature KTs = 65 ° C., the distribution ratio ρ = 1.25, and the low temperature corrosion region is not reached.
In addition, the response is quick even when hot water is re-supplied after a short period of waiting, and the overshoot phenomenon is less likely to occur.

As described above, according to the present invention, the target heating temperature KTs is uniquely set so as to be in a proper range out of the low temperature corrosion region or the boiling region, regardless of whether the incoming water temperature is high or low. Low temperature corrosion and boiling damage of the exchanger 1 are avoided. Further, by setting the bypass ratio within an intermediate range that is neither too large nor too small, the change amount of the distribution ratio at the time of re-hot water supply, that is, the bypass valve 8
The opening control amount of is reduced as much as possible.

[0020]

According to the present invention, in the water heater of the by-bass mixing system, the target heating temperature of the heat exchanger is not set too low or too high even in the summer and winter when the incoming water temperature is high. In addition to making it possible to reduce the amount of change in the distribution ratio at the time of re-hot water supply, it is possible to avoid low temperature corrosion and abnormal heating of the heat exchanger and improve the safety and durability of the equipment. The occurrence of cold and hot water phenomena such as overshoot and undershoot at the time of re-hot water supply can be suppressed and the hot water discharge characteristics can be improved. As described above, the present invention contributes to the improvement of reliability of the water heater.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a water heater according to the present invention.

FIG. 2 is a graph showing changes in hot water temperature of the heat exchanger of the water heater.

FIG. 3 is a graph showing the relationship between the distribution ratio of the bypass valve and the number of drive steps of the bypass valve.

FIG. 4 is a configuration diagram of a conventional water heater.

[Explanation of symbols]

 1 Heat Exchanger 2 Inlet Channel 3 Outlet Channel 4 Bypass Channel 6 Burner 7 Front Plug 8 Bypass Valve 9 Control Means 12 Can Body Outlet Temperature Sensor 13 Mixed Outlet Temperature Sensor

Claims (1)

[Claims] 1. A bypass valve for mixing hot water from a heat exchanger and water from a bypass passage to discharge hot water at an arbitrary set temperature, the bypass valve being provided in the middle of the bypass passage to variably control the amount of bypass water. A hot water supply device comprising a control means for controlling the heating temperature by the heat exchanger and the opening degree of the bypass valve, wherein the control means is a target heating temperature of the heat exchanger for the hot water supply request, the low temperature corrosion Calculated by adding the required constant value to the set temperature so that it is in an appropriate range that deviates from the range and boiling range, and the hot water from the heat exchanger is calculated based on the calculated target heating temperature, set temperature, and incoming water temperature. It has a function of calculating a target distribution ratio with water from the bypass passage and controlling the opening degree of the bypass valve based on this target distribution ratio.
A water heater characterized by that.