JPH056099B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Application and Summary of the Invention) The present invention relates to a heat exchanger for a water heater, etc. The present invention relates to a heat exchanger such as a water heater. This is intended to suppress the generation of condensate within the exchanger.

(Prior art and its problems) A conventional heat exchanger for a water heater has a configuration as shown in FIG. A combination of bypass circuits 2 is adopted, and hot water at a desired temperature can be drawn from a faucet provided downstream from the junction of these two circuits.

In this conventional system, the amount of water passing through the heated tube 11 of the heated circuit 1 is smaller than when the entire amount of water from the inlet is heated by a heat exchanger, so the amount of water passing through the heated tube 11 of the heated circuit 1 is reduced. The temperature of the heating tube 11 increases, making it difficult for drainage to occur.

However, in the case of a type in which the amount of hot water discharged has a wide adjustment range and the temperature of hot water discharged within a wide adjustment range, condensation may occur in the heated tube if the above-mentioned conventional method is simply adopted.

This is because in a type of heat exchanger with a large hot water supply capacity, the total length of the heated tube 11 becomes long, and the temperature of the heated tube at the downstream side of the combustion exhaust flow becomes low. In particular, when a large amount of low-temperature hot water is to be obtained, this tendency becomes remarkable, and the atmospheric gas in the heated tube 11 condenses and drips into the heat exchanger.

In order to eliminate this inconvenience, as shown in FIG. , a detection means 4 for detecting the temperature of this portion is provided at a specific location of the heated circuit 1, and the flow rate ratio adjustment valve 3 is actuated by the output from this detection means, and the patent application No. 61 −95985 (Unexamined Japanese Patent Publication No. 62-
252848).

In this prior art, the temperature of the tube to be heated 11 can be set to a certain temperature or higher by the control signal from the detection means 4, so that the generation of drainage can be prevented.

However, in this prior art, the operation of the flow rate ratio adjustment valve is controlled by the output state caused by the actual heating state of the heated circuit 1, which is so-called feedback control, so that a predetermined control state is achieved. It will take a certain amount of time. Therefore, it is not possible to prevent drainage from occurring during this period.

(Technical Problem) The present invention provides a heated circuit 1 including a heated tube 11 and a bypass circuit 2 that does not involve the heated tube 11.
A flow ratio adjustment valve 3 is inserted into either or both of the circuits between the confluence of the bypass circuit 2 and the heated circuit 1 to the branching point, and this flow ratio adjustment valve is A heat exchanger for a water heater that controls the flow rate ratio of the heated circuit 1 and the bypass circuit 2 in order to maintain the heated pipe 11 at a temperature that does not generate condensation according to the output from the drive circuit. In order to reliably prevent the generation of condensate in the heated tube 11, the technical problem is to maintain the temperature of the heated tube 11 above a certain temperature by forward-forward control.

(Means) The technical means of the present invention taken to solve the above-mentioned technical problem is as follows. The system is equipped with a heat quantity control device that operates a gas proportional control valve 62 inserted into the gas circuit to maintain the hot water temperature at the set temperature by comparing the temperature with the set temperature of the hot water outlet temperature setting device 64. An incoming water temperature detection means 40 is provided to detect the water temperature on the upstream side of the branch point between the circuit 2 and the heated circuit 1, and a bypass circuit is established based on the set temperature of the outlet hot water temperature setting device 64 and the detected temperature of the incoming water temperature detection means 40. 2 and the heated circuit 1 is a calculation drive circuit 3 that calculates a signal value applied to the flow rate ratio adjustment valve 3 that should set the flow rate ratio between the heated circuit 1 and the heated circuit 1 to a ratio that does not cause drainage to occur in the heated pipe 11.
0 is provided, and this arithmetic drive circuit 30 is used as a drive circuit for driving the flow rate ratio adjustment valve 3. (See Figure 1).

(Function) The above technical means of the present invention functions as follows.

When the heat exchange action is being performed, the fluid supplied from the upstream side of the heat exchanger is passed through the bypass circuit 2.
and the heated circuit 1 to the downstream side. The fluid passing through the heated circuit 1 undergoes heat exchange within the heat exchanger, and on the downstream side of the confluence, the heated fluid and the non-heated fluid are mixed to form a fluid at a desired temperature.

Here, the amount of heat for heating the heated tube 11 is set to a predetermined amount of heat by the output of the gas proportional control valve 62. At this time, the opening degree of the gas proportional control valve 62 is controlled by comparing the detected hot water temperature downstream of the confluence of the bypass circuit 2 and the heated circuit 1 with the detected temperature.
The amount of heat is set to a predetermined value. The hot water temperature is
Since it is determined by the amount of heat supplied to the heat exchanger, the thermal efficiency of this heat exchanger, and the total flow rate of bypass circuit 2 and heated circuit 1, the setting of the flow rate ratio between bypass circuit 2 and heated circuit 1 is determined. Regardless of the situation, the hot water temperature will be maintained at the set temperature by the control described above.

At the same time, the calculation drive circuit 30 calculates the operating amount of the flow rate ratio adjustment valve 3 based on the set temperature of the outlet hot water temperature setting device 64 and the detected temperature of the incoming water temperature detection device 40, Then, the flow rate ratio adjustment valve 3 operates, and the flow rate ratio between the bypass circuit 2 and the heated circuit 1 is set to a predetermined ratio,
The temperature on the heated tube 11 side is maintained to such an extent that no drainage occurs. That is, the hot water temperature setting device 64
When the temperature of the heated tube 11 tends to shift to the lower temperature side depending on the set value of increases. As a result, the temperature on the heated tube 11 side rises and is maintained at a level that does not cause drainage. Further, contrary to the above, when the temperature of the heated circuit 1 tends to shift to the high temperature side, the operation is reversed to that described above to keep the temperature of the heated circuit 1 constant.

Incidentally, even if the flow rate ratio changes as described above, the tapping temperature is maintained at the set temperature by the action of the gas proportional control valve 62 for the reasons described above.

(Effects) Since the present invention has the above configuration, it has the following unique effects.

The heated circuit 1 side is always set at a temperature that does not cause condensation, and the conditions for maintaining this temperature are set in advance in accordance with changes in the inlet water temperature and changes in the outlet temperature setting. Inconveniences such as drainage generated in the pipe 11 and dripping into the heat exchanger can be reliably prevented.

In addition, the inside of the heated tube 11 is not heated to an abnormally high temperature, and boiling inside the heat exchanger can be prevented.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 2 to 5.

In the first embodiment shown in FIGS. 2 and 3, in order to enable large-capacity heat exchange, as shown in FIG.
The heated tube group 13, 14 consisting of 11 is made into two stages,
A gas burner 15 is employed as a heating source. Therefore, the groups of heated tubes 13 and 14 are arranged in upper and lower stages in the can body 10 and connected to each other, and the lower part of the group of heated tubes 14 is defined as a combustion chamber 16.
In order to increase the combustion capacity in this combustion chamber,
A fan 17 is used to feed combustion air.

Further, a bypass circuit 2 is provided outside the can body 10, and both ends of the heated tube groups 13 and 14 are communicated with each other. Therefore, a portion of the water flowing through the water circuit flows from the branch point 21 to the confluence point 22 without passing through a heat exchanger.

Next, as the incoming water temperature detection device 40 described above, a first thermistor 41 that detects water temperature or tube wall temperature is employed. The first thermistor 41 is provided on the upstream side of the branch point 21, and a water proportional control valve 31 serving as the flow ratio adjustment valve 3 is inserted into the bypass circuit 2 near the confluence point 22.

The water proportional control valve 31 has a known configuration, and is configured to compare and calculate the voltage applied to the first thermistor 41 and the set voltage of the hot water temperature setting device 64, and output an operation signal according to this difference. The arithmetic drive circuit 30 changes the opening degree of the valve.

Note that a second thermistor 61 for separately detecting the outlet temperature is provided on the downstream side of the confluence point 22, and a gas proportional control valve 62 is provided in the gas circuit 7 to the gas burner 15.
is inserted. The gas proportional control valve 62 changes the combustion amount of the gas burner by changing the valve opening depending on the output from the second drive circuit 63. The output signal and the output signal from the second thermistor 61 are compared by the second drive circuit 63, and an operation signal output corresponding to the difference is applied to the gas proportional control valve 62.

Therefore, regardless of the flow rate ratio between the heated circuit 1 and the bypass circuit 2, and regardless of the change in the amount of hot water, the output of the gas proportional control valve 62 will
The hot water temperature is maintained at the set temperature.

Therefore, when the hot water outlet temperature is set by the hot water outlet temperature setting device 64, the gas proportional control valve 62 operates in an output state that corresponds to the heated circuit-bypass circuit distribution ratio at this time, and the hot water outlet temperature becomes a predetermined temperature. Set. At the same time, based on the relationship between the inlet water temperature, the set value of the outlet water temperature, and the amount of gas required to heat the heated pipes 11, 11 of the heated circuit to a temperature at which no condensation occurs (for example, 55°C), calculation is performed. circuit 3
0 calculates the operation amount of the flow rate ratio adjusting valve 3 and performs an output operation according to the result of this calculation, so that the flow rate ratio between the heated circuit 1 and the bypass circuit 2 is set to a predetermined value. Thereafter, even if the amount of hot water that comes out changes, the gas proportional control valve 62 performs a control operation while maintaining this set flow rate ratio, and the hot water temperature is maintained at the set temperature.

This will be explained in more detail using mathematical formulas.

First, set hot water temperature: (T), water input temperature:
(T ₀ ), heated tube heating temperature: (T ₁ ), total flow rate (Q), heated circuit flow rate (Q ₁ ), bypass circuit flow rate (Q ₂ ), and the bypass circuit flow rate and the heated circuit flow rate. If the ratio of is (k), then the following formula holds true.

Q ₂ /Q ₁ = k ...... Q = Q ₁ + Q ₂ ...... Since the total amount of heat exchange corresponds to the amount of heating of the heated circuit 1, Q ₁ (T ₁ - T ₀ ) = Q (T - T ₀ ) ...... From the formula, Q = (1 + k) Q ₁ Substituting this into the formula, Q ₁ (T ₁ - T ₀ ) = (T - T ₀ )・(1 + k) Q ₁
...... Therefore, the following formula holds true.

k = [(T ₁ - T ₀ ) / (T - T ₀ )] - 1 In this way, if the above ratio (k) is set from the incoming water temperature and the set hot water temperature, regardless of the amount of hot water coming out, the heated The amount of heating required for the tubes 11, 11 will be determined.

Therefore, in the calculation drive circuit 30, the heated tube 1
Minimum required heating temperature for items 1 and 11 (e.g. 35℃)
Then, the distribution ratio is calculated from the inlet water temperature and the outlet hot water set temperature. Based on this calculation result, the first proportional control valve 31 as the flow rate ratio adjustment valve 3 operates, and after that, the output of the gas proportional control valve 62 causes the outlet hot water temperature to be maintained at the set temperature regardless of the change in the amount of hot water. will be maintained.

As described above, the combination of two proportional control valves allows the temperature and amount of hot water to be varied over a wide range, and prevents condensate from forming and dripping in the heated pipe within this adjustment range.

In the first embodiment described above, the water proportional control valve 31 is used as the flow rate ratio adjustment valve 3 and is provided at the downstream end of the bypass circuit 2.
The insertion position of the bypass circuit 2 may be set at any position of the bypass circuit 2.

In the case of the first embodiment, the flow rate ratio of both circuits is changed by adjusting the flow rate of the bypass circuit 2, but it is also possible to directly change the flow rate ratio.

As this method, for example, a configuration in which a flow ratio adjusting valve 3 as shown in FIG. 4 is inserted into the confluence point 22 or the branch point 21 can be adopted.

In the embodiment shown in the figure, the valve body 32 of the flow rate ratio adjusting valve 3 faces both the outlets of the bypass circuit 2 side and the heated circuit 1 side at the confluence point 22, and this valve body 32 is connected to the output mechanism. The valve body 32 is connected to an output shaft 33a of the valve body 33, and the position of the valve body 32 is changed by moving the output shaft back and forth. Therefore, when the valve body 32 is moved by the output mechanism 33 so that the degree of blockage on the heated circuit 1 side increases, the flow rate ratio of this circuit is reduced, and conversely, the flow rate ratio on the bypass circuit 2 side is reduced. Increased. In other words, the ratio between the flow rate on the bypass circuit 2 side and the flow rate on the heated circuit 1 side changes directly.

Then, the distribution ratio is calculated from the relationship between the incoming water temperature and the set temperature, and the output mechanism 3
The operation signal output No. 3 is input from the arithmetic drive circuit 30 to the output mechanism. In addition, in the same figure, the valve body 32 is placed facing the confluence point 22, but this is
You may have them face 1.

Further, even if the flow ratio adjusting valve 3 is provided on the inlet side to the heat exchanger as shown in FIG. 5, the above-mentioned effects of the present invention will not change.

Furthermore, as shown by the two-dot chain line in FIG. Therefore, by setting the flow rate to a restricted state, it is possible to prevent problems such as not being able to get hot water at the set temperature even when the incoming water temperature is extremely low. In this case, the calculation drive circuit 30 is added with a calculation function for driving the total water flow restriction valve 42 by comparing the incoming water temperature and the set temperature.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an explanatory diagram of the first embodiment, Fig. 3 is a plan view of a group of heated tubes, and Fig. 4 is an explanatory diagram of the main parts of the second embodiment. FIG. 5 is an explanatory diagram of the third embodiment, FIG. 6 is an explanatory diagram of the conventional example, and FIG. 7 is an explanatory diagram of the prior example. ... Heated pipe, 2 ... Bypass circuit, 3 ... Flow ratio adjustment valve, 30 ... Arithmetic drive circuit, 40 ... Incoming water temperature detection means, 62 ... Gas proportional control valve, 64 ... Output hot water temperature setting device .

Claims (1)

[Claims] 1 A heated circuit 1 equipped with a heated tube 11 and a bypass circuit 2 that does not pass through the heated tube 11, and any point between the confluence of the bypass circuit 2 and the heated circuit 1 and the branch point or both circuits,
In addition to inserting the flow rate ratio adjustment valve 3, this flow rate ratio adjustment valve is connected to the heated circuit 1 and the bypass in order to maintain the heated pipe 11 at a temperature that does not cause drainage, depending on the output from its drive circuit. circuit 2
In the water heater heat exchanger that controls the flow rate ratio of Gas proportional control valve 6 inserted into the gas circuit by comparing the set temperature and
Incoming water temperature detection means 40 is equipped with a heat amount control device that operates 2 to maintain the outlet water temperature at the set temperature, and detects the water temperature upstream of the branch point between the bypass circuit 2 and the heated circuit 1. The flow rate ratio of the bypass circuit 2 and the heated circuit 1 should be set to a ratio that does not generate drain in the heated pipe 11 based on the set temperature of the outlet hot water temperature setting device 64 and the detected temperature of the inlet water temperature detector 40. A heat exchanger for a water heater, which is provided with an arithmetic drive circuit 30 that calculates a signal value applied to a flow rate ratio adjustment valve 3, and uses this arithmetic drive circuit 30 as a drive circuit for driving the flow rate ratio adjustment valve 3.