JPH0650238B2 - Heat recovery device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat recovery device for recovering heat from heat source water such as hot waste water.

[Prior art]

BACKGROUND ART In recent years, it has been widely practiced to recover and utilize heat from hot water, hot water from a geothermal power plant, cooling water from a power plant, and the like.

[Problems to be solved by the invention]

However, when recovering heat from such warm wastewater as heat source water, (a) the amount of water varies with time (variation within a day, seasonal variation, etc.) and is not constant.

(b) Since it contains a large amount of scale, it tends to adhere to the heat transfer surface of the heat exchanger and the heat transfer state deteriorates.

(c) It is difficult to measure the flow rate with a flow meter because it contains a large amount of scale and other dust.

It was a problem.

Of these, for example, in order to deal with (b), it is necessary to clean the heat transfer surface of the heat exchanger, for example, the inside of the heat transfer tube in the case of the shell and tube type, and for that reason, a brush or sponge is placed in the heat transfer tube. A means has been developed for cleaning a cleaning body such as a ball by reciprocatingly driving it with the fluid force of heat source water.

However, even in this case, (a) above becomes a problem. That is, the heat source water is usually introduced to the heat exchanger as it is, or even if it is passed through a tank on the way, it is merely for precipitation,
The heat source water was supplied to the heat exchanger at the same flow rate as the sampled flow rate. Therefore, the amount of heat source water varies, and when it decreases, the supply flow rate to the heat exchanger also decreases, and the flow velocity in the heat transfer tube also decreases. In order to drive the cleaning material, a certain lower limit flow velocity is required, and when the flow rate is below the corresponding lower limit flow rate, the cleaning material cannot be driven. In addition, when the flow velocity decreases, the scale is likely to adhere to the heat transfer tube, increasing the resistance of the cleaning material and further increasing the lower limit flow rate, which is a bad condition,
In addition, heat transfer conditions also deteriorate.

In this way, when recovering heat using warm wastewater as the heat source water, the amount of scale adhered to the heat transfer surface in the heat exchanger increases when the supply amount of the heat source water is not constant and decreases. Conditions worsen and the amount of heat recovered decreases. Further, in the case of using the cleaning material driven by the fluid force, there is a problem that the cleaning material cannot be moved when the flow rate becomes less than the drivable lower limit flow rate.

The present invention solves the above problems in the conventional one,
An object of the present invention is to provide a heat recovery device that can secure the supply amount of heat source water to the heat exchanger at or above the lower limit flow rate even if the inflow amount of heat source water decreases.

[Means for solving problems]

The present invention, as a means for solving the above problems,
In a heat recovery device equipped with a heat exchanger that recovers the heat of the heat source water and gives heat to the fluid to be heated, a heat source water inlet chamber having an inlet part of the heat source water and a heat source water that has passed through the heat exchanger are A heat source water return chamber having a return portion for receiving, a communication passage communicating between the inlet chamber and the outlet chamber so as to move the heat source water, and a heat source from the inlet chamber to the heat exchanger. A supply path for guiding water, a return path for returning heat source water from the heat exchanger to the return part of the return chamber, and a pump for transferring the heat source water through the supply path, the heat exchanger and the return path. And an outlet part which communicates with the return chamber and prevents the water level in the return chamber and the inlet chamber from exceeding a predetermined level, and a heat recovery device.

[Action]

The present invention is configured as described above, as a heat source water flow path,
Inlet room → Inlet room → Supply path → Heat exchanger → Return path → Return room → Exit section In addition to the main path, the entrance room → Supply path → Heat exchanger → Return path → Return room → Inlet room Can be formed. Since the outlet part communicates with the return chamber, the communication part further communicates with the inlet chamber, and even if the raw water flow rate q _i flowing from the inlet part into the inlet chamber changes, the same flow rate as the inflow amount q _i. The heat source water is discharged at. Some flow by the pump in this condition, for example if flowing a lower flow rate q _n or more flow to the supply path, flow rate q _i is decreased, if q _{i <be} a q _n q _n -
Since the flow rate having a difference of q _i circulates through the communication path and the circulation path, a flow rate _{equal to} or higher than a predetermined lower limit flow rate q _n is ensured in the heat exchanger, so that scale adhesion increases or cleaning material cannot be driven. Trouble can be prevented.

When q _i > q _n , the flow rate q _x supplied to the heat exchanger by the pump is preferably a flow rate commensurate with q _i .
This is because when q _x is too large compared to q _i, there is a large amount of wasteful circulation, resulting in a large wasteful power consumption of the pump, and q _i
If the amount is too small compared with the above, the high temperature heat source water in the inlet chamber flows back through the communication passage, enters the return chamber, and escapes from the outlet portion, and is discarded without being recovered.

〔Example〕

 Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 is a tank body, which is divided into an inlet chamber 3 and a return chamber 4 by a partition plate 2, both chambers are communicated with each other by a communication passage 5, and the raw heat water contained therein is Due to the water level difference in the chamber, the movement is performed through the communication passage 5.
Reference numeral 6 is a flow pipe for the raw heat water as an inlet portion, and 7 is provided with an overflow outlet 8 which communicates with the return chamber 4 and prevents the water level of the return chamber 4 and the water level of the inlet chamber 3 from exceeding a predetermined water level. It is an outlet pipe as an outlet portion.

Reference numeral 9 denotes a shell-and-tube heat exchanger, which is configured to move the cleaning material 11 in the heat transfer tube 10 by a water flow for cleaning. Reference numeral 12 is a switching valve as a switching mechanism that switches the flow direction in the heat transfer tube 10 between forward and reverse directions. In the state of the solid line shown, the heat source water flows in the direction of the arrow of the solid line, and the cleaning material 11 is housed in the container at the right end in the first pass and the left end in the second pass. If the switching valve 12 is switched as shown by the dotted line, the heat source water flows in the opposite direction as shown by the dotted line of the arrow,
At that time, the cleaning material 11 moves while cleaning the inside of the heat transfer tube 10 and enters the container at the opposite end.

13 is a supply path for guiding the heat source water in the inlet chamber 3 to the switching valve 12, 14 is a path for returning raw heat water from the switching valve 12 to a return pipe 15 as a return part of the return chamber 4, 16 is a supply path 13, heat exchange It is a pump for transferring the heat source water through the container 9 and the return path 14.

The inlet chamber 3 may be provided with a baffle plate 17 so that the high-temperature heat source water flowing from the inflow pipe 6 does not directly enter the communication passage 5 and escape to the return chamber 4.

18 is a temperature detector for detecting the inlet temperature T ₁ which is the temperature of the heat source water in the inlet chamber 3 (or in the inflow pipe 6), and 19 is the supply path 1
A temperature detector for detecting a supply temperature T ₂ which is a heat source water temperature from the vicinity of the starting point of 3 to the inlet of the inflow side heat transfer tube of the heat exchanger 9, and 20 is a return tube from the outlet of the outflow side heat transfer tube of the heat exchanger 9. A temperature detector for detecting a return temperature T ₃ which is a heat source water temperature up to 15; a temperature detector 21 for detecting an outlet temperature T ₄ which is a heat source water temperature near the outlet pipe 7; a temperature detector 18; , 19, 20, 21 from temperatures T ₁ , T ₂ , T ₃ ,
It is a control device that inputs a signal relating to T ₄ , processes it, and sends an operation signal for flow rate control to the pump 16. Reference numeral 23 is a flow rate detector.

Examples of the flow rate control means include control of the rotation speed of the pump 16, flow rate control by a flow rate control valve on the outlet side, and algebraic control of the pump.

The operation will be described.

The heat source water inflow amount from the inflow period 6 is the inflow amount q _i , and the pump 16
The heat source water flow rate (that is, the flow rate returning from the return interval 15 to the return chamber 4) passing through the heat exchanger 9 by the supply amount q _x , and the heat source water flow amount overflowing and flowing out from the outlet pipe 7 by the outflow amount q ₀ , The heat source water flow rate bypassed from the return chamber 4 to the inlet chamber 5 (this direction is positive) through the communication passage 5 is defined as a bypass amount q _m .

In the state where the steady operation is performed, the outflow is caused by the overflow, so that q ₀ ≈q _i (1). By controlling the pump 16, the flow rate control is performed so that the supply flow rate q _x corresponds to the inflow rate q _i such that q _x ≈q _i (2). At this time, q _m ≈0 (3), and there is almost no bypass flow through the communication passage 5.

The flow rate control method in this case will be described later.

When the inflow quantity q _i decreases, the supply flow rate q _x also decreases by the flow rate control according to the decrease. The supply flow rate q _x, the rotation speed of the pump at that time, the opening degree of the flow control valve, is estimated by such number of operating pumps, the lower limit flow rate q _{n (above} which it is allowed to heat exchanger 9 As described below, due to scale adhesion, immobilization of cleaning material, etc.), the supply flow rate q _x is kept constant q _{n in} preference to the signal from the flow rate control system.
Keep as, opening speed or the flow control valve of the pump 16, to ensure such operation algebra maintaining the lower flow rate q _n to.

Even if the inflow amount q _i decreases, the bypass flow amount q _m increases and compensates, so the circulation amount does not change, and the outflow amount is q ₀ ≈
Since the lower limit flow rate q _n flows in the heat exchanger 9 while maintaining q _i , it is possible to prevent problems such as scale adhesion and immobilization of the cleaning material.

Next, a flow rate control method will be described.

In the above, in order to protect the heat exchanger 9 at the time of an abnormality in which the flow rate q _i decreases and becomes equal to or less than the lower limit flow rate q _n , the supply flow rate q _x is kept constant (q _n )
Although the description of the means that in the following the q _i
This is a flow rate control method during normal operation _where > q _n .

During normal operation, the supply flow rate q _x is the inflow quantity q as shown in equation (2).
Controlled to meet _i .

In this case, if q _x is too large compared to q _i , the bypass flow rate q _m passing through the communication passage 5 becomes large, the useless circulation amount increases, and the useless power consumption of the pump 16 increases.

In order to prevent this, the inflow amount q _i is measured, and the flow rate of the pump 16 or the throttle of the flow control valve is adjusted so as to correspond to it.
Alternatively, when controlling the number of units, it is sufficient to adjust the number of operating pumps.However, as described in (c) above, the warm wastewater contains a large amount of scale and dust, which hinders the operation of the flowmeter. , Cause an error.

In order to prevent this, the flow rate is not used as a detection target, only the temperature of each part is detected, and the supply flow rate q commensurate with the inflow rate q _i is detected.
_A flow rate control method capable of selecting _x will be described below with three examples.

The first flow rate control method uses the inlet temperature T ₁ and the supply temperature T _1.
This is a method in which only ₂ is detected.

In this method, when the supply flow rate q _x is excessively large compared to the inflow quantity q _i , the bypass flow rate q _m also becomes large. The temperature of the heat source water in the return room is approximately T ₃ , which is lower than the inlet temperature T ₁ , so that if the bypass flow rate q _m is large, the supply temperature T ₂ that is the temperature of the heat source water after mixing becomes low. The focus is on that.

That is, the temperature difference ΔT of T ₁ −T ₂ = ΔT is set so that ΔT ₀ ≧ ΔT> 0 (4) with respect to the positive temperature difference ΔT ₀ of a predetermined small value (for example, about 0.5 ° C. to 2 ° C.). The control device 22 performs processing so as to keep it and outputs a control signal.

In this way, the supply flow rate q _x almost matches the inflow quantity q _i , so that the power consumption of the pump 16 is prevented from being wasted, and the communication passage 5
Since it prevents the backflow of waste heat, it is possible to reduce the amount of heat that is wasted without recovering it. Moreover, only a temperature detector is required as a detector, and it is easy to use heat source water containing dust and scale. .

Next, the second flow rate control method will be described. This method detects not only the inlet temperature T ₁ and the supply temperature T ₂ but also the return temperature T ₃ , and the supply flow rate q _x at that time is the rotation speed of the pump 16, the opening degree of the flow control valve, and the operation of the pump. It is known from the number of units, the inflow amount q _i is calculated based on these numerical values, and the supply amount q _x is selected corresponding to this.

_{That, q x = q i + q} m (5) q i T 1 + q m T 3 = q x T 2 becomes (6) (5) (6) determined by calculating the inflow _{q i} from equation accordance with this The flow rate is controlled so that the supply flow rate q _x becomes equal.

A case where the flow rate control is performed by controlling the number of pumps will be described. For example, as shown in FIG. 2, consider a case where the number of units is controlled by two pumps, a pump P ₁ (flow rate q ₁ ) and a pump P ₂ (flow rate q ₂ ). Let q ₁ > q ₂ .

First, let us consider a case where only the pump P ₁ is in operation.

Since q _x = q ₁ in the formulas (5) and (6), q ₁ = q _i + q _m (7) q _i T ₁ + q _m T ₃ = q ₁ T ₂ (8). Switching from one P ₁ unit is as follows.

P ₁ + P ₂ 2 units (q ₁ + q ₂ ) ↑ (increase) P ₁ 1 unit (q ₁ ) ↓ (decrease) P ₂ 1 unit (q ₂ ) The boundary conditions for increasing and decreasing the capacity are obtained.

First, the boundary state to be increased is a state in which it is determined that the bypass flow rate q _m is negative, that is, backflow occurs, and the supply flow rate q _x (that is, q ₁ ) is too small with respect to the inflow amount q _i .
_{When m} = 0, that is, T ₂ = T _{1, that} is, ΔT = T ₁ −T ₂ = 0, the capacity must be increased. However, ΔT = T ₁ −T
₂ becomes 0 even when q _m is negative, so for a slight positive temperature difference ΔT ₀ , ΔT = T ₁ −T ₂ = ΔT ₀ should be switched to the capacity increase, that is, P ₁ + P ₂ operation. Boundary condition. ΔT ₀ is about 0.5 to 2 ° C. In order to make it easier to see, ΔT ₀ is described as 1 ° C. below.

Next, in the boundary state where the capacity should be reduced, the inflow amount q _i is q _i =
It becomes q _x , and it is a state in which it is determined that P ₂ can also cover. At this time, the equations (5) and (6) are expressed by q ₁ = q ₂ + q _m (9) q ₂ T ₁ + q _m T ₃ = q ₁ T ₂ (10) (9) (10), and thus q ₂ T ₁ + _{(q 1 -q 2) T 3} = q 1 T 2 than this, The return temperature T ₃ when the inflowing heat source water has a temperature T ₁ and a flow rate q ₂ has an approximate value from the specifications of the heat exchanger 9. Therefore, T ₁ −T ₃ at the boundary state of q ₁ = q ₂ can be calculated in advance. The value T ₁ −T ₃ is used ((1
1 set And

Summarizing the above, the _{P 1 1} units during _operation, T _{1, T} 2, T
₃ is detected and T ₁ −T ₃ and ΔT _A are calculated. If ΔT ₀ is 1 ° C., (a) When 1 ° C.> T ₁ −T ₂ → P ₁ + P ₂ 2 units (b) ΔT _A > T ₁ −T ₂ ≧ 1 ° C. → P ₁ 1 as it is
Performing → _{P 2} 1 units composed as units control when the base _{(c) T 1 -T 2 ≧} ΔT A.

Next, in the case where only the pump P ₂ is in operation, as in the case of only P ₁ , (a) when 1 ° C.> T ₁ −T ₂ → P ₁ operation, P ₂ stop (b) T ₁ -When T ₂ ≧ 1 ° C. → The number of units is controlled so that P ₂ units remain.

Next, let us consider the case of operating _two pumps P ₁ + P ₂ .

Boundary conditions to reduce the capacity and switch to P ₁ unit are:
The inflow quantity q _i is q _i = q _1, and the equations (5) and (6) at that time are q ₁ + q ₂ = q ₁ + q _{m, that} is, q ₂ = q _m (13) q ₁ T ₁ + Q _m T ₃ = (q ₁ + q ₂ ) T ₂ (14) (13) (14) From q ₁ T ₁ + q ₂ T ₂ = (q ₁ + q ₂ ) T ₂ Here, the return temperature T ₃ when the inflowing heat source water has a temperature T ₁ and a flow rate q ₁ can be roughly estimated from the specifications of the heat exchanger 9. Therefore, T ₁ −T ₃ in the boundary state of q _i = q ₁ can be calculated in advance. Using the value T ₁ -T ₃ (15)
formula And Then, (a) when ΔT _c > T ₁ −T ₂ → P ₁ + P _{2 as it is}
2 units (b) When T ₁ -T ₂ > ΔT _c holds → Unit control is performed so that P ₁ 1 unit holds.

The second flow rate control method can predict the optimum supply flow rate q _x or the optimum number of pumps in the state at that time, as compared with the first flow rate control method using only T ₁ and T ₂ .
Stable and smooth control can be performed.

Next, a third flow rate control method will be described.

In this method, in addition to T ₁ , T ₂ , and T ₃ , the outlet temperature T ₄ is also detected, and it is determined whether or not there is a negative bypass flow rate −q _m (= q _B ) that flows backward in the communication passage 5. When q _B is present, the supply flow rate q _x is increased so as to eliminate it.

That is, the outlet temperature T ₄ is detected, and when T ₄ > T ₃ , it is determined that there is a negative bypass flow rate −q _{m, that} is, q _B , and the supply flow rate q _x is increased.

In this case equation (5) is the relationship between the _{q x = q i -q B (} 17) T 1, T 3, T 4, q x T 3 + q B T 1 = q i T 4 (18) ( 18) (19) gives q _i and q _B.

The flow rate control targets T ₁ ≈T ₂ in the state of T ₄ ≈T ₃ .

In the case of continuous control such as pump speed control, as an example, T ₁ -T ₂ is the control target, the target value is α,
α is variable according to the value of T ₄ −T ₃ .

For example, (a) α = 0 ° C. when 1 ° C.> T ₄ −T ₃ or α = 0.5 ° C. (b) α = 1 ° C. when T ₄ −T ₃ ≧ 1 ° C. As another example, (T ₁ -T ₂₎ and _{(T 4} -
Since it is most preferable that each T ₃ ) be 0,
The flow rate may be controlled so that (T ₁ −T ₂ ) + (T ₄ −T ₃ ) = 0 is obtained by summing the detected values of T ₁ , T ₂ , T ₃ , and T ₄ .

When controlling the number of pumps, first, the pumps P ₁ + P ₂
(5) and (6) are expressed as q ₁ + q ₂ = q _i + q _m (19) q _i T ₁ + q _m T ₂ = (q ₁ + q ₂ ) T ₂ (20) from this seek _{q i,} performs as _P 1 + _{P 2 2} units comprising as flow control when _{(a) q 1 ≧ q i} > P 1 operation when _{q 2, P 2} stop _{(b) q} i> q ₁ .

Next, when one pump P ₁ is in operation, equations (5) and (6) are as follows: q ₁ = q _i + q _m (21) q _i T ₁ + q _m T ₃ = q ₁ T ₂ (22) q _i is calculated, (a) P ₁ stops when q ₂ ≧ q _i , P ₂ operation (b) When q _i ≧ q ₁ > q ₂ , P ₁ 1 unit (c) q _i > q ₁ Alternatively, when T ₄ −T ₃ > 0 ° C., the flow rate is controlled so that P ₁ + P ₂ 2 units.

If the pump P _{2 1} units in operation Next, (5) (6) is, q ₂
= Q _i + q _m (23) q _i T ₁ + q _m T ₃ = q ₂ T ₂ (24) From this, q _i is obtained, and (a) when q ₂ ≧ q _i or T ₄ −T ₃ = 0 ° C. At that time, the flow rate control is performed such that P ₂ unit (b) q _i > q ₂ or T ₄ −T ₃ > 0 ° C. P ₁ operation P _{2 is} stopped.

In the third flow rate control method, it is possible to control the presence / absence of the negative bypass flow rate −q _m , and it is possible to reduce the heat that is wasted without being recovered.

Figure 3 is an example in which the number control using the pump P ₁ and P _2, is provided with a manual valve 24 for maintenance pump P ₁ and P _2. A manual valve may be added similarly to the example of FIG.

In FIG. 4, two heat exchangers 9 _a and 9 _b are provided, and a pump P _a (flow rate q _a ) and a pump P _b (flow rate q _b ) are provided respectively.
Is provided. Q _i and q _m are estimated from the pump characteristics q _a and q _b and the temperatures T ₁ , T ₂ and T _3, and the number of units is controlled so as to meet q _i .

FIG. 5 shows an example of the overflow at the outlet, and the outlet pipe 7 branches off from the middle of the return path 14 and rises to the overflow water level.

FIG. 6 is also an example of the overflow at the outlet, and the outlet pipe 7 branches off from the middle of the return path 14, and the tank 25 secures the overflow water level.

FIG. 7 is an example in which the inflow pipe 6 is provided below the water surface of the inlet chamber 3.

FIG. 8 shows an example in which the inlet chamber 3 and the return chamber 6 are divided into different tanks, and the communication passage 5 is formed by a pipe.

FIG. 9 shows an example in which an inlet chamber 3 and a return chamber 4 are vertically provided by a horizontal partition plate 2. You may reverse upside down.

〔The invention's effect〕

The present invention provides an inlet chamber and a return chamber that communicate with each other, allows heat source water to flow into the inlet chamber, returns to the return chamber via a heat exchanger, overflows, and is discharged, and also allows a circulation flow to flow through the communication passage. By making it possible, even if the inflow rate is lower than the lower limit flow rate required by the heat exchanger, water circulation of the lower limit flow rate is secured by the circulation flow in the heat exchanger, increasing adhesion of scale and cleaning material. It is possible to provide a heat recovery device that can prevent troubles such as immobilization, and it is extremely effective in practice.

[Brief description of drawings]

The drawings relate to an embodiment of the present invention and are shown in FIGS.
FIG. 3, FIG. 3 and FIG. 4 are flow charts of different embodiments,
FIGS. 5 and 6 are flow charts of two embodiments of the outlet portion, and FIGS. 7, 8 and 9 are flow charts of three embodiments of the inlet chamber and the outlet chamber. 1 ... Tank body, 2 ... Partition plate, 3 ... Inlet chamber, 4 ... Return chamber, 5 ... Communication passage, 6 ... Inflow pipe, 7 ... Outlet pipe, 8 ...
... Overflow outlet, 9 ... Heat exchanger, 10 ... Heat transfer tube, 11 ... Cleaning material, 12 ... Switching valve, 13 ... Supply path, 14 ... Return path, 15 ... Return tube, 16 ... Pump, 17 ... Buckle plate, 18, 19, 20, 21 ...
Temperature detector, 22 ... Control device, 24 ... Manual valve, 25
……tank.

Claims (6)

[Claims] 1. A heat recovery device having a heat exchanger for recovering heat of heat source water and applying heat to a fluid to be heated, the heat source water inlet chamber having an inlet part of the heat source water, and the heat exchanger passing through the heat exchanger. A heat source water return chamber having a return part for receiving the heat source water, a communication passage communicating between the inlet chamber and the outlet chamber so that the heat source water is moved between the inlet chamber and the outlet chamber; A supply path for guiding the heat source water to the exchanger, a return path for returning the heat source water from the heat exchanger to the return part of the return chamber, and a transfer of the heat source water through the supply path, the heat exchanger and the return path. A heat recovery device comprising: a pump; and an outlet portion that communicates with the return chamber and prevents the water level in the return chamber and the inlet chamber from exceeding a predetermined water level. 2. The heat exchanger is a tubular heat exchanger having a heat transfer tube through which heat source water is passed, the heat exchanger being provided with a cleaning material which is reciprocally driven by the force of the heat source water flow. The heat recovery device according to claim 1, further comprising a switching mechanism for switching the direction of the heat source water flow between normal and reverse directions. 3. A flow rate q _{x of} heat source water passing through the heat exchanger.
The heat recovery device according to claim 2, further comprising a flow rate control device for controlling the heat recovery. 4. The lower limit flow rate q _n required to drive the cleaning material is such that the flow rate q _x controlled by the flow rate control device.
The heat recovery apparatus according to claim 3, further comprising flow rate holding means for maintaining the flow rate q _x at the lower limit flow rate q _n in preference to the control of the flow rate control apparatus when the flow rate becomes smaller. 5. A heat recovery device having a heat exchanger for recovering heat of heat source water and applying heat to a fluid to be heated, the heat source water inlet chamber having an inlet part of the heat source water, and the heat exchanger passing through the heat exchanger. A heat source water return chamber having a return part for receiving the heat source water, a communication passage communicating between the inlet chamber and the outlet chamber so that the heat source water is moved between the inlet chamber and the outlet chamber; A supply path for guiding the heat source water to the exchanger, a return path for returning the heat source water from the heat exchanger to the return part of the return chamber, and a transfer of the heat source water through the supply path, the heat exchanger and the return path. A pump, an outlet communicating with the return chamber to prevent the water level in the return chamber and the inlet chamber from exceeding a predetermined water level, and controlling the flow rate q _{x of the} heat source water passing through the heat exchanger. A flow rate control device, comprising: A source water temperature (hereinafter referred to as inlet temperature) T _1, wherein (hereinafter referred to as supplying this temperature) from the start point near the supply channel heat source water temperature up to the inflow-side heat transfer tube inlet of the heat exchanger and the T ₂ Is detected, and T ₁ -T ₂
The flow rate q by the flow rate control device so as to maintain the temperature difference ΔT of ΔT = ΔT such that ΔT ₀ ≧ ΔT> 0 with respect to the positive temperature difference ΔT ₀ of a predetermined small value.
A heat recovery device characterized in that _x is controlled. 6. A heat recovery device having a heat exchanger for recovering heat of heat source water and applying heat to a fluid to be heated, the heat source water inlet chamber having an inlet part of the heat source water, and the heat exchanger passing through the heat exchanger. A heat source water return chamber having a return part for receiving the heat source water, a communication passage communicating between the inlet chamber and the outlet chamber so that the heat source water is moved between the inlet chamber and the outlet chamber; A supply path for guiding the heat source water to the exchanger, a return path for returning the heat source water from the heat exchanger to the return part of the return chamber, and a transfer of the heat source water through the supply path, the heat exchanger and the return path. A pump, an outlet communicating with the return chamber to prevent the water level in the return chamber and the inlet chamber from exceeding a predetermined water level, and controlling the flow rate q _{x of the} heat source water passing through the heat exchanger. A flow rate control device, and an inlet temperature T ₁ and a supply temperature T ₂ and the temperature of the heat source water between the outlet of the heat transfer tube on the outflow side of the heat exchanger and the vicinity of the return portion of the outlet of the return path (hereinafter referred to as the return temperature) T ₃
If, (hereinafter referred to as this outlet temperature) heat source water temperature in the vicinity of the outlet portion of the _{T 4,} T _1, T 2, _{T 3} or detects the total of these temperatures _{T 1,} T 2, _{T 3} Or T ₁ , T
_{2. The} heat recovery device, wherein the flow rate control device controls the flow rate q _x so that it becomes substantially equal to the inlet flow rate q _{i of the} heat source water calculated based on ₂ , T ₃ , and T ₄ .