JPS61122457A - Solar heat collecting device - Google Patents

Abstract

PURPOSE:To prevent the thermal medium from boiling in a heat collector by detecting the temperature and pressure of the thermal medium in the heat collector, and controlling the rate of circulation of the thermal medium so that the relationship between the two may not fall in the boiling condition. CONSTITUTION:A pressure sensor 10 and a temperature sensor 6 are disposed on the heat collector 1 side to detect the pressure and temperature. A controller 11 compares the temperature and pressure of the thermal medium detected by both the sensors 6, 10 at the outlet of the heat collector 1 with the value as shown by a broken line on the diagram, and if the condition of the broken line B is met, the delivery rate of a pump 5 is increased by a certain amount to increase the pressure loss PL so that the relationship between the temperature and pressure may not reach the boiling condition. In addition, the controller 11 starts and stops the pump 5 in response to a temperature difference as detected by temperature sensors 6, 7, and if the boiling condition is not reached while the pump 5 is being operated, its delivery rate is reduced to save the power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a solar heat collector that can prevent boiling of a heat medium within a heat collector.

<Prior Art> FIG. 4 shows a solar heat collector that has been commonly used in the past.

1 is a solar heat collector, 2 is a heat storage tank, 2a is a heat exchanger for indirectly transmitting the heat of the heat medium to the heat storage body in the heat storage WI2,
3 is the outgoing pipe of the heat medium circulation circuit, 4 is the return pipe of the same circulation circuit, 5
is a heat medium circulation pump, 6° is a heat collector temperature sensor that detects the heat medium outlet temperature of the solar heat collector 1, 7 is a heat storage tank temperature sensor that detects the temperature at the bottom of the heat storage tank, 8 is a heat medium supply tank, 9 is a control section. Note that the arrows in the figure indicate the circulation direction of the heat medium, and the broken lines indicate electrical connections.

In the above configuration, the heat medium stored in the heat medium supply tank 8 whose upper part is open to the atmosphere is operated by the control unit 9 according to the temperature detected by the heat collector temperature sensor 6 and the heat storage tank temperature sensor 7. The heat medium circulation pump 5 controls the heat medium supply tank 8, the circulation pump 5, the outgoing pipe 3, the heat collector 1, the return pipe 4, the heat exchanger 2a, and the heat medium supply tank 8 for forced circulation. The heat collector 1 collects the solar heat, and the heat exchanger 2a exchanges the solar heat with the heat storage body in the heat storage tank 2 to store the heat.

The operation of the circulation pump 5 is controlled as follows depending on the difference in temperature detected by the temperature sensor 6.7. That is, when the temperature sensor 6 becomes higher than the temperature sensor 7 by, for example, 7°C or more, the circulation pump 5 is operated, and the temperature difference becomes, for example, 4°C or more.
It will stop when the temperature drops below ℃.

Here, the circulation circuit is configured by 8 heat medium supply tanks.
is open to the atmosphere, but other parts are sealed, so once the circulation circuit is full of water, even if the circulation pump 5 is stopped, the heat medium in the circulation circuit, including the heat collector 1, remains in the siphon. It will not fall due to this phenomenon. Therefore, once the circulation circuit is filled with water, the lift of the circulation pump 5 only needs to be equal to the pressure loss for the flow rate of the circulation circuit, and the flow rate can be controlled using a variable output pump such as an inverter pump. This allows for economical operation with minimal power consumption.

<Problems to be Solved by the Invention> As mentioned above, the heating medium does not fall due to the siphon phenomenon, but the circulation circuit above the heating medium liquid level in the heating medium supply tank 8 only absorbs the water head equal to the height difference. becomes lower than atmospheric pressure.

For this reason, the boiling point is lowered by that amount, and the heat medium can be boiled at a lower temperature than at atmospheric pressure. Once it boils, the pressure loss increases rapidly, and the circulation pump 5 stops shortly after boiling. , the heat collecting effect becomes impossible. This is because all the collected thermal energy is consumed for boiling, the temperature of the heat medium does not rise, and the temperature difference between the temperature sensors 6 and 7 falls below the reference value for stopping the operation of the circulation pump 5. If this happens, it will be difficult to recover the temperature difference above the standard value for restarting operation. Therefore, even if there is sufficient solar radiation and the heat storage capacity of the heat storage tank 2 is sufficient, heat cannot be collected.

The present invention has been made for the purpose of solving the problems of the prior art and providing a solar heat collecting device that can prevent the heat medium from boiling.

Means for Solving the Problems〉 In order to achieve the above-mentioned object, the present invention provides a heat medium circulation pump with a variable discharge and a heat medium circulation pump, and a heat collector temperature sensor that detects the temperature of the heat medium at the outlet of the heat collector. In addition to the sensor, there is also a collector pressure sensor that detects the pressure inside the collector, and the detection output of each of these sensors is compared with pre-stored boiling conditions for the heating medium, and if the heating medium approaches boiling conditions, the heating medium is The present invention is characterized by comprising a control section that increases the discharge amount of the circulation pump.

<For home use> In the device of the present invention, the temperature and pressure of the heat medium in the heat collector are detected by the heat collector temperature sensor and the heat collector pressure sensor, and when the heat medium circulation pump approaches boiling conditions, the heat medium circulation pump is activated. By increasing the discharge volume and increasing the pressure loss in the circulation circuit to increase the pressure inside the collector, boiling conditions are avoided and excessive temperature rise in the collector is also prevented, allowing normal operation. control is carried out.

<Example> Next, the present invention will be specifically described with reference to an illustrated example. Note that the same parts as in the conventional example shown in FIG.

In FIG. 1, 10 is a heat collector pressure sensor for detecting the pressure inside the heat collector 1, and 11 is a control section. It is desirable that the pressure sensor 10 can detect the pressure at the lowest pressure part in the circulation circuit, and in this example, it is provided at the outlet of the heat collector 1, that is, at the starting end of the return pipe 4. Also, the control section 11
For example, a microcomputer is used to store the boiling conditions of the heating medium and the overall control program,
and a central processing unit.

As the boiling condition of the heating medium, the relationship between the saturation pressure and temperature of the heating medium used as illustrated in FIG. 2 is used,
This should be memorized in the form of numerical tables or calculation formulas. For example, if the heat medium is water, the solid line A in FIG. 2 is a water vapor pressure-temperature diagram. The area above solid line A in Figure 2 is the boiling region,
As a reference value for control, data that is slightly closer to the non-boiling region side than the solid line A, such as the broken line B in the figure, is used, taking into account a certain safety factor.

The pressure Pc (kg/am") inside the heat collector 1 is expressed by the following formula (1)
So/required.

Pc=Pa-h ・r+PL --Formula (1) where, Pa: Atmospheric pressure (kg/cm2) 11: Height from the liquid level of the heat medium supply tank 8 to the highest part of the heat collector 1 (cm) r : Specific weight of the heat medium (kg/cm) PL: Pressure loss in the circulation circuit from the outlet of the heat collector 1 to the heat medium supply tank 8 (kg/am") Now, if the heat medium is water, Pa 1.033kg/cm
”, h is 500cm, PL at a certain flow rate is 0.16
7kg/cIll”, the pressure inside the collector is Pc-4,033-800X0,001+0.167=
0.40 (kg/am”).According to the well-known steam saturation stage, the pressure
The boiling point of water at a force of 0.4 kg/cm" is 75.42°C, and if the temperature of the heat medium at the outlet of the collector at this time is below 75.42°C, heat collection can continue without any abnormality. If the temperature exceeds the temperature, a boiling state occurs and normal heat collection cannot be expected, and in order to avoid boiling, it is necessary to increase Pc, that is, the pressure inside the heat collector 1.

Since Pa, h, and r in equation (1) are constant once the system is determined, in order to increase Pc, PL, that is, the heat collector 1
It is sufficient to increase the pressure loss in the subsequent circulation circuit, and this pressure loss PL changes depending on the above h specific to the system, the length and piping diameter of the circulation circuit, the flow rate of the heat medium, etc. It can be seen that it is sufficient to control the flow rate of .

That is, the control 8S11 compares the relationship between the temperature and pressure of the heat medium at the outlet of the heat collector 1 detected by the temperature sensor 6 and the pressure sensor 10 with the value of the broken line B in FIG. If so, the discharge amount of the circulation pump 5 is increased by a certain amount of change, and the pressure loss PL is increased to prevent the relationship between temperature and pressure from reaching the boiling condition.

Further, the control unit 11 operates and stops the circulation pump 5 according to the temperature difference detected by the temperature sensor 6.7, and when the circulation pump 5 is in operation, the relationship between temperature and pressure reaches the condition indicated by the broken line B. If not, control is performed to reduce the discharge amount little by little to eliminate wasted power consumption and to prevent the discharge amount from falling below a preset minimum discharge amount.

A flowchart regarding the above control is shown in FIG. Here, the meaning of each symbol is as follows.

TH: Detection temperature of JJ heating device temperature sensor 6 ('C) TL
: Detection temperature of heat storage tank temperature sensor 7 ("C) F : Discharge amount of heat medium circulation pump 5 (1/Il+in) Fmin:
Maximum discharge amount (1/min) ΔF: Discharge amount variation (l/n+in) <Effects of the invention> As is clear from the description of the above embodiments, the present invention The system detects the temperature and pressure of the heat exchanger and controls the circulation flow rate of the heat medium so that the relationship between the two does not reach boiling conditions, thereby preventing the heat medium from boiling inside the heat collector. Ru.

Therefore, it is possible to obtain a solar heat collecting device capable of stable heat collecting without being unable to collect heat even though there is sunlight and there is sufficient heat storage capacity in the heat storage tank.

[Brief explanation of the drawing]

FIG. 1 is a schematic structural diagram of an embodiment of the present invention, and FIG. 2 is a
A pressure-temperature diagram, FIG. 3 is a control 70-chart diagram, and FIG. 4 is a schematic structural diagram of a conventional example. 1... Solar heat collector, 2... Heat storage tank 5...
・Heat medium circulation pump, 6... Heat collector temperature sensor,

Claims (1)

[Claims] In a solar heat collection device that stores solar heat by forcing a heat medium to circulate between a solar heat collector and a heat storage tank, a heat medium circulation pump with a variable discharge rate and a temperature of the heat medium at the outlet of the heat collector are used. A heat collector temperature sensor detects the pressure inside the heat collector, a heat collector pressure sensor detects the pressure inside the heat collector, and the detection outputs of these sensors are compared with pre-stored boiling conditions for the heat medium, and the temperature is determined to be close to boiling conditions. 1. A solar heat collector comprising: a control unit that increases the discharge amount of a heat medium circulation pump when the heat medium circulation pump is heated.