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CN116576495A - Heat supply unit capable of reducing backwater temperature and backwater temperature reducing method - Google Patents

️Fri Aug 11 2023

Disclosure of Invention

The invention aims to provide a heat supply unit for reducing the backwater temperature and a backwater temperature reducing method, which have the functions of not increasing the area of a radiator, not needing an absorption heat pump, not using an electric heat pump, not reducing the flow of a secondary network heat user and not needing cascade heat exchange to obtain low backwater temperature.

In order to achieve the above object, the present invention provides the following solutions:

the invention provides a heat supply unit for reducing backwater temperature, which comprises: the system comprises a unit controller, a room temperature sensor, a heat exchanger, an electric regulating valve and an electric on-off valve which are arranged at a primary network of the heat exchanger, a secondary network water supply temperature transmitter, a secondary network backwater temperature transmitter and a secondary network circulating pump which are arranged at a secondary network of the heat exchanger;

the room temperature sensor is used for collecting the actual value of the room temperature of the user side;

a secondary network water supply temperature regulator is arranged in the unit controller; the unit controller is respectively connected with the room temperature sensor, the electric regulating valve, the electric on-off valve, the secondary network water supply temperature transmitter, the secondary network backwater temperature transmitter and the secondary network circulating pump;

the unit controller is used for:

acquiring unit operation data;

when the operation data show that the secondary network circulating pump operates under the working condition of 100% of design flow and the electric on-off valve is under the working condition, setting parameters of a secondary network water supply temperature regulator, and controlling valve position action of the electric regulating valve according to the parameters of the secondary network water supply temperature regulator, so that the deviation between the actual secondary network water supply temperature value and the target secondary network water supply temperature value is within a set range;

according to the operation data and the on-off mode of the electric on-off valve, the two-network backwater temperature is regulated and controlled, and then the one-network backwater temperature is regulated and controlled.

Optionally, the parameters of the secondary network water supply temperature regulator comprise a regulation period, a valve opening increment and a regulation water supply temperature dead zone.

Optionally, the unit controller is further configured to:

setting an upper limit target value and a lower limit target value of the backwater temperature of the secondary network;

an upper limit target value and a lower limit target value of the room temperature are set.

Optionally, the operation data at least comprises a room temperature actual value and a secondary network backwater temperature actual value, and the unit controller is used for controlling the secondary network backwater temperature according to the operation data and the on-off mode of the electric on-off valve:

when the actual value of the room temperature is higher than the upper limit target value of the room temperature,

if the actual value of the secondary network backwater temperature is higher than the upper limit target value of the secondary network backwater temperature, regulating and controlling the secondary network backwater temperature in a mode that an electric on-off valve is broken and a secondary network circulating pump keeps running until the actual value of the secondary network backwater temperature is lower than the lower limit target value of the secondary network backwater temperature;

and if the actual value of the secondary network backwater temperature is lower than the lower limit target value of the secondary network backwater temperature, regulating and controlling the secondary network backwater temperature by adopting a mode that an electric on-off valve is communicated and a secondary network circulating pump keeps running until the actual value of the secondary network backwater temperature is higher than the upper limit target value of the secondary network backwater temperature.

when the actual value of the room temperature is lower than the upper limit target value of the room temperature, changing the lower limit target value of the backwater temperature of the secondary network;

and if the actual value of the secondary network backwater temperature is lower than the lower limit target value of the changed secondary network backwater temperature, regulating and controlling the secondary network backwater temperature by adopting a mode that an electric on-off valve is communicated and a secondary network circulating pump keeps running until the actual value of the secondary network backwater temperature is higher than the upper limit target value of the secondary network backwater temperature.

Optionally, when the actual value of the room temperature is lower than the upper limit target value of the room temperature, the unit controller is used for changing the lower limit target value of the secondary network backwater temperature:

when the actual value of the room temperature is lower than the lower limit target value of the room temperature, determining the lower limit target value of the changed secondary network backwater temperature as thnj-deltath; thnj is a set lower limit target value of the backwater temperature of the secondary network, and Deltath is a difference value of backwater temperature;

when the actual value of the room temperature is higher than the lower limit target value of the room temperature and lower than the lower limit target value of the room temperature, determining the lower limit target value of the changed secondary network backwater temperature as thxj-2 xDeltath; and thxj is the set upper limit target value of the backwater temperature of the secondary network.

Optionally, a primary network water supply pipe and a primary network water return pipe which are connected with the heat exchanger are also arranged at the primary network of the heat exchanger; wherein, once net water supply temperature transmitter, electric control valve and electronic on-off valve set up in once net delivery pipe, once net return water temperature transmitter sets up at once net return water pipe.

Optionally, a secondary network water supply pipe and a secondary network water return pipe which are connected with the heat exchanger are also arranged at the secondary network of the heat exchanger; the secondary network water supply temperature transmitter is arranged on the secondary network water supply pipe; the secondary network circulating pump, the secondary network backwater temperature transmitter and the secondary network backwater pressure transmitter are arranged on the secondary network backwater pipe.

Optionally, the system also comprises an upper computer; the upper computer is used for acquiring operation data acquired by the unit controller and various instructions transmitted by the unit controller.

The invention also provides a backwater temperature reducing method applied to the backwater temperature reducing heat supply unit, which comprises the following steps:

acquiring unit operation data;

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

(1) The invention is simple, effective and low in cost; the invention can be used for improving the structure of the existing heat supply unit according to the invention and installing a unit controller according to the invention, thus obtaining the required low backwater temperature.

(2) According to the method provided by the invention, the return water temperature of the secondary network is reduced, and the return water temperature of the primary network is also reduced, and the primary network temperature difference is increased, so that the heating area can be increased under the condition that the primary network flow is unchanged.

(3) The total flow of the primary network is fluctuated, because the number of the primary network electric on-off valves of all the heating units is changed, the hydraulic balance among the heating units in the on state of the electric on-off valves can be always ensured due to the adjusting effect of the primary network electric adjusting valve.

(4) Although the water supply temperature of the secondary network fluctuates, the flow of the secondary network is stable, so that hydraulic imbalance of the secondary network does not occur.

(5) The room temperature data is directly collected, and a room temperature feedback control scheme is adopted; room temperature fluctuates somewhat, but because the thermal inertia of the building is very large, a few room temperature fluctuations do not affect thermal user comfort.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The invention provides a heat supply unit for reducing the return water temperature and a method for reducing the return water temperature, which have the characteristics of improving the primary network conveying capacity, improving the system efficiency and reducing the heat supply cost, and have the characteristics of low cost, simplicity and easiness.

In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.

Example 1

The embodiment of the invention provides a heat supply unit capable of reducing the return water temperature, which can realize the low return water temperature operation of the heat supply unit in a low-cost mode, effectively improve the transmission efficiency of a primary network and improve the operation efficiency of a heat source.

The heat supply unit for reducing the return water temperature is provided with a heat supply unit controller (hereinafter referred to as a unit controller) according to the system characteristics of the heat supply unit, and the unit controller controls the heat supply unit to operate in a mode of reducing the return water temperature.

As shown in fig. 1, a heating unit for reducing return water temperature provided by an embodiment of the present invention includes: the system comprises a unit controller, a room temperature sensor, a heat exchanger, an electric regulating valve and an electric on-off valve which are arranged at a primary network of the heat exchanger, a secondary network water supply temperature transmitter, a secondary network backwater temperature transmitter and a secondary network circulating pump which are arranged at a secondary network of the heat exchanger;

the room temperature sensor is used for collecting the actual value of the room temperature of the user side; a secondary network water supply temperature regulator is arranged in the unit controller; the unit controller is respectively connected with the room temperature sensor, the electric regulating valve, the electric on-off valve, the secondary network water supply temperature transmitter, the secondary network backwater temperature transmitter and the secondary network circulating pump.

The unit controller is used for:

and acquiring unit operation data.

When the operation data show that the secondary network circulating pump operates under the working condition of 100% of design flow and the electric on-off valve is under the working condition, setting parameters of a secondary network water supply temperature regulator, and controlling valve position action of the electric regulating valve according to the parameters of the secondary network water supply temperature regulator, so that the deviation between the actual secondary network water supply temperature value and the target secondary network water supply temperature value is within a set range; the parameters of the secondary network water supply temperature regulator comprise a regulation and control period, a valve opening increment and a regulation and control water supply temperature dead zone.

According to the operation data and the on-off mode of the electric on-off valve, the two-network backwater temperature is regulated and controlled, and then the one-network backwater temperature is regulated and controlled.

Preferably, the unit controller in the embodiment of the present invention is further configured to:

setting an upper limit target value and a lower limit target value of the backwater temperature of the secondary network, and setting an upper limit target value and a lower limit target value of the room temperature.

Further, the operation data at least comprises a room temperature actual value and a secondary network backwater temperature actual value, and the unit controller is used for controlling the secondary network backwater temperature according to the operation data and the on-off mode of the electric on-off valve:

when the actual value of the room temperature is higher than the upper limit target value of the room temperature,

Or,

When the actual value of the room temperature is lower than the upper limit target value of the room temperature, the lower limit target value of the backwater temperature of the secondary network is changed, and the unit controller is used for:

In addition, in the example of the invention, a primary network water supply pipe and a primary network water return pipe which are connected with the heat exchanger are also arranged at the primary network of the heat exchanger; wherein, once net water supply temperature transmitter, electric control valve and electronic on-off valve set up in once net delivery pipe, once net return water temperature transmitter sets up at once net return water pipe.

A secondary network water supply pipe and a secondary network water return pipe which are connected with the heat exchanger are also arranged at the secondary network of the heat exchanger; the secondary network water supply temperature transmitter is arranged on the secondary network water supply pipe; the secondary network circulating pump, the secondary network backwater temperature transmitter and the secondary network backwater pressure transmitter are arranged on the secondary network backwater pipe.

Preferably, the embodiment of the invention further comprises an upper computer; the upper computer is used for acquiring operation data acquired by the unit controller and various instructions transmitted by the unit controller.

Example two

As shown in fig. 2, a method for reducing return water temperature of a heat supply unit for reducing return water temperature according to an embodiment of the present invention includes:

step 100: and acquiring unit operation data.

Step 200: when the operation data show that the secondary network circulating pump operates under the working condition of 100% of design flow and the electric on-off valve is under the working condition, setting parameters of the secondary network water supply temperature regulator, and controlling valve position action of the electric regulating valve according to the parameters of the secondary network water supply temperature regulator, so that deviation between the actual secondary network water supply temperature value and the target secondary network water supply temperature value is within a set range.

Step 300: according to the operation data and the on-off mode of the electric on-off valve, the two-network backwater temperature is regulated and controlled, and then the one-network backwater temperature is regulated and controlled.

The method for reducing the return water temperature provided by the embodiment of the invention can be used for a concentrated heat source indirect heat supply unit, a concentrated heat source distributed pump indirect heat supply unit, a concentrated heat source mixed water direct heat supply unit, a gas boiler indirect heat supply unit and the like. Each heating unit is provided with a unit controller and corresponding hydraulic conveying equipment and meters. The method for reducing the backwater temperature according to the embodiment of the invention is described by taking a concentrated heat source indirect heat supply unit with the backwater temperature reduction as an example.

The structure of the indirect heat supply unit with the concentrated heat source for reducing the backwater temperature is shown in fig. 3, and a primary network water supply pressure transmitter 11, a primary network water supply temperature transmitter 12, an electric regulating valve 17 and an electric on-off valve 18 are sequentially connected to a primary network water supply pipe 12; a primary net backwater pressure transmitter 14 and a primary net backwater temperature transmitter 16 are connected to the primary net backwater pipe 15; a secondary net water supply temperature transmitter 25 and a secondary net water supply pressure transmitter 27 are sequentially installed on the secondary net water supply pipe 23; the secondary network water return pipe 24 is sequentially provided with a secondary network circulating pump 21, a heat meter 22, a secondary network water return temperature transmitter 26 and a secondary network water return pressure transmitter 28, and the secondary network water supply pipe 23 and the secondary network water return pipe 24 are connected with a heat user building 29; connected between the primary and secondary networks is a heat exchanger 19.

The touch screen on the unit controller 4 is respectively connected with the touch screen 1 and the gateway 2 through the gateway interface 3; the first analog input interface 8 is respectively connected with the primary network water supply pressure transmitter 11, the primary network water supply temperature transmitter 12, the primary network backwater pressure transmitter 14 and the primary network backwater temperature transmitter 16; the second analog input interface 5 is respectively connected with a secondary network water supply temperature transmitter 25, a secondary network water supply pressure transmitter 27, a secondary network backwater temperature transmitter 26 and a secondary network backwater pressure transmitter 28; the analog output interface 9 is connected with a secondary network circulating pump frequency converter 20, an electric regulating valve 17 and an electric on-off valve 18; the RS485 interface 10 is connected with the calorimeter 22; the room temperature and external temperature interface 30 is respectively connected with the room temperature sensor 6 and the external temperature sensor 7. The secondary network circulation pump inverter 20 is also connected to a secondary network circulation pump 21.

The upper computer 31 in the dispatching room is used for acquiring the operation data acquired by the unit controller and performing remote monitoring.

The main function of the unit controller 4 is to collect operation data, communicate with the upper computer 31, control valve position actions of the electric regulating valve 17 and the electric on-off valve 18, and the unit controller 4 is internally provided with a secondary network water supply temperature regulator, so that the actual secondary network water supply temperature value can be regulated and controlled according to a given secondary network water supply temperature target value, and when the electric on-off valve 18 is in a communicating state, the actual secondary network water supply temperature value is ensured to be equal to the secondary network water supply temperature target value, and the hydraulic balance of the primary network is realized.

A method for reducing backwater temperature applied to the heat supply unit comprises the following steps:

(1) And after the heat supply unit normally operates, the unit controller collects real-time operation data of the heat supply unit.

After the heat supply unit normally operates, real-time operation data collected by the unit controller comprise primary network pressure, secondary network pressure, primary network water supply temperature, secondary network water supply temperature, primary network water return temperature, secondary network water return temperature, accumulated heat, accumulated flow, instantaneous heat, instantaneous flow, secondary network circulating pump frequency, valve opening of an electric regulating valve, valve state of an electric on-off valve, indoor temperature, outdoor temperature and the like.

(2) According to real-time operation data, reduce above-mentioned heating unit's a net return water temperature, specifically include:

s1: and setting parameters of a secondary network water supply temperature regulator in the unit controller.

When the secondary network circulating pump is in the working condition of 100% of design flow and the state of the electric on-off valve 18 is in the on state, the secondary network water supply temperature regulator controls the valve position action of the electric regulating valve 17, so that the parameters of the secondary network water supply temperature regulator under the working condition that the actual secondary network water supply temperature tgs of the heat exchanger is consistent with the target secondary network water supply temperature tgj are as follows: the control period Ti (range 0-300 s, preferably 60 s), the valve opening increment DeltaF (1% -5%, preferably 2%), and the control water supply temperature dead zone DeltaT (range + -3 ℃, preferably + -1 ℃).

The value range of the ground heating secondary network water supply temperature target value tgdj is 50-60 ℃, and the optimal value is 55 ℃; the value range of the water supply temperature target value tggj of the secondary network for hanging and heating is 60-70 ℃, and the optimal value is 65 ℃.

When the state of the electric on-off valve 18 is in the off state, the secondary network water supply temperature regulator does not operate, and the valve position of the electric control valve 17 does not change.

S2: setting an upper limit target value thxj and a lower limit target value thnj of the backwater temperature of the secondary network; wherein, the upper limit target value thdxj of the return water temperature of the floor heating secondary network has a value range of 25-35 ℃, the lower limit target value thdnj has a value range of 20-30 ℃, and the preferred value is that thdxj=30 ℃, and thdnj=25 ℃; the upper limit target value thgxj of the water return temperature of the secondary network for hanging and heating is in the range of 30-40 ℃, the lower limit target value thgnj is in the range of 20-30 ℃, and the preferred value is that thgxj=35 ℃, and thgnj=25 ℃.

S3: setting a target room temperature; wherein the upper limit target value tnxj of the room temperature is 18-24 ℃, and preferably the upper limit target value is 20 ℃; the lower limit target value tnnj of the room temperature is in the range of 18 to 22 ℃, preferably 18 ℃.

S4: the electric on-off valve 18 regulates the backwater temperature of the secondary network in an on-off mode.

If the actual value ths of the secondary network backwater temperature is higher than the upper limit target value thxj of the secondary network backwater temperature, the state of the electric on-off valve 18 is controlled to be disconnected, and the condition that the actual value ths of the secondary network backwater temperature is lower than the lower limit target value thnj of the secondary network backwater temperature is waited.

If the actual value ths of the secondary network backwater temperature is lower than the lower limit target value thn of the secondary network backwater temperature, the state of the electric on-off valve 18 is controlled to be in an on state, and the state is waited for that the actual value ths of the secondary network backwater temperature is higher than the upper limit target value thxj of the secondary network backwater temperature.

S5: if the room temperature actual value tns is lower than the room temperature lower limit target value tnnj, the lower limit target value thnj of the secondary network backwater temperature is reduced (thgnj is floor heating, thgnj is hanging heating), wherein thdnj=thdxj- Δth (floor heating), and thgnj=thgxj- Δth (hanging heating). The value of the difference Deltath of the return water temperature is 2-5 ℃, preferably 3 ℃.

If the actual value tns of the room temperature is higher than the upper limit target value tnxj of the room temperature, the lower limit target value thnj of the secondary network backwater temperature is kept unchanged.

If the real value tns of the room temperature is higher than the lower limit target value tnnj of the room temperature and lower than the upper limit target value tnxj of the room temperature, the lower limit target value thnj=thxj-2×Δth of the secondary network backwater temperature.

Examples: the indirect heat supply system of a certain concentrated heat source comprises 60 indirect heat supply units, the heat supply area is 300 kilo-square meters, and the tail end radiator is hung. In order to ensure the primary net conveying efficiency, the primary net backwater temperature needs to be reduced and the primary net backwater temperature is lower than 40 ℃, the difference between the secondary net water supply temperature and the secondary net backwater temperature of the indirect heat supply units is between 5 and 8 ℃, and the room temperature is required to be between 18 and 20 ℃. According to the requirements, all indirect heating units in the heating system are transformed into indirect heating units with the function of reducing the backwater temperature, corresponding unit control cabinets are configured, and meanwhile, the low backwater temperature operation is realized according to the following method.

1. And obtaining the water supply temperature of the secondary network of each heat exchanger under the primary network balance working condition.

Firstly, enabling the secondary network circulating pump to operate under the working condition of 100% of design flow, and setting parameters of a secondary network water supply temperature regulator under the working condition of an electric on-off valve: the regulation period ti=60 s, the valve opening increment Δf=2%, and the regulation water supply temperature dead zone Δt= ±1 ℃;

and then setting the target water supply temperature values of the secondary network of all the hanging heat exchangers according to the target water supply temperature value tgj =65 ℃ of the hanging secondary network, wherein the actual water supply temperature value tgs of the secondary network of the hanging heat exchanger is automatically regulated and controlled by the secondary network water supply temperature regulator of the unit controller to be consistent with the target water supply temperature value of the secondary network thereof, so that the hydraulic balance among the heat exchangers in the on-off valve on-state of the primary network is realized.

2. Setting upper and lower limit target values of the backwater temperature of the secondary network: the upper limit target value thgxj=38 ℃ and the lower limit target value thgnj=25 ℃ of the water return temperature of the secondary network for hanging heating; the difference Δth=3℃.

3. The upper limit target value tnxj of room temperature was set to 20 ℃ and the lower limit target value tnnj of room temperature was set to 18 ℃.

4. The electric on-off valve 18 regulates and controls the backwater temperature in an on-off mode

(1) If the actual value tns of the room temperature is higher than the upper limit target value tnxj=20 ℃ of the room temperature, the lower limit target value thgnj=25 ℃ of the secondary network backwater temperature is maintained:

if the actual value ths of the secondary network backwater temperature is higher than the upper limit target value thgxj=38 ℃ of the secondary network backwater temperature, the electric on-off valve is disconnected, the secondary network circulating pump operates normally, and then the actual value ths of the secondary network backwater temperature is waited to be lower than the lower limit target value thgnj=25 ℃ of the secondary network backwater temperature.

If the actual value ths of the secondary network backwater temperature is lower than the lower limit target value thgnj=25 ℃ of the secondary network backwater temperature, the electric on-off valve is turned on, and then the actual value ths of the secondary network backwater temperature is higher than the upper limit target value 38 ℃ of the secondary network backwater temperature.

(2) If the room temperature actual value tns is lower than the room temperature lower limit target value tnnj=18℃: the lower limit target value of the backwater temperature of the secondary network is changed, thgnj=38 ℃ -3 ℃ =35 ℃, and the range of the deltath value is 3 ℃.

If the actual value ths of the secondary network backwater temperature is higher than the upper limit target value thgxj=38 ℃ of the secondary network backwater temperature, the electric on-off valve is disconnected, and then the actual value ths of the secondary network backwater temperature is lower than the lower limit target value thgnj=35 ℃ of the modified secondary network backwater temperature.

If the actual value ths of the secondary network backwater temperature is lower than the lower limit target value thgnj=35 ℃ of the modified secondary network backwater temperature, the electric on-off valve (18) is opened, and then the actual value ths of the secondary network backwater temperature is higher than the upper limit target value thgxj=38 ℃ of the secondary network backwater temperature.

(3) If the actual value tns of the room temperature is higher than the target value tnnj=18 ℃ of the lower limit of the room temperature and lower than the target value tnxj=20 ℃, the target value thgnj=38 ℃ -3 ℃ of the lower limit of the return water temperature is changed, wherein the range of the value deltath is 3 ℃. The subsequent steps are the same as the step (2).

The further explanation is as follows:

(1) Process for increasing actual value of room temperature of hot user

When the actual value tns of the room temperature is lower than the target value tnnj=18 ℃ of the lower limit of the room temperature and the actual value ths of the return water temperature of the secondary network is lower than the target value thgnj=35 ℃ of the lower limit of the return water temperature of the secondary network, the electric on-off valve is turned on, the secondary network circulating pump is operated, and hot water with the water supply temperature of tgj =65 ℃ of the secondary network is sent to a user side; then after a period of time, the actual value of the backwater temperature of the secondary network starts to rise, and when the actual value exceeds the upper limit target value thgxj=38 ℃ of the backwater temperature of the secondary network, the electric on-off valve is disconnected; and then the water supply temperature of the secondary network and the water return temperature of the secondary network tend to be consistent, circulation is continued in the secondary network, the actual water return temperature of the secondary network is continuously reduced, and when the water return temperature is lower than the target value thgnj=35 ℃ of the lower limit of the water return temperature of the secondary network, the process is continued until the actual value of the room temperature is higher than the upper limit of the room temperature by 20 ℃.

(2) Process for reducing actual value of room temperature of hot user

When the actual value tns of the room temperature is higher than the upper limit target value tnxj=20 ℃ of the room temperature and the actual value ths of the secondary network backwater temperature is lower than the lower limit target value thgnj=25 ℃ of the secondary network backwater temperature, the electric on-off valve is turned on, the secondary network circulating pump is operated, and the secondary network water supply temperature is tgj =65 ℃ and hot water is sent to a user side; then after a period of time, the actual value of the backwater temperature of the secondary network starts to rise, and when the actual value exceeds the upper limit target value thgxj=38 ℃ of the backwater temperature of the secondary network, the electric on-off valve is disconnected; and then the water supply temperature of the secondary network and the water return temperature of the secondary network tend to be consistent, circulation is continued in the secondary network, the actual water return temperature of the secondary network is continuously reduced, and when the water return temperature is lower than the lower limit target value thgnj=35 ℃ of the water return temperature of the secondary network, the process is continued until the actual value of the room temperature is lower than the lower limit target value 18 ℃.

(3) It can be seen that the fluctuation range of the secondary network backwater temperature is 35-38 ℃ in the room temperature heating process of the hot user, and the average backwater temperature is 36.5 ℃; in the process of reducing the room temperature of a heat user, the fluctuation range of the secondary network backwater temperature is 25-38 ℃, the average backwater temperature is 33 ℃, that is, when the actual value of the room temperature is lower than 18 ℃, a room temperature heating process is started; when the actual value of the room temperature is higher than 20 ℃, a room temperature cooling process is started. The room temperature thus fluctuates between 18 and 20 ℃.

(4) In order to avoid the excessively rapid fluctuation of the room temperature, an intermediate process is added, wherein the actual value tns of the room temperature is larger than 18 ℃ and smaller than 20 ℃, and the fluctuation range of the secondary network backwater temperature in the intermediate process is 32-38 ℃ and the average backwater temperature is 35 ℃.

In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.

The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.