A method for online control of solution concentration in a heat source tower

Abstract

The invention relates to an online control method for solution concentration of a heat source tower, and belongs to the field of energy technology. The method specifically comprises: setting an approach temperature △t of a heat source tower, obtaining an outdoor wet-bulb temperature T1, then measuring a solution temperature T2 of an inlet of the heat source tower and a solution density ρ at a heat source tower inlet main pipe, establishing a variation model of the solution temperature T2 of an inlet of the heat source tower and the solution density ρ at a heat source tower inlet main pipe, calculating a freezing point temperature T3 of a solution at an outlet of the heat source tower through the solution temperature of the inlet of the heat source tower, controlling the start and stop of a liquid replenishment electric valve, and online controlling the solution concentration of the heat source tower when the heat source tower is operating normally.

Description

Technical Field

[0001] The invention belongs to the field of energy technology, and in particular relates to an online control method for solution concentration in a heat source tower. Background Art

[0002] The heat source tower heat pump energy supply system can be used both in winter and summer. It can be used in newly built buildings without other cold and heat sources; it can also be used in renovated buildings to replace the original high-energy consumption equipment such as gas boilers for heating.

[0003] In summer, the heat source tower in the heat source tower heat pump energy supply system is used as a cooling tower, and cooling water circulates in the heat source tower; in winter, the solution circulates in the heat source tower, which not only solves the problem of frosting and defrosting of the air source heat pump, but also improves the heating efficiency. The reason for using the solution is that when the outdoor air temperature is low in winter, using water as the circulating medium will cause ice and be unfavorable for pipeline transportation. Therefore, it is necessary to use a solution with a freezing point below zero degrees Celsius to replace the cooling water in summer for circulation. The heating efficiency of the heat pump unit in winter is an important parameter. In addition to affecting the heating effect of the unit, it directly affects the operating cost of the system. The solution in the heat source tower exchanges sensible heat and latent heat with the air. The heating efficiency of the heat source tower heat pump system will be high only when the outdoor air dry bulb temperature is high and the humidity is high. The outdoor air parameters change at any time. The air and solution parameters entering the tower determine the solution parameters leaving the tower, and at the same time affect the heating efficiency of the heat source tower heat pump unit. How to maintain the efficient operation of the unit under the premise of meeting the heating load has become an issue that needs urgent attention.

[0004] The concentration change of the solution affects the heat transfer effect of the heat source tower and the freezing point temperature of the solution. Therefore, an online control method for the solution concentration of the heat source tower is proposed, which can timely monitor and adjust the solution concentration of the heat source tower system to ensure the efficient and stable operation of the system. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for online control of the solution concentration in a heat source tower, which can online control the solution concentration in the heat source tower when the heat source tower is operating normally.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for online control of solution concentration in a heat source tower comprises the following steps:

[0008] Step A. To facilitate the establishment of subsequent series of mathematical models, the heat source tower approximate temperature △t is set;

[0009] Step B. Obtain the outdoor wet bulb temperature T1, the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe, and construct a freezing point temperature change model of the solution at the heat source tower outlet;

[0010] Step C. Compare the outdoor wet-bulb temperature T1 and the inlet solution temperature T2 of the heat source tower, and control the heat source tower to enter the water absorption mode or the water loss mode;

[0011] Step D. For the heat source tower water absorption mode, whether the difference between the outdoor wet bulb temperature T1 and the heat source tower approach temperature △t is ≥ the calculated freezing point temperature T3 is the key to controlling the heat source tower solution replenishment electric valve;

[0012] Step E: For the heat source tower dehydration mode, is the liquid level of the heat source tower solution greater than the normal liquid level L? normal It is the key to control the electric valve for liquid replenishment of the heat source tower;

[0013] Step F: When the liquid level L is greater than or equal to L min When the liquid is replenished, the original state is kept unchanged, otherwise the electric valve and the replenishment pump of the heat source tower solution are opened to replenish the liquid.

[0014] As a further preferred embodiment of the method for online control of the solution concentration of a heat source tower of the present invention, in step B, the outdoor wet bulb temperature T1, the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe are obtained, and a freezing point temperature change model of the solution at the heat source tower outlet is constructed as follows:

[0015] T3=f(ρ)

[0016] f(ρ)=T f* -K f *bB

[0017] Where: T3 is the freezing point temperature of the solution at the outlet of the heat source tower, °C; ρ: the density of the solution at the inlet main of the heat source tower, kg / m 3 ; T f* : Freezing point temperature of the solution, °C; K f : Solvent freezing point depression constant, K*Kg / mol; bB: mass molar concentration of solute, mol / Kg.

[0018] As a further preferred embodiment of the method for online control of the solution concentration of a heat source tower of the present invention, in step C, the outdoor wet-bulb temperature T1 and the heat source tower inlet solution temperature T2 are compared to control the heat source tower to enter a water absorption mode or a water loss mode;

[0019] When T1≥T2, the heat source tower enters water absorption mode;

[0020] When T1<T2, the heat source tower enters water loss mode.

[0021] As a further preferred embodiment of the method for online control of the solution concentration of a heat source tower of the present invention, in step D, for the water absorption mode of the heat source tower, whether the difference between the outdoor wet bulb temperature T1 and the heat source tower approach temperature △t is ≥ the calculated freezing point temperature T3 is the key to controlling the electric valve for liquid replenishment of the solution in the heat source tower;

[0022] When T3≤T1-△t, close the electric valve for replenishing the solution in the heat source tower;

[0023] When T3>T1-△t, the electric valve for replenishing the solution in the heat source tower is opened, and the replenishing pump is started.

[0024] As a further preferred embodiment of the method for online control of the solution concentration of a heat source tower of the present invention, in step E, for the water loss mode of the heat source tower, since a liquid level sensor is installed in the heat source tower, the liquid level of the solution can be monitored in time to determine whether the liquid level of the solution in the heat source tower is greater than the normal liquid level L normal Fixed value is the key to control the electric valve of solution replenishment in the heat source tower;

[0025] When L<L normal When the heat source tower solution replenishment electric valve is opened, the replenishment pump is turned on;

[0026] When L<L normal When the liquid replenishment electric valve of the heat source tower is closed, the replenishment pump is turned off.

[0027] As a further preferred embodiment of the method for online control of the solution concentration of a heat source tower of the present invention, in step F, after the heat source tower is in the water absorption mode, when the liquid level sensor measures the liquid level L after closing the electric valve for liquid replenishment of the heat source tower solution, the liquid level L is compared with L min The height of the fixed value;

[0028] When L ≥ L min When , keep the original state unchanged;

[0029] When L<L min When the liquid replenishment electric valve of the heat source tower is opened, the liquid replenishment pump is started.

[0030] The method for online control of the solution concentration in a heat source tower of the present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0031] The invention relates to an online control method for the concentration of a heat source tower solution. In a heat source tower solution that has reached engineering practicality, an approximate temperature △t of the heat source tower is set, an outdoor wet-bulb temperature T1 is obtained, and then a temperature T2 of a solution entering the heat source tower and a density ρ of a solution at a heat source tower liquid inlet main pipe are measured, a variation model of the temperature T2 of a solution entering the heat source tower and the density ρ of a solution at a heat source tower liquid inlet main pipe is established, a freezing point temperature T3 of a solution at a heat source tower outlet is calculated according to the temperature of the solution entering the heat source tower, the start and stop of a liquid replenishing electric valve is controlled, and when the heat source tower is operating normally, the concentration of the solution in the heat source tower is controlled online. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic diagram of the implementation of the logic judgment method for the on-line control method of the heat source tower solution concentration. DETAILED DESCRIPTION

[0033] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0034] The present invention is designed to control the heat source tower heat pump to give full play to its optimal heating capacity. In practical applications, such as Figure 1 As shown, the following steps A to F are specifically performed.

[0035] Step A. To facilitate the establishment of subsequent series of mathematical models, the heat source tower approximate temperature △t is set;

[0036] Step B. Obtain the outdoor wet bulb temperature T1, the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe, and construct a freezing point temperature change model of the solution at the heat source tower outlet;

[0037] Step C. Compare the outdoor wet-bulb temperature T1 and the inlet solution temperature T2 of the heat source tower, and control the heat source tower to enter the water absorption mode or the water loss mode;

[0038] Step D. For the heat source tower water absorption mode, whether the difference between the outdoor wet bulb temperature T1 and the heat source tower approach temperature △t is ≥ the calculated freezing point temperature T3 is the key to controlling the heat source tower solution replenishment electric valve;

[0039] Step E: For the heat source tower dehydration mode, is the liquid level of the heat source tower solution greater than the normal liquid level L? normal It is the key to control the electric valve for liquid replenishment of the heat source tower;

[0040] Step F: When the liquid level L is greater than or equal to L min When the liquid is replenished, the original state is kept unchanged, otherwise the electric valve and the replenishment pump of the heat source tower solution are opened to replenish the liquid.

[0041] As a further preferred embodiment of the method for online control of the solution concentration of a heat source tower of the present invention, in step B, the outdoor wet bulb temperature T1, the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe are obtained, and a freezing point temperature change model of the solution at the heat source tower outlet is constructed as follows:

[0042] T3=f(ρ)

[0043] f(ρ)=Tf*-Kf*bB

[0044] Where: T3 is the freezing point temperature of the solution at the outlet of the heat source tower, ℃; ρ: the density of the solution at the inlet main of the heat source tower, kg / m3;

[0045] Tf*: freezing point temperature of the solution, ℃; Kf: freezing point depression constant of the solvent, K*Kg / mol; bB: mass molar concentration of the solute, mol / Kg.

[0046] In step C, the outdoor wet-bulb temperature T1 and the inlet solution temperature T2 of the heat source tower are compared to control the heat source tower to enter the water absorption mode or the water loss mode;

[0047] When T1≥T2, the heat source tower enters water absorption mode;

[0048] When T1<T2, the heat source tower enters water loss mode.

[0049] In step D, for the heat source tower water absorption mode, whether the difference between the outdoor wet bulb temperature T1 and the heat source tower approach temperature △t is ≥ the calculated freezing point temperature T3 is the key to controlling the heat source tower solution replenishment electric valve;

[0050] When T3≤T1-△t, close the electric valve for replenishing the solution in the heat source tower;

[0051] When T3>T1-△t, the electric valve for replenishing the solution in the heat source tower is opened, and the replenishing pump is started.

[0052] In the step E, for the heat source tower dehydration mode, since a liquid level sensor is installed in the heat source tower, the liquid level of the solution can be monitored in time. Whether the liquid level of the heat source tower solution is greater than the normal liquid level Lnormal fixed value is the key to controlling the heat source tower solution replenishment electric valve;

[0053] When L<Lnormal, open the electric valve for replenishing the solution in the heat source tower and start the replenishing pump;

[0054] When L<Lnormal, close the heat source tower solution replenishment electric valve and turn off the replenishment pump.

[0055] In the step F, after the heat source tower is in the water absorption mode, when the liquid level sensor measures the liquid level L after closing the heat source tower solution replenishment electric valve, the liquid level L is compared with the Lmin fixed value;

[0056] When L≥Lmin, keep the original state unchanged;

[0057] When L<Lmin, open the heat source tower solution replenishment electric valve and start the replenishment pump.

[0058] The invention relates to an online control method for the concentration of a heat source tower solution. In a heat source tower solution that has reached engineering practicality, an approximate temperature △t of the heat source tower is set, an outdoor wet-bulb temperature T1 is obtained, and then a temperature T2 of a solution entering the heat source tower and a density ρ of a solution at a heat source tower liquid inlet main pipe are measured, a variation model of the temperature T2 of a solution entering the heat source tower and the density ρ of a solution at a heat source tower liquid inlet main pipe is established, a freezing point temperature T3 of a solution at a heat source tower outlet is calculated according to the temperature of the solution entering the heat source tower, the start and stop of a liquid replenishing electric valve is controlled, and when the heat source tower is operating normally, the concentration of the solution in the heat source tower is controlled online.

[0059] The online control method of the heat source tower solution concentration designed by the above technical scheme sets the heat source tower approximation temperature △t in the heat source tower solution that has reached engineering practicality, obtains the outdoor wet-bulb temperature T1, then measures the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe, establishes a change model of the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe, calculates the freezing point temperature T3 of the solution at the heat source tower outlet through the heat source tower inlet solution temperature, controls the start and stop of the liquid replenishment electric valve, and controls the heat source tower solution concentration online when the heat source tower is operating normally.

[0060] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for online control of solution concentration in a heat source tower, characterized in that: The specific steps include: Step A. To facilitate the establishment of subsequent series of mathematical models, the heat source tower approximate temperature △t is set; Step B. Obtain the outdoor wet bulb temperature T1, the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe, and construct a freezing point temperature change model of the solution at the heat source tower outlet; Step C. Compare the outdoor wet-bulb temperature T1 and the inlet solution temperature T2 of the heat source tower, and control the heat source tower to enter the water absorption mode or the water loss mode; Step D. For the heat source tower water absorption mode, whether the difference between the outdoor wet bulb temperature T1 and the heat source tower approach temperature △t is ≥ the calculated freezing point temperature T3 is the key to controlling the heat source tower solution replenishment electric valve; Step E: For the heat source tower dehydration mode, is the liquid level of the heat source tower solution greater than the normal liquid level L? normal It is the key to control the electric valve for liquid replenishment of the heat source tower; Step F: When the liquid level L is greater than or equal to L min When the liquid is replenished, the original state is kept unchanged, otherwise the electric valve and the replenishment pump of the heat source tower solution are opened to replenish the liquid.

2. The method for online control of solution concentration in a heat source tower according to claim 1, characterized in that: In step B, the outdoor wet bulb temperature T1, the heat source tower inlet solution temperature T2 and the solution density ρ at the heat source tower inlet main pipe are obtained, and a freezing point temperature change model of the solution at the heat source tower outlet is constructed as follows: T3=f(ρ) f(ρ)=T f* -K f *bB Where: T3 is the freezing point temperature of the solution at the outlet of the heat source tower, °C; ρ: the density of the solution at the inlet main of the heat source tower, kg / m 3 ; T f* : Freezing point temperature of the solution, °C; K f : Solvent freezing point depression constant, K*Kg / mol; bB: mass molar concentration of solute, mol / Kg.

3. The method for online control of solution concentration in a heat source tower according to claim 1, characterized in that: In step C, the outdoor wet-bulb temperature T1 and the inlet solution temperature T2 of the heat source tower are compared to control the heat source tower to enter the water absorption mode or the water loss mode; When T1≥T2, the heat source tower enters water absorption mode; When T1<T2, the heat source tower enters water loss mode.

4. The method for online control of solution concentration in a heat source tower according to claim 1, characterized in that: In step D, for the heat source tower water absorption mode, whether the difference between the outdoor wet bulb temperature T1 and the heat source tower approach temperature △t is ≥ the calculated freezing point temperature T3 is the key to controlling the heat source tower solution replenishment electric valve; When T3≤T1-△t, close the electric valve for replenishing the solution in the heat source tower; When T3>T1-△t, the heat source tower solution replenishment electric valve is opened and the replenishment pump is started.

5. The method for online control of solution concentration in a heat source tower according to claim 1, characterized in that: In step E, for the heat source tower dehydration mode, since a liquid level sensor is installed in the heat source tower, the liquid level of the solution can be monitored in time to determine whether the liquid level of the heat source tower solution is greater than the normal liquid level L. normal Fixed value is the key to control the electric valve of solution replenishment in the heat source tower; When L<L normal When the heat source tower solution replenishment electric valve is opened, the replenishment pump is turned on; When L<L normal When the liquid replenishment electric valve of the heat source tower is closed, the liquid replenishment pump is turned off.

6. The method for online control of solution concentration in a heat source tower according to claim 1, characterized in that: In step F, after the heat source tower is in the water absorption mode, when the liquid level sensor measures the liquid level L after closing the heat source tower solution replenishment electric valve, the liquid level L is compared with L min The height of the fixed value; When L ≥ L min When , keep the original state unchanged; When L<L min When the liquid replenishment electric valve of the heat source tower is opened, the liquid replenishment pump is started.

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