Efficient energy-saving control method for evaporative cooler set

Abstract

The invention provides a high-efficiency energy-saving control method for an evaporative cooler group, which comprises the following steps: S110, a fan of the evaporative cooler group is a fixed-frequency fan, so that only an optimal cooling water spraying amount interval corresponding to rated air volume needs to be determined, an inlet valve M1-41 is adjusted to control the inlet flow of process fluid to be a rated value and the inlet temperature to be a design value or a fixed value, and the optimal cooling water spraying amount interval is determined; and the rated power of the fan is kept, the valves M1-42 are adjusted to control the cooling spraying water amount to change between design values, the outlet temperature of the process fluid under all the cooling water amounts is recorded, the heat exchange amount of the process fluid is calculated, and the optimal spraying water amount under the rated air amount is determined according to the power consumption of the cooling water pump and the heat exchange amount. The energy consumption of the fan and the water pump is reduced as much as possible while the operation condition change is met, and the efficient operation time of the heat exchange pipe is prolonged. During operation, the dirt thermal resistance value and the change rule of the heat exchange pipe are monitored to guide equipment operation and heat exchange pipe cleaning, so that the thermal load processing capacity of the evaporative cooler set is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of evaporative cooling, and in particular to a high-efficiency energy-saving control method for an evaporative cooler group. Background Art

[0002] An evaporative cooler is a heat exchange device in which heat exchange tubes are placed under spray water. Air flows from the bottom of the heat exchange tubes through the spray water film on the surface of the heat exchange tubes with the help of a fan, and is finally discharged into the atmosphere from the top. During operation, the air takes away some moisture to achieve the purpose of evaporative cooling. Since the process fluid is always in the heat exchange tubes, its quality can be guaranteed to be uncontaminated, ensuring the stable operation of the main equipment and increasing its service life. The evaporative cooler has a compact structure, high heat transfer efficiency, and is easy to install and maintain. It is widely used in industries such as oil refining, metallurgy, electricity, and refrigeration.

[0003] Usually, when the process fluid heat exchange rate is not high, one evaporative cooler can meet the requirement, such as a chiller. When the process fluid heat exchange rate is large and there are load changes, multiple evaporative coolers need to be operated in parallel, such as closed-loop cooling of iron-making blast furnaces. When the heat load of the evaporative cooler group is reduced, the air volume and cooling water volume are reduced or deviated from the efficient heat exchange range, such as turning off the fan, and keeping the spray water and other operating parameters unchanged; turning off the spray water of the evaporative cooler, keeping the fan and other operating parameters unchanged, although these control methods can meet the load regulation requirements, when the fan is turned off, the heat transfer coefficient between the medium in the tube and the spray water outside the tube is low, the pump operation consumes high energy, and it is easy to cause scale accumulation outside the heat exchange tube, affecting the heat exchange effect; when the spray water is turned off and the fan is kept running, only the sensible heat of the air changes, the heat exchange rate is small, the fan energy consumption increases, and at the same time, the life of the air inlet equipment is reduced. The evaporative cooler is designed with a certain heat exchange margin, and the heat load will also change during the production process. Therefore, it is of great significance to maintain the efficient operation of the evaporative cooler and reduce unnecessary energy consumption of the fan and water pump. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] The purpose of the present application is to prevent the evaporative cooler from operating in air-cooling, water-cooling or other low heat exchange efficiency states.

[0006] (II) Technical solution

[0007] A high-efficiency energy-saving control method for an evaporative cooler group comprises the following steps:

[0008] S110: The fan of the evaporative cooler group is a fixed-frequency fan, so it is only necessary to determine the optimal cooling water spray volume range corresponding to the rated air volume, adjust the inlet valve M1-41 to control the process fluid inlet flow rate to the rated value, the inlet temperature to the design value or a certain value, maintain the rated power of the fan, adjust the valve M1-42 to control the cooling spray water volume to change between the design values, record the outlet temperature of the process fluid under each cooling water volume, calculate the process fluid heat exchange, and determine the optimal spray water volume under the rated air volume according to the power consumption and heat exchange of the cooling water pump;

[0009] The actual change of spray water volume will cause the change of air volume. The air outlet of the evaporative cooler on the test bench is equipped with a wind speed monitoring instrument. The actual air volume value can be calculated according to the wind tube parameters, and the air volume can be corrected accordingly. When the difference between the actual air volume and the rated air volume is small, the influence of the air volume change can be ignored. If the difference of the air volume is large, the fan power consumption can be taken into account when determining the optimal spray water volume.

[0010] S120: Turn on the fan, adjust valve M1-42 so that the cooling water flow corresponds to the optimal spray water density, keep the medium inlet flow unchanged, adjust the inlet temperature, and make the temperature change as close to the upper and lower limits of the heat load range as possible. Select different air parameters for testing under various temperature conditions;

[0011] S130: Calculate the current heat transfer coefficient and the initial tube outer wall fouling thermal resistance.

[0012] S140: During operation, the flow rate and temperature after the process fluid inlet pipeline valve M1-41 are obtained, and the process fluid outlet temperature is the set value. The total heat exchange is calculated. Usually, the process fluid flow rate is relatively stable, and it is mainly regulated by the variable frequency pump during operation. When the flow rate change affects the normal heat exchange of the evaporative cooler, the process fluid pump frequency, the M-III valve in zone III, the M-II valve in zone II, etc. can be adjusted at the same time to control the fluid in the evaporative cooler pipe to be near the rated value;

[0013] Get the current air dry-bulb temperature and wet-bulb temperature, calculate the heat exchange area according to the structural parameters of the evaporative cooler heat exchange tube, calculate the outlet temperature of the fluid in the tube, the outlet temperature of the cooling water and the heat exchange of the evaporative cooler under the current tube fluid temperature and air parameters, and determine the number of evaporative coolers required based on the total load of the process fluid and the calculation error of the heat exchange;

[0014] S150: Adjust the cooling water flow rate of the cooling water pump outlet main pipe according to the total amount of cooling spray water of a single unit and the number of evaporative coolers in operation;

[0015] S160: Turn on the fixed-frequency fan and select the optimal spray water volume under the corresponding air volume to obtain the maximum heat exchange of a single evaporative cooler under the current environment. Turn off the fan and cooling water inlet of the evaporative cooler that is not in operation, reduce the power consumption of the fan and cooling water pump, and reduce the loss of the fan and air filter device to extend the service life; reduce the scouring of the copper pipe by the cooling spray water, reduce the rate of dirt generation on the outside of the copper pipe, and extend the efficient heat exchange time of the copper pipe;

[0016] S170: Calculate the heat transfer coefficient from the fluid in the tube to the spray water according to the current operation data, and respectively calculate the convection heat transfer coefficient from the fluid in the tube to the inner wall of the copper tube, the thermal conductivity from the inner wall to the outer wall of the copper tube, the convection heat transfer coefficient from the outer wall of the copper tube to the cooling water, etc., calculate and obtain the current copper tube outer wall dirt thermal resistance, and draw a dirt thermal resistance change curve with the fan operation time as the horizontal axis and the heat exchange tube outer wall dirt thermal resistance as the vertical axis. When the copper tube outer wall dirt thermal resistance exceeds the preset value, an alarm is issued on the system operation interface.

[0017] Preferably, the heat exchange capacity of a single evaporative cooler is calculated based on the optimal spray water volume determined in S110, the heat exchange tube structural parameters, the fluid flow rate in the tube, the inlet temperature, the fan air volume, the cooling water flow rate, the inlet temperature, and the air parameters. The actual heat exchange capacity of the evaporative cooler is calculated based on the fluid flow rate in the tube, the inlet temperature, and the outlet temperature monitored during operation. The error value of the calculated heat exchange capacity under each operating condition is analyzed, and the error trend is analyzed.

[0018] Preferably, the design value of S110 is 85% to 115%.

[0019] Preferably, in the quenching and heat-insulating treatment, the proportions of the components of the mixed solution of sodium sulfate, sodium chloride and sodium iodide are 40% sodium sulfate, 40% sodium chloride and 20% sodium iodide.

[0020] Preferably, the total heat exchange of the medium is obtained according to the outlet temperature of the medium, the outlet temperature of the cooling water, and the dry-bulb temperature of the air at the fan outlet at different inlet temperatures during the test.

[0021] Q r =c·m·Δt (1)

[0022] Among them, Q r The total heat transfer capacity of the medium, c is the specific heat capacity of the medium, m is the mass flow rate of the medium, and Δt is the inlet and outlet temperature difference of the medium.

[0023] Heat exchange causes an increase in air humidity and cooling water temperature. The air temperature will also increase, but the increase is generally very small and is usually negligible. Therefore, the total amount of heat absorption can be obtained.

[0024] Q x =q f ·r·Δd+q w ·cw ·Δt (2)

[0025] Among them, Q x is the total heat absorption, q f is the air volume, r is the latent heat of vaporization of water, Δd is the change in moisture content before and after the air enters the evaporative cooler, q w is the cooling water flow rate, c w is the specific heat capacity of water, and Δt is the temperature difference between the inlet and outlet of cooling water.

[0026] According to the heat balance, the total heat exchange of the cooling medium is equal to the total heat absorption of air and water, that is,

[0027] Q r =Q x (3).

[0028] Preferably, the actual heat exchange rate of the fluid can be known by knowing the monitoring parameters of the test conditions. The calculated heat exchange rate of the process fluid under each test condition is compared with the actual heat exchange rate value to obtain the error and trend between the calculated heat exchange rate and the actual value under each condition;

[0029] During operation, the total flow rate and temperature of the fluid to be cooled are obtained. Usually, the temperature of the supplied process fluid is kept stable, that is, the final outlet temperature of the fluid in the pipe remains unchanged. The heat load of the process fluid can be calculated according to formula (1);

[0030] Calculate the heat exchange capacity of a single evaporative cooler based on the current process fluid temperature and current air parameters, and adjust the heat exchange capacity appropriately based on the calculation error;

[0031] The number of evaporative coolers to be put into operation is determined based on the heat load of the process fluid and the heat exchange capacity of a single evaporative cooler. For equipment not in operation, the fan and cooling water are kept closed to save energy consumption of the pump and fan and maintain efficient heat exchange of the copper tube;

[0032] Calculate the heat transfer coefficient K0 from the heat exchange tube to the cooling spray water under the above working conditions (based on the inner surface of the tube)

[0033]

[0034] where α i is the convection heat transfer coefficient between the fluid in the tube and the inner surface of the tube, J / (m 2 ·s·℃), α o Convective heat transfer coefficient between the spray water outside the tube and the outer surface of the tube, J / (m 2 ·s·℃), r i , r o are the thermal resistance of dirt on the inner and outer walls of the tube, m 2 ·s·℃ / J,d i , d o are the inner and outer diameters of the tube, m and d respectivelym is the logarithmic mean diameter of heat transfer, m

[0035]

[0036] Convective heat transfer coefficient α between the outer surface of the tube and the spray water o There is an empirical formula

[0037]

[0038] The test range of this formula is 0.694 <G max <5.278

[0039] Among them, t f is the spray water film temperature, t f =(t w +t t ) / 2,G max is the mass flow rate of wet air at the minimum cross section (average at the inlet and outlet of the evaporative cooler), Γ is the flow rate flowing through the unit width, and when the triangles are staggered

[0040]

[0041] Among them, M w is the mass flow rate of spray water, m is the number of heat exchange tubes in a row, l is the length of the heat exchange tube, m

[0042] When the thermophysical properties of the fluid in the tube are similar to those of water, α i It can be calculated by the following formula

[0043]

[0044] Among them, t t is the temperature of the fluid in the tube, °C, ω is the flow rate of the fluid in the tube, m / s.

[0045] Preferably, the fluid in the tube

[0046] Q r =K O ·S·Δt m (9)

[0047] Where S is the surface area of ​​the heat exchange tube, Δt m is the average heat transfer temperature difference between the fluid inside the tube and the fluid outside the tube

[0048] Δt m =ψΔt m,c (10)

[0049] Among them, Δt m,c is the logarithmic mean temperature difference calculated in countercurrent mode, ψ is the cross-flow correction factor, and the evaporative cooler correction factor can usually be written as

[0050]

[0051] Among them, P is the ratio of the temperature change of the fluid in the tube to the temperature difference between the fluid in the tube and the cooling water inlet, and R is the ratio of the cooling water temperature change to the temperature difference between the inlet and outlet of the fluid in the tube.

[0052] (III) Beneficial effects

[0053] The present invention provides a high-efficiency energy-saving control method for an evaporative cooler group. It has the following beneficial effects:

[0054] While meeting the changes in operating conditions, reduce the energy consumption of fans and water pumps as much as possible, extend the efficient operation time of heat exchange tubes, and extend the service life of equipment to a certain extent. Monitor the heat exchange tube fouling thermal resistance value and change rules during operation to guide equipment commissioning and heat exchange tube cleaning to ensure the heat load handling capacity of the evaporative cooler group. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A schematic flow chart of the steps of a high-efficiency energy-saving control method for an evaporative cooler group proposed by the present invention;

[0056] Figure 2 A schematic diagram of a high-efficiency energy-saving control method for an evaporative cooler group is provided in the present invention;

[0057] Figure 3 The present invention provides a partial structural schematic diagram of a high-efficiency energy-saving control method for an evaporative cooler group. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] Embodiment: The present invention provides a high-efficiency energy-saving control method for an evaporative cooler group, comprising the following steps:

[0060] S110: Since the fan of the evaporative cooler group in this example is a fixed-frequency fan, it is only necessary to determine the optimal cooling water flow range corresponding to the rated air volume. The specific implementation is to adjust Figure 3The inlet valve M1-41 shown controls the inlet flow of the process fluid to the rated value, and the inlet temperature to the design value or a certain value, maintains the rated power of the fan, adjusts the valve M1-42 to control the cooling spray water volume to vary between 85% and 115% of the design value, records the outlet temperature of the process fluid under various cooling water volumes, calculates the heat exchange of the process fluid, and determines the optimal spray water volume under the rated air volume based on the power consumption and heat exchange of the cooling water pump.

[0061] Changes in the actual spray water volume will cause changes in the air volume. A wind speed monitoring instrument is set at the air outlet of the evaporative cooler on the test bench. The actual air volume value can be calculated based on the wind tube parameters, and the air volume is corrected accordingly. When the difference between the actual air volume and the rated air volume is small, the impact of the air volume change can be ignored. If the air volume difference is large, the fan power consumption can be taken into account when determining the optimal spray water volume.

[0062] S120: Turn on the fan, adjust valve M1-42 so that the cooling water flow corresponds to the optimal spray water density, keep the medium inlet flow unchanged, adjust the inlet temperature, and make the temperature change as close to the upper and lower limits of the heat load range as possible. Select different air parameters for testing under each temperature condition.

[0063] The heat exchange of a single evaporative cooler is calculated based on the optimal spray water volume determined by S110, the heat exchange tube structural parameters, the fluid flow rate in the tube, the inlet temperature, the fan air volume, the cooling water flow rate, the inlet temperature, and the air parameters. The actual heat exchange of the evaporative cooler is calculated based on the fluid flow rate, inlet temperature, and outlet temperature of the tube monitored during operation, and the error value and error trend of the calculated heat exchange under various working conditions are analyzed.

[0064] S130: The current heat transfer coefficient can be obtained according to formulas (9)-(11), and the initial tube outer wall fouling thermal resistance can be obtained according to formula (4).

[0065] S140: During operation, the flow rate and temperature after the process fluid inlet pipeline valve M1-41 are obtained, and the process fluid outlet temperature is the set value, and the total heat exchange is calculated. Usually, the process fluid flow rate is relatively stable, and it is mainly regulated by the variable frequency pump during operation. When the flow change affects the normal heat exchange of the evaporative cooler, the process fluid pump frequency, the M-III valve in zone III, the M-II valve in zone II, etc. can be adjusted at the same time to control the fluid in the evaporative cooler pipe to be near the rated value.

[0066] Get the current air dry bulb temperature and wet bulb temperature, and calculate the heat exchange area according to the structural parameters of the evaporative cooler heat exchange tube. Calculate the outlet temperature of the fluid in the tube, the outlet temperature of the cooling water, and the heat exchange of the evaporative cooler under the current tube fluid temperature and air parameters. According to the total load of the process fluid, consider the calculation error of the heat exchange, and determine the number of evaporative coolers that need to be invested.

[0067] S150: Adjust the cooling water flow rate of the cooling water pump outlet main pipe according to the total amount of cooling spray water of a single unit and the number of evaporative coolers in operation. In this example, there are 24 evaporative coolers in total. When adjusting between 24 and 8 units, the adjustment interval is 2 units to avoid frequent opening and closing of valves when the heat load fluctuates slightly or the air parameters fluctuate, and to maintain a certain heat exchange margin. When less than 8 units are in operation, the adjustment interval is 4 units, which can be used for adjustment under abnormal heat load conditions. For example, according to the calculation in S140, 19 units need to be put into operation. Then, the M-31 valve in Zone III and the M-21 valve in Zone II of the cooling water system can be closed, and 8 evaporative coolers in Zone I, 6 evaporative coolers in Zone II, and 4 evaporative coolers in Zone III can be put into operation, for a total of 20 evaporative coolers.

[0068] S160: Turn on the fixed-frequency fan and select the optimal spray water volume under the corresponding air volume to obtain the maximum heat exchange of a single evaporative cooler under the current environment. Turn off the fan and cooling water inlet of the evaporative cooler that is not in operation to reduce the power consumption of the fan and cooling water pump, while reducing the loss of the fan and air filter device and extending the service life; reduce the scouring of the copper pipe by the cooling spray water, reduce the rate of dirt generation on the outside of the copper pipe, and extend the efficient heat exchange time of the copper pipe.

[0069] S170: Calculate the heat transfer coefficient from the fluid in the tube to the spray water according to the current operation data, and respectively calculate the convection heat transfer coefficient from the fluid in the tube to the inner wall of the copper tube, the thermal conductivity from the inner wall of the copper tube to the outer wall, the convection heat transfer coefficient from the outer wall of the copper tube to the cooling water, etc., obtain the current copper tube outer wall fouling thermal resistance according to formula (4), and draw a fouling thermal resistance change curve with the fan operation time as the horizontal axis and the heat exchange tube outer wall fouling thermal resistance as the vertical axis. When the copper tube outer wall fouling thermal resistance exceeds the preset value, an alarm is issued on the system operation interface. Since the cooling water is centrally supplied and has the same water quality, the time margin for cleaning the heat exchange tubes of other evaporative coolers can be estimated according to the test bench heat exchange tube outer wall fouling thermal resistance change curve.

[0070] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0071] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency energy-saving control method for an evaporative cooler group, characterized in that: The following steps are involved: S110: The fan of the evaporative cooler group is a fixed-frequency fan, so it is only necessary to determine the optimal cooling water spray volume range corresponding to the rated air volume, adjust the inlet valve M1-41 to control the process fluid inlet flow rate to the rated value, the inlet temperature to the design value or a certain value, maintain the rated power of the fan, adjust the valve M1-42 to control the cooling spray water volume to change between the design values, record the outlet temperature of the process fluid under each cooling water volume, calculate the process fluid heat exchange, and determine the optimal spray water volume under the rated air volume according to the power consumption and heat exchange of the cooling water pump; The actual change of spray water volume will cause the change of air volume. The air outlet of the evaporative cooler on the test bench is equipped with a wind speed monitoring instrument. The actual air volume value can be calculated according to the wind tube parameters, and the air volume can be corrected accordingly. When the difference between the actual air volume and the rated air volume is small, the influence of the air volume change can be ignored. If the difference of the air volume is large, the fan power consumption can be taken into account when determining the optimal spray water volume. S120: Turn on the fan, adjust valve M1-42 so that the cooling water flow corresponds to the optimal spray water density, keep the medium inlet flow unchanged, adjust the inlet temperature, and make the temperature change as close to the upper and lower limits of the heat load range as possible. Select different air parameters for testing under various temperature conditions; S130: Calculate the current heat transfer coefficient and the initial tube outer wall fouling thermal resistance. S140: During operation, the flow rate and temperature after the process fluid inlet pipeline valve M1-41 are obtained, and the process fluid outlet temperature is the set value. The total heat exchange is calculated. Usually, the process fluid flow rate is relatively stable, and it is mainly regulated by the variable frequency pump during operation. When the flow rate change affects the normal heat exchange of the evaporative cooler, the process fluid pump frequency, the M-III valve in zone III, the M-II valve in zone II, etc. can be adjusted at the same time to control the fluid in the evaporative cooler pipe to be near the rated value; Get the current air dry-bulb temperature and wet-bulb temperature, calculate the heat exchange area according to the structural parameters of the evaporative cooler heat exchange tube, calculate the outlet temperature of the fluid in the tube, the outlet temperature of the cooling water and the heat exchange of the evaporative cooler under the current tube fluid temperature and air parameters, and determine the number of evaporative coolers required based on the total load of the process fluid and the calculation error of the heat exchange; S150: Adjust the cooling water flow rate of the cooling water pump outlet main pipe according to the total amount of cooling spray water of a single unit and the number of evaporative coolers in operation; S160: Turn on the fixed-frequency fan and select the optimal spray water volume under the corresponding air volume to obtain the maximum heat exchange of a single evaporative cooler under the current environment. Turn off the fan and cooling water inlet of the evaporative cooler that is not in operation, reduce the power consumption of the fan and cooling water pump, and reduce the loss of the fan and air filter device to extend the service life; reduce the scouring of the copper pipe by the cooling spray water, reduce the rate of dirt generation on the outside of the copper pipe, and extend the efficient heat exchange time of the copper pipe; S170: Calculate the heat transfer coefficient from the fluid in the tube to the spray water according to the current operation data, and respectively calculate the convection heat transfer coefficient from the fluid in the tube to the inner wall of the copper tube, the thermal conductivity from the inner wall to the outer wall of the copper tube, the convection heat transfer coefficient from the outer wall of the copper tube to the cooling water, etc., calculate and obtain the current copper tube outer wall dirt thermal resistance, and draw a dirt thermal resistance change curve with the fan operation time as the horizontal axis and the heat exchange tube outer wall dirt thermal resistance as the vertical axis. When the copper tube outer wall dirt thermal resistance exceeds the preset value, an alarm is issued on the system operation interface.

2. The high-efficiency energy-saving control method of the evaporative cooler group according to claim 1, characterized in that: According to the optimal spray water volume determined by S110, the structural parameters of the heat exchange tube, the fluid flow rate in the tube, the inlet temperature, the fan air volume, the cooling water flow rate, the inlet temperature, and the air parameters, the heat exchange rate of a single evaporative cooler is calculated. The actual heat exchange rate of the evaporative cooler is calculated according to the fluid flow rate in the tube, the inlet temperature, and the outlet temperature monitored during operation. The error value of the calculated heat exchange rate under various working conditions is analyzed, and the error trend is analyzed.

3. The high-efficiency energy-saving control method of the evaporative cooler group according to claim 1, characterized in that: The design value of s110 is 85% to 115%.

4. The high-efficiency energy-saving control method of the evaporative cooler group according to claim 1, characterized in that: According to the different inlet temperatures during the test, the outlet temperature of the medium, the outlet temperature of the cooling water, and the dry-bulb and wet-bulb temperatures of the air at the fan outlet, the total heat transfer of the medium is obtained. Q r =c·m·Δt (1) Among them, Q r The total heat transfer capacity of the medium, c is the specific heat capacity of the medium, m is the mass flow rate of the medium, and Δt is the inlet and outlet temperature difference of the medium. Heat exchange causes an increase in air humidity and cooling water temperature. The air temperature will also increase, but the increase is generally very small and is usually negligible. Therefore, the total amount of heat absorption can be obtained. Q x =q f ·r·Δd+q w ·c w ·Δt (2) Among them, Q x is the total heat absorption, q f is the air volume, r is the latent heat of vaporization of water, Δd is the change in moisture content before and after the air enters the evaporative cooler, q w is the cooling water flow rate, c w is the specific heat capacity of water, and Δt is the temperature difference between the inlet and outlet of cooling water. According to the heat balance, the total heat exchange of the cooling medium is equal to the total heat absorption of air and water, that is, Q r =Q x (3)。 5. The high-efficiency energy-saving control method for an evaporative cooler group according to claim 1, characterized in that: The actual heat transfer of the fluid can be known by knowing the monitoring parameters of the test conditions. Compare the calculated heat transfer value of the process fluid under each test condition with the actual heat transfer value, and obtain the error and trend between the calculated heat transfer value and the actual value under each condition; During operation, the total flow rate and temperature of the fluid to be cooled are obtained. Usually, the temperature of the supplied process fluid is kept stable, that is, the final outlet temperature of the fluid in the pipe remains unchanged. The heat load of the process fluid can be calculated according to formula (1); Calculate the heat exchange capacity of a single evaporative cooler based on the current process fluid temperature and current air parameters, and adjust the heat exchange capacity appropriately based on the calculation error; The number of evaporative coolers to be put into operation is determined based on the heat load of the process fluid and the heat exchange capacity of a single evaporative cooler. For equipment not in operation, keep the fan and cooling water closed to save energy consumption of the pump and fan and maintain efficient heat exchange of the copper tube; Calculate the heat transfer coefficient K0 from the heat exchange tube to the cooling spray water under the above working conditions (based on the inner surface of the tube) where α i is the convection heat transfer coefficient between the fluid in the tube and the inner surface of the tube, J / (m 2 ·s·C), α o Convective heat transfer coefficient between the spray water outside the tube and the outer surface of the tube, J / (m 2 ·s·C), r i , r o are the thermal resistance of dirt on the inner and outer walls of the tube, m 2 ·s·C / J, d i , d o are the inner and outer diameters of the tube, m and d respectively m is the logarithmic mean diameter of heat transfer, m Convective heat transfer coefficient α between the outer surface of the tube and the spray water o There is an empirical formula The test range of this formula is 0.694 <G max <5.278 Among them, t f is the spray water film temperature, t f =(t w +t t ) / 2,G max is the mass flow rate of wet air at the minimum cross section (average at the inlet and outlet of the evaporative cooler), Γ is the flow rate flowing through the unit width, and when the triangles are staggered Among them, M w is the mass flow rate of spray water, m is the number of heat exchange tubes in a row, l is the length of the heat exchange tube, m When the thermophysical properties of the fluid in the tube are similar to those of water, α i It can be calculated by the following formula Among them, t t is the temperature of the fluid in the tube, °C, ω is the flow rate of the fluid in the tube, m / s.

6. The high-efficiency energy-saving control method for an evaporative cooler group according to claim 1, characterized in that; Fluid in pipe Q r =K O ·S·Δt m (9) Where S is the surface area of ​​the heat exchange tube, Δt m is the average heat transfer temperature difference between the fluid inside the tube and the fluid outside the tube Δt m =ψΔt m,c (10) Among them, Δt m,c is the logarithmic mean temperature difference calculated in countercurrent mode, ψ is the cross-flow correction factor, and the evaporative cooler correction factor can usually be written as Among them, P is the ratio of the temperature change of the fluid in the tube to the temperature difference between the fluid in the tube and the cooling water inlet, and R is the ratio of the cooling water temperature change to the temperature difference between the inlet and outlet of the fluid in the tube.

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