Working condition analysis control method based on cooling tower heat dissipation

Abstract

The invention relates to the technical field of heat dissipation control of cooling towers of air conditioners, in particular to a working condition analysis control method based on heat dissipation of a cooling tower, which comprises the following steps of: analyzing and calculating metering parameters including water spraying size and air inlet size, and sensor acquisition parameters including air speed, air pressure, air inlet and outlet temperature, relative humidity and water inlet and outlet temperature; a required condensation signal of the air conditioning unit is fed back to a cooling tower heat dissipation working condition analysis controller for control calculation of a cooling tower fan, a coupling relation between wind and water is established, and the frequency of the water pumps is adjusted by adjusting the number of the water pumps; the number of cooling tower fans is adjusted, and the frequency of the fans is adjusted. The purposes of controlling air volume and water volume and economically and reasonably controlling heat dissipation of the cooling tower are achieved, and the operation cost is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of air conditioning cooling tower heat dissipation control, and particularly relates to a working condition analysis control method based on cooling tower heat dissipation BACKGROUND Cooling tower heat dissipation is the core technology of energy-saving control of a central air conditioning high-efficiency machine room, which not only needs to reach the best working condition point of the central air conditioning host device to meet the high-efficiency operation of the host, but also needs to control the cooling tower and the cooling water pump to run economically and reasonably.

[0002] Most of the existing cooling tower heat dissipation control methods are limited to the dew point temperature and the tower proximity as the main control basis to control the running number and running frequency of the cooling tower, such as the invention patent with the name of determination method and system of cooling tower control parameters based on big data deep learning and the publication number of CN119730167A, the essence of which is to collect and analyze the outdoor wet bulb temperature and the cooling tower inlet water temperature.

[0003] There are also methods for analysis from the perspective of heat balance, such as the invention patent with the name of closed cooling tower control method based on differential evolution algorithm and the publication number of CN117128800A, the essence of which is to collect and analyze the temperature and humidity of water and air from the heat balance between water and air. These methods either cannot include the actual process working condition based on the dew point temperature and the tower proximity as the main control basis or cannot reach automation and engineering application through the collection and operation, and thus cannot meet the most economic and reasonable operation requirements.

[0004] The cooling tower heat dissipation is essentially the heat exchange process between wind (air) and water, which is a relational wind-water coupling analysis involving the relationship between the air properties and the water heat exchange properties. The air involves the air volume, air speed, temperature and humidity, state point enthalpy and tower inlet air density, and the water involves the water temperature, water volume, water speed, surface heat exchange involving the surface heat exchange capacity, viscosity and fouling coefficient. The goal of the cooling tower heat dissipation control is to control the air volume (air speed, frequency and number) and water volume (water speed, frequency and number) under the automatic optimization operation working condition of the air conditioning unit. SUMMARY

[0005] The application aims to provide a timely and dynamic analysis and control method for the coupling relationship between wind (air) and water of the cooling tower heat dissipation under the automatic optimization operation working condition of the air conditioning unit. The method can achieve the purpose of controlling the air volume and water volume through the calculation model analysis and calculation of the metering parameters (water spraying size and air inlet size) and the sensor collected parameters (air speed, air pressure, inlet and outlet air temperature, relative humidity and inlet and outlet water temperature) under the automatic optimization operation working condition of the air conditioning unit, so as to economically and reasonably control the cooling tower heat dissipation.

[0006] The dynamic analysis and control device establishes an optimization model based on factors such as air volume, air velocity, temperature and humidity, state point enthalpy, inlet air density, water temperature, water volume, water velocity, surface heat transfer coefficient, and surface heat transfer capacity. It continuously optimizes the cooling tower (frequency and number of units) and cooling water pump (frequency and number of units) during dynamic data acquisition.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The operating condition analysis and control method based on cooling tower heat dissipation specifically includes: Step 1: Read the air conditioning unit's operating data and send it to the gateway; Step 2: The gateway transmits the operating data to the cooling tower heat dissipation condition analysis controller for data analysis, and obtains the SDT-SST curve of the air conditioning unit. At the same time, it also feeds back the output signal to continuously optimize the regression calculation. Step 3: Use the compressor selection software to optimize the T0 of the air conditioning unit based on the SDT-SST curve. 蒸发温度 With TK 冷凝温度 Correspondence table; Step 4: Calculate T0 蒸发温度 With TK 冷凝温度 Correspondence table; Step 5: Standardized T0 蒸发温度 With TK 冷凝温度 The corresponding relationship table calculates the Targ_TK condensation under the corresponding operating condition; Step 6: Derive the target cooling water temperature Targ_TK 冷凝水 TS 进 TS 出 Collect the actual inlet water temperature Tinlet and outlet water temperature Toutlet; calculate the target flow rate Starget flow rate = Qcondensate / ρ × cp × Δt, and collect the actual flow rate LScooling; input the target flow rate Starget flow rate and the collected cooling water flow rate LScooling into the water pump database to deduce the number of water pumps that need to be operated online; establish a PID relationship to control the water pump frequency conversion and adjust the water pump frequency based on the target flow rate Starget flow rate and the collected cooling water flow rate LScooling. Step 7: The Q condensation signal is fed back to the cooling tower heat dissipation condition analysis controller to perform control calculations for the cooling tower fan and establish the coupling relationship between air and water.

[0008] Preferably, the analysis and calculation of the feng shui coupling relationship includes the following steps: (1) Collect water parameters to calculate the heat dissipation of the cooling tower: Collect the cooling tower inlet water temperature Tr, cooling tower outlet water temperature Ts, cooling water flow rate Fv, water density ρ, water specific heat capacity cp, and cooling water temperature difference Δt; cooling tower inlet water temperature Tr = Tin; cooling tower outlet water temperature Ts = Tout; cooling water flow rate Fv = S target flow rate; The cooling tower water heat dissipation is calculated according to the following formula: Qw=Fv×ρ×cp×Δt; (2) The cooling heat Qair=Qwater heat=Qcondensation=Qw; The air volume Va is calculated according to the following formula: Va=Qwater heat / (h1-h0) / 0.95 / ρa; Wherein, h1 is the tower air enthalpy, h1=Cg×Td+0.622×(γ0+CV×Td)×(ф×Pv / (P-ф×Pv)), wherein, the dry air specific heat Cg=1.005, Td is the dry ball air temperature; h0 is the tower air enthalpy, h0=h1+C×Δt / (K×λ), Δt is the temperature difference between the inlet and outlet water; ρa is the tower air density; Pv is the saturated water vapor pressure; γ0 is the water vaporization heat at 0℃ (2500kJ / kg); CV is the water vapor specific heat (1.846kJ / (kg•℃); ф is the relative humidity of the tower air; P is the atmospheric pressure (100.55kpa); γ is the water vaporization heat at the outlet (2420kJ / kg); the heat coefficient K=1-C×Tout / γ; C is the specific heat capacity of water; (3) The fan shaft power W is calculated: W=ΔPtotal×Va×ρa / (η×3600×1000); Wherein, the fan efficiency η=0.85, the fan total pressure ΔPtotal=ΔP / 0.8, the fan static pressure ΔP=ΔP1+ΔP2, the water spraying section resistance ΔP1=ΔP / ρ=3.88•ω^1.66•q^0.49×ρa, the other part resistance ΔP2=ΔP1×40%, the water spraying density q=Starget flow / Fpass, the water passing area Fpass=CT_W×CT_L, CT_W is the filler water passing surface width, CT_L is the filler water passing surface length; The fan shaft power is compared with the actual collected fan shaft power set to determine the reasonable fan running number and to increase or decrease the running fan number in operation.

[0009] Compared with the prior art, the present application has the following beneficial effects: According to the above air conditioning unit equipment heat dissipation and cooling water circuit, the cooling water and cooling tower wind correlation analysis and calculation can obtain: the online water pump running number and water pump running frequency are outputted according to the air conditioning unit, water pump equipment database data optimization calculation; the online fan running number and fan running frequency are outputted according to the cooling tower equipment database data optimization calculation, and the operation cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 It is a cooling tower heat dissipation working condition analysis performance chart in an embodiment.

[0011] Figure 2 It is a control logic diagram of the present application.

[0012] Figure 3 This is a diagram of the control system in this invention.

[0013] Figure 4 This is a structural diagram of the controller in this invention. Detailed Implementation

[0014] Most current control methods for cooling tower heat dissipation are limited to dew point temperature and tower proximity as the main control basis. These are only preliminary single-environmental temperature and humidity conditions and have no relation to the operating performance parameters of the controlled objects: air conditioning units and cooling towers.

[0015] See Figure 2 The working principle of this invention is as follows: S1. First, the operating parameters of the air conditioning unit are collected through communication to obtain the SDT-SST curve of the air conditioning unit; S2. By calling compressor selection software, such as Xecaturbo CompMate (Air Suspension Compressor Selection Software V3.0) adapted for air-suspension compressors, and based on the SDT-SST curve, such as... Figure 1 As shown: Cooling tower heat dissipation performance analysis diagram, namely the working range diagram of "saturated suction temperature (SST)" and "saturated exhaust temperature (SDT)". According to the set return steam superheating parameters and condensation subcooling parameters, a relational calculation model is established: Under the set performance parameters, namely the set TK evaporation, exhaust subcooling and suction superheating temperatures, the optimal dynamic condensing temperature Targ_TK condensing with a higher COP value of the air conditioning unit is obtained. Where TK represents the evaporation temperature of the air conditioning unit, and Targ_TK represents the condensation temperature. : Where is the condensation temperature, and Targ_TK is the average water-side temperature; Targ_TK condensate = E × Targ_TK condensate; E = [1 / ain + Ain / (Aoa0)] - 1; E is the total surface heat transfer coefficient, ain is the heat transfer coefficient inside the heat exchange tube, a0 is the heat transfer coefficient outside the heat exchange tube, and Ain / Ao is the ratio of the heat transfer area inside and outside the tube. Q condensation = Q evaporation + Wtot + Q loss = Q evaporation (1 + α) + Wtot; Q represents the evaporation energy (cooling capacity); α represents the heat loss rate, an empirical formula related to cooling capacity; Wtot represents the compressor power consumption. Q_evaporation is read from the chilled water energy meter connected to the air conditioning unit via communication, and W_tot is read from the electricity meter connected to the air conditioning unit via communication. Calculated based on a Δ5℃ temperature difference under standard condenser operating conditions, i.e.: TS_in = Targ_TK_condensate - 2.5; TSout = Targ_TKcondensate water + 2.5; TSin is the calculated cooling water inlet temperature, and TSout is the calculated cooling water outlet temperature; S target flow = Q condensation / p x cp x Δt; LScooling is the cooling water collection flow; p is the density of water, cp is the specific heat capacity of water, and Δt is the cooling water temperature difference; Δt' = T in - T out: Δt' is the corrected temperature difference; Tin is the collected cooling water inlet temperature, and Tout is the collected cooling water outlet temperature; TSout = TSin + Q condensation / LScooling x p x cp; LScooling is the cooling water collection flow, p is the density of water, and cp is the specific heat capacity of water; Total flow of the cooling water pump: S actual = ∑ (S pump1, S pump2, S pump3, S pump4... S pumpn); S pumpn rated is the best (1, 2, 3, 4 pumps corresponding to the best flow) determined according to the pump resistance characteristic curve, which is the best matching of the use type pump and the pipe network; The number of water pumps is controlled according to: S target flow / S pumpn rated = (1, 2, 3...) = n, n is the calculated required cooling water pump number, n_pmp is the collected actual running pump number, and N and n_pmp are compared to determine the number of water pump running increase or decrease; According to S 目标流量 , S 实际流量 PID relationship is established to carry out the cooling water pump frequency conversion.

[0016] Among them, the wind-water coupling analysis and calculation, cooling tower structure, and environmental condition calculation steps are as follows: (1) Collect water parameters to calculate the cooling tower heat dissipation: collect the cooling tower inlet water temperature Tr, the cooling tower outlet water temperature Ts, the cooling water flow Fv, the density of water p, the specific heat capacity of water cp, and the cooling water temperature difference Δt; the cooling tower inlet water temperature Tr = T out; the cooling tower outlet water temperature Ts = T in; and the cooling water flow Fv = S target flow; Calculate the cooling tower heat dissipation: Qw = Fv x p x cp x Δt; (2) According to the cooling heat Q air = Q water heat = Q condensation = Qw; calculate the required air volume Va = Q water heat / (h1 - h0) / 0.95 / p a; Among them, h1 is the inlet tower air enthalpy, h0 is the outlet tower air enthalpy, and p a is the air density; Saturation water vapor pressure: Pv = 611.2 x EXP((18.678 - Td / 234.5) x Td / (Td + 257.14)); Td is dry bulb air temperature; Wet bulb temperature; ts=(-5.806+0.672×td-0.006×td^2+(0.061+0.004×td+0.000099×td^2)×RH×100+(-0.000033-0.000005×td-0.0000001×td^2)×(RH×100)^2); RH is relative humidity; Air density into the tower: ρa=0.003484×(101325-Pv×RH / 100) / (Td1+273.15)+0.002169×Pv×RH / 100 / (Td1+273.15); Pv is saturated water vapor pressure; Dry air specific heat Cg=1.005,0℃ water vaporization heat γ0=2500kJ / kg,water vapor specific heat CV=1.846kJ / (kg•℃),out of tower water temperature vaporization heat γ=2420kJ / kg,ф is relative humidity of air into the tower,atmospheric pressure P=100.55kpa,water specific heat C=4.19kJ / (kg•℃); Calculate the enthalpy of air into the tower h1=Cg×Td+0.622×(γ0+CV×Td)×(ф×Pv / (P-ф×Pv)); Calculate the enthalpy of air out of the tower h0=h1+C×Δt / (K×λ); Heat coefficient K=1-C×Tout / γ; Packing calculation Water specific heat capacity C,water temperature difference Δt,air enthalpy into the tower h1,air enthalpy out of the tower h0,water temperature into the tower saturated air enthalpy hi1,water temperature out of the tower saturated air enthalpy hi2,average water temperature air enthalpy hm1,average water temperature saturated air enthalpy hm0; Calculate cooling number N=C×Δt×(1 / (hi2-h1)+4 / (hm0-hm1)+1 / (hi1-h0)) / 6; Calculate mass transfer coefficient βxv=(N×1000Q) / (V×K); The cooling number N' calculated by packing is 1.2476×λ^0.5585; Mass transfer coefficient of packing itself βxv'= (B×Vg)^(m×q)^n; m,n are packing constants related to packing material and form; Fan calculation λ=Va×ρa / (Fv×ρ); Wherein, λ: air-water ratio, ρ: water density; Fv=S target flow; Mass air velocity Vg = q x λ x 1000 / 3600; Spray section air velocity ω = Va / (Fpass x 3600); 3) Calculate the fan shaft power W: W = ΔPtotal x Va x pa / (η x 3600 x 1000); Wherein, fan efficiency η = 0.85, fan total pressure ΔPtotal = ΔP / 0.8, fan static pressure ΔP = ΔP1 + ΔP2, spray section resistance ΔP1 = ΔP / ρ = 3.88 • ω ^ 1.66 • q ^ 0.49 x pa, other part resistance ΔP2 = ΔP1 x 40%, spray density q = S_target flow / Fpass, water area Fpass = CT_W x CT_L, CT_W is the filler water surface width, CT_L is the filler water surface length; compare the fan shaft power with the actual collection of all fan shaft power set to determine the reasonable number of fan operation and in operation to increase or decrease the number of running fans.

[0017] Through the cooling tower analysis and calculation of water temperature conditions, cooling tower fan frequency conversion using spray pressure difference PID, cooling tower outlet water PID two methods according to the conditions are respectively two methods of frequency conversion.

[0018] Through the above air conditioning unit equipment heat dissipation and cooling water circuit, cooling water and cooling tower wind correlation analysis and calculation, can be obtained: according to the air conditioning unit, water pump equipment database data optimization calculation output online water pump running number and water pump running frequency; according to the cooling tower equipment database data optimization calculation output online fan running number and fan running frequency.

[0019] The system for completing the above control method is shown in Figure 3 and Figure 4 The cooling tower heat dissipation working condition analysis controller is divided into collection and execution two parts, the collection part is divided into communication collection and data module collection two parts, the communication collection mainly collects air conditioning unit parameters through communication gateway (WG) and communication module (HUB): including evaporation temperature, condensation temperature, set outlet water temperature and refrigerating capacity.

[0020] Through the data module collection: cooling tower inlet air (HT1) temperature and humidity sensor, outlet air (HT2) temperature and humidity sensor; cooling tower inlet water (t1) temperature sensor, cooling tower outlet water (t2) temperature sensor; cooling tower inlet air (FS1) air velocity sensor, cooling tower outlet air (FS2) air velocity sensor, cooling tower cooling water flow (LS), ΔP differential pressure sensor.

[0021] The execution part is based on the analysis of the system, and the online water pump running number and water pump running frequency are outputted according to the water pump equipment database data optimization calculation; the online fan running number and fan running frequency are outputted according to the cooling tower equipment database data optimization calculation.

Claims

1. A method for analyzing and controlling the operating conditions based on cooling tower heat dissipation, characterized in that: Specifically, it includes: Step 1: Read the air conditioning unit's operating data and send it to the gateway; Step 2: The gateway transmits the operating data to the cooling tower heat dissipation condition analysis controller for data analysis, obtains the SDT-SST curve of the air conditioning unit, and also feeds back the output signal to continuously optimize the regression calculation. Step 3: Use the compressor selection software to optimize the T0 of the air conditioning unit based on the SDT-SST curve. 蒸发温度 With TK 冷凝温度 Correspondence table; Step 4: Calculate T0 蒸发温度 With TK 冷凝温度 Correspondence table; Step 5: Standardized T0 蒸发温度 With TK 冷凝温度 The corresponding relationship table calculates the Targ_TK condensation under the corresponding operating condition; Step 6: Derive the target cooling water temperature Targ_TK 冷凝水 TS 进 TS 出 Collect actual inlet water temperature Tinlet and outlet water temperature Toutlet. Calculate the target flow rate S = Q_condensate / ρ × cp × Δt, and collect the actual flow rate: LS_cooling; The number of pumps that need to be operated online is derived by entering the target flow rate S and the collected cooling water flow rate LS into the pump database; based on the target flow rate S and the collected cooling water flow rate LS, a PID relationship is established to control the pump frequency conversion and adjust the pump frequency. Step 7: Feed back the condensation signal to the cooling tower heat dissipation condition analysis controller to perform control calculations for the cooling tower fan and establish the coupling relationship between air and water.

2. The operating condition analysis and control method based on cooling tower heat dissipation as described in claim 1, characterized in that, The analysis and calculation of the feng shui coupling relationship includes the following steps: (1) Collect water parameters to calculate the heat dissipation of the cooling tower: Collect the cooling tower inlet water temperature Tr, cooling tower outlet water temperature Ts, cooling water flow rate Fv, water density ρ, water specific heat capacity cp, and cooling water temperature difference Δt; cooling tower inlet water temperature Tr = Tin; cooling tower outlet water temperature Ts = Tout; cooling water flow rate Fv = S target flow rate; The heat dissipation of cooling tower water is calculated using the following formula: Qw = Fv × ρ × cp × Δt; (2) Cooling heat Q_air = Q_water heat = Q_condensation = Q_w; Calculate the air volume Va according to the following formula: Va = Q_hydrothermal / (h1 - h0) / 0.95 / ρa; Where h1 is the enthalpy of the air entering the tower, h1=Cg×Td+0.622×(γ0+CV×Td)×(ф×Pv / (P-ф×Pv)), where the specific heat of dry air Cg=1.005, and Td is the dry-bulb air temperature; h0 is the enthalpy of the air exiting the tower, h0=h1+C×Δt / (K×λ), where Δt is the temperature difference between the inlet and outlet water; ρa is the density of the air entering the tower; Pv is the saturated water vapor pressure; γ0 is the heat of vaporization of water at 0℃ (2500kJ / kg); CV is the specific heat of water vapor (1.846kJ / (kg•℃); ф is the relative humidity of the air entering the tower; P is the atmospheric pressure (100.55kpa); γ is the heat of vaporization of the water at the outlet temperature (2420kJ / kg); the heat coefficient K=1-C×Tout / γ; C is the specific heat capacity of water; (3) Calculate the fan shaft power W: W = ΔP_total × Va × ρa / (η × 3600 × 1000); Wherein, the fan efficiency η=0.85, the total fan pressure ΔP_total=ΔP / 0.8, the static fan pressure ΔP=ΔP1+ΔP2, the water spray section resistance ΔP1=ΔP / ρ=3.88•ω^1.66•q^0.49×ρa, the resistance of other parts ΔP2=ΔP1×40%, the water spray density q=S target flow rate / F_over, the water flow area F_over=CT_W×CT_L, CT_W is the width of the water flow surface of the packing, and CT_L is the length of the water flow surface of the packing; By comparing the fan shaft power with the actual collected set of all fan shaft power, a reasonable number of fans in operation is determined, and the number of fans in operation is increased or decreased during operation.

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