Method for measuring cooling capacity of mechanical draft cooling tower group

Abstract

The invention relates to a method for measuring the cooling capacity of a mechanical ventilation cooling tower group, which comprises the following steps of: acquiring the measured values of test parameters of the cooling tower group, and calculating the cooling capacity of cooling towers according to a cooling capacity formula; wherein the test parameters of the cooling tower group comprise atmospheric pressure, ambient air dry-bulb temperature, ambient air wet-bulb temperature, cooling tower group inlet air dry-bulb temperature, cooling tower group inlet air relative humidity, cooling tower group inlet water quantity, cooling tower group inlet water temperature, cooling tower group outlet water temperature, cooling tower group outlet air temperature and cooling tower group ventilation quantity. The test parameters of the cooling tower group are collected by taking the cooling tower group as a whole, and then the cooling capacity of the cooling tower group is measured, so that the situation of inaccurate measurement caused by the influence of the tower group effect on a single cooling tower can be avoided, and online real-time monitoring of the cooling capacity of the cooling tower group is realized.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and in particular relates to a method for measuring the cooling capacity of a mechanical ventilation cooling tower group. Background Art

[0002] In order to accelerate the pace of reducing carbon emissions and improve the global competitiveness of the industry and economy, it is increasingly important for refining enterprises to save energy and reduce consumption and save costs. The energy consumption of the water system in refining enterprises accounts for about 15% of the enterprise's energy consumption, and the energy consumption of the circulating water system accounts for about 70% of the energy consumption of the water system. The cooling tower fan and circulating water pump are the most important energy-consuming equipment in the circulating water system. The cooling capacity of the cooling tower determines the amount of circulating water in the circulating water system, and then determines the power of the circulating water pump. Therefore, the cooling tower is the core of the circulating water system to achieve energy conservation and consumption reduction.

[0003] At present, most of the cooling towers in the circulating water field of refineries are mechanical draft cooling towers, and most of them are 2-10 mechanical draft cooling towers arranged side by side as a cooling tower group. Due to the existence of the tower group effect, the measurement results of a single tower are always different from those of the tower group. If the measurement results of a single tower are directly used to replace the measurement results of the tower group, it will lead to excessive energy consumption of the tower group, excessive operating costs of the tower group, and untimely maintenance of the tower group. Therefore, it is necessary to accurately test the thermal performance of the existing cooling tower group. Summary of the invention

[0004] The object of the present invention is to provide a method for measuring the cooling capacity of a mechanical ventilation cooling tower group so as to accurately detect the thermal performance of the cooling tower group.

[0005] In order to achieve the above object, a first aspect of the present invention provides a method for determining the cooling capacity of a mechanical ventilation cooling tower group, the method comprising the following steps:

[0006] Collect the measured values ​​of the test parameters of the cooling tower group and calculate the cooling capacity of the cooling tower according to the cooling capacity formula;

[0007] The test parameters of the cooling tower group include atmospheric pressure, ambient air dry bulb temperature, ambient air wet bulb temperature, cooling tower group inlet air dry bulb temperature, cooling tower group inlet air relative humidity, cooling tower group inlet water volume, cooling tower group inlet water temperature, cooling tower group outlet water temperature, cooling tower group outlet air temperature, cooling tower group ventilation volume;

[0008] The dry bulb temperature of the air entering the cooling tower group and the relative humidity of the air entering the cooling tower group are respectively the weighted average values ​​of the dry bulb temperature and relative humidity of the air at the air inlet of each single cooling tower duct, with the air volume of the single cooling tower duct as the weight;

[0009] The air temperature at the outlet of the cooling tower group is the weighted average of the air temperatures at the air outlets of the air ducts of each single cooling tower, with the air volume of the air duct of the single cooling tower as the weight;

[0010] The ventilation volume of the cooling tower group is the sum of the ventilation volumes of the fans in the cooling tower group.

[0011] Optionally, the cooling capacity formula is calculated according to formula (1):

[0012]

[0013] Where: η——cooling capacity of cooling tower, %;

[0014] G t ——Measured air mass flow rate into the tower, kg / h;

[0015] Q d ——Designed cooling water flow rate, kg / h;

[0016] λ c ——Gas-water ratio corrected to the design operating conditions;

[0017] Q c ——Corrected to the cooling water flow rate into the tower under design conditions, kg / h.

[0018] Optionally, the method for calculating the ventilation volume of each fan in the cooling tower group includes the following steps:

[0019] S1, obtain the operating current and voltage of each fan in the cooling tower group, and calculate the measured fan shaft power according to formula (2);

[0020]

[0021] Where: N t ——Measured fan shaft power, kW;

[0022] U——measured voltage, V;

[0023] I——measured current, A;

[0024] Cosφ——motor power factor;

[0025] η——motor working efficiency;

[0026] S2, then calculate the ventilation volume of each fan according to formula (3);

[0027]

[0028] Where: G t , G d ——Measured and designed mass flow rate of dry air entering the tower, kg / h;

[0029] ν t , ν d ——Measured and designed specific volume of dry air, m 3 / kg;

[0030] N d ——Designed fan shaft power, kW;

[0031] ρ t , d ——Measured and designed air density at the tower inlet, kg / m 3 .

[0032] Optionally, the thermal performance curve and the operating characteristic curve of the cooling tower group are consistent with the thermal performance curve and the operating characteristic curve of a single cooling tower in the cooling tower group.

[0033] Optionally, the water volume entering the cooling tower group is collected at the return water main of the cooling tower group; the collection location of the water temperature entering the cooling tower group is located at the return water main of the cooling tower group; the collection location of the water temperature leaving the cooling tower group is located at the water supply main of the cooling tower group.

[0034] Optionally, the collection positions of the dry-bulb temperature and relative humidity of the air at the air inlet of the wind duct of a single-room cooling tower are located at both ends of the air inlet of the wind duct of the single-room cooling tower; preferably, the collection positions of the dry-bulb temperature and relative humidity of the air at the air inlet of the wind duct of the single-room cooling tower are no more than 2.0m away from the air inlet of the wind duct of the single-room cooling tower, and are 1.5-2.0m away from the top of the water pool; at least one temperature probe is arranged on both sides of the air inlet of each wind duct of the single-room cooling tower.

[0035] Optionally, the air temperature at the air outlet of the single-room cooling tower duct is collected at the air outlet of the single-room cooling tower duct; at least one temperature probe is provided at the air outlet of the single-room cooling tower duct.

[0036] Optionally, the collection location of the atmospheric pressure, the ambient air dry-bulb temperature and the ambient air wet-bulb temperature is located upwind of the cooling tower group; the collection location of the atmospheric pressure, the ambient air dry-bulb temperature and the ambient air wet-bulb temperature is 30-50m away from the cooling tower group and 1.5-2.0m above the ground.

[0037] Optionally, the location for collecting ambient wind speed and wind direction is located upwind of the cooling tower group; the distance between the location for collecting ambient wind speed and wind direction and the cooling tower group is 30-50m, and the height from the ground is 1.5-2.0m.

[0038] A second aspect of the present invention provides a real-time determination method for the cooling capacity of a cooling tower group, the determination method comprising the following steps:

[0039] Compile a computing program according to the determination method provided in the first aspect of the present invention;

[0040] The collection module collects the working values ​​of the cooling tower group and transmits the working values ​​to the control module;

[0041] The control module is loaded into the calculation program, and the control module calculates the cooling capacity of the cooling tower group in real time.

[0042] Through the above technical scheme, the present invention collects the test parameters of the cooling tower group by considering the cooling tower group as a whole, and then measures the cooling capacity of the cooling tower group. This can avoid inaccurate measurements caused by the influence of the tower group effect on a single cooling tower, and realize online real-time monitoring of the cooling capacity of the cooling tower group.

[0043] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention. In the accompanying drawings:

[0045] Figure 1 Corrected air-water ratio calculation diagram for cooling tower groups.

[0046] Figure 2 Corrected air-water ratio calculation diagram for a single-chamber cooling tower.

[0047] Among them, the working characteristic curve and design thermal performance curve of the cooling tower group are consistent with the working characteristic curve and design thermal performance curve of the single cooling tower. The main difference is that the cooling tower group and the single cooling tower respectively calculate the corresponding air-water ratio and cooling number through the corresponding measured working conditions, and obtain the corresponding thermal performance curve of the measured working conditions by translating the thermal performance curve. DETAILED DESCRIPTION

[0048] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0049] Due to the tower group effect, the external environment of a single cooling tower is affected by other cooling tower groups and changes. Therefore, the performance of a single cooling tower cannot represent the performance of each cooling tower in the cooling tower group. However, the thermal performance test of the cooling tower is carried out by a special testing team. If the thermal performance of each cooling tower in the cooling tower group is tested, a large amount of thermal resources will be consumed. Therefore, the present invention adds an appropriate number of cooling tower thermal performance testing equipment based on the existing online detection equipment of the refining enterprise, and provides a measurement method that can accurately detect the cooling capacity of a mechanical ventilation cooling tower group.

[0050] A first aspect of the present invention provides a method for determining the cooling capacity of a mechanical ventilation cooling tower group, the method comprising the following steps:

[0051] Collect the measured values ​​of the test parameters of the cooling tower group and calculate the cooling capacity of the cooling tower according to the cooling capacity formula;

[0052] The test parameters of the cooling tower group include atmospheric pressure, ambient air dry bulb temperature, ambient air wet bulb temperature, cooling tower group inlet air dry bulb temperature, cooling tower group inlet air relative humidity, cooling tower group inlet water volume, cooling tower group inlet water temperature, cooling tower group outlet water temperature, cooling tower group outlet air temperature, cooling tower group ventilation volume;

[0053] The dry bulb temperature of the air entering the cooling tower group and the relative humidity of the air entering the cooling tower group are respectively the weighted average values ​​of the dry bulb temperature and relative humidity of the air at the air inlet of each single cooling tower duct, with the air volume of the single cooling tower duct as the weight;

[0054] The air temperature at the outlet of the cooling tower group is the weighted average of the air temperatures at the air outlets of the air ducts of each single cooling tower, with the air volume of the air duct of the single cooling tower as the weight;

[0055] The ventilation volume of the cooling tower group is the sum of the ventilation volumes of the fans in the cooling tower group.

[0056] The technical solution of the present invention eliminates the influence between the single cooling towers in the cooling tower group by considering the cooling tower group as a whole, and avoids the problem of inaccurate cooling capacity measurement caused by the influence of the tower group effect on the single cooling tower. At the same time, the present invention is based on the fact that most water management units manage the circulating water field in the form of a cooling tower group. By performing real-time detection of the cooling capacity of the cooling tower group, the water management personnel can meet the needs of macro-management of the circulating water field cooling towers in the first place.

[0057] The cooling capacity formula is calculated according to formula (1):

[0058]

[0059] Where: η——cooling capacity of cooling tower, %;

[0060] G t ——Measured air mass flow rate into the tower, kg / h;

[0061] Q d ——Designed cooling water flow rate, kg / h;

[0062] λ c ——Gas-water ratio corrected to the design operating conditions;

[0063] Q c ——Corrected to the cooling water flow rate into the tower under design conditions, kg / h.

[0064] According to the above formula, under the condition of known design cooling water flow, it is also necessary to provide the actual measured ventilation volume of the cooling tower group and the air-water ratio λ corrected to the design condition. c The cooling capacity can be calculated.

[0065] Among them, the gas-water ratio λ corrected to the design condition c The calculation steps are as follows:

[0066] 1. According to the actual measured water flow rate of the cooling tower group O t The measured air volume G of the cooling tower group t According to formula (9), the measured gas-water ratio λ is calculated t ;

[0067] 2. Calculate the cooling number N of the measured working condition according to the measured gas-water ratio and the measured working condition parameters according to formula (10);

[0068] 3. The measured gas-water ratio λ t The cooling number N is marked in the calculation diagram of the corrected air-water ratio of the cooling tower group, and then the thermal performance curve of the cooling tower group is translated through this point to obtain the thermal performance curve under the measured working conditions. The air-water ratio corresponding to the intersection of the translated thermal performance curve and the working characteristic curve of the cooling tower group is the air-water ratio λ corrected to the design working conditions. c .

[0069] In the present invention, the cooling tower operating characteristic curve is determined by the cooling tower design parameters, including the inlet and outlet water temperature, the inlet air dry-bulb temperature and the atmospheric pressure. The cooling tower design thermal performance curve is determined by the specific cooling tower selection.

[0070] In the present invention, the measured ventilation volume of the cooling tower group can be calculated based on the ventilation volume of each fan in the cooling tower group. Since the cooling tower group is regarded as a whole, specifically, in the present invention, the ventilation volume of the cooling tower group is the sum of the ventilation volumes of each fan in the cooling tower group.

[0071] The method for calculating the ventilation volume of each fan in the cooling tower group includes the following steps:

[0072] S1, obtain the operating current and voltage of each fan in the cooling tower group, and calculate the measured fan shaft power according to formula (2);

[0073]

[0074] Where: N t ——Measured fan shaft power, kW;

[0075] U——measured voltage, V;

[0076] I——measured current, A;

[0077] Cosφ——motor power factor;

[0078] η——motor working efficiency;

[0079] S2, then calculate the ventilation volume of each fan according to formula (3);

[0080]

[0081] Where: G t , G d ——Measured and designed mass flow rate of dry air entering the tower, kg / h;

[0082] ν t , ν d ——Measured and designed specific volume of dry air, m 3 / kg;

[0083] N d ——Designed fan shaft power, kW;

[0084] ρ t , d ——Measured and designed air density at the tower inlet, kg / m 3 .

[0085] Specifically, in some embodiments of the present invention, the thermal performance curve and the operating characteristic curve of the cooling tower group are consistent with the thermal performance curve and the operating characteristic curve of a single cooling tower in the cooling tower group.

[0086] In the above formula, the air specific volume is calculated according to formula (4):

[0087]

[0088] Where: ν——Specific volume of air, m 3 / kg;

[0089] P0——atmospheric pressure, kPa;

[0090] χ——humidity content of air, calculated according to formula (5), kg / kg;

[0091] T——absolute air temperature, K.

[0092]

[0093] Where: χ——humidity content of air, kg / kg;

[0094] P0——atmospheric pressure, kPa;

[0095] P θ ″——Water vapor partial pressure of saturated air at dry bulb temperature θ when the air entering the tower is in kPa;

[0096] ——Relative humidity of air entering the tower, %.

[0097] In the present invention, the relative humidity of the air entering the tower is Calculate according to formula (6):

[0098]

[0099] Where: p τ ″——Water vapor partial pressure of saturated air at the wet bulb temperature τ when the air entering the tower is, kPa;

[0100] p′ θ ′——the water vapor partial pressure of saturated air at the dry bulb temperature θ of the inlet air, kPa;

[0101] A——Coefficients of different dry-bulb and wet-bulb thermometers; A=0.0007974 for the house-type Avergust dry-bulb and wet-bulb thermometer; A=0.000662 for the ventilated Assmann dry-bulb and wet-bulb thermometer;

[0102] P0——atmospheric pressure, kPa;

[0103] θ——dry bulb temperature, °C;

[0104] τ——wet bulb temperature, ℃.

[0105] In the present invention, the saturated water vapor partial pressure is calculated according to formula (7) at 0°C to 100°C:

[0106]

[0107] Where: p″——vapor partial pressure of saturated air, kPa;

[0108] t——temperature, ℃.

[0109] In the present invention, the inlet air density is calculated according to formula (8):

[0110]

[0111] Where: ρ1——density of dry air entering the tower, kg / m 3 ;

[0112] ——Relative humidity of air entering the tower, %;

[0113] p′ θ ′——the water vapor partial pressure of saturated air at the dry bulb temperature θ of the inlet air, kPa;

[0114] P0——atmospheric pressure, kPa;

[0115] θ——dry bulb temperature, ℃.

[0116] In the present invention, the single-room cooling towers in the cooling tower group can be arranged side by side in a straight line or in a quadrilateral arrangement.

[0117] The water volume of the cooling tower group is collected at the return water main of the cooling tower group. Specifically, an ultrasonic flowmeter or a solenoid valve flowmeter can be used to collect the flow of the cooling tower group, and the data can be automatically recorded by an automatic recorder. Most of the circulating water fields of refineries use the above method to measure the total circulation volume of the return water main, and the data can be directly read according to the real-time display of the central control system.

[0118] Wherein, the collection location of the water temperature entering the cooling tower group is located at the return water main of the cooling tower group.

[0119] The location for collecting the outlet water temperature of the cooling tower group is located at the water supply main of the cooling tower group.

[0120] In some specific embodiments of the present invention, a temperature probe is used to collect the water temperature of the cooling tower group entering the cooling tower and the water temperature of the cooling tower group leaving the cooling tower. Specifically, the temperature probe is installed in a protective sleeve, and a small amount of oil exists in the sleeve to submerge the temperature sensing element.

[0121] Among them, the collection positions of the air dry bulb temperature and relative humidity at the air inlet of the single-room cooling tower duct are located at both ends of the air inlet of the single-room cooling tower duct.

[0122] Preferably, the collection position of the air dry-bulb temperature and relative humidity at the air inlet of the single-room cooling tower duct is no more than 2.0m away from the air inlet of the single-room cooling tower duct, and is 1.5-2.0m away from the top of the water pool.

[0123] Specifically, the relative humidity of the air entering the tower and the dry-bulb temperature of the air at the air inlet of the single-room cooling tower duct are collected through electronic temperature and humidity probes. At least one temperature probe is set on both sides of the air inlet of each air duct of the single-room cooling tower. For example, when the cooling tower is a mechanical ventilation cooling tower with double-sided air intake, the cooling tower is arranged with two air duct inlets for air intake, and one temperature probe is set on both sides of each air duct inlet, then each cooling tower is provided with 4 temperature probes.

[0124] In a specific embodiment of the present invention, for a rectangular cooling tower with single-sided and double-sided air inlet, when the air inlet height is not more than 4.0m and the width is not more than 6.0m, a detection point is set at 1 / 2 of the width of the air inlet on each side. The distance between the detection point and the air inlet louver is within 2.0m. The temperature probe is installed 1.5m-2.0m from the upper edge of the water collection tank. When the air inlet height is greater than 4.0m and the width is greater than 6.0m, a detection point is set at 1 / 4 and 3 / 4 of the width and height of the air inlet on each side. The distance between the detection point and the air inlet louver is 2.0m-3.0m.

[0125] Wherein, the air temperature at the air outlet of the single-room cooling tower duct is collected at the air outlet of the single-room cooling tower duct; at least one temperature probe is arranged at the air outlet of the single-room cooling tower duct.

[0126] The atmospheric pressure, the ambient air dry-bulb temperature and the ambient air wet-bulb temperature are collected at a location upwind of the cooling tower group. Specifically, the ambient air dry-bulb and wet-bulb temperatures are collected by arranging mechanical ventilation dry-bulb and wet-bulb thermometers upwind of the cooling tower group. In a specific embodiment of the present invention, the atmospheric pressure, the ambient air dry-bulb temperature and the ambient air wet-bulb temperature are collected at a distance of 30-50 m from the cooling tower group and at a height of 1.5-2.0 m from the ground.

[0127] In the present invention, the environmental wind speed and wind direction parameters are collected by arranging an electronic three-cup anemometer. Specifically, the collection position of the environmental wind speed and wind direction is located upwind of the cooling tower or the cooling tower group. The distance between the collection position of the environmental wind speed and wind direction and the cooling tower group is 30-50m, and the height from the ground is 1.5-2.0m. It should be noted that the distance between the collection position of the environmental wind speed and wind direction and the cooling tower group refers to the distance between the collection position and the edge of the cooling tower group.

[0128] It should be noted that the measured values ​​of the above test parameters can be recorded regularly by an automatic recorder and transmitted to the control module.

[0129] The measured gas-water ratio is calculated according to formula (9):

[0130]

[0131] Where: λ——measured gas-water ratio;

[0132] G——Cooling tower group ventilation volume, m 3 / kg;

[0133] Q——Cooling water volume of cooling tower group, kg / h;

[0134] ρ1——density of air entering the tower, kg / m 3 .

[0135] In the present invention, the cooling tower in the cooling tower group is a counter-flow cooling tower, wherein the measured cooling number of the counter-flow cooling tower is calculated according to formula (10):

[0136]

[0137] Where: N——measured cooling number;

[0138] h″——saturated air enthalpy, kJ / kg;

[0139] h——air enthalpy, kJ / kg;

[0140] t1——water temperature entering the tower, ℃.

[0141] The right side of the above formula can be solved by Simpson's approximate integration method or other methods, that is,

[0142]

[0143] Where:

[0144] Δt——cooling water temperature difference, °C;

[0145] C W ——Specific heat of water is 4.187 kJ / (kg·℃);

[0146] h″ c1 ——Saturated air enthalpy under the condition of outlet water temperature t2+0.1Δt, kJ / kg(DA);

[0147] h G1 ——The corrected specific enthalpy of air at the first point, calculated according to formula (11), kJ / kg(DA);

[0148] h″ c2 ——Saturated air enthalpy at the outlet water temperature t2+0.4Δt, kJ / kg(DA);

[0149] h G2 ——The corrected specific enthalpy of air at the second point, calculated according to equation (12), kJ / kg(DA);

[0150] h″ c3 ——Saturated air enthalpy under the condition of inlet water temperature t1-0.4Δt, kJ / kg(DA);

[0151] h G3 ——The corrected specific enthalpy of air at the third point, calculated according to equation (13), kJ / kg(DA);

[0152] h″ c4 ——Saturated air enthalpy under the condition of inlet water temperature t1-0.1Δt, kJ / kg(DA);

[0153] h G4 ——The corrected specific enthalpy of air at the fourth point, calculated according to formula (14), kJ / kg (DA).

[0154] h G1 =h1+0.1ΔtC W / λ (11)

[0155] h G2 =h1+0.4ΔtC W / λ (12)

[0156] h G3 =h2-0.4ΔtC W / λ (13)

[0157] h G4 =h2-0.1ΔtC W / λ (14)

[0158] When the temperature difference between the water inlet and outlet (t1-t2) is less than 15°C, the water temperature t1 to t2 can be solved according to equations (15) and (16):

[0159]

[0160]

[0161] Where: Δt——cooling water temperature difference, °C;

[0162] h m ——The average value of the specific enthalpy of the wet air entering and leaving the tower, kJ / kg (DA);

[0163] h″1——enthalpy of saturated air at a temperature equivalent to the inlet water temperature t1, kJ / kg (DA);

[0164] h″2——enthalpy of saturated air at a temperature equivalent to the outlet water temperature t2, kJ / kg (DA);

[0165] h″ m ——with the average water temperature in and out of the tower tm The corresponding saturated air enthalpy, kJ / kg(DA);

[0166] The enthalpy of air entering and leaving the tower is calculated according to formula (17):

[0167]

[0168] Where: h1 – enthalpy of air entering the tower, kJ / kg.

[0169] The enthalpy of the air out of the tower is calculated according to formula (18):

[0170]

[0171] Where: h2——the enthalpy of air out of the tower, kJ / kg;

[0172] C W ——The specific heat capacity of water is 4.187 kJ / (kg·℃);

[0173] k——heat coefficient taken away by evaporating water, calculated according to formula (19):

[0174]

[0175] t2——water temperature out of the tower, ℃.

[0176] When the temperature is t, the saturated air enthalpy is calculated according to formula (20):

[0177]

[0178] Where: h″——saturated air enthalpy at temperature t, kJ / kg;

[0179] p t ″——Water vapor partial pressure of saturated air at temperature t, kPa.

[0180] When the cooling tower in the cooling tower group is a cross-flow cooling tower, the cooling number of the cross-flow cooling tower is solved according to formula (21):

[0181]

[0182] Where: N h ——Cooling number of cross-flow cooling tower;

[0183] N n - cooling number calculated by the countercurrent cooling tower method;

[0184] F——Correction coefficient; calculated according to formula (22)

[0185]

[0186] Where: h1——air enthalpy when the water temperature entering the tower is t1, kJ / kg(DA);

[0187] h2——saturated air enthalpy when the outlet water temperature is t2, kJ / kg (DA);

[0188] h1″——saturated air enthalpy when the inlet water temperature is t1, kJ / kg(DA);

[0189] h2″——saturated air enthalpy when the outlet water temperature is t2, kJ / kg(DA);

[0190] It should be noted that when the measured cooling tower group inlet water temperature is not equal to the design water temperature, and the temperature difference is greater than ±2°C, the measured cooling number is corrected for water temperature according to formula (23);

[0191]

[0192] Where: N——measured cooling number;

[0193] N x ——Correct the cooling number;

[0194] t tl ,t dl ——The measured inlet water temperature of cooling tower group and the designed inlet water temperature of cooling tower group, ℃.

[0195] After the modified cooling number is calculated according to the above formula, the air-water ratio λ corrected to the design condition is calculated on the modified air-water ratio calculation chart according to the measured air-water ratio, the modified cooling number, the thermal performance curve and the working characteristic curve of the cooling tower group. c .

[0196] The air-water ratio λ corrected to the design condition is calculated. c Finally, the measured cooling capacity of the cooling tower group is obtained according to the cooling capacity calculation.

[0197] A second aspect of the present invention provides a real-time determination method for the cooling capacity of a cooling tower group, the determination method comprising the following steps:

[0198] Compile a computing program according to the determination method provided in the first aspect of the present invention;

[0199] The collection module collects the working values ​​of the cooling tower group and transmits the working values ​​to the control module;

[0200] The control module is loaded into the calculation program, and the control module calculates the cooling capacity of the cooling tower group in real time.

[0201] The present invention is further described in detail below by way of examples, but the present invention is not limited to the following examples.

[0202] Example 1

[0203] A cooling tower group of a circulating water field consists of 5 4500m 3 / h counter-current two-side air inlet mechanical ventilation cooling towers are arranged side by side. Among them, the data of cooling tower group inlet water volume, cooling tower group inlet water temperature, cooling tower group outlet water temperature, and fan voltage and fan current of each fan in the cooling tower group are obtained from the central control system.

[0204] The ventilation volume of the cooling tower group is the sum of the ventilation volumes of each fan in the cooling tower group. The fan ventilation volume is calculated by reading the operating voltage and operating current of each fan in the five cooling towers and using the above formulas (2) and (3) using the indirect method.

[0205] Atmospheric pressure and ambient air dry-bulb and wet-bulb temperatures are collected and read by mechanical ventilation dry-bulb and wet-bulb thermometers. The collection location of atmospheric pressure and ambient air dry-bulb and wet-bulb temperatures is located upwind of the cooling tower group, and the collection location is more than 30m away from the cooling tower group and 1.5m above the ground.

[0206] The air inlet temperature of the cooling tower group and the relative humidity of the cooling tower group are the weighted average values ​​of the dry-bulb temperature and relative humidity of the air at the air inlet of each single cooling tower duct with the air volume of the single cooling tower duct as the weight; the dry-bulb temperature and relative humidity of the air at the air inlet of the cooling tower duct are collected and read by 20 temperature and humidity probes installed on both sides of the air inlet of the cooling tower duct. The temperature and humidity probes are 2m away from the air inlet and 1.5m away from the top of the water pool.

[0207] The air temperature at the cooling tower group outlet is the weighted average of the air temperature at the air outlet of each single cooling tower duct, with the air volume of the single cooling tower duct as the weight. The air temperature at the air outlet of the cooling tower duct is read by 5 temperature measuring probes set under the cooling tower duct blades.

[0208] The data collected on-site, design parameters and actual operating parameters of the cooling tower group are shown in Table 1.

[0209] Table 1

[0210] Test Parameters Design conditions Actual test conditions Atmospheric pressure / kPa 100.87 101.0 Ambient air dry bulb temperature / ℃ / 27.0 Ambient air wet bulb temperature / ℃ / 24.5 Inlet air dry bulb temperature / ℃ 33.1 26.1 Wet bulb temperature of air entering the tower / ℃ 28.5 24.2 Relative humidity of air entering the tower / % 70.9 85.0 <![CDATA[Water inflow into the tower / (m 3 / h)]]> 22500 17000 Inlet water temperature / ℃ 43 31.36 Outlet water temperature / ℃ 33 26.69 Outlet air temperature / ℃ / 29.90 Fan voltage / V 10000 10220 Fan current / A 14.7 13.4 Fan shaft power / kW 200 186.0 <![CDATA[Ventilation volume / (m 3 / h)]]> 14500000 14519148 Gas-water ratio / 0.975 Calculate Cooling Number / 1.692 Corrected cooldown number / 1.491 Corrected gas-water ratio / 0.799 Thermal performance / % / 92.2

[0211] The measured fan shaft power is obtained based on the measured operating voltage and operating current of the fan:

[0212]

[0213] The actual air flow rate into the single cooling tower:

[0214] The ventilation volume of cooling tower group is:

[0215] Measured gas-water ratio:

[0216] Measured cooling number:

[0217] Since the measured water temperature entering the tower is not equal to the designed water temperature, and the temperature difference is greater than ±2℃, water temperature correction is performed to obtain the corrected cooling number N tx1 :

[0218]

[0219] Figure 1 The calculation diagram of the corrected air-water ratio of the cooling tower group is shown in Figure 1, where I is the thermal performance curve of the cooling tower group, and II is the working characteristic curve of the cooling tower group. The curve I is translated through the points of the measured air-water ratio and the corrected cooling number to obtain the parallel line III. The air-water ratio corresponding to the intersection of the parallel line III and the working characteristic curve II is the corrected air-water ratio, that is, the air-water ratio λ c1 =0.799.

[0220] Then calculate the cooling capacity of the cooling tower group in this embodiment:

[0221]

[0222] The specific thermal performance calculation results are shown in Table 1.

[0223] Evaluation: The measured cooling capacity of the cooling tower group reaches 92.2% of the designed cooling capacity.

[0224] Comparative Example 1

[0225] A cooling tower group of a circulating water field consists of 5 4500m 3 / h counter-current two-side air inlet mechanical ventilation cooling towers are arranged side by side. In this comparative example, one of the cooling towers is selected for testing.

[0226] Among them, the atmospheric pressure and the dry-bulb and wet-bulb temperatures of the ambient air are collected and read by mechanical ventilation dry-bulb and wet-bulb thermometers. The collection position of the atmospheric pressure and the dry-bulb and wet-bulb temperatures of the ambient air is located upwind of the cooling tower, and the collection position is more than 30m away from the cooling tower and 1.5m above the ground.

[0227] The air temperature and humidity entering the cooling tower are collected and read by four temperature and humidity probes installed on both sides of the air inlet of the cooling tower wind duct. The temperature and humidity probes are 2m away from the air inlet and 1.5m away from the top of the water pool.

[0228] The water flow rate entering the tower is measured by installing an ultrasonic flow meter at 2 / 3 of the return pipe riser.

[0229] The water temperature entering the tower is measured by a temperature probe at the sampling port of the return pipe.

[0230] The outflow water temperature is measured by moving a floating basin to comprehensively measure the water temperatures of four water pools, and the arithmetic average of the water temperatures of the four water pools is taken as the outflow water temperature.

[0231] The air temperature out of the tower is read by arranging 5 temperature probes under the wind tube blades.

[0232] The ventilation volume of a single cooling tower is calculated by reading the fan operating voltage and current data and using the above formulas (2) and (3) using the indirect method.

[0233] The data collected on-site, design parameters and actual operating parameters of the cooling tower are shown in Table 2.

[0234] Table 2

[0235]

[0236]

[0237] The measured fan shaft power is obtained based on the measured operating voltage and operating current of the fan:

[0238]

[0239] The actual air flow rate into the single cooling tower:

[0240] The ventilation volume of cooling tower group: G t2 =G t

[0241] Measured gas-water ratio:

[0242] Measured cooling number:

[0243] Since the measured water temperature entering the tower is not equal to the designed water temperature, and the temperature difference is greater than ±2℃, water temperature correction is performed to obtain the corrected cooling number N tx2 .

[0244]

[0245] Figure 2 The calculation diagram of the corrected air-water ratio of a single cooling tower is shown in Figure 1, where Ⅰ is the thermal performance curve of the cooling tower, and Ⅱ is the working characteristic curve of the cooling tower. The curve Ⅰ is translated through the points of the measured air-water ratio and the corrected cooling number to obtain the parallel line Ⅲ. The air-water ratio corresponding to the intersection of the line Ⅲ and the working characteristic curve Ⅱ is the corrected air-water ratio, that is, the air-water ratio λ c2 =0.773.

[0246] Then calculate the cooling capacity of the cooling tower group in this embodiment:

[0247]

[0248] The specific thermal performance calculation results are shown in Table 2.

[0249] Evaluation: The measured cooling capacity of the cooling tower group reaches 95.3% of the designed cooling capacity.

[0250] According to the above data, the measured cooling capacity of the cooling tower group in Example 1 is 92.2% of the designed cooling capacity, and when the cooling capacity of one of the cooling towers is measured, the measured cooling capacity is 95.3% of the designed cooling capacity, that is, the measured cooling capacity of the cooling tower group is lower than the measured cooling capacity of a single cooling tower.

[0251] The present invention calculates the measured cooling capacity of the cooling tower group by considering the cooling tower group as a whole, thereby avoiding the problem of inaccurate detection of the tower group effect of a single cooling tower in the cooling tower group, and making the detection of the thermal performance of the cooling tower group more accurate. At the same time, by monitoring the measured cooling capacity of the cooling tower group, it is possible to avoid the problems of excessive energy consumption of the tower group, excessive operating cost of the tower group, and untimely maintenance of the tower group caused by directly replacing the measurement results of the tower group with the measurement results of a single tower, which is conducive to the refined management of the cooling tower group.

[0252] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0253] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0254] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for determining the cooling capacity of a mechanical ventilation cooling tower group, characterized in that: The determination method comprises the following steps: Collect the measured values ​​of the test parameters of the cooling tower group and calculate the cooling capacity of the cooling tower according to the cooling capacity formula; The test parameters of the cooling tower group include atmospheric pressure, ambient air dry bulb temperature, ambient air wet bulb temperature, cooling tower group inlet air dry bulb temperature, cooling tower group inlet air relative humidity, cooling tower group inlet water volume, cooling tower group inlet water temperature, cooling tower group outlet water temperature, cooling tower group outlet air temperature, cooling tower group ventilation volume; The dry bulb temperature of the air entering the cooling tower group and the relative humidity of the air entering the cooling tower group are respectively the weighted average values ​​of the dry bulb temperature and relative humidity of the air at the air inlet of each single cooling tower duct, with the air volume of the single cooling tower duct as the weight; The air temperature at the outlet of the cooling tower group is the weighted average of the air temperatures at the air outlets of the air ducts of each single cooling tower, with the air volume of the air duct of the single cooling tower as the weight; The ventilation volume of the cooling tower group is the sum of the ventilation volumes of the fans in the cooling tower group.

2. The assay method according to claim 1, wherein The cooling capacity formula is calculated according to formula (1): Where: η——cooling capacity of cooling tower, %; G t ——Measured air mass flow rate into the tower, kg / h; Q d ——Designed cooling water flow rate, kg / h; λ c ——Gas-water ratio corrected to the design operating conditions; Q c ——Corrected to the cooling water flow rate into the tower under design conditions, kg / h.

3. The measuring method according to claim 1, wherein The method for calculating the ventilation rate of each fan in the cooling tower group comprises the following steps: S1, obtain the operating current and voltage of each fan in the cooling tower group, and calculate the measured fan shaft power according to formula (2); Where: N t ——Measured fan shaft power, kW; U——measured voltage, V; I——measured current, A; Cosφ——motor power factor; η——motor working efficiency; S2, then calculate the ventilation volume of each fan according to formula (3); Where: G t , G d ——Measured and designed mass flow rate of dry air entering the tower, kg / h; ν t , ν d ——Measured and designed specific volume of dry air, m 3 / kg; N d ——Designed fan shaft power, kW; ρ t , d ——Measured and designed air density at the tower inlet, kg / m 3 .

4. The assay method according to claim 1, wherein The thermal performance curve and the operating characteristic curve of the cooling tower group are consistent with the thermal performance curve and the operating characteristic curve of a single cooling tower in the cooling tower group.

5. The assay method according to claim 1, wherein The water volume of the cooling tower group inlet is collected at the return water main of the cooling tower group; The collection location of the cooling tower group inlet water temperature is located at the return water main of the cooling tower group; The location for collecting the outlet water temperature of the cooling tower group is located at the water supply main of the cooling tower group.

6. The assay method according to claim 1, wherein The collection positions of the air dry bulb temperature and relative humidity at the air inlet of the single-room cooling tower duct are located at both ends of the air inlet of the single-room cooling tower duct; Preferably, the distance between the collection position of the air dry bulb temperature and relative humidity at the air inlet of the single cooling tower duct and the air inlet of the single cooling tower duct is no more than 2.0m, and the distance from the top of the water pool is 1.5-2.0m; At least one temperature probe is installed on both sides of the air inlet of each air duct of a single-room cooling tower.

7. The measuring method according to claim 1, wherein The air temperature at the air outlet of the single-chamber cooling tower is collected at the air outlet of the single-chamber cooling tower; At least one temperature probe is arranged at the air outlet of the air duct of the single-room cooling tower.

8. The assay method according to claim 1, wherein The collection location of the atmospheric pressure, the ambient air dry-bulb temperature and the ambient air wet-bulb temperature is located upwind of the cooling tower group; The distance between the atmospheric pressure, the ambient air dry-bulb temperature and the ambient air wet-bulb temperature and the cooling tower group is 30-50 m, and the height from the ground is 1.5-2.0 m.

9. The assay method according to claim 1, wherein The location for collecting ambient wind speed and wind direction is located upwind of the cooling tower group; the distance between the location for collecting ambient wind speed and wind direction and the cooling tower group is 30-50m, and the height from the ground is 1.5-2.0m.

10. A method for real-time determination of cooling capacity of a cooling tower group, characterized in that: The determination method The following steps are involved: Compiling a computing program according to the method according to any one of claims 1 to 9; The collection module collects the working values ​​of the cooling tower group and transmits the working values ​​to the control module; The control module is loaded into the calculation program, and the control module calculates the cooling capacity of the cooling tower group in real time.

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