Standard No.:	DL/T 5545-2018
English Name:	Code for design of indirect dry cooling system for fossil-fired power plant
Chinese Name:	火力发电厂间接空冷系统设计规范
Professional Classification:	DL    Professional Standard - Electricity
Issued by:	NEA
Issued on:	2018-06-06
Implemented on:	2018-10-1
Status:	valid
Language:	English
File Format:	PDF
Word Count:	25000 words
Price(USD):	600.0
Delivery:	via email in 1 business day

Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative. Pursuant to the requirements of Notice of the National Energy Administration on issuing the plan 2014 for development (revision) of the first batch of professional standards in energy sector (NEA S&T [2014] No.298), the code development group has prepared this Code through extensive investigation, careful conclusion from indirect dry cooling system design experience, and wide consultation. The main technical contents of this Code are as follows: general provisions, terms, basic requirements, meteorological parameter selection requirements of indirect dry cooling system, general layout of indirect dry cooling system, design parameter selection and calculation of indirect dry cooling system, indirect dry cooling process system and equipment, indirect dry cooling tower structure, operation and control requirements of indirect dry cooling system and test requirements of indirect dry cooling system. Code for design of indirect dry cooling system for fossil-fired power plant 1 General provisions 1.0.1 This Code is formulated in order to make the design of indirect dry cooling system of fossil-fired power plant meet the requirements for safety, reliability, advanced technology, economy, rationality and environmental protection. 1.0.2 This Code is applicable to the design of indirect dry cooling system of fossil-fired power plants with single unit capacity of 125MW~1,000MW in newly built, renovated and expanded engineerings. 1.0.3 The design of indirect dry cooling system of fossil-fired power plants shall actively adopt advanced technologies, processes, equipment and materials proved by operation practice or industrial test. 1.0.4 The design life of indirect dry cooling process system shall be 30 years, and the design service life of the structure of indirect dry cooling tower shall be 50 years. 1.0.5 The design identification system of indirect dry cooling system shall be consistent with the identification system of the main work of fossil-fired power plant. 1.0.6 In addition to this Code, the design of indirect dry cooling system of fossil-fired power plant shall also comply with those specified in the current relevant standards of the nation. 2 Terms 2.0.1 indirect dry cooling system cooling system indirectly exchanging the exhaust heat of steam turbine with air using air as the final cooling medium and circulating cooling water as the intermediate heat exchange medium, including indirect dry cooling system with surface condenser and indirect dry cooling system with jet condenser   2.0.2 indirect dry cooling system with surface condenser indirect dry cooling system with the heat exchange between exhaust steam of steam turbine and circulating cooling water taking place in surface condenser 2.0.3 indirect dry cooling system with jet condenser indirect dry cooling system with the heat exchange between exhaust steam of steam turbine and circulating cooling water taking place in mixing condenser 2.0.4 cooling column column consisting of several groups of tube bundles and tube sheet cooling elements, with both ends connected with water chambers 2.0.5 louver device for adjusting the air input of an dry cooling radiator, which consists of a frame and louver blades 2.0.6 cooling delta triangular cooling unit composed of two cooling columns with the same length and a group of louvers with the same length 2.0.7 cooling sector functional unit composed of several adjacent cooling deltas, with each operating under the control of a set of inlet valve, outlet valve, vent valve and exhaust device   2.0.8 initial temperature difference (ITD) difference between indirect dry cooling radiator cooling water inlet temperature and radiator inlet air temperature 2.0.9 single flow pass circulating cooling water entering from one end of the cooling column and directly flowing out from the other end of the cooling column without changing its direction 2.0.10 double flow pass circulating cooling water flowing in from one half-side finned tube at one end of the cooling column and turning back to the other half-side finned tube through the water chamber at the other end of the cooling column, and flowing out from the same end of the cooling column as flowing in, with the water flow direction in the finned tube by which the circulating cooling water flows in opposite to that in the finned tube by which the circulating cooling water flows out 2.0.11 natural draught indirect dry cooling tower facility cooling circulating cooling water in an dry cooling radiator by natural convection of air formed by air density difference between inside and outside the cooling tower 2.0.12 mechanical draught indirect dry cooling tower facility cooling circulating cooling water in an dry cooling radiator by forced convection of air formed by a fan 2.0.13 indirect dry cooling tower with flue gas discharge natural draught indirect dry cooling tower with flue gas discharge function as a chimney 2.0.14 widening platform closed structure between the top of the cooling delta and the indirect dry cooling tower body when the cooling deltas are vertically arranged around the tower 2.0.15 design ambient wind velocity average velocity of undisturbed ambient air for a period of 10min at an elevation 10m above the zero-meter ground outside the dry cooling tower 3 Basic requirements 3.0.1 Indirect dry cooling system should adopt natural draught indirect dry cooling tower and, if it is limited by the following conditions and it is verified by technical and economic comparison, may adopt mechanical draught indirect dry cooling tower: 1 It is difficult to arrange natural draught indirect dry cooling tower because of the limited land occupation of the plant site; 2 The temperature is low in winter or it is difficult to prevent freeze for heating unit by adopting natural draught indirect dry cooling tower. 3.0.2 The selection of indirect dry cooling system with surface condenser and indirect dry cooling system with jet condenser shall be determined by technical and economic comparison, comprehensively taking into account factors such as condenser terminal difference, control of circulating cooling water and condensate water quality, system power consumption, design and manufacturing level of mixing condenser and pressure regulating hydraulic turbine. 3.0.3 The exhaust steam cooling facility of steam turbine for auxiliary engine drive should be combined with main engine cooling facilities.   3.0.4 Special anti-freezing measures shall be taken when indirect dry cooling system is adopted in areas where the average temperature in the coldest month is less than or equal to -10℃; reasonable allocation scale and design measures for summer should be adopted if the indirect dry cooling system is used in areas with high temperature in summer; measures to prevent strong winds should be taken if the indirect dry cooling system is used in areas with high ambient wind velocity; the design of strengthening radiator cleaning system should be adopted if the indirect dry cooling system is used in areas with poor ambient air quality, including areas with more floating objects or dust in the air. 3.0.5 For units with single unit capacity of 600MW or above, each unit should be equipped with one natural draught indirect dry cooling tower. 3.0.6 The automation level of indirect dry cooling system shall be consistent with that of unit. 3.0.7 The indirect dry cooling system shall be brought under the monitoring and control of decentralized control system (DCS) of unit. 4 Meteorological parameter selection requirements of indirect dry cooling system 4.0.1 The meteorological data required for the design and design depth of indirect dry cooling system shall meet the relevant requirements of the current professional standard DL/T 5507 Regulation for basic data and depth of the hydraulic design for fossil-fired power plant. 4.0.2 The design air temperature of indirect dry cooling system shall be determined according to the meteorological data of the typical year of the reference meteorological station, and the selection of the typical year shall meet the relevant requirements of the current professional standard DL/T 5158 Technical code for meteorological survey in electric power engineering. 4.0.3 The statistics of accumulated hours of air temperature in typical years shall be arranged in descending order of air temperature from high to low, with the air temperature grading not greater than 2℃. The statistical table of accumulated hours of air temperature in typical years shall include the corresponding hours, accumulated hours and cumulative frequency of air temperatures at all grades.   4.0.4 The ambient wind data of indirect dry cooling system should meet the following requirements: 1 Statistical analysis of wind frequency, average wind velocity and maximum wind velocity of each wind direction in the whole year, every season and every month in recent 10 years; 2 Statistical analysis of the occurrence number, frequency and average wind velocity of each wind direction with wind velocity greater than 3m/s in the whole year and summer in recent 10 years; 3 Statistical analysis of the occurrence number, frequency and average wind velocity of each wind direction in recent 10 years when the ambient air temperature is greater than or equal to 26.0℃ and the average wind velocity for a period of 10min is greater than or equal to 4m/s and 5m/s. 4.0.5 If the altitude of the plant site is inconsistent with that of the meteorological station, the ambient air temperature and atmospheric pressure shall be corrected. 4.0.6 When designing the indirect dry cooling system, the representativeness of the selected reference meteorological station to the plant site shall be analyzed and demonstrated. If the representativeness of the reference meteorological station data to the plant site area cannot be analyzed accurately, an dry cooling meteorological observation station shall be set up in the plant site area for comparative analysis. The relevant technical requirements of the dry cooling meteorological observation station at the plant site shall meet those specified in the current professional standard DL/T 5158 Technical code for meteorological survey in electric power engineering. 4.0.7 For the design of indirect dry cooling system, the temperature inversion distribution data of the plant site area should be collected, and the relevant technical requirements should meet those specified in the current professional standard DL/T 5158 Technical code for meteorological survey in electric power engineering. 4.0.8 For the design of indirect dry cooling system, the ambient air quality near the plant site shall be subjected to the following analysis: 1 In areas with frequent sandstorms, analytic statistics shall be carried out for the season with frequent sandstorms, the longest duration of a sandstorm, the intensity of sandstorms, the dominant wind direction and the maximum wind velocity; 2 It is advisable to analyze the dirty environmental conditions such as dust and plant flocs that may affect the performance of indirect dry cooling radiator. 5 General layout of indirect dry cooling system 5.0.1 The position of indirect dry cooling tower relative to surrounding buildings shall meet the following requirements: 1 It should not be on the downwind side of the summer prevailing wind direction of the direct dry cooling platform; 2 It should not be on the downwind side of the winter prevailing wind direction of the mechanical draught wet cooling tower; 3 It should not be on the downwind side of the whole-year prevailing wind direction of the dust source; 4 It should be far away from the outdoor heat source, and should not be on the downwind side of the summer prevailing wind direction of the outdoor heat source. 5.0.2 If the radiators are horizontally arranged in the tower, the clear distance between the towers shall be calculated according to the distance between the centers of the tower pillars corresponding to the zero-meter elevation; if radiators are vertically arranged around towers, the clear distance between towers shall be calculated according to the distance between the outermost edges of radiators. 5.0.3 The clear distance between adjacent indirect dry cooling towers shall meet the following requirements: 1 For the towers with the radiators arranged horizontally inside, the clear distance between the towers should not be less than 4 times the height of the larger air inlet, and shall not be less than 0.5 times the diameter of the tower pillar center of the larger natural draught indirect dry cooling tower at zero meter; 2 For the towers with the radiators arranged vertically around them, the clear distance between the towers should not be less than 3 times the height of the higher radiator, and shall not be less than 0.5 times the diameter of the pillar center of the natural draught indirect dry cooling tower at zero meter; 3 The clear distance between the mechanical draught indirect dry cooling tower and the natural draught indirect dry cooling tower shall meet the following requirements: 1) If the radiators of the mechanical draught indirect dry cooling tower and the natural draught indirect dry cooling tower are vertically arranged, the clear distance between towers should not be less than 1.5 times of the sum of the heights of radiators of the two towers; 2) If the radiators of mechanical draught indirect dry cooling tower are arranged vertically and those of natural draught indirect dry cooling tower are arranged horizontally, the clear distance between towers should not be less than the sum of 1.5 times the height of radiator of mechanical draught indirect dry cooling tower and 2 times the height of air inlet of natural draught indirect dry cooling tower; 3) If the radiators of mechanical draught indirect dry cooling tower are arranged horizontally and those of natural draught indirect dry cooling tower are arranged vertically, the clear distance between towers should not be less than the sum of 2 times the height of air inlet of mechanical draught indirect dry cooling tower and 1.5 times the height of radiator of natural draught indirect dry cooling tower; 4) If the radiators of the mechanical draught indirect dry cooling tower and the natural draught indirect dry cooling tower are horizontally arranged, the clear distance between towers should not be less than 2 times of the sum of the heights of air inlets of the two towers. 5.0.4 The minimum clear distance between the indirect dry cooling tower and its surrounding buildings (structures) may be determined using the following equation: Lmin≥0.4H＋h (5.0.4) where, Lmin——the minimum clear distance between the indirect dry cooling tower and its surrounding buildings (structures), m; H——the effective height of the outermost air inlet surface of the indirect dry cooling tower, m; h——the effective wind resistance height of buildings (structures) around the indirect dry cooling tower, m. For particularly tall obstacles near the cooling tower, special research shall be conducted to evaluate their adverse effects on the thermal performance of the cooling tower. 5.0.5 If the location of the plant site has height limit requirements for the chimney, or it is proved that it is better in terms of the aspects of technique and economy to adopt the indirect dry cooling tower with flue gas discharge, the indirect dry cooling tower with flue gas discharge may be adopted after it is approved upon the environmental impact assessment. 5.0.6 If the zero-meter elevation difference between the indirect dry cooling towers of two units is greater than 2m, the unit system should be adopted. 5.0.7 The position of indirect dry cooling tower should not be at the lower point of circulating cooling water system. 5.0.8 Facilities that do not affect the heat dissipation performance and safe operation of the indirect dry cooling tower may be set in the indirect dry cooling tower in combination with the requirements of relevant process system layout and general layout. 5.0.9 If facilities with fire protection requirements are placed in the indirect dry cooling tower, fire fighting access and supporting fire fighting facilities shall be set according to the requirements of the current national standard GB 50229 Code for design of fire protection for fossil fuel power plants and substations. 5.0.10 The geometric dimension of the indirect dry cooling tower tube shall meet the thermal performance requirements of the indirect dry cooling tower and shall be determined through technical and economic comparisons in combination with factors such as reasonable structure and convenient construction. If a hyperbolic reinforced concrete tower tube is used, the geometric dimension of indirect dry cooling tower tube should be determined according to Table 5.0.10. Table 5.0.10 Recommended geometric dimensions of shell of hyperbolic indirect dry cooling tower tube Ratio of tower height to tower bottom (±0.00m) diameter Ratio of throat area to shell bottom area Ratio of throat height to tower height Diffusion angle at tower top αt Meridian inclination of shell bottom αD 1.00~1.50 0.40~0.60 0.75~0.85 3°~6° 14°~17° 5.0.11 The flue of natural draught indirect dry cooling tower with flue gas discharge should be arranged between two adjacent cooling sectors, and should be set in combination with the gate of indirect dry cooling tower. 5.0.12 The circulating water pump room of indirect dry cooling system with surface condenser should be arranged close to the indirect dry cooling tower, which may be built separately or jointly according to the number of units; the circulating water pump set of indirect dry cooling system with jet condenser should be arranged close to the steam condenser. 5.0.13 The electronic equipment room should be arranged near the indirect dry cooling tower or main equipment for the indirect dry cooling system.   6 Design parameter selection and calculation of indirect dry cooling system 6.1 General requirements 6.1.1 Each design condition of indirect dry cooling system shall correspond to each design condition of dry cooling steam turbine, and the design and calculation parameters shall be selected based on the parameters of corresponding working conditions of dry cooling steam turbine. 6.1.2 The design conditions of indirect dry cooling system should meet the requirements of back pressure and rating in maximum continue rating working condition of dry cooling steam turbine under the condition of design air temperature. For dry cooling units with the rating in maximum continue rating working condition as the unit plate rating, the calculated back pressure and rating in summer shall be checked according to the calculated air temperature in summer; for dry cooling units with the plate rating determined in accordance with the current national standard GB/T 5578 Fixed power plant turbine specifications, the requirements of back pressure and rating in plate rating working condition of dry cooling steam turbine under the condition of calculated air temperature in summer shall be met. 6.2 Design parameter selection of indirect dry cooling system 6.2.1 The design air temperature shall be calculated based on the hourly dry-bulb temperature of a typical year, and should be determined based on the annual weighted-average of air temperatures above 5℃, and temperatures below 5℃, if any, shall be regarded as 5℃. 6.2.2 The calculated air temperature in summer shall be reasonably determined according to the electric load requirements and characteristics of the generator set in summer, which may be selected from the hourly dry-bulb temperature statistics table of a typical year from the highest to the lowest corresponding ambient temperature for a cumulative period of not more than 200h. 6.2.3 The design ambient wind velocity shall be determined based on the statistical data of the reference meteorological station or the dry cooling meteorological observation station at the plant site, and the design ambient wind velocity should not be less than the maximum monthly average velocity. 6.2.4 The design atmospheric pressure and atmospheric pressure in summer should be determined based on the statistical data of the reference meteorological station or the dry cooling meteorological observation station at the plant site, and the former should be the average atmospheric pressure over the years, while the latter should be the average atmospheric pressure of the hottest month over the years. 6.2.5 The design relative humidity and the relative humidity in summer should be determined based on the statistical data of the reference meteorological station or the dry cooling meteorological observation station at the plant site, and the former should be average relative humidity over the years, while the latter should be the average relative humidity of the hottest month over the years. 6.2.6 The initial temperature difference shall be determined by technical and economic comparison and optimization calculation based on meteorological conditions, main engine selection, plant site layout and other conditions. The design initial temperature difference should be selected within the range of 25℃~35℃. 6.2.7 For power plants equipped with a condensation water refine treatment system, the saturated steam temperature corresponding to the calculated back pressure in summer shall match with the temperature resistance of the anion exchange resin of the condensation water refine treatment system. 6.3 Calculation of indirect dry cooling system 6.3.1 The thermodynamic calculation of the indirect dry cooling system shall meet the following requirements: 1 The heat exchange capacity of the indirect dry cooling radiator shall be calculated using the following equation: Q1=K×S×Ft×tm (6.3.1-1) (6.3.1-2) (6.3.1-3) t1=ts-(TTD)c (6.3.1-4) t2=t1-t (6.3.1-5) (6.3.1-6) where, Q1——the heat exchange capacity of indirect dry cooling radiator, W; K——the total heat transfer coefficient, which is related to the water-side flow velocity and air-side wind velocity of the radiator, with the relational expression provided by the manufacturer or determined by test, [W/(m2·℃)]; S——the heat transfer area of the radiator, m2; Ft——the correction factor of non-countercurrent heat transfer; △tm——the average temperature difference of heat transfer, ℃; ma——the face velocity of mass through radiator, [kg/(s·m2)]; v——the flow velocity at the water side of the radiator, m/s; μ——the dynamic viscosity of air, Pa·s; ts——the saturated steam temperature corresponding to the exhaust steam pressure of steam turbine, ℃; t1——the inlet water temperature of radiator, ℃; t2——the outlet water temperature of radiator, ℃; ∆t——the inlet and outlet temperature difference of circulating cooling water, ℃; θ1——the air temperature at the inlet of the radiator, i.e., the ambient dry-bulb temperature, ℃; θ2——the air temperature at the outlet of radiator, ℃; (TTD)c——the steam condenser terminal difference, ℃; Qk——the heat exhaust of the steam condenser, W; W——the flow rate of circulating cooling water, kg/s; cpw——the specific heat capacity of water, 4187[J/(kg·℃)].   2 The heat exhaust of the steam condenser shall be calculated using the following equation: Qk=Dk(hk-hc)+∑Dki(hki-hci)+Qs (6.3.1-7) where, Qk——the heat exhaust of the steam condenser, W; Dk——the exhaust volume of the steam turbine for main engine, kg/s; hk——the exhaust enthalpy of the steam turbine for main engine, J/kg; hc——the enthalpy of condensation water of main engine, J/kg; Dki——the exhaust volume of steam turbine for each auxiliary engine, kg/s; hki——the exhaust enthalpy of steam turbine for each auxiliary engine, J/kg; hci——the enthalpy of condensation water of each auxiliary engine (j/kg); Qs——the exhaust volume of the drainage, W. 3 The heat absorption of ambient air shall be calculated using the following equation: Q2=∆θ×ma×Sn×cpa (6.3.1-8) where, Q2——the heat absorption of ambient air, W; ∆θ——the temperature rise of the air, ℃; Sn——the windward area of the radiator, m2; cpa——the specific heat of air at constant pressure, [J/(kg·℃)];   6.3.2 The suction force generated by the effective height of the air duct of a natural draught indirect dry cooling tower should be calculated using the following equation: ND=He×g×(ρ1-ρ2) (6.3.2) where, ND——the suction force generated due to the effective height of the air duct of indirect dry cooling tower, Pa; He——the effective draft height of the indirect dry cooling tower, which should be the height difference from the middle of the radiator to the top of the tower if the radiator is arranged vertically, or the height difference between the average value of the top of the radiator and the top of the tower if the radiator is arranged horizontally, m; g——the gravitational acceleration, m/s2; ρ1——the density of cold air outside the indirect dry cooling tower, kg/m3. ρ2——the density of hot air inside the indirect dry cooling tower, kg/m3. 6.3.3 The ventilation resistance at each part of the natural draught indirect dry cooling tower shall be calculated in accordance with the following requirements: 1 The measured data of prototype towers identical or similar to the designed indirect dry cooling tower shall be adopted; 2 If the measured data mentioned above are not available, it may be calculated using the empirical methods specified in 6.3.4 and 6.3.5 of this Code. 6.3.4 The ventilation resistance of natural draught indirect dry cooling tower may be calculated using the following empirical methods: 1 The ventilation resistance of the louver may be calculated using the following equation: (6.3.4-1) where, ∆Pb——the ventilation resistance of the louver, Pa; Cb——the coefficient, which is obtained by test; m——the exponent, which is obtained by test; vb——the face velocity of air flow passing through the louver, m/s. 2 The resistance at the inlet of the radiator may be calculated using the following equation: (6.3.4-2) Khi=51.601-1.335α+0.0094α2 (6.3.4-3) where, ∆Phi——the resistance at the inlet of the radiator, Pa; Khi——the resistance coefficient of the triangle inlet of the radiator; vh——the air velocity through the windward side of the radiator, m/s; α——the vertex angle of the cooling delta, 40º≤α≤70º, º. 3 The resistance at the outlet of the radiator may be calculated using the following equation: (6.3.4-4) Kho=14.015-0.2929α+0.0017α2 (6.3.4-5) where, ∆Pho——the resistance at the outlet of the radiator, Pa; Kho——the resistance coefficient of the triangle outlet of the radiator;   4 The resistance of the radiator may be calculated using the following equation: (6.3.4-6) where, ∆Ph——the resistance of air flow passing through the radiator, Pa; Ch——the coefficient, which is obtained by test; n——the exponent, which is obtained by test; 5 The resistance of the air flow passing through the tower pillar may be calculated using the following equation: (6.3.4-7) (6.3.4-8) (6.3.4-9) where, ∆Pd——the resistance of the air flow through tower pillar, Pa; Cd——the resistance coefficient of tower pillar, which may be selected from those specified in Table 6.3.4-1; ρ——the density of air flow passing through the section, kg/m3; vd——the face velocity upstream of the tower pillar, m/s; Ad——the total cross-sectional area of air inlet column, m2; A——the total area of air inlet, m2; b——the width of the tower pillar parallel to the direction of air flow, m; d——the width of the tower pillar facing the direction of air flow, m; Re——the Reynolds number (103

Foreword ii 1 General provisions 2 Terms 3 Basic requirements 4 Meteorological parameter selection requirements of indirect dry cooling system 5 General layout of indirect dry cooling system 6 Design parameter selection and calculation of indirect dry cooling system 6.1 General requirements 6.2 Design parameter selection of indirect dry cooling system 6.3 Calculation of indirect dry cooling system 6.4 Design margin of indirect dry cooling system 7 Indirect dry cooling process system and equipment 7.1 Indirect dry cooling radiator system 7.2 Steam condenser 7.3 Circulating water pump and piping system 7.4 Expansion water tank system 7.5 Underground water storage tank and water filling and drainage system 7.6 Radiator cleaning system 7.7 Water quality control of circulating water system 7.8 Condensation water refine treatment system 7.9 Testing and instrumentation, alarm 7.10 Insulation, painting and heat tracing 8 Indirect dry cooling tower structure 8.1 General requirements 8.2 Main structure of indirect dry cooling tower 8.3 Widening platform 8.4 Tower core structure of horizontal radiator arrangement 8.5 Accessory structure 9 Operation and control requirements of indirect dry cooling system 9.1 Startup and shutdown 9.2 Normal operation 9.3 Winter operation 9.4 Summer operation 10 Test requirements of indirect dry cooling system 10.1 Mathematical and physical model test of indirect dry cooling system 10.2 Performance test of indirect dry cooling system Annex A Aerodynamic calculation resistance coefficient and correction factor of mechanical draught indirect dry cooling tower Annex B Water resistance and correction factor of cooling radiator bundle Explanation of wording in this code List of quoted codes Explanation of provisions