Abstract
A double reheat ultra-supercritical boiler is an important development direction for high-parameter and large-capacity coal-fired power plants due to its high thermal efficiency and environmental value. China has developed a 1000 MW double reheat ultra-supercritical boiler with steam parameters of 35 MPa at 605°C/613°C/613°C. Reasonable water wall design is one of the keys to safe and reliable operation of the boiler. In order to examine the thermal-hydraulic characteristics of the double reheat ultra-supercritical boiler, the water wall system was equivalent to a flow network comprising series-parallel circuits, linking circuits and pressure nodes, and a calculation model was built on account of the conservation equations of energy, momentum and mass. Through the iterative solving of nonlinear equations, the prediction parameters of the water wall at boiler maximum continue rate (BMCR), 75% turbine heat-acceptance rate (THA) and 30% THA loads, including total pressure drops, flow distribution, outlet steam temperatures, fluid and metal temperatures were gotten. The results of calculation exhibit excellent thermal-hydraulic characteristics and substantiate the feasibility of the water wall design of the double reheat ultra-supercritical boiler.
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Abbreviations
- d n :
-
inner diameter/m
- d w :
-
outer diameter/m
- f :
-
friction coefficient
- G :
-
mass flux/kg·m2·s-1
- h :
-
enthalpy/J·kg1
- h f :
-
enthalpy of bulk fluid/J·kg1
- h in :
-
inlet enthalpy/J·kg1
- h out :
-
outlet enthalpy/J·kg1
- h w :
-
enthalpy of fluid of tube wall surface fluid/J·kg-1
- J n :
-
non-uniformity coefficient of heat flux of inner wall
- k :
-
absolute roughness of the inner tube/m
- l :
-
tube length/m
- M(i):
-
mass flow rate in circuit i/kg·s1
- M tot :
-
total mass flow rate/kg·s1
- Nu :
-
Nusselt number
- P(i):
-
pressure in circuit i/MPa
- P cs :
-
outlet pressure in economizer/MPa
- ΔP(i):
-
pressure drop in circuit i /MPa
- ΔP f :
-
frictional pressure drop/MPa
- ΔP g :
-
gravitational pressure drop/MPa
- ΔP l :
-
local pressure drop/MPa
- Pr b :
-
Prandtl number of while the qualitative temperature is bulk fluid temperature
- Pr gw :
-
Prandtl number of the gas phase while the qualitative temperature is inner tube wall temperature
- Pr w :
-
Prandtl number while the qualitative temperature is inner tube wall temperature
- \(\overline{Pr_{\rm{w}}}\) :
-
Average Prandtl number while the qualitative temperature is inner wall temperature
- q :
-
heat flux/W·m-2
- q w :
-
heat flux of outer wall/W’ m2
- Re b :
-
Reynodes number while the qualitative temperature is bulk fluid temperature Reg Reynodes number of the gas phase
- Re w :
-
Reynodes number while the qualitative temperature is inner tube wall temperature s
- T f :
-
fluid temperature/°C
- T m :
-
metal temperature in the middle of tube wall/°C
- T n :
-
metal temperature of inner tube wall/°C
- T qd :
-
metal temperature in the tip of fin/°C
- T qg :
-
metal temperature in the root of fin/°C
- T w :
-
metal temperature of outer tube wall/°C
- x :
-
steam quality of fluid/kg·kg1
- α :
-
coefficient of heat transmission/ kW·m-2·°C-1
- δ :
-
fin thickness/m
- η qd :
-
balance coefficient of heat flux in the tip of fin
- η qg :
-
balance coefficient of heat flux in the root of fin
- λ :
-
thermal conductivity of tube/W·m-1 ·K-1
- λ cr :
-
critical thermal conductivity /W·m-1 ·K-1
- λ g :
-
thermal conductivity of the gas phase/W·m-1·K-1
- μ w :
-
dynamic viscosity while the qualitative temperature is inner tube wall temperature/N·s·m-2
- ξ :
-
local resistance coefficient
- ρ :
-
average density of fluid/kg·m-3
- ρ g :
-
density of gas phase/kg·m-3
- ρ 1 :
-
density of liquid phase/kg·m-3
- ρ w :
-
density while the qualitative temperature is inner tube wall temperature/kg·m-3
- ψ :
-
correction coefficient
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Acknowledgement
This work is financially supported by the National Key Research & Development Program of China (2018YFB0604400).
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Wan, L., Yang, D., Zhou, X. et al. Thermal-Hydraulic Calculation and Analysis on Evaporator System of a 1000 MW Ultra-Supercritical Pulverized Combustion Boiler with Double Reheat. J. Therm. Sci. 30, 807–816 (2021). https://doi.org/10.1007/s11630-020-1322-2
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DOI: https://doi.org/10.1007/s11630-020-1322-2