Numerical Calculations and Cold Tests for Flow Fields of a 220t/h Retrofitted Oil-Boiler

In this paper, cold simulation experiments and numerical calculations are conducted to predict 3 D flow field aerodynamics for an oil furnace after being retrofitted due to its fuel variation. K ε model and SIMPLE program under body fit coordination (BFC) system, in which TTM non orthogonal method is used to control the irregular geometric boundary, are adopted to solve the control equations. Model tests are conducted to check the calculation results, showing that they are in agreement with each other. Three different alternatives with different side window locations are also calculated to optimize the designs. The field retrofitting results show that the combination of cold tests with numerical calculations has prosperous application in retrofitting or renewing medium and small boilers.

Feasibility Analysis on the Integrated Application of Solar Energy, Biogas, Coal-fired Boiler and Radiant Floor Heating for Rural Residence

The feasibility of adopting a balanced energy mix mode (domestic solar energy, biogas, coal-fired boiler and radiant floor heating) was proposed. Taking a typical rural residence in Zhengzhou City for example, the study through theoretical analysis and calculation showed that such a balanced energy mix is an economic way and efficient in saving energy and reducing air pollution, and elaborated the theoretical feasibility of popularizing such a heat supply mode in rural areas.

Equation of Radiation Heat Transfer in Multiple Combustion Boiler Furnace of Fluidized Bed and Pulverized Coal Firing

The equation for radiation heat transfer in a multiple combustion boiler furnace with nuidized bed and pulverized coal firing is derived from direct calculation of radiation heat transfer.

The Application of Radiation Shields for Thermal Control of Superheater Tubes in Boiler

Superheater tubes temperature control is a necessity for long lifetime, high efficiency and high load following capability in boiler. This study reports a new approach for the control strategy design of boilers with special shields. The presented control strategy is developed based on radiation thermal shields with low emissivity coefficient and high reflectivity or scattering coefficient. In order to simulate the combustion event in boiler and heat transfer to superheater tubes, an effective set of computational fluid dynamic (CFD) codes is used. Results indicate a successful identification of over- heated zones on platen superheater tubes and effect of radiation shields for solving this problem.

On-Line Life Monitoring Technique for Tube Bundles of Boiler High-Temperature Heating Surface

High-temperature heating surface such as superheater and reheater of large-sized utility boiler all experiences a relatively severe working conditions. The failure of boiler tubes will directly impact the safe and economic operation of boiler. An on-line life monitoring model of high-temperature heating surface was set up according to the well-known L-M formula of the creep damages. The tube wall metal temperature and working stress was measured by on-line monitoring, and with this model, the real-time calculation of the life expenditure of the heating surface tube bundles were realized. Based on the technique the on-line life monitoring and management system of high-temperature heating surface was developed for a 300 MW utility boiler. An effective device was thus suggested for the implementation of the safe operation and the condition-based maintenance of utility boilers.

Heating and Cooling Hybrid System with Gas Mixture Sourced Heat Pump and Heating Boiler

Preliminary investigation shows that air sourced type heat pumps by energy efficiency are competitive with gas boilers having 93% of coefficient of performance （COP） if heat pumps are used in climatic zones, having outside air temperature higher than （-3 ℃ to -5 ℃）. But, in such conditions the heat pump＇s evaporator is covered by ice crust, which cuts off the flow of outside air-heat source through the evaporator of heat pump. For avoiding stating problems it is recommended to use as heat source a mixture of waste warm gases. In this article a high efficiency heating-cooling system is developed, consisting of warm gases mixture sourced heat pump, heating boiler operating simultaneously with heat pump and solar air heater. The heating demand of the served house is shared between boiler and heat pump. Instead of outside air the warm gases mixture enters into evaporator of heat pump. A new construction of heat exchanger was developed. The article presents the structure and principle of operation, as well as the method for optimization and design of suggested system. Analysis proved high energy efficiency and cost effectiveness of the new system.

Power Generation Systems Using Continuous Blowdown Waste Heat from Drum Boilers Driving an Organic Rankine Cycle

提出了一种利用汽包锅炉排污系统余热的有机朗肯循环发电系统,有机工质回收扩容器疏水的热量,并通过气轮机发电。建立了系统的热力性能分析模型,并对R227ea、RC318、R236ea、R245fa、R245ca、R123和R113等7种工质的热力性能进行了优化。结果表明,临界温度高的工质,其o2循环的最佳主气温度（蒸发温度）反而低；亚临界循环采用干流体时,过热不利于余热的利用；超临界循环可以改善热源与工质间的温度匹配,有利于增大系统输出功,但是其运行压力高、大比热区的传热恶化等问题是实际运行和设计需要考虑的因素；R236ea的热力性能优于其余6种工质。

A simulation Study on the System Combined Solar Energy with Biogas Boiler for Floor Radiant Heating and Fuel

A mathematical model was built for simulating an innovative design system combined solar energy with biogas boiler for floor radiant heating and fuel. Effects of the ambient air temperature on the performance of the system had been examined. And the results also support theoretical feasibility of the system.

Design Optimization of Boiler Tail Flue in Supercritical Carbon Dioxide Power Generation System

The S-CO_(2) top-bottom combined cycle based on overlap energy utilization can lead to excessive heating area,due to the small temperature difference and the large thermal load for the heating surface at the tail of the boiler.Therefore,reasonable optimization indexes are needed for design optimization.Common optimization indexes include heating area and working medium pressure drop,but lower working medium pressure drop usually leads to large heating area,for example,with the increase of tube inner diameter or boiler width,the pressure drop decreases but the heating area increases.Thus,if both are used as optimization indexes,it will be difficult to choose the optimum tube inner diameter and boiler width.In this paper,exergy loss analysis is used,in combination with economic analysis,the optimization index is unified to the cost per unit heat transfer of the heating surface.The thermal calculation and pressure drop calculation models are established for the heating surface at the tail of the boiler.The optimized heating surface can greatly improve the economic benefit.

Numerical Investigation on the Heat Transfer Characteristics of Supercritical Water in a Non-Uniformly Heated Tube for a Supercritical CFB Boiler

In this paper,a numerical model was built by ANSYS FLUENT to investigate the heat transfer performances of supercritical water in a circumferential non-uniformly heated vertical tube.The Shear Stress Transport(SST)k-ωmodel was adopted for describing turbulence.The operating parameters are chosen according to a 660 MW ultra-supercritical CFB boiler.The heat transfer performances under different operating parameters,such as boiler load,flow direction and heat flux distribution are analyzed.The temperature and heat flux on inner wall varies along the circumference and show symmetric distributions.The overall heat transfer performances at each cross section are better than the local heat transfer performance of midpoint of heating side.Flow direction has a great influence on heat transfer performance;it changes the radial distribution of axial velocity and then affects the turbulence distribution.Therefore,upward flow condition shows a better heat transfer performance.Smaller heat flux improves both the overall and local heat transfer performances.Reducing the heat flux area is not conducive to the overall heat transfer,but does not affect the local heat transfer at the midpoint of heating side.Finally,a new correlation is fitted based on the simulated results of supercritical water heat transfer with circumferential non-uniform heat flux distributions.

Optimization Study of Active-Passive Heating System Parameters in Village Houses in the Southern Xinjiang Province

Aiming at the problems of large energy consumption and serious pollution of winter heating existing in the rural buildings in Southern Xinjiang,a combined active-passive heating system was proposed,and the simulation software was used to optimize the parameters of the system,according to the parameters obtained from the optimization,a test platform was built and winter heating test was carried out.The simulation results showed that the thickness of the air layer of 75 mm,the total area of the vent holes of 0.24 m^(2),and the thickness of the insulation layer of 120 mm were the optimal construction for the passive part;solar collector area of 28 m^(2),hot water storage tank volume of 1.4 m^(3),mass flow rate of 800 kg/h on the collector side,mass flow rate of 400 kg/h on the heat exchanger side,and output power of auxiliary heat source of 5∼9 kWwere the optimal constructions for active heating system.Test results showed that during the heating period,the system could provide sufficient heat to the room under different heating modes,and the indoor temperature reached over 18°C,which met the heating demand.The economic and environmental benefits of the system were analyzed,and the economic benefits of the systemwere better than coal-fired heating,and the CO_(2) emissionswere reduced by 3,292.25 kg compared with coalfiredheating.The results of the study showed that the combinedactive-passiveheating systemcouldeffectively solve the heating problems existing in rural buildings in Southern Xinjiang,and it also laid the theoretical foundation for the popularization of the combined heating systems.

Paraffin–CaCl_(2)·6H_(2)O dosage effects on the strength and heat transfer characteristics of cemented tailings backfill

The challenge of high temperatures in deep mining remains harmful to the health of workers and their production efficiency The addition of phase change materials (PCMs) to filling slurry and the use of the cold storage function of these materials to reduce downhole temperatures is an effective approach to alleviate the aforementioned problem.Paraffin–CaCl_(2)·6H_(2)O composite PCM was prepared in the laboratory.The composition,phase change latent heat,thermal conductivity,and cemented tailing backfill (CTB) compressive strength of the new material were studied.The heat transfer characteristics and endothermic effect of the PCM were simulated using Fluent software.The results showed the following:(1) The new paraffin–CaCl_(2)·6H_(2)O composite PCM improved the thermal conductivity of native paraffin while avoiding the water solubility of CaCl_(2)·6H_(2)O.(2) The calculation formula of the thermal conductivity of CaCl_(2)·6H_(2)O combined with paraffin was deduced,and the reasons were explained in principle.(3) The“enthalpy–mass scale model”was applied to calculate the phase change latent heat of nonreactive composite PCMs.(4)The addition of the paraffin–CaCl_(2)·6H_(2)O composite PCM reduced the CTB strength but increased its heat absorption capacity.This research can give a theoretical foundation for the use of heat storage backfill in green mines.

Heat and power load dispatching considering energy storage of district heating system and electric boilers

As one of promising clean and low-emission energy, wind power is being rapidly developed in China.However, it faces serious problem of wind curtailment,particularly in northeast China, where combined heat and power(CHP) units cover a large proportion of the district heat supply. Due to the inherent strong coupling between the power and the heat load, the operational flexibility of CHP units is severely restricted in winter to meet the heat supply demand, which imparts considerable stress on the wind power connection to the grid. To promote the integration of wind power and enhance the flexibility of CHP units, this paper presented a method of heat and power load dispatching by exploring the energy storage ability of electric heating boilers and district heating systems. The optimization results indicate that the proposed method can integrate additional wind power into the grid and reduce the coal consumption of CHP units over the optimized period. Furthermore, the thermal inertia of a district heating system is found to contribute more to the reduction of coal consumption, whereas the electric heating boilers contribute to lower wind curtailment.

The Heat Transfer Coefficients of the Heating Surface of 300 MWe CFB Boiler

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.

Research on Marine Boiler's Pressurized Combustion and Heat Transfer

The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.

The Study on the Heat Transfer Characteristics of Oxygen Fuel Combustion Boiler

According to 350 MW and 600 MW boilers,under oxygen fuel condition,through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model,the temperature distribution,heat flux distribution and absorption heat distribution,etc.was obtained which compared with those under air condition.Through calculation,it is obtained that the primary and secondary flow mixed well,good tangentially fired combustion in furnace was formed,the temperature under air condition obviously higher than the temperature under O26 condition.The adiabatic flame temperature of wet cycle was slightly higher than that of dry cycle.The maximum heat load appeared on the waterwall around the burner area.The heat load gradually decreased along the furnace height up and down in burner area.The heat absorption capacity of the furnace under O26 was lower than that under the air condition.The heat absorption capacity of the platen heating surface under 026 was equal to that under air condition.And the heat absorbing capacity of waterwall under O26 was about 7%~12% less than that under air condition.

A Method for Optimum Heating and Cooling Boiler Components of a Complex Shape

A numerical method for determining a transient fluid temperature is presented.The method is formulated to minimize the total time of heating and cooling operation based on the assumption that maximum tensile and compressive total stresses in a solid can not exceed the allowable value during the entire process.The method can be used for any construction element of a simple or complicated geometry.In this method,material properties of solids can be assumed as constant or temperature dependent.The method will be implemented for the heating operation of an outlet header.This construction element is mounted in supercritical power plants.The outlet header is installed in the 460 MW power unit and it is designed for the working pressure of p_w=26.5 MPa and the steam working temperature of T_w=554℃.The results obtained from the proposed method will be compared with the calculations according to TRD 301-German boiler code.

Thermal Inertia of 330 MW Circulating Fluidized Bed Boiler during Load Change

The operating principles of Circulating Fluidized Bed(CFB)boilers involve a significant amount of heat accumulation,which forms the thermal inertia of the boiler and hinders the improvement of its variable load response rate.This study aims to characterize the thermal inertia of CFB boilers by evaluating the change in the boiler's heat accumulation corresponding to the change in unit power generation.The thermal inertia of a 330MW CFB boiler was determined through the collection of operating data under four different operating conditions of 30%,50%,75%,and 100%load.The study proposes to substitute the existing refractory material with a metal grille to reduce the thermal inertia of the boiler.The effect of the metal grille on heat transfer was confirmed through verification on a 440 t/h CFB boiler,and its performance change and thermal inertia reduction were further predicted.The results indicate that over 50%of the total thermal inertia of CFB boilers originates from the refractory material.The use of metal grille in place of refractory material improved heat transfer in the furnace,resulting in a decrease of the furnace chamber temperature by 13℃in the 330 MW CFB boiler.This reduction of thermal inertia by 30%-35%will facilitate faster load lifting and lowering of the boiler,fulfilling the requirement for flexible peaking.

An Efficient Method for Heat Recovery Process and Temperature Optimization

Flue gas heat loss accounts for a significant component of theoverall heat loss for coal-fired boilers in power plants. The flue gas absorbsmore heat as the exhaust gas temperature rises, which reduces boiler efficiencyand raises coal consumption. Additionally, if the exhaust gas temperatureis too high, a lot of water must be used to cool the flue gas for the wetflue gas desulfurization system to function well, which has an impact onthe power plant’s ability to operate profitably. It is consequently vital totake steps to lower exhaust gas temperatures in order to increase boilerefficiency and decrease the amount of coal and water used. Desulfurizationperformance may be enhanced and water use can be decreased by reasonableflue gas characteristics at the entry. This study analyzed the unit’s energyconsumption, investment, and coal savings while proposing four couplingstrategies for regulating flue gas temperature and waste heat recovery. Agraded flue gas conditioning and waste heat recovery plan was presentedunder the condition of ensuring high desulfurization efficiency, along withthe notion of minimizing energy loss owing to energy inflow temperaturedifference. Numerical results show that the proposed methods improved thesystem performance and reduced the water consumption and regulated theboiler temperature.

Theoretical Calculation Model of Heat Transfer for Deep-derived Supercritical Fluids with a Case Study

Based on a set of equations established by Duan et al. (1992, 1996) for a geofluid system H2O-CO2-CH4(-N2), a formula is obtained to calculate the heat changes. Combining the geological T-P conditions (geothermal gradients and lithostatic and hydrostatic pressures), the enthalpy of some typical geofluids is figured out. Then the principles of heat transfer of deep-derived supercritical fluids are discussed. The result shows that deep-derived geofluids can bring a large amount of thermal heat and release most heat to the shallow surroundings as they move up, because the molar enthalpies vary very greatly from the deep to shallow, increasing with the increases of T and P. Generally, more than tens of kilojoules heat per molar can be released. Furthermore, the molar enthalpy is affected by the compositions of the geofluids, and the molar enthalpy of CO2, CH4, or N2 is greater than that of H2O, being twice, more than twice, and about 140% of H2O, respectively. Finally, a case study is conducted by investigating a source rock sequence affected hydrothermally by magmatic fluids in the Huimin depression of Shengli Oilfield. The thermal heat calculated theoretically of the fluids related to a diabase intrusion is quite large, which can increase the temperature near the diabase to about 300℃, and that can, to some extent, account for the abnormal rise of the vitrinite reflectance, with the highest of about 3.8% (Ro).