Uniform Air Distribution Research Articles

Analysis and structure optimization of the flow and temperature fields of the large-scale hot air drying room

Large-scale hot air drying rooms play a crucial role as efficient drying equipment across various industries. The uniform distribution of hot air is a crucial factor influencing the drying quality of large-scale hot air drying rooms. This study focuses on camellia seeds as the drying subject. Building on a porous media model and the drying kinetics of camellia seeds, a CFD model of the drying room was established. Three-dimensional simulations of the internal flow and temperature fields were performed using CFD software, and the simulated results aligned well with experimental data. To improve the uniformity, this study introduced an optimized design featuring a combination of a Type E3 air guide hood with five guiding plates and a fan, selected based on optimized angles (θ1 = 5°, θ2 = 10°). Under the condition of improving the structure without introducing a new heat source, the optimization ensured a significant improvement in flow field uniformity while making the temperature field closer to the desired ideal temperature. This offers a reference for the design and research of hot air drying equipment and hot air drying rooms.

Assisting denitrification and strengthening combustion by using ammonia/coal binary fuel gasification-combustion: Effects of injecting position and air distribution

The direct co-firing of ammonia (NH3) with coal is an effective approach for reducing carbon emissions from coal-fired plants. However, the limitations of NH3 combustion, such as its high ignition energy requirement and high NOx emissions, restrict its large-scale co-combustion in coal-fired units. In this study, a self-sustaining gasification–combustion experimental system was employed, and its denitrification performance and combustion strengthening capability for NH3/coal binary fuel under different NH3 injection positions and air distribution methods were evaluated. The results of co-firing 20% NH3 in the gasifier revealed that its operating temperature can be flexibly controlled within the optimal reaction temperature window of SNCR by adjusting the primary air ratio (λ1). Increasing λ1 was beneficial for NH3 and coal conversion and denitrification in the gasifier; at λ1 = 0.53, the conversion rate of NH3 and N2 reached 86.37% and 83.59%, respectively, with no NOx being detected at the gasifier outlet. Furthermore, increasing λ1 promoted the development of gasified char pore structure, thereby improving reactivity. After entering the down-fired combustor (DFC), increasing λ1 promoted NH3 and coal burnout and effectively controlled NOx emissions, reaching a level similar with that of pure coal under λ1 = 0.53. Co-firing 20% NH3 in the DFC also demonstrated that the introduction of inner secondary air was conducive to char burnout, however, increased NH3 slip. The outer secondary air promoted NH3 combustion, however, exacerbated NOx emissions and inhibited gasified char combustion. The uniform air distribution method balanced the combustion of NH3 and gasified char, and effectively controlled NOx emissions. When the same air distribution method was used, co-firing NH3 in the gasifier was more favourable for NOx control, whereas co-firing NH3 in the DFC benefited coal burnout. This study provides innovative ideas and serves as a reference for developing enhanced combustion and low NOx emission technologies for large-scale NH3 co-firing in coal-fired units.

CFD design and testing of an air flow distribution device for microwave infrared hot-air rolling-bed dryer

In this study, a new microwave infrared hot air rolling bed dryer (MIHRBD) was developed and computational fluid dynamics (CFD) techniques were introduced into the design process of the integrated drying system. The structure of the air distribution device was optimised to improve the airflow uniformity over the curved surface of the rolling bed in the microwave-hot air drying combined equipment. The research findings reveal that, across eleven models, the outlet airflow velocity stabilises once the number of mesh elements reaches 5 million, achieving significant computational accuracy at that point. Optimizing components like the uniform air distribution pipe, turbulence plates, and wind deflectors significantly enhanced airflow distribution uniformity by 52.1%. The best airflow and temperature distribution uniformity on the rolling bed surface was achieved when the inlet airflow velocity ranged from 1 to 3 m s−1, with minimum Vd, Uv and temperature non-uniformity coefficients of 0.007 m s−1, 7.2% and 0.2%, respectively. Validation tests on the MIHRBD pilot equipment showed that after optimizing the uniform air distribution device, the minimum temperature difference on the pleurotus eryngii surface was 3.1 °C. This confirmed the feasibility of the computational fluid dynamics method. Introducing hot air significantly enhanced pleurotus eryngii's drying uniformity, with the Page model effectively predicting the MIHRBD drying process. This study provides technical support for future developments in this field of equipment manufacturing and drying process analysis.

Simulation and Analysis of Hydrodynamic Behavior in Different Nozzles and Its Corresponding Fluidized Beds

Uniform air distribution is the basic condition for the stable operation of circulating fluidized beds and closely related to the hole layout of nozzles and the air outlet conditions. In this paper, CAD modeling software is used to establish different opening types for nozzles and the corresponding gasifier models, and Fluent simulation software for numerical simulations (k-ε model) is introduced to the hydrodynamic behavior of the upper opening, the side opening and the combined opening types of nozzles, as well as the corresponding single-nozzle fluidized bed gasifiers. The flow field distribution under the above opening modes is obtained, including the velocity distribution, static pressure distribution, and total pressure distribution, and the influence of the boundary conditions, including the inlet gas velocity and outlet pressure, on the flow field distribution inside the nozzle and in the single-nozzle fluidized bed gasifier is also investigated. The simulation results show that the suitable optimal operating conditions for the coal gasifier can be achieved with an inlet velocity of 30 m/s and an outlet pressure of 25 kPaG. Under the above conditions, the local fluidization dead zone at the elbow and top of the nozzle is narrower, the uniformity of the wind velocity can be improved, the pressure drop of the inner core tube of the nozzle is gentle, and the pressure distribution tends to be stable. Theoretically, the anti-slag performance of the nozzle is improved, which will enhance the stability and reliability of the operation of the gasification unit.

Design and evaluation of an R290-based freezing system and air distribution in a domestic-scale microwave-heated freeze-dryer prototype

Freeze-drying is a drying process that can result in long-term and cost-effective storage of food products. In the case of domestic applications, a compact freeze-dryer may lead to the production of added-value products in households and small farms. For this reason, this study aimed to determine the design of R290 refrigeration system together with air distribution system components in a one-chamber microwave-heated freeze-dryer prototype. The device is capable of drying both fresh and frozen food products. The freezing time of food products was experimentally analysed concerning various evaporator configurations to fulfill the final device design's compactness and high food load. The study showed that an internal evaporator located at the bottom of the freeze-dryer chamber outperformed the external heat exchangers with mini- and micro-channels. The freezing process was optimised based on the CFD model of airflow distribution in the microwave-heated chamber with a stationary multi-shelf system by proposing the shape and location of air guides and radial fans. The results showed that the solution involving air guides positioned at the ends of the shelves at a 60-degree angle provides uniform air distribution. The combination of experimental and numerical approaches resulted in a complete design of a prototype freeze-dryer chamber in which, according to the calculations performed, the freezing time of food products was 40% faster compared to the reference device.

Numerical Study of Air Distribution and Thermal Environment in Attached Ventilation Mode in the Generator Layer of a Hydropower Station

Because they are in enclosed underground buildings, the generator layers of hydropower stations have limited ventilation. In order to reduce the influence of a hot and humid environment on equipment and staff health and create a good thermal environment with good air quality for underground buildings, in this paper, vertical wall-attached ventilation was combined with the generator layer of a hydropower station to replace traditional ventilation. The influence of air supply velocity, air supply outlet position, and the opening mode of the generator layer on indoor velocity and temperature field distribution were analyzed via numerical simulation, and the evaluation indices of different cases were also compared. In the single-sided vertical wall-attached ventilation mode, when the velocity was increased from 4 m/s to 8 m/s, the maximum increment in the energy utilization coefficient was 41%, and the maximum reduction in the velocity non-uniformity coefficient was 9.5%. The results show that the single-sided mode can offer a higher ventilation efficiency than the double-sided mode, with a higher energy efficiency and a more uniform air distribution. Based on the mean temperature and velocity, and the key evaluation indices (head-foot temperature difference, percentage of dissatisfaction, non-uniformity coefficient, energy utilization coefficient, and air diffusion performance index), it is suggested that the single-sided air supply mode should be adopted for this kind of tall building, with an air supply velocity of v = 6 m/s and two open air supply outlets at each interval.

Experimental and computational (Chemical Kinetic + CFD) analyses of Self-Recuperative annular tubular porous burner for NH3/CH4 -air Non-Premixed combustion

Ammonia is now being explored as a potential gas turbine fuel because of its renewable and carbon-free nature. Ammonia combustion possesses various limitations, such as high NO emissions, low burning velocity, and high auto-ignition temperature. Moreover, dual-fuel combustion approaches can be used to mitigate these drawbacks. However, the limitations of available information about the resulting emissions are insufficient to encourage widespread adoption. In this work, an NH3/CH4-air fueled self-recuperative high aspect ratio annular tubular porous burner is developed for gas turbine power applications. In this burner, an annular zone surrounds the combustion chamber to preheat the incoming air, while two perforated discs are mounted between the combustor and annular zone for uniform distribution of air. Eight Zirconia foams (4 of 10 PPI and 4 of 20 PPI) are stacked at the upstream side of the combustor. Experimentally, air preheat temperature, combustor exit temperature, NO, and CO emissions are analyzed and measured for various ammonia addition (0–41 % by weight) percentages, equivalence ratio of 1.0, and heat inputs of 17 & 21 kW for 10 PPI and a combination of 10 and 20 PPI porous foams. A preheated air stream coming from the annular zone speeds up fuel dissociation and helps in stabilizing the flame on the upstream side of the combustor. Combustor exit temperatures are lower in sandwich cases of 10 + 20 PPI than the porous foams of 10 PPI. However, with porous foams of 10 PPI, the air preheat temperature is higher. The insertion of porous foams shows better recirculation of heat and stable combustion is observed for higher percentages of ammonia and higher thermal inputs. The OH radicals are distributed for larger areas inside the dumb combustor, while for porous combustion, it is distributed near the porous foams. The porous sandwich cases of 10 + 20 PPI shows higher combustion efficiency compared to 10 PPI and without porous cases. The chemical kinetic analysis shows that the HNO and HCO radicals act as the main intermediate channel for NO and CO production.

Experimental and numerical investigation of swirling flow on the conjugate cooling efficiency of an effusion-cooled combustor

Effusion cooling has been extensively employed in the liner thermal protection of modern combustors, however, its performance in swirling flow fields remains to be thoroughly investigated. This research aims to reveal insights into the effusion cooling characteristic across various swirl numbers (SN = 0∼1.21) and average blowing ratios (M‾ = 1.2–8.9) based on experimental and numerical approaches. Furthermore, semi-empirical engineering function equations for the area-weighted average cooling efficiency were compiled. The results show that inhomogeneity of the near-wall flow obstructs local effusion outflow, especially in the countercurrent side of the impingement zone, resulting in incremental flow heat transfer and disability in forming a cooling film. The increment of SN from 0.49 to 1.21 recedes the undermost level of conjugate cooling efficiency by an average of about 0.13, progressively impairs the cooling of the leading edge, and begets an ante displacement of the poorest cooling position from 0.43 to 0.31 (ratio of flow wise direction coordinate distance to flame tube dome height). Higher cooling air volume effectively strengthens the coolant effluent capacity to offer a more uniform distribution of cold air under swirl flow, and the overall conjugate cooling efficiency is enhanced by about 0.34 when M‾ increases from 1.2 to 8.9.

Optimizing biomass combustion in a 130 t/h grate boiler: Assessing gas-phase reaction models and primary air distribution strategies

Grate-firing technology is widely used for biomass combustion for heat and power production due to its good fuel flexibility. However, grate boilers often suffer from high unburnout, low efficiency, and high emissions, and require optimization to improve their performance. The distribution of primary air along the grate length significantly affects combustion and pollutant formation behaviors in the furnace; however, this effect is often under-investigated and poorly quantified. In this study, combustion of corn stover in a 130 t/h grate boiler is investigated experimentally and numerically. To establish a reliable baseline computational fluid dynamics (CFD) model and provide valuable reference for modeling and optimizing this industrial grate boiler, this study first investigates the applicability of the commonly used gas-phase reaction models. The finite rate/eddy dissipation model is found to outperform other gas-phase reaction models such as eddy dissipation model and eddy dissipation concept, which well predicts the temperature and shape of the flame in both the kinetics-controlled primary combustion zone and the diffusion-controlled burnout zone and shows the best agreement with the measured and site observations. Then, the study simulates and quantifies the effects of different primary air distribution modes (uniform, staged and refined-staged) on combustion performance of the boiler. Compared with the uniform primary air distribution, both the staged and refined-staged primary air distribution show an obvious increase in the char burnout ratio, from 76.5 % to 87.8 % and 95.5 %, respectively. Furthermore, the CO concentration at the furnace outlet is remarkably reduced, from 3178 ppm to 2766 ppm and 1917 ppm, respectively. This demonstrates that reasonable air supply in the latter two primary air distribution cases facilitates complete combustion in both the fuel-bed and freeboard. Moreover, in the latter two cases, the temperature distribution in the freeboard becomes more uniform, and the local oxygen-rich regions are eliminated. These are beneficial in suppressing the NO formation, as the emission of which decreases from 172 mg/m3 (at 11 % O2) to 161 mg/m3 and 156 mg/m3, respectively. This work provides important theoretical guidance for the accurate modeling and optimization of grate-firing boilers as well as the design of new grate boilers.

The Influence of Supply Channel Design on the Gas-Dynamic Structure of Air Flow in a Vertical Conical Diffuser

Vertical conical diffusers are used in power engineering, chemical industry, technological processes, and other industries. The efficiency of many machines and pieces of equipment is determined by the gas-dynamic and heat-exchange perfection of processes in diffusers. This study assesses the influence of the air supply method on flow structure in a diffuser. The studies were carried out on a test bench with thermal imaging for air flow rates ranging from 0.018 to 0.057 m3/s (42,500 < Re < 150,000). Two designs were examined: (1) a conventional air supply through one channel from below and (2) a nozzle air supply through four tubes at an angle of 45° to the vertical axis. In addition, the influence of the cross-sectional shape of the supply channels of both designs was studied. It is established that the use of a conventional air supply through one channel leads to the generation of a pronounced central flow along the vertical axis (all configurations of the supply channel) and the creation of stagnant zones in the corners of the diffuser (round and triangular channels; the use of a square supply channel causes the most uniform air distribution throughout the entire volume of the diffuser (while maintaining the central flow). It is found that with nozzle air supply, there are no stagnant zones in the corners and intense air movement generation in the centre of the diffuser (round and triangular tubes) can be observed; the use of square nozzle tubes causes intense flow movement at the base of the diffuser, which quickly collapses upstream, uniformly filling the entire volume of the diffuser’s cylindrical part. The presented data can be useful for designing various machines and pieces of equipment with vertical conical diffusers.

Numerical and experimental analysis of air-cooled Lithium-ion battery pack for the evaluation of the thermal performance enhancement

The main objective of this study is to assess the thermal performance of an air-cooled Lithium-ion battery pack. This involves analyzing the heat dissipation characteristics and temperature distribution within the battery pack at different operating conditions. Here, the thermal performance of the battery pack is evaluated numerically and experimentally. The experimental platform allows adjusting numerous control factors, like air velocity (0.5 to 2.0 m/s), air temperature (282.0 to 315.0 K), and battery pack discharge rate (0.5 to 2.5C). The temperature distribution is studied in longitudinal and transverse directions of the battery pack and circumferentially for a cell. The numerical simulations involve the solution of Shear Stress Transport (SST) k- ω model-based Navier-Stokes (N-S) equation using the ANSYS FLUENT R19.2 software. The numerical results were found to closely match the experimental findings with maximum error to be within 3.12%. The evaluation parameters used to assess the thermal performance of BTMS are maximum temperature(Tmax), maximum temperature difference (∆Tmax), average temperature (Tavg.), and standard deviation of the temperature σT within the battery pack. The numerical and experimental analyses show a reduction in both the maximum and mean temperature of the battery pack and improved temperature uniformity, with the increase in air velocity, lowering the discharge rate and decreasing the ambient temperature. The correlation between air inlet velocity and temperature drop is stronger at higher discharge rates than lower discharge rates. The effect is due to high heat transfer coefficient and uniform air distribution at high velocities, less heat generation and more time to dissipate heat at low discharge rates, and lower temperature of air at cold ambient conditions. The reduced temperatures and temperature uniformity minimizes the occurrence of localized hotspots within the battery pack. Further, for any given air inlet temperature, an increase in temperature is observed parallel to the direction of airflow. Under severe operating conditions, the inlet-to-discharge temperature difference reached a maximum of T = 22.14 K whereas, under mild conditions, it dropped to T = 0.21 K. The circumferential temperature non-uniformity of cells lying in high-temperature zone of the battery pack reduces with increasing velocity. The work presented here can help in the identification of potential hotspots and design better cooling strategies for the battery pack at different operating conditions.

Comparative studies and optimizations of air distribution of underground building ventilation systems based on response surface methodology: A case study

As underground enclosed buildings, utility tunnels have limited ventilation conditions. An efficient ventilation system is necessary for improving the indoor thermal environment and air quality in utility tunnels. In this paper, exhaust fan ventilation (EFV), relay fan ventilation (RFV), and innovative wall-attached ventilation (WAV) schemes are compared using a series of evaluation indicators (i.e., energy efficiency coefficient, nonuniform coefficient, temperature not guaranteed rate, and age of air). The results show that the WAV scheme offers a higher ventilation efficiency, while decreasing the age of air and providing a uniform air distribution. Thus, the WAV scheme is recommended for utility tunnel ventilation systems. Additionally, the WAV scheme is further optimized and analysed based on response surface methodology (RSM). The influence of different factors (i.e., the slot outlet height (h), slot outlet width (b), air-supply velocity (u0), and cable heat source intensity (q)) on the evaluation indicators is studied, and the optimal design scheme (h = 1.40 m, b = 0.12 m, u0 = 3.00 m/s, q = 74.5 W/m2) is obtained and verified. The age of air in the optimal design scheme is 486.50 s. This paper can provide a reference for the ventilation design of urban underground buildings.

Numerical Simulation of a Efficient Solar-Powered Ventilation System

The objective of this study is to conduct a numerical analysis of a small-scale solar ventilation-air conditioning system operating under the meteorological conditions of Bisha, Saudi Arabia. The primary objective of the proposed system is to provide sustainable and comfortable thermal conditions. To achieve this objective, the system recovers the heat wasted by the solar ventilation process and reuses it to power the desiccant dehumidification process. The solar chimney features a lateral (vertical) wall design, and a comparative performance investigation of two solar chimney designs (conventional vs original) is conducted. Mathematical models of the ventilated room and solar chimney are developed, and numerical simulations are carried out to evaluate the performance of each solar chimney design. The study aims to assess the ability of each design to maintain indoor thermal comfort through the analysis of air distribution temperature and air streamlines. The results of the performance comparison revealed that the proposed solar chimney design outperformed the conventional design in terms of thermal and ventilation performance. The proposed solar chimney design, with its lateral (vertical) wall, was also found to be more effective in maintaining indoor thermal comfort than the conventional design. The simulations showed that the proposed design produced a more uniform air distribution temperature within the ventilated room, resulting in improved comfort levels. Additionally, the proposed design was found to have a more efficient airflow pattern, with fewer areas of stagnant airflow. These results suggest that the proposed solar ventilation-air conditioning system has the potential to provide sustainable and comfortable thermal conditions in small-scale buildings.

Air speed and plastic crate vent-holes for wine grape quality during postharvest dehydration: commercial and laboratory studies.

Airflow is an important issue to favor postharvest dehydration keeping wine grape quality. The aim of this experimental work was to analyze the grape quality during postharvest dehydration: (i) in a commercial facility ('fruttaia') by monitoring the efficiency of the ventilation system and (ii) at laboratory level, studying the influence of crate type and airflow direction. In the fruttaia, the airflow was provided by an air duct hanging from the ceiling, and by floor fans. A great gap in air speed from 0 up to 3.7 m s-1 was measured in different sectors of the fruttaia, leading to a different weight loss and grape quality in crates, depending on crate stack height and sector. At the laboratory level, two tunnels, with exhaust or supply fans, were used and four crate types with different percentages of vent-holes were adopted. A decrease of about 5% delayed the weight loss rate depending on the type of crate, and the exhaust fan guaranteed a faster dehydration. The results clarified the inefficiency of the commercial ventilation system in ensuring homogeneous grape weight loss in all crates. In addition, the exhaust fan guaranteed a more uniform air distribution around crates, and a slightly higher air speed. © 2023 Society of Chemical Industry.

Pressure-volume mechanics of inflating and deflating intact whole organ porcine lungs

Pressure-volume curves of the lung are classical measurements of lung function and are impacted by changes in lung structure due to disease or shifts in air-delivery volume or cycling rate. Diseased and preterm infant lungs have been found to show heterogeneous behavior which is highly frequency dependent. This breathing rate dependency has motivated the exploration of multi-frequency oscillatory ventilators to deliver volume oscillation with optimal frequencies for various portions of the lung to provide more uniform air distribution. The design of these advanced ventilators requires the examination of lung function and mechanics, and an improved understanding of the pressure–volume response of the lung. Therefore, to comprehensively analyze whole lung organ mechanics, we investigate six combinations of varying applied volumes and frequencies using ex-vivo porcine specimens and our custom-designed electromechanical breathing apparatus. Lung responses were evaluated through measurements of inflation and deflation slopes, static compliance, peak pressure and volume, as well as hysteresis, energy loss, and pressure relaxation. Generally, we observed that the lungs were stiffer when subjected to faster breathing rates and lower inflation volumes. The lungs exhibited greater inflation volume dependencies compared to frequency dependencies. This study’s reported response of the lung to variations of inflation volume and breathing rate can help the optimization of conventional mechanical ventilators and inform the design of advanced ventilators. Although frequency dependency is found to be minimal in normal porcine lungs, this preliminary study lays a foundation for comparison with pathological lungs, which are known to demonstrate marked rate dependency.

STUDI DISTRIBUSI UDARA PENDINGIN REEFER CONTAINER IKAN PADA KERETA API MENGGUNAKAN CFD

Fresh fish is sensitive to storage temperature. Temperatures above 2 °C accelerate the growth of bacteria and cause spoilage. The optimal storage temperature for frozen fish is -20 °C. Reefer container with a closed cooling system serves to preserve by maintaining the temperature of frozen fish. The problem of this research is the uneven distribution of cold air in the reefer containers of the train, thereby reducing the quality of frozen fish. The purpose of this research is to increase the even distribution of air, velocity, and pressure in the reefer container of the train. The solution to the problem is simulation and analysis of the condition of the reefer container train using Computational Fluid Dynamics (CFD). Reefer containers without guide plates are simulated to find out the area of the train reefer containers that are not evenly distributed. The distribution of air in the reefer container of the train is improved even by the addition of guide plates with variations in angles of 40°, 50°, and 60°. This research produces qualitative data (velocity contour and pressure contour reefer container) and quantitative (average velocity and pressure). The results of this study are CFD simulation data of uniform distribution of air, speed, and pressure on the reefer container train with a 40⁰ guide plate.

Thermal Management and Energy Consumption in Air, Liquid, and Free Cooling Systems for Data Centers: A Review

The thermal management and reduction of energy consumption in cooling systems have become major trends with the continued growth of high heat dissipation data centers and the challenging energy situation. However, the existing studies have been limited to studying the influences of individual factors on energy saving and thermal management and have not been systematically summarized. Thus, this paper reviews the key factors in achieving thermal management and reducing energy consumption in each cooling system, the corresponding research, and optimization methods. To achieve these goals, in this paper, literature surveys on data center cooling systems are investigated. For data center air cooling, thermal management is mainly related to the uniform distribution of hot and cold air. Adjusting the porosity of perforated tiles can reduce energy consumption. For liquid cooling and free cooling systems, climate conditions, cooling system structural design, coolant type, and flow rate are key factors in achieving thermal management and reducing energy consumption. This paper provides the power usage effectiveness (PUE) values of the cooling systems in some cases. A summary of the key factors can provide directions for research on thermal management and energy reduction, and a summary of previous research can provide a basis for future optimization.

Research on a new optimization method for airflow organization in breeding air conditioning with perforated ceiling ventilation

Modern agricultural production puts forward higher requirement for environmental control. Uniform air distribution can form the stable temperature, humidity and velocity of indoor air, which is particularly important for agricultural production. In this paper, theoretical research is conducted on a nursery piggery and the velocity uniformity is defined to evaluate the performance of perforated ceiling ventilation. A new optimization method for airflow organization is developed, which improves the airflow organization based on the suitable air supply angle. It shows that the velocity uniformity is increased and then decreased with the increase of air supply angle, and the best air supply angle is around 35°. The optimal air supply angle changes with the plenum height, and there is a threshold for the plenum height. The best velocity uniformity can be achieved when the height of plenum is 0.5 m. Besides, the air supply velocity has almost no effect on the velocity uniformity. The optimization model for airflow organization based on the air supply angle is established and its accuracy is verified. Finally, a specific case is selected to compare and analyze the air distribution under different air supply methods, which verifies the feasibility of the optimization method proposed in this paper.

Study on the Uniformity of Secondary Air of a 660 MW Ultra-Supercritical CFB Boiler

Based on the field test of a 600 MW supercritical circulating-fluidized bed boiler, this paper optimizes the secondary air pipe layout scheme of a 660 MW ultra-supercritical circulating fluidized bed boiler with a similar furnace structure and carried out a numerical simulation on its air distribution uniformity. The secondary air box of the 660 MW ultra-supercritical circulating-fluidized bed boiler adopts a variable section design, and the secondary air branch pipe adopts a separate air inlet mode. The experimental results showed that the oxygen concentration was uniform near the rear wall, but all exhibited a “decrease–increase–decrease” profile along the horizontal line, which indicated that the trajectory of the secondary air jet was first in the shape of bending downward and then upward. To achieve a more uniform secondary air distribution for supercritical CFB boilers, further optimization of the layout of the bellows and branch pipes should be considered. Numerical results showed that the deviation rate of the internal and lower secondary air reached 17%, and there was optimization space for the secondary air branch pipe layout of the boiler. Its uniformity can be increased by adding valves and other measures. The velocity deviation of the secondary air of the 660 MW ultra-supercritical circulating-fluidized bed boiler can be within 3% by means of separate air supply and pipe diameter change, and better uniform air supply can be achieved to reduce the speed deviation by adding valves and adjusting the combustion.

Numerical simulation for energy consumption and thermal comfort in a naturally ventilated indoor environment under different orientations of inlet diffuser

This study numerically analyses a well-validated comprehensive work on IEQ in a naturally ventilated, occupied 3-dimensional office building with installed furniture and internal heat-generating surfaces. This study analyzes the effect of the inlet diffuser orientation (IDO) on the indoor thermal comfort (ITC) of occupants and the energy demand of the building for heating indoor air. The Optimization of ITC has also been calculated for the acceptable indoor occupant comfort and energy consumption. The study is valuable to analyze the relationship between IDO of 0°, 15°, 30°, 45°, 60°and 75°, on ITC and the energy consumption of the indoor environment. Different methods have been chosen to study the ITC of the occupants such as air temperature, air movement in the occupied zone, vertical temperature gradient, and PMV and PPD index according to ISO7730. The results show that under a uniform indoor air distribution, the variation in IDO considerably affects the ITC and energy consumption. Optimized ITC can reduce indoor energy consumption by 35.14%. The IDO slightly affects the PMV and PPD index. Occupant's legs are more sensitive to the naturally ventilated indoor environment due to the adverse effect of buoyancy force which may create the problem of the cold draft. For optimization of the ITC, the air temperature in the occupied zone plays a key role.