Uniform Air Distribution Research Articles

Influencing factors of thermal performance of small-size vaccine cold storage: An experiment-based parametric study

The temperature gradient and thermal performance of a 20-m2 small-size vaccine cold storage warehouse for a working temperature range of 2–8 °C are studied in four central cities of northern, central and southern Jiangsu Province in China. The effects of cold storage geometry, cooler layout, air curtain and vaccine load on the thermal performance of vaccine cold storage are experimentally studied. Based on the findings in experiments, evaluation metrics are proposed for vaccine cold storage with loads. The results showed that for small vaccine cold storage, the arrangement of two air coolers with appropriate cooling capacity aligned along the length direction produces a more uniform air distribution inside the cold storage. With a reduced length to width ratio of cold storage, the temperature inhomogeneity coefficient decreased. Meanwhile, an air curtain outlet wider than the door can better maintain the cold storage temperature when the door is open. Results of three extended evaluation metrics were obtained for a case with 80% load, i.e. the average temperature deviation ratio Nη = 1.38, the ratio of temperature inhomogeneity coefficient Nσ = 1.15, and the temperature range ratio NR = 1.16, showing the deviation of temperature field of the loaded vaccine cold storage from the unloaded one.

Analysis and optimization of air distribution and ventilation performance in a generator hall using an innovative attached air supply mode

The continuous development of hydropower necessitates the extensive design and construction of hydropower stations. As an underground large space building, it is difficult for the air in the hydropower station to directly exchange with the external environment. Scientifically reasonable air supply modes are indispensable for ensuring a uniform air distribution with low energy consumption. In this study, numerical simulations were carried out to analyse the air distributions and thermal environments under three air supply modes: roof air supply (RAS), sidewall air supply (SAS), and attached air supply (AAS). A set of evaluation indices, namely, the air velocity, air temperature, nonuniformity coefficient, and energy efficiency coefficient, were adopted to assess the ventilation performance of these three modes. Moreover, an orthogonal experiment was conducted to optimize the ventilation performance with four factors (air outlet height, air outlet width, air supply velocity, and heat source intensity) in the AAS mode. The average temperatures among the RAS, SAS, and AAS were 26.1 °C, 26.4 °C, and 26.0 °C, respectively. The results indicated that the attached air supply (AAS) mode is recommended for generator hall applications due to its lower nonuniformity coefficient and higher energy efficiency coefficient. Based on the range analysis and variance analysis, the air outlet height exhibited significant effects on the air distribution and ventilation performance. This research provides design references for the innovative design of air supply systems in large space buildings.

Application of an Asterisk Plate in the Flow Diversion of the Volatile Organic Compound Removal System

AbstractIn order to reduce process complexity and manufacturing difficulty, we proposed to use a single air distribution plate to guide the flow and achieve uniform air distribution. We established...

PHYSICO-MATHEMATICAL MODEL OF VENTILATION SYSTEM FORCING OF CLEAN AIR IN LIVESTOCK PREMISES

The microclimate of livestock facilities is determined by a range of factors, including physical parameters: humidity, atmospheric pressure, light, temperature, speed and direction of air movement. Air quality plays an important role - the concentration of harmful gases and microorganisms, dust. The parameters of the microclimate affect not only the productivity of animals, but also their health. In order not to harm the health of the animal and achieve the desired performance, these parameters must be adjusted with special equipment. The purpose of research is to substantiate the design and technological parameters of the ventilation system for the injection of clean air in livestock premises to ensure uniformity of its distribution. The article presents the results of research to substantiate the design and technological parameters of the ventilation system for the injection of clean air in pig farms to ensure uniformity of its distribution. As a result of analytical studies of the parameters of the slit of the nozzle for air injection from the condition of uniform air distribution, an approximate equation for its width δ'y depending on the y-axis location for different effective diameters of the nozzle d'H. For the system of injection of clean air the condition according to which at opening of all discharge valves it is necessary to provide uniformity of distribution of air by system of injection is set. For this purpose the central air duct for air injection should have a wedge-shaped form of length L' with constant height b', with initial width a'N and final a'1. As a result of theoretical researches dependences of a lateral angle of a wedge θ the central air duct of system of injection of pure air and its width on the end a1' on distance between adjacent sections L'0, width of the central air duct on its beginning aN' and quantity of branch pipes for injection N' are established. As a result of analytical studies of pressure losses of the ventilation system of pure air injection of the pigsty, the dependences of changes in pressure losses Δp2 and power NW2 required for pumping air through it on the width of the central air duct aN, air flow through the system qk, length between system pipes L0 and their number N.

Investigation of Air Distribution in Mosque Rooms with Different Angles of Supply and Inlet Velocity

The HVAC (heating, ventilation, and air conditioning) systems utilization has increased in the last decade. It conducts global warming which has an impact on the rising of global temperatures. An excellent air conditioning system will make the room comfortable conditions. This paper aims to investigate the mosque space with a cooling model of wall-mounted air conditioning and the difference in inlet angle and air inlet velocity. The room design was constructed using SolidWorks software. Air distribution observations were created using ANSYS Workbench simulation software. The use of a supply angle of 90° results in an even distribution of air with a low inlet velocity, whereas in conditions of a supply angle of 60° requires a higher inlet speed. Thus, the uniform air distribution is able to be realized by the proper configuration which results an appropriately room temperature and saves energy usage.

Ventilation effectiveness of uniform and non-uniform perforated duct diffusers at office room

Half of the energy usages in buildings is due to HVAC systems, and the efficiency of the subsections plays an essential role in the evaluation of the total energy consumption. Previous works on ventilation systems using perforated duct diffusers (PDDs) were mainly concentrated on the calculation of the thermal comfort indices, while their energy consumption and ventilation effectiveness were omitted. In this paper, a mixed experimental-numerical method has been developed to evaluate the real efficiency of PDDs with different perforation patterns. So, an office room facility is used for the full-scale experiments and the validation of the numerical simulations. Incidentally, five RANS models have been benchmarked to highlight the most accurate numerical model for this specific application. As a result, a k-ε Realizable turbulence model with 4.3 million mesh elements has been preferred over the tested two-equation turbulence models to determine the diffuser parameters like age of air, terminal velocities, air-change effectiveness, and air exchange efficiency. Within this model, the required outdoor airflow for four types of PDDs has been calculated following the ASHRAE standard procedure. The discrepancy of the real efficiency and the calculated value for the nearest application in the standards shows that the performance of PDDs is underestimated, and they require lower airflow in reality. Later, it is shown that for the systems using PDDs, the required airflow and energy consumption decrease by up to 18.4%, and a more uniform air distribution is achieved using a non-uniform perforation pattern.

Numerical Simulation of the Effect of Combustion Process on Flue Gas Thermal Deviation in 660MW Boiler

In order to analyze the effect of the air volume on the combustion side and the non-uniformity of pulverized coal on the temperature distribution of the boiler outlet flue gas, and then analyze the thermal deviation characteristics of the steam heating surface, the following five different working conditions are calculated and analyzed in a 660MW boiler. Results show that the deviation of pulverized coal content of each burner and the deviation of primary air volume are the important factors that cause the temperature deviation of flue gas outlet in the furnace. Therefore, it is an important way to improve the temperature distribution and reduce the thermal deviation of flue gas outlet by improving the uniform combustion and air distribution of the burner in the furnace.

Nature-Inspired Flow-Fields and Water Management for PEM Fuel Cells

Flow-field design is crucial to polymer electrolyte membrane fuel cell (PEMFC) performance, since non-uniform transport of species to and from the membrane electrode assembly (MEA) results in significant power losses. The long channels of conventional serpentine flow-fields cause large pressure drops between inlets and outlets, thus large parasitic energy losses and low fuel cell performance.Here, a nature-inspired approach is used to design flow-fields guided by the structure of the human lung.[1-4] Its fractal geometry provides scalable, uniform distribution of air from a single outlet (trachea) to multiple outlets (alveoli). Furthermore, the human lung transitions between two flow regimes: 14-16 upper generations of branches dominated by convection, and 7-9 lower generations of space-filling acini dominated by diffusion. The upper generations of branches reduce the gas flow to a rate compatible with the rate in the diffusional regime (Pé ~ 1); in addition, the channel dimensions between branching points are proportioned in a way that results in constant entropy production in both regimes and, thus, in minimal global entropy production over the entire structure of the human lung.By employing a three-dimensional (3D) fractal structure as flow-field inlet channel, we aim to yield similar benefits from replicating these characteristics of the human lung. The fractal pattern consists of repeating “H” shapes, where daughter “H’s” are located at the four tips of the parent “H”. The fractal geometry obeys Murray’s law, much like the human lung, hereby leading to minimal mechanical energy losses. Furthermore, the three-dimensional branching structure provides uniform local conditions on the surface of the catalyst layer, as only the outlets of the fractal inlet channel are exposed to the MEA.Numerical simulations were conducted to determine the number of generations required to achieve uniform reactant distribution and minimal entropy production. The results reveal that the ideal number of generations for minimum entropy production lies between N = 5 and 7, for 10 cm2 surface area.[3, 5] Guided by these simulation results, three flow-fields, with N = 3, 4 and 5, were 3D printed via direct metal laser sintering (DMLS), and experimentally validated against conventional serpentine flow-field based PEMFCs. The fractal flow-field based PEMFCs with N = 4 and 5 generations showed ~20% and ~30% increase in performance and maximum power density over serpentine flow-field based PEMFCs above 0.8 A cm-2 at 50% RH. At fully humidified conditions, though, the performance of a fractal flow-field based PEMFC with N = 5 significantly deteriorates due to flooding issues.[3]Another defining characteristic of the fractal approach is scalability, which is an important feature in nature. Fractal flow-fields can bridge multiple length scales by adding further generations, while preserving the building units and microscopic function of the system. Larger, 3D printed fractal flow-fields (25 cm2 surface area) with N = 4 are compared to conventional serpentine flow-fields. Performance results show that fractal and serpentine flow-field based PEMFCs have similar polarization curves, which is attributed to the significantly higher pressure drop (~ 25 kPa) of large serpentine flow-fields compared to fractal flow-fields. However, such excessive pressure drop renders the use of large serpentine flow-field prohibitive, thus favoring the fractal flow-field.[3]A shortcoming of these fractal flow-fields for PEMFCs operated at high humidity is, though, their susceptibility to flooding in the gas channels, due to low gas velocity. This problem has led to the development of a nature-inspired water management mechanism that draws inspiration from the ability of the Thorny Devil (Australian lizard) to passively transport liquid water across its skin using capillary pressure.[6] We have recently integrated this strategy with the fractal N = 4 flow-fields and verified the viability of the strategy using neutron imaging. Implementation of this water management strategy is expected to circumvent remaining problems of high-generation fractal flow-fields.

Thermal performance of multi-pipe earth-to-air heat exchangers considering the non-uniform distribution of air between parallel pipes

In multi-pipe structures of earth-to-air heat exchangers (EAHEs), the airflow distribution between parallel pipes is not uniform and depends on many geometrical parameters, primarily the relation between the diameters of parallel pipes and manifolds, and the length of branch pipes. The phenomenon of airflow non-uniformity is usually neglected in the thermal performance calculations. This report investigates the influence of airflow distribution patterns on the thermal performance of multi-pipe EAHEs in order to bridge this knowledge gap. The calculations have been performed for a winter-time season for exchangers located in the climatic conditions of Central Europe. Analysis was conducted for different airflow conditions characterized by an airflow distribution uniformity coefficient. Results show that the thermal performance calculated for real EAHEs, with branch-pipes of a length L = 76d and diameters equal to the main pipe diameters, can be up to 28% lower than for ideal (uniform) distribution of air in an analogous exchanger. For EAHEs with branch-pipes of a length L = 300d and main pipes 1.4 times larger in diameter than parallel branch-pipes, the differences are much lower, i.e., less than 13%. The correlation between the airflow distribution uniformity coefficient and the EAHE seasonal heat gains is presented for exchangers consisting of 3, 5, 7, or 10 parallel branch-pipes. These results can be applied in various energy and economic analyses to estimate the potential energy savings from designing energy efficient building HVAC systems equipped with EAHEs characterized by better airflow distribution.

Numerical Estimation of the Heat and Mass Transfer Efficiency Considering Nonuniformity in Water and Air Distribution

Using a system of differential equations of heat and mass transfer written in a cylindrical coordinate system with volumetric interphase sources of heat and mass transfer, a mathematical model of heat and mass transfer in film blocks of cooling tower irrigators has been developed. Expressions describing the interphase sources of heat and mass transfer and correlations for calculation of their parameters are presented. The parameters of the sources, i.e., the coefficients of heat and mass transfer, are related with the hydraulic resistance of irrigator blocks and can be calculated with both uniform and nonuniform distribution of air and water. The calculated volumetric coefficients of mass transfer were calculated and compared with the experimental data for regular mesh packing made of polyethylene and sheet-type metal packing. The numerical solution of the system of differential equations yielded the distribution of water, air, and air humidity content along the height of a packing block. The thermal efficiency of water cooling was calculated. It agrees satisfactory with the experimental data for spraying blocks made of polyethylene mesh. The causes of nonuniform distribution of phases among the packing blocks, which decreased the thermal efficiency of the cooling tower, were examined. The numerical investigations revealed that nonuniform air supply has the most significant influence decreasing the thermal efficiency of water cooling by as much as 35% or more compared with uniform phase distribution. The presented mathematical model can be used for estimating the cooling capacity of existing cooling towers at thermal power stations (TPSs) and industrial plants as well as in upgrading or developing high-efficient spraying blocks for film-type apparatuses.

Spatial distribution of air temperature and air flow analysis in radiant cooling system using CFD technique

This paper describes the air flow analysis and distribution of a radiant cooling system installed in a commercial building. Computational Fluid Dynamics (CFD) simulations using ANSYS were carried out to identify the thermal performance of the radiant cooling system. The calibration of simulated model was done using the actual data and a hypothetical case of conventional cooling system has been evaluated with the help of TRNSYS for comparative analysis. The CFD simulations were carried out to find the effect of the spatial distribution of air for the radiant system and the conventional system. It was recorded that a radiant cooling system maintains uniform air distribution and better average air temperature as compared to a conventional cooling system. Impact of thermal mass on the fluctuations of the temperature was also studied and it was identified that the higher thermal mass prevents high fluctuations in operative temperatures.

Design and Development of Open Cathode PEM Fuel Cell – Flow Analysis Optimization by CFD

AbstractAir‐cooled polymer electrolyte membrane fuel cells (PEMFCs) have emerged as a potential power generation source, due to its simple construction and operation. Flow‐field designing for the efficient distribution of reactants is of paramount importance in air‐cooled PEM fuel cells. The requirement of flow fields with uniform distribution amounting to minimal pressure drop across the flow area is necessary for high gas utilization and easy removal of water. Thus, the present work deals with the design of land and pillar flow field type for cathode, and further optimization of its flow pattern. A 3‐D computational fluid dynamics analysis tool for modeling fluid flow was used for simulating the reactant distribution profile and finalizing the flow field design. The effect of flow field design, inlet velocity and inlet ports dimension were studied in order to obtain flow pattern with uniform distribution. The optimized configuration showed higher percentage of flow area (76%) with outlet velocities ranging from 3.0–5.5 m s−1 in relation to inlet velocity of 4.4 m s−1. From the results it was inferred that, with the increase of air inlet velocity and modified flow design, the non‐uniform areas occurring in flow field are reduced leading to uniform air distribution throughout the flow volume.

Energetic and exergetic thermal analysis of an inline-airflow solar hybrid dryer

Uniform air distribution inside drying chamber is key factor to reduce energy consumption along with drying uniformity. A detailed thermal analysis (energy and exergy based) was performed for a newly developed inline-airflow solar hybrid dryer (coupled with solar evacuated tube collector and gas burner). The experiments were performed using green chilies at 60 °C under three modes of heating sources i.e. dual (gas + solar), gas and solar. Thermal analysis revealed that energy utilization varied in the ranges of 0–17 kJ/sec (dual), 0–16 kJ/sec (gas), 0–13 kJ/sec (solar), energy utilization ratios were in the ranges of 0–56.8% (dual), 0–60% (gas), 0–47.8% (solar) while values of exergy losses were 2.26–5.41 kJ/kg (dual), 2.45–5.56 kJ/kg (gas) 1.48–4.00 kJ/kg (solar), and exergy efficiencies were in the ranges of 33.95–74.11% (dual), 24–73.58% (gas),17–69% (solar). Heating component that comprised of heat exchanger–evacuated tube collector handled major part of energy possessing higher exergetic factor (54.37) and improvement potential rate (2.016). The values of specific evaporation and product energies were calculated 5.16, 5.77, 4.45 MJ/kg and 22.28, 24.90, 19.19 MJ/kg for dual, gas and solar modes of heating respectively. The study provides a detailed and sequential procedure to conduct thermal analysis of an industrial drying unit employing hybrid source of heating for design assessment and optimization.

ИССЛЕДОВАНИЯ ЭФФЕКТИВНОСТИ РАБОТЫ СИСТЕМЫ ЕСТЕСТВЕННОЙ ВЕНТИЛЯЦИИ МНОГОКВАРТИРНОГО ДОМА

The analysis of existing research in the field of ventilation systems is performed and the current shortcomings of the ventilation systems of secondary apartment houses of series 114–85 are identified. The instability of the natural ventilation system of an apartment building characterized by variable air exchange and overturning ventilation in the ventilation ducts is demonstrated. Field studies of the natural ventilation system efficiency of an apartment house series 114–85 located in Saratov are carried out. According to the research results, the absence of traction and the presence of reverse traction in the exhaust ducts of the ventilation system are revealed. The initial reason for the lack of normal traction in the ventilation system associated with its calculation in the project of building a house series 114-85 for open mode operation is stablished. The increased tightness of windows and doors of apartments is determined, resulting in a reversed traction and the impossibility of uniform distribution of air vertically of the house, therefore installing only the exhaust system of the natural ventilation of an apartment building is inefficient. It is established that the ventilation channel in the kitchen is constantly working to extract air from the premises of the apartments, since the bathroom door is tightly closed that does not correspond to the normative indicators. The analysis of ventilation system on the example of three-bedroom apartments shows the need for additional supply devices for controlled flow of outside air into the premises of apartments. The use of supply wall valves of KIV-125 brand and window ventilation valves of Air Box Comfort brand is provided. A methodology of selection the modern, highly efficient energy saving models of turbo ventilators is presented, increasing traction in exhaust ventilation ducts at 40 % and independent of direction and wind gusts.

(Invited) Development of an Innovative Flat-Metal Separator Integrating the Gdl Formed Gas-Flow Channels and the Analysis As Components of PEFCs

PEFCs are attracting enormous interest with the properties of cleanness and large power density in the wide application areas such as fuel cell vehicles (FCVs) or EneFarms, of which commercialization were already started in 2014 and 2008, respectively, in Japan. It is, however, still essential to reduce the cost of components, such as electrocatalysts, membranes, GDL and separator, by totally ca. 1/10, without losing the cell performances and durability. The cost of GDL plus separator, for example, is predicted to share more than 1/3 in FC systems as well as that of electrocatalysts, even at mass-production stage of the systems. Therefore, we have extensively challenged to develop a less-expensive and corrosion-resistive flat-metal separator coated with thin CB/Resin layer (FMS), and a less-expensive GDL, consist of short carbon fiber (CF) bound with conventional resin, formed gas-flow channels (FC+), named as GDLFC+, and also the integrated product of FMS and GDLFC+, named as FMSG+, in the last 8 years. This development is now promoted as 5 years national project supported by MEXT of Japan. The project targets of FMSG+ for 2021; contact resistance < 10mΩ/cm2 (2020), corrosion resistance ≈ current Au or C-coated SUS or Ti separators and limiting current at cathode > current level×2 (4A/cm2 under ambient air). The cost target of FMSG+/piece is < 2$ (2030), which may bring an assembling cost reduction by the structure integrated above two parts. As these results, we can expect to reduce the cost to a half and improve the performance to double from the stat-of-the-art PEFCs. Flat SUS 304 sheet has been tested to coat tightly with CB/Resin (20-40μm thick) applying various CB and resin. We have achieved 5.7mΩ/cm2 in the contact resistance for this type FMS, lower than 10 mΩ/cm2 of DOE target. No-corrosion were observed over 4,000hrs on optimized FMSs under the soaking in 0.1M H2SO4 solution at 90˚C, which has been used as our accelerated corrosion test on the FMSs since no common test protocol has been shown, serious enough compared to a practical operation condition of PEFCs. We are also testing their durability under the open circuit condition in a PEFC, fed pure H2 and O2 at 90˚C and 100% RH for the comparison with the above liquid-phase test. Various combinations of CF and resin for the GDL have been examined to make balance among the pore size (gas-diffusivity), electric resistance and mechanical strength. Distinctive feature of our approach for the GDLFC+ is the forming of gas-channels in the GDL to make possible uniform distribution of reactant H2 and air over the whole catalyst layers and uniform removing of produced water by forced cross-flow of such reactants and products in GDL and by elimination of the shadow portion against the mass-transportation on the catalyst layer (CL) contacting with ribs of gas-flow channels in the conventional separators. Since this feature is strongly depends on the FC+ patterns, we have tried to create the effective pattern and procedures. Applying a developed GDLFC+, the limiting current of 3.3A/cm2 in the single cell has been achieved under the operation with H2 (UH2=80%) and air (Uair=40%) at 80oC, humidified at 100% RH. For such optimization of GDLFC+ design, in-situ modern visualization methods, applied the phenomena such as the luminescence change on a sensing die depending on O2 concentration [1] or the absorption of neutron beam by H2O, have been used effectively to analyze the flows of the reactant gases or produced liquid water. The results will be shown in the presentation. [1] J. Inukai, K. Miyatake, K. Takada, M. Watanabe, T. Hyakutake, H. Nishide, Y. Nagumo, M. Watanabe, M. Aoki, and H. Takano, Angew. Chem. Int. Ed, 47, 2792-2795 (2008).

Effect of Double-T and V-shaped Pipe Configurations and Perforations on the Quality of Chicken Litter Compost

Livestock waste management has received much attention because of the huge volume and instability. One of the good management practices adopted to address this menace is composting. This study examined the effect of specialized passively aerated composters on some physicochemical properties of chicken litter. The composter is made up of six double T and V shaped pipe with three different perforation diameters of 15, 20 and 25 mm. Pile configuration of the developed composters had marked effect on total nitrogen content (p0.05) of the compost subjected to 90 days composting time. The composters had uniform air distribution as pile temperature was not significantly affected by pile configuration, perforation size, and their interactions. Furthermore, both T and V shaped pipe structures reached a thermophilic temperature of 49.0 and 67 oC respectively and the compost stabilized in the 12th week. From the agronomic point of view, V-shaped pipe outperformed double inverted T pipes with perforation sizes of 15 and 20 mm. Overall result from this study suggests that double-T and V-shaped composters are feasible composting systems that can enhance biodegradation, maturation, and stability of chicken litter.Keyword: compost, litter, composter, double-T, pile, perforation.

Solar Thermal Application for Decentralized Food Baking Using Scheffler Reflector Technology

Baking is an energy intensive unit operation. The thermal application of solar energy is getting attention in food processes by eliminating the facts of interrupted supply and fluctuated costs of nonrenewable energy sources. This study has been carried out for the design and development of solar bakery unit which comprises of a 10 m2 Scheffler reflector focusing all the beam radiations on a secondary reflector that further concentrate the beam radiations toward the heat receiver of solar bakery unit to heat up the air circulated through baking chamber employing a photovoltaic operated fan. Computational fluid dynamic (CFD)-based three-dimensional (3D) simulation was performed to analyze the design for uniform air distribution in the baking chamber. The system designed configurations gave quite good results for airflow distribution. The receiver temperature reached between 300 and 400 °C while temperature at the inlet of baking chamber was in the range of 200–230 °C, sufficient for most of the products to be baked. The maximum available solar power at receiver was calculated to be 3.46 kW having an average efficiency of 63%. A series of experiments were conducted for the baking of cakes and total energy available in baking chamber was about 3.29 kW and cake utilized 0.201 kW energy to be baked. The average value of energy utilization ratio was found to be 45%. As a base, the study would lead to the development of an appropriate and low cost solar baking units for the maximum retention of quality parameters and energy saving.

Effect of primary air maldistribution due to nozzle wear on CFBC performance

As in any fluidized bed application, the nozzle grid of a CFBC riser has the task of supplying fluidization/primary combustion air to the combustion chamber with a uniform distribution and at the same time retaining the coarse ash to form a dense bed at the riser bottom. A typical issue in large scale CFBs is a maldistribution of primary air caused by either excessive nozzle wear in certain grid regions or clogging and blocking on the other hand.The contribution presents a joint method of grid nozzle measurement and CFB combustion simulation for plant performance assessment. Results of erosion patterns and their effect on primary air maldistribution and subsequent combustion issues for a 105MWth CFBC are shown.The method of nozzle grid field measurements combined with detailed flow and combustion computations provides the CFBC operator with information on required number of nozzles to be changed in order to ensure uniform air distribution and at the nozzle grid. As a prerequisite for burn-out quality, boiler efficiency and emission control, the nozzle grid assessment is an effective measure to reduce boiler maintenance costs.

Ultra-low NOx emissions from catalytic hydrogen combustion

The objective of this work is to determine the nitrogen oxide emission in the flue gas of a catalytic hydrogen combustion process, operating without premixed hydrogen and air supply. The study was investigated on a novel designed gas under glass stove top burner, suitable for domestic kitchen applications. The basic catalytic burner assembly consists of two platinum coated silicon carbide (SiC) foam disks with a diameter of 150 mm, a thickness of 10 mm and a porosity of 60 and 80 pores per inch (ppi) respectively. The two catalytic SiC disks are stacked with 10 mm space between for a uniform air feeding and distribution. Hydrogen is supplied from below the assembly and air is blown in between the two Pt coated catalytic SiC disks, leading to a homogeneous air distribution and thus a uniform catalytic reaction of hydrogen and air. Tests are performed at hydrogen flow rates of 5, 10 and 15 Nl/min, equivalent to 0.9, 1.8, 2.7 kW power, the hydrogen to oxygen ratios (φ) were fixed to 0.66, 0.5 and 0.33 respectively. Ultra-low nitrogen oxide emissions of 0.09 ppmv to 9.49 ppmv, equivalent to 0.007 to 0.37 mg/kWh are achieved with this novel developed catalytic combustion design. These values are significantly lower than the present EU regulation of 56 mg/kWh for combustion processes of gaseous fuels for heating applications. This result shows the very high potential of converting hydrogen to heat without harmful exhaust gases for a broad domestic application in decarbonised gas grids or stationary power to gas applications.

Improvement of Air Homogeneity in Paddy Dryer With Central Air Flow Channel

Abstract Air heterogeneity in the drying chamber of the batch-type dryer is a major problem because uneven air distribution within the drying chamber reduces the product quality and dryer efficiency. To surmount this problem, a new dryer with central air distribution model has been designed and developed. This is the distinct design feature of the dryer, which ensure the uniformity in the moisture content of the final dried paddy grains. ANSYS-Fluent (Computational Fluid Dynamics [CFD]) was used to predict the flow behavior of the air with respect to pressure and velocity within the drying chamber by applying actual boundary conditions and standard k−ε turbulence model. Pressure and velocity profiles in the drying chamber were determined using CFD to optimize the drying uniformity. An estimated value for velocity input was used and air distribution was found good. For the validation of simulation results several drying tests were performed at different dryer depths of 18, 36, 54 and 72 cm in the drying chamber. The drying results expressed as percentage moisture content reduction, along the length of the dryer and measured the uniformity in the drying rate. The drying curves for each depth showed high R 2 value. Numerical simulation and experimental results showed that the newly developed solar-assisted paddy dryer is capable to produce uniform air distribution throughout the length of the drying chamber in the dryer for uniform and quality drying. This approach improved the overall performance of the solar-assisted paddy dryer.