Air Flow Rate Ratio Research Articles

Statistical modeling and optimization of tannery wastewater treatment in a fluidized bed bioreactor with low density biomass support

Treatment of tannery industry effluent is a serious challenge due to the presence of toxic pollutants including dyes and heavy metals. This work is focused on the optimization of bed height and air flow rate for tannery industry wastewater treatment in a fluidized bed reactor with low density biomass support. Response surface methodology was adopted for the optimization of process parameters viz air flow rate, bed height and wastewater dilution ratio and the best operating conditions were identified. The optimum values for the maximum chemical oxygen demand (COD) removal are: air flow rate—233 LPH, Bed height—82 cm and wastewater dilution ratio—1:2. The results from the IFBR showed that a maximum of 90.2% of COD reduction obtained at an airflow rate of 233 LPH and initial bed height of 82 cm. In this research, a maximum colour removal of 83.4% was achieved. A high correlation coefficient (R2) value of more than 0.94 for all the three models indicates that the RSM based models predict the data well. The relative effect of variables on COD removal, colour removal and air hold up were depicted in perturbation plots.

Effect of the staged secondary air on NOx emission of pulverized semi-coke flameless combustion with coal preheating technology

Coal self-preheating combustion technology has been proved its potential on NOx reduction. This study adopted the technology to mainly investigate the effect of the staged secondary air on NOx emission with two different types of coaxial jet nozzles. Besides, the difference between flameless and flame combustion of the high temperature preheated fuel was also discussed. After being preheated, more than half of nitrogen was released to coal gas, and the released N was mainly converted to N2. It was confirmed that flameless combustion of the preheated fuel (coal gas + coal char) could be easily realized in a coaxial jet triple channel straight nozzle, and (1) the down-fired combustor was transparent without visible flame fronts; and (2) compared with flame combustion, NOx emission was far lower, and the lowest was 50.8 mg/m3 (@6% O2). By comparing the temperature eigenvalues, it was impossible to effectively distinguish between flameless and flame combustion of the preheated fuel. However, it could still be found that T′ (normalized temperature fluctuation) and δT (difference between the maximum temperature and the inlet temperature of the preheated fuel) of flame combustion were always higher than that of flameless combustion, and the differences were enlarged as increasing R12 (ratio of the inner secondary air flow rate to the external secondary air flow rate). With the increase of R12, the exit NOx emission increased first and then decreased whether it was flameless or flame, and the best R12 for NOx emission was about 1.

Durability of Low-PGM Electrodes Under Automotive Drive Cycles

We are evaluating the potential of reaching 8000-h durability of automotive fuel cell systems with a de-alloyed Pt3Co catalyst supported on a high surface area carbon (HSAC) for >440 A/gPt mass activity at a low Pt loading (<0.1 mg-Pt/cm2) for meeting the 30 $/kWe cost target. The supporting experimental data was obtained on a membrane electrode assembly (MEA) operated under differential cell conditions. The MEA has d-PtCo/C in cathode, Pt supported on Vulcan carbon in anode, thin 12-mm reinforced PFSA membrane, and 200-mm GDL with microporous layers. The Pt loadings are 0.1 mg/cm2 in the cathode catalyst and 0.025 mg/cm2 in the anode catalyst.The durability data were obtained by running catalyst accelerated stress tests (AST) for 5k, 10k and 30k cycles. The standard AST protocol consists of trapezoidal cycles with 3-s holds at 0.60/0.95 V lower/upper potential limits (LPL/UPL) and exposure at 80oC and 100% relative humidity (RH). For model development, additional single-variable tests were run at different UPL (0.95 V, 0.90 V, 0.85 V and 0.80 V) and RH (50% and 100%) at 80ᵒC. The ORR kinetics and O2 transport resistances in degraded electrodes were characterized by measuring mass activity and H2/N2 EIS impedance (EIS) at beginning (BOT) and end of tests (EOT) and, in some tests, polarizations curves at different pressures (1-2.5 atm), temperatures (60-95oC), RH (30-100%), and O2 mole fraction (5-21%). In parallel with the differential cell campaign, two-factor interactions were investigated by conducting catalyst ASTs on 50-cm2 cells. In all, 16 tests were conducted for different combinations of UPL (0.95 V and 0.85 V), RH (100% and 40%), temperature (95°C and 55°C), and hold time at UPL (1 s and 5 s) for 30k and 60k cycles. Also, one standard condition (0.9 V UPL, 70% RH, 75ᵒC and 3 s hold time at UPL) was repeated to track reproducibility in each test series.We constructed a durability model that calculates the aqueous dissolution of Pt and Co from a d-PtCo/C catalyst for which online ICP-MS measurements are available as a function of potential cycle parameters. We correlated the calculated Pt dissolution rate to the measured ECSA loss in catalyst AST tests on differential cells at different UPL, temperature and RH. The correlation was validated against the ECSA losses measured in two-variable interaction tests on the 50-cm2 cell.We used the performance and durability models to understand ECSA and voltage losses on urban (UDDS) and highway (HWFET) duty cycles to measure fuel economy of light duty vehicles. These simulations show that the requirement of <10% acceptable degradation in rated power over lifetime can be met by restricting the ECSA loss to 55.3%. A sensitivity analysis shows that potential and RH are the two most important parameters that control electrode degradation. A potential-RH-temperature acceptability map was constructed to determine the envelope of operating conditions for achieving target ECSA loss rate. We used this envelope to guide us in determining the parameters and controls to reach 8,000-h durability on drive cycles in a mid-size vehicle powered by an 80-kWe FCS with a 1.6 kWh battery. We observed that the minimum FCS power (4 kWe) is an important parameter since it determines the peak potential reached during a drive cycle transient. If the power demand falls below 4 kWe, a drive-cycle FC stack shutdown is initiated during which the anode and cathode channels are isolated and electrochemically depleted of H2 and O2. The subsequent stack restart depends on power sharing between FCS and the hybrid battery. We found that the CEM turndown (ratio of air flow rate at rated power and at idle) and cell temperature are important parameters in controlling RH and maximum cell voltage. Figure 1(left) indicates 1,800-h lifetime at the baseline operating conditions, CEM turndown of 20 and 66oC average stack temperature, that lead to 111%/116% average outlet RH in UDDS/HWFET, and cell voltage varying between 760-866 mV. Figure 1(middle) shows that the electrode lifetime can be extended to 5,000 h by reducing the CEM turndown to 12.5 such that the average outlet RH is 90%/102% during UDDS/HWFET, and the cell voltage varies between 760-850 mV. These operating conditions may be benign toward membrane stability. Reaching 8,000-h electrode lifetime requires the CEM turndown to be further lowered to 10 and the average cell temperature to be raised to 70oC, see Fig. 1(right), so that the average outlet RH is 52%/78% during UDDS/HWFET, and the cell voltage varies between 760-825 mV. These dry operating conditions may prove challenging to membrane stability and require further investigation. Figure 1

Flow and aeroacoustic characteristics evaluation of microjet noise reduction concept in the nozzle design for minimum quantity lubrication

Minimum quantity lubrication (MQL) is an efficient and sustainable technology, which has been considered to be an option of conventional flood cutting process. Even though MQL provides green solution for the cooling and lubrication function during machining, it brings about unendurable aeroacoustic jet noise from the high velocity spray. The acoustic pollution has seriously affected the operator's health and efficiency so that it should be paid much attention to. In this paper, with the utilization of microjets noise reduction concept, a noise cancellation accessory for MQL nozzle has been developed. The flow field and aeroacoustic characteristics of the original nozzle and microjets have been investigated numerically to help understand the noise reduction mechanism. Variables including the main jet flow rates, the air flow rate ratios of the microjets to the main jet and the measuring azimuths on noise directivities and sound pressure level (SPL) have been analysed. It has found the flow ratio is a critical parameter, which has an optimal value in regard to the main jet flux. The simulation results have been partially verified through OASPL measurement. The overall aeroacoustic noise reduction varied from 0.70 to 4.88 dB has been observed experimentally. Finally, the noise cancellation mechanism has been discussed from the flow field and the frequency characteristics points of view. The shrinking effect of microjet injection at appropriate air flow ratios has significantly narrowed the distribution of the turbulent intensity and reduced the SPL of low and medium frequency while increased that of the high frequency in specific directions. The overall amplitude of OASPL has been reduced. However, inappropriate air flow ratios will generate additional jet noise.

Fresh air humidification in winter using desiccant wheels for cold and dry climate regions: Optimization study of humidification processes

• Analyzing efficient fresh air humidification methods for buildings in cold and dry climate regions. • Multi-stage desiccant wheels with separate dehumidification air improve system performance. • Control strategies are discussed, showing an over 95 % satisfactory rate, under Urumchi condition. • When natural gas boilers are used, heating system efficiency can be around 2 with heat recoveries. Efficient fresh air humidification methods for buildings located in cold and dry climate regions are discussed in this paper. Air handling units that use desiccant wheels to realize air humidification are studied. Optimization analysis is carried out for three types of air handling units under different ambient humid ratios and effects of desiccant wheel facial area ratios ( A r ) between dehumidification air and humidification air, air flow rate ratio between dehumidification air and humidification air ( F r ), rotation speed ( RS ), stage number etc., are discussed. Based on the optimization results, an air handling unit that has 3 stages desiccant wheels and 3 streams dehumidification air is proposed. For this device, A r is 3 for each desiccant wheel and F r can be adjusted from 1 to 9. It can satisfy fresh air humidification in a wide range of ambient conditions. Based on this device, two control strategies are discussed based on Urumchi winter ambient conditions. The satisfactory rate is over 95%.

Deposition fraction of ellipsoidal fibers in the human nasal cavity- Influence of non-creeping formulation of hydrodynamic forces and torques

In this study, the deposition of fibrous particles in a realistic 3D model of the right nasal cavity of a 24-years-old woman was simulated using the non-creeping formulations for hydrodynamic forces and torques. The Lagrangian trajectory analysis approach within the Ansys-Fluent software was used for these simulations. Several user-defined functions (UDFs) for solving the coupled translational and rotational motion of an ellipsoidal fiber and for evaluation of non-creeping forces and torques were developed and were incorporated in the Ansys-Fluent DPM. The passage included the main nasal cavity from the nostril to the beginning of the nasopharynx. Both laminar and turbulent steady inhalation breathing conditions were assumed, and for turbulence modeling, the Realizable k-ε model was employed. It was assumed that the airflow was incompressible. The breathing rates of 2.5, 5.0, 7.5, and 10 lit/min per nostril were considered for laminar airflow corresponding to the rest or light physical activity conditions. For turbulent airflow, the breathing rates of 15, 20, and 30 lit/min were assumed for high physical activities. The transport and deposition of fibers of different sizes and aspect ratios in the nasal cavity under laminar and turbulent airflow regimes were investigated.The simulation results showed that the increase of air flow rate, fiber diameter, and aspect ratio led to the increase of deposition in the human nasal cavity. In addition, the use of forces and torques estimated from the more accurate non-creeping flow estimation led to somewhat lower particle deposition in the nasal cavity compared to those obtained from the simplified creeping flow assumption.

β-Cyclodextrin and ultrasound-assisted enzyme renaturation for foam fractionation of laccase from fermentation broth of Trametes hirsuta 18

Foam fractionation is a cost-effective method to separate laccase from its fermentation broth. However, the enzyme readily suffered a substantial activity loss in the separation process. To reduce the activity loss, we firstly analyzed the structure-function relationship of laccase to explain how laccase was denatured in the foam fractionation of laccase from fermentation broth of Trametes hirsuta 18 using cetyltrimethyl ammonium bromide (CTAB) as a collector. The results demonstrate that via electrostatic force, CTAB interacted with laccase molecules to cause their structural unfolding, so CTAB resulted in the denaturation of laccase. Increasing the molar ratio of CTAB vs laccase at the gas-liquid interface over that in the feed solution, foaming enhanced the CTAB-induced denaturation. On this ground, we attempted to use β-cyclodextrin and ultrasound to assist the refolding of laccase denatured jointly by CTAB and foaming in the foamate. Ultrasound effectively assisted the renaturation of denatured laccase after it was separated from CTAB by β-cyclodextrin in 40 min at 20 °C or lower. Furthermore, their renaturation performances highly depended on pH, volumetric airflow rate, CTAB concentration and molar ratio of β-cyclodextrin vs CTAB in the foamate. At pH 6.0, volumetric airflow rate 60 mL/min, CTAB concentration 0.4 g/L and molar ratio of β-cyclodextrin vs CTAB in the foamate of 1.6:1, the enrichment ratio and recovery yield of laccase activity and purification fold of laccase reached 73.4%, 11.9 and 3.5, respectively. They were 230% higher than those without β-cyclodextrin and ultrasound. Therefore, ultrasound and β-cyclodextrin effectively enhanced the CTAB-assisted foam fractionation of laccase from the fermentation broth of T. hirsuta 18. In addition, a SDS-PAGE analysis determined that laccase of 55 kDa in molecular weight was highly enriched by the foam fractionation.

Aspen Plus simulation and optimization of industrial spent caustic wastewater treatment by wet oxidation method

Spent caustic is a waste generated by petrochemical refineries, which used to eliminate acid components such as hydrogen sulphide (H2S) and mercaptans from the refined product streams. A study was carried out on simulation and optimization of spent caustic wastewater treatment system by using Aspen Plus based on wet air oxidation (WAO) method. WAO method uses air under elevated temperature and pressure to carry out oxidation in the aqueous phase. Process flow diagram (PFD) of WAO method was drawn and relevant input data was keyed in Aspen Plus according to experimental results on WAO. Both results were validated and the results were match each another as the percentage of allowable error between both the results were less than 5 %. After that, optimization was carried out to determine the optimum ratio of spent caustic feed flow rate to air flow rate and operating temperature of the flash separator unit involved in the process. From the optimization results, it can come to a conclusion that 1: 9.2 is the minimum spent caustic feed flow rate to air flow rate ratio and optimum operating temperature of flash separator unit is 140°C in order for maximum flow rate of CH3SSCH3 in offgas stream in this simulation model of spent caustic wastewater treatment system using WAO method.

Investigating the nasal cycle using unilateral peak nasal inspiratory flow and acoustic rhinometry minimal cross-sectional area measurements.

To plot the nasal cycle using unilateral peak nasal inspiratory flow (UPNIF) and unilateral minimal cross-sectional area (UMCA) readings demonstrating a linear relationship in normal nasal function. Additionally, to determine how this changes in abnormal nasal function. A cross-sectional study measuring UPNIF and UMCA in controls demonstrating normal nasal function and in patients with nasal obstruction. Royal National Throat Nose and Ear Hospital, London. A total of 39 participants, 26 controls and 13 patients, were recruited. Controls exhibited normal nasal function with SNOT-22 <5. Patients nasal obstruction symptoms secondary to inflammation or structural abnormality with SNOT-22 >9. Airflow rates and resistance values were derived from UPNIF and UMCA measurements respectively based on Poiseuille's laws. Ratios between right and left UPNIF and UMCA values were taken to adjust for confounding factors. The relationship of 1/Resistance Ratio and Airflow Rate Ratio demonstrated a linear of direct proportionality of strong correlation and statistical significance (correlation coefficient=0.76, P«0.01). This suggests that data points from controls with a normal nasal cycle lie closely along the regressed line, whilst those lying significantly away were shown to belong to patients with nasal dysfunction. Olfactory dysfunction appears to be a sensitive discriminator in predicting this. This study demonstrates the directly proportional relationship of 1/Resistance Ratio and Airflow Rate Ratio in normal nasal function. Furthermore, nasal pathology can be predicted if data points lie significantly outside these normal limits. Further studies are needed to validate exact normal and abnormal thresholds.

An evaluation of turbulence and tile models at server rack level for data centers

In recent decades, computational tool is popularly used for thermal management of large data centers to meet the high demand of IT services which causes an increase in thermal load density. In this study, an evaluation of various available tile models at different tile-to-rack airflow rate ratios is carefully conducted using experimental data for one single server rack in a dada center laboratory from the available literature. In addition, several turbulence models are thoroughly studied, and recommendations are provided for the most accurate and less time-consuming turbulence models depending on targeting purposes when applying to a single rack model. A proposed composite performance index is introduced and used for evaluating various tile and turbulence models. It is an interesting finding that the zero-equation produces a very decent result when compared to the widely used standard k-ε. As for the tile model investigated, it is found that the body force and modified body force model are the best candidates for tile modelling applications. The use of zero equation with either body force or modified body force tile model yields either an equivalent or better results in terms of time and accuracy compared to the standard k-ε case combined with the same tile models.

Experimental study of an ultrasonic regenerative evaporative cooler for a desiccant cooling system

This paper presents fabrication of an ultrasonic regenerative evaporative cooler, coupled with a desiccant dehumidifier. Ultrasonic regenerative evaporative cooler consists of several sets of a dry channel and a wet channel. A part of the air from the dry channel is redirected into the wet channel where it is cooled by evaporation of water mist from an ultrasonic atomiser. Air flowing through dry channels is pre-cooled by heat transfer between wet and dry channels, without changing its humidity. In this cooler, the conventional hygroscopic layer for wetting the plate surface is replaced with the water mist. It is observed that the performance of the cooling system significantly depends on the channel spacing, channel length, inlet airflow rate and extraction ratio, and marginally depends upon feed water temperature. The room cooling capacity is eminently responsive to both air mass flow rate and extraction ratio. The maximum available room cooling capacity of 339.8 W is obtained for the optimal values of 0.0488 kg/s mass flow rate of air and 0.37 extraction ratio. The prototype achieved wet-bulb effectiveness values as high as 1.15 and delivered more than 10℃ temperature drop. Practical application: An ultrasonic regenerative evaporative cooler can be coupled with a desiccant dehumidification unit for use in hot and humid climate to achieve comfort condition utilising less energy and feed water when compared to the vapour compression refrigeration system. From this prototype researchers and engineers can develop, by combining desiccant regenerators and evaporative coolers which use ultrasonic method for low-temperature dehydration of desiccant substance. Solar thermal energy can also be directly utilised for marginally heating the desiccant substance during the regeneration process. Overall, this system can contribute to the development of energy efficient buildings.

Research on tunnel ventilation systems: Dust Diffusion and Pollution Behaviour by air curtains based on CFD technology and field measurement

In order to further improve an air curtain's dust suppression performance in tunnels, this paper made an in-depth analysis of the effects of an air curtain generator's radial and axial pressure airflow rate and a dust removal fan's exhaust airflow rate on the diffusion and pollution behaviors of dust. Through CFD Technology and field measurements, it can be observed that: when the air curtain generator's axial-to-radial pressure airflow rate ratio (Ra/r) varied within the range of 1/9–6/4, the diffusion distance of high-concentration dust (with a concentration over 10 mg/m3) decreased with the decrease of Ra/r; and when Ra/r = 1/9, the formed airflow curtains exhibited the most favorable dust suppression performance. In addition: when the dust removal fan's exhaust-to-pressure airflow rate ratio (Re/p) increased, the diffusion distance of high-concentration dust decreased; and when Re/p = 1.2, the dust produced could be suppressed effectively by the air curtains. Finally, field measurements reveal that when a dust removal fan with a Re/p of 1.2 and an air curtain generator with a Ra/r of 1/9 were used in combination, high-concentration dust can be controlled fully within a range of 5.49 m from the head-on section by the formed air curtains, and the average dust concentration in the region 5–50 m away from the head-on section in tunnel was reduced to 9.82 mg/m3; i.e., the excavator driver and workers can be protected effectively.

Experimental investigation on the flow-induced vibration of a free-hanging flexible riser by internal unstable hydrodynamic slug flow

Unstable hydrodynamic slug flow is extensively encountered in marine risers, resulting in internal flow-induced vibration, which is quite different with the vortex-induced vibration caused by a cross flow. Experiments were performed in an air-water test loop to study the internal slug flow-induced vibration of a free-hanging flexible riser with aspect ratio (the ratio of the length to the diameter of a riser) of 158. A non-intrusive technique of high speed imaging method was employed to record the vibration displacements of the riser model and the flow regime of two-phase mixture in the riser simultaneously. The results show that an in-plane vibration is created by the internal slug flow, and the responses along the two directions in the plane are interdependent to each other. In the considered gas-liquid ratio (the ratio of air flow rate to water flow rate), the second-order mode dominates the response. The hydrodynamic behaviors of slug flow, including the gas-liquid ratio, liquid slug length and superficial velocity, affect the local pressure fluctuation and hence influence the vibration amplitude. The fluid-structure interaction is reflected from the same frequencies presenting in the vibration and pressure fluctuation.

Techno – economic analysis of ventilation driven through solar metallic wall for a hostel building of National Institute of Technology Raipur India

The aim of present work is to investigate theoretically the ventilation flow rate produced using solar metallic wall system. In this effort, the effect of various design parameters on the performance of solar metallic wall system is evaluated under the climatic condition of Raipur (21.2514° N, 81.6296° E), Chhattisgarh. A computer simulation program based on the mathematical model of proposed system has been developed using MATLAB software. The performance of solar metallic wall system is evaluated by predicting the volumetric air flow rate. The effect of air gap, height and different metallic sheets are determined. It has been observed that with increase in air gap and height, volumetric air flow rate increases, about 203 % increase in volumetric air flow rate is observed for increase in air gap from 0.1 m to 0.5 m and 57 % increase in volumetric air flow rate is observed for increase in height from 1 m to 2 m. The best performance of solar metallic wall system is observed on using aluminium as metallic sheet as compared to the other chosen materials. The ratio of volumetric air flow rate obtained for iron, copper, and aluminium is 1, 1.11, 1.45 that shows, volumetric air flow rate for ventilation by metallic wall of aluminium is about 45% more than its competitor. Finally the system is proposed for a hostel of NIT Raipur and it is concluded that 3024 kWh per year of energy is saved if solar metallic wall is used in place of conventional electrical system. The amount of carbon-dioxide emitted to atmosphere is also reduced by 0.02 tonne per year. The payback period of total solar metallic wall units required in place of exhaust fans to completely ventilate the hostel building during day hours is coming out to be 7 years and 8 months.

Overall cooling effectiveness of effusion cooled annular combustor liner at reacting flow conditions

A three-sector annular combustor test rig is built to carry out experimental investigation on the liner effusion cooling performance using steady state infrared radiation thermography method at reacting flow conditions. 7 rows of effusion holes in a staggered layout are distributed on both inner and outer liner bended testing plates, where the temperature field is captured and overall cooling effectiveness is analyzed. Coolant-to-main air flow rate ratio and equivalence ratio are varied to evaluate their effects on the cooling effectiveness. Three axial nozzles generating representative high swirling flows are fueled by methane-air mixture to perform premixed combustion. Besides, results for effusion holes in different inclination angle (90° and 30°) are compared. The results indicate that a region with low overall cooling effectiveness on the both liners for normal effusion holes due to the swirling flame impingement effect. Because of double length-to-diameter ratio, inclined holes at 30 degree perform better cooling protection than the normal holes. The variation of equivalence ratio induces the change of the flame pattern, temperature field and flow field, which will have an impact on the liner effusion cooling in consequence.

Design and development of an air humidifier using finite difference method for a solar desalination plant

Humidifier is an important component in air humidification-dehumidification desalination plant for fresh water production. Liquid to air flow rate ratio is optimization is reported for an industrial cooling towers but for an air humidifier it is not addressed. The current work is focused on the design and analysis of an air humidifier for solar desalination plant to maximize the yield with better humidification, using finite difference method (FDM). The outlet conditions of air from the humidifier are theoretically predicted by FDM with the given inlet conditions, which will be further used in the design calculation of the humidifier. Hot water to air flow rate ratio and inlet hot water temperature are identified as key operating parameters to evaluate the humidifier performance. The maximum and optimal values of mass flow rate ratio of water to air are found to be 2.15 and 1.5 respectively using packing function and Merkel Integral. The height of humidifier is constrained to 1.5 m and the diameter of the humidifier is found as 0.28m. The performance of humidifier and outlet conditions of air are simulated using FDM and compared with experimental results. The obtained results are within an agreeable range of deviation.

The influence of chilled water on the performance of direct evaporative cooling

In this paper, the performance of direct evaporative air cooling (DEC) was investigated with chilled water. This may increase the performance of DEC, especially in humid weather, as the air wet-bulb temperature reduces during the cooling process. The efficiency of DEC was determined by a performance factor instead of the saturation efficiency. A prediction model based on heat and mass balance between air and water was developed. For this model, the condition line of cooling process was divided into segments for which the enthalpy of air was gradually decreased. The influence of dry-bulb temperature of entering air, relative humidity, water subcooling and air-water mass flow rate ratio on the performance factor was taken into account. Experiments were performed for the verification of the predicted data. It could be shown that the mass flow rate ratio is the most effective parameter on the performance of DEC. The performance of DEC can be significantly increased by chilling water and by decreasing the mass flow rate ratio even when the air humidity is relatively high. This may enable the potential application of DEC in very humid weather areas. The mean absolute percentage deviation between experimental and predicted performance factor was 15.1%.

Syngas production from CO2/CH4 rich combustion in a porous media burner: Experimental characterization and elementary reaction model

Methane and carbon dioxide are two major components in many biomass-derived gases such as landfill gas and biogas, which are renewable and have potential fuel cell applications. Syngas production from non-catalytic and fuel-rich combustion using a two-layer porous media burner was studied experimentally and numerically with a range of CO2 content in the CH4 fuel. With an air flow rate of 5L/min, an equivalence ratio of 1.5 and a mole ratio of CO2/CH4 of 1, the reforming efficiency was found to be 45.3%, larger than that (39.1%) without CO2 in the feed at the same air flow rate and equivalence ratio. A two-dimensional model with an elementary reaction mechanism was developed to study the influence of carbon dioxide on the reforming characteristics. The model is validated by the experimental results with good agreement. The simulation results clearly showed that the reaction process along the burner could be divided into a preheating zone, a CO2-consuming zone and a CO2-generating zone according to the net reaction rate of CO2.

OPTIMIZATION OF PROCESS PARAMETERS OF PRESSURE-SWING ADSORPTION CYCLE IN A SILICA GEL DESICCANT DEHUMIDIFICATION SYSTEM

Parametric study on pressure-swing adsorption cycle desiccant dehumidification system is a continuous engineering task with the aim of analyzing its effects and attains target quality of dry air for an industrial process. An experimental setup is developed with a dehumidification tower, regeneration tower,and flow control valve.The effect of process air inlet moisture content, cycle time ratio, and regeneration air flow rate on the adsorption performance is studied to evaluate the potential of the dehumidification system suitable for drying applications. The optimal dehumidification parameters are found, and a regression equation is also developed for the process. It is concluded that, process air inlet moisture is the most influencing parameter compared to regeneration air flow rate and cycle time ratio for the silica gel desiccant dehumidification system.

Analysis of freeze protection methods for recuperators used in energy recovery from exhaust air

In this study theoretical analysis of the heat and mass transfer in counter-flow recuperators used for energy recovery in air handling units (AHU) under sub-zero outdoor air temperature operating conditions is presented. The most probable variants of year-round heat exchanger operation performance, which characterized by existence of three active heat and mass transfer zones ( “dry”, “wet”, “frost” ), and effect of the latent heat of water vapour condensation on the realization of these variants was determined. It was established, that the frost tends to take place with increasing temperature effectiveness of the heat exchanger. Two main techniques of the frost prevention (preheating and bypassing the outdoor airflow) were described and analysed. The values of critical outdoor temperatures and outdoor-to-return airflow rate ratio were determined on the base of parametric frosting limits analysis conducted under different inlet return airflow conditions. The comparison of the heat recovery efficiency and additional energy consumption for the air treatment in the AHU is presented.