Varying Inlet Air Temperature Research Articles

Chemical study of bottom ash sintering in combustion of pelletized residual agricultural biomass

Although residual agricultural biomass is a high-potential energy source, its use is curtailed by the characteristics of its ash (quantity and composition). This ash can cause problems during combustion, including bottom ash sintering, which is the main focus of this study. Results of bottom ash proportion and sintering degree yielded by combustion tests carried out with four different agropellets (one was exclusively woody, and the others were blended with various herbaceous components –mixed agropellets) under different operating conditions in a laboratory fixed-grate reactor were presented in a previous paper. The inlet air temperature and the excess air were the two controlled operating parameters in the tests. To bring the analysis further, samples of bottom ash collected during these tests have been characterized using SEM-EDS and P-XRD techniques. The results confirmed that, given its high content of alkali metals and its high ratio (K+Na)/(Si+P), the differences in sintering behavior presented by the four agropellets are related to the formation of alkali metal silicates and phosphates; Si+P is the limiting and determining content that condition the sintering severity. Regarding the influence of operating conditions, only small variations in the composition of both the sintered and not sintered fractions of the bottom ash have been detected when varying inlet air temperature and excess air in the analyzed range. Nevertheless, these SEM-EDS results have led to the detection of two opposing phenomena related to increased excess air: higher ash entrainment and lower vaporization, which are associated with the increase of air velocity and the reduction of combustion temperature, respectively. Whereas in the mixed agropellets and in the range of excess air tested these two effects offset each other, woody agropellet is significantly affected by entrainment due to its lack of sintered matter. These results provide useful information towards a solution of the problem posed by sintering in the combustion of residual agricultural biomass.

Holistic integration of multi-stage dew point counter flow indirect evaporative cooler with the solar-assisted desiccant cooling system: A techno-economic evaluation

This paper presents a detailed techno-economic assessment along with a performance analysis of various configurations of the solar-assisted desiccant air-cooling system. In holistic integration, multiple configuration variants of solar-assisted desiccant cooling system were considered involving: (1) direct evaporative cooler on both process and regeneration sides; (2) direct evaporative cooler on the process with counter flow indirect evaporative cooler on regeneration side, (3) counter flow indirect evaporative cooler on both process and regeneration sides and (4) direct evaporative cooler on the process side with regenerative side with any evaporative cooler. The technical assessment is carried out to evaluate the performances of all the considered solar-assisted desiccant cooling system configurations. In order to evaluate the economic viability, all setups were tested for a wide range of operating conditions with varying inlet air temperature, humidity, and solar radiation during 15 different selected days of the typical summer season to obtain actual and realistic estimates of systems performances. The seasonal testing results revealed that the first three configurations achieved maximum coefficient of performance values of 0.76, 0.99 & 1.85, and maximum energy efficiency ratio values of 7.19, 8.73, and 13.3, respectively. Utilizing the experimental data, the economic analysis indicates that the third configuration has the potential to save up to 62.9% energy cost compared to the conventional system with a payback period of 5.87 years.

Experimental and numerical studies on dynamic thermal performance of hollow ventilated interior wall

The system integrating hollow ventilated interior wall (HVIW) with solar air collector in residential buildings on Tibetan Plateau facilitates in reducing heating energy use and improving nighttime thermal comfort. In this paper, dynamic thermal performance of HVIW is investigated by experiments and numerical simulations. Experimental results of 3 cases show that heating from the interior wall to the room space lasts during the whole day, and the heat released during the non-ventilation time accounts for more than 40% of the total heat input. Numerical model of this HVIW is validated by experimental results and used to study the influencing factors. Numerical results indicate that the baffle effectively reduces the air short circuit and improves the heat exchange inside the air channel, but resulting in a higher pressure drop. The thicker air channel is averse to the heat transfer inside the channel, while the thicker concrete wall is beneficial to the heat transfer with the increased heat release during the non-ventilation time. With the same ventilation time, the varying inlet air temperature and the intermittent operation significantly increase the total heat released during a whole day and the non-ventilation time. Study of influencing factors in this paper is beneficial to the design of HVIW.

Numerical modelling of a counter-flow regenerative evaporative cooler based on modified effectiveness-NTU method

This study develops a numerical model for a counter-flow regenerative evaporative cooler in Engineering Equation Solver environment by using modified effectiveness-NTU method. The overall performance of the counter-flow heat exchanger was predicted by varying inlet air temperature and humidity.

Investigating Instabilities in a Rotating Detonation Combustor Operating With Natural Gas–Hydrogen Fuel Blend—Effect of Air Preheat and Annulus Width

Abstract Propagation characteristics of a detonation wave in an air-breathing rotating detonation combustor (RDC) using natural gas (NG)–hydrogen fuel blends is presented in this paper. Short-duration (∼up to 6 s) experiments were performed on a 152.4 mm OD uncooled RDC with two different annulus gap widths (5.08 mm and 7.62 mm) over a range of equivalence ratios (0.6–1.0) at varying inlet air temperatures (∼65–204 °C) and NG content (up to 15%) with precombustion operating pressure slightly above ambient. It was observed that the RDC, with an annulus gap width of 5.08 mm, was inherently unstable when NG was added to the hydrogen fuel while operating at precombustion pressures near ambient and at an inlet air temperature of 65 °C. Increasing the annulus gap width to 7.62 mm improved the stability of the detonation wave at similar temperatures and pressure permitting operation with as much as 5% NG by volume. While observed speeds of the detonation waves were still below theoretical values, an increase in inlet air temperature reduced the variability in wave speed. The frequency analysis thus explored in this study is an effort to quantify detonation instability in an RDC under varying operational envelope. The data presented are relevant toward developing strategies to sustain a stable detonation wave in an RDC using NG for land-based power generation.

Effects of fuel variation and inlet air temperature on combustion stability in a gas turbine model combustor

In this study, influences of fuel variation and inlet air temperature on the combustion stability characteristics in a gas turbine model combustor were experimentally investigated. Test fuels involved three selected single component hydrocarbons, including one linear alkane (n-decane), one branched alkane (iso-octane) and one cyclic alkane (methylcyclohexane (MCH)). RP-3 jet fuel was also selected as a technical reference. For all the fuels, experiments were conducted at a fixed equivalence ratio of 0.86 and varying inlet air temperatures from 383 to 483 K. Results showed that RP-3 and n-decane exhibited similar stability behaviors. At low inlet air temperatures, when the combustor was fueled with RP-3 and n-decane, the flame was stabilized and anchored in the combustor. The combustor then shifted to thermo-acoustically unstable state when the inlet air temperature exceeded a threshold value, which was associated by large-scale flame shape variations. On the other hand, noticeable differences can be observed for MCH and iso-octane flames, which featured thermo-acoustically unstable combustion throughout all the tested conditions, and unique mode-shift phenomenon was observed when the inlet air temperature was raised from 403 K to 423 K. Additional flame dynamics was visualized by OH⁎ chemiluminescence imaging. The underlying mechanisms that led to the differences in combustion stability and flame dynamics of the tested fuels were discussed with respect to their differences in physicochemical properties.

Performanse hibridnog fotovoltačnog / toplotnog sušenja u toplo-vlažnom regionu Nigerije

This paper presents a study carried out to investigate the performance of a hybrid photovoltaic/thermal crop dryer in hot humid region of Umuagwo-Ohaji in the South-east region of Nigeria, through energy and exergy analyses, drying, electrical and thermal efficiencies, energy utilization and energy utilization ratio, sustainability indicators such as waste energy ratio (WER), sustainability index (SI) and improvement potential (IP). Drying experiments were conducted at varying inlet air temperatures (50, 60 and 70oC), airflow rates (1.14, 2.29 and 3.43 kgs-1) and slice thicknesses (10, 15 and 20 mm) on 500g batch size of red pepper slices during sunshine periods. Results obtained show that the total and specific energy consumption for drying a batch of sliced red pepper samples varied between 2.08 - 34.91kJ and 7.04 - 62.76 kJkg-1, respectively. The energy utilization and energy utilization ratio during the drying process ranged from 195.75 - 3013.21 Js-1 and 1.82 - 20.4%, respectively. The energy and exergy efficiencies varied between 15.67-38.17% and 26% to 88%, respectively. The mean drying efficiency of the system ranged from 7.12 - 40.27%. The maximum electrical and thermal efficiencies of 23.86% and 93.03%, respectively were obtained. A waste energy ratio of 0.0827 - 0.1579 was obtained, whereas SI and IP values ranged between 1.137 ≤ SI ≤ 6.119 and 0.198 ≤ IP ≤0.583kW, respectively. There is certainly a wide range of improvement in the PV/T system as 12.1 - 18.4 % of the solar irradiance was consumed for drying. Prospects for improvement and recommendations for further studies were suggested.

Increasing energy efficiency in microencapsulation of soybean oil by spray drying

The aim of this study was to evaluate the influence of inlet air temperature of spray drying on microparticles properties and heat loss on drying chamber in sense to select the conditions that promote the preservation of functional compounds and improve energy efficiency. The energy efficiency of the process was evaluated varying inlet air temperature (T) from 110 to 150 °C and airflow (AF) from 20 to 40kg/h, being the energy efficiency, the response variable. The microspheres presented a continuous surface and no cracking, which hinders the diffusion of air and reduces the probability of triglycerides oxidation in the nucleus. The heat loss curves were plotted considering the principles of mass and energy conservation applied to both input and output currents. Further, the thermodynamic parameters were continuously monitored during the spray dryer. So, the selected operational conditions (T = 130 °C, AF = 20 kg.h 1 ) allowed to achieve high encapsulation efficiency (95%) and saving energy compared to conventional processes using inlet air temperatures above 180 °C, a significant improvement to thermo-sensitive compounds.

Fig extract drying: The relationship between the main operating parameters of a pilot-scale spray dryer and product specifications.

This study aims to optimize extraction and drying conditions of fig syrup. Drying was done in a pilot scale two‐fluid nozzle spray dryer. A total of 27 experiments were conducted with varying inlet air temperatures, air flow rates, and also a maltodextrin (MD)‐ low methoxyl pectin (LMP) ratios. While feed rate, feed temperature, and compressed air flow rate of the atomizer were kept constant. The results of differential scanning calorimetry revealed that high levels of glucose and fructose in the extract resulted in a low glass transition temperature of fig syrup. By an increase in the inlet air temperature, the powder bulk density decreased. However, the MD:LMP ratio and the air flow rate were not significantly effective (p < 0/05) in changing the bulk density. SEM micrographs of spray‐dried particles and particle size distribution analysis showed that particles were largely in a range of 5 to 50 μm. The best powders were obtained at an inlet air temperature of 170°C.

A novel multigenerational hydrogen production system: Performance evaluation

The current study discusses the first and second laws analyses of a multi-commodity solar energy-based integrated energy system. The system produces hydrogen in a sustainable manner and supplies 500 MW of electricity, hot water, and hot air for space heating for various applications in sectors. Energy and exergy losses of the plant components are calculated based on a thermodynamic model. Based on the total output work, both energy and exergy efficiencies of the overall system are determined. A parametric study is performed by varying inlet air temperature, air-to-fuel ratio, throttling temperature, and condenser temperature. The results show that increasing pressure ratio increases the efficiency from 66% to 68% over a range of 8–25. Increasing the air-to-fuel ratio increases the energy efficiency from 0.60 to above 0.80, respectively.

Numerical investigation of ethanol fuelled HCCI engine using stochastic reactor model. Part 2: Parametric study of performance and emissions characteristics using new reduced ethanol oxidation mechanism

Ethanol fuelled homogenous charge compression ignition engine offers a better alternative to tackle the problems of achieving higher engine efficiency and lower emissions using renewable fuel. Present study computationally investigates the HCCI operating range of ethanol at different compression ratios by varying inlet air temperature and engine speed using stochastic reactor model. A newly developed reduced ethanol oxidation mechanism with NOx having 47 species and 272 reactions is used for simulation. HCCI operating range for compression ratios 17, 19 and 21 are investigated and found to be increasing with compression ratio. Simulations are conducted for engine speeds ranging from 1000 to 3000rpm at different intake temperatures (range 365–465K). Parametric study of combustion and emission characteristics is conducted and engine maps are developed at most efficient inlet temperatures. HCCI operating range is defined using combustion efficiency (>85%) and maximum pressure rise rate (<5MPa/ms). In HCCI operating range, higher efficiency is found at higher engine loads and lower engine speeds. Emission characteristics of species (NOx, N2O, CO, CH4, C2H4, C2H6, CH3CHO, and HCHO) found in significant amount is also analysed for ethanol fulled HCCI engine. Emission maps for different species are presented and discussed for wide range of speed and load conditions. Some of unregulated species such as aldehydes are emitted in significantly higher quantities from ethanol fuelled HCCI engine at higher load and speed conditions.

ON THE EXPERIMENTAL STUDY OF COMPOSITE DESSICANTS FOR ENERGY EFFICIENT AIR DEHUMIDIFICATION

This paper presents the development and performance characterization of new composite desiccants. The main compositions for the composite desiccants include silica gel, lithium chloride, calcium chloride and bentonite. Different percentage compositions of these four components were tested to determine the optimal material composition for improving moisture removal capacity under varying inlet air temperature and humidity, and amount of moisture released under different regenerative temperature. For the first time, four-layered composite desiccants were developed and tested experimentally to determine their moisture removal capacity and moisture regeneration capacity at temperature of about 60oC under inlet air conditions similar to Singapore’s tropical climate. The performances of these composite desiccants were benchmarked with the performance of pure silica gel - the most commonly used desiccant in the market today. It was observed experimentally, that employing a four-layered composite desiccant, comprising silica-gel (SiO2), Bentonite, Lithium Chloride (LiCl), and Calcium Chloride (CaCl2), has enabled greater moisture removal capacity for varying inlet air temperature and humidity ranging from 25 to 35oC and 55 to 95% relative humidity (RH). The percentage improvements, in contrast to pure silica gel, are 14 to 22.5%, and 10 to 26.3% for varying inlet air temperature and varying inlet RH, respectively. KEYWORDS: experiments; composite desiccant; dehumidification; energy efficiency

Drying of Soybean Seeds in Fluidized Bed: Experimental and Scale-up Simulation in Continuous Operation Mode

The drying curve of the soybean seed (X_in 0.4 kg/kg dry base) was obtained experimentally by fluid bed dryer. The experimental works was performed by varying inlet air temperature (°C): 35; 40; 45, bed mass of particles (kg): 0.2; 0.3; 0.4 and superficial air velocity (m/sec): 7.6; 8.4; 9.1. The drying rate curves as a function of moisture content showed only the decreasing rate period. Among the variables examined, only temperature had a significant influence on the soybean seed drying in fluidized bed. The normalized drying curve of the single particles as well as the critical moisture content (X_cr 0.5) was derived. A simulated continuous fluidized bed dryer for soybean with capacuty 500 kg/h seed had been successfully designed by scale-up method.

The effect of evaporator operating parameters on the flow patterns inside horizontal pipes

A general and simple model for simulating the steady state behaviors of air-to-refrigerant fin-and-tube evaporator is introduced with the focus on the detailed flow patterns inside the tubes. In order to simulate the heat transfer between air and the working fluid, the evaporator is divided into a number of control volumes. Empirical correlations from literature were also adopted to estimate the void fraction, the internal and external heat transfer coefficients, and the pressure drops. Simulations were performed to study the effects of varying inlet air temperature, refrigerant mass flow rate and evaporation pressure on the flow patterns inside the horizontal pipe of the evaporator. The simulation results indicate that the proposed model can be used to predict flow patterns well. The predicted results of the model agree well with experimental results, the difference is within ±3% for the cooling capacity, and is within ±0.2% for refrigerant evaporation temperature.

A 3-D Heat Transfer and Fluid Flow Model for Cooling of a Single Egg under Forced Convection

Shell eggs are cooled under forced convection in commercial egg coolers. They are prone to contamination by pathogenic bacteria such as Salmonella spp., which can grow if the eggs are not properly chilled. Transmission of Salmonella Enteritidis in eggs has been reported, requiring proper chilling of the egg to minimize the risk of foodborne illness. Accurate estimation of egg temperature under various storage conditions would assist egg processing industries to evaluate the adequacy of the egg chilling unit operation to ensure food safety. In order to determine the center temperature of a shell egg under transient forced-air convection cooling, numerical simulations were carried out using a finite volume based computational fluid dynamics (CFD) model. Conduction heat transfer was solved inside the egg, and convective heat transfer was solved at the exterior surface of egg immersed in the fluid domain. Experimental tests were conducted to determine the center temperature of an egg placed inside the test chamber of a wind tunnel by varying the air velocity (0.3 to 1.2 m s-1) and air temperature (3.7°C to 11.4°C) at the inlet of the test chamber. The CFD model was validated by comparing the results with experimental observations. The root mean square error (RMSE) of the egg center temperature predicted by the CFD model varied from 0.2°C to 0.9°C at constant inlet air temperature. Further, the model was also validated for varying inlet air temperature with time. The simulated and experimental values of egg center temperature at various boundary conditions were found to be in good agreement, with RMSE ranging from 0.23°C to 0.37°C. The predicted egg temperatures from the heat transfer model can be provided as an input to a microbial growth model to estimate the potential growth of Salmonella spp. during egg cooling for assessing food safety.

Prediction of Peak Cylinder Pressure Variations Over Varying Inlet Air Condition of Compression-Ignition Engine

Peak cylinder pressure (pmax) of a compression-ignition engine can be affected by the engine inlet air condition, such as its inlet air temperature (Ti) and pressure (pi). The variation of peak cylinder pressure due to varying inlet air temperature or pressure is analytically studied. A model is developed and simplified, and thus the variations of pmax can be predicted along with varying inlet air temperature or pressure. The analysis and prediction indicate that cylinder active compression ratio (CR) and intake air boost ratio (pm0∕pi0) play relatively significant roles in affecting the variation of pmax over inlet air temperature and pressure, and the pressure variation is proportional to CRk and ratio pm0∕pi0. Comparison between the predicted results using the simplified model and those from engine experiments shows a close agreement in both the trend and magnitude. The investigation and prediction also include modeling the variation in pmax due to varying the cylinder TDC clearance volume (Vc). The simplified model is presented and shows that the change in pmax versus varying Vc also depends on the cylinder compression ratio. It is indicated that for a certain change in the clearance volume, a higher compression-ratio configuration would produce a greater change in pmax than a lower one does, especially as the rest of the engine design and operating parameters remain unchanged.

Emission characteristics of marine furnaces burned at varying inlet air temperatures and humidity

Marine power plants are frequently operated under varying atmospheric air temperature and humidity conditions. The effects of inlet air temperatures and humidity of marine furnaces such as incinerators and boilers thus attract much research interest. An industrial furnace incorporated with an automatic burner was employed to experimentally investigate the influences of the inlet air temperature and humidity on the emission characteristics. The inlet air humidity and temperature were adjusted using an air-conditioning machine to preset values before being admitted into the burner. ASTM No. 2D diesel oil was atomized, mixed with the inlet air and burned inside the industrial furnace. Eight small rectangular slots were cut on the upper side of the furnace to allow gas analyzer and thermocouple probes to be inserted into the furnace center to measure the axial variations in the gas temperature, burning efficiency and burning gas compositions such as NO x, SO 2, CO. The experimental results show that the O 2 and NOx emission concentrations decreased while the CO 2 emission concentration and burning efficiency increased with either increasing inlet air humidity or temperature.

Evaporation characteristics of fuel spray and low emissions in a lean premixed-prevaporization combustor for a 100 kW automotive ceramic gas turbine

A lean premixed-prevaporization combustor (PPL-1) for a 100 kW automotive ceramic gas turbine has been developed to meet the Japanese emission standards for passenger cars without using an aftertreatment system. The design of a fuel injector and a prevaporization-premixing tube (PP-tube) in the PPL-1 combustor is a key subject for promotion of evaporation of fuel spray. The Sauter mean diameter and the non-evaporated mass fraction of fuel spray in the PP-tube were measured employing a phase Doppler particle analyzer varying inlet air temperature, air pressure, air velocity and swirl number. The evaporation of the fuel spray in the PP-tube was promoted by higher swirl number, air velocity, air temperature and increased atomization of the fuel injector, but was suppressed by higher air pressure and fuel properties such as distillation in high temperature. The characteristics of NO x , CO and HC emissions were measured with a combustor test rig and discussed influences of the evaporation characteristics of fuel spray. Results show that a mass fraction of non-evaporated fuel of less than 10% and lean fuel-air mixtures, i.e. having equivalence ratios from 0.15 to 0.5, reduce the PPL-1 combustor emissions of NO x and CO.