Incoming Air Research Articles

Numerical investigations and performance comparisons of a novel cross-flow hollow fiber integrated liquid desiccant dehumidification system

The heat and mass transfer process of a novel cross-flow hollow fiber integrated liquid desiccant dehumidification system is analyzed numerically. Compared with other porous media or packing towers in dehumidification applications, hollow fibre membranes have significant advantages including low weight, corrosion resistance and no liquid droplet carryover. A novel air-KCOOH cross-flow dehumidification system was designed and manufactured, with 5500 hollow fibres formed into a circular module. The variations of the dehumidification effectiveness and moisture removal rates were studied numerically and validated against experimental results under the incoming air mass flow rates of 0.08–0.26 kg/s and relative humidity from 55% to 75%. The dehumidification performance comparisons for the proposed system using CaCl2, LiCl and KCOOH as the desiccants have been conducted. The results demonstrated that under the same m*(ratio between solution mass flow rate to the air mass flow rate), the proposed system using 62% KCOOH could achieve approximately the same latent effectiveness compared with 40% CaCl2 and 32% LiCl, with at least 3.1% sensible effectiveness improvement. Therefore, it could be concluded that the proposed system using KCOOH as desiccant could be more applicable for dehumidification purpose compared with other systems using conventional liquid desiccants.

Energy efficiency of exhaust air heat recovery while controlling building air humidity: A case study

One modern method of lowering building energy use is heat exchange between outgoing and incoming air. Exhaust air moisture (partly) condenses in the heat exchanger, giving liquid water to be removed. With low absolute humidity of inlet air especially at low outdoor temperatures, a significant drying effect results for the air inside the building. Increasing air humidity by, for example, spraying water or increasing watering of plants will give an energy penalty. This paper presents an analysis of the energy efficiency (recovered versus input exergy) of a modern house equipped an exhaust air heat recovery system and external heating supplied by a geothermal heat pump. Indoor temperature is 22 °C and relative humidity is 50 or 30%. Temperature and humidity of inlet air and ventilation flow rates are variable and the effects on power use by the heat pump are assessed. Results show that without moisture recirculation a water loss up to 1 kg/h from the building may occur. Several kWh of electricity may be consumed daily by a (geothermal) heat pump supplying heat depending on outdoor temperature, and indoor and outdoor air humidity. Besides water consumption, this may imply 10–15% of total electricity use.

Evaluating improvements in a waste-to-energy combined heat and power plant

Evaluation of different alternatives for enhancement in a waste combustion process enables adequate decisions to be made for improving its efficiency. Exergy analysis has been shown be an effective tool in assessing the overall efficiency of a system. However, the conventional exergy method does not provide information of the improvements possible in a real process. The purpose of this paper is to evaluate state-of-the art techniques applied in a municipal solid-waste fired heat and power plant. The base case plant is evaluated first; the results are then used to decide upon which technical modifications should be introduced and they are thereafter evaluated. A modified exergy-based method is used to discover the improvement potential of both the individual components and the overall base case plant. The results indicate that 64% of exergy destruction in the overall process can theoretically be improved. The various modifications selected involve changing the bed material, using a gasifier followed by a gas boiler and incorporating a more durable material into the boiler walls. In addition, changing the heating medium of the incoming air (from steam to flue gas) along with a reduction in the stack temperature and the integration of flue gas condensation were considered for utilizing the exergy in the flue gases. The modification involving gasifier, gas boiler and flue gas condensation proved to be the best option, with the highest exergy efficiency increment of 21%.

Exergetic and Energetic Analysis of a Traditional Semi-Industrial Comorian Ylang-Ylang Essential Oil Wood Fire Distiller

In this article a study of the energy performance of a distillation system of ylang-ylang essential oil on a wood fire was carried out. To do this an analysis using the first and the second low of thermodynamics was made for each component of the distillation system. The analysis showed that the energy efficiency depends on the fration of oil to be distilled and that the whole system is very deficient. The exergetic and energetic analysis shows that it is in the combustion chamber that has a large amount of destroyed exergy and a strong energetic loss. The velocity of the air entering at the combustion chamber greatly influences the efficiency of the chamber. Indeed it has been found that the destruction of the exergy increases with the velocity of the air incoming air.

Exergetic and Energetic Analysis of a Traditional Semi-Industrial Comorian Ylang-Ylang Essential Oil Wood Fire Distiller

In this article a study of the energy performance of a distillation system of ylang-ylang essential oil on a wood fire was carried out. To do this an analysis using the first and the second low of thermodynamics was made for each component of the distillation system. The analysis showed that the energy efficiency depends on the fration of oil to be distilled and that the whole system is very deficient. The exergetic and energetic analysis shows that it is in the combustion chamber that has a large amount of destroyed exergy and a strong energetic loss. The velocity of the air entering at the combustion chamber greatly influences the efficiency of the chamber. Indeed it has been found that the destruction of the exergy increases with the velocity of the air incoming air.

The experimental and simulation study of an earth-air heat exchanger in Medan city

The earth-air heat exchanger (EAHE) is an air-conditioning device utilizing a heat exchange between the air in the room and the soil. This paper purpose to determine the EAHE performance with experimentally and simulation. The simulation used are transient CFD, turbulent and 3-dimensional. The ambient air was distributed to the pipes with the different velocity of 2 m/s and 3 m/s. It was found that the earth-air heating exchanger effectiveness at air velocity 2 m/s for testing was 0.84 while for theoretical of 0.97. The coefficient of performance (COP) of EAHE increase from 1.341 to 1.761 when the increasing air velocity from 2 m/s to 3 m/s. The COP value also increases from 1.473 to 2.278 at the increasing of air velocity from 2 m/s to 3 m/s. The average of the COP value of the simulation result of the incoming air velocity was 1.99422 for velocity 3 m/s and 1.41426 for the velocity 2 m/s. For the average effectiveness of the simulation result obtained 1.00074 for the velocity of 3 m/s and 0.86100 for velocity 2 m/s.

Association between air travel and importation of chikungunya into the USA.

Abstract Background: During infectious disease outbreaks with pandemic potential, the number of air passengers travelling from the outbreak source to international destinations has been used as a proxy for disease importation risk to new locations. However, evaluations of the validity of this approach are limited. We sought to quantify the association between international air travel and disease importation using the 2014–2016 chikungunya outbreak in the Americas as a case study. Methods: We used country-level chikungunya case data to define a time period of epidemic activity for each of the 45 countries and territories in the Americas reporting outbreaks between 2014 and 2016. For each country, we identified airports within or proximate to areas considered suitable for chikungunya transmission and summed the number of commercial air passengers departing from these airports during the epidemic period to each US state. We used negative binomial models to quantify the association between the number of incoming air passengers from countries experiencing chikungunya epidemics and the annual rate of chikungunya importation into the USA at the state level. Results: We found a statistically significant positive association between passenger flows via airline travel from countries experiencing chikungunya epidemics and the number of imported cases in the USA at the state level (P < 0.0001). Additionally, we found that as the number of arriving airline passengers increased by 10%, the estimated number of imported cases increased by 5.2% (95% CI: 3.0–7.6). Conclusion: This validation study demonstrated that air travel was strongly associated with observed importation of chikungunya cases in the USA and can be a useful proxy for identifying areas at increased risk for disease importation. This approach may be useful for understanding exportation risk of other arboviruses.

A manufacturing process design for producing a membrane-based energy recovery ventilator with high aspect ratio support ribs

Heating, ventilation, and air conditioning systems represent nearly half of building energy usage in the United States. Recent building regulations requiring increased air turnover within buildings will result in even greater air conditioning usage. To alleviate these concerns, membrane-based heat-and-moisture exchangers known as energy recovery ventilators have been developed to reduce the energy expenditure of air conditioning systems by pre-conditioning incoming air through sensible and latent heat transfer with building air exhaust. In this work, we propose and validate a manufacturing process design for channel lamination based on surface mount adhesives capable of meeting the process requirements of a membrane-based ventilator. In particular, the device requires rib supports with height-to-width aspect ratios greater than one. The proposed manufacturing process design is capable of meeting this process requirement by stretching the adhesive after initial adhesive tacking. A manufacturing process flow diagram, a machine tool specification and a cost model are proposed for meeting process requirements. A set of design constraints are developed detailing the adhesive requirements necessary for meeting requirements. The cost model is validated by building a sub-scale mesochannel array demonstrating the ability to meet process requirements. Results show that additional work is needed to validate the curing step but that the process is capable of producing a mesochannel array with an acceptable level of variation.

Regulators seek ways to down rogue drones: Growing antidrone industry offers radar, remote ID, and other tools - [News

Drone sightings at London's Gatwick Airport disrupted operations there for three days last December, and in January, rumored sightings near Newark [N.J.] Liberty International Airport delayed incoming air traffic temporarily. These incidents highlighted a growing problem with small drones: Miscreants, or just clueless operators, can make real trouble by flying these machines where they're not allowed.

Investigation of the flow structure and heat transfer intensity of surfaces with split plate finning

The authors use CFD modeling to study three types of heat exchange surfaces, i.e. a basic plate fin surface and two modified split plate surfaces – without rotation and with rotation of the split sections at an angle of 30° against the incoming air flow. Thermal aerodynamic characteristics of the studied heat exchange surfaces are obtained and verified with experimental data. The flow patterns are presented in three sections along the height of the channels in the finned area. An explanation is offered for the intensification of heat transfer in the modified heat exchange surfaces. It is shown how geometrical and operating parameters influence the heat transfer intensity and aerodynamic resistance. The results can be useful in designing cooling systems for electronics, particularly microprocessor and microlaser devices, power amplifiers of transmitting modules for radar systems, promising energy-saving solid-state light sources, power electronics for electric vehicles, equipment for aviation and space-rocket electronics with heat pipes.

Experimental investigation on upstream fuel injection technique of RBCC scramjet mode

Upstream fuel injection in the inlet/isolator is a promising fueling strategy for the reliable operation of rocket-based combined-cycle (RBCC) engine scramjet mode, where fuel must be injected and mixed with the air in an extremely short time. A ground direct-connect test system was used to simulate the condition of incoming air and the combustion in combustor. Experiments have been conducted to investigate the upstream fuel injection of heated/non-heated kerosene at Mach 5.5, and appropriate fuel injection strategy has been proposed according to the result. An observation window was installed at the combustor wall surface to study the flame propagation. The attained results reveal that high combustor pressure and efficient combustion can be achieved by upstream fuel injection coupled with the injection of pylons positioned downstream for non-heated kerosene, while high combustor pressure can be achieved by only upstream fuel injection with heated kerosene. Resident flame can be formed and hold between the central strut base and pylons when the primary rocket is turned off.

Assessment of NOx emissions of the Scimitar engine at Mach 5 based on a thermodynamic cycle analysis

The Scimitar engine is a new advanced propulsion system designed to propel the aircraft A2 of the LAPCAT project. It is a hybrid system that utilizes the features of turbofan, ramjet and air-turborocket. Hydrogen and air are used as the fuel and oxidant, respectively, while helium is used to transfer heat from the hot incoming air to the hydrogen in the engine. In this study, we present a thermodynamic cycle analysis of the Scimitar engine for the assessment of NOx emissions. The combustion of fuel is studied in detail with an equilibrium model taking into account various dissociation and formation reactions since high levels of temperatures are achieved in its combustion chamber. The NOx emissions of the engine at Mach 5 and the effects of fuel and air flow rates, cruise speed and altitude on these emissions are presented by solving a nonlinear system of equations formed through our novel thermodynamic model. The results show that the NO emissions of the engine can be diminished significantly by decreasing air flow rate, cruise speed and altitude and by increasing the fuel flow rate. The variations of NO2 emissions with these parameters are similar except the variation with altitude which has an inverse effect as compared to the variation of NO.

Does China Fall into Poverty-Environment Traps? Evidence from Long-term Income Dynamics and Urban Air Pollution

This paper examines the long-run relationship between income and urban air pollution using a joint distribution dynamics approach. This approach enables to estimate the transition process and long-run distribution and to examine the mechanisms behind the evolution process. The approach is applied to a unique panel data of CO2, SO2 and PM2.5 (particulate matter smaller than 2.5µm) for 286 Chinese cities over the period 2002-2014. Strong persistence in the transition dynamics suggests that this convergence process may require a long time. The distribution dynamics analyses indicate that multiple equilibria are the major characteristics in the long-run relationship between income and urban air pollution in China, which implies that inter-regional technology spillover may be an important way to accelerate convergence. Our results further support the existence of poverty-environmental trap in PM2.5 concentrations. Thus, new environmental models are expected to be developed to explain this new stylized fact. The findings provide strong support for taking more aggressive measures that consider income and urban environment simultaneously to reduce poverty and air pollutions together in the Chinese cities.

CONTROL GAS NITRIDING PROCESS: A REVIEW

The detailed surface is the boundary between the machine part and the working environment or with other machine parts in the structure of the machine. The surface is directly affected by the mechanical, physical and chemical effects of the environment. It is also the first place to receive loads, often subject to friction, abrasion The surface of the machine is where the hardest working conditions are, so it is also vulnerable to abrasion. There are many methods to the durable surface; But the most common method is diffusion. In diffusion method, there are many methods, but the chapter only focuses on the gas nitriding method and control of the gas nitriding process. Nitriding process can only be best achieved by control of the gas nitriding process, in particular by controlling the amount of incoming air at each stage. The specifications of the gas nitriding process will determine the quality of the nitriding layer. One of the very difficult parameters to control this process is the concentration of NH 3 and N 2 into the air. In order to control this air which will use the air control equiments but to control the permeability components in the equipment need special control processes with modern equipment. In this paper, we present a technique for control of the gas nitriding process by sensor hydro.

Building Fire: Experimental and Numerical Studies on Behaviour of Flows at Opening

Compartment fire is conducted by complex phenomena which have been the topics of many studies. During fire incident in a building, damage to occupants is not often due to the direct exposition to flames but to hot and toxic gases resulting from combustion between combustibles and surrounding air. Heat is therefore taken far from the source by combustion products which could involve a rapid spread of fire in the entire building. With the intention of studying the impact of the opening size on the behaviour of fire, experimental and computational studies have been undertaken in a reduced scale room including a single open door. Owing to Froude modelling, the obtained results have been transposed into full scale results. In accordance with experiments, numerical studies enabled the investigation of the influence of the ventilation factor on velocities of incoming air and outgoing burned gases and on areas of the surfaces crossed by these fluids during full-developed fire. Comparison of the deduced mass flow rates with the literature reveals an approval agreement.

Numerical Simulation of Flow and Heat Transfer in a Square Rotating U-Duct Using Hydrocarbon Fuel

Air turbine power generation system is considered as a feasible power generation system for hypersonic aircraft with Mach 6. However, the incoming air with high temperature cannot be used as coolant while turbine has to be cooled. Since hydrocarbon fuel is the only cooling source onboard, the scheme of fuel cooling air turbine is put forward. In this paper, square cooling channel, including inlet part, outlet part and U-duct, is established based on the typical air turbine. The hydraulic diameter of the channel is 2 mm and four types of U-ducts are used to compare the performance with simulation using k-Epsilon turbulence model. The density and specific heat capacity of fuel are considered as constant as the temperature difference in this study is small. The Reynolds number varies from 2760 to 16,559 and rotating number ranges from 0 to 6.9. The results show that the pressure distribution in radial direction is proportional to the square of radial distance and the square of rotating speed. The regulations of velocity and normalized Nusselt number distributions depend on rotating number. Furthermore, the heat transfer is enhanced with fin while the pressure loss is also increased. The position of fins cannot significantly influence pressure loss but can influence heat transfer obviously. The normalized Nusselt number of inlet-fin U-duct is higher than the outlet-fin U-duct both on leading side surface and trailing side (TS) surface, while the pressure losses for the two types of ducts are almost same.

Elevation‐dependent warming in the Swiss Alps 1981–2017: Features, forcings and feedbacks

Due to the environmental and socio‐economic importance of mountainous regions, it is crucial to understand causes and consequences of climatic changes in those sensitive landscapes. Daily resolution alpine climate data from Switzerland covering an elevation range of over 3,000 m between 1981 and 2017 have been analysed using highly resolved trends in order to gain a better understanding of features, forcings and feedbacks related to temperature changes in mountainous regions. Particular focus is put on processes related to changes in weather types, incoming solar radiation, cloud cover, air humidity, snow/ice and elevation dependency of temperature trends. Temperature trends in Switzerland differ depending on the time of the year, day and elevation. Warming is strongest during spring and early summer with enhanced warming of daytime maximum temperatures. Elevation‐based differences in temperature trends occur during autumn and winter with stronger warming at lower elevations. We attribute this elevation‐dependent temperature signal mainly to elevation‐based differences in trends of incoming solar radiation and elevation‐sensitive responses to changes in frequencies of weather types. In general, effects of varying frequencies of weather types overlap with trends caused by transmission changes in short‐ and long‐wave radiation. Temperature signals arising from snow/ice albedo feedback mechanisms are probably small and might be hidden by other effects.

Weapon target assignment optimization for land based multi-air defense systems: A goal programming approach

This study addressed the issue of allocating the air defense missiles to incoming air targets to maximize the air defense effectiveness of land-based air defense systems. A constraint based nonlinear goal programming (multi-objective) model for weapon assignment problem to minimize survival probability was developed. The model not only gave optimum assignment but also resulted in engagement times and defense success for multi-defense sites. The model utilized parameters belonging to defense systems such as engagement duration, setup duration between engagements, command and control structures, fire doctrines, and defense strategies and parameters belonging to target such as probability of kill values, position, orientation, weapon load, target type, and course of actions inferred by current detection information. The simulation model has two-way usages. In the first usage, it obtains solution for the parameters given above under limited number of missiles. In the second usage, the model shows the amount of missile to be used to achieve the possible highest success with the parameters given above. To be able to use the optimization model in a simulation environment, a simulation model as an optimizer agent is developed and located in air defense simulation scenarios. The model collects input data, optimize assignments, calculates fire times, and schedules fire orders. This solution is exemplified by a land-based air defense example.

Effects of vertical farming on natural ventilation of residential buildings

While vertical farming can promote sustainable living and mitigate urban heat island, vegetation could worsen the cross natural ventilation due to additional drag force on air flow. This study aims to investigate the impact of vertical farming on ventilation performance that is important to the thermal comfort especially at tropical/subtropical cities. The Computational Fluid Dynamics (CFD) simulation was first validated against the wind tunnel experiment in the street canyon with tree planting. The vegetable was modelled as porous medium in CFD simulation. In the parametric study, six configurations of facades module were investigated with respect to the vegetable block ratio, arrangement, and vegetable species. The results indicate that the natural ventilation performance is highly affected by the block ratio of vegetable. When three forth of the façade is covered by vegetable, i.e. block ratio of 0.75, the natural ventilation of the façade is very limited, with minimum leeward wind speed of 0.2m/s for incoming air flow of 2.0m/s. For the façade with a block ratio of 0.5, half of incoming air flow, i.e. minimum wind speed of 1.0m/s, can reach the near field downstream of the façade to promote indoor thermal comfort. Therefore, in the design process of the vertical farming, the block ratio of vegetable should be carefully determined regarding the ventilation performance. Furthermore, the natural ventilation with the same block ratio of vegetable could also be improved by appropriately modifying the vegetable arrangement and vegetable species. This study provides important understandings on vertical farming to enable architects to make the evidence-based decision in the architectural design.

Analysis of a multistage solar thermal energy accumulator

The present work evaluates the effect of using two paraffin wax with different solidification points as PCM, stored in soda cans and sequentially distributed, on the discharge efficiency of solar thermal energy accumulators in laboratory and prototype scales. The discharge efficiency ranges found were [74%,92%] and [49%,61%] for the laboratory and prototype scale models respectively. Greater efficiency values were obtained in both accumulators when the first rows of soda cans exposed to the incoming air was filled with the PCM of lower solidification point (41 °C) and the last row with PCM of higher solidification point (56 °C). Numerical solution of the mathematical modeling allowed to predict the outlet air temperature which compared with experimental data. Bigger discrepancies with the simulation results were obtained in the prototype scale accumulator due to the variability of the environmental conditions. As conclusion we stated that it is possible to enhance the discharge efficiency of a solar energy accumulator by using two PCM with different solidification points. The implemented mathematical model allowed to predict the time evolution of the air temperature at the accumulators outlet. Row order and paraffin wax type allow to adjust the energy discharge rate depending on the application type.