Development of a Simulation Analysis Environment for Ventilated Slab Systems

2014 ◽  
Author(s):  
Benjamin Park ◽  
Moncef Krarti
Keyword(s):  
Simulation Analysis ◽  
Energy Performance ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Hollow Core ◽  
Simulation Environment ◽  
Core Diameter ◽  
Air Inlet ◽  
Thermal Bridge ◽  
Parametric Analyses

This paper presents a simulation environment developed to assess the energy performance of hollow core ventilated slab systems. The developed simulation environment combines a transient finite difference solution of a ventilated slab system with an RC network model for a multi-floor building. The developed simulation environment takes into account ventilated slab system thermal bridge effects on the energy performance of multi-floor buildings. The predictions of the developed simulation environment are verified against those obtained from a detailed whole-building energy simulation tool. In addition, several parametric analyses are performed to determine the performance of ventilated slab systems under various design and operating conditions. In particular, the parametric analyses include the effect of supply air inlet temperature, air mass flow rate, hollow core depth, and hollow core diameter. In particular, it is found that due to increased heat transfer through slab edge increases due to thermal bridge effects, ventilated slab requires 5% more heating and 7% more cooling energy end-uses.

scholarly journals Experimental Evaluation of the Energy Performance of an Air Vortex Tube when the Inlet Parameters are Varied

2013 ◽  
Vol 7 (1) ◽  
pp. 98-107 ◽  
Author(s):  
E. Torrella ◽  
J. Patiño ◽  
D. Sánchez ◽  
R. Llopis ◽  
R. Cabello
Keyword(s):  
Vortex Tube ◽  
Experimental Tests ◽  
Energy Performance ◽  
Cooling Capacity ◽  
Inlet Temperature ◽  
Temperature Variations ◽  
Cold Flow ◽  
Air Inlet ◽  
Cold Stream ◽  
Cooling Tube

The paper presents the analysis of the energy performance of an air vortex cooling tube under variations of the air inlet properties, with three independent experimental tests validated through the energy balance in the device. The experimental analysis includes the following variations of the input conditions: First, the effect of the air inlet pressure to the vortex tube, focused on the analysis of temperature variations in the output cold stream and in the cooling capacity when the cold flow fraction varies. Second, we studied air inlet temperature variations to the vortex tube under different cold flow fractions, which is an analysis not found in the literature. And finally, is studied the performance of the vortex tube when the insulation is provided or in absence of insulation.

scholarly journals Air-side performance of a micro-channel heat exchanger in wet surface conditions

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 375-385 ◽  
Author(s):  
Raviwat Srisomba ◽  
Lazarus Asirvatham ◽  
Omid Mahian ◽  
Ahmet Dalkılıç ◽  
Mohamed Awad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Relative Humidity ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Micro Channel ◽  
Surface Conditions ◽  
Air Inlet ◽  
Wet Surface

The effects of operating conditions on the air-side heat transfer, and pressure drop of a micro-channel heat exchanger under wet surface conditions were studied experimentally. The test section was an aluminum micro-channel heat exchanger, consisting of a multi-louvered fin and multi-port mini-channels. Experiments were conducted to study the effects of inlet relative humidity, air frontal velocity, air inlet temperature, and refrigerant temperature on air-side performance. The experimental data were analyzed using the mean enthalpy difference method. The test run was performed at relative air humidities ranging between 45% and 80%; air inlet temperature ranges of 27, 30, and 33?C; refrigerant-saturated temperatures ranging from 18 to 22?C; and Reynolds numbers between 128 and 166. The results show that the inlet relative humidity, air inlet temperature, and the refrigerant temperature had significant effects on heat transfer performance and air-side pressure drop. The heat transfer coefficient and pressure drop for the micro-channel heat exchanger under wet surface conditions are proposed in terms of the Colburn j factor and Fanning f factor.

Computational and Experimental Investigation of Emissions in a Highly Humidified Premixed Flame

2003 ◽  
Author(s):  
Fredrik Hermann ◽  
Jens Klingmann ◽  
Rolf Gabrielsson
Keyword(s):  
Air Temperature ◽  
Combustion Efficiency ◽  
Reaction Scheme ◽  
Operating Conditions ◽  
Aerodynamic Load ◽  
Inlet Temperature ◽  
Atmospheric Conditions ◽  
Air Inlet ◽  
Stirred Reactor ◽  
Maximum Humidity

Emission formation and flame stability were investigated, both experimentally and computationally, for premixed combustion with varying amounts of water vapor in the mixture. Emission measurements were made in a gas turbine combustor at atmospheric conditions, using Danish Natural Gas (NG) as fuel. The emissions were mapped as a function of humidity, inlet air temperature, equivalence ratio and aerodynamic load. Operating conditions were chosen to match what can be expected from e.g. an EvGT cycle for power generation. The inlet air temperature was slightly lower than the inlet temperatures that would be found in a recuperated cycle. The degree of humidity was varied from 0w% to 33w% of the airflow in the experiment, while the air inlet temperature was varied from 500K to 800K. Computations were made using a single Perfectly Stirred Reactor (PSR) model and a reaction scheme with 821 reactions and 69 species. It was found that the NOx emissions were strongly reduced by the addition of water. Most of this decrease vanishes in practical combustion since richer combustion is required to keep CO emissions (combustion efficiency) at a tolerable level. The maximum humidity was found to be dependent on inlet air temperature and aerodynamic load. In this experiment, the maximum humidity achieved was 33%.

Hydrogen Fueled Dry Low NOx Gas Turbine Combustor Conceptual Design

2014 ◽  
Author(s):  
Matteo Cerutti ◽  
Stefano Cocchi ◽  
Roberto Modi ◽  
Stefano Sigali ◽  
Gualtiero Bruti
Keyword(s):  
Gas Turbine ◽  
Conceptual Design ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Pure Hydrogen ◽  
Gas Turbine Combustor ◽  
Three Solutions ◽  
Air Inlet ◽  
Conceptual Design Phase ◽  
Development Paths

Conceptual design of a hydrogen fueled dry low NOx combustor for heavy duty gas turbine is presented in this paper, including a complete experimental validation, with focus on both NOx emissions and operability. Effort was first provided in the identification of viable conceptual solutions: a technology screening has been carried out, balancing both innovation content and proven experience of each concept. A look to alternative solutions coming from literature has been given too. Three burner concepts have been selected, designed and procured to be tested into a reduced scale rig, arranged to mimic main features of a small size gas turbine combustor, in terms of combustion air inlet temperature, hot gases residence times and amount of cooling: atmospheric pressure operation was considered a proper approximation to actual operating conditions for a conceptual design phase. The three solutions have been first characterized in terms of emissions against equivalence ratio, pilot percentage and burner pressure drop. At the same time, safe operation margins to both flashback and combustion instabilities onset have been identified for both pure hydrogen and pure natural gas feeding options. Results, while recommending different development paths for each of the investigated concepts, clearly indicate the most mature among them, allowing authors to address specific operability detailed investigations on it: flashback and flame holding resistance tests were thus performed, demonstrating that such a solution is mature for a preliminary full scale arrangement design and experimental characterization.

scholarly journals Microencapsulation ofβ-Carotene by Spray Drying: Effect of Wall Material Concentration and Drying Inlet Temperature

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Luiz C. Corrêa-Filho ◽  
Maria M. Lourenço ◽  
Margarida Moldão-Martins ◽  
Vítor D. Alves
Keyword(s):  
Antioxidant Activity ◽  
Spray Drying ◽  
Encapsulation Efficiency ◽  
Fruits And Vegetables ◽  
Wall Material ◽  
Inlet Temperature ◽  
Carotene Content ◽  
Arabic Gum ◽  
Air Inlet ◽  
Adverse Environmental Conditions

Carotenoids are a class of natural pigments found mainly in fruits and vegetables. Among them,β-carotene is regarded the most potent precursor of vitamin A. However, it is susceptible to oxidation upon exposure to oxygen, light, and heat, which can result in loss of colour, antioxidant activity, and vitamin activity. Thus, the objective of this work was to study the microencapsulation process ofβ-carotene by spray drying, using arabic gum as wall material, to protect it against adverse environmental conditions. This was carried out using the response surface methodology coupled to a central composite rotatable design, evaluating simultaneously the effect of drying air inlet temperature (110-200°C) and the wall material concentration (5-35%) on the drying yield, encapsulation efficiency, loading capacity, and antioxidant activity. In addition, morphology and particles size distribution were evaluated. Scanning electron microscopy images have shown that the particles were microcapsules with a smooth surface when produced at the higher drying temperatures tested, most of them having a diameter lower than 10μm. The conditions that enabled obtaining simultaneously arabic gum microparticles with higherβ-carotene content, higher encapsulation efficiency, and higher drying yield were a wall material concentration of 11.9% and a drying inlet temperature of 173°C. The systematic approach used for the study ofβ-carotene microencapsulation process by spray drying using arabic gum may be easily applied for other core and wall materials.

scholarly journals Geometrical Scaling of Antiresonant Hollow-Core Fibers for Mid-Infrared Beam Delivery

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 420
Author(s):  
Ang Deng ◽  
Wonkeun Chang
Keyword(s):  
Structural Parameters ◽  
Transmission Band ◽  
Confinement Loss ◽  
Hollow Core ◽  
Core Size ◽  
Core Diameter ◽  
Mid Infrared ◽  
The Core ◽  
Tubular Type ◽  
Beam Delivery

We numerically investigate the effect of scaling two key structural parameters in antiresonant hollow-core fibers—dielectric wall thickness of the cladding elements and core size—in view of low-loss mid-infrared beam delivery. We demonstrate that there exists an additional resonance-like loss peak in the long-wavelength limit of the first transmission band in antiresonant hollow-core fibers. We also find that the confinement loss in tubular-type hollow-core fibers depends strongly on the core size, where the degree of the dependence varies with the cladding tube size. The loss scales with the core diameter to the power of approximately −5.4 for commonly used tubular-type hollow-core fiber designs.

Unsteady simulations of migration and deposition of fly-ash particles in the first-stage turbine of an aero-engine

2021 ◽  
pp. 1-21
Author(s):  
Z. Hao ◽  
X. Yang ◽  
Z. Feng
Keyword(s):  
Fly Ash ◽  
Film Cooling ◽  
Particle Deposition ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Velocity Model ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Aero Engine

Abstract Particulate deposits in aero-engine turbines change the profile of blades, increase the blade surface roughness and block internal cooling channels and film cooling holes, which generally leads to the degradation of aerodynamic and cooling performance. To reveal particle deposition effects in the turbine, unsteady simulations were performed by investigating the migration patterns and deposition characteristics of the particle contaminant in a one-stage, high-pressure turbine of an aero-engine. Two typical operating conditions of the aero-engine, i.e. high-temperature take-off and economic cruise, were discussed, and the effects of particle size on the migration and deposition of fly-ash particles were demonstrated. A critical velocity model was applied to predict particle deposition. Comparisons between the stator and rotor were made by presenting the concentration and trajectory of the particles and the resulting deposition patterns on the aerofoil surfaces. Results show that the migration and deposition of the particles in the stator passage is dominated by the flow characteristics of fluid and the property of particles. In the subsequential rotor passage, in addition to these factors, particles are also affected by the stator–rotor interaction and the interference between rotors. With higher inlet temperature and larger diameter of the particle, the quantity of deposits increases and the deposition is distributed mainly on the Pressure Side (PS) and the Leading Edge (LE) of the aerofoil.

scholarly journals Managing energy performance in buildings from design to operation using modelling and calibration

2021 ◽  
pp. 014362442110083
Author(s):  
Nishesh Jain ◽  
Esfand Burman ◽  
Dejan Mumovic ◽  
Mike Davies
Keyword(s):  
Best Practice ◽  
Good Practice ◽  
Energy Performance ◽  
Operating Conditions ◽  
Design Stage ◽  
Performance Gap ◽  
Actual Performance ◽  
Simulation Tools ◽  
Calibration Protocol ◽  
Covering Design

To manage the concerns regarding the energy performance gap in buildings, a structured and longitudinal performance assessment of buildings, covering design through to operation, is necessary. Modelling can form an integral part of this process by ensuring that a good practice design stage modelling is followed by an ongoing evaluation of operational stage performance using a robust calibration protocol. In this paper, we demonstrate, via a case study of an office building, how a good practice design stage model can be fine-tuned for operational stage using a new framework that helps validate the causes for deviations of actual performance from design intents. This paper maps the modelling based process of tracking building performance from design to operation, identifying the various types of performance gaps. Further, during the operational stage, the framework provides a systematic way to separate the effect of (i) operating conditions that are driven by the building’s actual function and occupancy as compared with the design assumptions, and (ii) the effect of potential technical issues that cause underperformance. As the identification of issues is based on energy modelling, the process requires use of advanced and well-documented simulation tools. The paper concludes with providing an outline of the software platform requirements needed to generate robust design models and their calibration for operational performance assessments. Practical application The paper’s findings are a useful guide for building industry professionals to manage the performance gap with appropriate accuracy through a robust methodology in an easy to use workflow. The methodological framework to analyse building energy performance in-use links best practice design stage modelling guidance with a robust operational stage investigation. It helps designers, contractors, building managers and other stakeholders with an understanding of procedures to follow to undertake an effective measurement and verification exercise.

scholarly journals Improvement Effect of Green Remodeling and Building Value Assessment Criteria for Aging Public Buildings

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1200
Author(s):  
Yong-Joon Jun ◽  
Seung-ho Ahn ◽  
Kyung-Soon Park
Keyword(s):  
High Efficiency ◽  
Energy Performance ◽  
Operating Conditions ◽  
Energy Usage ◽  
Public Buildings ◽  
Value Judgment ◽  
Relationship Analysis ◽  
Improvement Effect ◽  
The Relationship ◽  
Usage Data

The Green Remodeling Project under South Korea’s Green New Deal policy is a government-led project intended to strengthen the performance sector directly correlated with energy performance among various elements of improvement applicable to building remodeling by replacing insulation materials, introducing new and renewable energy, introducing high-efficiency equipment, etc., with public buildings taking the lead in green remodeling in order to induce energy efficiency enhancement in private buildings. However, there is an ongoing policy that involves the application of a fragmentary value judgment criterion, i.e., whether to apply technical elements confined to the enhancement of the energy performance of target buildings and the prediction of improvement effects according thereto, thus resulting in the phenomenon of another important value criterion for green remodeling, i.e., the enhancement of the occupant (user) comfort performance of target buildings as one of its purposes, being neglected instead. In order to accurately grasp the current status of these problems and to promote ‘expansion of the value judgment criteria for green remodeling’ as an alternative, this study collected energy usage data of buildings actually used by public institutions and then conducted a total analysis. After that, the characteristics of energy usage were analyzed for each of the groups of buildings classified by year of completion, thereby carrying out an analysis of the correlation between the non-architectural elements affecting the actual energy usage and the actual energy usage data. The correlation between the improvement performance of each technical element and the actual improvement effect was also analyzed, thereby ascertaining the relationship between the direction of major policy strategies and the actual energy usage. As a result of the relationship analysis, it was confirmed that the actual energy usage is more affected by the operating conditions of the relevant building than the application of individual strategic elements such as the performance of the envelope insulation and the performance of the high-efficiency system. In addition, it was also confirmed that the usage of public buildings does not increase in proportion to their aging. The primary goal of reducing energy usage in target buildings can be achieved if public sector (government)-led green remodeling is pushed ahead with in accordance with biased value judgment criteria, just as in the case of a campaign to refrain from operating cooling facilities in aging public buildings. However, it was possible to grasp through the progress of this study that the remodeling may also result in the deterioration of environmental comfort and stability, such as the numerical value of the indoor thermal environment. The results of this study have the significance of providing basic data for pushing ahead with a green remodeling policy in which the value judgment criteria for aging existing public buildings are more expanded, and it is necessary to continue research in such a direction that the quantitative purpose of green remodeling, which is to reduce energy usage in aging public buildings, and its qualitative purpose, which is to enhance their environmental performance for occupants’ comfort, can be mutually balanced and secured at the same time.

Rough Air-Soft Elastohydrodynamic Lubrication

2013 ◽  
Vol 420 ◽  
pp. 30-35
Author(s):  
Khanittha Wongseedakaew ◽  
Jesda Panichakorn
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Modulus Of Elasticity ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Multilevel Methods ◽  
Inlet Temperature ◽  
Film Pressure ◽  
Air Inlet ◽  
Air Film

This paper presents the effects of rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material under the effect of air molecular slip. The time independent modified Reynolds equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness, modulus of elasticity and air inlet temperature are examined. The simulation results showed surface roughness has effect on film thickness but it little effect to air film pressure. When the amplitude of surface roughness and modulus of elasticity increased, the air film thickness decreased but air film pressure increased. However, the air inlet temperature increased when the air film thickness increased.

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