scholarly journals Solar Thermal Panels for Small-Medium Scale Air Cleaners in Major Cities

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Francisco J. Arias ◽  
Salvador De Las Heras
Keyword(s):  
Mass Flow ◽  
Cooling System ◽  
Air Flow ◽  
Solar Thermal ◽  
Air Purification ◽  
Small Scale ◽  
Cooling Systems ◽  
Air Mass ◽  
Medium Scale ◽  
Air Cleaners

Air quality in major cities is reaching worrisome levels across the planet owing to large-scale industrialization. As a result, air purification systems are becoming a fertile and emerging field for research. Here, consideration is given to the use of a small-medium scale air purification system for cities using a kind of solar thermal panels by inducing local convective currents intended to be used in parks, housing estates, or similar urban places providing a local improvement of the quality of the air. The main difficulty which arose when attempting to use these convective currents is that the upward flow of hot air, which has been cleaned from contaminant particles during its upward travel, must be returned back to the ground. To accomplish this, air must be cooled during the travel in order to obtain an effective buoyancy. Several possible solutions have been proposed in the past, for example, the use of a dedicated cooling system as is the use of water spraying systems which could be an attractive option for large towers. However, for small-medium scale air cleaners, dedicated spraying cooling systems are out of question either because of the requirement of water flow or because of the high local humidity generated which can be uncomfortable for humans. One possible solution could be taking advantage of vertical panels in which a side of the panel is permanently irradiated and the other is permanently in the shadow; in this way, heating and cooling could be performed eliminating the need for specialized cooling systems, and although the effective buoyancy—and then the purified air mass flow—of such a system is considerably reduced, nevertheless, it could still be acceptable for local small-scale applications. Utilizing a simplified physical model, the effective buoyancy and attainable air mass flow were calculated. It is shown that for a small panel of 5 m-height or thereabouts, an air flow per unit of width ∼0.4 kg/s is attainable, and for a 10 m-height panel, an air flow per unit of width 0.6 kg/s is attainable. Computational fluid dynamics simulations were performed which agree with the analytical results within ±30 %.

Perimeter Cooling Unit and Localized Row-Based Cooling Unit Transient Air Flow Effects Modeling and Characterization in Data Centers

2015 ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Bahgat G. Sammakia ◽  
Russell Tipton ◽  
Mark Seymour
Keyword(s):  
Thermal Management ◽  
Data Center ◽  
Data Centers ◽  
Cooling System ◽  
Air Flow ◽  
Cooling Systems ◽  
Dynamic Thermal Management ◽  
Hybrid Cooling ◽  
Cooling Unit ◽  
Cooling Air

Cooling power constitutes a large portion of the total electrical power consumption in data centers. Approximately 25%∼40% of the electricity used within a production data center is consumed by the cooling system. Improving the cooling energy efficiency has attracted a great deal of research attention. Many strategies have been proposed for cutting the data center energy costs. One of the effective strategies for increasing the cooling efficiency is using dynamic thermal management. Another effective strategy is placing cooling devices (heat exchangers) closer to the source of heat. This is the basic design principle of many hybrid cooling systems and liquid cooling systems for data centers. Dynamic thermal management of data centers is a huge challenge, due to the fact that data centers are operated under complex dynamic conditions, even during normal operating conditions. In addition, hybrid cooling systems for data centers introduce additional localized cooling devices, such as in row cooling units and overhead coolers, which significantly increase the complexity of dynamic thermal management. Therefore, it is of paramount importance to characterize the dynamic responses of data centers under variations from different cooling units, such as cooling air flow rate variations. In this study, a detailed computational analysis of an in row cooler based hybrid cooled data center is conducted using a commercially available computational fluid dynamics (CFD) code. A representative CFD model for a raised floor data center with cold aisle-hot aisle arrangement fashion is developed. The hybrid cooling system is designed using perimeter CRAH units and localized in row cooling units. The CRAH unit supplies centralized cooling air to the under floor plenum, and the cooling air enters the cold aisle through perforated tiles. The in row cooling unit is located on the raised floor between the server racks. It supplies the cooling air directly to the cold aisle, and intakes hot air from the back of the racks (hot aisle). Therefore, two different cooling air sources are supplied to the cold aisle, but the ways they are delivered to the cold aisle are different. Several modeling cases are designed to study the transient effects of variations in the flow rates of the two cooling air sources. The server power and the cooling air flow variation combination scenarios are also modeled and studied. The detailed impacts of each modeling case on the rack inlet air temperature and cold aisle air flow distribution are studied. The results presented in this work provide an understanding of the effects of air flow variations on the thermal performance of data centers. The results and corresponding analysis is used for improving the running efficiency of this type of raised floor hybrid data centers using CRAH and IRC units.

scholarly journals A Numerical Analysis of the Air-Cooling System of a Spark Ignition Aeronautical Engine

2020 ◽  
Vol 197 ◽  
pp. 06003
Author(s):  
Maria Faruoli ◽  
Annarita Viggiano ◽  
Paolo Caso ◽  
Vinicio Magi
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling System ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Air Cooling ◽  
Air Mass ◽  
Air Cooling System

It is well known that spark ignition internal combustion engines for aeronautical applications operate within a specific temperature range to avoid structural damages, detonations and loss of efficiency of the combustion process. An accurate assessment of the cooling system performance is a crucial aspect in order to guarantee broad operating conditions of the engine. In this framework, the use of a Conjugate Heat Transfer method is a proper choice, since it allows to estimate both the heat fluxes between the engine walls and the cooling air and the temperature distribution along the outer wall surfaces of the engine, and to perform parametric analyses by varying the engine operating conditions. In this work, the air-cooling system of a 4-cylinder spark ignition engine, designed by CMD Engine Company for aeronautical applications, is analysed in order to evaluate the amount of the air mass flow rate to guarantee the heat transfer under full load operating conditions. A preliminary validation of the model is performed by comparing the results with available experimental data. A parametric study is also performed to assess the influence of the controlling parameters on the cooling system efficiency. This study is carried out by varying the inlet air mass flow rate from 1.0 kg/s to 1.5 kg/s and the temperature of the inner wall surfaces of the engine combustion chambers from 390 K to 430 K.

Multidisciplinary Sensitivity Analysis of the Cooling System of a High-Pressure Turbine Blade in the Pre-Design Phase

2021 ◽  
Author(s):  
Barbara Fiedler ◽  
Yannick Muller ◽  
Matthias Voigt ◽  
Ronald Mailach
Keyword(s):  
Mass Flow ◽  
Cooling System ◽  
Mechanical Analysis ◽  
Thermal Design ◽  
Probabilistic Methods ◽  
Cycle Performance ◽  
Design Parameters ◽  
Cooling Systems ◽  
Cooling Air Flow ◽  
Cooling Air

Abstract The engine-cycle performance of jet engines can be improved by more efficient cooling systems, either by reducing the required cooling air or by intensifying the cooling efficiency with the same amount of cooling mass flow. However, the multitude of geometrical design parameters and the strong multidisciplinary aspect of cooling mass flow consumption optimization make designing the cooling systems extremely challenging. Integrating probabilistic methods into the thermal design process enables the automated evaluation of multiple design variants which contributes to the development of more efficient systems. In the present study, the sensitivity of a multi-pass cooling system to geometric variations is investigated. The cooling air flow, solved using a 1D, correlation based flow solver, is iteratively coupled with the 3D-FE thermo-mechanical analysis of the blade. The geometry of the cooling system is varied using the Harmonic-Spline-Deformation parametric, which has been extended to modify the wall thickness enabling to perform a geometrical-holistic analysis. Furthermore, the Elementary-Effects-Method (EEM) and the Monte-Carlo-Simulation (MCS) are compared to identify the most influential parameters and analyze their complex interactions. It is shown that the cooling system’s performance is mostly affected by the shape and position of the first web. Furthermore, MCS proves to be robust towards changes in design space while simultaneously enabling a more detailed analysis of the system behavior compared to EEM.

Comparative Analysis of Solar Thermal Cooling and Solar Photovoltaic Cooling Systems

2011 ◽  
Author(s):  
N. Fumo ◽  
V. Bortone ◽  
J. C. Zambrano
Keyword(s):  
Energy Consumption ◽  
Fossil Fuels ◽  
Cooling System ◽  
Solar Thermal ◽  
Solar Photovoltaic ◽  
Solar Thermal Energy ◽  
Cooling Systems ◽  
Solar Cooling ◽  
Solar Thermal Cooling ◽  
Thermal Cooling

The Energy Information Administration of the United States Department of Energy projects that more than 80% of the energy consumption of the U.S. by 2035 will come from fossil fuels. This projection should be the fuel to promote projects related to renewable energy in order to reduce energy consumption from fossil fuels to avoid their undesirable consequences such as carbon dioxide emissions. Since solar radiation match pretty well building cooling demands, solar cooling systems will be an important factor in the next decades to meet or exceed the green gases reduction that will be demanded by the society and regulations in order to mitigate environmental consequences such as global warming. Solar energy can be used as source of energy to produce cooling through different technologies. Solar thermal energy applies to technology such as absorption chillers and desiccant cooling, while electricity from solar photovoltaic can be used to drive vapor compression electric chillers. This study focuses on the comparison of a Solar Thermal Cooling System that uses an absorption chiller driven by solar thermal energy, and a Solar Photovoltaic Cooling System that uses a vapor compression system (electric chiller) driven by solar electricity (solar photovoltaic system). Both solar cooling systems are compared against a standard air cooled cooling system that uses electricity from the grid. The models used in the simulations to obtain the results are described in the paper along with the parameters (inputs) used. Results are presented in two figures. Each figure has one curve for the Solar Thermal Cooling System and one for the Solar Photovoltaic Cooling System. One figure allows estimation of savings calculated based the net present value of energy consumption cost. The other figure allows estimating primary energy consumption reduction and emissions reduction. Both figures presents the result per ton of refrigeration and as a function of area of solar collectors or/and area of photovoltaic modules. This approach to present the result of the simulations of the systems makes these figures quite general. This means that the results can be used to compare both solar cooling systems independently of the cooling demand (capacity of the system), as well as allow the analysis for different sizes of the solar system used to harvest the solar energy (collectors or photovoltaic modules).

scholarly journals Spiral Vibration Cooler for Continual Cooling of Biomass Pellets

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1060
Author(s):  
David Žurovec ◽  
Lucie Jezerská ◽  
Jan Nečas ◽  
Jakub Hlosta ◽  
Jan Diviš ◽  
...  
Keyword(s):  
Cooling System ◽  
Negative Impact ◽  
Air Flow ◽  
Important Process ◽  
Cooling Process ◽  
Cooling Systems ◽  
Technical Problems ◽  
Insight Into ◽  
Vibrating Feeder

Cooling is an important process during the production of pellets (as post-treatment). The pellet cooling process significantly impacts the quality of the pellets produced and the systematic use of energy. However, the cooling systems currently in use sometimes encounter technical problems, such as clogging of the perforated grids (sieves), the discharge hopper, or pellet degradation may occur. Therefore, a prototype of a new pellet cooling system using a vibrating feeder was tested. The aim of the study is to present a new variation of pellet cooling system using spiral vibration cooler as a possible solution next to a counterflow cooler. The presented system was tested (critically evaluated and discussed) in two design variants. The first variant consists in cooling by chaotic movement of the pellets. The second is then in combination with the chaotic movement of the pellets together with the action of intense air flow using specially placed air hoses. All tests involved pelletization of rapeseed straw. It was found that both cooling system variants could, realistically, be used. However, the variant with an intense air flow was more energy-intensive, a factor which is, however, offset by the higher quality of the pellets. No negative impact of vibrations to pellets quality was occur. Studies provide insight into new usable technologies that do not reduce the efficiency of the process as a result of grate clogging.

Three-Dimensional Forced Air Cooling System Analysis of a Scooter Engine

2002 ◽  
Author(s):  
Ennio Carnevale ◽  
Giacomo Migliorini ◽  
Stefano Zecchi ◽  
Bart Olmi
Keyword(s):  
Mass Flow ◽  
Noise Level ◽  
Cooling System ◽  
Three Dimensional ◽  
Low Noise ◽  
Air Cooling ◽  
Air Mass ◽  
Air Cooling System ◽  
Flow Demand ◽  
Forced Air

Internal combustion engines must match several requirements such as good efficiency and low fuel consumption rate; when they are applied on scooter they are subject to some other restrictions. Nowadays, both low pollutant emissions and low noise level are requested for this engine since scooters are usually city vehicles. To match these requirements several aspects must be investigated: one of these may be the cooling system. There are usually three cooling methods, i.e. free stream air cooling, liquid cooling and forced air cooling. The first one is usually not employed in scooter engines because of its arrangement inside the scooter body (due to functionality and aestheticism). The second one may present some plant complications caused by the heat exchanger and ducts. A forced air cooling system presents usually lower complication, lower weight and greater reliability. Nevertheless, in order to keep engine temperatures below lubricant and structural limit, high mass flow rate may be necessary since air has smaller coolant efficiency compared to liquids. Moreover cooling air, supplied by a fan, requires high pumping power which may be excessive at high rotational speed; the fan itself may produce excessive noise reducing comfort. Sometimes, it may be hard to define the air flow demands in order to properly cool the critical parts (i.e. cylinder head); poor design may result in an excessive air mass flow demand and high pressure losses. Consequently the fan requires an excessive power and emits high noise level. Proper coolant distribution around the cylinder and the engine head reduces the overall air mass flow demand, rising indirectly engine efficiency. Usually the geometry of a forced air cooled engine is quite complex because of fins and other internal passages. To study coolant distribution and heat transfer a three-dimensional approach is then required. Computational fluid dynamic calculations, provided by commercial codes, can give useful suggestions about flow distribution around a finned cylinder. This paper will show an analysis of a typical air cooled scooter engine. Air mass flows and cooling efficiency are shown at several engine rotational speeds.

scholarly journals Small Scale Solar Cooling Unit in Climate Conditions of Latvia: Environmental and Economical Aspects

2010 ◽  
Vol 4 (-1) ◽  
pp. 47-52
Author(s):  
Dzintars Jaunzems ◽  
Ivars Veidenbergs
Keyword(s):  
Cooling System ◽  
Electricity Consumption ◽  
Economic Feasibility ◽  
Point Of View ◽  
Small Scale ◽  
Cooling Systems ◽  
Climate Conditions ◽  
Solar Cooling ◽  
Cooling Unit ◽  
Solar Cooling System

Small Scale Solar Cooling Unit in Climate Conditions of Latvia: Environmental and Economical Aspects The paper contributes to the analyses from the environmental and economical point of view of small scale solar cooling system in climate conditions of Latvia. Cost analyses show that buildings with a higher cooling load and full load hours have lower costs. For high internal gains, cooling costs are around 1,7 €/kWh and 2,5 €/kWh for buildings with lower internal gains. Despite the fact that solar cooling systems have significant potential to reduce CO2 emissions due to a reduction of electricity consumption, the economic feasibility and attractiveness of solar cooling system is still low.

Numerical and Experimental Characterization of the Transient Effectiveness of a Water to Air Heat Exchanger for Data Center Cooling Systems

2015 ◽  
Author(s):  
Tianyi Gao ◽  
Marcelo del Valle ◽  
Alfonso Ortega ◽  
Bahgat G. Sammakia
Keyword(s):  
Heat Exchanger ◽  
Mass Flow ◽  
Data Center ◽  
Heat Exchangers ◽  
Cooling System ◽  
Cross Flow ◽  
Inlet Temperature ◽  
Experimental Measurements ◽  
Cooling Systems ◽  
Flow Heat

The cross flow heat exchanger is at the heart of most cooling systems for data centers. Air/Water or air/refrigerant heat exchangers are the principal component in Central Room Air Conditioning (CRAC) units that condition data room air that is delivered through an underfloor plenum. Liquid/air heat exchangers are also increasingly deployed in close-coupled cooling systems such as rear door heat exchangers, in-row coolers, and overhead coolers. In all cases, the performance of liquid/air heat exchangers in both steady state and transient scenarios are of principal concern. Transient scenarios occur either by the accidental failure of the cooling system or by intentional dynamic control of the cooling system. In either scenario, transient boundary conditions involve time-dependent air or liquid inlet temperatures and mass flow rates that may be coupled in any number of potential combinations. Understanding and characterizing the performance of the heat exchanger in these transient scenarios is of paramount importance for designing better thermal solutions and improving the operational efficiency of existing cooling systems. In this paper, the transient performance of water to air cross flow heat exchangers is studied using numerical modeling and experimental measurements. Experimental measurements in 12 in. × 12 in. heat exchanger cores were performed, in which the liquid (water) mass flow rate or inlet temperature are varied in time following controlled functional forms (step jump, ramp). The experimental data were used to validate a transient numerical model developed with traditional assumptions of space averaging of heat transfer coefficients, and volume averaging of thermal capacitances. The complete numerical model was combined with the transient effectiveness methodology in which the traditional heat exchanger effectiveness approach is extended into a transient domain, and is then used to model the heat exchanger transient response. Different transient scenarios were parametrically studied to develop an understanding of the impact of critical variables such as, the fluid inlet temperature variation and the fluid mass flow rate variation, and a more comprehensive understanding of the characteristics of the transient effectiveness. Agreement between the novel transient effectiveness modeling approach and the experimental measurements enable use of the models as verified predictive design tools. Several studies are designed based on the practical problems related to data center thermal environments and the results are analyzed.

Influence of Fuel Physical Properties and Reaction Rate on Threshold Heterogeneous Gas Turbine Combustion

2012 ◽  
Author(s):  
Victor Burger ◽  
Andy Yates ◽  
Carl Viljoen
Keyword(s):  
Mass Flow ◽  
Flow Rate ◽  
Laminar Flame ◽  
Chemical Reactivity ◽  
Air Flow ◽  
Cetane Number ◽  
Relative Pressure ◽  
Fuel Blend ◽  
Air Mass ◽  
Pressure Drops

The paper presents the findings from a study of the lean blowout (LBO) behaviour of sixteen fuel blends in a heterogeneous laboratory combustor. The LBO results were correlated with fuel blend properties that included the D86 distillation profile, density, viscosity, flash point and ignition delay as represented by derived cetane number (DCN). A spherical bomb was employed to measure laminar flame speed and Markstein length based on pressure measurements. The experiments were conducted with two different starting temperatures and over a range of air fuel ratios from rich to lean. The atomisation behaviour of the fuels was evaluated using a pressure atomised nozzle and a laser diffraction particle sizer. The data allowed the Sauter mean diameter (SMD) values at extinction to be estimated based on the fuel pressure. Each individual LBO test was conducted at constant air flow rate with the extinction point being attained by reducing the fuel flow rate. The test series for each fuel spanned a range of air flow rates based on combustor liner relative pressure drops from 1% to 6%. These results exhibited three distinct regions (A1, A2 and B) that were evident to varying degrees in the results obtained with all sixteen test fuels. The transition between A1 and A2 was ascribed to combustor flow and was shown to be independent of the fuel being tested. The transition between B and A2 was ascribed to the change from the LBO behaviour being dominated by atomization to it being a mixing / turbulence dominated regime. The individual transitions were found to be dependent on the test fuel blend. In order to accommodate the LBO results in a multivariate analysis the observed trends were represented by three parameters that were determined through curve fitting to the different regions. The three parameters were the SMD and air mass flow rate at the transition between region B and A2 and a projected LBO equivalence ratio at zero air mass flow. The data was cross correlated between all determined properties and it was shown that the extinction behaviour correlated with chemical reactivity, flame stretch, density and volatility to different degrees in the two regions of operation. It was concluded that there is potential for influencing threshold extinction limits through both chemical and physical jet fuel properties, and the need to take cognisance thereof in fuel formulation, was highlighted.

Use of Engineered Materials to Reduce Both Strainer Head Loss and Fiber Bypass for Emergency Core Cooling Systems

2019 ◽  
Author(s):  
Alan J. Bilanin ◽  
Andrew E. Kaufman ◽  
Warren J. Bilanin
Keyword(s):  
Large Scale ◽  
Cooling System ◽  
Head Loss ◽  
Small Scale ◽  
Pressurized Water ◽  
Cooling Systems ◽  
Large Scale Testing ◽  
Engineered Materials ◽  
Water Reactors ◽  
Core Cooling

Abstract Testing has shown that the use of engineered materials that can be combined with Loss of Cooling Accident generated debris has the ability to reduce debris head loss for boiling water and pressurized water reactors on Emergency Core Cooling System strainers. This engineered material has also been shown to reduce the amount of fiber that penetrates a strainer and continues downstream toward the fuel. Large scale testing is described that demonstrates that engineered materials can reach the strainers and reduce head loss. Small scale testing is described that demonstrates that engineered material can reduce the amount of fiber that can penetrate a strainer.

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