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Article
Publication date: 1 January 1991

R. PLATFOOT and C.A.J. FLETCHER

An alternative algorithm has been developed for computing the behaviour of flows within arbitrary ducts and channels. This technique requires a small number of downstream…

Abstract

An alternative algorithm has been developed for computing the behaviour of flows within arbitrary ducts and channels. This technique requires a small number of downstream marches in the primary flow direction, employing, on each march, numerically efficient procedures originally developed for a single sweep non‐elliptic flow solver. The multiple sweeps allow the capture of effects such as upstream pressure influences and streamwise recirculation. The energy equation is also solved to allow for varying heat transfer between the fluid and the boundary walls. The numerical work is further complicated by considering flows within turning sections of ducts which demonstrate large transverse velocities and consequent distortion of the primary flow. The computations are validated by comparison with a number of fluid/heat transfer experiments. The majority of these are taken from studies of turning flows within circular arc ducts which display the various pressure and transverse flow phenomena for which this new algorithm was initially developed to represent.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 1 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 31 March 2020

Nandkishor Sah and Mohan Jagadeesh Kumar Mandapati

Use of packed beds, enhanced tubes, nano-fluids and artificial ribs are few passive techniques to increase heat transfer in solar air heaters (SAHs). Artificial ribs…

Abstract

Purpose

Use of packed beds, enhanced tubes, nano-fluids and artificial ribs are few passive techniques to increase heat transfer in solar air heaters (SAHs). Artificial ribs attached to the absorber plate of the SAH will enhance the turbulence near the plate. Experimental analyses are conducted to find the thermal performance of SAH with ribs of regular geometries including rectangular, semi-circular and triangular in cross section. This paper aims to present the improvement in thermal performance of SAH with modified-arc.

Design/methodology/approach

Absorber plates are designed with ribs of rectangular, triangular, semi-circular and modified-arc in cross-section using existing data in literature. Physical dimensions of the ribs are designed by adapting procedure from literature. Absorber plates are manufactured with ribs and coated with blackboard paint and fixed to the existing SAH. Experiments are conducted with a variable-speed blower fixed to the inlet section of the SAH, which is used to supply air at different mass flow rates in a range between 0.495 and 0.557 kg/min.

Findings

Efficiency is found to be a strong function of mass flow rate of air through the SAH from the present experimental investigations. It was found that use of modified-arc ribs enhanced the efficiency of SAH by 105.35 per cent compared to SAH with plane absorber plate. Efficiency of SAH with modified-arc ribs is found to be higher by 24.43, 45.61 and 63.21 per cent, respectively, for SAH with semi-circular, rectangular and triangular arc ribs on its absorber plate.

Research limitations/implications

Experiments on SAH are conducted during daytime from 9:00 am to 5:00 pm in open atmospheric conditions. Solar intensity is continuously changing during the experimentation from morning to evening. Calculations are made based on the observations with average values of solar intensity and temperature readings. More accurate values of SAH efficiency can be obtained with constant heat supply to the absorber plate by simulating the experimental setup in indoor conditions. Temperature and flow rate observations could be more accurate with sophisticated instrumentation rather than using simple thermocouples and orifice meters.

Social implications

SAHs are basically used to supply hot air for both rural and industrial applications. These are used for crop drying, preheating of air, removal of moisture from leather, chemicals, etc. Conventionally, formers in India are using open sun drying to remove moisture from agricultural products. In this method, the moisture can be removed up to a level of 20 to 25 per cent. Use of SAH can remove moisture up to below 5 per cent and process is clean without reducing the quality of agricultural products. Enhancing the efficiency of SAHs will surely increase its usage by formers for crop drying.

Originality/value

Use of artificial ribs on absorber plate of SAH is most economical among many of the active and passive techniques. Numerical and experimental investigations are found in literature with regular cross-sectional ribs, including rectangular, triangular and semi-circular. The present work proposed new shape of the ribs named as modified-arc, which was not presented in the literature. Experimental analysis proved that the use of modified-arc makes the SAH more efficient in heat transfer.

Details

World Journal of Engineering, vol. 17 no. 3
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 12 October 2012

Fotios Papadopoulos, Ioannis Valakos and Ioannis K. Nikolos

The purpose of this paper is to design an S‐duct intake for unmanned aerial vehicles (UAVs) applications with good efficiency in a wide range of operating conditions.

Abstract

Purpose

The purpose of this paper is to design an S‐duct intake for unmanned aerial vehicles (UAVs) applications with good efficiency in a wide range of operating conditions.

Design/methodology/approach

A fully‐parametric 3‐D CAD model of the intake was constructed in order to produce different intake configurations, within specific geometric constraints, and to study the influence of geometry variation on efficiency. O‐type blocking methodology was adopted in order to construct the block‐structured mesh of hexahedral elements, used in the simulations. The commercial CFD code ANSYS‐CFX was used to compute the flow field inside the flow domain of each case considered. The Reynolds averaged Navier‐Stokes (RANS) equations are discretized using an implicit, vertex‐based finite volume method, combined with the shear stress transport (SST) two‐equation turbulence model and an automatic wall treatment.

Findings

By shortening the axial length the flow separation after the first turning becomes more pronounced and the losses are increasing. For very long ducts the increased internal wall area leads to increased wall friction and, consequently, to increased loss production.

Originality/value

The adoption of Gerlach‐shaped profiles for the design of the S‐duct resulted in a low pressure loss level for the optimal shape, although more uniform distribution of total pressure losses resulted for ducts longer than the optimal one, which should be taken into account in the design process.

Details

Aircraft Engineering and Aerospace Technology, vol. 84 no. 6
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 June 1996

Antonio Campo and Juan C. Morales

This paper presents a simple computational procedure for the laminar,fully established velocity and temperature in straight ducts with irregular,singly connected…

Abstract

This paper presents a simple computational procedure for the laminar, fully established velocity and temperature in straight ducts with irregular, singly connected cross‐sections by virtue of a control volume discretization of the momentum and energy equations in boundary‐fitted co‐ordinate systems. The combined procedure has been applied to a large group of ducts whose cross‐sections possess different levels of difficulty. The numerical predictions for the pressure drop (friction factor) and the convective heat transfer coefficient (Nusselt number) have been reported for a sub‐class of ducts with curved sides and sharp corners utilizing various grid sizes.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 6 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 July 1939

G.N. Patterson

AN interesting feature of modern aeroplane design is the growing use of duct systems. The low drag and heat regeneration obtainable from a cooling duct is now an…

Abstract

AN interesting feature of modern aeroplane design is the growing use of duct systems. The low drag and heat regeneration obtainable from a cooling duct is now an accomplished fact. Ventilation systems for cabin aircraft have been introduced. In the future we may see duct systems used in connexion with the control of the boundary layer. As aeroplane design is improved, new applications of duct systems continue to appear.

Details

Aircraft Engineering and Aerospace Technology, vol. 11 no. 7
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 2 January 2018

Kazimierz Rup, Lukasz Malinowski and Piotr Sarna

The purpose of this paper is to extend the possibilities of using the earlier developed indirect method of fluid flow rate measurement in circular pipes to the…

Abstract

Purpose

The purpose of this paper is to extend the possibilities of using the earlier developed indirect method of fluid flow rate measurement in circular pipes to the square-section channels with elbows installed.

Design/methodology/approach

The idea of the method is based on selecting such a value of the Reynolds number assumed as a coefficient in fluid flow equations, which fulfills with set accuracy the condition of equality between the measured and computed pressure difference at the end points of the secant of the elbow arch. The numerical calculus takes into consideration the exact geometry of the flow space and the measured temperature of the fluid, on the basis of which its thermo–physical properties are determined. To implement the proposed method in practice, a special test stand was built. The numerical computations were carried out using the software package FLUENT.

Findings

The results of calculations were compared with corresponding results of measurements achieved on the stand, as well as those found in the literature. The comparative analysis of the obtained numerical and experimental results shows a high grade of consistence.

Practical implications

The discussed elbow flow meter, implementing the extended indirect measuring method, can be applied to determine the flow rate of gases, as well as liquids and suspensions.

Originality/value

The indirect method used to measure the volumetric flow rate of the fluid is characterized by high accuracy and repeatability. The high accuracy is possible because of a very realistic mathematical model of the complex flow in the curved duct. The indirect method eliminates the necessity of frequent calibration of the flow meter. The discussed extended indirect measuring method can be applied to determine the flow rate of gases as well as liquids and suspensions. The fluid flow rate measurement based on the method considered in this paper can be particularly useful in newly designed as well as already operated ducts.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 1
Type: Research Article
ISSN: 0961-5539

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Abstract

FOR a number of years now it has been evident that a successor to the well‐tried Vickers Viscount and Convoir 240/340/440 series was required. However, the big problem was to design an aircraft such that its economics and passengerappealweresub‐stantially better than the machines it would ultimately replace. Other important factors which had to be con‐sidered were improved reliability, easier and cheaper maintenance, higher standards of safety and means of reducing ramp times. Furthermore, the difficult choice of passenger capacity and cruising speed had to be made. Probably the easiest decision was to employ the twin‐engine configuration with the power plants placed in the now familiar rear position, one on cither side of the fuselage.

Details

Aircraft Engineering and Aerospace Technology, vol. 35 no. 5
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 October 1964

TO say that the Twenty‐fourth S.B.A.C. Show was an unqualified success is perhaps to gild the lily. True there were disappointments— the delay which kept the TSR‐2 on the…

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Abstract

TO say that the Twenty‐fourth S.B.A.C. Show was an unqualified success is perhaps to gild the lily. True there were disappointments— the delay which kept the TSR‐2 on the ground until well after the Show being one—but on the whole the British industry was well pleased with Farnborough week and if future sales could be related to the number of visitors then the order books would be full for many years to come. The total attendance at the Show was well over 400,000—this figure including just under 300,000 members of the public who paid to enter on the last three days of the Show. Those who argued in favour of allowing a two‐year interval between the 1962 Show and this one seem to be fully vindicated, for these attendance figures are an all‐time record. This augurs well for the future for it would appear that potential customers from overseas are still anxious to attend the Farnborough Show, while the public attendance figures indicate that Britain is still air‐minded to a very healthy degree. It is difficult to pick out any one feature or even one aircraft as being really outstanding at Farnborough, but certainly the range of rear‐engined civil jets (HS. 125, BAC One‐Eleven, Trident and VCIQ) served as a re‐minder that British aeronautical engineering prowess is without parallel, while the number of rotorcraft to be seen in the flying display empha‐sized the growing importance of the helicopter in both civil and military operations. As far as the value of Farnborough is concerned, it is certainly a most useful shop window for British aerospace products, and if few new orders are actually received at Farnborough, a very large number are announced— as our ’Orders and Contracts' column on page 332 bears witness. It is not possible to cover every exhibit displayed at the Farnborough Show but the following report describes a wide cross‐section beginning with the exhibits of the major airframe and engine companies.

Details

Aircraft Engineering and Aerospace Technology, vol. 36 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 30 September 2014

Fabio Furlan, Nicola Chiereghin, Timoleon Kipouros, Ernesto Benini and Mark Savill

– The purpose of this paper is to identify efficient methods and tools for the design of distributed propulsion architectures.

Abstract

Purpose

The purpose of this paper is to identify efficient methods and tools for the design of distributed propulsion architectures.

Design/methodology/approach

Multi-objective computational aerodynamic design optimisation of an S-Duct shape.

Findings

Both duct pressure loss and flow distortion through such a duct can be reduced by wall-curvature changes.

Research limitations/implications

Initial simplified study requires higher fidelity computational fluid dynamics & design sensitivity follow-up.

Practical implications

Shape optimisation of an S-Duct intake can improve intake efficiency and reduce the risk of engine-intake compatibility problems.

Social implications

Potential to advance lower emissions impact from distributed propulsion aircraft.

Originality/value

Both the duct loss and flow distortion can be simultaneously reduced by significant amounts.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86 no. 6
Type: Research Article
ISSN: 0002-2667

Keywords

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Article
Publication date: 1 December 1965

C.E. Tharratt

A Theoretical Approach to Assessing the Thermodynamic Process Within the Combustion Chamber of the Propulsive Duct, an Examination of the Potential of the Duct with…

Abstract

A Theoretical Approach to Assessing the Thermodynamic Process Within the Combustion Chamber of the Propulsive Duct, an Examination of the Potential of the Duct with Special Reference to the Application of Feedback and Spark Discharge Techniques. The type of valve of greatest importance to successful duct design is one which is synchronized to the pressure fluctuations within the combustion zone. Although there have been a number of proposals for mechanically linked valves (indeed the normal internal combustion engine works on this principle) and rotary valves, these have severe limitations at the higher frequencies and are generally impracticable for the application under review. This section will therefore concentrate on the mechanical reed‐type valve which, theoretically, need have only one moving part, i.e. the dynamic metal reed, and the aerodynamic valve which relies upon the interaction of two gas dynamical vibrations and has no moving mechanical parts.

Details

Aircraft Engineering and Aerospace Technology, vol. 37 no. 12
Type: Research Article
ISSN: 0002-2667

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