Experimental and Simulated Performances of a Batch-Type Longan Dryer with Air Flow Reversal Using Biomass Burner as a Heat Source

2011 ◽  
Vol 29 (12) ◽  
pp. 1439-1451 ◽  
Author(s):  
S. Janjai ◽  
N. Lamlert ◽  
B. Mahayothee ◽  
P. Sruamsiri ◽  
M. Precoppe ◽  
...  
Keyword(s):  
Heat Source ◽  
Air Flow ◽  
Flow Reversal ◽  
Batch Type

scholarly journals A three-dimensional theory of wind pumping

1991 ◽  
Vol 37 (125) ◽  
pp. 89-96 ◽  
Author(s):  
Garry K. C. Clarke ◽  
Edwin D. Waddington
Keyword(s):  
Heat Source ◽  
Surface Pressure ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Normal Component ◽  
Three Dimensional ◽  
Lower Atmosphere ◽  
Dimensional Theory ◽  
Theoretical Formulation ◽  
Near Surface

AbstractQuantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source.Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface.

scholarly journals Removal of HFC-134a from Brackish Water Using a Semi Batch Jet Loop Reactor

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 311 ◽  
Author(s):  
Devi Marietta Siregar ◽  
Yiseul Park ◽  
Yong Sun Won ◽  
Jun Heok Lim
Keyword(s):  
Flow Rate ◽  
Gas Hydrate ◽  
Brackish Water ◽  
Air Flow ◽  
High Mass ◽  
Air Flow Rate ◽  
Solubility In Water ◽  
Batch Type ◽  
Hfc 134A ◽  
Commercial Applications

Mineral salt components (Na+, Ca2+, K+, Mg2+, etc.) are naturally excluded during the gas hydrate in which water molecules form cavities by hydrogen bonding and guest gas molecules are encapsulated into the cavities to stabilize the overall gas hydrate structure. However, when using refrigerant hydrofluorocarbon-134a (HFC-134a) for guest gas, it resided in resulting brackish water after the desalination process because of its high solubility in water. Jet loop reactors (JLRs) are frequently employed in many commercial applications because of their high mass transfer capabilities. In this study, a semi-batch type JLR was introduced to improve the degassing of HFC-134a from brackish water. The effect of parameters, such as the initial HFC-134a concentration (200–772 mg/L), liquid circulation (40–80 L/min) rate, and air flow rate (10–30 L/min), were studied in this JLR. The removal efficiency and overall volumetric transfer were calculated and it was determined that increasing the air flow rate has a high effect on KLa.

Surging of Axial Compressors

1949 ◽  
Vol 1 (3) ◽  
pp. 195-210 ◽  
Author(s):  
H. Pearson ◽  
T. Bowmer
Keyword(s):  
Air Flow ◽  
Flow Reversal ◽  
Centrifugal Compressors ◽  
Axial Compressors ◽  
Complete Breakdown ◽  
Actual Flow ◽  
Normal Performance ◽  
Working Point

It is fairly generally known that if, at any fixed speed of a compressor, either axial or centrifugal, the flow is reduced by throttling the outlet, then a point is eventually reached at which a complete breakdown of the air flow occurs and in most cases an actual flow reversal through the compressor takes place. Sometimes this phenomenon is gradual, taking the form of a sort of burbling, but more generally it takes the form of a sudden “ bang ” associated with a violent shake of the whole foundation of the bed on which the compressor is mounted. In most centrifugal compressors the flow reversal which takes place stops rapidly, the performance recovers, and a second “ surge ” occurs if the throttling is not reduced. The frequency of these individual surges varies greatly according to the degree of throttling and many other conditions; it may be only one isolated occurrence, in which case it would be concluded that the working point was just, but only just on the surge point, or it may take the form of a rapid series of thuds indicating that the working point is beyond the surge. In all cases of centrifugal compressors known to the authors reduction of the throttling will restore the compressor to its normal performance.

A Large Area Rapid Thermal Processor for Flat Panel Displays

1993 ◽  
Vol 303 ◽  
Author(s):  
Chunghsin Lee ◽  
Robert B. Bramhall
Keyword(s):  
Heat Source ◽  
Great Difficulty ◽  
Flat Panel Displays ◽  
Flat Panel Display ◽  
Large Area ◽  
Flat Panel ◽  
Batch Type ◽  
Blue Phosphor ◽  
Single Arc ◽  
Heating Uniformity

ABSTRACTThe advantages of rapid thermal processing over slow, batch type processing have been demonstrated clearly in flat panel display manufacturing for a number of years. In the case of electroluminescence FPD, the brightness of the blue phosphor is increased by as much as 100%.However, rapid thermal processors that use a lamp-based heat source - either a tungsten lamp array or a single arc lamp - have great difficulty in achieving heating uniformity over large areas.By using a resistance-heated continuous heat source developed initially for RTP processing of large silicon wafers, temperature uniformity of less than +/− 2.5°C has been achieved over a panel with diagonal of 530mm.A description of the system and its characteristics are presented.

Computational Fluid Dynamics Simulation of Fire-Induced Air Flow in a Large Space Building: Key Points to Note

2004 ◽  
Author(s):  
Y. F. Li ◽  
W. K. Chow
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Source ◽  
Air Flow ◽  
Region Of Interest ◽  
Dynamics Simulation ◽  
Navier Stokes ◽  
Convergence Criteria ◽  
Large Space ◽  
Key Points

Fire-induced air flow in a large span building by computational fluid dynamics (CFD) will be discussed in this paper. The CFD model is based on Reynolds Averaging Navier-Stokes (RANS) equations with k-ε based turbulence model for predicting velocity, pressure and temperature distribution. This technique is commonly used in practical design for smoke management system. The fire is taken as a volumetric heat source and buoyancy effects are included in equations for the vertical momentum and turbulent parameters. Several key points to note in the simulation will be discussed. These are: • Relaxation factor and convergence criteria. • False diffusion. • Sudden changes in flow parameters across the heat source. A large terminal hall with 1 MW fire is taken as an example to discuss the above points. The fire scenarios in a region of interest will be assessed by CFD.

Natural Ventilation in Workshop with Different Horizontal Arrangement of Heat Source

2012 ◽  
Vol 229-231 ◽  
pp. 2411-2414
Author(s):  
Ya Xin Su ◽  
Xin Wan
Keyword(s):  
Temperature Distribution ◽  
Heat Source ◽  
Natural Ventilation ◽  
Air Flow ◽  
Ventilation Rate ◽  
Pollutant Emission ◽  
Distribution Factor ◽  
Cfd Method ◽  
The Right ◽  
Horizontal Arrangement

The natural ventilation in a heating workshop with different horizontal arrangement of heat source was numerically simulated based on computational fluid dynamics (CFD) method. Realizable k- turbulent model was used to calculate the air flow and temperature distribution. Simulation results showed that the horizontal arrangement of the heat source in the workshop influenced heavily the air flow and temperature distribution. When the heat source was placed at the workshop centre, the heat distribution factor was minimal, the average air temperature at operation zone was lowest and the hot air exhausting velocity was highest, the air flow field and temperature distribution was reasonable for the natural ventilation. When the heat source was placed to be close to the air inlet opening, the fresh air would travel a short path and directly rise to exit and the fresh air did not reach to the right part of the workshop, leading to a possible accumulation of pollutant emission there. When the heat source was placed at the right side of the workshop, the benefit would be that the possible pollutant could be taken away by the air flow, however, the ventilation rate decreased.

scholarly journals Simulation of Combustion Air Flow in the Gasification Biomass Boiler

2018 ◽  
Vol 168 ◽  
pp. 02015 ◽  
Author(s):  
Marek Patsch ◽  
Peter Pilát
Keyword(s):  
Heat Source ◽  
Air Flow ◽  
Biomass Combustion ◽  
Air Distribution ◽  
Combustion Chambers ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Biomass Boiler ◽  
Certification Tests ◽  
Experimental Heat

The article deals with the optimization of biomass combustion in a small heat source by means of an optimal distribution of combustion air. The uneven distribution of combustion air has been observed in certification tests and in real operation of used heat source and it has an influence on uneven combustion of biomass in the gasification chamber, on increase emissions and combustion losses. At this stage of the research, optimization of the combustion air distribution is performed by CFD simulations, which will be later verified by PIV measuring of the velocity fields in gasification and combustion chambers of the experimental heat source. CFD simulations and subsequent PIV measurements on the experimental device are realized without real combustion, only the air flow in the empty gasification chamber and in the combustion chamber is investigated. This approach has been chosen to simplify calculations and experiments, and on the assumption that when the combustion air distribution is optimal in empty chambers, it will be optimal even during real combustion. The primary air flow in the gasification chamber is in real operation affected by the size and shape of the inserted biomass and its placement in chamber and this effect is accidental and difficult to verifiable.

scholarly journals A three-dimensional theory of wind pumping

1991 ◽  
Vol 37 (125) ◽  
pp. 89-96 ◽  
Author(s):  
Garry K. C. Clarke ◽  
Edwin D. Waddington
Keyword(s):  
Heat Source ◽  
Surface Pressure ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Normal Component ◽  
Three Dimensional ◽  
Lower Atmosphere ◽  
Dimensional Theory ◽  
Theoretical Formulation ◽  
Near Surface

AbstractQuantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source.Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface.

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