The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Li Cheng - One of the best experts on this subject based on the ideXlab platform.
-
Fluid Pattern and Optimum Design of Sump Based on CFD
Volume 2: Applied Fluid Mechanics; Electromechanical Systems and Mechatronics; Advanced Energy Systems; Thermal Engineering; Human Factors and Cogniti, 2012Co-Authors: Li ChengAbstract:The open sump is a typical inlet passage for small to middle-sized pumping station. It is important for the efficiency and safe operation of pumps that the open sump has an optimum design. The flow through the sump and into the pump is calculated using CFD. The incompressible N-S equations are solved by the finite volume method. The RNG k-e turbulence model and the SIMPLEC algorithm for pressure-velocity coupling are used. Many different designs for the open sump are considered, the results of which are compared based on common criteria to evaluate the sump performance. Design values for the width, the depth of submergence and the Bellmouth shape are derived.Copyright © 2012 by ASME
-
Research on the Design Process of Bellmouth Suction Passage of Vertical Pumping System
Volume 1: Symposia Parts A B and C, 2009Co-Authors: Li ChengAbstract:There are different types of suction box of vertical pumping system. In order to understand their relations and differences, the control volume method was used to simulate flow pattern of different suction boxes. The standard k-e turbulent model and SIMPLEC algorithm were applied in solving the N-S equations. The steady calculation results indicated that the flow patterns of different suction boxes of vertical pumping system were similar to each other. The different kinds of suction boxes were evolved from the pump sump. They can be united if they have essentially the same controlled parameters. It is a useful idea for the design of suction box of vertical pumping system.Copyright © 2009 by ASME
-
A study of active tonal noise control for a small axial flow fan
Journal of the Acoustical Society of America, 2005Co-Authors: Jingbo Wang, Lixi Huang, Li ChengAbstract:Sound radiated by a computer cooling fan consists of tones which are phase locked with the rotation, and other less deterministic tones and broadband random noise. This paper demonstrates the feasibility of globally eliminating the rotation-locked tones by applying a very simple destructive interference to a modified cooling fan with the number of struts equal to the number of rotor blades. The rig consists of a miniature electret microphone used as a rotation sensor, an ordinary loudspeaker, and a bandpass filter with adjustable amplitude and phase delay. The microphone is located at the inlet Bellmouth of the fan to pick up the fluctuating aerodynamic pressure caused by the passing rotor blades. The pressure spectrum is rich in the blade passing frequency (BPF) and its low-order harmonics. It provides much better performance than a pulse-generating tachometer. Analysis of the original fan noise shows that about 90% of the radiated tonal sound is phase locked with rotation, and this portion is almost com...
Nasa - One of the best experts on this subject based on the ideXlab platform.
-
Quiet Clean Short-haul Experimental Engine (QCSEE) Under-The-Wing (UTW) engine composite nacelle test report. Volume 1: Summary, aerodynamic and mechanical performance
2013Co-Authors: NasaAbstract:The performance test results of the final under-the-wing engine configuration are presented. One hundred and six hours of engine operation were completed, including mechanical and performance checkout, baseline acoustic testing with a Bellmouth inlet, reverse thrust testing, acoustic technology tests, and limited controls testing. The engine includes a variable pitch fan having advanced composite fan blades and using a ball-spline pitch actuation system.
Josua P. Meyer - One of the best experts on this subject based on the ideXlab platform.
-
Inlet flow effects in micro-channels in the laminar and transitional regimes on single-phase heat transfer coefficients and friction factors
International Journal of Heat and Mass Transfer, 2014Co-Authors: Jaco Dirker, Josua P. Meyer, Darshik V. GarachAbstract:An experimental investigation of heat transfer and pressure drop in rectangular micro-channels was conducted for water in the laminar and transitional regimes for three different inlet configurations. The inlet types under consideration were the sudden contraction, Bellmouth, and swirl inlet types, and hydraulic diameters of 0.57, 0.85, and 1.05 mm were covered. It was found that the critical Reynolds number and the transitional behaviour in terms of heat transfer coefficients and friction factors were influenced significantly by the inlet type. For the sudden contraction inlet type, which were investigated for both adiabatic, as well as diabatic cases, adiabatic friction factors were predicted well by the laminar Shah and London correlation, while diabatic friction factors were decreased with an increase in wall heat flux. The sudden contraction inlet critical Reynolds numbers were found to be between 1800 and 2000 for adiabatic cases, while for diabatic cases the transition regime commenced at a Reynolds number of about 2000. The Bellmouth and swirl inlet types were mostly investigated for diabatic cases only with swirl inlet tests limited to the 1.05 mm channel. Laminar friction factors were approximately similar to those of the sudden contraction inlet type, however, after the commencement of transition both inlet types exhibited higher friction factors than the sudden contraction inlet. Minor transition occurred as early as at Reynolds numbers of 1200 and 800 for the Bellmouth and swirl inlet types respectively while major transition occurred at Reynolds numbers of approximately 1800 and 1500 respectively. Critical Reynolds numbers were found not be significantly influenced by the channel diameter to length ratio considered in this study. Laminar Nusselt numbers were predicted well by conventional macro-channel thermal entry correlations. The swirl inlet type exhibited the highest friction factors and Nusselt numbers in the transitional regime followed by the Bellmouth inlet type. During transition while compared with the sudden contraction inlet, both the Bellmouth and swirl inlet types exhibited larger enhancement in heat transfer than increases in the friction factor penalty. Based on the experimental data obtained in this study, a set of correlations were developed which describes the relation between the friction factor and Colburn j-factor. Depending on the inlet type, the correlations predicted between 94% and 100% of the results to within 10% of the experimental measurements.
-
Heat Transfer and Pressure Drop Characteristics of Smooth Horizontal Tubes in the Transitional Flow Regime
Heat Transfer Engineering, 2014Co-Authors: Josua P. Meyer, Jonathan OlivierAbstract:The operating conditions of many heat exchangers are in, or close to, the transitional flow regime. However, in this regime, not a lot of design information is available and some design books even recommend to not design heat exchangers to operate in the transitional flow regime. Furthermore, it is known that the type of inlet of heat exchangers influences the transition characteristics. It was therefore the purpose of this study to measure heat transfer and pressure drop characteristics in smooth horizontal tubes using different types of inlets. The types of inlets were hydrodynamically fully developed, square-edged, re-entrant, and Bellmouth. Experiments were conducted on a 14.48-mm inner diameter horizontal tube in which the water was cooled. Reynolds numbers ranged between 1000 and 20,000 and Grashof numbers were on the order of 105. It was found that for adiabatic flow the square-edged inlet delayed transition to Reynolds numbers of around 2600, while the Bellmouth inlet delayed it to about 7000. How...
-
Heat transfer and pressure drop in micro-channels with different inlet conditions for water in the laminar and transitional regimes
2012Co-Authors: Darshik V. Garach, Jaco Dirker, Josua P. MeyerAbstract:Heat transfer by means of microchannels is an efficient method of cooling small but high-heat-dissipating objects. With very high heat transfer coefficients, the application of microchannels, especially in the field of electronics cooling, shows potential. With the aid of different inlet conditions, an experimental investigation to measure the heat transfer and pressure drop in a single copper microchannel, with a constant surface heat flux boundary condition, was undertaken in the laminar, transitional, and early turbulent regimes. Three test sections of hydraulic diameters 1.05 mm, 0.85 mm and 0.57 mm and of equal lengths of 200 mm were experimentally investigated using two inlet conditions: a sudden contraction inlet and a Bellmouth inlet. Friction factors were determined for three heat input conditions per test section. Results show lower values of the friction factor than the conventional theory in the laminar and turbulent regimes for the sudden contraction inlet. The Bellmouth inlet results show an early onset of transition compared to the sudden contraction, with a longer and smoother transition profile. Nusselt number results were higher in the laminar regime, while increasing until the onset of transition. Turbulent results show convergence to the Gnielinski equation for both inlet conditions.
-
Single-Phase Heat Transfer and Pressure Drop of the Cooling of Water inside Smooth Tubes for Transitional Flow with Different Inlet Geometries (RP-1280)
Hvac&r Research, 2010Co-Authors: Jonathan Olivier, Josua P. MeyerAbstract:Design constraints and energy requirements have often led to heat exchangers operating outside of their design parameters. These parameters often involve the exchanger operating in the transition region of flow. Adiabatic as well as diabatic experiments were conducted inside smooth tubes with diameters of 15.88 mm (5/8 in.) and 19.02 mm (3/4 in.). Four inlet profiles were investigated; hydrodynamically fully developed, square-edged, re-entrant, and Bellmouth. The test fluid was water that was cooled, with Reynolds numbers ranging between 1000 and 20,000, Prandtl numbers between 4 and 6, and Grashof numbers in the order of 105. Adiabatic results showed that transition from laminar to turbulent flow was strongly dependent on the inlet profile, with transition being delayed to Reynolds numbers as high as 12,000, confirming results of previous studies. Diabatic heat transfer and friction factor results showed that transition was independent of the inlet, with transition occurring at a Reynolds number of appro...
Jonathan Olivier - One of the best experts on this subject based on the ideXlab platform.
-
Heat Transfer and Pressure Drop Characteristics of Smooth Horizontal Tubes in the Transitional Flow Regime
Heat Transfer Engineering, 2014Co-Authors: Josua P. Meyer, Jonathan OlivierAbstract:The operating conditions of many heat exchangers are in, or close to, the transitional flow regime. However, in this regime, not a lot of design information is available and some design books even recommend to not design heat exchangers to operate in the transitional flow regime. Furthermore, it is known that the type of inlet of heat exchangers influences the transition characteristics. It was therefore the purpose of this study to measure heat transfer and pressure drop characteristics in smooth horizontal tubes using different types of inlets. The types of inlets were hydrodynamically fully developed, square-edged, re-entrant, and Bellmouth. Experiments were conducted on a 14.48-mm inner diameter horizontal tube in which the water was cooled. Reynolds numbers ranged between 1000 and 20,000 and Grashof numbers were on the order of 105. It was found that for adiabatic flow the square-edged inlet delayed transition to Reynolds numbers of around 2600, while the Bellmouth inlet delayed it to about 7000. How...
-
Single-Phase Heat Transfer and Pressure Drop of the Cooling of Water inside Smooth Tubes for Transitional Flow with Different Inlet Geometries (RP-1280)
Hvac&r Research, 2010Co-Authors: Jonathan Olivier, Josua P. MeyerAbstract:Design constraints and energy requirements have often led to heat exchangers operating outside of their design parameters. These parameters often involve the exchanger operating in the transition region of flow. Adiabatic as well as diabatic experiments were conducted inside smooth tubes with diameters of 15.88 mm (5/8 in.) and 19.02 mm (3/4 in.). Four inlet profiles were investigated; hydrodynamically fully developed, square-edged, re-entrant, and Bellmouth. The test fluid was water that was cooled, with Reynolds numbers ranging between 1000 and 20,000, Prandtl numbers between 4 and 6, and Grashof numbers in the order of 105. Adiabatic results showed that transition from laminar to turbulent flow was strongly dependent on the inlet profile, with transition being delayed to Reynolds numbers as high as 12,000, confirming results of previous studies. Diabatic heat transfer and friction factor results showed that transition was independent of the inlet, with transition occurring at a Reynolds number of appro...
R. A. Kach - One of the best experts on this subject based on the ideXlab platform.
-
Wave reflections from duct terminations.
Journal of the Acoustical Society of America, 2001Co-Authors: Ahmet Selamet, Z. L. Ji, R. A. KachAbstract:The reflection coefficients and inertial end corrections of several duct terminations, including finite length duct extensions perpendicular to an infinite wall, as well as at a number of angles, curved interface surfaces, and annular cavities, are determined and analyzed in the absence of flow by employing the boundary element method. Predictions for the classical unflanged and flanged circular ducts show good agreement with analytical and computational results available in the literature. The predictions for curved interface surfaces (Bellmouth or horn) are also consistent with the available experimental data. In view of its high reflection coefficient, the duct termination with an annular cavity may be suggested for the suppression of noise radiation in a specific frequency band or for an effective wave reflection from the termination.
