Pressure Loss Coefficients for VAV Terminal Units

2021 ◽  
Author(s):  
Kiran Lankalapalli ◽  
Stephen Idem
Keyword(s):  
Pressure Loss ◽  
Loss Coefficients ◽  
Terminal Units

scholarly journals Turbulence model performance for ventilation components pressure losses

2021 ◽  
Author(s):  
Karsten Tawackolian ◽  
Martin Kriegel
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Test Case ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Near Wall

AbstractThis study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ε turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

Simulations to Determine Laminar Loss Coefficients for Flow in Circular Ducts With Arbitrary Planar Bifurcation Geometries

2008 ◽  
Author(s):  
Tim A. Handy ◽  
Evan C. Lemley ◽  
Dimitrios V. Papavassiliou ◽  
Henry J. Neeman
Keyword(s):  
Pressure Loss ◽  
Three Dimensional ◽  
Computer Code ◽  
Two Dimensions ◽  
Stagnation Pressure ◽  
Loss Coefficient ◽  
Pressure Losses ◽  
Common Plane ◽  
Loss Coefficients ◽  
Inlet Duct

The goal of this study was to determine laminar stagnation pressure loss coefficients for circular ducts in which flow encounters a planar bifurcation. Flow conditions and pressure losses in these laminar bifurcations are of interest in microfluidic devices, in porous media, and in other networks of small ducts or pores. Until recently, bifurcation geometries had been studied almost exclusively for turbulent flow, which is often found in fluid supply and drain systems. Recently, pressure loss coefficients from simulations of a few arbitrary bifurcation geometries in two-dimensions have been published — the present study describes the extension of these two-dimensional simulations to three-dimensional circular ducts. The pressure loss coefficients determined in this study are intended to allow realistic simulation of existing laminar flow networks or the design of these networks. This study focused on a single inlet duct with two outlet ducts, which were allowed to vary in diameter, flow fraction, and angle — all relative to the inlet duct. All ducts considered in this study were circular with their axes in a common plane. Laminar stagnation pressure loss coefficients were determined by simulating incompressible flow through 475 different geometries and flow condition combinations. In all cases, the flow was laminar in the inlet and outlet ducts with a Reynolds number of 15 in the inlet duct. Simulations of the dividing flow geometries were done using FLUENT and a custom written computer code, which automated the process of creating the three-dimensional flow geometries. The outputs, pressure and velocity distributions at the inlet and outlets, were averaged over the circular ducts and then used to calculate pressure loss coefficients for each of the geometries and flow fraction scenarios simulated. The results for loss coefficient for the geometries considered ranged from 2.0 to 70. The loss coefficient for any geometry increased significantly as the outlet flow fraction increased. A consistent increase in loss coefficient was also observed as a function of decreasing outlet duct diameter. Less significant variation of the loss coefficient was observed as a function of the angles of the outlet ducts.

Analytical and Experimental Studies of Diffuser/Nozzle Valve-Less Micro-Pump

2008 ◽  
Author(s):  
Seiichi Tanaka ◽  
Shun Moriyama ◽  
Hiroshi Tsukamoto ◽  
Koji Miyazaki
Keyword(s):  
Pressure Loss ◽  
Experimental Studies ◽  
Measured Data ◽  
Dimensionless Numbers ◽  
Physical Mechanisms ◽  
Micro Pump ◽  
Unsteady Operation ◽  
Loss Coefficients ◽  
Bernoulli’S Theorem ◽  
Simplified Analysis

A valve-less micro-pump was realized with just one diffuser/nozzle element. The pressure-loss in a nozzle is lower than that in a diffuser, and therefore one-way flow may be realized in the nozzle direction. The frequency characteristics and the pump characteristics are measured. Dimensionless numbers are introduced to rearrange the measured data and to understand the physical mechanisms of the micro-pump. Simplified analysis was done for unsteady operation of the pump by considering the channel geometries and pressure-loss coefficients based on Bernoulli’s theorem. The calculated pump characteristics agreed with the measured ones. Numerical calculations were made using the commercial CFD (computational fluid dynamics) code CFX. The calculated flow patterns showed differences between the diffuser and nozzle directions.

Flow Around Baffles

1984 ◽  
Vol 106 (4) ◽  
pp. 743-749 ◽  
Author(s):  
C. Berner ◽  
F. Durst ◽  
D. M. McEligot
Keyword(s):  
Flow Visualization ◽  
Water Flow ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Streamwise Direction ◽  
Loss Coefficients ◽  
Shell And Tube

Flow visualization, manometry, and laser-Doppler anemometry have been applied to approximately two-dimensional water flow around segmental baffles with baffle spacing/depth equal to 0.4, window cuts from 10 to 50 percent, and Reynolds numbers ranging from 600–10,500 in order to simulate important aspects relating to shellside flow in shell-and-tube heat exchangers. The main features of the flow (which is eventually periodic in the streamwise direction), development lengths, pressure loss coefficients, and mean and rms velocity distributions are presented.

Non-Steady Flow through a Gauze in a Duct

1965 ◽  
Vol 7 (4) ◽  
pp. 449-459 ◽  
Author(s):  
R. S. Benson ◽  
P. C. Baruah
Keyword(s):  
Steady Flow ◽  
Excellent Agreement ◽  
Pressure Loss ◽  
Internal Combustion Engines ◽  
Wave Action ◽  
Combustion Engines ◽  
Flow Through ◽  
Flow Pressure ◽  
Loss Coefficients ◽  
Flow Experiments

By using steady flow relations including pressure loss coefficients a method is developed for calculating wave action in a duct with a gauze. Both steady and non-steady flow experiments for five gauzes are described. The results of the non-steady flow tests showed excellent agreement between the predicted indicator diagrams, using the steady flow pressure loss coefficients, and the measured indicator diagrams. The methods described in the paper may be used by engine designers to predict the effect of gauzes or similar devices on the wave action in exhaust systems of internal combustion engines.

scholarly journals Preliminary Experimental Study on Pressure Loss Coefficients of Exhaust Manifold Junction

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Xiao-lu Lu ◽  
Kun Zhang ◽  
Wen-hui Wang ◽  
Shao-ming Wang ◽  
Kang-yao Deng
Keyword(s):  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Flow Ratio ◽  
Pressure Loss Coefficient ◽  
Loss Coefficients ◽  
Total Pressure Loss Coefficient ◽  
Mass Flow Ratio

The flow characteristic of exhaust system has an important impact on inlet boundary of the turbine. In this paper, high speed flow in a diesel exhaust manifold junction was tested and simulated. The pressure loss coefficient of the junction flow was analyzed. The steady experimental results indicated that both of static pressure loss coefficientsL13andL23first increased and then decreased with the increase of mass flow ratio of lateral branch and public manifold. The total pressure loss coefficientK13always increased with the increase of mass flow ratio of junctions 1 and 3. The total pressure loss coefficientK23first increased and then decreased with the increase of mass flow ratio of junctions 2 and 3. These pressure loss coefficients of the exhaust pipe junctions can be used in exhaust flow and turbine inlet boundary conditions analysis. In addition, simulating calculation was conducted to analyze the effect of branch angle on total pressure loss coefficient. According to the calculation results, total pressure loss coefficient was almost the same at low mass flow rate of branch manifold 1 but increased with lateral branch angle at high mass flow rate of branch manifold 1.

Pressure Losses and Limiting Reynolds Numbers for Non-Newtonian Fluids in Short Square-Edged Orifice Plates

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Butteur Ntamba Ntamba ◽  
Veruscha Fester
Keyword(s):  
Pressure Loss ◽  
Reynolds Numbers ◽  
Newtonian Fluids ◽  
Pressure Losses ◽  
Pressure Loss Coefficient ◽  
Stable Operating ◽  
Piping Systems ◽  
Laminar And Turbulent Flow ◽  
Loss Coefficients ◽  
Industrial Problem

Correlations predicting the pressure loss coefficient along with the laminar, transitional, and turbulent limiting Reynolds numbers with the β ratio are presented for short square-edged orifice plates. The knowledge of pressure losses across orifices is a very important industrial problem while predicting pressure losses in piping systems. Similarly, it is important to define stable operating regions for the application of a short orifice at lower Reynolds numbers. This work experimentally determined pressure loss coefficients for square-edged orifices for orifice-to-diameter ratios of β = 0.2, 0.3, 0.57, and 0.7 for Newtonian and non-Newtonian fluids in both laminar and turbulent flow regimes.

Pressure Loss Through Sharp 180 Deg Turns in Smooth Rectangular Channels

1984 ◽  
Vol 106 (3) ◽  
pp. 677-681 ◽  
Author(s):  
D. E. Metzger ◽  
C. W. Plevich ◽  
C. S. Fan
Keyword(s):  
Pressure Loss ◽  
Rectangular Cross Section ◽  
Reynolds Numbers ◽  
Internal Cooling ◽  
Turbine Engine ◽  
Pressure Distributions ◽  
Rectangular Channels ◽  
Flow Geometry ◽  
Loss Coefficients ◽  
Measured Pressure

Measured pressure distributions, pressure loss coefficients, and surface streamline visualizations are presented for 180 deg turns in smooth, rectangular cross-section channels. The flow geometry models situations that exist in multipass internal cooling of gas turbine engine airfoils. The turn geometry is characterized by parameters W*, the ratio of upstream and downstream channel widths; D*, the nondimensional channel depth; H*, the nondimensional clearance height at the tip of the turn; and R*, the nondimensional corner fillet radius. The present results cover a range of combinations of geometry parameters and Reynolds numbers to aid in prediction of coolant flow rates in present and future cooled airfoil designs.

Pressure loss of gaseous flow at a micro-tube outlet

2010 ◽  
Vol 225 (3) ◽  
pp. 649-657
Author(s):  
Y Horii ◽  
Y Asako ◽  
C Hong ◽  
J Lee
Keyword(s):  
Mach Number ◽  
Atmospheric Pressure ◽  
Pressure Loss ◽  
Stagnation Pressure ◽  
Loss Coefficient ◽  
Arbitrary Lagrangian Eulerian ◽  
Gaseous Flow ◽  
Pressure Loss Coefficient ◽  
Loss Coefficients ◽  
Energy Equations

The pressure loss of gaseous flow at a micro-tube outlet was investigated numerically. The numerical methodology is based on the arbitrary Lagrangian—Eulerian (ALE) method. Axis-symmetric compressible momentum and energy equations are solved to obtain the pressure loss coefficient of gaseous flow at a micro-tube outlet. Computed tube diameters are 50, 100, and 150μm. The stagnation pressure of upper stream of the tube is chosen in such a way that the Mach number at the tube outlet ranges from 0.1 to 1.2. The ambient (back) pressure is fixed at the atmospheric pressure. The pressure loss coefficients are compared with available experimental data for a conventionally sized tube. The effects of the Mach number and the tube diameter on the pressure loss coefficient are discussed and a correlation for the pressure loss coefficient is proposed.

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