Single Phase Compressible Steady Flow in Pipes

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
David Hullender ◽  
Robert Woods ◽  
Yi-Wei Huang
Keyword(s):  
Heat Transfer ◽  
Mass Velocity ◽  
Single Phase ◽  
Laboratory Data ◽  
Iterative Solution ◽  
Gas Temperature ◽  
Flow Conditions ◽  
Explicit Equation ◽  
Adiabatic Flow ◽  
Transfer Ratio

In general, the computation of single phase subsonic mass velocity of gas flowing through a pipe requires a computerized iterative analysis. The equations for the friction factor for laminar and turbulent flow are used to obtain explicit equations for the subsonic mass velocity as a function of the pressures at the ends of a pipe. Explicit equations for mass velocity are presented. Included within the equations is a heat transfer ratio, which can vary between 0 for adiabatic flow conditions to 1 for isothermal flow conditions. The use of this heat transfer ratio also enables the formulation of an explicit equation for the gas temperature along the pipe for nonisothermal flow conditions. The explicit equations eliminate the need for an iterative solution. Laboratory data are used to support the accuracy of the model.

Friction Losses and Heat Transfer in Laminar Microchannel Single-Phase Liquid Flow

2008 ◽  
Author(s):  
Vaˆnia Silve´rio ◽  
Anto´nio L. N. Moreira
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Flow ◽  
Single Phase ◽  
Wall Heat Flux ◽  
Oxide Thin Film ◽  
Flow Conditions ◽  
Constant Wall Heat Flux ◽  
Phase Liquid ◽  
Single Phase Liquid Flow

Many studies addressed the validity of macroscale theories to describe momentum and heat transfer in single phase in microtubes, but the results are often inconsistent. It is suggested that the fluid flow and heat transfer in microchannels without phase change is substantially different from that in larger channels. However, these discrepancies may be attributed to experimental uncertainties mainly due to the use of conventional measurement apparatus that are too big to implement in the tested system. Other researchers explain the microfluidic behavior with the ratio of surface forces to body forces which evolve inversely to the hydraulic diameter. The present work considers the use of a dedicated experimental facility built to allow the use of optical diagnostic and flow visualization techniques in heated microtubes and addresses the potential microscale effects which may arise for single phase flow conditions. The experiments encompass measurements of the pressure drop and the longitudinal temperature distribution in the fully developed single phase liquid flow established in circular and square cross section of channels made of borosilicate glass with hydraulic diameters from 50μm up to 500μm. The flow conditions consider a range of Reynolds number from 10 up to around 2500 and the use of diverse fluids to account for the effects of liquid properties. Namely, three distinct fluids were used: distilled water, methoxy-nonafluorobutane and methanol. For heat transfer studies, the channels are heated with constant wall heat flux supplied by Joule effect by means of external wall rf-PERTE deposition of Indium Oxide thin film. The thin transparent film showed good chemical stability in the range of temperatures up to 70°C, therefore indicating that the thermal boundary condition approximates a constant wall heat flux condition. The mass flux is varied from 60 to 3300kg.m−2·s−1 and the heat flux was set between 4 and 6kW.m−2. Experimental uncertainties are estimated to be below 14% for the friction factor and below 24% for Nusselt number; the former is dominated by inaccuracies in the diameter, while the second is dominated by temperature measurements.

Pressure Drop During Two-Phase Flow of R134a and R32 in a Single Minichannel

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Alberto Cavallini ◽  
Davide Del Col ◽  
Marko Matkovic ◽  
Luisa Rossetto
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Single Phase ◽  
Two Phase Flow ◽  
Vapor Flow ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Roughness Effects ◽  
Two Phase ◽  
Adiabatic Flow

Condensation in minichannels is widely used in air-cooled condensers for the automotive and air-conditioning industry, heat pipes, and compact heat exchangers. The knowledge of pressure drops in such small channels is important in order to optimize heat transfer surfaces. Most of the available experimental work refers to measurements obtained within multiport smooth extruded tubes and deal with the average values over the number of parallel channels. In this context, the present authors have set up a new test apparatus for heat transfer and fluid flow studies in single minichannels. This paper presents new experimental frictional pressure gradient data, relative to single-phase flow and adiabatic two-phase flow of R134a and R32 inside a single horizontal minitube, with a 0.96 mm inner diameter and with not-negligible surface roughness. The new all-liquid and all-vapor data are successfully compared against predictions of single-phase flow models. Also the two-phase flow data are compared against a model previously developed by the present authors for adiabatic flow or flow during condensation of halogenated refrigerants inside smooth minichannels. Surface roughness effects on the liquid-vapor flow are discussed. In this respect, the friction factor in the proposed model is modified, in order to take into consideration also effects due to wall roughness.

Single-phase heat transfer regimes in forced flow conditions under exponential heat inputs

2021 ◽  
Vol 174 ◽  
pp. 121294
Author(s):  
F. Chavagnat ◽  
R. Nop ◽  
N. Dorville ◽  
B. Phillips ◽  
M. Bucci
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Forced Flow ◽  
Flow Conditions

Frictional Pressure Drops During Vapour-Liquid Flow in Minichannels: Experimental Data and Modelling

2008 ◽  
Author(s):  
Alberto Cavallini ◽  
Davide Del Col ◽  
Marko Matkovic ◽  
Luisa Rossetto
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Single Phase ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Roughness Effects ◽  
Two Phase ◽  
Pressure Drops ◽  
Adiabatic Flow

Condensation in minichannels is widely used in air-cooled condensers for the automotive and air-conditioning industry, in heat pipes and other applications for cooling electronics. The knowledge of pressure drops in such small channels is important in order to optimize heat transfer surfaces. Most of the available experimental work refers to measurements obtained within multiport smooth extruded tubes and deal with the average values over the number of parallel channels. In this context, the present authors have set up a new test apparatus for heat transfer and fluid flow studies in single minichannels. This paper presents new experimental frictional pressure gradient data, relative to single-phase flow and adiabatic two-phase flow of R134a inside a single horizontal mini tube, with 0.96 mm inner diameter and with not-negligible surface roughness. The new all-liquid and all-vapour data are successfully compared against predictions of single-phase flow models. Also the two-phase flow data are compared against Cavallini et al. [1, 2] model, valid for adiabatic flow or for flow during condensation of halogenated refrigerants inside smooth minichannels. Surface roughness effects on the liquid-vapour flow are discussed. In this respect, the friction factor in the proposed model is modified, in order to take into consideration also effects due to wall roughness.

scholarly journals Approximate Analytical Analysis of Unsteady MHD Mixed Flow of Non-Newtonian Hybrid Nanofluid over a Stretching Surface

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 138
Author(s):  
Ali Rehman ◽  
Zabidin Salleh
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Base Fluid ◽  
Research Work ◽  
Hybrid Nanofluid ◽  
Stretching Surface ◽  
Optimal Homotopy Analysis Method ◽  
Analytical Analysis ◽  
Transfer Ratio ◽  
The Impact

This paper analyses the two-dimensional unsteady and incompressible flow of a non-Newtonian hybrid nanofluid over a stretching surface. The nanofluid formulated in the present study is TiO2 + Ag + blood, and TiO2 + blood, where in this combination TiO2 + blood is the base fluid and TiO2 + Ag + blood represents the hybrid nanofluid. The aim of the present research work is to improve the heat transfer ratio because the heat transfer ratio of the hybrid nanofluid is higher than that of the base fluid. The novelty of the recent work is the approximate analytical analysis of the magnetohydrodynamics mixed non-Newtonian hybrid nanofluid over a stretching surface. This type of combination, where TiO2+blood is the base fluid and TiO2 + Ag + blood is the hybrid nanofluid, is studied for the first time in the literature. The fundamental partial differential equations are transformed to a set of nonlinear ordinary differential equations with the guide of some appropriate similarity transformations. The analytical approximate method, namely the optimal homotopy analysis method (OHAM), is used for the approximate analytical solution. The convergence of the OHAM for particular problems is also discussed. The impact of the magnetic parameter, dynamic viscosity parameter, stretching surface parameter and Prandtl number is interpreted through graphs. The skin friction coefficient and Nusselt number are explained in table form. The present work is found to be in very good agreement with those published earlier.

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