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Fluid Mechanics
Published in Yeong Koo Yeo, Chemical Engineering Computation with MATLAB®, 2020
The Fanning friction factor f is related to the Reynolds number NRe through a set of correlations, and depends on whether the flow regime is laminar, transitional, or turbulent. A simple relation between f and NRe can be expressed as f=aNReb where a and b are constants. The friction factor is affected by the roughness of the surface at a high Reynolds number (NRe≥2000).
Motor Power Losses
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
There are two types of friction factors used in the literature: Darcy–Weisbach friction factor and Fanning friction factor. Darcy–Weisbach friction factor is commonly used in the Moody diagram for pipe friction flows, and Fanning friction factor is primarily used for rotating or swirling flows [10.39]. Obviously, for electric rotating machines, the Fanning friction factor is more appropriate.
Parametric study of vortex generators on a fin-and-tube heat exchanger
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Koldo Portal-Porras, Unai Fernandez-Gamiz, Ekaitz Zulueta, Roberto Garcia-Fernandez, Oscar Irigaray
Pressure drop is a very relevant parameter, since the greater the pressure difference between the inlet and outlet, the greater the energy consumed to maintain the desired flow. To perform a meaningful comparison between cases, Fanning friction factor () is evaluated, which determines the pressure drop at a given flow rate and geometry. The plot from Figure 11a provides a comparison of the pressure drop, and the plot Figure 11b a comparison of .
Experimental Characterization of a Compact Milli-Channel Heat Exchanger for Liquid–Liquid Heat Transfer
Published in Heat Transfer Engineering, 2020
Jean-François Portha, Guillaume Henry, Alexandra Père-Gigante, Jean-Marc Commenge
To characterize the MCHE, a set of four differential equations describing the profiles of temperature and pressure of each fluid is established. Given the counter-current configuration, the boundary conditions and the system of equations consist in a two-point boundary value problem solved numerically by the Matlab software. To integrate the energy and pressure balances, the calculation of a convective heat transfer coefficient and of a Fanning friction factor respectively are necessary. Different forms of correlations of Nusselt number may exist (cf. Table 2). After different considerations, two forms of correlation are selected: where and are parameters to identify by optimization. The same correlation of Nusselt number is used for both fluids. In a general way, the Fanning friction factor depends on the Reynolds number. In laminar flow conditions, the product of the friction factor by the Reynolds number is theoretically equal to a constant depending on the geometry: where is also a parameter to identify by optimization. By considering Eq. (21), and introducing the Fanning friction factor as well as the dynamic viscosity, the differential equations describing the pressure profiles of the hot and cold fluids can be determined together with the corresponding boundary conditions: where and respectively, denote the total cross sections of hot and cold fluids. Despite the insulation of the heat exchanger, heat losses are not completely avoided and have to be taken into account in the model. The heat losses can be estimated from experiments through an overall heat balance applied to the heat exchanger: where represents an enthalpy power. The enthalpy depends on the heat capacity which can be estimated either at the fluid inlet or at the fluid outlet. For the considered experiments, the hot and cold temperatures range from 10 °C up to 78 °C. Over this range, the specific heat capacity of water changes by only 0.7% with respect to its mean value, and this deviation is less than 10% for the oil. Assuming that they are constant over this temperature range, the specific heat capacities, for each fluid, are calculated at the arithmetical average temperature between inlet and outlet. The spatial distribution of the heat losses along the heat exchanger is supposed to be uniform. Heat losses can therefore be considered as a negative heat source in the heat balance applied to the hot fluid, which becomes: