Convective heat transfer for a nonlinear viscoplastic medium in a circular pipe

1970 ◽  
Vol 19 (5) ◽  
pp. 1386-1393 ◽  
Author(s):  
Z. P. Shul'man ◽  
V. M. Gorislavets ◽  
V. A. Rozhkov ◽  
V. V. Uryadova
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Viscoplastic Medium ◽  
Circular Pipe

scholarly journals CONVECTIVE HEAT TRANSFER AND POWER SAVING APPLICATION OF SI BASED NANOPARTICLES IN A CIRCULAR PIPE

2020 ◽  
Vol 50 (4) ◽  
pp. 321-327
Author(s):  
Md Insiat Islam Rabby ◽  
Farzad Hossain ◽  
S.A.M. Shafwat Amin ◽  
Tazeen Afrin Mumu ◽  
MD Ashraf Hossain Bhuiyan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Base Fluid ◽  
Volume Fraction ◽  
Numerical Study ◽  
Convective Heat Transfer Coefficient ◽  
Circular Pipe ◽  
Working Fluid ◽  
Pumping Power

A numerical study of laminar forced convection heat transfer for the fully developed region inside a circular pipe filled with Si based nanoparticle is presented for investigating the parameters of heat transfer. Four Si based nanoparticles Si, SiC, SiO2, Si3N4 with 1-5% volume fraction have been mixed with water to prepare nanofluids which is used for working fluid to flow over a circular pipe with 5mm diameter and 700mm length. Heat transfer characteristics and pumping power have been calculated at fully developed region with constant heat flux condition on pipe wall to identify the heat transfer enhancement ratio and pumping power reduction ratio among base fluid water and each nanofluids. It is worth mentioning that utilizing SiC nanoparticle shows not only the highest increment of Nusselt number and convective heat transfer coefficient but also the highest decrement of pumping power requirement and FOM in comparison to the base fluid.

A Numerical Study of Forced Convective Heat Transfer Characteristics of Supercritical Fluid in a Horizontal Circular-Pipe

2020 ◽  
Author(s):  
Alaba Bamido ◽  
V. K. Dhir ◽  
V. Prasad ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Convective Heat Transfer ◽  
Supercritical Fluid ◽  
Convective Heat ◽  
Circular Pipe ◽  
Heat Transfer Characteristics ◽  
Forced Convective Heat Transfer ◽  
Transfer Characteristics ◽  
Thermo Physical Properties

Abstract Analytical and computational studies were performed to compare the convective heat transfer characteristics of a supercritical fluid in a circular pipe for horizontal flow configuration. The motivation of this study was to explore the efficacy of heat exchangers involving forced convective heat transfer of supercritical fluids (tube side) integrated with air cooling (i.e., in free convection). The goal of this study was to determine the forced convective heat transfer characteristics of supercritical carbon dioxide (sCO2) in air-cooled tube heat-exchangers. The scope of this study was limited to the values of Reynolds number (Re) varying from 10∼104 (i.e., involving both laminar and turbulent flow correlations for analytical formulations and computational models). The predictions for the forced convection heat transfer characteristics (e.g., heat transfer coefficient, pressure drop, volume flow rate, mass flow rate, pump penalty/ pumping power/ required compressor ratings, Nusselt number (Nu) etc.) were obtained using analytical formulations and compared with that of computational models. The flow configurations involved a horizontal circular pipe of 1 m length and with different diameters (ranging from 1 mm – 10 mm). The supercritical properties of the working fluid were investigated at a fixed value of reduced pressure (Pr = 1.1) and a fixed range of temperatures, i.e., T, varying from 550 to 750 [K]. The fluid properties were gleaned from the NIST property database (available online at the NIST website). For the second part of this study, the forced convective heat transfer characteristics of sCO2 flowing in a horizontal tube with circular cross-section were studied using analytical correlations (e.g., Dittus-Boelter and Gnielinski correlation) and validated using commercial tools for Computational Fluid Dynamics (CFD)/ Computational Heat Transfer (CHT), i.e., using Fluent® (Ansys®). Validation of the analytical predictions using CFD/ CHT tools was performed to ascertain the level of uncertainty in the predicted results due to acute variation of the thermo-physical properties as a function of temperature and pressure (since the thermo-physical properties are expected to oscillate widely in the vicinity of the critical point). In the simulations, the inlet temperature for the supercritical fluid (sCO2) was fixed (at Tin = 700 [K]), and the ambient temperature was also fixed (at Tamb = 300 [K]), for the purpose of determining the values of the natural convection coefficients (external to the tube). Constant values of the thermo-physical properties of sCO2 at the mean film temperature (and corresponding to the inlet pressure values) were assumed for obtaining the analytical predictions. The results from the CFD / CHT simulations helped to quantify the level of uncertainties in the assumption of constant properties (in the analytical model) at different values of Reynolds number (i.e., for both laminar and turbulent flow regimes).

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