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

2021 ◽  
Author(s):  
Debjyoti Banerjee ◽  
Alaba Bamido ◽  
Vijay Dhir ◽  
Vish Prasad
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Supercritical Fluid ◽  
Convective Heat ◽  
Numerical Study ◽  
Circular Pipe ◽  
Heat Transfer Characteristics ◽  
Forced Convective Heat Transfer ◽  
Transfer Characteristics

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).

Experimental Convective Heat Transfer With Nanofluids

2008 ◽  
Author(s):  
S. Kabelac ◽  
K. B. Anoop
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Turbulent Regime ◽  
Heat Transfer Characteristics ◽  
Forced Convective Heat Transfer ◽  
Transfer Characteristics

Nanofluids are colloidal suspensions with nano-sized particles (<100nm) dispersed in a base fluid. From literature it is seen that these fluids exhibit better heat transfer characteristics. In our present work, thermal conductivity and the forced convective heat transfer coefficient of an alumina-water nanofluid is investigated. Thermal conductivity is measured by a steady state method using a Guarded Hot Plate apparatus customized for liquids. Forced convective heat transfer characteristics are evaluated with help of a test loop under constant heat flux condition. Controlled experiments under turbulent flow regime are carried out using two particle concentrations (0.5vol% and 1vol %). Experimental results show that, thermal conductivity of nanofluids increases with concentration, but the heat transfer coefficient in the turbulent regime does not exhibit any remarkable increase above measurement uncertainty.

A Numerical Study on the Convective Heat Transfer Characteristics of Pulsed Impingement Drying

2012 ◽  
Vol 30 (10) ◽  
pp. 1056-1061 ◽  
Author(s):  
Ying Jiang ◽  
Peng Xu ◽  
Arun S. Mujumdar ◽  
Shuxia Qiu ◽  
Zhouting Jiang
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Numerical Study on Supercritical CH4/N2 Cooling in a Horizontal Tube

2012 ◽  
Author(s):  
Zhongxuan Du ◽  
Wensheng Lin ◽  
Anzhong Gu
Keyword(s):  
Heat Transfer ◽  
Nitrogen Content ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Horizontal Tube ◽  
Buoyancy Effect ◽  
Heat Transfer Characteristics ◽  
Bottom Line ◽  
Transfer Characteristics

Coalbed methane (CBM) is a kind of mixed gas with the principal component of methane and nitrogen. Supercritical convective heat transfer of CH4/N2 cooled in horizontal circular tubes is one of the most important heat transfer processes during CBM liquefaction. In this paper, supercritical CH4/N2 cooling has been numerically investigated in a horizontal tube by using the low Reynolds number turbulence model proposed by Lam and Bremhorst. The study first focuses on the effect of nitrogen content on CBM heat transfer characteristics. The results indicate that supercritical convective heat transfer of CBM is mainly affected by the fact that the CBM properties change with nitrogen content. Then the study focuses on the buoyancy effect on heat transfer characteristics at different mass fluxes, heat fluxes and pressures. The results show that buoyancy effect increases with the decrease of mass flux or with the increase of heat flux, and the relationship Gr/Re2.7 predicts the buoyancy effect onset better than Gr/Re2. When the buoyancy effect is considerably strong, buoyancy effect on heat transfer in the top line of the horizontal circular tube is equivalent to buoyancy-opposed heat transfer, and buoyancy effect on heat transfer in the bottom line to buoyancy-aided heat transfer. The correlation of buoyancy-opposed heat transfer proposed by Bruch et al. predicts well for the supercritical heat transfer of methane. When the buoyancy effect is negligible, the calculated results agree well with the Gnielinski correlation.

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