Three-dimensional numerical simulation of external fluid flow and heat transfer of a heat exchanger in a wind tunnel using porous media model

Journal of Thermal Analysis and Calorimetry - Notwithstanding the widespread use of wind tunnel to investigate the performance of radiators and heat exchangers, has never been considered a...     

Hybrid conduction,convection and radiation heat transfer simulation in a channel with rectangular cylinder

Journal of Thermal Analysis and Calorimetry - The innovation of this study is to investigate the combination effect of thermal radiation and convection in the hybrid heat transfer between solid and...     

Numerical investigation of mixed convection heat transfer behavior of nanofluid in a cavity with different heat transfer areas

Journal of Thermal Analysis and Calorimetry - The main purpose of this research is the numerical modeling of laminar mixed convection heat transfer inside an open square cavity with different heat...     

Magneto-hydrodynamical numerical simulation of heat transfer in MHD stagnation point flow of Cross fluid model towards a stretched surface

Here formulation and computations are presented to introduce the novel concept of activation energy in chemically reacting stagnation point flow towards a stretching sheet. Constitutive expression for Cross liquid is taken into account. Magnetic field is utilised in the transverse direction. Application of suitable variables generates the non-linear differential systems. Numerical solution by Runge–Kutta–Fehlberg approach is presented. Characteristics for the significant variables like Weissenberg number, Hartmann number, Schmidt number, activation energy chemical reaction parameter, velocity ratio parameter and Prandtl number on the physical quantities are addressed through graphs and tables. Our computations reveal that species concentration rises via larger activation energy parameter whereas it decays when Schmidt number is incremented. The Weissenberg number has opposite characteristics for local Nusselt and Sherwood numbers when compared with surface drag force.     

Intensification of heat transfer in a liquid film evaporator

Influence of the heat exchanger shape on the heat transfer efficiency investigated. Heat transfer efficiency of two vertical pipe-in-pipe heat exchangers, one with a straight wall and the other with a twisted wall were compared. Both heat exchangers worked on the principle of liquid falling film. Electric transformer oil was used as the heated liquid and water vapor at atmospheric pressure was used as the heating agent. Oil was just heated, not evaporated during the experiments. Oil inlet and outlet temperature were measured at six different oil mass flows. Heat flux and heat flux density in the straight- and twisted-wall heat exchangers were compared. Mathematical model was built to verify the possibility of the oil outlet temperature prediction.     

射流流化床煤气化炉中气固流动和传热、传质的CFD模拟研究

通过双流体模型对射流流化床煤气化炉进行了CFD（Computational Fluid Dynamics,计算流体力学）模拟。模拟着重分析了流化床气化炉气固流动的特性和传质、传热过程。结果表明,流化床中气固两相的传热、传质过程与气体和颗粒的运动特性密切相关。     

Iteration-free calculation of heat transfer coefficients in heat exchangers

If a heat transfer coefficient is dependent on the wall temperature it is usually calculated by an iterative technique. Starting from an earlier iteration-free method which was developed for air-cooled heat exchangers and the cooling of viscous oils, an improved procedure is derived for convective cooling or heating of liquids. Furthermore, it is shown how the local heat transfer coefficient can also be calculated without iteration in the corresponding cases of combined radiation and convection.     

Fluctuating hydrodynamics for multiscale modeling and simulation: Energy and heat transfer in molecular fluids

This work illustrates that fluctuating hydrodynamics (FHD) simulations can be used to capture the thermodynamic and hydrodynamic responses of molecular fluids at the nanoscale, including those associated with energy and heat transfer. Using all-atom molecular dynamics (MD) trajectories as the reference data, the atomistic coordinates of each snapshot are mapped onto mass, momentum, and energy density fields on Eulerian grids to generate a corresponding field trajectory. The molecular length-scale associated with finite molecule size is explicitly imposed during this coarse-graining by requiring that the variances of density fields scale inversely with the grid volume. From the fluctuations of field variables, the response functions and transport coefficients encoded in the all-atom MD trajectory are computed. By using the extracted fluid properties in FHD simulations, we show that the fluctuations and relaxation of hydrodynamic fields quantitatively match with those observed in the reference all-atom MD trajectory, hence establishing compatibility between the atomistic and field representations. We also show that inclusion of energy transfer in the FHD equations can more accurately capture the thermodynamic and hydrodynamic responses of molecular fluids. The results indicate that the proposed MD-to-FHD mapping with explicit consideration of finite molecule size provides a robust framework for coarse-graining the solution phase of complex molecular systems.     

LBM simulation of MHD nanofluid heat transfer in a square cavity with a cooled porous obstacle: effects of various temperature boundary conditions

Journal of Thermal Analysis and Calorimetry - Nanofluid natural convection inside a cavity with a porous square obstacle in the presence of magnetic field is simulated by lattice Boltzmann method....     

Effect of Reynolds number on heat transfer and flow for multi-oxide nanofluids using numerical simulation

A numerical simulation model for laminar flow of nanofluids in a pipe with constant heat flux at the wall has been built to study the effect of Reynolds number on heat transfer and pressure loss. The investigation was performed for metallic oxide and multi-oxide nanoparticles suspended in water. The thermal conductivity and dynamic viscosity were measured for a range of temperature (10–60 °C) and volume fraction of multi-oxide nanofluid. Comparison of the thermal conductivity for monocular oxide and multi-oxide nanofluids reveals a new way to control the enhancement in nanofluid conductivity. The numerical results obtained were compared with existing well-established correlations. The predictions of the Nusselt number for nanofluids are in agreement with the Shah correlation, and the deviation in the results is less than 1 %. It is found that the pressure loss increases with the Reynolds number, nanoparticle density, and volume fraction for multi-oxide nanoparticles. However, the flow demonstrates enhancement in heat transfer which improves with increasing Reynolds number of the flow.     

Nitro-phenylalanine: a novel sensor for heat transfer in peptides

Femtosecond IR-pump-IR-probe experiments with independently tunable pulses are used to monitor the ultrafast response of selected IR absorption bands to vibrational excitation of other modes of Fmoc-nitrophenylalanine. The absorptions of both NO(2)-bands change rapidly within <2 ps upon excitation of other vibrational modes. The results point to considerable coupling between the monitored NO(2) modes and the initially excited modes or low-frequency modes. The latter are populated by a rapid energy redistribution process. The strong IR absorption of the NO(2) stretching bands and the intense coupling to other modes makes the nitro group of nitrophenylalanine a sensitive monitor for vibrational energy arriving at this amino acid.     

Hydrodynamics and heat transfer in a plasma spouted bed reactor

The literature reveals very little intformation about plasma spouted bed hydrodynamics. Spouting of corindon particles with diameters ranging from 0.4 to 3.36 mm with argon plasma was conducted in a 90-mm-diameter column in the temperature range 300–1300°C. It was found that the maximum spoutable height (H_m) decreases with increasing particle diameter and decreasing mean bed temperature. A relation between the inlet plasma velocity and H_m is proposed. Concerning heat transport phenomena in the annulus, measurements and calculations indicate a large axial diffusivity but a poor radial mixing. Typical values of D_z and D_r are proposed on the basis of an identification procedure.Notation Ar Archimede number - Ar d ³ p (p — f) _f g ² - C_p specific heat - d_p particle diameter - d_e core diameter (or spout diameter) - D_i fluid inlet orifice diameter - D_e column diameter - D_r and D_z radial and axial diffusivity, respectively - g acceleration due to gravity - H packed static bed height - H_b bed height - H_m maximum spoutable bed height - P power     

Experimental study on forced convection heat transfer of a nanofluid in a heat exchanger filled partially porous material

Journal of Thermal Analysis and Calorimetry - Heat transfer of MgO-EG nanofluid flowing in a double tube heat exchanger with an inner tube containing a partial porous material under laminar and...     

Turbulent heat transfer in tubular heat exchangers with twisted tape

Journal of Thermal Analysis and Calorimetry - Enhancing heat transfer in heat exchangers has gained attention of researchers for many years because of reduction in costs of generating heat...     

Three-dimensional heat transfer in nonlinear flow: a FEM computational approach

Journal of Thermal Analysis and Calorimetry - Finite element simulations for the dynamics of Casson fluid flow over time-dependent two-dimensional stretching sheet subjected to magnetic field and...     

Melting heat transfer in hybrid nanofluid flow along a moving surface

Journal of Thermal Analysis and Calorimetry - The impact and capability of Cu–Al $$_2$$ O $$_3$$ /water nanoliquid as the heat transfer fluid are numerically investigated along a moving...     

Local heat transfer downstream of a two-element flow control orifice

Experiments were performed to determine the heat transfer characteristics of a turbulent pipe flow downstream of a flow control orifice. The orifice consisted of an orifice plate followed by an abrupt expansion. A total of fifty-four geometric variants were tested. The working fluid was water, with Prandtl number 7, and the Reynolds number range was from 50, 000 to 125, 000. The maximum Nusselt numbers observed were 3 to 5 times the value for the corresponding fully-developed flows.