Effect of wall conduction on the heat transfer characteristics of supercritical n-decane in a horizontal rectangular pipe for cooling of a scramjet combustor

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yong Li ◽  
Gongnan Xie ◽  
Bengt Ake Sunden
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Secondary Flow ◽  
Transverse Velocity ◽  
Convection Heat Transfer ◽  
Numerical Results ◽  
Fluid Temperature ◽  
Content Type ◽  
Scramjet Combustor ◽  
Thermo Physical Properties

Purpose The purpose of this paper is to numerically study the influence of wall conduction on the heat transfer of supercritical n-decane in the active regenerative cooling channels. Design/methodology/approach A horizontally placed rectangular pipe with a solid zone and another one without a solid zone were used. A drastic variation of thermo-physical properties was emphatically addressed. After the verification of mesh and turbulence models comparing with the experimental results, a mesh number of 4.5 M and the low Reynolds number SST k-ω turbulence model were chosen. The solution of the governing equations and the acquisition of the numerical results were executed by the commercial software FLUENT 2020 R1. Findings The numerical results indicate that there is a heat transfer deterioration (HTD) potential for the upper wall, lower wall and sidewall with the decrease of mass flux. Due to wall conduction, the distribution of the fluid temperature at spanwise-normal planes becomes uniform and this feature also takes advantage of the relatively uniform transverse velocity. For the streamwise-normal planes, the low fluid temperature appears close to the upper wall at the region near the sidewall and vice versa for the region near the centre. Undoubtedly, the secondary flow at the cross-section plays a crucial role in this process and the relatively cool mainstream is affected by the vortices. Originality/value This study warns that the wall conduction must be considered in the practical design and thermal optimization due to the sensibility of thermo-physical properties to the heat flux. The secondary flow caused by the buoyancy force (gravity) plays a significant role in the supercritical heat transfer and mixed convection heat transfer should be further studied.

scholarly journals Reconstruction of the thermal properties in a wave-type model of bio-heat transfer

2020 ◽  
Vol 30 (12) ◽  
pp. 5143-5167
Author(s):  
Moataz Alosaimi ◽  
Daniel Lesnic ◽  
Jitse Niesen
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Thermal Wave ◽  
Wave Model ◽  
Temperature Measurements ◽  
Dimensionless Parameters ◽  
Content Type ◽  
Boundary Temperature ◽  
Dimensional Parameters ◽  
Thermo Physical Properties

Purpose This study aims to at numerically retrieve five constant dimensional thermo-physical properties of a biological tissue from dimensionless boundary temperature measurements. Design/methodology/approach The thermal-wave model of bio-heat transfer is used as an appropriate model because of its realism in situations in which the heat flux is extremely high or low and imposed over a short duration of time. For the numerical discretization, an unconditionally stable finite difference scheme used as a direct solver is developed. The sensitivity coefficients of the dimensionless boundary temperature measurements with respect to five constant dimensionless parameters appearing in a non-dimensionalised version of the governing hyperbolic model are computed. The retrieval of those dimensionless parameters, from both exact and noisy measurements, is successfully achieved by using a minimization procedure based on the MATLAB optimization toolbox routine lsqnonlin. The values of the five-dimensional parameters are recovered by inverting a nonlinear system of algebraic equations connecting those parameters to the dimensionless parameters whose values have already been recovered. Findings Accurate and stable numerical solutions for the unknown thermo-physical properties of a biological tissue from dimensionless boundary temperature measurements are obtained using the proposed numerical procedure. Research limitations/implications The current investigation is limited to the retrieval of constant physical properties, but future work will investigate the reconstruction of the space-dependent blood perfusion coefficient. Practical implications As noise inherently present in practical measurements is inverted, the paper is of practical significance and models a real-world situation. Social implications The findings of the present paper are of considerable significance and interest to practitioners in the biomedical engineering and medical physics sectors. Originality/value In comparison to Alkhwaji et al. (2012), the novelty and contribution of this work are as follows: considering the more general and realistic thermal-wave model of bio-heat transfer, accounting for a relaxation time; allowing for the tissue to have a finite size; and reconstructing five thermally significant dimensional parameters.

Experimental Study on Heat Transfer of Supercritical Kerosene in a Vertical Upward Tube

2013 ◽  
Author(s):  
Dan Huang ◽  
Wei Li ◽  
Wei Zhang ◽  
Guo-Qiang Xu ◽  
Zhi Tao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Temperature ◽  
Physical Properties ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Supercritical Pressure ◽  
Fluid Temperature ◽  
Thermo Physical Properties

A research on the heat transfer performance of kerosene flowing in a vertical upward tube at supercritical pressure is presented. In the experiments, insights are offered on the effects of the factors such as mass flow rate, heat flux and pressure. It is found that increasing the mass flow rate could enhance the heat transfer performances, while increasing the working pressure will deteriorate the heat transfer. Besides, the effect of heat flux on heat transfer is complicated. Based on the analysis of experimental data, enhancement of heat transfer occurs when the inner wall temperature of tube is higher than pseudo-critical temperature while the bulk fluid temperature is lower than the pseudo-critical temperature. At the supercritical conditions, heat transfer is influenced by the significant changes in thermo-physical properties, thus accurate evaluations of the thermo-physical properties become the key for the supercritical heat transfer calculations. The extended corresponding-state principle could be used for evaluating the density and the transport properties of kerosene, including its viscosity and thermal conductivity, at different temperatures and pressures. In order to obtain the numerical values of the heat capacity, a Soave–Redlich–Kwong (SRK) equation of state is used. The correlation for predicting heat transfer in kerosene at supercritical pressure is established, the calculation results from this correlation are in good agreement with the experimental results.

Thermo-Physical Properties and Natural Convection Heat Transfer of Carbon Nano-Tube Fluid

2015 ◽  
Vol 41 (2) ◽  
pp. 121-130 ◽  
Author(s):  
Shintaro Suzuki ◽  
Terumi Inagaki ◽  
Yanrong Li ◽  
Koshi Harada ◽  
Yukitaka Izawa ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Physical Properties ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Carbon Nano Tube ◽  
Thermo Physical Properties

Effect of geometrical and temperature-dependence parameters on forced convection of a nanofluid in a micro-channel heat sink

2016 ◽  
Vol 13 (5) ◽  
pp. 399-406 ◽  
Author(s):  
Rabah Nebbati ◽  
Mahfoud Kadja
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Physical Properties ◽  
Forced Convection ◽  
Heat Sink ◽  
Volume Fraction ◽  
Micro Channel ◽  
Temperature Dependent ◽  
Content Type ◽  
Thermo Physical Properties

Purpose The purpose of this study is the numerical prediction of the thermal and hydraulic characteristics (Nusselt number and shear stress) of a forced convection laminar flow through a rectangular micro-channel heat sink, using constant and temperature-dependent thermo-physical properties. The effects of the solids volume fraction and the size of the micro-channel on heat transfer enhancement have also been investigated. Design/methodology/approach The authors use the flow of a water-Al2O3 nanofluid and a single-phase approach. The equations are solved using the commercial code Fluent Version 6.3. This code uses the finite volume approach to solve the equations subject to the boundary conditions, which govern three-dimensional conjugate convection-conduction heat transfer model. The physical domain was meshed using the code GAMBIT. The mesh used is non-uniform and was obtained by sweeping in the Z direction an X-Y surface meshed with QUAD/pave type cells. Findings The results clearly show that the inclusion of nanoparticles produces a considerable increase in the heat transfer. Also, the temperature-dependent models present higher values of local and average Nusselt number than in the case of constant thermo-physical properties, and an increase in the channel dimensions leads to an important increase in heat transfer. Consequently, we ensure a better cooling of the base of the micro-channel heat sink. Research limitations/implications Because of the settling of nanoparticles, the research results may not be generalized to high values of solids volume fraction. Therefore, researchers are encouraged to find other techniques of cooling when the heat loads exceed values that cannot be dissipated using nanonofluids. Practical implications The paper includes implications for the miniaturization of electronic devices such as in microprocessors or those used in robotics and automotive industries, where continually increasing power densities are requiring more innovative techniques of heat dissipation from a small area and small coolant requirements. Originality/value This paper shows the implementation of variable property nanofluid models in CFD commercial codes.

Thermo-Physical Properties of Magnetic Fluid and its Natural Convection Heat Transfer in a Horizontal Enclosed Rectangular Container

2014 ◽  
Vol 620 ◽  
pp. 461-467
Author(s):  
Yan Rong Li ◽  
Terumi Inagaki ◽  
Hikaru Saito ◽  
Masashi Abe
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Physical Properties ◽  
Magnetic Fluid ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Rectangular Container ◽  
The Heat Transfer Coefficient ◽  
Thermo Physical Properties

Thermo-physical properties of magnetic fluid were measured experimentally at various temperatures, in order to evaluate their temperature dependencies. Heat transfer by natural convection was also investigated in a horizontal enclosed rectangular container filled with the tested magnetic fluid. It was found that the heat transfer coefficient of the magnetic fluid keeps good agreement with the conventional heat-transfer correlation of natural convection heat transfer in a horizontal enclosed rectangular container by applying the values of thermo-physical properties obtained in the present work. Therefore, the measured thermo-physical properties are reliable and can be used as a thermo-physical database of the magnetic fluid.

scholarly journals A review on thermo-physical properties and heat transfer applications of single and hybrid metal oxide nanofluids

2019 ◽  
Vol 13 (2) ◽  
pp. 5182-5211
Author(s):  
W. H. Azmi ◽  
S. N. M. Zainon ◽  
K. A. Hamid ◽  
R. Mamat
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Heat Transfer Performance ◽  
Experimental Studies ◽  
Convection Heat Transfer ◽  
Transfer Performance ◽  
Engineering Systems ◽  
Different Types ◽  
Hybrid Metal Oxide ◽  
Thermo Physical Properties

Nanofluids have been widely explored by various investigators for different types of nanomaterials either the single nanoparticles or hybrid types. This is due to their advantages in thermal properties as well as contribution to the enhancement in the heat transfer performance. Numerous numbers of studies were performed mostly on oxide nanofluids until today. However, the review on oxide nanofluids and their applications is limited. Hence, this paper highlights the most recent development solely on the oxide nanofluids for heat transfer applications. In addition, a comprehensive review is carried out on the recent studies of thermo‑physical properties on oxide nanofluids and their heat transfer applications. The numerical and experimental studies related to forced convection heat transfer using oxide nanofluids were presented. Most of the literatures confirmed the capability of nanofluids to improve the heat transfer performance and simultaneously insignificant increments in pressure drop. Hence, the oxide nanofluids is recommended for applications in various engineering systems.

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