Begell House Inc.
Heat Transfer Research
HTR
1064-2285
49
3
2018
HEAT TRANSFER IN VISCOPLASTIC BOUNDARY-LAYER FLOW FROM A VERTICAL PERMEABLE CONE WITH MOMENTUM AND THERMAL WALL SLIP: NUMERICAL STUDY
189-204
10.1615/HeatTransRes.2017018153
Annasagaram
Subba Rao
Department of Mathematics, Madanapalle Institute of Technology and Science, Madanapalle —
517325, India
V. Ramachandra
Prasad
Department of Mathematics, Madanapalle Institute of Technology and Science, Madanapalle,
India
V. Naga
Radhika
Department of Mathematics, GITAM University Bangalore Campus, Bangalore — 561203, India
O. Anwar
Bég
Multi-Physical Engineering Sciences Group, Aeronautical and Mechanical
Engineering Department, School of Science, Engineering and Environment
(SEE), Newton Building, University of Salford, Manchester, M54WT, UK
thermal convection
slip condition
Keller-box numerical method
skin friction
Nusselt number
cone
Casson viscoplastic model
boundary layers
buoyancy
suction
A mathematical model is presented for laminar free convection boundary-layer flow of a Casson viscoplastic non-Newtonian fluid external to a vertical penetrable circular cone in the presence of thermal and hydrodynamic slip conditions. The cone surface is maintained at a nonuniform surface temperature. The boundary layer conservation equations, which are parabolic in nature, are transformed into nondimensional form via appropriate similarity variables, and the emerging boundary-value problem is solved computationally with the second order accurate implicit Keller-box finite-difference scheme. The influence
of velocity (momentum) slip, thermal slip, and Casson non-Newtonian parameter on velocity, temperature, skin friction,
and Nusselt number are illustrated graphically. Validation of solutions with earlier published work is included. The computations show that the flow near the cone surface is strongly decelerated with increasing momentum slip whereas the temperature and thermal boundary-layer thickness increased. Increasing Casson parameter generally decelerates the flow and also decreases temperatures. Both velocity and thermal boundary-layer thickness are reduced at a higher Prandtl number. The study is relevant to petrochemical engineering (polymer) processing systems.
A CORRELATION BETWEEN TWO- AND THREE-DIMENSIONAL NUMERICAL INVESTIGATION OF HEAT TRANSFER OVER A BACKWARD-FACING STEP INFLUENCED BY EHD FLOW
205-217
10.1615/HeatTransRes.2017016855
K.
Mostajiri
Mechanical Engineering Department, Faculty of Engineering, University of Guilan, Rasht, Iran
Nima
Amanifard
University of Guilan
Hamed Mohaddes
Deylami
Faculty of Technology and Engineering, East of Guilan, University of Guilan, Rudsar, Iran
electrohydrodynamic
backward-facing step
heat transfer
numerical investigation
In this paper, 2D and 3D numerical simulations were carried out to study the effect of EHD flow on the flow and temperature fields over a backward-facing step. The electrical field is generated by a wire electrode charged with high voltage. The effect of electric field on the average Nusselt number is studied for both approaches. The average Nusselt numbers obtained from the 3D simulation are lower than the corresponding values obtained by the 2D approaches. Based on these results, two formulas are presented. A corrective correlation between the 2D and 3D simulation results is proposed to calculate the
average Nusselt number.
DESIGN OF VENTILATION SYSTEMS AND FIRE SCENARIOS IN MINES AND ESTABLISHING THE SAFETY ZONE WITH ANALYSIS OF ESCAPE ROUTES
219-233
10.1615/HeatTransRes.2017019130
Selçuk
Keçel
Gazi University, Faculty of Architecture, Department of Industrial Product Design, Maltepe,
Ankara, Turkey
fire modeling
ventilation system design
modeling of safety zone
In this study, fire scenarios that may occur in mines have been prepared by means of Computational Fluid Dynamics
(CFD), and the results obtained from modifying the direction and velocity of airflow in tunnel entrances and exits have
been examined. The operating parameters of the ventilation system (air velocity and direction) were taken as a basis in the underground mine model, and a fire pool was prepared. Fire analyses with heat release rate (HRR) values of 1, 2, 3, 4, and 6 MW were conducted based on different scenarios. Temperature distributions and smoke movements within the tunnel were analyzed. An attempt was made to create scenarios to provide workers with correct guidance in the event of a fire, based on the results obtained from the mine model. It was seen in the created scenarios that temperature distribution and smoke movement have quite dynamic structures in a time-dependent manner. Furthermore, the change in the differences of the distances to the so-called safety zones for workers, where fire smoke or temperature increase are absent, was examined.
As a result of this study, the effects that may arise in the mining sector related to fire were reviewed, and the importance of critical decisions that are required at the moment of an accident is illustrated by means of diagrams. This study revealed that a correct response in the entrance and exit conditions allows adequate time for evacuation of all workers, while an incorrect response could cause an increase in the expansion rate of poisonous gases stemming from the fire.
EXPERIMENTAL INVESTIGATION OF AXIAL HEAT TRANSFER AND ENTRANCE EFFECT IN RANDOMLY PACKED BEDS BY A NAPHTHALENE SUBLIMATION TECHNIQUE
235-253
10.1615/HeatTransRes.2018016318
Jingyu
Wang
Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, P.R. China
Yan
Liu
Key Laboratory of Thermal-Fluid Science and Engineering, Ministry of Education, Xi'an Jiaotong
University, Xi'an, Shaanxi, 710049, P.R. China
Jian
Yang
MOE Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, P.R. China
Yitung
Chen
Department of Mechanical Engineering Director, Center for Energy Research University of Nevada-Las Vegas 4505 S. Maryland Parkway, MS 454027
Las Vegas, NV 89154-4027
Qiuwang
Wang
MOE Key Laboratory of Thermo-Fluid Science and Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, No. 28 Xianning West Road, Xi'an, Shaanxi 710049, P.R. China
randomly packed bed
naphthalene sublimation
convective heat transfer
entrance effect
discrete element method
axial porosity distribution
Local average heat transfer characteristics along the axial direction in randomly packed beds are investigated experimentally by using a naphthalene sublimation technique and the heat-to-mass transfer analogy. Packed beds of three particle diameters of 12 mm, 10 mm, and 8 mm are investigated, respectively. The relationship between the Nusselt number along the axial direction and the axial porosity distribution is analyzed, and the influence of the entrance effect on the overall heat transfer is explored. In the present paper, the axial porosity distribution is obtained by numerical analysis of a randomly
packed bed generated by a discrete element method (DEM). The results of pressure drop show that most experimental points
lie within ± 20% deviations of the Ergun equation and that the pressure distribution along the axial direction decreases almost linearly. Furthermore, it is found that in the axial direction, the Nusselt number increases in the first three layers and stays almost constant after that, where the heat transfer is fully developed. The development of Nusselt number along the axial direction can be attributed to the change of axial porosity distribution and to the alterative turbulence. Besides, the Nusselt number in the first layer is about 60–80% of the average Nusselt number in the bulk of the packed bed in the present
Reynolds number range (373–2867). Finally, the entrance effect can have an influence on the overall Nusselt number
when the packed bed is shorter than 8–16 particle diameters.
ANALYSIS OF TRANSIENT TEMPERATURE FIELD CHARACTERISTICS INSIDE A LARGE-SCALE THERMAL CYCLING TEST CAVITY FOR SPACECRAFT
255-273
10.1615/HeatTransRes.2018019407
Guang
Yang
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, 200240, China
Liangjun
Zhang
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, 200240, China; Shanghai Key Laboratory of Spacecraft Mechanism, Aerospace System Engineering Shanghai, 201108 Shanghai, China
Jingyi
Wu
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, 200240, China
Yiye
Huang
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, 200240, China
Aifeng
Cai
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, 200240, China
thermal cycling test
temperature uniformity
turbulent mixed convection
buoyancy
rectangular cavity
The transient temperature field characteristics inside the test cavity of a large-scale thermal cycling test system for space-craft were investigated by numerical simulation as well as experiments conducted in a full-scale system. The temperature profile in a cooling or heating process was found to be strongly affected by the buoyancy force. The temperature profile was vertically stratified if buoyancy assisted the inlet flow while it was unstable if the buoyancy opposed the inlet flow. The influences of inlet flow rate (4 × 103 ≤ Re ≤ 1 × 105), cooling or heating rate (± 3 K/min ≤ Δ ≤ ± 20 K/min), and thermal
conductivity of the solid walls (0 ≤ ks ≤ ∞) on the temperature uniformity, heating/cooling efficiency, and energy losses were also investigated in detail, providing useful parameters for the design and operation of large-scale thermal cycling test systems at high temperature differences.
VARIATIONAL EQUATION OF NON-FOURIER HEAT CONDUCTION
275-285
10.1615/HeatTransRes.2018015988
Xiaomin
Zhang
Department of Engineering Mechanics, Chongqing University, Chongqing, 400044, P.R.China
Song
Peng
Department of Engineering Mechanics, Chongqing University, Chongqing, 400044, P.R.China
Long
Zhang
Department of Engineering Mechanics, Chongqing University, Chongqing, 400044, P.R.China; Department of Theoretical and Applied Mechanics, Chongqing University of Science
and Technology, Chongqing, 401331, P.R.China
Zimin
Yan
Department of Engineering Mechanics, Chongqing University, Chongqing, 400044, P.R.China
Yuan
Liang
School of Foreign Language, Chongqing University of Science and Technology, Chongqing,
401331, P.R.China
Bo
Yan
Department of Engineering Mechanics, Chongqing University, Chongqing, 400044, P.R.China
non-Fourier heat conduction
variational equation
relaxation time
The variational equation containing the finite relaxation time was deduced by promoting Biot's variational equation for non-Fourier heat conduction in the finite relaxation model as well as for non-Fourier media in the Cattaneo−Vernotte (CV) model. In addition, the form in the generalized coordinates and the expression with the potential function corresponding to the variational equation were obtained. The employed variational equation and the heat-affected zone in the semi-infinite space under the influence of a step thermal pulse were investigated. A comparison of the relationships of heat distribution
and time between the Fourier and non-Fourier models indicates that the propagation velocity is underestimated in the Fourier law under the condition of ultrashort duration. The relationships between the heat-affected zone and the relaxation time, relaxation zone, and duration were discussed as well as the expression of the bounded temperature gradient was obtained.