Begell House Inc.
Heat Transfer Research
HTR
1064-2285
48
10
2017
INFLUENCE OF HIGH ALTITUDE ON COMBUSTION EFFICIENCY AND RADIATION FRACTION OF HYDROCARBON FIRES
865-875
Haihang
Li
State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026, Anhui, P.R. China; Safety and Environment Institute, College of Quality & Safety Engineering, China Jiliang
University, Hangzhou 310018, P.R. China
Wei
Yao
Institute of Mechanics, Chinese Academy of Sciences, Beĳing 100190, P.R. China
Pan
Li
State Key Laboratory of Fire Science, University of Science and Technology of China,
Hefei 230026, Anhui, P.R. China
Zhihui
Zhou
State Key Laboratory of Fire Science, University of Science and Technology of China,
Hefei 230026, Anhui, P.R. China; China Waterborne Transport Research Institute, Beĳing 100088, P.R. China
Jian
Wang
State Key Laboratory of Fire Science, University of Science and Technology of China,
Hefei 230026, Anhui, P.R. China
Fire behaviors of three gaseous hydrocarbon fuels were experimentally measured and compared at two different altitudes (Lhasa city, 64 kPa at an altitude of 3650 m; Hefei city, 100 kPa at an altitude of 50 m). The heat release rates were calculated through a simplified thermochemistry based on the measured concentrations of O2 and CO2 in the exhaust duct,
then the combustion efficiencies and the radiation fractions were compared at the two altitudes. The heat release rates and combustion efficiencies were higher at lower pressure, and the overall temperatures of methane fires rose at a lower pressure. The radiative heat fluxes and radiation fractions at a low pressure were smaller than those at a normal pressure, while the smoke transmittances of acetylene fi res at a low pressure were higher.
NUMERICAL SIMULATION OF BOUNDARY LAYER TRANSITION FOR TURBINE BLADE HEAT TRANSFER PREDICTION
877-891
Athmane
Harizi
Mechanical Engineering Department, Science and Technology Faculty, University of Batna,
Algeria
A.
Gahmousse
Energetic and Turbomachinery Laboratory LET, University of Tebessa, 12002 Algeria
E.-A.
Mahfoudi
Mechanical Engineering Department, Science and Technology Faculty, University of Constantine,
Algeria
A.
Mameri
Mechanical Engineering Department, Science and Technology Faculty, University of Oum
El Bouaghi, 04000 Algeria
This paper deals with an external heat transfer numerical simulation for a two-dimensional transonic turbine blade cascade. We focused on the prediction of the laminar-turbulent boundary layer transition which can have an important effect on the distribution of the heat transfer around the turbine blade surface. The Reynolds-averaged Navier–Stokes equations (RANS) with the correlation-based transitional model developed by Menter and later modified by Langtry are solved. Comparisons with measurements for a highly loaded transonic turbine blade, experimentally studied on the von Karman Institute (VKI) test facility, show good agreement especially for the prediction of the transition onset for the all test cases considered. One of the major contributions of this paper is the implementation and evaluation of a set of new empirical correlations published recently in the literature. The results show that all correlations tested correctly predict the boundary layer transition onset with a relative difference for the heat flux computed in the fully turbulent region.
ANALYSIS OF THE HYDRAULIC AND THERMAL PERFORMANCES OF A MICROCHANNEL HEAT SINK WITH EXTENDED-NOZZLE IMPINGING JETS
893-914
Tingzhen
Ming
University of North Texas
School of Civil Engineering and Architecture, Wuhan University of Technology
J. L.
Gui
School of Energy and Power Engineering, Huazhong University of Science and Technology,
Wuhan, 430074, China
C.
Peng
School of Architecture and Urban Planning, Huazhong University of Science and Technology,
Wuhan, 430074, China
Y.
Tao
College of Engineering and Computing, Nova Southeastern University, Davie 33314, FL U.S.A.
A strong transverse main stream from upstream impinging jets will cause the flow direction of the downstream impinging jets to deflect greatly, which will significantly deteriorate the thermal performance of the microchannel heat sink with impinging jets. An idea of extending the length of the nozzles for the impinging jets has been introduced to avoid this negative effect and ultimately to enhance the thermal performance of microchannel heat sink jets. Mathematical models describing the fluid flow and heat transfer characteristics of the microchannel heat sink with extended-nozzle impinging jets (MHSEIJ) have been presented, and the thermal and hydraulic performances of the MHSEIJ with the lengths of extended nozzles being 0, 0.5, and 1.0 mm have been numerically investigated. From the results we can fi nd that: (1) the introduction of extended nozzles for impinging jets can greatly avoid the negative effect of the transverse main stream from upstream impinging jets; (2) increasing the length of extended nozzles will achieve better thermal performance of the MHSEIJ , accompanied by a reasonable increase in flow resistance; and (3) when Re is 18,000, the values of Nu are 258.15163 and 302.07749 for the
MHSEIJ, with Le being 0 mm and 1.0 mm, causing an increase of 17%.
INVERSE IDENTIFICATION OF EFFECTIVE THERMAL CONDUCTIVITY BASED ON SURFACE TEMPERATURE MEASUREMENT: AN ANALYSIS OF EFFECTING FACTORS
915-933
Chunli
Fan
College of Power Engineering, Naval University of Engineering, Wuhan 430033, People's Republic
of China
Lin
Zhang
College of Power Engineering, Naval University of Engineering, Wuhan 430033, People's Republic
of China
Wendou
Jia
College of Power Engineering, Naval University of Engineering, Wuhan 430033, People's Republic
of China
Li
Yang
College of Power Engineering, Naval University of Engineering, Wuhan 430033, People’s Republic
of China
Fengrui
Sun
College of Power Engineering, Naval University of Engineering, Wuhan 430033, People’s Republic
of China
A new conductivity-based method was presented in one of our previous papers (Fan et al., 2012) which provides a simple
and efficient solution to the inverse heat transfer problem on the geometry identification of inner plate surface with
defects. However, for this method there are still some problems, such as the error resources and the effecting factors of the method, that need to be discussed. This paper takes the core identification process of the method, i.e., the identification of the distribution of effective thermal conductivity, to analyze the above-mentioned problems. Based on a series of numerical experiments, we can draw the following conclusions (also applicable for the conductivity-based method): the method does not magnify the temperature measurement error; the error in the identification result comes from the inverse problem itself but not the algorithm; increasing the temperature of the heating surface is helpful to obtain a more accurate identification result; the number of temperature measurement points can be reduced, and the lateral boundary conditions have a negligible effect on the identification result of the inverse method.
THERMAL-MECHANICAL COUPLING PROPAGATION AND TRANSIENT THERMAL FRACTURE IN MULTILAYER COATINGS
935-954
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
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
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
Qibin
Li
Department of Engineering Mechanics, Chongqing University, Chongqing, 400044, P.R.China
A definite solution problem of a coupled thermal-mechanical model is considered for in-plane double-layer coatings, subjected to a heat pulse. The general solution of the governing coupled equations is obtained using the dual-phase lag model of the non-Fourier heat conduction law. The temperature increment T and volumetric strain θ are derived, which are related to the logarithmic heat rate ε. A thermal-mechanical failure analysis of the coating system is made and the possible failure mode is also investigated. The results show that the wave front propagates along the interface because of the reflection and superposition at the convex part of the interface. Transient stress intensity factors of mode I are obtained in the double-layer
system with cracks close to the interface. Moreover, the influences of different relaxation times and of the radius of the interface curvature are discussed.