Begell House Inc.
Heat Transfer Research
HTR
1064-2285
48
15
2017
THERMAL CHARACTERISTICS OF AN ANNULAR WICKLESS HEAT PIPE
1339-1357
Guodong
Xia
Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China
Wei
Wang
Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education,
College of Environmental and Energy Engineering, Beĳing University of Technology,
Beĳing 100124, China
Yonggang
Jiao
Department of Energy and Environmental Engineering, Shĳiazhuang Tiedao University,
Shĳiazhuang 050043, China
Dandan
Ma
Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education,
College of Environmental and Energy Engineering, Beĳing University of Technology,
Beĳing 100124, China
An experimental study was carried out to investigate the thermal characteristics of an eccentric annular wickless heat pipe (EAWHP) with deionized water as a working fluid. The eccentric annular wickless heat pipe was sealed by a high vacuum valve which is capable of changing the filling ratio. The experiments were performed in the range of 343.15–373.15 K operating temperature and 15–60% filling ratio under natural convection and forced convection. The temperature stability, uniformity, and distribution of the evaporator wall outer surface and the condenser wall inner surface of the eccentric annular wickless heat pipe are affected by various factors, such as the filling ratio, the mounting location of the heater controller sensor, and the cooling ability of the condenser section. The results show that the larger filling ratio, lower operating temperature, and the upper temperature control point have been found to be very helpful for optimizing the temperature stability and uniformity in the condenser wall inner surface under our experimental conditions. The temperature stability of the central of condenser wall inner surface can reach 0.048 K for 2 h, while the accuracy of the device for controlling
temperature lies within ±2.0 K. The condenser wall inner surface temperature uniformity can be reached at 0.142 K, while that of the evaporator wall outer surface is 2.676 K. Analysis of the evaporator wall outer surface temperature distributions using a method of thermal resistance network is also presented. The ability to maintain constant evaporator temperature makes the eccentric annular wickless heat pipes effective devices for use in temperature calibration field.
THEORETICAL ANALYSIS OF SODIUM VAPOR CONDENSATION ON A PLATE IMBEDDED IN A POROUS MEDIUM UNDER ZERO GRAVITY CONDITION
1359-1378
Lan
Xiao
Key Laboratory of Low-grade Energy
Utilization Technologies and Systems, Ministry of Education, Chongqing
University, Chongqing 400044, China; College of Power Engineering,
Chongqing University, Chongqing 400044, China
Shuang-Ying
Wu
Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry
of Education, Chongqing University, Chongqing 400044, China; College of Power Engineering, Chongqing University, Chongqing 400044, China
Yang
Shang
College of Power Engineering, Chongqing University, Chongqing 400044, China
A theoretical model considering the capillary force rather than the gravitational force is established to study sodium vapor condensation heat transfer on a plate imbedded in a porous medium under zero gravity condition. The impacts of different parameters, including structural and operational ones, are discussed in detail. The results show that no matter what is the layer − thick porous (δ < H) or thin porous (δ > H) − the condensate film thickness δ decreases with the increasing permeability K and radiation source temperature Tr, while it increases with the increasing effective thermal conductivity λe, sodium vapor saturation temperature Ts, and the temperature difference ΔT. The variation trends of the local Nusselt number Nux and condensate film thickness δ versus related parameters, except for the porous medium layer thickness H, are contrary, since Nux tends to vary inversely with δ. Specially, for the case of δ > H, both Nux and δ increase with increasing H, which is different from the condensation of water vapor. Compared with no radiation heat transfer, the presence of radiation heat transfer makes the condensate film thickness δ reduced and the local Nusselt number Nux increased somewhat.
RADIATIVE HEAT TRANSFER IN COMPLEX ENCLOSURES USING NVD DIFFERENCING SCHEMES OF THE FTn FINITE VOLUME METHOD
1379-1398
Kamel
Guedri
Mechanical Engineering Department, College of Engineering and Islamic Architecture,
Umm Al-Qura University, B. Po 5555, Makkah, 21955, Saudi Arabia; Unité de Recherche Matériaux, Energie et Energies Renouvelables, Faculty of Sciences of Gafsa,
University of Gafsa, Tunisia
Abdulmajeed Saeed
Al-Ghamdi
Mechanical Engineering Department, College of Engineering, Umm Al-Qura University, Makkah, Saudi Arabia
In the present work, nine high-order resolution schemes based on the Normalized Variable Diagram (NVD) formulation,
such as MINMOD, GAMMA, CLAM, NOTABLE, MUSCL, CUBISTA, SMART, WACEB, and VANOS schemes, are applied to the FTn FVM, a nonuniform angular discretization, for solving the radiative transfer equation in 2D and 3D regular and irregular enclosures containing transparent, emitting-absorbing, emitting-absorbing-scattering, and nonhomogeneous
media. To treat irregular boundaries, the blocked-off-region procedure is implemented. By comparing with analytical or numerical reference solutions, it should be pointed out that although all NVD schemes are much more accurate than the STEP scheme, they consume more time and require more iterations. Moreover, most of them often necessitate underrelaxation to ensure convergence. The MINMOD and GAMMA schemes are still much less accurate than other NVD schemes, but they converge most quickly of the NVD schemes, and do not require underrelaxation. Although the VANOS scheme gives more accurate solutions, it is not competitive with other NVD schemes.
HYPERBOLIC HEAT CONDUCTION ANALYSIS FOR AN ORTHOTROPIC FG HOLLOW SPHERE WITH INTERNAL HEAT SOURCE. APPLICATION OF A NEW AUGMENTED STATE SPACE METHOD
1399-1419
Majid
Bakhtiari
Department of Mechanical Engineering, Iran University of Science and Technology, Narmak,
Tehran 16844, Iran
Kamran
Daneshjou
Department of Mechanical Engineering, Iran University of Science and Technology, Narmak,
Tehran 16844, Iran
Hossein
Parsania
Department of Mechanical Engineering, Iran University of Science and Technology, Narmak,
Tehran 16844, Iran
M.
Fakoor
Department of Aerospace Engineering, Faculty of New Sciences and Technologies, University
of Tehran, Tehran 4399-55941, Iran
In the present study, a new mathematical model, named an augmented state space method, is introduced to solve the governing differential equations of non-Fourier problem including a heat source and arbitrary boundary conditions in spherical coordinates. Hyperbolic heat conduction in an inhomogeneous orthotropic hollow sphere subjected to time-dependent heat source and heat flux are investigated. The new augmented state-space method is based on laminate approximation theory in the Laplace domain. In order to convert the obtained results into the time domain, numerical Laplace transformation inversion with consideration of the Gibbs phenomenon has been employed. The transient responses of temperature are investigated for different inhomogeneity parameters and different indices of orthotropic FG hollow spheres.
A TEMPERATURE ERROR CORRECTION METHOD FOR A DTR503A NATURALLY VENTILATED RADIATION SHIELD
1421-1432
Jie
Yang
Jiangsu Collaborative Innovation Center on Atmospheric Environment and Equipment Technology, Nanjing 210044, China; Jiangsu Key Laboratory of Meteorological Observation and Information Processing, Nanjing 210044, China
Qingquan
Liu
Jiangsu Collaborative Innovation Center on Atmospheric Environment and Equipment Technology, Nanjing 210044, China; Jiangsu Key Laboratory of Meteorological Observation and Information Processing, Nanjing 210044, China
Wei
Dai
Key Laboratory of MEMS of the Ministry of Education, Nanjing 210009, China
Due to solar radiation exposure, air flowing inside a naturally ventilated radiation shield may produce a measurement error of 0.8°C or higher. To improve the air temperature observation accuracy, a temperature error correction method is proposed. The correction method is based on a computational fluid dynamics (CFD) method and a genetic algorithm (GA) method. The CFD method is implemented to obtain the temperature error of a DTR503A naturally ventilated radiation shield under various environmental conditions. Then, a temperature error correction equation is obtained by fitting the CFD results using the GA method. To verify the performance of the correction equation, the DTR503A naturally ventilated radiation shield and an aspirated temperature measurement platform are characterized in the same environment to allow intercomparison.
The aspirated temperature measurement platform serves as an air temperature reference. The mean temperature error
given by the intercomparison experiments is 0.66°C, and the mean temperature error given by the correction equation is 0.67°C. This correction equation allows the temperature error to be reduced by approximately 98.5%. The mean absolute error and the root mean square error between the temperature errors given by the correction equation and the temperature errors given by the experiments are 0.073°C and 0.079°C, respectively. The correction equation is only for the DTR503A naturally ventilated radiation shield, but the temperature error correction method can be used on a variety of shields.