Begell House Inc.
Heat Transfer Research
HTR
1064-2285
46
5
2015
A NEW METHOD TO DETERMINE THE THERMAL PROPERTIES OF SOIL FOR VERTICAL-BOREHOLE GROUND-SOURCE HEAT PUMP SYSTEMS
417-427
Xingjie
Dong
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, 800 Dongchuan Rd, Shanghai 200240, China
Bo
Gu
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, 800 Dongchuan Rd, Shanghai 200240, China
This paper presents a new method to determine the thermal properties of soil for a vertical-borehole ground-source heat pump. The method proposed is the result of combining the experimental and numerical study with the parameter estimation technique. The experimental study is an in situ thermal response test and the numerical study is the solution of the model of heat transfer inside/outside the borehole. The results show that the parameters including the soil thermal conductivity, borehole thermal resistance, and soil thermal diffusivity are accurately obtained and verified with the aid of experimental data. The method can accommodate well to the variable heat input conditions, and also it concludes that the models of heat transfer inside/outside the borehole are feasible to simulate the borehole heat transfer process.
PROPOSAL OF THE SHAPE LAYOUT OF TRAPEZOIDAL CAVITY RECEIVER TO IMPROVE THE OPTICAL EFFICIENCY
429-446
Fuqiang
Wang
Harbin Institute of Technology at Weihai, Harbin Institute of Technology, 2 West Wenhua Road,
Weihai 264209, P.R. China
Yong
Shuai
Key Laboratory of Aerospace Thermophysics of MIIT, School of Energy Science of Engineering, Harbin Institute of Technology, Harbin 150001, China
Heping
Tan
Key Laboratory of Aerospace Thermophysics of MIIT, School of Energy Science of Engineering, Harbin Institute of Technology, Harbin 150001, China
Liang
Gong
Department of Energy and Power Engineering, China University of Petroleum (East China), 66 West
Changjiang Rd. Huangdao District, Qingdao 266580, PR. China
The optical efficiency of conventional trapezoidal cavity receiver with different aperture radii is analyzed by the Monte Carlo ray tracing (MCRT) method. During fabrication, the bottom surface of the conventional cavity receiver cannot be fully covered by a coiled copper tube which would induce a dead space of solar energy absorption. A proposal for a shape layout of the trapezoidal cavity receiver, i.e., an inverted trapezoidal receiver with a bottom surface interior convex (ITBSIC receiver) is put forward with the objective of solving the problem of dead space absorption and improving the optical efficiency of the conventional trapezoidal cavity receiver. The effects of the interior convex dimensionless height, wall absorptivity, alignment error, and the pointing error on variation of the optical efficiency are analyzed.
ANALYTICAL SOLUTION OF THE PROBLEM OF NON-FOURIER HEAT CONDUCTION IN A SLAB USING THE SOLUTION STRUCTURE THEOREMS
447-464
Mohammad
Akbari
Department of Mechanical Engineering, Semnan University, Semnan, Iran
Seyfolah
Saedodin
Department of Mechanical Engineering, Semnan University, Semnan, Iran
Davood Semiromi
Toghraie
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University,
Khomeinishahr, Iran
Farshad
Kowsary
Department of Mechanical Engineering, University College of Engineering, University of Tehran, Tehran 515-14395, Iran
This paper studies an analytical method which combines the superposition technique along with the solution structure theorem such that a closed-form solution of the hyperbolic heat conduction equation can be obtained by using the fundamental mathematics. In this paper, the non-Fourier heat conduction in a slab at whose a left boundary there is a constant heat flux and at the right boundary, a constant temperature Ts = 15, has been investigated. The complicated problem is split into multiple simpler problems that in turn can be combined to obtain a solution to the original problem. The original problem is divided into five subproblems by setting the heat generation term, the initial conditions, and the boundary conditions for different values in each subproblem. All the solutions given in this paper can be easily proven by substituting them into the governing equation. The results show that the temperature will start retreating at approximately t = 2 and for t = 2 the temperature at the left boundary decreases leading to a decrease in the temperature in the domain. Also, the shape of the profiles remains nearly the same after t = 4. The solution presented in this study can be used as benchmark problems for validation of future numerical methods.
MIXED CONVECTION FLUID FLOW AND HEAT TRANSFER OF THE Al2O3−WATER NANOFLUID WITH VARIABLE PROPERTIES IN A CAVITY WITH AN INSIDE QUADRILATERAL OBSTACLE
465-482
Mohammad
Hemmat Esfe
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
Amir Hossein
Refahi
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
Hamid
Teimouri
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
Mohammaj javad
Noroozi
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
Masoud
Afrand
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.
Arash
Karimipour
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
This investigation is focused on mixed convection fluid flow and heat transfer of Al2O3−water inside a square enclosure containing a hot rectangular obstacle at its bottom wall. The governing equations have been solved using the finite volume method. The SIMPLER algorithm was employed to couple the velocity and pressure fields. Utilizing the developed code, a parametric study was conducted and the impact of important parameters such as the solid volume fraction, Richardson number, size of the hot obstacle on the fluid flow and thermal fields and heat transfer inside the enclosure were investigated. The results show that for all Richardson numbers, the average Nusselt number increases with increase in the volume fraction of nanoparticles. Moreover, at all values of the Richardson number, heat transfer decreases when the height of the heated obstacle increases.
EMPIRICAL CORRELATIONS FOR SIZING ADIABATIC CAPILLARY TUBES USING CONVENTIONAL REFRIGERANTS AND THEIR ALTERNATIVES
483-501
Shodiya
Sulaimon
Automotive Development Centre (ADC), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), Skudai, Johor, Malaysia;Department of Mechanical Engineering, Faculty of Engineering, University of Maiduguri (UNIMAID), Maiduguri, Borno, Nigeria
Azhar Abdul
Aziz
Automotive Development Centre (ADC), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), Skudai, Johor, Malaysia
Henry
Nasution
Automotive Development Centre (ADC), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor,
Malaysia
Amer Nordin
Darus
Automotive Development Centre (ADC), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), Skudai, Johor, Malaysia
This paper presents new empirical correlations developed by using conventional and alternative refrigerants for determining the size of adiabatic capillary tubes used in small vapor compression refrigeration systems. A homogenous two-phase flow model based on the principal equations of conservation of mass, momentum, and energy has been developed. Colebrook's and Churchill's formulations were used to determine the single-phase friction factor. Also, the two-phase viscosity models of Cicchitti et al. (I960), Dukler et al. (1964), McAdam et al. (1942), and Lin et al. (1991) were used to determine the two-phase viscosity factor. The developed numerical model that takes account of a metastable process to enhance the model was validated by using experimental data from the literature with an average error of 1.75%. This developed model that had not been employed previously by researchers was used to study the effects of relevant parameters on the capillary tube length. From these effects, empirical correlations of the capillary tube length with these dependent variables have been developed. Comparing the empirical models with experimental data from the literature showed a reasonable agreement with an average error of 3.45%. Though the empirical model developed in this study covers a large set of refrigerants, it should be used with caution by considering the range of operating conditions covered.