Begell House Inc.
Heat Transfer Research
HTR
1064-2285
51
1
2020
EXPERIMENTAL AND NUMERICAL STUDY ON HEAT TRANSFER ENHANCEMENT OF HOME RADIATORS BY EMPLOYING SOLAR CELLS AND FANS
1-12
10.1615/HeatTransRes.2019029250
Faraz
Afshari
Erzurum Technical University, Department of Mechanical Engineering, 25240, Erzurum, Turkey
heat transfer enhancement
forced convection
solar energy
CFD
radiator
In the traditional heating systems, heated water in the boiler is circulated in the home radiators to warm up the ambient temperature as an air conditioning system. Generally, in the mentioned systems, the natural convection has a key role in the heat transfer from the radiator to the surroundings. The forced convection can be also applied by using air fans, and consequently the Nusselt number will be increased, which means an increase in the efficiency and heat transfer. In this work, the air fans were placed in a sample radiator to improve the thermal efficiency. The used fans are powered by batteries, and the battery supply is charged by solar cells. The fans will be able to operate at nights when the electric energy of the solar cells has been stored in the accumulator. The problem was simulated using the ANSYS Fluent software to compare the obtained numerical results to those recorded experimentally. In numerical and experimental results, an increase in heat transfer was observed. The obtained results showed that the average heat transfer rate was improved by about 21% by using forced convention.
APPLICATION OF TRIPLE DECOMPOSITION TECHNIQUE IN NEAR-WAKE MEASUREMENTS OF A SQUARE CYLINDER
13-23
10.1615/HeatTransRes.2019029585
Hamidreza
Shiri
Department of Mechanical Engineering, Eastern Mediterranean University, Northern Cyprus, Via
Mersin 10, Turkey
Hasan
Hacisevki
Aerodynamics Laboratory, Department of Mechanical Engineering, Eastern Mediterranean University, Northern Cyprus, Via Mersin 10, Turkey
vortex shedding
turbulent kinetic energy
triple decomposition
The flow properties and wake structures behind bluff bodies have fascinated researchers for many years. The Reynolds decomposition is a very common technique to approach these problems. However, some researchers tackle such problems with an alternative technique known as the triple decomposition. Since the flow structure of a bluff body comprises large-scale organized motion, the time-varying component in the wake region of a bluff-body flow consists of a periodic component (coherent structure) that can be distinguished from a random (incoherent) component. In the present study, incoherent turbulent flow structures in the near-wake region downstream of a square cylinder have been studied by employing triple decomposition. It was observed that the main incoherent turbulent kinetic energy production occurs in the region with the same width of square cylinder. Moreover, it was demonstrated that while a vortex is developing from one edge with maximum incoherent streamwise stress, the initiated shear layers from the other edge exhibit a maximum in incoherent transverse stress production.
HEAT TRANSFER AND FLUID FLOW IN A WATER-FILLED GLASS LOUVER SUBJECT TO SOLAR IRRADIATION
25-39
10.1615/HeatTransRes.2019031074
Yi
Nan
Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New
Jersey, Piscataway, NJ 08854, USA
Yaomin
Cai
Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New
Jersey, Piscataway, NJ 08854, USA
Zhixiong
Guo
Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New
Jersey, Piscataway, NJ 08854, USA
solar energy
energy harvest
conjugate heat transfer
fluid flow
illumination
glass louver
Numerical studies of fluid flow and heat transfer in a water-filled prismatic glass louver have been carried out to investigate the efficiency of solar thermal energy harvest via the proposed louver that could be deployed in buildings to improve natural lighting to save electrical bills as well as to harvest and store solar energy transformed into thermal energy. One surface of the prismatic louver is adjusted to face the direct solar irradiation. Both direct and diffuse irradiations are incorporated in different air mass models. The distribution of absorbed solar radiation in the louver is precalculated via the Monte Carlo method and input as a heating source. The finite element method based on COMSOL is adopted to simulate the three-dimensional steady-state fluid flow and conjugate heat transfer in the triangular water channel. Temperature-dependence of water property is considered. The prismatic louver is surrounded by ambient air. Emphasis is placed on investigating the effects of flow rate and solar irradiation conditions on water temperature rise and energy harvest. It is found that the outlet water temperature is a strong function of the water flow rate. Most of the absorbed solar energy in the glass can be converted into stored thermal energy in the water through convective heat transfer. The water pumping power consumed is negligible as compared to the energy harvested. When the louver is adjusted to face the direct solar irradiation and the water flow velocity is 0.1 m/s, the overall utilization efficiency of the louver reaches 89.2, 90.3, 89.1, and 87.9% for AM1.0, AM1.5, AM2.0, and AM3.0, respectively.
EFFECTS OF COOLING TUBES ON CONJUGATE HEAT AND MASS TRANSFER IN A HEXAGONAL PARALLEL-PLATE MEMBRANE CHANNEL
41-56
10.1615/HeatTransRes.2019029768
Si-Min
Huang
Key Laboratory of Distributed Energy Systems of Guangdong Province, Department of Energy
and Chemical Engineering, Dongguan University of Technology, Dongguan 523808, People's
Republic of China
Dai-Wei
Du
Guangdong Provincal Key Laboratory of Distributed Energy Systems, Dongguan University of
Technology, Dongguan 523808, China
Liehui
Xiao
Guangdong Provincal Key Laboratory of Distributed Energy Systems, Dongguan University of
Technology, Dongguan 523808, China
Wu-Zhi
Yuan
Guangdong Provincal Key Laboratory of Distributed Energy Systems, Dongguan University of
Technology, Dongguan 523808, China
Bing
Hu
Guangdong Provincal Key Laboratory of Distributed Energy Systems, Dongguan University of
Technology, Dongguan 523808, China
Shimin
Kang
Guangdong Provincal Key Laboratory of Distributed Energy Systems, Dongguan University of
Technology, Dongguan 523808, China
conjugate heat and mass transfer
internally cooled types
hexagonal parallel-plate membrane
cooling tubes
liquid desiccant air dehumidification
An internally cooled hexagonal parallel-plate membrane contactor is developed and used to study the conjugate heat and mass transfer under the effects of cooling tubes. The contactor is comprised of a series of internally cooled hexagonal parallel-plate membrane channels (IHPMC). A mathematical model is established in a unit cell including a hexagonal plate membrane, an adjacent air channel and a solution (liquid desiccant) channel with several cooling tubes. The air and the solution streams are in an arrangement combined with counterflow and crossflow. The cooling tubes are installed in the solution side, while the water flows in the counterflow arrangement to take away the sensible heat of the solution generated by absorbing the water vapor. The partial differential equations for describing the fluid flow and heat and mass transfer are established and numerically solved. The friction factors, Nusselt numbers, and Sherwood numbers are then obtained and analyzed. Influences of the tube number Ntube, tube outer diameters douter, and Reynolds numbers Re on the IHPMC under the conjugate heat and mass transfer boundary conditions are investigated. It can be found that the tube numbers and the tube outer diameters have negligible influences on the mean Nusselt numbers and the Sherwood numbers for the air stream, while their effects on the solution are large. The friction factors and the Nusselt numbers for the water stream are nearly independent of the various tubes inside the solution channels.
GEOMETRIC-PARAMETER INFLUENCES ON AND ORTHOGONAL EVALUATION OF THERMOMECHANICAL PERFORMANCES OF A LAMINATED COOLING STRUCTURE
57-82
10.1615/HeatTransRes.2019030676
Chen
Wang
College of Energy and Power Engineering, Jiangsu Province Key Laboratory of Aerospace Power
System, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
Jing-Zhou
Zhang
College of Energy and Power Engineering, Jiangsu Province Key Laboratory of Aerospace Power
System, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China; Collaborative Innovation Center of Advanced Aero-Engine, Beĳ ing, 100191, China
Chun-hua
Wang
College of Energy and Power Engineering, Jiangsu Province Key Laboratory of Aerospace Power System, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Jun
Ji
College of Energy and Power Engineering, Jiangsu Province Key Laboratory of Aerospace Power
System, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
Xiao-Ming
Tan
College of Energy and Power Engineering, Jiangsu Province Key Laboratory of Aerospace Power
System, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China
laminated cooling structure
geometric-parameter influence
orthogonal evaluation
thermomechanical performance
comprehensive performance index
Numerical simulations are conducted to illustrate the geometric-parameter influences on and orthogonal evaluation of thermomechanical performances of a specific laminated cooling structure, under the representative engine-simulated environment. Five geometric parameters taken into consideration are the film-hole diameter, impinging-hole diameter, pin-fin diameter, streamwise hole-to-hole pitch, and the spanwise hole-to-hole pitch. Firstly, each geometric-parameter influence is investigated individually among its varying range while maintaining the other geometric parameters. Secondly, an orthogonal analysis (5-factors and 4-levels for each factor) is performed for evaluating the importance of each geometric-parameter on the thermomechanical performances of a laminated cooling structure, in the viewing of comprehensive performance index which is constructed by applying a weighted sum method, taking the overall cooling effectiveness, cooling air pressure drop, maximum thermal stress, and maximum thermal deformation into consideration. From the orthogonal analysis, a relatively optimum combination of the above geometric parameters is presented.
THERMODYNAMIC ANALYSIS OF HALL CURRENT AND SORET NUMBER EFFECT ON HYDROMAGNETIC COUETTE FLOW IN A ROTATING SYSTEM WITH A CONVECTIVE BOUNDARY CONDITION
83-102
10.1615/HeatTransRes.2019027139
Malapati
Venkateswarlu
Department of Mathematics, V.R. Siddhartha Engineering College, Krishna (Dist), A.P., India
D. V.
Lakshmi
Department of Mathematics, V.R. Siddhartha Engineering College, Krishna (Dist), A.P., India
Oluwole Daniel
Makinde
Faculty of Military Science, Stellenbosch University, Private Bag X2, Saldanha 7395, South
Africa
Hall current
Soret number
heat absorption
Couette flow
rotation
The present article considers the effect of the fascinating and novel characteristics of Hall current and Soret number on hydromagnetic Couette flow in a rotating system with a convective boundary condition. Exact solutions for the fluid velocity, temperature, and species concentration, under Boussinesq approximation, are obtained in closed form by using the two-term perturbation technique. The interesting parts of thermal dispersing outcomes are taken into account. Graphical evaluation appears to depict the trademark direct of introduced parameters on non-dimensional velocity, temperature, and concentration profiles. Also, the numerical assortment for skin friction coefficient, Nusselt number, and Sherwood number is examined through tables. In particular, primary velocity decreases and secondary velocity increases with an increase in the magnetic parameter.