scholarly journals Thermal Analysis on Pin-Fins With Hexagonal & Threaded Geometry In Natural and Forced Convection

2020 ◽  
pp. 16-27
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Natural Convection ◽  
Temperature Distribution ◽  
Forced Convection ◽  
Transfer Rate ◽  
Airflow Rate ◽  
Test Panel ◽  
Centrifugal Blower ◽  
Pin Fins

In the present work of heat transfer for hexagonal fins (1mm & 2mm) grooves on surface and threaded fin is addressed. The test has been performed on three different fin geometries having hexagonal (1mm)groove, hexagonal(2mm)groove, threaded fin(0.5mm)pitch and test performed by using a centrifugal blower, test section, heater and test panel and Results are obtained for temperature distribution, effectiveness, efficiencies at a same flow rate of air as it was conducted in forced convection and the same parameters considered for different values are obtained for natural convection with different fins as well. In this experiment for forced convection, the airflow rate is constant i.e, 2.3371 m/sec throughout the experiment. In natural convection, efficiency for the threaded fin is high with 93.89% and effectiveness of hexagonal(2mm)depth fin is 28.11. In forced convection, the efficiency of the threaded fin is high with 81.83% and effectiveness of hexagonal(1mm)depth fin is high with 23.51 was recorded. The heat transfer rate is higher in natural convection is hexagonal(2mm)depth fin with 11.41 watts and 21.75 watts in forced convection with hexagonal(1mm)depth fin

scholarly journals Experimental Study for Counter to Cross Flow Air Cooled Heat Exchanger in Concentric Tube using Rectangular Copper Fins Spacing with Internal Spiral Grooving

2021 ◽  
pp. 203-208
Author(s):  
Rakesh Kumar Tiwari ◽  
Ajay Singh ◽  
Parag Mishra
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cross Flow ◽  
Variable Number ◽  
Air Cooled Heat Exchanger

In this manuscript we have presented eight variation of Air-Cooled Heat Exchanger (ACHE) design with internal spiral grooving, all of them are having variable number of rectangular copper fins with different distances between the fins. In the proposed design we get the value of heat transfer rate of a counter to cross flow ACHE is 7833.77 watt, 4068.13 watt, 2736.95 watt, 2161.49 watt, 1802.89 watt, 1546.44 watt, 1336.51 watt and 1165.74 watt in natural convection (without fan) for 0.5 cm, 1.0 cm, 1.5 cm, 2.0 cm, 2.5 cm, 3.0 cm, 3.5 cm and 4.0 cm respectively. Then again, value of rate of heat transfer in forced convection (with fan) are 8007.46 watt, 4084.81 watt, 2754.69 watt, 2205.98 watt, 1809.24 watt, 1555.39 watt, 1352.88 watt and 1172.78 watt for 0.5 cm, 1.0 cm, 1.5cm, 2.0 cm, 2.5 cm, 3.0 cm, 3.5 cm and 4.0 cm respectively.

Thermal Analysis and Optimization of Orthotropic Pin Fins: A Closed-Form Analytical Solution

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
Syed M. Zubair ◽  
A. F. M. Arif ◽  
Mostafa H. Sharqawy
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Temperature Distribution ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Two Dimensional ◽  
Fin Efficiency ◽  
Pin Fin ◽  
Special Cases ◽  
Pin Fins

Analytical solutions for temperature distribution, heat transfer rate, and fin efficiency and fin effectiveness are derived and presented for orthotropic two-dimensional pin fins subject to convective-tip boundary condition. The generalized results are presented and discussed in terms of dimensionless variables such as radial and axial Biot numbers (Bir,Biz), fin aspect ratio, L/R, and radial-to-axial conductivity ratio k∗. Several special cases are derived from the general solution, which includes the insulated-tip boundary condition. It is also demonstrated that the classical temperature distribution and heat transfer rate from the two-dimensional isotropic pin fin introduced earlier in literature can easily be recovered from the general solutions presented in this paper. Furthermore, dimensionless optimization results are presented for orthotropic pin fins that can help to solve many natural and forced convection pin fin problems.

Mixed Convection Transport From an Isolated Heat Source Module on a Horizontal Plate

1990 ◽  
Vol 112 (3) ◽  
pp. 653-661 ◽  
Author(s):  
B. H. Kang ◽  
Y. Jaluria ◽  
S. S. Tewari
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Mixed Convection ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Finite Thickness ◽  
Forced Flow ◽  
Maximum Temperature ◽  
Convection Dominated

An experimental study of the mixed convective heat transfer from an isolated source of finite thickness, located on a horizontal surface in an externally induced forced flow, has been carried out. This problem is of particular interest in the cooling of electronic components and also in the thermal transport associated with various manufacturing systems, such as ovens and furnaces. The temperature distribution in the flow as well as the surface temperature variation are studied in detail. The dependence of the heat transfer rate on the mixed convection parameter and on the thickness of the heated element or source, particularly in the vicinity of the source, is investigated. The results obtained indicate that the heat transfer rate and fluid flow characteristics vary strongly with the mixed convection variables. The transition from a natural convection dominated flow to a forced convection dominated flow is studied experimentally and the basic characteristics of the two regimes determined. This transition has a strong influence on the temperature of the surface and on the heat transfer rate. As expected, the forced convection dominated flow is seen to be significantly more effective in the cooling of a heat dissipating component than a natural convection dominated flow. The location of the maximum temperature on the module surface, which corresponds to the minimum local heat transfer coefficient, is determined and discussed in terms of the underlying physical mechanisms. The results obtained are also compared with these for an element of negligible thickness and the effect of a significant module thickness on the transport is determined. Several other important aspects of fundamental and applied interest are studied in this investigation.

Design of a Plane-Type Bidirectional Thermal Diode

1988 ◽  
Vol 110 (4) ◽  
pp. 299-305 ◽  
Author(s):  
K. Chen
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Transfer Rate ◽  
Reverse Bias ◽  
Energy Utilization ◽  
Heat Transfer Analysis ◽  
Transfer Rates ◽  
One Dimensional ◽  
Plane Type ◽  
Solar Energy Utilization

The design of a plane-type, bidirectional thermal diode is presented. This diode is composed of two vertical plates and several fluid-filled loops with their horizontal segments soldered to the vertical plates. This invention is simple in construction and low in cost. The direction of heat transfer in the invented thermal diode can be easily reversed. These features of the present invention make it very attractive to solar energy utilization. Natural convection analysis for thermosyphon operations was adopted for heat transfer calculations of the fluid-filled loops. A one-dimensional heat transfer analysis was employed to estimate the heat transfer rate and ratio of heat transfer rates of the diode under forward and reverse bias.

scholarly journals A RANS K-? SIMULATION OF 2D TURBULENT NATURAL CONVECTION IN AN ENCLOSURE WITH HEATING SOURCES

2019 ◽  
Vol 20 (1) ◽  
pp. 229-244
Author(s):  
Mehdi Ahmadi ◽  
Seyed Ali Agha Mirjalily ◽  
Seyed Amir Abbas Oloomi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Kinetic Energy ◽  
Aspect Ratio ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Turbulent Natural Convection ◽  
Cold Source ◽  
Thermal Sources

ABSTRACT: This study is conducted to investigate turbulent natural convection flow in an enclosure with thermal sources using the low-Reynolds number (LRN) k-? model. This enclosure has a cold source with temperature Tc and a hot source with temperature Th as thermal sources, other walls of the enclosure are adiabatic. The aim of this study is to predict the effect of change in Rayleigh number, repositioning of cold and hot sources, and thermal sources aspect ratio on the flow field, temperature, and rate of heat transfer. To achieve this aim, the equations of continuity, momentum, energy, turbulent kinetic energy, and kinetic energy dissipation are employed in the case of 2D turbulence with constant thermo-physical properties except the density in the buoyancy term (Boussinesq approximation). To numerically solve these equations, the finite volume method and SIMPLE algorithm are used. According to the modeling results, the most optimal temperature distribution in the enclosure is seen when the hot source is below the cold source. With decreasing distance between hot and cold sources, heat transfer rate increases. The maximal heat transfer rate is derived via study of the heating sources aspect ratio. In constant positions of cold and hot sources on a wall, the heat transfer rate increases with increasing Rayleigh number (Ra=109-1011). ABSTAK: Kajian ini dijalankan bagi mengkaji perubahan semula jadi aliran perolakan dalam tempat tertutup dengan sumber haba menggunakan model k-? nombor Reynolds-rendah (LRN). Bekas tertutup ini mempunyai dua sumber haba iaitu sumber sejuk dengan suhu Tc dan sumber panas dengan suhu Th, manakala dinding lain bekas ini adalah adiabatik. Tujuan kajian ini adalah bagi mengesan perubahan nombor Rayleigh, mengubah sumber sejuk dan panas dan nisbah sumber haba kepada kawasan aliran, suhu dan halaju perubahan haba. Bagi mencapai tujuan tersebut, persamaan sambungan, momentum, tenaga, tenaga kinetik perolakan, dan pengurangan tenaga kinetik telah dilaksanakan dalam kes perolakan 2D dengan sifat fizikal-haba berterusan (malar) kecuali isipadu terma keapungan (anggaran Boussinesq). Bagi menyelesaikan persamaan ini secara berangka, kaedah isipadu terhad dan algorithma MUDAH telah digunakan. Berdasarkan keputusan model, suhu distribusi optimal dalam bekas tertutup dilihat apabila sumber panas adalah kurang daripada sumber sejuk. Dengan pengurangan jarak antara sumber panas dan sejuk, kadar pertukaran haba meningkat. Kadar pertukaran haba maksima telah diperoleh melalui kajian nisbah  aspek sumber pemanasan. Kadar pertukaran haba bertambah dengan bertambahnya nombor Rayleigh  (Ra=109-1011), pada posisi tetap sumber sejuk dan panas pada dinding bekas.

scholarly journals Improving the Heat Transfer Rate of Air Conditioning Condenser by Material Optimization

2021 ◽  
pp. 39-50
Author(s):  
A. A. Adegbola ◽  
O. A. Adeaga ◽  
A. O. Babalola ◽  
A. O. Oladejo ◽  
A. S. Alabi
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Heat Flux ◽  
Flow Rate ◽  
Transfer Rate ◽  
Air Conditioning ◽  
Static Pressure ◽  
Cfd Analysis ◽  
Condenser Tube ◽  
Total Heat Transfer

Air conditioning systems have condensers that remove unwanted heat from the refrigerant and transfer the heat outdoors. The optimization of the global exploit of heat exchanging devices is still a burdensome task due to different design parameters involved. There is need for more and substantial research into bettering cooling channel materials so as to ensure elevated performance, better efficiency, greater accuracy, long lasting and low cost heat exchanging. The aim of this research work is to improve the heat transfer rate of air conditioning condenser by optimizing materials for different tube diameters. Simulations using thermal analysis and Computational Fluid Dynamic (CFD) analysis were carried out to determine the better material and fluid respectively. The analysis was done using Analysis System software. Different parameters were calculated from the results obtained and graphs are plotted between various parameters such as heat flux, static pressure, velocity, mass flow rate and total heat transfer. The materials used for CFD analysis are R12 and R22, and for thermal analysis are copper and aluminium. From the CFD analysis, the result shows that R22 has more static pressure, velocity, mass flow rate and total heat transfer than R12 at condenser tube diameter 6 mm. In thermal investigation, the heat flux is more for copper material at condenser tube diameter 6 mm. Copper offers maximum heat flux. Also, refrigerant R22 scores maximum for the heat transfer criteria, but cannot be recommended due to toxicity

Natural Convection in an Anisotropic Porous Enclosure Due to Nonuniform Heating From the Bottom Wall

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Ashok Kumar ◽  
P. Bera
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Principal Direction ◽  
Orientation Angle ◽  
Bottom Wall ◽  
Nonuniform Heating ◽  
Material Derivative ◽  
Porous Enclosure

A comprehensive numerical investigation on the natural convection in a hydrodynamically anisotropic porous enclosure is presented. The flow is due to nonuniformly heated bottom wall and maintenance of constant temperature at cold vertical walls along with adiabatic top wall. Brinkman-extended non-Darcy model, including material derivative, is considered. The principal direction of the permeability tensor has been taken oblique to the gravity vector. The spectral element method has been adopted to solve numerically the governing conservative equations of mass, momentum, and energy by using a stream-function vorticity formulation. Special attention is given to understand the effect of anisotropic parameters on the heat transfer rate as well as flow configurations. The numerical experiments show that in the case of isotropic porous enclosure, the maximum rates of bottom as well as side heat transfers (Nub and Nus) take place at the aspect ratio, A, of the enclosure equal to 1, which is, in general, not true in the case of anisotropic porous enclosures. The flow in the enclosure is governed by two different types of convective cells: rotating (i) clockwise and (ii) anticlockwise. Based on the value of media permeability as well as orientation angle, in the anisotropic case, one of the cells will dominate the other. In contrast to isotropic porous media, enhancement of flow convection in the anisotropic porous enclosure does not mean increasing the side heat transfer rate always. Furthermore, the results show that anisotropy causes significant changes in the bottom as well as side average Nusselt numbers. In particular, the present analysis shows that permeability orientation angle has a significant effect on the flow dynamics and temperature profile and consequently on the heat transfer rates.

Effect of a Magnetic Field on the Heat Transfer Rate on Free Convection in a Rectangular Cavity

2005 ◽  
Author(s):  
Gustavo Gutierrez ◽  
Ezequiel Medici
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Stokes Equations ◽  
Rectangular Cavity ◽  
Convection Flow ◽  
Interesting Phenomenon ◽  
The Magnetic Field

The interaction between magnetic fields and convection is an interesting phenomenon because of its many important engineering applications. Due to natural convection motion the electric conductive fluid in a magnetic field experiences a Lorenz force and its effect is usually to reduce the flow velocities. A magnetic field can be used to control the flow field and increase or reduce the heat transfer rate. In this paper, the effect of a magnetic field in a natural convection flow of an electrically conducting fluid in a rectangular cavity is studied numerically. The two side walls of the cavity are maintained at two different constant temperatures while the upper wall and the lower wall are completely insulated. The coupling of the Navier-Stokes equations with the Maxwell equations is discussed with the assumptions and main simplifications assumed in typical problems of magnetohydrodynamics. The nonlinear Lorenz force generates a rich variety of flow patterns depending on the values of the Grashof and Hartmann numbers. Numerical simulations are carried out for different Grashof and Hartmann numbers. The effect of the magnetic field on the Nusselt number is discussed as well as how convection can be suppressed for certain values of the Hartmann number under appropriate direction of the magnetic field.

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