Research Article
The Increasing of the Heat Transfer Coefficient of Short Linear Heat Pipes
Seryakov Arkady Vladimirovich
Issue:
Volume 12, Issue 3, May 2023
Pages:
30-46
Received:
3 October 2023
Accepted:
24 October 2023
Published:
17 November 2023
Abstract: The results of the experimental studies of heat transfer coefficients KHP of short linear heat pipes (HP’s) with a Laval nozzle-liked vapour channel, and with a partially swirled vapour flow inside the channel are presented. A partial azimuthal swirling of the jet vapour stream is created using inclined injection channels 1 mm in diameter in a flat multilayer mech evaporator, with an inclination angle φ relative to the longitudinal axis in the azimuthal direction, in the range of 0° < φ < 60°. The heat transfer coefficients KHP of a set of the identical HP’s with a different inclination angles φ of the injection channels in the evaporators, with the same working fluid mass filling (δm/m ≤ 0.1 %), at the same evaporator temperature heat load δT = Tev –TB = (20 ± 0.03) K, represent an extreme convex function, depending on the inclination angle φ magnitude of the injection channels, with a maximum at the swirled angle of the vapour flow φ = 26° ± 2°. The magnitude of the excess of the KHP with a swirling vapour flow over the identical HP’s with a direct vapour flow reaches 10%. An analysis of the recommended vapour channel shape, carried out by the estimating of the Richardson number Ri of the vapour flow jets above the evaporator, allowed us to estimate the value of the dimensionless longitudinal radius of curvature δ/Rconf of the confuser part of the vapour channel, which is determined from the condition of minimal friction losses during the flow of moist vapour in the boundary layer δ along the concave wall of the confuser part of the vapour channel with a longitudinal radius of curvature Rconf. The concave diffuser part shape of the vapour channel is determined by the condition that the moving vapour jets velocity vectors must be parallel to the longitudinal axis of the diffuser part of the HP’s vapour channel. The results of the numerical simulation of the hydraulic resistance coefficients ξvp of the HP’s vapour channel, closed with flat covers, with partially swirling jet vapour flow, obtained by using the ANSYS FLUENT program, show a decrease in ξvp coefficients at high values of the evaporator temperature load, in the range of vapour flow velocities 1 m/s < uz ≤ 100 m /s, and in the range of swirling angles 0°<φ<30°. With the increasing the swirling angles φ>30°, a sharp increase in the hydraulic resistance coefficient ξvp begins.
Abstract: The results of the experimental studies of heat transfer coefficients KHP of short linear heat pipes (HP’s) with a Laval nozzle-liked vapour channel, and with a partially swirled vapour flow inside the channel are presented. A partial azimuthal swirling of the jet vapour stream is created using inclined injection channels 1 mm in diameter in a flat...
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Research Article
Annular Axisymmetric Stagnation Flow of a Casson Fluid Through Porous Media in a Moving Cylinder
Muhammad Umar Farooq*,
Abdul Rehman,
Naveed Sheikh
Issue:
Volume 12, Issue 3, May 2023
Pages:
47-53
Received:
14 November 2023
Accepted:
4 December 2023
Published:
14 December 2023
Abstract: The present investigation deals with the study of annular axisymmetric stagnation flow and heat transfer of a Casson fluid through porous medium in a moving cylinder. The inner cylinder is rotating with a fixed angular velocity and is also translating along axial axis with constant axial velocity while the outer cylinder is assumed fixed. Fluid is injected from the top surface of the fixed outer cylinder towards the translating and rotating inner cylinder. The motion of the Casson fluid is assumed under the influence of some porous media. The governing nonlinear partial differential equations of conservation of mass, conservation of li near momentum and heat transfer are obtained and then simplified with the help of a set of suitable similarity transformations which reduces the original set of partial differential equations into a new simplified set of ordinary differential equations. The resulting system of ordinary differential equations is then solved numerically with the aid of fifth order Runge-Kutta Fehlberg method. A comparison of special cases of the present numerical solution with the already available work is also included through tables. The behavior of important involved physical non-dimensional parameters like Prandtl numbers, porosity parameter and Reynolds numbers is also presented at the end.
Abstract: The present investigation deals with the study of annular axisymmetric stagnation flow and heat transfer of a Casson fluid through porous medium in a moving cylinder. The inner cylinder is rotating with a fixed angular velocity and is also translating along axial axis with constant axial velocity while the outer cylinder is assumed fixed. Fluid is ...
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