Heat Transfer Analysis of Laminar Pulsating Flow in a Rectangular Channel Using Infrared Thermography

2021 ◽  
Author(s):  
Richard Blythman ◽  
Sajad Alimohammadi ◽  
Nicholas Jeffers ◽  
Darina B. Murray ◽  
Tim Persoons
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Analytical Solution ◽  
Local Time ◽  
Rectangular Channel ◽  
Pulsating Flow ◽  
Time Dependent ◽  
Heat Transfer Analysis ◽  
Flux Boundary Condition ◽  
Hydrodynamic Behaviour

Abstract While numerous applied studies have successfully demonstrated the feasibility of unsteady cooling solutions, a consensus has yet to be reached on the local instantaneous conditions that result in heat transfer enhancement. The current work aims to experimentally validate a recent analytical solution (on a local time-dependent basis) for the common flow condition of a fully-developed incompressible pulsating flow in a uniformly-heated vessel. The experimental setup is found to approximate the ideal constant heat flux boundary condition well, especially for the decoupled unsteady scenario where the amplitude of the most significant secondary contributions (capacitance and lateral conduction) amounts to 1.2% and 0.2% of the generated heat flux, respectively. Overall, the experimental measurements for temperature and heat flux oscillations are found to coincide well with a recent analytical solution to the energy equation by the authors. Furthermore, local time-dependent heat flux enhancements and degradations are observed to be qualitatively similar to those of wall shear stress from a previous study, suggesting that the thermal performance is indeed influenced by hydrodynamic behaviour.

Transient Internal Forced Convection Under Arbitrary Time-Dependent Heat Flux

2013 ◽  
Author(s):  
M. Fakoor-Pakdaman ◽  
M. Andisheh-Tadbir ◽  
Majid Bahrami
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Forced Convection ◽  
Analytical Model ◽  
Time Dependent ◽  
Bulk Temperature ◽  
Fluid Temperature ◽  
Flux Boundary Condition ◽  
Arbitrary Time

A new all-time model is developed to predict transient laminar forced convection heat transfer inside a circular tube under arbitrary time-dependent heat flux. Slug flow condition is assumed for the velocity profile inside the tube. The solution to the time-dependent energy equation for a step heat flux boundary condition is generalized for arbitrary time variations in surface heat flux using a Duhamel’s integral technique. A cyclic time-dependent heat flux is considered and new compact closed-form relationships are proposed to predict: i) fluid temperature distribution inside the tube ii) fluid bulk temperature and iii) the Nusselt number. A new definition, cyclic fully-developed Nusselt number, is introduced and it is shown that in the thermally fully-developed region the Nusselt number is not a function of axial location, but it varies with time and the angular frequency of the imposed heat flux. Optimum conditions are found which maximize the heat transfer rate of the unsteady laminar forced-convective tube flow. We also performed an independent numerical simulation using ANSYS to validate the present analytical model. The comparison between the numerical and the present analytical model shows great agreement; a maximum relative difference less than 5.3%.

scholarly journals Convection Heat Transfer Analysis in A Vertical Porous Tube

2020 ◽  
Vol 8 (1) ◽  
pp. 31-45
Author(s):  
Hikmat N. Abdulkareem ◽  
Kifah H. Hilal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convection Heat Transfer ◽  
Particle Diameter ◽  
Vertical Channel ◽  
Packed Bed ◽  
Constant Heat Flux ◽  
Heat Transfer Analysis ◽  
Constant Heat ◽  
Flux Boundary Condition

Forced convective heat transfer in a vertical channel symmetrically heated with a constant heat flux, and packed with saturated porous media, has been investigated experimentally in the present work. The channel was padded with spherical glass of three diameter (1, 3 and 10 mm) in a range 0.0416 < (particle diameter / inner channel radius) <0.416. The experimental setup, using a copper tube as a packed bed assembly with (48 mm) inside diameter and (1150 mm) heated length with a constant heat flux boundary condition. The test section was vertically oriented with water flowing against gravity and packed with glass spheres (1, 3 and 10 mm) diameter respectively. The results show that local Nusselt number increased at 34% with increasing Reynolds number at 65% while increased at 11% with increasing heat flux at 71%. Heat transfer rate increase as the particle diameter increase at the range of (1 – 3) mm but decrease with increasing particle diameter at the range (3 – 10) mm. Pressure drop through channel minimize at 97% as porosity increase at 23%.Many empirical relations, obtained experimentally.

Unsteady Laminar Forced-Convective Tube Flow Under Dynamic Time-Dependent Heat Flux

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
M. Fakoor-Pakdaman ◽  
Mehdi Andisheh-Tadbir ◽  
Majid Bahrami
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Analytical Model ◽  
Time Dependent ◽  
Bulk Temperature ◽  
Fluid Temperature ◽  
Tube Flow ◽  
Flux Boundary Condition ◽  
Arbitrary Time

A new all-time model is developed to predict transient laminar forced convection heat transfer inside a circular tube under arbitrary time-dependent heat flux. Slug flow (SF) condition is assumed for the velocity profile inside the tube. The solution to the time-dependent energy equation for a step heat flux boundary condition is generalized for arbitrary time variations in surface heat flux using a Duhamel's integral technique. A cyclic time-dependent heat flux is considered and new compact closed-form relationships are proposed to predict (i) fluid temperature distribution inside the tube, (ii) fluid bulk temperature and (iii) the Nusselt number. A new definition, cyclic fully developed Nusselt number, is introduced and it is shown that in the thermally fully developed region the Nusselt number is not a function of axial location, but it varies with time and the angular frequency of the imposed heat flux. Optimum conditions are found which maximize the heat transfer rate of the unsteady laminar forced-convective tube flow. We also performed an independent numerical simulation using ansys fluent to validate the present analytical model. The comparison between the numerical and the present analytical model shows great agreement; a maximum relative difference less than 5.3%.

FORCED CONVECTION BASED HEAT TRANSFER ANALYSIS OF SPHERICAL DIMPLE AND PROTRUSION SURFACE IN TURBULENT FLOW

2017 ◽  
Vol 41 (5) ◽  
pp. 771-786 ◽  
Author(s):  
Ashif Perwez ◽  
Shreyak Shende ◽  
Rakesh Kumar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Vortex Flow ◽  
Rectangular Channel ◽  
Heat Transfer Analysis ◽  
Flow Structures ◽  
Transfer Enhancement ◽  
Heat Transfer Augmentation ◽  
Thermal Boundary Conditions

An experimental and numerical investigation is performed to study the effect of dimple and protrusion geometry on the heat transfer enhancement and the friction factor of surfaces with dimples and protrusions subjected to turbulent flow. The parameters used to compare the spherical dimples and protrusions are Nusselt Number, friction factor, and flow pattern. These parameters are obtained for a Reynolds number of 10500-60900. The spherical dimple results showed the greater heat transfer, which is about 6.97% higher and pressure loss which is 5.07% lower than the spherical protrusion. The realistic heat transfer augmentation capabilities of channels with dimples and protrusions can be studied from the experimental results. The comparison is made with respect to the smooth rectangular channel under the same flow and thermal boundary conditions. The numerical analysis is performed which shows the different vortex flow structures of the spherical dimples and protrusions channel.

scholarly journals CFD-BASED STUDY ON RELATIONSHIP BETWEEN COOLING PERFORMANCE OF PULSATING FLOW AND RIB HEIGHT MOUNTED IN MINI RECTANGULAR CHANNEL

2020 ◽  
Vol 1 (1) ◽  
pp. 26-29
Author(s):  
Shintaro Hayakawa ◽  
Takashi Fukue ◽  
Hidemi Shirakawa ◽  
Wakana Hiratsuka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Rectangular Channel ◽  
The Body ◽  
Pulsating Flow ◽  
Cfd Analysis ◽  
Human Beings ◽  
Pumping Power ◽  
Transfer Enhancement ◽  
Cooling Performance

This study aims to develop a novel water-cooled device that increases heat transfer performance while inhibiting the increase of pumping power for next-generation electronic equipment. Our previous reports have reported that the combination of the pulsating flow, which is the unsteady flow that the supply flow rate is periodically changed likes a blood in the body of human beings, and the rib has higher cooling efficiency. In this report, in order to optimize the dimensions of the ribs from the viewpoint of the cooling performance, an investigation of the pulsating flow around the rib was conducted through 2D-CFD analysis while changing the height of the rib. It was found that the level of the heat transfer enhancement was dependent on the rib height.

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