The effects of inlet temperature frequency on the quasi-steady approach of periodic conjugated heat transfer problem

2004 ◽  
Vol 42 (8-9) ◽  
pp. 825-839 ◽  
Author(s):  
K. Mansouri ◽  
D. Sadaoui ◽  
B. Fourcher
Keyword(s):  
Heat Transfer ◽  
Transfer Problem ◽  
Heat Transfer Problem ◽  
Inlet Temperature ◽  
Conjugated Heat Transfer

scholarly journals Heat Transfer Coefficient Determination during FC-72 Flow in a Minichannel Heat Sink Using the Trefftz Functions and ADINA Software

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6647
Author(s):  
Magdalena Piasecka ◽  
Beata Maciejewska ◽  
Paweł Łabędzki
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Transfer Problem ◽  
Heat Transfer Problem ◽  
Heated Wall ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Flowing Fluid

This work focuses on subcooled boiling heat transfer during flow in a minichannel heat sink with three or five minichannels of 1 mm depth. The heated element for FC-72 flowing along the minichannels was a thin foil of which temperature on the outer surface was measured due to the infrared thermography. The test section was oriented vertically or horizontally. A steady state heat transfer process and a laminar, incompressible flow of the fluid in a central minichannel were assumed. The heat transfer problem was described by the energy equations with an appropriate system of boundary conditions. Several mathematical methods were applied to solve the heat transfer problem with the Robin condition to determine the local heat transfer coefficients at the fluid/heated foil interface. Besides the 1D approach as a simple analytical method, a more sophisticated 2D approach was proposed with solutions by the Trefftz functions and ADINA software. Finite element method (FEM) calculations were conducted to find the temperature field in the flowing fluid and in the heated wall. The results were illustrated by graphs of local heated foil temperature and transfer coefficients as a function of the distance from the minichannel inlet. Temperature distributions in the heater and the fluid obtained from the FEM computations carried out by ADINA software were also shown. Similar values of the heat transfer coefficient were obtained in both the FEM calculations and the 1D approach. Example boiling curves indicating nucleation hysteresis are shown and discussed.

scholarly journals On the Thermal Performance of a Microparallel Channels Heat Exchanger

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Ivana Fernandes de Sousa ◽  
Carolina Palma Naveira Cotta ◽  
Daduí Cordeiro Guerrieri ◽  
Manish K. Tiwari
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Exchanger ◽  
Theoretical Analysis ◽  
Transfer Problem ◽  
Heat Transfer Problem ◽  
Coolant Fluid ◽  
Differential Formulation ◽  
Micro Heat Exchanger ◽  
Conjugated Heat Transfer

Abstract This paper presents the experimental and theoretical analysis of a micro heat exchanger designed for the waste heat recovery from a high concentration photovoltaic (HCPV) system. A test bench was built to analyze the thermal behavior of a heat exchanger targeted to work in a similar condition of an existing HCPV panel. A high power heater was encapsulated inside a copper cartridge, covered by thermal insulation, leading to dissipated heat fluxes around 0.6 MW/m2, representative of the heat flux over the solar cell within the HCPV module. The experimental campaign employed water as the coolant fluid and was performed for three different mass flow rates. An infrared camera was used to nonintrusively measure the temperature field over the micro heat exchanger external surface, while thermocouples were placed at the contact between the heat exchanger and the heater, and at the water inlet and outlet ports. In the theoretical analysis, a hybrid numerical–analytical treatment is implemented, combining the numerical simulation through the comsolmultiphysics finite elements code for the micro heat exchanger, and the analytical solution of a lumped-differential formulation for the electrical heater cartridge, offering a substantial computational cost reduction. Such computational simulations of the three-dimensional conjugated heat transfer problem were critically compared to the experimental results and also permitted to inspect the adequacy of a theoretical correlation based on a simplified prescribed heat flux model without conjugation effects. It has been concluded that the conjugated heat transfer problem modeling should be adopted in future design and optimization tasks. The analysis demonstrates the enhanced heat transfer achieved by the microthermal system and confirms the potential in reusing the recovered heat from HCPV systems in a secondary process.

Numerical Analysis of the Conjugated Heat Transfer Problem for Mixed Electro-Osmotic and Pressure-Driven Flows of Phan-Thien Tanner Fluids in Microchannels

2010 ◽  
Author(s):  
Juan P. Escando´n ◽  
Oscar E. Bautista ◽  
Federico Me´ndez
Keyword(s):  
Heat Transfer ◽  
Newtonian Fluid ◽  
Transfer Problem ◽  
Viscoelastic Behavior ◽  
Heat Transfer Problem ◽  
Fluid Temperature ◽  
Cross Sectional ◽  
Viscoelastic Parameter ◽  
Numerical Process ◽  
Conjugated Heat Transfer

In this work we solve numerically the conjugated heat transfer problem of a non-Newtonian fluid and solid walls in a microchannel under the influence of pressure and electro-osmotic forces. The velocity field is determined taking into account a hydrodynamically fully-developed flow and a constitutive relation based in a viscoelastic rheological model with a simplified Phan-Thien Tanner fluid. The numerical process results in solid and fluid temperature distributions. Is shown the influence of nondimensional parameters involved in the analysis on the conjugated heat transfer problem: an indicator of viscoelastic behavior, the Peclet number, a normalized power generation term being the ratio of heat flow from the external wall to the Joule heating, a conjugation term which determines the basic heat transfer regimes between fluid and solid sections in the microchannel. For the flow field: the ratio of pressure forces to the electro-osmotic forces acts on flow as a drag reducer and drag increaser under favorable and adverse pressure gradients, respectively, moreover, for increasing values of the viscoelastic parameter, the velocity of the fluid increases with respect the Newtonian fluid flow case. These velocity perturbations resulting in cross-sectional variations of temperature.

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