Dual Pulsating or Steady Slot Jet Cooling of a Constant Heat Flux Surface

2003 ◽  
Vol 125 (4) ◽  
pp. 575-586 ◽  
Author(s):  
A. K. Chaniotis ◽  
D. Poulikakos ◽  
Y. Ventikos
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Stokes Equations ◽  
Chaotic Behavior ◽  
Heated Surface ◽  
Jet Impingement ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Plate Temperature ◽  
Non Linear System

The work presented in this paper focuses on the effect of jet pulsation on the heat transfer and fluid dynamics characteristics of single and double jet impingement on a constant heat flux heated surface. Specifically, the influence of frequency, amplitude and in particular, of the phase difference of the two jets on the temperature distribution of the heated surface is examined. The simulations are conducted using a novel, remeshed Smooth Particle Hydrodynamics (SPH) methodology that is based on particle discretization of the governing compressible Navier-Stokes equations. It was found that the strong aerodynamic and thermal interaction that exists between the gaseous jets and the impingement surface leads to non-linear system responses; with serious heat transfer implications. Dynamical systems analysis leads to the identification of intermittent periodic/chaotic behavior above a threshold value of the Reynolds number. As a result, a reduction in the maximum plate temperature in a window of periodic behavior was discovered.

Passive Solar Massive Wall Systems With Fins Attached on the Heated Wall and Without Glazing

2000 ◽  
Vol 122 (1) ◽  
pp. 30-34 ◽  
Author(s):  
E. Bilgen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heated Surface ◽  
Constant Heat Flux ◽  
Heated Wall ◽  
Concrete Wall ◽  
Constant Heat ◽  
Conduction Heat Transfer ◽  
Finned Surface ◽  
Passive Solar

Natural convection, radiation and conduction heat transfer in passive solar massive wall systems with fins attached to the heated surface and without glazing is experimentally studied. The system was 0.78 m high, 0.40 m wide, and 0.10 m thick concrete wall with 0.025 m long, 0.004 m thick horizontal fins made as an integral part of it and placed at 0.01 m intervals. A heat source was used to impose a constant heat flux which could be varied from about 200 to 800 W/m2. Temperatures at various points and heat flux by convection at the back were measured. Using periodicity hypothesis and various assumptions, the wall with fins was also analyzed theoretically. The results indicate that for the case considered, about 35 percent of the heat flux imposed on the finned surface goes through the system and is dissipated at the back. [S0199-6231(00)00701-2]

An analytical approach for optimal design of heat sinks under forced convection

2013 ◽  
Vol 3 (2) ◽  
Author(s):  
Antonio Miguel
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Transfer Rate ◽  
Analytical Approach ◽  
Constant Heat Flux ◽  
Heat Sinks ◽  
Pumping Power ◽  
Fluid Stream ◽  
Design Standards ◽  
Constant Heat

AbstractSaving energy is just as important as generating energy. In this paper, we seek an optimized structure that achieves a certain level of heat transfer rate under a minimum pumping power to drive the fluid stream. Constraints are specified by the flow regime (laminar and turbulent), admissible boundary conditions on the walls (prescribed temperature and constant heat flux), and design standards. The study will help designers with more effective basic tools for the conceptual design of system and in establishing proper operating procedures.

Heat Transfer Characteristics of Gaseous Flows in Micro-Channels With Negative Heat Flux

2006 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Constant Heat Flux ◽  
Channel Height ◽  
Gas Temperature ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Transfer Characteristics ◽  
Micro Channels ◽  
Gaseous Flows

Two-dimensional compressible momentum and energy equations are solved to obtain the heat transfer characteristics of gaseous flows in micro-channels with CHF (constant heat flux) whose value is negative. The combined effect of viscous dissipation and compressibility is also investigated. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations are performed for channels with constant heat flux with range from −104 to −102 Wm−2. The channel height ranges from 10 to 100 μm and the aspect ratio of the channel height and length is 200. The stagnation pressure varies from 120 to 500 kPa. The outlet pressure is fixed at the atmosphere. The wall and bulk temperatures in micro-channels are compared with those of the case of positive heat flux and also compared with those of the incompressible flow in a conventional sized channel. In the case of negative heat flux, temperature profiles normalized by heat flux have different trends in the case of positive heat flux, when flow is fast. A gas temperature falls down due to the energy conversion. A correlation for the prediction of the wall temperature of the gaseous flow in the micro-channel is proposed.

On Effects of Temperature Boundary Conditions on Heat Transfer in Turbulent Low-Prandtl-Number Flows

2020 ◽  
Author(s):  
Ivan Otic
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Boundary Conditions ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Flux Boundary Condition ◽  
Large Eddy ◽  
Heat Flux Boundary Condition ◽  
Effects Of Temperature

Abstract One important issue in understanding and modeling of turbulent heat transfer is the behavior of fluctuating temperature close to the wall. Common engineering computational approach assumes constant heat flux boundary condition on heated walls. In the present paper constant heat flux boundary condition was assumed and effects of temperature fluctuations are investigated using large eddy simulations (LES) approach. A series of large eddy simulations for two geometries is performed: First, forced convection in channels and second, forced convection over a backward facing step. LES simulation data is statistically analyzed and compared with results of direct numerical simulations (DNS) from the literature which apply three cases of heat flux boundary conditions: 1. ideal heat flux boundary condition, 2. non-ideal heat flux boundary condition, 3. conjugate heat transfer boundary condition. For low Prandtl number flows LES results show that, despite very good agreement for velocities and mean temperature, predictions of temperature fluctuations may have strong deficiencies if simplified boundary conditions are applied.

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