Convective heat transfer on a flat surface induced by a vertically-oriented piezoelectric fan in the presence of cross flow

2017 ◽  
Vol 53 (9) ◽  
pp. 2745-2768 ◽  
Author(s):  
Xin-Jun Li ◽  
Jing-zhou Zhang ◽  
Xiao-ming Tan
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flat Surface ◽  
Cross Flow

scholarly journals Conjugate Heat Transfer CFD Predictions of Impingement Jet Array Flat Wall Cooling Aerodynamics With Single Sided Flow Exit

2013 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Significant Feature ◽  
Axial Distance ◽  
Impingement Jet ◽  
The Cross

Conjugate heat transfer CFD studies were undertaken on impingement square jet arrays with self induced crossflow in the impingement gap with a single sided exit. The aim was to understand the aerodynamic interactions that result in the deterioration of heat transfer with axial distance, whereas the addition of duct flow heat transfer would be expected to lead to an increase in heat transfer with axial distance. A square array of impingement holes was investigated for a common geometry investigated experimentally, pitch to diameter ratio X/D of 5 and impingement gap to diameter ratio Z/D of 3.3 for 11 rows of holes in the crossflow direction. A metal duct wall was used as the impingement surface with an applied heat flux of 100kW/m2, which for a gas turbine combustor cooling application operating at steady state with a temperature difference of ∼450K corresponds to a convective heat transfer coefficient of ∼200 W/m2K. A key feature of the predicted aerodynamics was recirculation in the plane of the impingement jets normal to the cross-flow, which produced heating of the impingement jet wall. This reverse flow jet was deflected by the cross flow which had its peak velocity in the plane between the high velocity impingement jets. The cross-flow interaction with the impingement jets reduced the interaction between the jets on the surface, with lower surface turbulence as a result and this reduced the surface convective heat transfer. A significant feature of the predictions was the interaction of the cross-flow aerodynamics with the impingement jet wall and associated heat transfer to that wall. The results showed that the deterioration in heat transfer with axial distance was well predicted, together with predictions of the impingement wall surface temperature gradients.

scholarly journals ON THE CALCULATION OF CONVECTIVE HEAT TRANSFER UNDER MUTUAL-ACTION OF A JET WITH LIMITING SURFACE

2019 ◽  
Vol 62 (3) ◽  
pp. 208-214
Author(s):  
I. A. Pribytkov ◽  
S. I. Kondrashenko
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Flux Density ◽  
Convective Heat ◽  
Heat Flux Density ◽  
Flat Surface ◽  
Dynamic Potential ◽  
Velocity Coefficient ◽  
Limiting Surface

The paper proposes a method for calculating convective heat transfer in the interaction of a single circular jet with a flat surface. The differences of the proposed method from the existing ones are given. The concepts “energodynamic potential of the flow” and “energodynamic power of the flow” are introduced, allowing to determine the intensity of convective heat transfer at “gas-solid” boundary. Differences of the proposed definitions from the existing ones are given: heat flux and heat flux density. The principal difference between the heat flux density q and the energy dynamic potential qэ is as follows: the heat flux density q for convective heat transfer problems means the amount of heat that is transferred from a liquid to a solid surface (or vice versa) per unit of time through a unit of heat exchange surface area. Thus, quantity q characterizes the intensity of convective heat transfer process at the interface. The energy dynamic potential qэ characterizes the flow property as a source or carrier of heat. Value of qэ characterizes the specific energy power of the fluid flow. When calculating the heat transfer, it was proposed to divide the jet when interacting with the flat surface into two parts: before the interaction – the jet part, after – the fan flow. The method for calculating convective heat transfer under jet heating, in which the Reynolds criterion calculated by characteristics of the gas at the nozzle exit is decisive, is not entirely correct. It is proposed to use criteria specific to the fan flow. Characteristic values for the fan flow are its initial average velocity Uвп, distance from the critical point of the jet (point of intersection of vertical axis of the jet with the surface) to the current coordinate of radius downstream. To assess the changes in basic characteristics of a free jet at different distances from the nozzle exit to limiting surface, dependences of the following criteria are presented: jet expansion coefficient; jet injection coefficient; velocity coefficient for any jet section; velocity coefficient for any jet section, except h/d0 = 0; relation of the Reynolds criteria, confirming the need to carry out calculations of heat transfer on the values characteristic separately for the fan flow.

Calculation of Convective Heat Transfer of Plane Surfaces with Wire-Net Finning Immersed in a Cross-Flow

2005 ◽  
Vol 36 (1-2) ◽  
pp. 39-46 ◽  
Author(s):  
E. N. Pis'mennyi ◽  
A. M. Terekh ◽  
V. A. Rogachev ◽  
V. D. Burlei ◽  
A. I. Rudenko
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Cross Flow
Sign in / Sign up

Export Citation Format

Share Document