Heat Transfer Enhancement in Rectangular Channels with Concavities

1999 ◽  
Vol 6 (6) ◽  
pp. 429-439 ◽  
Author(s):  
MinKing Chyu ◽  
Y. Yu ◽  
H. Ding
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Transfer Enhancement ◽  
Rectangular Channels

Numerical Study on the Flow and Heat Transfer Characteristics in Rectangular Channels With Grooves and Different Protrusions

2017 ◽  
Author(s):  
Feng Zhang ◽  
Xinjun Wang ◽  
Jun Li ◽  
Daren Zheng ◽  
Junfei Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rectangular Channels

The present work represents a numerical study on the flow and heat transfer characteristics in rectangular channels with protrusion-grooved turbulators. The Reynolds averaged Navier-Stokes equations, coupled with SST turbulence model, are adopted and solved. In this paper, six geometric protrusion shapes (circular, rectangular, triangular, trapezoidal, circular with leading round concave and circular with trailing round concave) are selected to perform the study. The flow structure, heat transfer enhancement, friction factor as well as thermal performance factor of the rectangular channel fitted with combined groove and different protrusions have been obtained at the Reynolds number ranging from 5000 to 20000. The results indicate that the protrusion shapes affect the velocity distribution near the groove surface. The case of circular protrusion with leading round concave provides the highest overall heat transfer enhancement, while it also causes the highest pressure loss penalty. The case of rectangular protrusion has the lowest overall heat transfer enhancement with high pressure loss penalty. The case of circular protrusion has similar overall heat transfer enhancement with cases of trapezoidal protrusion as well as circular protrusion with trailing round concave, but the pressure loss penalty of the case of circular protrusion is the lowest. In addition, the best overall thermal performance can be observed for circular protrusion-grooved channel.

scholarly journals Internal Cooling Using Novel Swirl Enhancement Strategies in a Slot Shaped Single Pass Channel

2010 ◽  
Author(s):  
Del Segura ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Turbine Blades ◽  
Main Channel ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Mean Velocity ◽  
Performance Factors ◽  
Air Temperatures ◽  
Rectangular Channels

Heat transfer results for a given slot shaped channel with a 3:1 aspect ratio are presented using various methods to enhance swirl in the channel including helical shaped-trip-strips and swirl-jets issuing from the side walls. Four different configurations of the swirl jets and one configuration of the helical trip strips were studied. The Reynolds numbers investigated range from 10,000 to 50,000 and are based on the mean velocity of the fluid at the channel inlet, or when swirl-jets are used, the equivalent mass flow rates at the exit of the main channel. Independently these heat transfer enhancement strategies have proven to be effective in either round channels, in the case of swirl jets and helical protrusions, or rectangular channels, in the case of trip strips. A transient technique combined with Duhamel’s superposition theorem was used to obtain the heat transfer coefficient distributions. Narrow-band liquid crystals were used to map the transient surface temperatures and were combined with thermocouples that measured the bulk-air temperatures along the flow path in the main channel. The results for the tests reported in this paper show mean heat transfer enhancement values (Nu/Nuo) greater than 4.5 and low normalized friction factors. Thermal performance factors ranged from 1.1–3.3 for the various configurations studied. These results show significant improvements over other types of heat transfer enhancement methods currently used in the mid-span section of turbine blades.

scholarly journals A Numerical Investigation of Turbulent Flow and Heat Transfer in Rectangular Channels With Elliptic Scale-Roughened Walls

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Feng Zhou ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Volume Averaging ◽  
Spanwise Direction ◽  
Transfer Enhancement ◽  
Pressure Drops ◽  
Flow Mixing ◽  
Rectangular Channels

In the present paper, rectangular channels with six types of elliptic scale-roughened walls for heat transfer enhancement are numerically studied. Heat transfer and fluid flow characteristics for sixteen different scale-roughened models (with the scale height varying in the range from 1 mm to 2.5 mm) are numerically predicted using commercial computational fluid dynamics (CFD) code, Ansys cfx. The turbulent model employed is the k–ω based shear–stress transport (SST) model with automatic wall function treatment. In the performance evaluation, we use a “universal” porous media length scale based on volume averaging theory (VAT) to define the Reynolds number, Nusselt number, and friction factor. It is found that heat transfer performance is most favorable when the elliptic scales are oriented with their long axis perpendicular to the flow direction, while the scales elongated in the flow direction have lower Nusselt numbers and pressure drops compared with the circular scale-roughened channels. Results indicate that the scale-shaped roughness strongly spins the flow in the spanwise direction, which disrupts the near-wall boundary layers continuously and enhances the bulk flow mixing. With the flow marching in a more intense spiral pattern, a 40% improvement of heat transfer enhancement over the circular scale-roughened channels is observed.

Ionic Wind Heat Transfer Enhancement in Vertical Rectangular Channels: Experimental Study and Model Validation

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Noris Gallandat ◽  
Federico Bonetto ◽  
J. Rhett Mayor
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Natural Convection ◽  
Heat Transfer Enhancement ◽  
Heat Sink ◽  
High Reliability ◽  
Ionic Wind ◽  
Transfer Enhancement ◽  
Wind Generator ◽  
Rectangular Channels

This paper presents the results of an experimental study of ionic wind heat transfer enhancement in internal rectangular channels. Ionic wind is a potential technique to enhance natural convection cooling noise-free and without using moving part and thus ensuring a high reliability and a long lifetime. The goal of the present study is twofold: first, the multiphysics numerical model of ionic wind developed in previous work is validated experimentally. Second, the potential of the heat sink concept combining a fin array with an ionic wind generator is demonstrated by building a technology demonstrator. The heat sink presented in this work dissipates 240 W on a baseplate geometry of 200 × 263 mm. It is shown that the baseplate temperature can be reduced from 100 °C under natural convection to 81 °C when the ionic wind generator is turned on.

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