Flow and Heat Transfer Characteristics in Channels With Groove–Protrusions and Combination Effect With Ribs

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Lu Zheng ◽  
Yonghui Xie ◽  
Di Zhang ◽  
Haoning Shi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Leading Edge ◽  
Small Scale ◽  
Combination Effect ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Passive flow control and heat transfer enhancement technique has become an attractive method for device internal cooling with low resistance penalty. In the present paper, the flow and heat transfer characteristics in the small scale rectangular channel with different groove–protrusions are investigated numerically. Furthermore, the combination effect with ribs is studied. The numerical results show that on the groove side, the flow separation mainly occurs at the leading edge, and the reattachment mainly occurs at the trailing edge in accordance with the local Nusselt number distribution. On the protrusion side, the separation mainly occurs at the protrusion back porch and enhances the heat transfer at the leading edge of the downstream adjacent groove. The rectangle case provides the highest dimensionless heat transfer enhancement coefficient Nu/Nu0, dimensionless resistance coefficient f/f0, and thermal performance (TP) with the highest sensitivity of Re. When ribs are employed, the separation bubble sizes prominently decrease, especially inside the second and third grooves. The Nu/Nu0 values significantly increase when ribs are arranged, and the one-row case provides the highest heat transfer enhancement by ribs. Besides, the two-row case provides the highest Nu/Nu0 value without ribs, and the three-row case shows the lowest Nu/Nu0 value whether ribs are arranged or not.

Laminar Flow and Heat Transfer Characteristics of Colloid Suspensions in Water: A Numerical Study

2009 ◽  
Author(s):  
Khalid N. Alammar ◽  
Lin-wen Hu
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Flow Rate ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Numerical analysis is performed to examine axisymmetric laminar flow and heat transfer characteristics of colloidal dispersions of nanoparticles in water (nanofluids). Effect of volume fraction on flow and heat transfer characteristics is investigated. Four different materials, Alumina, Copper, Copper Oxide, and Graphite are considered. Heat transfer and property measurements were conducted previously for Alumina nanofluid. The measurements have shown that nanofluids can behave as homogeneous mixtures. It is found that oxide-based nanofluids offer the least heat transfer enhancement compared to elements-based nanofluids. When normalized by friction pressure drop, it is shown that graphite can have the highest effective heat transfer enhancement. For a given volume flow rate, all nanofluids exhibited linear increase in heat transfer enhancement with increasing colloids volume fraction, up to 0.05.

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.

The Effect of the Corrugation Rib Angle of Attack on the Fluid Flow and Heat Transfer Characteristics Inside Corrugated Ribbed Passage

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
A. M. I. Mohamed ◽  
R. Hoettiba ◽  
A. M. Saif
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Transfer Enhancement ◽  
Angle Of Attack ◽  
Navier Stokes ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Flow Field Characteristics

Heat transfer enhancement using corrugated ribbed passages is one of the common enhancement techniques inside heat exchangers. The present study investigated numerically the effect of the corrugation rib angle of attack on the fluid flow and heat transfer characteristics inside the corrugated ribbed passage. The commercial computational fluid dynamics code PHOENICS 2006 was used to perform the numerical analysis by solving the Navier–Stokes and energy equations. The experimental part of this study was used only to validate the numerical model, and a good agreement between the experimental results and the model was obtained. The flow field characteristics and heat transfer enhancement were numerically investigated for different corrugated rib angles of attack as follows: 90 deg, 105 deg, 120 deg, 135 deg, and 150 deg. The corrugation rib angle of attack has a great effect on the reversed flow zone, the flow reattachments, and the enhancement of the heat transfer coefficient through the duct. The recommended rib angle of attack, which gives the optimum thermohydraulic performance, is found to be between 135 deg and 150 deg. The value of the maximum thermohydraulic performance is about 3.6 for the 150 deg rib angle of attack at a Reynolds number equal to 10,000.

scholarly journals Convective Heat Transfer of Ethanol/Polyalphaolefin Nanoemulsion in Mini- and Microchannel Heat Exchangers for High Heat Flux Electronics Cooling

2021 ◽  
Author(s):  
Jaime Rios ◽  
Mehdi Kabirnajafi ◽  
Takele Gameda ◽  
Raid Mohammed ◽  
Jiajun Xu
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat ◽  
Phase Flow ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Flow And Heat Transfer

The present study experimentally and numerically investigates the flow and heat transfer characteristics of a novel nanostructured heat transfer fluid, namely, ethanol/polyalphaolefin nanoemulsion, inside a conventionally manufactured minichannel of circular cross section and a microchannel heat exchanger of rectangular cross section manufactured additively using the Direct Metal Laser Sintering (DMLS) process. The experiments were conducted for single-phase flow of pure polyalphaolefin (PAO) and ethanol/PAO nanoemulsion fluids with two ethanol concentrations of 4 wt% and 8 wt% as well as for two-phase flow boiling of nanoemulsion fluids to study the effect of ethanol nanodroplets on the convective flow and heat transfer characteristics. Furthermore, the effects of flow regime of the working fluids on the heat transfer performance for both the minichannel and microchannel heat exchangers were examined within the laminar and transitional flow regimes. It was found that the ethanol/PAO nanoemulsion fluids can improve convective heat transfer compared to that of the pure PAO base fluid under both single- and two-phase flow regimes. While the concentration of nanoemulsion fluids did not reflect a remarkable distinction in single-phase heat transfer performance within the laminar regime, a significant heat transfer enhancement was observed using the nanoemulsion fluids upon entering the transitional flow regime. The heat transfer enhancement at higher concentrations of nanoemulsion within the transitional regime is mainly attributed to the enhanced interaction and interfacial thermal transport between ethanol nanodroplets and PAO base fluid. For two-phase flow boiling, heat transfer coefficients of ethanol/PAO nanoemulsion fluids were further enhanced when the ethanol nanodroplets underwent phase change. A comparative study on the flow and heat transfer characteristics was also implemented between the traditionally fabricated minichannel and additively manufactured microchannel of similar dimensions using the same working fluid of pure PAO and the same operating conditions. The results revealed that although the DMLS fabricated microchannel posed a higher pressure loss, a substantial heat transfer enhancement was achieved as compared to the minichannel heat exchanger tested under the same conditions. The non-post processed surface of the DMLS manufactured microchannel is likely to be the main contributor to the augmented heat transfer performance. Further studies are required to fully appreciate the possible mechanisms behind this phenomenon as well as the convective heat transfer properties of nanoemulsion fluids.

Heat transfer enhancement in microchannels using ribs and secondary flows

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Karthikeyan Paramanandam ◽  
Venkatachalapathy S. ◽  
Balamurugan Srinivasan
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Secondary Flows ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose The purpose of this paper is to study the flow and heat transfer characteristics of microchannel heatsinks with ribs, cavities and secondary channels. The influence of length and width of the ribs on heat transfer enhancement, secondary flows, flow distribution and temperature distribution are examined at different Reynolds numbers. The effectiveness of each heatsink is evaluated using the performance factor. Design/methodology/approach A three-dimensional solid-fluid conjugate heat transfer numerical model is used to study the flow and heat transfer characteristics in microchannels. One symmetrical channel is adopted for the simulation to reduce the computational cost and time. Flow inside the channels is assumed to be single-phase and laminar. The governing equations are solved using finite volume method. Findings The numerical results are analyzed in terms of average Nusselt number ratio, average base temperature, friction factor ratio, pressure variation inside the channel, temperature distribution, velocity distribution inside the channel, mass flow rate distribution inside the secondary channels and performance factor of each microchannels. Results indicate that impact of rib width is higher in enhancing the heat transfer when compared with its length but with a penalty on the pressure drop. The combined effects of secondary channels, ribs and cavities helps to lower the temperature of the microchannel heat sink and enhances the heat transfer rate. Practical implications The fabrication of microchannels are complex, but recent advancements in the additive manufacturing techniques makes the fabrication of the design considered in this numerical study feasible. Originality/value The proposed microchannel heatsink can be used in practical applications to reduce the thermal resistance, and it augments the heat transfer rate when compared with the baseline design.

Experimental Study of Flow and Heat Transfer Characteristics in Silicon-Based Corrugated Microchannels

2009 ◽  
Author(s):  
Huimin Tang ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
High Efficiency ◽  
Cooling System ◽  
Width Ratio ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Total Thermal Resistance ◽  
Transfer Characteristics ◽  
Silicon Based

In this paper, the silicon-based corrugated microchannels used for the heat transfer enhancement were fabricated by MEMS technology for the first time. Both the flow and convective heat transfer characteristics of the deionized water through these corrugated microchannels were investigated experimentally, and comparisons were performed between corrugated microchannels and straight microchannels with the same cross-sectional aspect ratio (height-to-width ratio) and same hydraulic diameter. Experimental results showed that both the flow friction and Nusselt number in corrugated microchannels increased considerably compared with those in straight microchannels, and this increase became enlarged with the increase in the Reynolds number. With the same pumping power, using corrugated microchannels instead of straight microchannels caused the reduction in the total thermal resistance. The heat transfer enhancement mechanism of the corrugated microchannels was discussed. The results presented in this paper help to design the high efficiency integrated chip cooling system.

Numerical Investigation of Heat Transfer Enhancement on a Small Scale Vortex Generator

2009 ◽  
Author(s):  
Jiansheng Wang ◽  
Zhiqin Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Rectangular Channel ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Small Scale ◽  
Transfer Enhancement

The heat transfer characteristic and flow structure of fluid in the rectangular channel with different height vortex generators in small scale are investigated with numerical simulation. Meantime, the properties of heat transfer and flow of fluid in the rectangular channel are compared with the channel which located small scale vortex generator. The variation law of local heat transfer and flow structure in channel is obtained. The mechanism of heat transfer enhancement of small scale vortex generators is discussed in detail. It is found that the influence of vortex generator on heat transfer is not in proportion to the size of vortex generator. What is more, turbulent flow structure near the wall, which influences the temperature distribution near the wall, induces the variety of local heat transfer. The fluid movement towards to the wall causes the heat transfer enhanced. On the contrary, the fluid movement away from the wall decreases the local heat transfer.

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