Heat transfer enhancement and thermal–hydraulic performance in laminar flows through asymmetric wavy walled channels

2016 ◽  
Vol 97 ◽  
pp. 450-460 ◽  
Author(s):  
Zachary Grant Mills ◽  
Alok Warey ◽  
Alexander Alexeev
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Hydraulic Performance ◽  
Laminar Flows ◽  
Transfer Enhancement

Experimental and Numerical Investigations of Thermal Hydraulic Performance in Ribbed Channel for Combustor Liner

2019 ◽  
Author(s):  
Divya Bihari ◽  
Sanjay Bokade
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Rectangular Channel ◽  
Hydraulic Performance ◽  
Transfer Enhancement ◽  
Ansys Fluent ◽  
Transfer Measurement ◽  
Steady State Heat Transfer

Abstract The present study assess the thermal hydraulic performance of V-shaped, W-shaped and 2W-shaped ribs in a rectangular channel with an aspect ratio of 6:1. The rib-roughened copper plates were located at the bottom of the channel to simulate the backside wall cooling of gas turbine combustor liners. The rib height-to-hydraulic diameter ratio (e/Dh) was 0.05834 and the rib pitch-to-height ratio (P/e) was 10 for all the cases. The experiments were carried out at the Reynolds numbers ranging from 32000 to 72000. A steady state heat transfer measurement method is used to investigate the heat transfer enhancement of ribbed wall against a smooth wall. Pressure taps were located at two stream-wise locations in channel walls to measure the pressure loss. To validate the understanding of experimental data, all the rib configurations were investigated numerically using ANSYS FLUENT. A low Reynolds number k-ε turbulence model was used to predict the heat transfer in the channel. The results show that the 2W ribs have the highest heat transfer and pressure loss characteristics in channel. It gives around 1.4–1.6 times increase in average Nusselt number and 2.7–3.3 times increase in friction factor as compare to smooth plate. Among all the cases V ribs obtained lowest heat transfer and pressure loss characteristics. Furthermore, both heat transfer enhancement and pressure loss increases with increasing Reynolds number.

Use of artificial roughness to enhance heat transfer in solar air heaters – a review

2010 ◽  
Vol 21 (1) ◽  
pp. 35-51 ◽  
Author(s):  
Thakur Sanjay Kumar ◽  
N.S. Thakur ◽  
Anoop Kumar ◽  
Vijay Mittal
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Hydraulic Performance ◽  
Solar Air Heater ◽  
Artificial Roughness ◽  
Transfer Enhancement ◽  
Air Heater ◽  
Roughness Elements

Improvement in the thermo hydraulic performance of a solar air heater can be done by enhancing the heat transfer. In general, heat transfer enhancement techniques are divided into two groups: active and passive techniques. Providing an artificial roughness on a heat transferring surface is an effective passive heat transfer technique to enhance the rate of heat transfer to fluid flow. In this paper, reviews of various artificial roughness elements used as passive heat transfer techniques, in order to improve thermo hydraulic performance of a solar air heater, is done. The objective of this paper is to review various studies, in which different artificial roughness elements are used to enhance the heat transfer rate with little penalty of friction. Correlations developed by various researchers with the help of experimental results for heat transfer and friction factor for solar air heater ducts by taking different roughened surfaces geometries are given in tabular form. These correlations are used to predict the thermo hydraulic performance of solar air heaters having roughened ducts. The objective is to provide a detailed review on heat transfer enhancement by using an artificial roughness technique. This paper will be very helpful for the researchers who are researching new artificial roughness for solar air heater ducts to enhance the heat transfer rate and comparing with artificial roughness already studied by various researchers.

Injection, Transport and Removal of Gas Bubbles in Microchannels for Heat Transfer Enhancement

2010 ◽  
Author(s):  
Daniel Attinger
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Enhancement ◽  
Thin Liquid Film ◽  
Film Coating ◽  
Porous Membrane ◽  
Laminar Flows ◽  
Heat Fluxes ◽  
Transfer Enhancement ◽  
Segmented Flow

Liquid cooling is an efficient way to remove heat fluxes with magnitudes up to 10,000 W/cm2. One limitation of single-phase microchannel heat transfer is the relatively low Nusselt number, due to laminar flow. Several methods have been used to improve the Nusselt number such as geometric obtrusions, pins and fins and nanofluids. In this talk, we experimentally investigate the heat transfer enhancement of a heat sink where air bubbles are periodically injected. The segmented flow pattern generates recirculation loops that enhance transport phenomena. We show that segmented flow can enhance the Nusselt number of laminar flows in short channels by a factor two. Also, we demonstrate a simple and high-throughput method for removing bubbles from microchannels, using a hydrophobic porous membrane. The role of the thin liquid film coating the bubbles in the heat transfer and the bubble removal is investigated.

Vortex Heat Transfer Enhancement in Narrow Channel by Oval Dimples Arrangement

2013 ◽  
Author(s):  
Sergey Isaev ◽  
Yaroslav Chudnovsky ◽  
Alexander Leontiev ◽  
Nikolai Kornev ◽  
Egon Hassel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Numerical Study ◽  
Heated Surface ◽  
Spherical Shape ◽  
Narrow Channel ◽  
Constant Heat Flux ◽  
Hydraulic Performance ◽  
Equivalent Diameter ◽  
Transfer Enhancement

There are many passive techniques of heat transfer enhancement ranging from surface (2D) to volumetric (3D) vortex generators, however only a few of them are capable to provide a reliable increase in a heat transfer rate overrunning the increase in pressure losses. One of such successful techniques is the profiling of a heat transfer surface with the regulated arrangement of 3D cavities (dimples). The authors explored that the deviation of the dimple geometry from the spherical shape affects the flow structure and thermal and hydraulic performance of the dimpled wall. Detailed numerical simulation of fluid flow and heat transfer has been performed in the narrow channel with the 2.5 × 0.33 cross section normalized by the equivalent diameter of the dimple footprint at the constant Reynolds number Re = 10,000 and the constant heat flux through the dimpled wall. The oval dimple geometry was varied by changing the aspect ratio of the dimple footprint from 1 to 4.5 keeping the same footprint area. In the course of the numerical study, the optimal geometry, the arrangement and the orientation of oval dimples on the heated surface to achieve the superior thermal and hydraulic performance over the spherical cavities are established. Numerical results of local and integral heat transfer characteristics enhanced with the visual representation of the generated vortices clearly illustrated the flow restructuring and an increase in the thermal and hydraulic performance.

Thermal-Hydraulic Performance Enhancement by the Combination of Rectangular Winglet Pair and V-Shaped Dimples

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Inderjot Kaur ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Hydraulic Performance ◽  
Channel Height ◽  
Transfer Enhancement ◽  
Spacing Variation ◽  
Lower Heat

Abstract This paper presents numerical study on heat transfer enhancement due to the combination of rectangular winglet pair with V-dimples in an array-type arrangement. Array of rectangular winglet pairs results in heat transfer enhancement, however, at a cost of significant pressure drop, resulting in reduced thermal-hydraulic performance (THP). On the other hand, dimples are associated with lower heat transfer enhancement levels at relatively lower pumping power penalty. To this end, a combination of rectangular winglet pair and V-shaped dimples has been studied in this paper, where the arrangements were intended to achieve enhanced thermal-hydraulic performance. Three different configurations, namely, rectangular winglet pair, rectangular winglet pair with one V-dimple between two consecutive winglets, and rectangular winglet pair with two V-dimples packed in a pitch, are studied here. The variation of heat transfer enhancement, pressure drop gain, and THP with respect to winglet-to-winglet (S) spacing variation for rectangular winglet pair and rectangular winglet pair with one V-dimple configuration is presented at a Reynolds number of 25,000. The THP of the rectangular winglet pair configuration decreases up to S/H equal to 2.5 and then increases (H: channel height). For rectangular winglet pair with one V-dimple, three values of winglet-to-dimple (P) spacings are analyzed. For fixed S/H, the highest P/H configuration provided highest heat transfer enhancement and THP. Among the three configurations studied, rectangular winglet pair with two V-dimples resulted in the highest thermal-hydraulic performance.

THE EFFECT OF VORTEX GENERATOR BASE LENGTH ON THERMAL HYDRAULIC PERFORMANCE ACROSS FIN-AND-TUBE HEAT EXCHANGER

2017 ◽  
Vol 79 (7-3) ◽  
Author(s):  
Mohd Fahmi Md Salleh ◽  
Mazlan Abdul Wahid ◽  
Seyed Alireza Ghazanfari
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Vortex Generator ◽  
Hydraulic Performance ◽  
Base Length ◽  
Transfer Enhancement ◽  
Tube Heat Exchanger ◽  
Baseline Case

Heat transfer enhancement is believed can be achieved by using vortex generator. In the past decades, many researches have been performed to investigate the effect of various vortex generator geometry and parameters including vortex generator angle of attack and height. However, less study has been conducted to investigate the influence of vortex generator length at different arrangement towards the heat transfer performance across the fin-and-tube heat exchanger (FTHE). Therefore, the effects of different strategy on the rectangular winglet vortex generator (RWVG) base length towards the thermal hydraulic performance across the FTHE were numerically investigated in this study. Two types of RWVG arrangement known as common flow down (CFD) or common flow up (CFU) arrangement were used and placed behind four rows of tube in inline arrangement. Total of 7 cases were investigated including the default RWVG, extended front and extended back for both RWVG in CFD and CFU arrangement together with FTHE without vortex generator which was set as the baseline case. The Reynolds number ranged from 500 to 900. It was found that the size of the wake region behind the RWVG contributed to the additional pressure drop penalty across the FTHE. Meanwhile, different thermal characteristics were found for different base length strategy in CFD and CFU arrangement. For RWVG arranged in CFD and CFU arrangement, the extended back case shows the highest heat transfer enhancement with 5 – 25 % and 5 – 15 % increment compared to the baseline case respectively. Based on JF factor evaluation, default RWVG in CFU arrangement provide better heat transfer enhancement than the pressure drop penalty compared to other RWVG cases with average JF factor value is 0.8. Nonetheless, none of the tested cases shows higher JF factor value than the baseline case.  

Laminar Heat Transfer Enhancement Utilizing Nanofluids in a Chaotic Flow

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
A. Tohidi ◽  
S. M. Hosseinalipour ◽  
Z. Ghasemi Monfared ◽  
A. S. Mujumdar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Laminar Flows ◽  
Chaotic Advection ◽  
Al2o3 Nanoparticles ◽  
Transfer Enhancement ◽  
Volumetric Concentration ◽  
Chaotic Flow

This work numerically examined effects of nanofluids flow on heat transfer in a C-shaped geometry with the aim to evaluate potential advantages of using nanofluids in a chaotic flow. Numerical computations revealed that the combination of nanofluids and chaotic advection can be an effective way to improve thermal performance of laminar flows. The results indicated that addition of only 1–3% CuO or Al2O3 nanoparticles (volumetric concentration) to the chaotic flow improved heat transfer by 4–14% and 4–18%, respectively, with a marginal increase in the pressure drop.

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