scholarly journals Thermal performance augmentation in round tube with louvered V-winglet vortex generator

2022 ◽  
Vol 182 ◽  
pp. 121913
Author(s):  
Pongjet Promvonge ◽  
Pitak Promthaisong ◽  
Sompol Skullong
Keyword(s):  
Thermal Performance ◽  
Vortex Generator ◽  
Round Tube

Heat Transfer Augmentation and Flow Visualization With Delta Winglets in a Tube: A Numerical Approach

2020 ◽  
Author(s):  
Md. Islam ◽  
Liang Guangda ◽  
Md. Mahbub Alam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Swirling Flow ◽  
Circular Tube ◽  
Vortex Generator ◽  
Attack Angle ◽  
Maximum Enhancement ◽  
Longitudinal Vortices

Abstract In this research, heat transfer and pressure penalty from a circular tube with delta winglets insert are numerically investigated through Computational Fluid Dynamics (CFD) methodology. Numerical analysis with and without vortex generators (VGs) insert in a tube are done for a turbulent air flow, Reynolds number ranging from 6000 to 33000, under constant heat flux condition on the circular tube model surface. In our current research, we employed the shear stress transport (SST) k-omega model. The Nusselt number and friction factor results show the influence of the VGs insert on thermal performance. Effects of different winglet attack angles and blockage ratios on thermal performance enhancement were examined. Thermal performance is enhanced 5.1–30.7% using winglets in a tube. It is observed that small blockage ratio, B = 0.1 performed better than its counterpart of 0.2 and 0.3 for all the Reynolds number and for the same attack angle. The attack angle β = 15° and 30° showed better thermal performance enhancement at lower Re while at higher Re, β = 15° showed better performance. The maximum enhancement obtained for β = 30° and B = 0.1. Winglet vortex generator could create swirling flow when attack angle is 0 or 15°. When attack angle is increased, both swirling flow and longitudinal vortices appeared. At attack angle of 45°, large longitudinal vortices was found.

Experimental Research on Microchannel Heat Exchanger Performance for Residential Air Conditioner Applications

2009 ◽  
Author(s):  
Jianghong Wu ◽  
Shuangfeng Wang ◽  
Yunting Ge
Keyword(s):  
Heat Exchanger ◽  
Thermal Performance ◽  
Air Conditioning ◽  
The Other ◽  
Air Conditioner ◽  
Round Tube ◽  
Tube Heat Exchanger ◽  
Face Area ◽  
Residential Air Conditioning ◽  
Air Conditioning Systems

Two type condensers of R22 residential air conditioning systems were investigated in this study. Two R22 residential air-conditioning systems, one with a microchannel condenser and the other with a round-tube condenser, were examined experimentally, while the other components of the two systems were identical except the condensers. Based on the principle of the microchannel condensation, the analysis of heat transfer along parallel heat exchanger was conducted. The non-uniform air velocity distribution at the face of the microchannel condenser and refrigerant distribution in headers were taken into account in this research. The mechanism and possibility of the superior thermal performance as compared with conventional fin-tube heat exchangers were discussed. In addition, the maximum of thermal performance influenced by the running parameter was experimentally measured. The experimental results show that with one third face area of round tube heat exchanger, microchannel condenser’s pressure drop increase around 12–23% and refrigeration output increase 2–5%, refrigerant charge decreases around 50%, it is found to be a promising candidate for residential air conditioning condenser.

Heat Transfer Enhancement With Delta Winglets Vortex Generator for Different Arrangement in a Circular Tube

2018 ◽  
Author(s):  
Md. Islam ◽  
A. Nurizki ◽  
A. Kareem ◽  
A. Baba
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Circular Tube ◽  
Flow Behavior ◽  
Vortex Generator ◽  
Attack Angle ◽  
Transfer Performance ◽  
Pitch Ratio

Various technologies have been developed to enhance the heat transfer. Vortex generator (VG) is one of the passive techniques which can change the flow behavior and ultimately enhances the heat transfer performance. Delta winglet (DW) vortex generator can create longitudinal and horseshoe vortices which do not decay until further downstream and consequently increase heat transfer coefficient with comparatively lower pressure drop. With this vortex generator, it is expected to have higher Nusselt number with some increase of friction factor. Therefore, this study is to study the effect of pitch ratio (PR) and attack angle (B) of DW vortex generator to increase the thermal performance of heat exchanger. Four delta winglets are attached into a ring. Those rings attached with VGs will be used to investigate the influence of different parameters to heat transfer performance. In this study VGs were placed inside a circular copper tube and the heating coil was wrapped up around the outer surface of the copper tube to generate a constant heat flux condition. The experimental setup consists of a blower, orifice meter, flow straightener, calm/flow developing section and test section. The results show the friction factor, Nusselt number, and Thermal Performance Enhancement. It increases the thermal performance due to the formation of longitudinal vortex inside the circular tube. Pitch ratio and attack angle seem to have significant impact on the flow and heat transfer. The Pitch ratio of 1.6 have the highest impact on both (f/f0) and (Nu/Nuo) followed by attack angle. Smoke flow visualization technique was used to study flow behavior and flow structures.

Numerical Evaluation of Thermal Hydraulic Performance in Fin-and-Tube Heat Exchangers With Various Vortex Generator Geometries Arranged in Common-Flow-Down or Common-Flow-Up

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Mohd Fahmi Md Salleh ◽  
Ahmadali Gholami ◽  
Mazlan A. Wahid
Keyword(s):  
Reynolds Number ◽  
Thermal Performance ◽  
Vortex Generator ◽  
Simulation Method ◽  
Hydraulic Performance ◽  
Vortex Generators ◽  
Tube Heat Exchanger ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Baseline Case

Vortex generator as secondary flow enhancement technique has captured the attention of many researchers recently to augment the performance of the fin-and-tube heat exchanger (FTHE). There are various vortex generator parameters that influence the thermal and hydraulic performance in the FTHE such as the geometry and arrangement. In this study, the effect of different vortex generator geometries and arrangements was investigated using numerical simulation method. There are three vortex generator geometries studied including rectangular winglet (RWVG), delta winglet (DWVG), and trapezoidal winglet (TWVG). The vortex generators were placed behind tubes either in common flow down (CFD) or common flow up (CFU) arrangement. The introduction of vortex generators behind tubes resulted in heat transfer augmentation but comes together with higher pressure drop penalty. Further analysis on the thermal performance has found that TWVG in CFU arrangement almost obtained similar thermal performance factor with respect to the baseline case at Reynolds number 500 and 600. However, the thermal performance factor for TWVG in CFU arrangement decreases as the Reynolds number further increased. For other vortex generator cases, lesser thermal performance factor was found as compared to the baseline case.

THERMAL PERFORMANCE OF SINE WAVE FIN-AND-OVAL TUBE HEAT EXCHANGERS

2013 ◽  
Vol 21 (01) ◽  
pp. 1350008 ◽  
Author(s):  
NAE-HYUN KIM ◽  
KANG-JONG LEE ◽  
JI-CHAO HAN ◽  
BYUNG-NAM CHOI
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Sine Wave ◽  
Heat Transfer Characteristics ◽  
Round Tube ◽  
Flow And Heat Transfer ◽  
Wave Channel ◽  
Oval Tube

Experiments were conducted on sine wave fin-and-tube heat exchangers having oval tubes of 0.6 aspect ratio. Twelve samples having different fin pitches and tube rows were tested. Eight herringbone wave fin-and-tube heat exchangers having round tubes were also tested. For round tube samples, the effect of tube row on j factor is not prominent. For oval tube samples, however, the highest j factor is observed for two row configuration, whereas the lowest one is observed for one row configuration. Possible reasoning is provided considering the flow and heat transfer characteristics of sine wave channel combined with connecting oval tubes. The friction factor decreases as number of tube row increases. Comparison with round tube samples reveals that airside performance of oval fin-and-tube heat exchangers is generally superior except for one-row configuration.

Air-Side Heat-Transfer Enhancement by a New Winglet-Type Vortex Generator Array in a Plain-Fin Round-Tube Heat Exchanger

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
J. He ◽  
L. Liu ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Vortex Generator ◽  
Round Tube ◽  
Number Range ◽  
Tube Heat Exchanger ◽  
Large Pair ◽  
Goodness Factor ◽  
The Impact ◽  
Heat Transfer Improvement

The impact of a vortex-generation technique for air-side heat-transfer improvement is experimentally investigated through full-scale wind-tunnel testing of a plain-fin round-tube heat exchanger under dry-surface conditions. Inspired by the formation locomotion of animals in nature, a new vortex generator (VG) array deployed in a “V” is proposed in the present work, aiming to create constructive interference between vortices. The array is composed of two delta-winglet pairs and placed at an attack angle of 10 deg or 30 deg. Its effectiveness is compared with a baseline configuration and two conventional single-pair designs placed at 30 deg, a small pair with half the area of the array and a large pair with the same area as the array. The frontal air velocity considered ranges from 2.3 m/s to 5.5 m/s, corresponding to a Reynolds number range based on the hydraulic diameter of 1400–3400. The experimental results show little impact of the 10 deg array and a moderate heat-transfer improvement of up to 32% for the small pair, both introducing additional pressure loss of approximately 20–40%. For the 30 deg array and the large pair, similar augmentation of 25–55% in air-side heat-transfer coefficient is obtained accompanied by average pressure drop penalties of 90% and 140%, respectively. Performance evaluation using the criteria of the modified area goodness factor and the volume goodness factor indicates the superiority of the heat exchanger enhanced by the 30 deg array among all the investigated VGs. The VG array is found more effective at comparatively low Reynolds numbers, representative of many heating, ventilation, air-conditioning, and refrigeration applications and compact heat-exchanger designs.

Endwall Heat Transfer Enhancement Around Cylinders With a Wall-Mounted Vortex Generator Pair

2017 ◽  
Author(s):  
Safeer Hussain ◽  
Jian Liu ◽  
Lei Wang ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Vortex Generator ◽  
Diameter Ratio ◽  
Upstream Region ◽  
Spanwise Direction ◽  
Transfer Enhancement ◽  
Nusselt Numbers

Measurement of endwall heat transfer around a circular cylinder with a vortex generator pair has been investigated. Steady state liquid crystal thermography is adopted. Cylinders having two different height to diameter ratios have been employed. In one case, the cylinder has one end free in the flow and in the other case it has both ends attached on the walls. Local Nusselt numbers both upstream and downstream of the cylinder with and without the vortex generator pair are calculated. Nusselt numbers in streamwise and spanwise directions for both cases with vortex generator are compared with each other as well as with corresponding base cases. It is found from the experiments that the vortex generator influences the endwall heat transfer significantly downstream of the cylinder but has a small effect in the upstream region. Moreover, for different height to diameter ratio of the cylinder different heat transfer patterns are observed downstream of the cylinder. The vortex generator pair plays its major role on the endwall heat transfer enhancement in the spanwise direction and it expands as one moves from the upstream to downstream direction. To fully understand the advantage of the vortex generator pair, thermal performance is calculated for each case and it was found that in presence of the vortex generator pair, the cylinder with shorter height to diameter ratio shows higher thermal performance. Reynolds number dependence has also been investigated and it was found that the thermal performance decreases with increasing Reynolds number for both cases having a vortex generator pair.

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