An experimental study of heat transfer to turbulent separation fluid flow in an annular passage

Togun, Hussein; Salman, Yasin K.; Aljibori, Hakim S. Sultan; Kazi, S.N.

doi:10.1016/j.ijheatmasstransfer.2010.10.031

Cited by 27 publications

(10 citation statements)

References 13 publications

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“…Thermal physical properties of nanofluids such as thermal conductivity, specific heat, density and viscocity of nanofluids can be obtained by several suggested correlations. The thermal conductivity of TiO 2 nanofluids can be calculated using equation (4) [26]:…”

Section: Data Processingmentioning

confidence: 99%

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Numerical simulation of heat transfer to separation tio₂/water nanofluids flow in an asymmetric abrupt expansion

Oon

Yew

Chew

et al. 2015

EPJ Web of Conferences

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Abstract. Flow separation and reattachment of 0.2% TiO 2 nanofluid in an asymmetric abrupt expansion is studied in this paper. Such flows occur in various engineering and heat transfer applications. Computational fluid dynamics package (FLUENT) is used to investigate turbulent nanofluid flow in the horizontal doubletube heat exchanger. The meshing of this model consists of 43383 nodes and 74891 elements. Only a quarter of the annular pipe is developed and simulated as it has symmetrical geometry. Standard k-epsilon second order implicit, pressure based-solver equation is applied. Reynolds numbers between 17050 and 44545, step height ratio of 1 and 1.82 and constant heat flux of 49050 W/m 2 was utilized in the simulation. Water was used as a working fluid to benchmark the study of the heat transfer enhancement in this case. Numerical simulation results show that the increase in the Reynolds number increases the heat transfer coefficient and Nusselt number of the flowing fluid. Moreover, the surface temperature will drop to its lowest value after the expansion and then gradually increase along the pipe. Finally, the chaotic movement and higher thermal conductivity of the TiO 2 nanoparticles have contributed to the overall heat transfer enhancement of the nanofluid compare to the water.

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Section: Data Processingmentioning

confidence: 99%

“…One of the reasons is due to the thermal conductivity of metal and metal oxide particles exhibits much higher thermal conductivity than those of the basefluids [4,5]. However, due to the weak stability of microfluids (the mixing of micro size particle with basefluid), their applications have not been feasible over the past decade.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of heat transfer to separation tio₂/water nanofluids flow in an asymmetric abrupt expansion

Oon

Yew

Chew

et al. 2015

EPJ Web of Conferences

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“…During the last decades there are many experimental and numerical studies concerned thermal performance using different geometries and types of fluids. A good example for thermal performance could be found at fluid flow over single or double forward-facing step [3][4][5][6], over single-double backward-facing step [7][8][9][10], through the sudden expansion [11][12][13], and through the sudden contraction [14,15]. The results obtained indicated that thermal performance increases of step height, Reynolds number, and volume fraction of nanofluids.…”

Section: Introductionmentioning

confidence: 99%

“…An enhancement of local heat transfer coefficient was observed with the increase of the wall angle of annular diffusers. In addition, Togun et al [12] experimentally studied the heat transfer to air flow in sudden expansion for a concentric annular pipe with a heated outer pipe heated, and they observed an increase of the local heat transfer coefficient by increase of the step height, the Reynolds number and the heat flux.…”

Section: Introductionmentioning

confidence: 99%

Augmented of turbulent heat transfer in an annular pipe with abrupt expansion

et al. 2016

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This paper presents a study of heat transfer to turbulent air flow in the abrupt axisymmetric expansion of an annular pipe. The experimental investigations were performed in the Reynolds number range from 5000 to 30000, the heat flux varied from 1000 to 4000 W/m 2 , and the expansion ratio was maintained at D/d=1, 1.25, 1.67, and 2. The sudden expansion was created by changing the inner diameter of the entrance pipe to an annular passage. The outer diameter of the inner pipe and the inner diameter of the outer pipe are 2.5 and 10 cm, respectively, where both of the pipes are subjected to uniform heat flux. The distribution of the surface temperature of the test pipe and the local Nusselt number are presented in this investigation. Due to sudden expansion in the cross-section of the annular pipe, a separation flow was created, which enhanced the heat transfer. The reduction of the surface temperature on the outer and inner pipes increased with the increase of the expansion ratio and the Reynolds number, and increased with the decrease of the heat flux to the annular pipe. The peak of the local Nusselt number was between 1.64 and 1.7 of the outer and inner pipes for Reynolds numbers varied from 5000 to 30000, and the increase of the local Nusselt number represented the augmentation of the heat transfer rate in the sudden expansion of the annular pipe. This research also showed a maximum heat transfer enhancement of 63-78% for the outer and inner pipes at an expansion ratio of D/d = 2 at a Re = 30000 and a heat flux of 4000 W/m 2 .

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“…Turbulent heat transfer and fluid flow through annular pipe with sudden expansion were experimentally and numerically studied by Togun et al (2011) and Oon et al (2012). The results showed that the highest enhancement of heat transfer was about 18 % at step height 18.5 mm compared to without step.…”

Section: Introductionmentioning

confidence: 99%

Laminar CuO–water nano-fluid flow and heat transfer in a backward-facing step with and without obstacle

Togun

2015

Appl Nanosci

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This paper presents a numerical investigate on CuO-water nano-fluid and heat transfer in a backwardfacing step with and without obstacle. The range of Reynolds number varied from 75 to 225 with volume fraction on CuO nanoparticles varied from 1 to 4 % at constant heat flux was investigated. Continuity, momentum, and energy equations with finite volume method in two dimensions were employed. Four different configurations of backwardfacing step (without obstacle, with obstacle of 1.5 mm, with obstacle of 3 mm, with obstacle of 4.5 mm) were considered to find the best thermal performance. The results show that the maximum augmentation in heat transfer was about 22 % for backward-facing step with obstacle of 4.5 mm and using CuO nanoparticles at Reynolds number of 225 compared with backward-facing step without obstacle. It is also observed that increase in size of recirculation region with increase of height obstacle on the channel wall has remarkable effect on thermal performance. The results also found that increases in Reynolds number, height obstacle, and volume fractions of CuO nanoparticles lead to increase of pressure drop.

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An experimental study of heat transfer to turbulent separation fluid flow in an annular passage

Cited by 27 publications

References 13 publications

Numerical simulation of heat transfer to separation tio₂/water nanofluids flow in an asymmetric abrupt expansion

Numerical simulation of heat transfer to separation tio₂/water nanofluids flow in an asymmetric abrupt expansion

Augmented of turbulent heat transfer in an annular pipe with abrupt expansion

Laminar CuO–water nano-fluid flow and heat transfer in a backward-facing step with and without obstacle

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An experimental study of heat transfer to turbulent separation fluid flow in an annular passage

Cited by 27 publications

References 13 publications

Numerical simulation of heat transfer to separation tio2/water nanofluids flow in an asymmetric abrupt expansion

Numerical simulation of heat transfer to separation tio2/water nanofluids flow in an asymmetric abrupt expansion

Augmented of turbulent heat transfer in an annular pipe with abrupt expansion

Laminar CuO–water nano-fluid flow and heat transfer in a backward-facing step with and without obstacle

Contact Info

Product

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Numerical simulation of heat transfer to separation tio₂/water nanofluids flow in an asymmetric abrupt expansion

Numerical simulation of heat transfer to separation tio₂/water nanofluids flow in an asymmetric abrupt expansion