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Research Papers

Computational Analysis of a Pipe Flow Distributor for a Thermocline Based Thermal Energy Storage System

[+] Author and Article Information
Samia Afrin

Department of Mechanical Engineering,
University of Texas at El Paso,
El Paso, TX 79968
e-mail: safrin@miners.utep.edu

Vinod Kumar

Department of Mechanical Engineering,
University of Texas at El Paso,
El Paso, TX 79968
e-mail: vkumar@utep.edu

Desikan Bharathan

Department of Mechanical Engineering,
University of Texas at El Paso,
El Paso, TX 79968
e-mail: desikan.bharathan@nrel.gov

Greg C. Glatzmaier

National Renewable Energy Laboratory,
Golden, CO 80401

e-mail: greg.glatzmair@nrel.gov

Zhiwen Ma

National Renewable Energy Laboratory,
Golden, CO 80401
e-mail: zhiwen.ma@nrel.com

Contributed by the Solar Energy Division of ASME for publication in the Journal of Solar Energy Engineering. Manuscript received August 15, 2012; final manuscript received May 1, 2013; published online September 16, 2013. Assoc. Editor: Rainer Tamme.

J. Sol. Energy Eng 136(2), 021010 (Sep 16, 2013) (6 pages) Paper No: SOL-12-1202; doi: 10.1115/1.4024927 History: Received August 15, 2012; Revised May 01, 2013

The overall efficiency of a concentrating solar power (CSP) plant depends on the effectiveness of thermal energy storage (TES) system (Kearney and Herrmann, 2002, “Assessment of a Molten Salt Heat Transfer Fluid,” ASME). A single tank TES system consists of a thermocline region which produces the temperature gradient between hot and cold storage fluid by density difference (Energy Efficiency and Renewable Energy, http://www.eere.energy.gov/basics/renewable_energy/thermal_storage.html). Preservation of this thermocline region in the tank during charging and discharging cycles depends on the uniformity of the velocity profile at any horizontal plane. Our objective is to maximize the uniformity of the velocity distribution using a pipe-network distributor by varying the number of holes, distance between the holes, position of the holes and number of distributor pipes. For simplicity, we consider that the diameter of the inlet, main pipe, the distributor pipes and the height and the width of the tank are constant. We use Hitec® molten salt as the storage medium and the commercial software Gambit 2.4.6 and Fluent 6.3 for the computational analysis. We analyze the standard deviation in the velocity field and compare the deviations at different positions of the tank height for different configurations. Since the distance of the holes from the inlet and their respective arrangements affects the flow distribution throughout the tank; we investigate the impacts of rearranging the holes position on flow distribution. Impact of the number of holes and distributor pipes are also analyzed. We analyze our findings to determine a configuration for the best case scenario.

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References

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Figures

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Fig. 1

Schematic diagram of a single tank thermocline TES system

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Fig. 2

Pipe flow distributor shown from the top

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Fig. 3

(a) Configuration 1 where holes positioned at the top near the inlet. (b) Configuration 2 where holes positioned at the bottom near the inlet.

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Fig. 4

Percentage velocity deviation versus height of the tank

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Fig. 5

Compare percentage velocity deviation with even volume elements touneven volume elements

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Fig. 6

Velocity contour along the vertical direction for the geometry of 7 distributor pipes with 140 holes. (a) Configuration 1 with 7 distributor pipes 140 holes. (b) Configuration 2 with 7 distributor pipes 140 holes.

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Fig. 7

Percentage velocity deviation versus height of the tank

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Fig 8

Velocity contour along the vertical direction (a) 7 distributor pipes with 140 holes and (b) 6 distributor pipes with 104 holes

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Fig. 9

Velocity contour at the middle of the tank in horizontal direction (a) 7 distributor pipes with 140 holes, (b) 6 distributor pipes with 104 holes

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