Numerical Investigation for the Discharging Process in

Journal of Mechanical Engineering Research and Developments

ISSN: 1024-1752

CODEN: JERDFO

Vol. 43, No. 5, pp. 295-306

Published Year 2020

295

Numerical Investigation for the Discharging Process in Cold-

Water Storage Tank

Hayder Abed Dhahad†, Wissam H. Alaweea‡, Laith Jaafer Habeeb‡†

†Mechanical Engineering Department, University of Technology, Baghdad, Iraq ‡Control and Systems Engineering Department, University of Technology, Baghdad, Iraq

‡†Training and Workshops Center, University of Technology, Baghdad, Iraq

*Corresponding Author Email: [email protected]

ABSTRACT: Thermal Energy Storage technology is used typically in industries and buildings for the thermal

energy reservation in order that the stored energy can be used later. Numerical analysis was performed to study

the thermal energy storage tank using Ansys CFX. In this paper, the unsteady discharging process was studied

with two values of water flow rate. The model was simulated with two diffusers at the top and the bottom of the

tank. The point of this research was to reduce the turbulence in the tank and the thermocline thickness. Results

indicated that the thermal stratification improves with low inlet velocity, and high temperature difference, while

the storage mixing increases by enlarging the inlet water flow rate. Then again, the inlet flow rates can be

enlarged, without the increase of the mixing, beyond the thermocline has been formed. Again, thermoclines can

be formed between the high temperature differences and varied with the variation in flow rate. In addition, large

thermocline thickness between the water layers stored in the tank and the inlet water reduces the mixing due to

the high difference in the density between the layers also high inlet water velocity results in increasing the

mixing of water.

KEYWORDS: Thermocline, Cold water storage tank, Discharge process, Temperature distribution

INTRODUCTION

Cooling and Heating systems are essential within the environments of building to preserve the comfortable

thermal conditions for the inhabitants of office and commercial buildings, which use gravitational stratification

to maintain cold and hot water, they are widely used for energy conservation and load management applications.

Ventilating, traditional heating, cooling and air-conditioning systems being substance to large expenses and

participate in the demand peak. Most daytime operating regimes are contributed to the peak demand. The

electricity load in daytime peak is in the extreme excess comparison with the average load per day. To encounter

this demand, larger capacities are required from the utility companies, which end up unused for most times. The

obligation to meet the demand peak ultimately is met either by purchasing power from competitors or by

constructing new generation facilities, both choices causes higher rates for customer. The storage of thermal

energy storage is a progressive technique for generating the cooling as well as heating energy within the off-

peak hours and provides to the buildings through the peak hours and consequently moves the electricity demand

to the off-peak hours. By Thermal energy storage, the systems of cooling and heating are operating mostly at

night (off-peak periods) for storing the essential energy inside storage tanks. Throughout peak demands, the

energy of cooling/heating is provided from storage tanks without operating chillers and heaters. Efficiency of

the thermal storage tank is highly affected by thermal stratification [1-3]. The single stratified tank due to its low

cost and simplicity is attractive in medium to low temperature applications. Performance of the solar collector

increases with the decreases in the collector inlet temperature, because of the reduction in the heat loss by

convection from the plate of collector. Though, a hotter temperature is needed for the storage tank so as to fulfill

the various energy demands, like the uses of hot water, air cooling, and heating of space. At the tank top inlet

port, the heated water from the collector is discharged leading to a rise in the thermal stratification due to the

variation in the temperature, by that increases the medium density variation. Consequently, the hot water and

cold water are parted via the gravitational influence; the middle area is named thermocline. The storage tank

efficiency enlarged when the difference in temperature between the bottom and top is large. The efficiency of

storage can be enhanced via preserving an active stratification in fluid [2-5]. One or more thermal plants are

composed to make the heating systems with a scattering network of insulated pipes where the steam,

superheated water, or hot flow of water providing the heat to users by heat exchangers. Thermal plants

mailto:[email protected]

Numerical Investigation for the Discharging Process in Cold-Water Storage Tank

296

sometimes comprise large boilers and a combination of power and units of heat. The other formations are likely,

like geothermal sources, heat pumps, solar panels, and biomass boilers, convert waste to energy systems, also

industrial waste heat recovery systems [6]. The generation solar thermal power is a recent system that has

already present viable outcomes in the production of electricity. For the applications of solar energy, the storage

of thermal energy is a vital part, which includes electricity generation from Concentrated Solar Thermal power

plants, domestic use solar water heating systems, and building thermal capacity increasing. Economic, reliable

and efficient storage systems of thermal energy are a crucial requirement of the solar thermal power plants. The

efficiency of thermal energy storage and solar collector systems is improved if the water tank is stratified.

Thermal stratification is slowly applied to appropriately use and store high-quality heat energy in many types of

energy storage systems for instance solar thermal utilization system. Thermal storage becomes very important

due to the unsteady features of solar radiation in a heating load long-term operation [7-11]. Finally, because of

their low cost of maintenance and production, the feasibility are sized as well as designed to the smallest likely

volume [11]. When water gets heated up, the stratification is found due to the density difference. Under a highly

optimal stratification condition, the hot water must be withdrawal, supplied, or filled from the top of the storage

tank, whereas the cold water must be preserved at the bottom. Thermal stratification disturbs due to the hot

water filling from the top or top side of the tank. Thermal stratification disturbance leads to a blending of hot

and cold water and later, the potential of thermal energy storage grows affected [12]. A computational fluid

dynamics model has been developed to simulate the heat transfer and flow in a cylindrical chilled stratified

water storage tank with radial diffusers during discharging and charging [13-16], the model was utilized to

simulate the tank in full scale with a validated computational fluid dynamics (CFD) model. The results showed

that the assumed inlet velocity distribution does not affect the temperature profile that is fully developed, and it

is valuable to use the laminar models for simulations. In addition to that, the discharge cycles performance is not

as good as the charge cycle performance at the same flow rate [13-16]. They also found that the temperature

distributions obtained from the finite volume model are found to be in very close agreement with those obtained

experimentally [16]. Recently, a new tendency is introduced for using an energy storage system with phase

change materials in some domestic solar water heating systems, which give several advantages, including low

storage volume, high storage capacity, isothermal operation during the discharging and charging phases, and

decrease the heat transfer fluid use, which is mostly expensive [17-20]. Phase change material thermal energy

storage devices are vital in the waste heat energy and solar thermal techniques matching the energy fund to the

request and improve their thermal efficiency. The phase change material thermal energy storage is higher

valuable than the storage of sensible energy due to its storage energy high density per unit volume/mass [21].

Thermal stratification heat storage water tank was studied with an inside cylinder and/ or device, this

modifications was accomplished with the purpose of improving the tank efficiency. Computational Fluid

Dynamics methods were used in the studies. Influence of the inner cylinder working parameters and design

upon the water flow characteristic was investigated as well as a heat pump to improve the design of thermal

energy storage tank [22-24]. It was concluded that the stratification level is affected by the inlet devices

modifications. One of the internal devices used is the dual heaters, according to the quantity of hot water

required; the operators can switch between them. This will facilitate the energy rational use in the preparation of

domestic hot water [25]. Effect of using different obstacles on the thermal stratification in a cylindrical hot

water tank was analyzed numerically [26]. The results indicated that placing an obstacle in the tank provides

better thermal stratification compared to the no obstacle case. Different shapes of storage tank were investigated

to study the influences of different water tank shapes on the thermal energy storage capacity and thermal

stratification in the static mode of operation. The sphere and barrel water tanks were found to be ideal for

thermal energy storage capacity, whereas the cylinder water tank is the least favorable [27, 28]. The solar

system efficiency high was leveled by a decent thermal stratification. Investigations were performed on a

horizontal storage tank both experimentally and numerically to enhance the process of thermal stratification [29-

31]. It was concluded that a suitable location for the inlet of hot water leads to better collector efficiency, and

better storage tank thermal stratification, which the two improved the solar water heater system efficiency. The

effect of specification of wall material on the de-stratification for hot water domestic tanks was studied

numerically and experimentally [32]. The studies manifested that by selecting an appropriate wall material, the

de-stratification is minimizing enhancing by that the performance of hot water tanks and enhancing the

opportunity of using them in the management applications demand side. The stainless steel usage in the walls of

hot water tank was advocates and more exploration of composites and substituted materials that possess both the

low thermal conductivity and cost beside the high manufacturability as well as strength [32]. Most of the

researches available now study the storage tanks as a thermal storage tank where the cold liquid is converted

into hot liquid, and in different climates, the storage tanks systems are more effective if they convert the hot


297

liquid into a cold one. This paper numerically studies the storage tank discharging process where the hot water is

converted into a cold water at 4⁰C to be used during the peak hours.

DEFINITION OF THERMOCLINE THICKNESS

The intermediate zone between the cold and hot water, where there is a huge gradient in the temperature in the

storage tank, is called the thermocline. It was determined to decrease the range of thermocline temperature by

each ‘10% x △T’ within a warm/cold temperature range. Figure (1) illustrates the determination of the

thermocline.

△T = Warm water T – Cold water T

Figure 1: Thermocline determination

NUMERICAL STUDY

Analysis

A better stratification can be made sure with a suitable tank design, appropriate governing of the discrepancies

of temperature, keeping the inlet velocity and of the cold water from the tank’s bottom. When these being made

sure, the mechanical disturbances will be least and the discrepancies of density should make a vertical

temperature gradient zone, named the thermocline that splits the cold and warm waters. The higher temperature

of water is inserted from the tank’s top through the cycle of discharge and the cold water from the tank’s bottom

through the cycle of charging. In the present work, the blending and the thermocline behaviors of (TES) were

studied for the variations in the inlet velocity (inlet from top diffuser of hot water), and the difference of

temperature between the inlet water and the stored water.

MODELLING AND SIMULATION

The storage tank modelling and simulation were directed utilizing SolidWorks and ANSYS-CFX. The tank

geometry was constructed as a three-dimensional geometry using CAD software, figure (2) shows the schematic

drawing in SolidWorks and the dimensions of the tank, the geometry of tank studied is simple and has a

cylindrical shape. A small size of element was set around the inlet and outlet of tank to increase the accuracy of

the mesh. Initially, the mesh size was set to the ANSYS default meshing; it was found that the result is not

accurate since a non-uniform thermocline temperature was established. It was presumed that to attain better

results, it is better to increase the number of elements for the mesh. By that, an extra element for the meshing

formations was added. With the size of mesh that was used for the storage tank and diffusers; for the storage

tank, (1500708) elements were generated and (2110099) nodes, and for the diffuser, (515803) elements were

generated and (747450) nodes. Figure (3) elucidates the meshing for the storage tank system and the diffusers.


298

Figure 2: The dimensions of tank

Figure 3: Mesh element size

The boundary conditions that affect the system and the influence on the simulation of model are the conditions

at the inlet and outlet of tank as well as the wall the tank [1]. The physical model boundary conditions are:


299

• 3D Axisymmetric

• Boussinesq model

• Gravity

• Implicit unsteady

• Segregated Flow Temperature

The simulation is considered to be transient due to the heat transfer with time and the discharging water

characteristics. The CFD model was run as a 3D-axisymmetric model. The storage tank was filled with water

being flowed and distributed through the diffusers at the inlet and outlet of tank, the diffuser was used to avoid

mixing the hot and the cold water. The inlet boundary condition was assigned as inlet velocity; the outlet

boundary condition was applied as outlet pressure. The hot water flows with a velocity Vin into the top of tank

through an inlet pipe din and inlet diffuser, the cold water leaves the tank with a velocity Vout from the bottom of

tank through an outlet pipe and diffuser. The temperature of hot water entering into the tank is 18oC, while the

temperature of cold water discharging from the tank is 9oC. The outlet pressure was set as zero at the outlet

boundary condition. The walls of the storage tank were given an adiabatic thermal condition by setting the wall

surface as zero heat flux. All the solid surface walls were imposed as No-slip condition; that means the fluid

velocity is zero at the wall.

The operating conditions used for the discharging process that was investigated in this paper are listed in Table

(1). The properties of water at the inlet and outlet are given in Table (2).

Table 1: Operating conditions

Upper diffuser Diameter (d)

Large d= 3.6 m

Small d= 1.8 m

Height (h) 0.35 m

Lower diffuser Diameter (d)

Large d= 3.6 m

Small d= 1.8 m

Height (h) 0.35 m

Inlet Temperature 18oC

Initial Temperature 9oC

Mass flow 98.37 (L/s)

109.3 L/sec

Table 2: Water properties

Water properties Cold water (Tc)

9oC

Warm water (Tw)

18oC

Density (kg/m3) 999.781 998.594

Dynamic viscosity (Pa-s) 0.00134436 0.001052669

Specific heat (kJ/kg-K) 4.197 4.186

Thermal conductivity (W/m-K) 0.5781588 0.594864


300

Thermal expansion coefficient (1/K) 0.003544 0.003436

The governing transport expressions for the continuity, the momentum and the energy conservation for a fluid

are [1]:

- For continuity:

( ). 0ut

+ =

(1)

- For momentum:

( )( )

. . M

uu u S

t

+ = − + +

(2)

- For energy:

( )( )

. .( ) : M

hu h T u S

t

+ = + +

(3)

RESULTS AND DISCUSSION

This paper simulates the discharging process, which starts after completing the charging process. In this method,

cold water is discharged from the thermal energy storage tank, and the same amount of hot water at 18oC is fed

into the storage tank at the same time. CFD is concerned with obtaining a numerical solution to the fluid flow

problems by using computers [18]. Modeling of water density was made. It states that the difference in the

density is small sufficiently to be neglected, it performs in terms multiplied by the acceleration caused by

Gravitational acceleration (g). So, the density was evaluated only in momentum equations in the simulation of

discharge process. Figure (4) manifests a transient dimensionless temperature distribution profile of tank

through the discharging process. Because of the high momentum energy of the inlet flow, the inlet hot water

results a blending flow upon the upper layers and diffuses inside the tank, which affects the structure of flow in

the tank. As the time increases, the hot water starts to cover the inter duct reducing by that the cold water. The

thickness of the thermocline layer should be as small as possible. The chilled-water storage system stratification

decay is measured by the thermocline thickness enlargement with time, which results a losing in the capacity of

cooling.

(a) 4 min (b) 8 min


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(c) 12 min (d) 15 min

Figure 4: The temperature profile distribution demonstrates the temperature profile for the storage tank.

The temperature distribution graphic representation was analyzed in order to measure the stratification degree

among the several cases that were simulated in this study. Thermocline was also studied and analyzed from the

cases that were simulated, and the thermocline thickness with time was calculated. The thermocline thickness

increases as the time increases. The thermocline thickness enlarges mostly due to the conduction of heat over

time. In the meantime, the turbulence effect weakens; enlarging the water flow rate increases the thermocline

thickness, as displayed in figures (5) and (6). The Reynolds number enlarges by increasing the water flow rate,

which increases the thermocline thickness, as shown in figure (6). Small temperature difference reduces the

thermocline thickness, therefore, the thermal energy storage tanks is regularly designed for the chilled water

storage, which is aimed to reduce the pressure of the tank bottom by reducing the consumption of material [24].

Figures (5) and (6) also present the comparison of the temperature profiles for the three locations used in this

paper at a total flow rate of 98.37 L/sec and 109.3 L/sec, respectively, during a three-time interval through the

discharging mode. It can be noted that over a period of time, the outlet flow temperature raised quickly at the

high flow rates values, meanwhile for the lower values of flow rate, there is a gradual increase in the

temperature of the top layers until it reaches the steady state conditions.

(a) 5 min


302

(b) 10 min

(c) 15 min

Figure 5: Temperature distribution through the height of the tank at a total flow rate = 98.37 L/sec

(a) 5 min

(b) 10 min


303

(c) 15 min

Figure 6: Temperature distribution through the height of the tank at a total flow rate = 109.3 L/sec

The temperature difference in the upper and lower parts of the tank decreases as the time increases. Meanwhile,

as the diameter of the tank increases, the temperature difference between the top and bottom of tank is enlarged.

The water temperature reduced, and the drops in the area close to the bottom of the tank surface are due to the

heat that transfers from the walls of the tank and the density difference among the cold and hot water. After

simulating a range of water flow rates, it was concluded that even at large flow rates values, a steady thermal

performance is detected, and no blending happens, particularly at the storage tank top area. Also, such outcomes

verified those obtained in literature.

Figure (7) illustrates the velocity vectors performed during different times through the simulations. The arose of

the velocity boundary layer for the all conditions was on the tank walls, meanwhile the circulation of water

meanly happened on the top part of the storage tank. As the circulation of water increases, the cold and hot

water mixture in the tank increases as well, and this results in a decrease in the tank thermal stratification. The

water movement in the tank was found to be increased as the diameter of the tank was increased, by that, the

motion of the water in the tank area close to the bottom was found to be decreasing, figure (7). The thermal

stratification increased as the movement of water in the storage tank was reduced banning by the blending of hot

and cold water. Furthermore, the thermal stratification improved by enlarging the tank diameter which banning

the boundary layer of velocity from reaching the bottom area of tank.

(a) 4 min (b) 8 min


304

(c) 12 min (d) 15 min

Figure 7: Velocity vectors

CONCLUSIONS

This article conducted a numerical simulation based on the transient due to the heat transfer with time and the

discharging water characteristics. Depending on the obtained results, the followings are concluded:

1- Thermoclines can be formed between the high temperature differences and varied with the variation in flow

rate.

2- Large thermocline thickness between the water layers stored in the tank and the inlet water reduces the

mixing due to the high difference in the density between the layers.

3- High inlet water velocity results in increasing the mixing of water.

REFERENCES

[1] A. Karim, A. Burnett and S. Fawzia, “Investigation of Stratified Thermal Storage Tank Performance for

Heating and Cooling Applications”, Engineers, 11, Pp. 1-15, 2018.

[2] W. Yaïci, M. Ghorab, E. Entchev, and S. Hayden, “Three-dimensional unsteady CFD simulations of a

thermal storage tank performance for optimum design”, Applied Thermal Engineering, 60, Pp. 152-163,

2013.

[3] V.K. Reddy, M. Mastanaiah, and S.R.K. Reddy, “Experimental Analysis of Partial and Fully Charged

thermal Stratified Hot Water Storage Tanks”, International Journal of Mechanical Engineering and

Technology, Vol. 6, No. 2, Pp. 62-69, 2015.

[4] P. Li, J.V. Lew, C. Chan, W. Karaki, J. Stephens, and J.E. O’Brien, “Similarity and generalized analysis of

efficiencies of thermal energy storage Systems”, Renewable Energy, 39, Pp. 388-402, 2012.

[5] A. Pizzolato, F. Donato, V. Verda, and M. Santarelli, “CFD-based reduced model for the simulation of

thermocline thermal energy storage systems”, Applied Thermal Engineering, 76, Pp. 391-399, 2015.

[6] V. Verda and F. Colella, “Primary energy savings through thermal storage in district heating networks”,

Energy, 36, Pp. 4278-4286, 2011.

[7] A. Castell, M. Medrano, C. Solé, and L.F. Cabeza, “Dimensionless numbers used to characterize

stratification in water tanks for discharging at low flow rates”, Renewable Energy, 35, Pp. 2192-2199,

2010.


305

[8] E. Andersen, S. Furbo, M. Hampel, W. Heidemann, and H. Muller-Steinhagen, “Investigations on

stratification devices for hot water heat stores”, International Journal of Energy Research, 32, Pp. 255–

263, 2008.

[9] Y.M. Han, R.Z. Wang, and Y.J. Dai, “Thermal stratification within the water tank”, Renewable and

Sustainable Energy Reviews, 13, Pp. 1014–1026, 2009.

[10] S. Pintaldi, C. Perfumo, S. Sethuvenkatraman, S. White, and G. Rosengarten, “A review of thermal energy

storage technologies and control Approaches for solar cooling”, Renewable and Sustainable Energy

Reviews, 41, Pp. 975–995, 2015.

[11] M. Tesfay and M. Venkatesan, “Simulation of thermocline thermal energy storage system using C”,

International Journal of Innovation and Applied Studies, Vol. 3, No. 2, Pp. 354-364, 2013.

[12] M. Bhaumik, “CFD simulation of inlet position of hot water into SDHW thermal storage tank”,

International Journal of Engineering and Technical Research (IJETR), Vol. 2, No. 4, Pp. 64-67, 2014.

[13] A. Musser, and W.P. Bahnfleth, “Parametric Study of Charging Inlet Diffuser Performance in Stratified

Chilled Water Storage Tanks with Radial Diffusers: Part 1–Model Development and Validation”, HVAC &

R Research, Vol. 7, No. 1 (2001), Pp. 31-50, 2001.

[14] W.P. Bahnfleth, and A. Musser, “Thermal Performance of a Full-Scale Stratified Chilled-Water Thermal

Storage Tank”, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Vol. 104,

1998.

[15] J. Song, W.P. Bahnfleth, and J.M. Cimbala, “Parametric Study of Single-Pipe Diffusers in Stratified

Chilled Water Storage Tanks (RP-1185)”, HVAC&R Research, Vol. 10, No. 3, Pp. 345-365, 2004.

[16] F.M. Hasan, and M.A. Theeb, “Experimental and Numerical Study of Heat Transfer Process of Chilled

Water Storage Tank”, Universal Journal of Mechanical Engineering, Vol. 6, No. 4 (2018) , Pp. 63-75,

2018.

[17] B. Xu, P. Li, C. Chan, and E. Tumilowicz, “General volume sizing strategy for thermal storage system for

concentrated solar thermal power plant”, Applied Energy, 140, Pp. 256–268, 2015.

[18] G.C. Naidu, K. Aruna, K.D. Reddy, and P.V. Ramaiah, “CFD Simulation for Charging and Discharging

Process of Thermal Energy Storage System using Phase Change Material”, International Journal of

Engineering Research, Vol. No.5, Pp. 332-339, 2016.

[19] P. Verma, Varun, and S.K. Singal, “Review of mathematical modeling on latent heat thermal energy

storage systems using phase change material”, Renewable and Sustainable Energy Reviews, 12, Pp. 999–

1031, 2008.

[20] M.H. Abokersh, M. Osman, O. El-Baz, M. El-Morsi, and O. Sharaf, “Review of the phase change material

(PCM) usage for solar domestic water heating systems (SDWHS)”, International Journal of Energy

Research, Pp. 42, Pp. 329–357, 2018.

[21] M.K.A. Sharif, A.A. Al-Abidi, S. Mat, K. Sopian, M.H. Ruslan, M.Y. Sulaiman, and M.A.M. Rosli,

“Review of the application of phase change material for heating and domestic hot water systems”,

Renewable and Sustainable Energy Reviews, 42, Pp. 557–568, 2015.

[22] I.J. Moncho-Esteve, M. Gasque, P. Gonz´alez-Altozano, and G. Palau-Salvador, “Simple inlet devices and

their influence on thermal stratification in a hot water storage tank”, Energy and Buildings,

http://dx.doi.org/10.1016/j.enbuild.2017.06.012.

[23] L. Kong, W. Yuan, and N. Zhu, “CFD simulations of thermal stratification heat storage water tank with an

inside cylinder with openings”, Procedia Engineering, 146, Pp. 394 – 399, 2016.

[24] J. Sun, J. Hua, L. Fu, and S. Zhang, “Experimental Study of a Large Temperature Difference Thermal

Energy Storage Tank for Centeralized Heating Systems”, Thermal Science, Vol. 22, No. 1B, Pp. 613-621,

2018.

http://dx.doi.org/10.1016/j.enbuild.2017.06.012


306

[25] I. Sezai, L.B.Y. Aldabbagh, U. Atikol, and H. Hacisevki, “Performance improvement by using dual heaters

in a storage-type domestic electric water-heater”, Applied Energy, 81, Pp. 291–305, 2005.

[26] N. Altuntop, M. Arslan, V. Ozceyhan, and M. Kanoglu, “Effect of obstacles on thermal stratification in hot

water storage tanks”, Applied Thermal Engineering, Vol. 25, Pp. 2285–2298, 2005.

[27] B. Kurşun, “Thermal stratification enhancement in cylindrical and rectangular hot water tanks with

truncated cone and pyramid shaped insulation geometry”, Solar Energy, 169, Pp. 512–525, 2018.

[28] Z. Yang, H. Chen, L. Wang, Y. Sheng, and Y. Wang, “Comparative study of the influences of different

water tank shapes on thermal energy storage capacity and thermal stratification”, Renewable Energy, 85,

Pp. 31-44, 2016.

[29] M.R. Assari, H.B. Tabrizi, and M. Savadkohy, “Numerical and experimental study of inlet-outlet locations

effect in horizontal storage tank of solar water heater”, Sustainable Energy Technologies and Assessments,

Vol. 25, Pp. 181–190.

[30] D.L. Savicki, H.A. Vielmo, and A. Krenzinger, “Three-dimensional analysis and investigation of the

thermal and hydrodynamic behaviors of cylindrical storage tanks”, Renewable Energy, Vol. 36, Pp. 1364-

1373, 2011.

[31] B. Kurşun, and K. Ökten, “Effect of rectangular hot water tank position and aspect ratio on thermal

stratification enhancement”, Renewable Energy, 2017, doi: 10.1016/j.renene.2017.10.013.

[32] P. Armstrong, D. Ager, I. Thompson, and M. McCulloch, “Improving the energy storage capability of hot

water tanks through wall material specification”, Energy, 78, Pp. 128-140, 2014.

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Numerical Investigation for the Discharging Process in