Simple inlet devices and their influence on thermal stratification in a hot water storage tank

Moncho-Esteve, Ignacio José; Gasque, Marı́a; González-Altozano, Pablo; Palau-Salvador, Guillermo

doi:10.1016/j.enbuild.2017.06.012

Cited by 55 publications

(17 citation statements)

References 45 publications

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“…Among the more recent numerical studies, Bouhal et al [9] performed 2D-CFD simulations to assess the thermal stratification in an HWST and the impact of flate plates position within a tank. Moncho-Esteve et al [10] implemented a 3D-CFD model to study the flow field and thermal stratification during charging. Once validated, the model was used to accomplish slight modifications of the inlet devices with the intention of optimizing system efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…The study is completed with a comparison between the VTC method when using fewer measurement points and a numerical 3D-CFD approach, previously developed and validated in [10] with the same storage tank and experimental tests. Specifically, a comparison is made between the results obtained with the two methods when applied to the estimation of the instantaneous temperature profile.…”

Section: Introductionmentioning

confidence: 99%

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Minimum Number of Experimental Data for the Thermal Characterization of a Hot Water Storage Tank

2021

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This paper demonstrates that it is possible to characterize the water temperature profile and its temporal trend in a hot water storage tank during the thermal charge process, using a minimum number of thermocouples (TC), with minor differences compared to experimental data. Four experimental tests (two types of inlet and two water flow rates) were conducted in a 950 L capacity tank. For each experimental test (with 12 TC), four models were developed using a decreasing number of TC (7, 4, 3 and 2, respectively). The results of the estimation of water temperature obtained with each of the four models were compared with those of a fifth model performed with 12 TC. All models were tested for constant inlet temperature. Very acceptable results were achieved (RMSE between 0.2065 °C and 0.8706 °C in models with 3 TC). The models were also useful to estimate the water temperature profile and the evolution of thermocline thickness even with only 3 TC (RMSE between 0.00247 °C and 0.00292 °C). A comparison with a CFD model was carried out to complete the study with very small differences between both approaches when applied to the estimation of the instantaneous temperature profile. The proposed methodology has proven to be very effective in estimating several of the temperature-based indices commonly employed to evaluate thermal stratification in water storage tanks, with only two or three experimental temperature data measurements. It can also be used as a complementary tool to other techniques such as the validation of numerical simulations or in cases where only a few experimental temperature values are available.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Minimum Number of Experimental Data for the Thermal Characterization of a Hot Water Storage Tank

2021

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“…In the aspect of tank thermal stratification during DHW discharge, Castell et al [6] studied the suitability of the most used dimensionless numbers for characterizing stratification in water tanks and found that Richardson number was the best number to define stratification in a water tank, while Mix number presented some problems and a bad behavior. As to the inlet effect, Moncho-Esteve et al [7] analyzed the influence of simple inlet devices on the thermal stratification of a cylindrical hot water storage tank by CFD techniques and reported that a sintered bronze conical diffuser could improve stratification compared to a conventional bronze elbow inlet.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Thermal performance assessment and improvement of a solar domestic hot water tank with PCM in the mantle

Deng

Furbo

Kong

et al. 2018

Energy and Buildings

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“…Turbulence and mixing created by inlet flow affect considerably thermal stratification, for this reason a lot of researchers have investigated various inlet designs and their effect on stratification. A sintered bronze conical diffuser is considered to favor stratification for both low and high flows (García-Marí et al, 2013;Moncho-Esteve et al, 2017). Others suggest that a divergent conical tube diffuser creates better thermal stratification due to better diffusion of water (Alizadeh, 1999).…”

Section: Introductionmentioning

confidence: 99%

Optimization of the coefficient of performance of a heat pump with an integrated storage tank – A computational fluid dynamics study

Sifnaios¹,

Fan²,

Olsen

et al. 2019

Applied Thermal Engineering

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The performance of a heating system consisting of a heat pump with an integrated storage tank was evaluated by means of Computational Fluid Dynamics (CFD) calculations. The aim of the investigations was to elucidate how thermal stratification in the tank would influence the COP of the system. Differently designed storage tanks were investigated under typical operation conditions. CFD models of heat storage tanks were developed and validated by experiments on a test tank. Calculations with the validated models were carried out in order to find the optimal tank design and system settings for achieving the highest possible COP. The investigated parameters were volume flow rate, tank geometry, diffuser design and tank wall material. Two different system COPs were defined: one based only on charge operation and the other on both charge and discharge operations. It was found that there is a direct connection between the thermal stratification inside the tank and the COP of the heating system. Higher degree of stratification leads to higher COP. For the ideal case where there is no mixing and no vertical thermal conduction in the tank and no heat loss from the tank, the system COP after a charge-discharge cycle is 3.69. When the effect of mixing is taken into account, the obtained COP of the system is decreased by approximately 9%. If heat transfer to the tank wall and vertical thermal conduction are also taken into account, the obtained system COP is lowered by another 5%. Moreover, the COP of a heating system with high flow rates can be significantly increased by a diffuser plate installed in the tank with a small distance to the inlet/outlet. The best performing system studied consisted of an insulated tall and slim tank with a h/d ratio of 3.64 and a perforated plate diffuser, giving a COP of 3.23 which was 32% higher compared to a case without a diffuser. The performance of the suggested system was not affected by variations of flow rates in the range from 0.12 to 0.24 kg/s.

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Simple inlet devices and their influence on thermal stratification in a hot water storage tank

Cited by 55 publications

References 45 publications

Minimum Number of Experimental Data for the Thermal Characterization of a Hot Water Storage Tank

Minimum Number of Experimental Data for the Thermal Characterization of a Hot Water Storage Tank

Thermal performance assessment and improvement of a solar domestic hot water tank with PCM in the mantle

Optimization of the coefficient of performance of a heat pump with an integrated storage tank – A computational fluid dynamics study

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