Experimental and Numerical Study of Mixing in a Hot-Water Storage Tank

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
A. Aviv ◽  
Y. Blyakhman ◽  
O. Beeri ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Numerical Model ◽  
Storage Tank ◽  
Numerical Study ◽  
Tap Water ◽  
Three Dimensional ◽  
Hot Water ◽  
Software Validation ◽  
Water Storage Tank ◽  
Thermal Mixing ◽  
Numerical Investigations

Thermal mixing and stratification are explored numerically and experimentally in a cylindrical tank, which simulates a storage of water heated by a solar collector. The tank is 70cm in height and 24cm in diameter. The inlet and outlet are vertical and located off the centerline of the tank. The study is conducted in a transient mode, namely, the tank is filled with hot water, and as the hot water is being withdrawn, the tap water replaces it in a stratified way or by mixing. The flowrates of 2l∕min, 3l∕min, 5l∕min and 7l∕min, which correspond to superficial velocities of 4.35cm∕min, 6.52cm∕min, 10.87cm∕min, and 15.2cm∕min, are explored. Temperature of hot water ranges within 40–50°C, while the tap water is about 25–27°C. Installation of one and two horizontal baffles above the inlet is examined. Simultaneous experimental and numerical investigations are performed. In the experiment, both flow visualization and temperature measurements are used. Three-dimensional transient numerical simulations are done using the FLUENT 6 software. Validation of the numerical model is achieved by comparison with the experimental results. Then, the numerical model is applied to a study of various possible changes in the system. The results show that at low flowrates, up to a superficial velocity of about 11cm∕min through the tank, the baffles have no effect on tap water mixing with the stored hot water. At higher flowrates, a single horizontal baffle prevents the mixing and preserves the desired stratified temperature distribution in the storage tank.

Experimental and Numerical Study of Mixing in a Horizontal Hot-Water Storage Tank

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
A. Aviv ◽  
S. Morad ◽  
Y. Ratzon ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Numerical Study ◽  
Tap Water ◽  
Three Dimensional ◽  
Hot Water ◽  
Outlet Temperature ◽  
Dimensionless Time ◽  
Water Storage Tank ◽  
Thermal Mixing ◽  
Horizontal Cylindrical Tank ◽  
Port Location

Thermal mixing and stratification are explored experimentally in a horizontal cylindrical tank, which simulates a storage of water heated by a solar collector. The tank is 70 cm long and 24 cm in diameter. The study is conducted in a transient mode, namely, the tank is filled with hot water, which in the course of operation is replaced by the tap water in a stratified way or by mixing. The flow rates of 2 l/min, 3 l/min, 5 l/min, and 7 l/min are explored. Temperature of hot water is usually about 55°C, while the tap water is about 20°C. In the experiments, both flow visualization and temperature measurements are used. The effects of port location and deflector installation are examined. The experimental results are presented in a dimensionless form, as the normalized outlet temperature versus dimensionless time. Three-dimensional transient numerical simulations, done using the FLUENT 6 software, provide an additional insight in the process of mixing inside the tank.

Experimental and Numerical Study of Mixing in a Horizontal Hot-Water Storage Tank

2008 ◽  
Author(s):  
A. Aviv ◽  
S. Morad ◽  
Y. Ratzon ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Numerical Study ◽  
Tap Water ◽  
Three Dimensional ◽  
Hot Water ◽  
Outlet Temperature ◽  
Dimensionless Time ◽  
Water Storage Tank ◽  
Thermal Mixing ◽  
Horizontal Cylindrical Tank ◽  
Port Location

Thermal mixing and stratification are explored experimentally in a horizontal cylindrical tank, which simulates a storage of water heated by a solar collector. The tank is 70 cm long and 24 cm in diameter. The study is conducted in a transient mode, namely, the tank is filled with hot water, which in the course of operation is replaced by the tap water in a stratified way or by mixing. The flow rates of 2, 3, 5 and 7 liters per minute are explored. Temperature of hot water is usually about 55 °C, while the tap water is about 20 °C. In the experiments, both flow visualization and temperature measurements are used. The effects of port location and deflector installation are examined. The experimental results are presented in a dimensionless form, as the normalized outlet temperature vs. dimensionless time. Three-dimensional transient numerical simulations, done using the Fluent 6 software, provide an additional insight in the process of mixing inside the tank.

scholarly journals The impact of inflow velocity on thermal stratification in a water storage tank

2018 ◽  
Vol 44 ◽  
pp. 00079 ◽  
Author(s):  
Kamila Kozłowska ◽  
Piotr Jadwiszczak
Keyword(s):  
Storage Tank ◽  
Thermal Stratification ◽  
Heat Storage ◽  
Three Dimensional ◽  
Hot Water ◽  
Thermal Processes ◽  
Water Storage Tank ◽  
Thermal Mixing ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

The paper presents the analysis of thermal processes occurring in thermal energy storage tanks used for heating hot water systems. Three-dimensional Computational Fluid Dynamics (CFD) methods were used. The standard buffer charging stage was modelled for three tank inlets’ diameters DN20, DN40 and DN80. With a constant charging water flow and temperature the port diameter affects inlet velocity, heat storage dynamics, thermal stratification and thermocline thickness in storage tank. The smallest diameter causes unfavourable thermal mixing of accumulated water, and the largest diameter supports thermal stratification

scholarly journals ENERGY AND EXERGY ANALYSIS OF A CYLINDRICAL HOT WATER STORAGE TANK: EXPERIMENTAL AND CFD ANALYSIS

2020 ◽  
Author(s):  
Tomas Kropas ◽  
Giedrė Streckienė
Keyword(s):  
Numerical Model ◽  
Storage Tank ◽  
Exergy Analysis ◽  
Water Storage ◽  
Exergy Efficiency ◽  
Hot Water ◽  
Water Storage Tank ◽  
Environment Temperature ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

Active solar water heating systems typically include hot water storage tanks. The selection of the storage system strongly affects the performance of the entire system. This article presents a detailed analysis of a hot water storage tank during charging and dynamic charging-discharging mode. A numerical model using computational fluid dynamics for the storage tank was developed to investigate the temperature distribution inside of it. Transient thermal analysis was carried using ANSYS Fluent. The numerical model was validated with the experimental results. The energy and exergy analysis as an important tool for the evaluation of the thermal systems quantitatively and qualitatively was performed. The calculation procedures were described. The energy and exergy efficiencies, heat losses were calculated for steady and dynamic processes. Effect of mass flow rate was analysed. The results from parametric analysis showed that charging dynamics reduced the thermocline and efficiency of the hot water storage tank. The dependency of the exergy efficiency of the heat storage tank on the reference environment temperature during the dynamic operation was analysed. Exergy efficiencies for two cities with different climates were compared. This indicated that the higher envi-ronmental temperature gave lower exergy efficiency of the storage tank.

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

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4741
Author(s):  
María Gasque ◽  
Federico Ibáñez ◽  
Pablo González-Altozano
Keyword(s):  
Experimental Data ◽  
Water Temperature ◽  
Temperature Profile ◽  
Storage Tank ◽  
Water Storage ◽  
Hot Water ◽  
Experimental Temperature ◽  
Inlet Temperature ◽  
Water Storage Tank ◽  
Minimum Number

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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