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

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 The study is conducted in a transient mode, namely, the tank is filled with hot water, and as the hot water is being withdrawn, the tap water replaces it in a stratified way or by mixing.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.

scholarly journals Numerical Simulations of Temperature and Velocity Fields in the Storage Tank with the Three-Coil Heat Exchanger

2020 ◽  
Vol 44 (3) ◽  
pp. 74-79
Author(s):  
Robert Smusz ◽  
Joanna Wilk ◽  
Paweł Bałon
Keyword(s):  
Numerical Simulations ◽  
Storage Tank ◽  
Thermal Stratification ◽  
Waste Heat ◽  
Velocity Fields ◽  
Operating Conditions ◽  
Hot Water ◽  
Water Storage Tank ◽  
Coil Heat Exchanger ◽  
Temperature And Velocity Fields

AbstractThis article presents the results of the numerical investigation of the thermal stratification in the hot water storage tank. The exchanger consists of three tube coils that are immersed in the storage tank of hot water. Two coils—lower and upper—are designed to warm the water in the tank using the water as a heating medium. Another coil—uses the refrigerant for the waste heat transfer. The temperature stratification device is mounted in the thermal storage tank. The device’s task is to improve the thermal stratification level of heated water. The performed numerical simulations allowed us to obtain the temperature and velocity fields in the storage tank under the conditions of the work of coils filled with water. Calculations were made in the case of the use of the stratification device under the operating conditions of the upper and lower coils with water.

The thermal stratification characteristics affected by a novel equalizer in a dynamic hot water storage tank

2017 ◽  
Vol 126 ◽  
pp. 1006-1016 ◽  
Author(s):  
Zilong Wang ◽  
Hua Zhang ◽  
Binlin Dou ◽  
Huajie Huang ◽  
Guanhua Zhang
Keyword(s):  
Storage Tank ◽  
Thermal Stratification ◽  
Water Storage ◽  
Hot Water ◽  
Water Storage Tank

The Effect of Obstacle Geometry and Position on Thermal Stratification in Solar Hot Water Storage Tanks

2008 ◽  
Author(s):  
Necdet Altuntop ◽  
Veysel Ozceyhan ◽  
Yusuf Tekin ◽  
Sibel Gunes
Keyword(s):  
Storage Tank ◽  
Thermal Stratification ◽  
Water Storage ◽  
Hot Water ◽  
Storage Tanks ◽  
Domestic Hot Water ◽  
Water Storage Tank ◽  
Temperature Distributions ◽  
Solar Powered ◽  
Obstacle Geometry

In this study the effect of obstacle geometry and its position on thermal stratification in solar powered domestic hot water storage tanks are numerically investigated. The goal of this study is to obtain higher thermal stratification and supply hot water for usage as long as possible. The temperature distributions are presented for three different obstacle geometries (1, 2 and 3) and six different distances (f = 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 mm) from the bottom of the hot water storage tank. The numerical method is validated using both experimental and numerical results available in the literature. It is observed from the results that the thermal stratification increases with the increasing obstacle distance from the bottom of the hot water storage tank for obstacle 1 and 3. The obstacle 2 provides less thermal stratification than the obstacles 1 and 3. As a result, in a duration of 30 minutes, the obstacle 3 provides the best thermal stratification for the distance of f = 0.8 mm from the bottom of the hot water storage tank.

Thermal stratification in a solar hot water storage tank with mantle heat exchanger

2021 ◽  
Author(s):  
Qiong Li ◽  
Xiaoqiao Huang ◽  
Yonghang Tai ◽  
Wenfeng Gao ◽  
Wenxian Lin ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Storage Tank ◽  
Thermal Stratification ◽  
Water Storage ◽  
Hot Water ◽  
Water Storage Tank

Experimental and numerical research of thermal stratification with a novel inlet in a dynamic hot water storage tank

2017 ◽  
Vol 111 ◽  
pp. 353-371 ◽  
Author(s):  
Zilong Wang ◽  
Hua Zhang ◽  
Binlin Dou ◽  
Huajie Huang ◽  
Weidong Wu ◽  
...  
Keyword(s):  
Storage Tank ◽  
Thermal Stratification ◽  
Water Storage ◽  
Hot Water ◽  
Water Storage Tank ◽  
Numerical Research

Domestic Hot Water Storage Tank: Design and Analysis for Improving Thermal Stratification

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Nathan Devore ◽  
Henry Yip ◽  
Jinny Rhee
Keyword(s):  
Heat Exchanger ◽  
Storage Tank ◽  
Thermal Stratification ◽  
Reverse Flow ◽  
Storage System ◽  
Water Storage ◽  
Hot Water ◽  
Inlet Temperature ◽  
Domestic Hot Water ◽  
Water Storage Tank

Experimental designs for a solar domestic hot water storage system were built in efforts to maximize thermal stratification within the tank. A stratified thermal store has been shown by prior literature to maximize temperature of the hot water drawn from the tank and simultaneously minimize collector inlet temperature required for effective heat transfer from the solar panels, thereby improving the annual performance of domestic solar hot water heating systems (DSHWH) by 30–60%. Our design incorporates partitions, thermal diodes, and a coiled heat exchanger enclosed in an annulus. The thermal diodes are passive devices that promote natural convection currents of hot water upward, while inhibiting reverse flow and mixing. Several variations of heat exchanger coils, diodes and partitions were simulated using ansys Computational Fluid Dynamics, and benchmarked using experimental data. The results revealed that the optimum design incorporated two partitions separated by a specific distance with four diodes for each partition. In addition, it was discovered that varying the length and diameter of the thermal diodes greatly affected the temperature distribution. The thermal diodes and partitions were used to maintain stratification for long periods of time by facilitating natural convective currents and taking advantage of the buoyancy effect. The results of the experiment and simulations proved that incorporating these elements into the design can greatly improve the thermal performance and temperature stratification of a domestic hot water storage tank.

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