scholarly journals Diagnostics of a Domestic Hot Water Storage Tank under Operating Conditions

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1771
Author(s):  
Paweł Obstawski ◽  
Monika Janaszek-Mańkowska ◽  
Arkadiusz Ratajski
Keyword(s):  
Heat Exchanger ◽  
Dynamic Properties ◽  
Water Storage ◽  
Operating Conditions ◽  
Hot Water ◽  
Domestic Hot Water ◽  
Water Storage Tank ◽  
Coil Heat Exchanger ◽  
Coil Heat

This paper presents a new method for the diagnostics of a hot water storage tank under operating conditions. Depending on the operating point of the tank, the method enables determination of thermal conductivity coefficients of the coil heat exchanger, which allows us to determine the intensity of heat transfer between the transfer medium and water in the tank as well as of tank walls, which consequently enables determination of heat losses to the environment. Furthermore, the dynamic properties of the tank may also be determined by applying this method. The advantage of this method is possibility of analyzing changes in the material constants of the coil heat exchanger, tank walls, and dynamic properties of the tank as a function of mass flow of the medium supplying the coil heat exchanger. The possibility of determining coefficients of thermal conductivity as well as the inertia of tank and exchanger, based on temperature measurements acquired in operating conditions is a novelty in this paper. Knowing the variability of material constants and of dynamic properties of the tank as a function of medium flow rate allows multicriteria optimization to be performed which, with a conventional design of the tank, results in a reduction of up to 10% in the time taken to prepare domestic hot water.

A Transient Immersed Coil Heat Exchanger Model

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
William R. Logie ◽  
Elimar Frank
Keyword(s):  
Heat Exchanger ◽  
Water System ◽  
Operating Conditions ◽  
Hot Water ◽  
Simulation Environment ◽  
One Dimensional ◽  
Solar Fraction ◽  
Coil Heat Exchanger ◽  
Side Flow ◽  
Coil Heat

The aim of this paper is to present a transient one-dimensional (1D) radial immersed coil heat exchanger model that accounts for the effect that geometry and operating conditions have on heat transfer performance. Insights gained through its use in both an analysis of experimental data and an implementation in the simulation environment TRNSYS are shown and discussed. While variation in the external convection coefficient of immersed coil heat exchangers has little effect on the annual solar fraction of a generic solar domestic hot water system, variation in collector side flow can influence the solar fraction as great as ±5%, in particular low collector side flow improves stratification inside the store.

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.

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

2012 ◽  
Author(s):  
Nathan Devore ◽  
Henry Yip ◽  
Jinny Rhee
Keyword(s):  
Heat Exchanger ◽  
Storage Tank ◽  
Thermal Stratification ◽  
Reverse Flow ◽  
Storage System ◽  
Water Storage ◽  
Hot Water ◽  
Solar Panels ◽  
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 while simultaneously increasing the temperature delta 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 upwards, 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.

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 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

Effects of Baffle Width on Heat Transfer to an Immersed Coil Heat Exchanger: Experimental Optimization

2019 ◽  
Author(s):  
Julia Haltiwanger Nicodemus ◽  
Xiaoqi Huang ◽  
Emily Dentinger ◽  
Kyle Petitt ◽  
Joshua H. Smith
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Convection Heat Transfer ◽  
Hot Water ◽  
Outlet Temperature ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Water Storage Tank ◽  
Coil Heat Exchanger

Abstract In this work, we investigate the effects of the width of an annular baffle region on natural convection heat transfer to an immersed, coiled heat exchanger in an otherwise quiescent sensible hot water storage tank. In experiments, the coiled heat exchanger sits in an annular region created by the tank wall and a straight, cylindrical baffle. The width of this baffle region is 1.5, 2, 3, or 4 times the heat exchanger diameter, These experiments are compared to each other and to corresponding control experiments with no baffle. In general, all baffles create considerable benefits over their respective control experiments, consistent with past studies. The considered metrics of heat transfer rate, fraction of energy discharged from the tank, and heat exchanger outlet temperature show that heat transfer is improved slightly by narrowing the baffle region. For example, relative to their respective controls, the energy extracted from the tank after 30 min of discharge in the 1.5D, 2D, 3D and 4D experiments is 23.2%, 20.8%, 18.1%, and 14.7% higher, respectively. This improvement in natural convection heat transfer as the baffle region narrows is attributed to the increasing thermal stratification observed in experiments with increasingly narrow baffle regions.

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