On the Effectiveness of Baffles in Indirect Solar Storage Systems

2007 ◽  
Vol 129 (4) ◽  
pp. 494-498 ◽  
Author(s):  
F. A. Kulacki ◽  
Jane H. Davidson ◽  
M. Hebert
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Storage Systems ◽  
Boundary Layer Theory ◽  
Base Case ◽  
Thermal Plume ◽  
Storage Tanks ◽  
Physical Mechanisms ◽  
Design Factors ◽  
Insight Into

Parameters that control heat transfer and mixing in energy extraction from indirect solar storage tanks that employ an immersed heat exchanger with a straight baffle beneath are identified and estimated. The analysis of flow in the baffle is based on boundary layer theory and provides insight into the effectiveness of a baffle in controlling growth of the thermal plume from the heat exchanger. The important physical mechanisms are the restricted entrainment and heat transfer to the storage fluid. For an adiabatic baffle as a base case, key design factors are the point of attachment of the plume on the baffle and the width of the baffle relative to that of the heat exchanger.

Effect of Shroud and Baffle on Heat Transfer in a Solar Thermal Storage Tank

2009 ◽  
Author(s):  
S. K. S. Boetcher ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Transfer Rate ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Discharge Process ◽  
Storage Tanks ◽  
Nusselt Numbers ◽  
Enhancing Heat Transfer ◽  
Rayleigh Numbers

Enhancing heat transfer during the charge and discharge of solar thermal storage tanks is an ongoing technical challenge. The types of thermal storage systems considered in the present study comprise an immersed heat exchanger at the top of a solar thermal storage fluid. The discharge process of a thermal store with specified dimensions is numerically simulated over a range of Rayleigh numbers, 105 < RaD <107. The immersed heat exchanger is modeled as a two-dimensional isothermal cylinder which is situated near the top of a water-filled tank with adiabatic walls. An adiabatic shroud whose shape is parametrically varied is placed around the cylinder. In addition, the shroud is connected to an adiabatic baffle situated beneath the cylinder. Nusselt numbers are calculated for different shroud shapes at different Rayleigh numbers. Results show that the shroud is effective in increasing the heat transfer rate. Optimal shroud and baffle geometries are presented as well as qualitative flow results.

Numerical Investigation of a Heated Sodium Jet in a Co-Flow

2007 ◽  
Author(s):  
I. Otic´ ◽  
A. G. Class
Keyword(s):  
Heat Transfer ◽  
Pipe Wall ◽  
Experimental Studies ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Velocity ◽  
Temperature Variance ◽  
Physical Mechanisms ◽  
Insight Into ◽  
Good Agreement

Results of a numerical simulation of turbulent heated sodium jet in a co-flow using a combined LES-DNS approach are presented. The calculations correspond to the experiment of Knebel, Krebs, Muller and Axcell [1]. In agreement with the experimental results co-flow suppresses flow reversal along the outlet pipe wall. Comparisons of mean velocity, mean temperature, and temperature variance between experimental and numerical results show fairly good agreement. The results support the applicability of the combined LES-DNS approach for this type of flows. Simulations using this approach may complement experimental studies, allowing for better insight into the physical mechanisms of liquid metal turbulent heat transfer.

New Design of a Bimetallic Finned Tube for the Use in Latent Heat Thermal Energy Storage Units

2015 ◽  
Author(s):  
Georg Urschitz ◽  
Jens Brier ◽  
Heimo Walter ◽  
Roland Mertz ◽  
Friedrich Bleicher ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Heat Exchanger ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage Systems ◽  
Energy Storage Systems ◽  
Thermal Energy Storage Systems ◽  
Change Material

The use of finned tubes as enhancement method to increase the heat flow rate into a phase change material, which has in many cases a low thermal conductivity, is a common method. A highly efficient and easy-to-assemble solution for finned heat exchanger tubes is a key component for innovative thermal energy storage systems which play a key-role in electricity production and industrial heat management. In the present article the results of the investigation for different designs of bimetallic heat exchanger tubes is presented. These tube designs are developed for the use in latent heat thermal energy storage systems (LHTES) at a medium temperature range. For the use in latent heat thermal energy storage systems, the probably high pressure of the heat transfer medium and the high temperature differences between the operating temperature and the ambient temperature are challenging. Therefore, the bimetallic finned heat exchanger tube consists of a steel tube, where the heat transfer fluid flows, and an aluminum tube with longitudinal fins, which should improve the heat transfer to the phase change material. Due to different thermal expansion coefficients, displacements of the tubes are given. To guarantee a high heat transfer rate between the two connected tubes the contact between aluminum and steel plays an important role. In the present study 4 prototypes (including the new design) were designed, analyzed and compared on the connection strength. Long-term tests for simulating the application in a LHTES were done to determine the creep rupture properties of the compositions. All prototypes were tested successfully; the new design is convinced in many aspects of that challenge and is submitted to the Austrian patent office. Main advantages of the new design are the simple production and assembling compared to other analyzed prototypes. Furthermore, the new design shows the best results under the analyzed operation conditions and the layout of the geometry has a high optimization potential in terms of stresses.

A Numerical Study Concerning Indirect Ice Storage Tanks Performance

2004 ◽  
Author(s):  
Cleyton S. Stampa ◽  
Angela O. Nieckele
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Storage Tank ◽  
Numerical Study ◽  
Exchange Process ◽  
Vertical Position ◽  
Ice Storage ◽  
Tank Wall ◽  
Storage Tanks ◽  
Flat Plates

A numerical investigation regarding the charging process behavior occurring in a typical indirect ice storage tank is presented. It consists of analyzing the heat transfer and removal of energy, applicable to storage systems, which are chiller-based. In this sense the secondary coolant circulates through a heat exchanger that is submerged in a tank of water and it is used to freeze (charge) the phase-change material (water), which never leaves the storage tank. The thermal exchange process is investigated in critical regions formed between the heat exchanger wall and the tank wall. The present study simulates such regions through a channel formed by parallel flat plates, one of which is the heat exchanger, and investigates the heat transfer effects considering it in two different positions. In the first one the channel is in the vertical position, while for the second, it is horizontally positioned. Our task is to provide helpful qualitative results for the heat transfer performance of ice storage tanks. The results are analyzed through streamlines and isotherms, for specific instants of time. Further, the heat transfer effectiveness, average heat flux and solid formed at one of the two plates of the channel, are compared for the vertical and horizontal positions of the channel, as well as different distances from the heat exchanger and tank wall.

scholarly journals Heat Transfer Enhancement due to Acoustic Fields: A Methodological Analysis

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 281-294 ◽  
Author(s):  
Alessandro Franco ◽  
Carlo Bartoli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Thermodynamic System ◽  
Industrial Applications ◽  
General Validity ◽  
Physical Mechanisms ◽  
Physical Phenomena

The aim of this paper is to expose the main involved physical phenomena underlying the alteration of convective heat transfer in a heat exchanger subjected to imposed vibrations. This technique seems to have interesting features and industrial applications, such as for efficiency increases, heat transfer rate control and cleanliness action. However, a clear description and comprehension of how vibrations may alter the convective heat transfer coefficient in a heat exchanger has still not been reached due to the complexity of the involved physical mechanisms. For this reason, after a presentation and a schematization of the analyzed thermodynamic system, the fundamental alterations of the thermo-fluid dynamics fields are described. Then, the main involved physical phenomena are exposed for the three cases of gaseous, monophasic liquid and boiling liquid mediums. Finally, on the basis of the characteristics of these described phenomena, some considerations and indications of general validity are presented.

Thermohydraulic optimization of triple concentric-tube heat exchanger: A multi-objective approach

2018 ◽  
Vol 233 (3) ◽  
pp. 589-600 ◽  
Author(s):  
Tarikayehu Amanuel ◽  
Manish Mishra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Effective Parameters ◽  
Ansys Fluent ◽  
Tube Heat Exchanger ◽  
Large Growth ◽  
Design Factors ◽  
Response Variables

In the present study, optimization of heat transfer and pressure drop characteristics in a triple concentric tube heat exchanger has been done using the results of numerical simulation. A commercial CFD software ANSYS Fluent v17.0 has been employed for simulating the flow and heat transfer, while optimization has been done by Response surface methodology (RSM) and Genetic algorithm (GA). The effective parameters in the study are Reynolds number (2500 ≤ Re ≤ 10,000) and Length to hydraulic diameter ratio (100 ≤ L/Dh ≤ 220). The optimum values, as well as the functional relationship between the design factors (Re and L/Dh) and response variables (Nu and f), have also been developed. It has been found that both the design factors (Re and L/Dh) have a strong influence on the response variables (Nu and f). With the increase in Re (flow rate), a large growth in Nusselt number and decline in friction factor has been observed. However, with the increase in L/Dh, an enormous decrease in both Nusselt number and friction factor has been found.

scholarly journals NUMERICAL ANALYSIS OF INDIRECT ICE STORAGE SYSTEMS PERFORMANCE

2006 ◽  
Vol 5 (1) ◽  
pp. 84
Author(s):  
C. S. Stampa ◽  
A. O. Nieckele
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Storage Tank ◽  
Storage Systems ◽  
Exchange Process ◽  
Vertical Position ◽  
Ice Storage ◽  
Flat Plates ◽  
Thermal Exchange ◽  
Process Behavior

A numerical investigation regarding the charging process behavior occurring in a typical indirect ice storage tank is presented. It consists of analyzing the heat transfer and removal of energy, applicable to storage systems, which are chiller-based. In this sense the secondary coolant circulates through a heat exchanger that is submerged in a tank of water and it is used to freeze (charge) the phase-change material (water), which never leaves the storage tank. The thermal exchange process is investigated considering the storage tank in two different positions. In the first one the storage tank is in the vertical position, while for the second, it is horizontally positioned. The storage tank is represented by a channel formed by parallel flat plates, one of which is the heat exchanger. Our task is to provide helpful qualitative results for the heat transfer performance of ice storage tanks. The results are analysed through streamlines and isotherms, for specific instants of time. Further, the heat transfer effectiveness, average heat flux and solid formed at one of the two plates of the channel, are compared for the vertical and horizontal positions of the channel.

scholarly journals The Influence of the Punched Delta Wings on Flow Pattern and Heat Transfer Characteristic in a Fin-and-Oval-Tube Heat Exchanger

2015 ◽  
Vol 2015 ◽  
pp. 1-18
Author(s):  
Amnart Boonloi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Thermal Performance ◽  
Transfer Characteristic ◽  
Base Case ◽  
Delta Wings ◽  
Tube Heat Exchanger ◽  
Wing Tips ◽  
Oval Tube

3D numerical investigations are performed to study the heat transfer, friction factor, and thermal performance of a fin-and-oval heat exchanger with punched delta wings for a range of 500 ≤ Re ≤ 2500 (based on the hydraulic diameter). The influences of the punched angles, 20°, 30°, and 45°, flow directions, wing tips pointing downstream and upstream, and pitch ratios, 2, 3, 4, 5, and 6, are investigated. The results show that the use of the punched delta wings in the fin-and-oval-tube heat exchanger leads to an enhancement in the heat transfer and friction loss as compared to the plain fin for all cases (Nu/Nu0 and f/f0 higher than 1). The enhancements of the heat transfer and friction factor are around 1.01–1.22 and 1.37–2.65 times higher than the base case, respectively. The punched delta wings create the vortex flows through the test section that helps enhance the strength of the impinging flow on the tube walls. The impingement of the fluid flow is an important key to augment the heat transfer rate and thermal performance in the heat exchanger.

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