CFD MODELING OF HEAT TRANSFER AND HYDRODYNAMICS PROCESSES IN A HEAT STORAGE TANK
DOI:
https://doi.org/10.20535/kpi-sn.2020.2.205113Keywords:
Free convection, Heat storage tank, Temperature stratification, Thermal core, Ozokerite, Petrolatum, CeresinAbstract
Background. Today, heat storage tanks are an integral part of heating systems. However, modern designs of capacitive storage tanks are characterized by the phenomenon of thermocline and high thermal inertia. To minimize the aforementioned disadvantages, it is proposed to use a “thermal core”, for the formation of which it is necessary to select a substance with a high value of heat capacity.
Objective. The purpose of the presented study is to simulate the process of heat and mass transfer in a storage tank with a “thermal core”, in the form of the binary tube located on the central axis, the inter tube space of which is filled with paraffin (a mixture of saturated hydrocarbons with melting point – from 45 °C to 65 °C; dense – 0.880–0.915 g/cm3 at 15 °C).
Methods. Fluent software determines the temperature distribution in the heat storage tank under free convection conditions. The resulting data were then converted into a calculation module of the Transient Thermal software complex ANSYS, where further calculations of the non-stationary temperature distribution of the “thermal core” were carried out.
Results. It is determined that the heat storage tank with a capacity of 1400 liters, heated for one hour by a heat transfer agent with a temperature of 115 °C, is cooled to 50 °C in 4 hours. The analysis of the hydrodynamic structure of the flow based on the distribution of the trajectories of movement of free-convective flows in the water column of the storage tank indicates the need to improve the design of the tank. It is determined that the use of the “thermal core”, regardless of the type of paraffin used for its formation, helps to reduce the stratification of temperature by tank height. The type of paraffin used to form the “heat core” has no significant effect on the cooling time of the heat storage tank as a whole. However, when using “ceresin” as a filler for the “heat core”, the average tank temperature is generally about 0.5 °C higher than for other paraffin types studied. Thus, it is “ceresin” that should be used as a “thermal core”.
Conclusions. The result of the calculation of the inhomogeneous temperature field of all elements of the heat storage tank was used to determine the time of its complete cooling. The conducted research allows automating the process of calculation of the storage tanks as well as carrying out their modernization to increase the efficiency of use.References
Hydrotherm Engineering [Online]. Available: http://www.gidro-term.com.ua/142-stati/376-bak-akkumulyator-tepla-teploakkumulyator-ustrojstvo-montazh-normy
Boiler-houses, DBN V.2.5-77, 2014.
Thermal Networks, DBN V.2.5-39, 2009.
O.G. Martinenko and Yu.A. Sokovishin, Free Convective Heat Transfer. Mosсow, SU: Science and Technology, 1982, 400 p.
D.V. Ivanov and A.V. Dol, Introduction to Ansys Workbench. Saratov, Russia: Amirit, 2016, 56 p.
V.I. Myachenkov et al., Calculations of Engineering Structures using the Finite Element Method. Moscow, SU: Mechanical Engineering, 1989, 520 p.
Downloads
Published
Issue
Section
License
Copyright (c) 2020 The Author(s)
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under CC BY 4.0 that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work