Solidification Enhancement in a Triple-Tube Latent Heat Energy Storage System Using Twisted Fins
TL;DR: In this paper, the authors evaluated the influence of combining twisted fins in a triple-tube heat exchanger utilised for latent heat thermal energy storage (LHTES) in three-dimensional numerical simulation and compared the outcome with the cases of the straight fins and no fins.
Abstract: This work evaluates the influence of combining twisted fins in a triple-tube heat exchanger utilised for latent heat thermal energy storage (LHTES) in three-dimensional numerical simulation and comparing the outcome with the cases of the straight fins and no fins. The phase change material (PCM) is in the annulus between the inner and the outer tube, these tubes include a cold fluid that flows in the counter current path, to solidify the PCM and release the heat storage energy. The performance of the unit was assessed based on the liquid fraction and temperature profiles as well as solidification and the energy storage rate. This study aims to find suitable and efficient fins number and the optimum values of the Re and the inlet temperature of the heat transfer fluid. The outcomes stated the benefits of using twisted fins related to those cases of straight fins and the no-fins. The impact of multi-twisted fins was also considered to detect their influences on the solidification process. The outcomes reveal that the operation of four twisted fins decreased the solidification time by 12.7% and 22.9% compared with four straight fins and the no-fins cases, respectively. Four twisted fins improved the discharging rate by 12.4% and 22.8% compared with the cases of four straight fins and no-fins, respectively. Besides, by reducing the fins’ number from six to four and two, the solidification time reduces by 11.9% and 25.6%, respectively. The current work shows the impacts of innovative designs of fins in the LHTES to produce novel inventions for commercialisation, besides saving the power grid.
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TL;DR: In this article , a 3D numerical model is established and verified by visualization experiment to evaluate the effect of fin and metal foam on the internal melting process compared with pure paraffin structure.
28 citations
TL;DR: In this article , the authors investigated the impact of modifying the fin geometric characteristics and distribution patterns in various spatial zones of the heat exchanger, and found that changing the fin dimensions with the heat flow direction results in a faster charging rate, a higher storage rate, and a more uniform temperature distribution when compared to a uniform fin size.
Abstract: Employing phase-change materials (PCM) is considered a very efficient and cost-effective option for addressing the mismatch between the energy supply and the demand. The high storage density, little temperature degradation, and ease of material processing register the PCM as a key candidate for the thermal energy storage system. However, the sluggish response rates during their melting and solidification processes limit their applications and consequently require the inclusion of heat transfer enhancers. This research aims to investigate the potential enhancement of circular fins on intensifying the PCM thermal response in a vertical triple-tube casing. Fin arrays of non-uniform dimensions and distinct distribution patterns were designed and investigated to determine the impact of modifying the fin geometric characteristics and distribution patterns in various spatial zones of the heat exchanger. Parametric analysis on the various fin structures under consideration was carried out to determine the most optimal fin structure from the perspective of the transient melting evolution and heat storage rates while maintaining the same design limitations of fin material and volume usage. The results revealed that changing the fin dimensions with the heat-flow direction results in a faster charging rate, a higher storage rate, and a more uniform temperature distribution when compared to a uniform fin size. The time required to fully charge the storage system (fully melting of the PCM) was found to be reduced by up to 10.4%, and the heat storage rate can be improved by up to 9.3% compared to the reference case of uniform fin sizes within the same fin volume limitations.
23 citations
TL;DR: In this paper , the performance enhancement of a shell and tube latent heat thermal energy storage (LHTES) system in terms of energy and exergy has been assessed by implementing twisted fins in a PCM enclosure with both vertical and horizontal orientations by using Finite Volume Method and the Enthalpy-Porosity method has been used for simulating the melting process.
18 citations
TL;DR: In this paper , the authors summarized the current development process of new fins in the industry and the optimization results of the size, shape, and arrangement of fin by related researchers and analyzed the strengthening mechanism of heat transfer effect enhancement.
Abstract: In the process of industrial waste heat recovery, phase change heat storage technology has become one of the industry's most popular heat recovery technologies due to its high heat storage density and almost constant temperature absorption/release process. In practical applications, heat recovery and utilization speed are particularly critical. Developing fins with reasonable structure or optimizing the original fins can speed up the process of heat storage and utilization to a certain extent. To improve the heat transfer enhancement design efficiency of fins and expand their application and reference range, this paper summarizes the current development process of new fins in the industry and the optimization results of the size, shape, and arrangement of fins by related researchers. It aims at these research results and how to design the shape, size, quantity, and arrangement of heat exchange fins from four proposed ideas and methods. The strengthening mechanism of heat transfer effect enhancement is analyzed. The research results show that the multi-branch structure is the research direction of the new fin design in the future; the non-uniform fin array has better heat transfer performance than the uniform fin array; the targeted arrangement of fins can maximize the heat transfer effect; there is an optimal number of fins in the heat accumulator; the parameters such as the size and number of fins and the size parameters of the heat accumulator are not independent of each other, but influence and restrict each other. The design process needs to be considered comprehensively; the topology optimization method, multi-objective response surface method, Taguchi method, orthogonal test method, etc., are commonly used in optimizing the shape and size of fins, which are simple and efficient. • Fine, multi-branched structure for deeper thermal penetration • Topology optimization, RSM, Taguchi, and orthogonal methods are commonly used in fin design. • Non-uniform fin arrays have better unilateral heat transfer than uniform arrays. • Optimal design of fins for the dominant heat transfer mechanism in different zones • Optimum heat transfer level in relation to optimum number of fins, thickness etc.
11 citations
TL;DR: In this article , the authors focused on the technical performance indicator and specifically on predictive methods which aid the assessment of the performance of a LTES heat exchanger in a system, and the relation between the averaged effectiveness and phase change time was investigated both theoretically and based on data available in literature.
Abstract: Latent thermal energy storage (LTES) heat exchangers can provide energy storage in a broad range of energy systems. Implementing LTES heat exchangers requires an assessment of their performance in a given system. The performance of a LTES heat exchanger is described by its performance indicators which are classified as technical, economical, and life-cycle indicators. The current paper focusses on the technical performance indicator and specifically on predictive methods which aid the assessment of the performance of a LTES heat exchanger in a system. To structure the analysis, a thermodynamic framework is provided which allows to clearly define LTES heat exchangers and classify the technical performance indicators. In a second step, the literature is reviewed for reported technical performance indicators with a specific focus on predictive methods for these indicators. The averaged effectiveness-number of transfer units (ε-NTU) and phase change time method are identified as important predictive models, analyzed, and compared based on their theoretical derivation. The relation between the averaged effectiveness and phase change time is investigated both theoretically and based on data available in literature which results in recommendations for standardizing the characterization of LTES heat exchangers. By standardizing characterization of LTES heat exchangers, researcher can assess their performance in different energy systems without additional experiments or CFD calculations.
4 citations
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TL;DR: In this paper, the enhancement of thermal conductivity by the introduction of highly thermally conductive metallic and carbon-based nanoparticles, metallic foams, expanded graphite and encapsulation of PCM is discussed.
427 citations
TL;DR: In this paper, the melting process in a triplex-tube heat exchanger with phase-change material (PCM) RT82.26 was numerically investigated using the Fluent 6.3.
363 citations
TL;DR: In this article, heat transfer enhancement technique by using internal and external fins for PCM melting in a triplex tube heat exchanger (TTHX) was investigated numerically.
350 citations
TL;DR: In this paper, the augmentation in heat transfer for a shell and tube type LHSU is estimated by carrying out experimental analysis with three longitudinal fins installed on the heat transfer fluid (HTF) tube.
302 citations
TL;DR: In this article, a review of heat transfer enhancement techniques between phase change material (PCM) and the heat transfer fluid (HTF) based on the application of fins embedded in the PCM is presented.
Abstract: The continuous increase in the level of green-house gas emissions and the depletion of fossil fuels are identified, as the major driving forces behind efforts to effectively utilize different sources of renewable energy. Solar energy considered one of the most prospective sources of this energy. This review paper mainly focuses on the majority of heat-transfer enhancement techniques between the phase-change material (PCM) and the heat-transfer fluid (HTF) based on the application of fins embedded in the PCM. This study also investigated the geometrical dimensions, dimensionless numbers, and fin location through numerical and experimental works conducted to assess the influences of these parameters on the thermal performance of PCM-latent heat thermal energy storage (LHTES) containers. The best enhancement is achieved using the longitudinal finned configurations because of its easy design and fabrication, especially along circumference of the cylindrical PCM containers. The circular-finned tube was also more effective than the pinned-tube for different shell and tube. PCMs based on heat sinks with internal pin fins were widely used for the thermal management of various pieces of electronic products. The heat enhancement factor was effectively dependent on increasing the numbers and dimensions of these fins. Further researches still require to explore the possible geometrical designs of fins and their key findings, which have more effect on the thermal performance of the finned-LHTES system.
248 citations