scholarly journals Numerical and Experimental Investigation of Wire Cloth Heat Exchanger for Latent Heat Storages

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7542
Author(s):  
Sebastian Gamisch ◽  
Stefan Gschwander ◽  
Stefan J. Rupitsch
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Phase Change Materials ◽  
Tube Bundle ◽  
Thermal Power ◽  
Pareto Frontier ◽  
Frontier Analysis ◽  
Free Arrangement ◽  
The Wire ◽  
Wire Cloth

Latent thermal energy storages (LTES) offer a high storage density within a narrow temperature range. Due to the typically low thermal conductivity of the applied phase change materials (PCM), the power of the storages is limited. To increase the power, an efficient heat exchanger with a large heat transfer surface and a higher thermal conductivity is needed. In this article, planar wire cloth heat exchangers are investigated to obtain these properties. They investigated the first time for LTES. Therefore, we developed a finite element method (FEM) model of the heat exchanger and validated it against the experimental characterization of a prototype LTES. As PCM, the commercially available paraffin RT35HC is used. The performance of the wire cloth is compared to tube bundle heat exchanger by a parametric study. The tube diameter, tube distance, wire diameter and heat exchanger distance were varied. In addition, aluminum and stainless steel were investigated as materials for the heat exchanger. In total, 654 variants were simulated. Compared to tube bundle heat exchanger with equal tube arrangement, the wire cloth can increase the mean thermal power by a factor of 4.20 but can also reduce the storage capacity by a minimum factor of 0.85. A Pareto frontier analysis shows that for a free arrangement of parallel tubes, the tube bundle and wire cloth heat exchanger reach similar performance and storage capacities.

Macroencapsulation of Sodium Nitrate for Thermal Energy Storage in Solar Thermal Power

2012 ◽  
Author(s):  
Swetha Pendyala ◽  
Prashanth Sridharan ◽  
Sarada Kuravi ◽  
Chand K. Jotshi ◽  
Manoj K. Ram ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Metal Oxide ◽  
Sodium Nitrate ◽  
Large Scale ◽  
Phase Change Materials ◽  
Thermal Power ◽  
High Energy ◽  
Chemical Oxidation ◽  
Latent Heat Storage

Storage systems based on latent heat storage have high-energy storage density, which reduces the footprint of the system and the cost. However, phase change materials (PCMs) have very low thermal conductivities making them unsuitable for large-scale use without enhancing the effective thermal conductivity. In order to address the low thermal conductivity of the PCMs, macroencapsulation of PCMs is adopted as an effective technique. The macro encapsulation not only provides a self-supporting structure but also enhances the heat transfer rate. In this research, Sodium nitrate (NaNO3), a low cost PCM, was selected for thermal storage in a temperature range of 300–500°C. The PCM was encapsulated in a metal oxide cell using self-assembly reactions, hydrolysis, and simultaneous chemical oxidation at various temperatures. The metal oxide encapsulated PCM capsule was characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The cyclic stability and thermal performance of the capsules were also studied.

Elaboration of Conductive Thermal Storage Composites Made of Phase Change Materials and Graphite for Solar Plant

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
S. Pincemin ◽  
X. Py ◽  
R. Olives ◽  
M. Christ ◽  
O. Oettinger
Keyword(s):  
Thermal Conductivity ◽  
Power Plants ◽  
Phase Change Materials ◽  
Thermal Power ◽  
Thermal Storage ◽  
Steam Generation ◽  
Solar Plant ◽  
Pure Salt ◽  
Solar Steam Generation ◽  
Melting And Solidification

New thermal storage composites made of graphite and PCM (NaNO3∕KNO3 eutectic) have been developed for solar thermal power plants using direct solar steam generation. Those materials, obtained using different elaboration routes (compounding, infiltration, cold compression) and graphite types, are presented with their respective properties (enhanced thermal conductivities, thermal storage capacities, stability) and compared together. Both the laboratory and industrial scales and grades are considered and compared. The infiltration route has been found to be inefficient before the two other ones. Compound composites present isotropic properties and thermal conductivity intensification in the medium range (a factor of 10 for 7wt% in graphite). Cold compressed composites present highly anisotropic properties and strong intensification in thermal conductivity (a factor of 31 at 200°C for 20wt% in graphite). Their melting and solidification temperatures as well as their intrinsic storage capacity are close to the pure salt ones.

scholarly journals Interpretation of rock mass thermal conductivity at the design stage of heat pump installation and its impact on system efficiency (COP)

2018 ◽  
Vol 66 ◽  
pp. 02007
Author(s):  
Michał Kaczmarczyk ◽  
Magda Kaczmarczyk ◽  
Konrad Thürmer ◽  
Magdalena Klich
Keyword(s):  
Thermal Conductivity ◽  
Rock Mass ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Cooling System ◽  
Thermal Power ◽  
Economic Effect ◽  
Thermal Conditions ◽  
Design Stage ◽  
Ground Source

The recognition of geological and thermal conditions of the rock mass in the case of designing a vertical borehole heat exchanger as the ground source for heat pump installations is a key issue affecting the efficiency of the heating/cooling system operation. This is especially important for large-sized buildings with a high demand for thermal power, which affects into the size of the ground source installation. The aim of the article is to indicate the difference in the obtained results concerning thermal calculations at the design stage of the brine/water heat pump installation with the vertical heat exchanger, in relation to the theoretical values of the rock mass thermal conductivity and the real (measured) values obtained during the thermal response test (TRT). For this purpose, calculations of thermal efficiency from one meter of the current rock mass were made, with particular emphasis on the change in the value of the thermal conductivity coefficient in the tested drilling profiles. Correspondingly, heat pump coefficients of performance (COP) were calculated, which allowed to analyze the influence of the over/undersizing phenomenon of the ground source on the technical parameters of the heat pump's operation and the economic effect of the investment.

The Influence of the Ash Addition from Thermal Power Plant on the Mechanical, Thermal and Dielectric Characteristics of Mortars

2018 ◽  
Vol 69 (8) ◽  
pp. 2040-2044
Author(s):  
Georgeta Velciu ◽  
Virgil Marinescu ◽  
Adriana Moanta ◽  
Ladislau Radermacher ◽  
Adriana Mariana Bors
Keyword(s):  
Thermal Conductivity ◽  
Fly Ash ◽  
Power Plant ◽  
Cement Mortar ◽  
Thermal Power ◽  
Total Content ◽  
Ash Content ◽  
Dielectric Losses ◽  
Dielectric Characteristics ◽  
Cement Mortars

The influence of fly ash adittion (90 % fraction [ 100 mm) on the cement mortar characteristics was studied. The XRD, XRF, SEM and FTIR determinations indicated that fly ash used has a hollow microstructure of microsphere and cenosphere whose total content in SiO2, Al2O3 and Fe2O3 is 88.63 % and that of CaO and MgO of 8.55 %. The mechanical, thermal and dielectric determinations made on mortar samples with content of fly ash in the 0-40 % range have highlighted fact that the mechanical strength of cement mortars is maximal at 20 %, the increase in fly ash content leads to a decrease in relative density and thermal conductivity as well as and to increased dielectric losses tgd.

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