In the near future, a significant increase in the number of air conditioning systems and an increase in their total electricity consumption are predicted . The use of latent-heat thermal energy storage (LHTES) in these systems will reduce the peak load on equipment. This will enable to establish systems of lower power and reduce energy costs in the presence of a double tariff rate .
For the creation and effective operation of the LHTES, it is necessary to calculate the key parameters of the system, like the charging-discharging time and the power of the storage. Because of the high nonlinearity of thermophysical parameters of phase change materials (PCM), such a calculation presents a complex computational problem for CFD programs . An alternative is to calculate using simplified mathematical models. This calculation significantly requires fewer computing resources, time and does not require the purchase of expensive licenses.
This article proposes a computer model for numerical calculations of heat fluxes in packed bed of capsules with PCM. A mathematical model of heat transfer in the capsule is based on finding a zero-dimensional solution of the Stefan problem with the influence of convective flows arising in the liquid phase. In Stefan's approach, the location of the mobile interface between the solid and liquid phases is unknown. To account for convective heat transfer in the liquid phase, the effective coefficient of thermal conductivity is calculated .
To describe the conditions of heat transfer between the coolant and the wall of the capsule, an experimental dependence was used . The calculation is reduced to obtaining the temperature of the coolant after passing one layer of the packed bed. The resulting temperature represents an input parameter for calculating the subsequent layer. This operation is rehearsed until the calculation is made for all layers of the packed bed.
The numerical calculation was carried out in the mathematical software Scilab. The results of calculating the temperature of the coolant after passing through the LHTES according to the proposed model are in good agreement with the experimental data for LHTES with spherical capsules filled with paraffin.
This work was supported by the ITMO University under the project “Improving the efficiency of energy systems by using thermal energy storage batteries” (620150).
 IEA, World Energy Outlook 2019, November 2019, ISBN 978-92-64-97300-8
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|Position of speaker||graduate student|
|Publication||IOP Conference Series: Earth and Environmental Science|
|Affiliation of speaker||ITMO University|