ROBUSTNESS ANALYSIS OF VARIOUS APPROACHES TO MODELING OF THE PHASE CHANGE FRONT PROPAGATION

conference paper

English

Latent heat thermal energy storage (LHTES) has recently evolved into a promising approach for energy savings and pollution reduction. Phase change materials (PCMs) and the latent heat accompanying the phase change can be utilized to accumulate, store, are release the thermal energy when needed. The latent heat of the phase change allows for a storage of a relatively large amount of heat in a narrow temperature interval. The solid-liquid phase transition is widely utilized in such LHTES applications. Computer simulation tools are usually applied in the optimal design and real-time control of LHTES devices as the simulations are fast, relatively easy to perform and not expensive. Different numerical methods exist for modeling of heat transfer problems with phase changes. The methods can be assessed in several ways - accuracy, mathematical and programming complexity, demands for computational time and hardware, robustness etc. The wellknown enthalpy method, the effective heat capacity method and the temperature recovery method are widely utilized as they are simple and easy to implement. These so-called domain or front capturing methods suffer from a low accuracy in the vicinity of the phase interface and they are quite sensitive to the size of the time step. On the other hand, front tracking methods allow for very precise results near the phase interface, but they are more complex and computationally quite demanding. An important point is also the sensitivity and robustness of a method in relation to the thermal conditions and properties. In particular, the large heat flux at the boundary and the high thermal conductivity often cause numerical difficulties and instabilities. In practice, computer models have to be precise enough and sufficiently fast, especially in real-time applications. However, these two objectives are related in an opposite direction. The paper presents a robustness and sensitivity analysis of the above mentioned methods. The responses and numerical behavior of the methods are investigated and analyzed. The test problems with distinct grid spacing, sizes of time steps and thermophysical properties of phase change materials. The results show that the front tracking method can achieve higher accuracy for coarse mesh sizes than other tested methods. This characteristic compensates for higher computational demands of the front tracking method.

Latent heat, robustness analysis, simulation

MAUDER, T.; CHARVÁT, P.; KLIMEŠ, L.; ŠTĚTINA, J.

5. 11. 2017

The American Society of Mechanical Engineers

Tampa, Florida, USA

978-0-7918-5843-1

Proceedings of the International Mechanical Engineering Congress & Exposition

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