## 1 Introduction
Therefore, introducing a promising and affordable technique for enhancing the thermal conductivity of PCMs can play a key role in improving their performance. Various techniques have been reported to date by different researchers to address the low thermal conductivity problem of PCMs. These included the addition of high-conductivity particles, using fins or extended surfaces, employing metal foams, using multiple PCMs and embedding heat pipes [20; 21; 22]. The addition of high-conductivity additives to PCMs, is one of the promising methods tried to date for improving their effective thermal conductivity. In modern building design, particularly in predicting energy performance of buildings, simulation programs are the basic tools. In case of planning the use of phase-variable materials, the correctness of the model selection is very important due to their variable properties. Presented in ref. [23], empirical research validates and compares six PCM models implemented in different building energy and hygothermal software (EnergyPlus, ESP-r and WUFI). In addition, a 2D model developed in COMSOL and another PCM model developed in MATLAB (CSMPCM model) are also validated and compared using data from two independent experimental studies with Nano-PCM embedded in drywall and shape-stabilized PCM behind the drywall construction material. Measurements of the thermal properties of internal cladding containing phase change material (PCM) [24; 25; 26] confirmed the occurrence of hysteresis during the processes of heating and cooling materials, when PCM melts and freezes. Further analysis of this phenomenon as well as the impact of its omission in the calculations included full-scale tests of partitions (our articles) and modifications to the calculation algorithm in the Energy Plus program [26]. The calculation results using the modified algorithm showed a high degree of compliance with the measurement results, which allows it to be used to analyze the possible effects of neglecting hysteresis while making simulation calculations of buildings. However, an important feature of PCMs, the thermal hysteresis phenomenon, has hardly been studied and included in building thermal simulations. Refs. [27; 28; 29] showed the importance of considering hysteresis in the numerical simulations to describe accurately the temperature evolution of PCMs. However, accurate control of the phase change of PCM is not easy to predict, for example, neglecting hysteresis or the speed of phase change processes reduces the accuracy of the simulation. In the last few years, many research centers have been working on the selection and adaptation of the model to take into account the hysteresis of phase-variable materials in numerical models. For instance, a research paper by ref. [1] presents a numerical study of the combined effects of the hysteresis temperature difference, peak melting temperature and thickness of a building envelope PCM-wall on its thermal performance in air-conditioning and non-air-conditioning conditions. The study was carried out considering complete melting-freezing daily cycles of the PCM in a climate exhibiting both hot and cold thermal discomfort.) In ref. [26], the authors propose a new software module for EnergyPlus(tm) that aims to simulate the hysteresis of PCMs during the phase change. The new module is tested by comparing simulation results with experimental tests done in a climatic chamber. A strong consistency between experimental and simulation results was obtained, with a discrepancy error of less than 1%. An original algorithm including hysteresis effects and the results from simulations were compared against experimental data and described in paper [30]. The algorithm was implemented in EnergyPlus TM and makes use of the energy management system (EMS) group, one of the high-level control methods available in EnergyPlus TM.