Solar assisted thermal energy storage systems have gained potential over last few years. The present study investigates the melting behaviour of PCM in an enclosure under two different boundary conditions representing outlet temperature pattern of a solar collector and is compared with results of a baseline case with isothermal heating. Output temperature of a coaxial evacuated tube for two typical months have been used in the study and with this coupling of solar collector output and PCM, thermal energy storage of a particular type of solar collector is assessed. Lauric acid, an organic phase change material is used for the analysis. Conduction and convection both being equally important in such problems, Bejan's heatline concept is invoked to the current problem to study the heat flow in phase change materials which imparts novelty of the presented work. 2-D numerical simulations are performed to imitate the phase change process in virtual environment applying “effective heat capacity” method. In the modelling of the problem, natural convection is handled by taking into consideration of Boussenisq approximation and the velocity in solid region is restricted by the Darcy law's source term. Comparison with baseline case shows, the output of February month delivers fastest melting. The utility of the evacuated tube is also seen here as it extracts 11.35 kJ and 7.33 kJ more solar energy which is stored in phase change material. Heatlines are not explored much to analyse the heat transfer in phase change material in previous studies and in the present work one such attempt is made which effectively illuminates the conduction and convection regime. Interestingly it shows the re-emergence of conduction process at a later point of time in liquid PCM. The visualization of heat flow also reveals that the liquid region acts as heat source for solid PCM.

在过去的几年中，太阳能辅助的热能存储系统已经获得了发展潜力。本研究调查了在两种不同的边界条件下PCM在外壳中的熔化行为，这些边界条件代表了太阳能收集器的出口温度模式，并与等温加热基准案例的结果进行了比较。在研究中使用了同轴抽空管的输出温度两个典型月份，并结合太阳能收集器输出和PCM，评估了特定类型太阳能收集器的热能存储量。月桂酸，一种有机相变材料，用于分析。在此类问题中，传导和对流都同样重要，Bejan' s的热线概念被用于当前的问题，以研究相变材料中的热流，这赋予了所介绍工作的新颖性。使用“有效热容”方法进行了二维数值模拟，以模拟虚拟环境中的相变过程。在问题的建模中，自然对流通过考虑Boussenisq逼近来处理，而固体区域中的速度受达西定律的源项限制。与基准案例相比，2月份的产出融化最快。真空管的效用在这里也可以看到，因为它可以提取11.35 kJ和7.33 kJ的更多的太阳能，这些太阳能存储在相变材料中。在先前的研究中，没有太多研究热线来分析相变材料中的热传递，并且在本工作中，进行了这样的尝试，其有效地阐明了传导和对流状态。有趣的是，它显示了稍后在液体PCM中重新出现的传导过程。热流的可视化还表明，液体区域充当固体PCM的热源。