Numerical Simulation On Phase Change Energy Storage Performance Of Fatty Alcohols

Human survival and development can’t be separable from energy. Since the international energy crisis of the last century, energy storage technology plays an important role in energy conservation. The energy storage material is the basis of the energy storage technology. Phase change materials (PCMs) for which heat energy is stored in a latent heat form maily include three kinds:some hydration salts and some organic compounds (paraffin waxes, fatty acids, etc.) which are used for regular, middle temperature heat storage; molten salt for high temperature thermal storage. Hydrated salt which is easily accessible, low cost and high thermal storage density was once considered as the ideal phase change thermal storage medium, but this material has two major drawbacks:undercooling and crystallization. Organic phase change material, although its cost is higher than hydrated salt, has small undercooling and is relatively stable. Now research about organic phase change materials focuses on paraffin waxes and fatty acids, while reports about fatty alcohol are few.Based on this background, FLUENT is used in this paper to study the phase change energy storage performance of fatty alcohols which are non-paraffin organic PCMs. FLUENT is one of the most comprehensive, most widely used computational fluid dynamics (CFD) software. Solidification/melting model is based on the theory of the enthalpy method and is useful to solve the problem of mobile solid-liquid boundary. First, the solidification experiment of water in energy storage ball is carried out to verify the solidification/melting model. Second, the solidification process of five fatty alcohols in energy storage ball is numerical simulated. We find that n-decanol has the potential as PCM for conventional air conditioning conditions, because its phase-transition temperature is280.05K (about6.9℃), its latent heat of phase change is larger and its phase change time in energy storage ball is reasonable. The radius of the energy storage ball and the outer fluid temperature have great effect on the solidification time. We should choose appropriate radius and heat transfer temperature difference according to the actual situation.The model of storage tank which is close to the real size is also set up in this paper. The cold storage characteristics of storage tank are studied, and the effects of some parameters (such as the initial temperature, inlet temperature and inlet velocity) on energy storage process of storage tank are analyzed. The results show the inlet temperature has great effect on the energy storage process, while the effect of the initial temperature is small. Increasing the inlet velocity can speed up the cold storage process, but it also increases the power of the pump. So we should choose appropriate inlet velocity according to the actual situation.