The role of thermal energy storagte in the energetic scene has been continuously increasing over the last years,since electrical utilities started to adopted different rates for "peak" and "off-peak" power consumption periods.As a result,several works have been devoted to modeling and predicting the transieent response of both sensible and latent heat storage devices,over a variety of geometry.Following the current trend,latent heat storage on encapsulated phase change material (PCM) was chosen as the object of the present work.Since the main feature is to take advantage of the high storage capacity offered by the latent heat,this work only deals with situations with small values of the Stefan number (Ste) which allow the solidification to be predicted by a quasi-stationary model.To obtain more general results,all the physical variables are arranged in non-dimensional grups,the influence of which on the response of the storage unit is evaluated in order to provide guidelines to the design and operation of those devices.Several assumptions are made with a view to maintain the model as simple as possible,without disregarding a carful reflection about its accuracy and impact on the reliability of the solution.The transient behavior of the storage unit is described by the evolution of the outlet temperature,as well as the thermal resistance ratio (TRR) through the discharge process.To ratify the model.some comparisons wiht previously published works are provided,showing not only qualitative but quantitative concurrency as well.
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