Hot water thermal energy stores have the potential to improve andextend the performance of many kinds of energy system. Waperaturestratification in the store is likely to affect the system'sefficiency. A basic but accurate computer model of the hot waterstore under various inlet flow conditions is a requisite means ofassesiing promising applications of hot water storage by systemcomputer simulation techniques.A microprocessor-controlled test facility has been constructed toevaluate the performance of a 3m3hot water store under a wide rangeof inlet flow conditions, using a temperature step input approach.Three types of inlet/outlet ports have been examined: horizontal,vertical and distributors. The results show that two distinctregions evolve within the store: a fully-mixed region adjacent tothe inlet port and a region of smooth 'plug-flow' in the remainingvolume of the store. The performance of the store is shown to bedefined by the initial depth of the fully-mixed region which in turnis seen to be closely related to the buoyancy and momentum fluxes ofthe inlet flow.The behAviour of the store and the evident correlations have enableda one-dimensional computer model of the store to be developed, takinginto account the turbulent mixing, vertical heat conduction and heatlosses to the surrounding areas. The model has been successfullyvalidated against the results from the step input experiments.The model has been integrated into a computer simulated centralheating system which incorporates a hot water store. Predictions havebeen made, using the simulation, of the energy savings which may beachieved with the use of storage in comparison to a conventionalsystem, and an assessment has been made of the economic viability ofthe application.
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