Experimental analysis of fluid flow and PCM storage in a single-tube steam generator

Validated models to predict the behaviour of Latent Heat-Thermal Energy Storage (LH-TES) for steam generation under partial-load conditions are required to exploit their full potential with regard to design and operation. This article aims at overcoming the lack of data for experimental model validation for non-nominal flow control. It describes the implementation and results of experiments with a finned single-tube phase change material (PCM) steam generator which enables the simultaneous control of pressure and mass flow rate in the water/steam flow for the precise setting of operating points. Besides the condition of the storage, also the local condition of the heat transfer fluid (HTF) in the tubes is investigated based on pressure and temperature measurements. The test rig, containing a PCM which melts at approximately 133 °C, is operated between 1.4 bar and 6.7 bar, from 20 °C to 200 °C and with 1.26 kg/h to 4.30 kg/h. For improved quality of the results, the thermophysical data basis for the commercial phase change material PLUSICE A133 is extended. The results show that the storage peak power during charging and discharging is directly proportional to the mass flow rate. In partial-load operation of PCM steam generators with reduced mass flow rates, the produced steam mass flow rate as well as the pressure can be kept constant during the discharging process. • Extended operating range of LH-TES • Additional options for storage design • Power control for PCM steam generators • Determination of local flow conditions • Calculation of local heat transfer