Experimental test of tubular external molten salt receivers under non-steady state conditions Articles
- July 2019
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- In this work, a molten salt test loop to study the heat transfer under realistic operational conditions of solar power towers is described. The experimental installation is composed of a cylindrical molten salt tank, a pump to circulate the molten salt through a pipe and an induction heater to generate the heat flux, which is applied in a small rectangular region of the outer surface of the pipe. In solar power towers, the receiver tubes are subjected to a unilateral heat flux, because only one side of the pipe receives the solar radiation. The main advantage of using an induction heater to simulate this phenomenon is that a high heat flux can be applied to a delimited region of the external surface of the tube. Experiments where conducted to study the heat transfer process in a pipe circulating nitrate molten salt and subjected to a high and non- uniform heat flux. The temperature of the external wall of the tube was measured at different axial and angular positions varying the molten salt velocity. Besides, the tube bending due to the non-homogenous heat flux was measured using the images taken with an infrared camera. For a molten salt velocity of 0.78 m/s, the external wall temperature reached 700 °C at the front side of the pipe facing the inductor coil, while a temperature of 420 °C was measured at the rear side of the pipe. Additional experiments were done heating the empty tube in absence of molten salt flow, to simulate the start-up heating of the solar receiver. For this experiment, a temperature difference of approximately 340 ⁰C is observed between the front and rear side of the pipe, which leads to a higher tube bending than the previous experiments where the molten salt was flowing through the pipe.