INVESTIGATION OF COLD FILLING RECEIVER PANELS AND PIPING IN MOLTEN-NITRATE-SALT CENTRAL-RECEIVER SOLAR POWER-PLANTS

Cold filling refers to flowering a fluid through piping or tubes that are at temperatures below the fluid's freezing point. Since the piping and areas of the receiver in a molten-nitrate salt central-receiver s olar power plant must be electrically heated to maintain their tempera tures above the nitrate salt freezing point (430 degrees F, 221 degree s C), considerable energy could be used to maintain such temperatures during nightly shutdown and bad weather Experiments and analyses have been conducted to investigate cold filling receiver panels and piping as a way of reducing parasitic electrical power consumption and increa sing the availability of the plant. The two major concerns with cold f illing are (1) how far can the molten salt penetrate cold piping befor e freezing closed, and (2) what thermal stresses develop during the as sociated thermal shock. Cold fill experiments were conducted by flowin g molten salt at 550 degrees F (288 degrees C) through cold panels, ma nifolds, and piping to determine the feasibility of cold filling the r eceiver and piping. The transient thermal responses were measured and heat transfer coefficients were calculated from the data. Nondimension al analysis is presented which quantifies the thermal stresses in a pi pe or tube undergoing thermal shock. In addition, penetration distance s were calculated to determine the distance salt could flow in cold pi pes prior to freezing closed.