Heat transfer in floating insulations for open cryogenic liquid containers

A transient heat transfer analysis of floating insulations in open cryogenic liquid containers is presented. The results are obtained in terms of three dimensionless parameters and are correlated to give the values of the cool down time, the total heat in-leak during cool down, the heat of sensible cooling of insulation and the steady state values of the temperature and heat flux at the exposed surface, as functions of the three parameters. The analysis facilitates the determination of the optimum insulation thickness for a given storage time. The utility of the analysis is demonstrated with a practical example of liquid nitrogen storage using expanded polystyrene beads as floating insulation.