NONISOTHERMAL RECEIVERS

The reradiation losses, inherent ro every thermal receiver, can be sig nificantly reduced by exposing the working fluid to monotonously incre asing irradiance and preventing energy exchange between parts of the r eceiver that are at different temperatures. In this way the highest te mperatures are reached only near the end of the working fluid's path. The improvement is much more pronounced for nonuniform as compared to uniform irradiance. For a Gaussian distribution of irradiance we calcu late improvements exceeding a factor of two for the efficiency at a gi ven temperature (0.8 of the peak stagnation temperature), and for the temperature at a given efficiency of 0.8. These results are independen t of the peak irradiance and of the width of the distribution. Even a coarse partitioning into two mutually isothermal parts can already pro duce a significant improvement over the totally isothermal receiver.