Comparative measurements and theoretical modelling of single- and double-stage heat pipe coupled solar cooking systems for high temperatures

The measured and calculated properties of three collector-based solar cooki ng systems are described. Two of them have a direct single-stage heat-pipe coupling between collector and oven plate. The first one is heated by a fla t-plate collector with 2.33 m(2) aperture area, while the second system is heated by one module of a Sydney vacuum-tube collector with 1.085 m(2) of a perture area. The third system with a double-stage thermal coupling is heat ed by two Sydney modules. Extensive outdoor measurements were conducted in Marburg (latitude 50.8 degrees N) proving the operational stability of the different heat pipe systems even on days with rapidly varying irradiance. O n clear days the shortest heat-up times from 40 to 99.5 degreesC for 5 kg w ater were 36, 32 and 17 min corresponding to an average thermal power of 58 0. 653 and 1220 W for the three systems, respectively. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.