  An accurate analysis of the conduction heat transfer in a cryogenic flask is
made and some useful formulae are derived. Taking into account the temperature
dependence of conductivity and tensile strength of the supporting rods for a
helium cryostat, these formulae may provide more exact results than the the
formulae based on simpler models. This allows the design of the supporting
elements of a liquid helium cryostat with minimum cross-section (for minimizing
the heat transfer)and proper mechanical resistance. Some examples of numerical
results and tables are also presented.
