Efficiency of ?shieldless? method of employing the cold of vapors in cryogenic vessels with a wide neck

Methods for raising the efficiency of cryobiological vessels with liquid nitrogen are proposed and realized and a method for calculating their heat shielding is developed and tested. Experimental and computational methods for evaluating the components of heat inflow taking into account the use of the cold of vapors are tested. The components of heat inflow along the neck, its plug, and vapors of the cryogenic component were determined experimentally from their thermal conductivity and the temperature gradient in the lowest cold layers of these elements. The decrease in the temperature gradient in each of the elements, including the screen-vacuum thermal insulation (SVTI), owing to the use of the cold of the vapors, determines the efficiency of the shieldless method of cooling. Thermal conductivity of the SVTI packet in different modifications of the Kh-34B cryogenic vessel was determined from data obtained on heat inflow through the elements and the evaporability of the vessel. The results indicated these paths for improving vessel efficiency: reducing the thermal conductivity of the neck material; development of more efficient compositions for SVTI; heat treatment of SVTI materials to reduce the contact heat transfer; and increasing the vacuum in SVTI layers.