Features of design of thermal insulation of isothermal tanks
Features of the design of thermal insulation of isothermal tanks providing the restriction of evaporation speed of a product (in a percentage ratio from total amount per day) are discussed. Isothermal tanks are used for storage of various products at a constant negative temperature. They consist of an inner container containing liquefied gas, and an outer container. The gap between the inner and outer containers is filled with a heat-insulating material. In the inner container the maximum excessive pressure of the steam space over the tank product is provided. The heat protection of a bottom is made with due regard for the impact of the heat insulating material compression on the coefficient of its heat conductivity under the load action. The main requirement for the thermal insulation of a suspended floor is ensuring the absence of condensate on the external surface of the dome roof. Effective thicknesses of heat-insulation layers of various surfaces of the isothermal tank optimize the value of heat gain to the stored product, providing the optimum speed of evaporation. The condition that the condensate does not drop out from atmospheric air on external surfaces of the isothermal tank is thus observed. In the course of tanks designing it is necessary to take into account certain peculiarities: exclude the moisture formation in the gap between the walls and the possibility of soil freezing under the tank bottom; ensure the tightness in the tank and sufficient heat insulation of the tank lid. An example of design of thermal insulation is given.