A Procedure for Calculating the Low-Temperature Installation Start-up Time

Abstract

For any technical installation, it is important to know the time taken for the system to reach its normal operating mode after it has been switched on. This is especially relevant for low-temperature installations, since after starting them up, the temperature conditions of all their components will alter significantly. Initially, the temperature of any structural component corresponds to the ambient temperature at which the installation was either manufactured or shut down after the previous startup. After the installation is switched on anew, its structural components are cooled, as the level of operating temperature should be significantly lower than the ambient temperature. Depending on the installation process design arrangement, its components must operate under different temperature conditions. Therefore, theoretical determination of the startup time (the time of transition from the initial temperature conditions to the operating state) for a low-temperature installation that includes a huge number of structural elements is an extremely difficult task. An attempt to develop a possible approach to attack the startup time calculation problem is made. In so doing, attention is paid to the installation components that are in direct contact with the cooled object. Structurally, they may have a simple geometrical shape (a rod) or a more complex one (involving a channel for passing a cold gas or liquid flow). To calculate the time taken for cooling these components, computer programs enabling one to solve the equations of unsteady heat transfer with the possibility of calculating the temperature fields throughout the component’s entire volume were used.