Several classifications of cryogenic storage tanks

In simple terms, cryogenic storage tanks and cryogenic gas cylinders can be divided into three simple categories. First of all, it can be divided into cryogenic hot water and cryogenic storage tanks and high temperature hot water and cryogenic storage tanks according to the temperature of the working fluid in the pot. Secondly, according to the hot water circulation method, it can be divided into forced circulation (direct current) hot water cryogenic storage tank and natural circulation hot water cryogenic storage tank.
 
The forced circulation cryogenic storage tank is powered by the circulating water pump of the heating network to force water to flow and exchange heat in the heating surfaces of the cryogenic storage tank. This type of cryogenic storage tank usually does not have a drum, and the heating surface is composed of multiple sets of tube rows and headers. It has a compact structure, convenient manufacturing and installation, and low steel consumption. Its heating surface layout has co-current, counter-current and mixed-flow. Among them, the mixed-flow type has the advantages of both forward and reverse flow arrangements and avoids its shortcomings, that is, high utilization rate of the heating surface, good heat transfer efficiency, and prevention of cryogenic corrosion of the heating surface. It is an ideal and common layout.
 
In the natural circulation hot water cryogenic storage tank, the circulating flow of the water in the pot is mainly driven by the difference in the water column caused by the density of the water in the downcomer and the ascender. There are two types of this: 1. Natural circulation cryogenic storage tank with steam volume (using the drum for constant pressure). Such cryogenic storage tanks are usually high-temperature hot water and cryogenic storage tanks. It uses pot water to generate a small amount of steam, forming a steam space in the upper part of the cryogenic storage tank. On the one hand, this steam space is used to accommodate the expansion of the system water by heating, and acts as an expansion tank. On the other hand, it stabilizes the network system and prevents the water in the network system from vaporizing.
 
2. Natural circulation cryogenic tank with external expansion volume. In the operation of cryogenic storage tanks, an external expansion volume (such as an expansion tank) is required to contain the water that expands due to heating and to stabilize the network.