The symmetrical bi-cylindrical structure is a closedshell composed by two unclosed arch shell.
该结构是由两个对称非闭合大弧度圆弧横截面柱壳对接而成的闭合柱壳结构（简称“双圆弧柱壳”）；
2
Due to the closedshell, when conveying material can greatly improve the working conditions, prevent environmental pollution.
由于壳体封闭，在输送物料时可以显著改善工作条件，防止环境污染。
3
On the other hand, in order to meet the security needs of operation, the insulation must be closedshell, which will lead to difficulty in cooling coil.