环形管 meaning in English

looping pipe
ring pipe
ring tube

Compression couplings - ring type nipples for brazed connection
管螺纹连接.钎焊连接环形管接头
Test method for thermal resistance and related properties of thermal insulations - part 3 : circular pipe apparatus
绝热材料的耐热和相关特性的试验方法.第3部分:环形管装置
In this paper , the transition from churn flow to annular flow for upward gas - liquid in vertical concentric annulus is studied and a transition model is developed by considering the structural feature of the concentric annulus and the flow characteristics for churn and annular flows in the concentric annulus
根据团状流及环状流的流动特性，并考虑同心环形管的结构特徵，建立了垂直同心环形管上升气液团状流向环状流转换的新的理论模型。