英语翻译
With this type of heat exchanger,the counter current flow can be properly applied.If it is long enough,virtually all heat can be transferred from one to the other medium,i.e.,the outlet temperature of one medium is almost equal to the inflow temperature of the other medium.
The choice of which medium goes through the tubes and which around the tubes is determined by the degree of pollution.The inside of the tubes is generally accessible.After commissioning,the outside of the tubes cannot be reached very well.That is why the most polluting fluid (or gas) goes through the pipes and the least polluting around.