浮头式换热器英文论文1.docxVIP

Floating-head heat exchangers The present invention relates to an improvement in floating-head type heat exchangers and particularly to means for providing fluid-tight contact between a floating tube sheet and a head flange such exchangers.More particularly,this invention is concerned with a special packing joint which provides an effective seal between the shell side and the tube side and the tube side of a floating-head type heat exchanger. The use of so-called”shell and tube”heat exchangers has gained widespread commercial acceptance.Such exchangers are useful in transferring heat between two liquids,such as for example,in oil refining operation,or between a liquid and a vapor,such as for example in steam power plants. The relative thermal expansions or contraction which frequently result from differences in the temperatures of the fluids flowing through the tubes and the shell,or from differences in the materials of construction of the tubes and the shells, have led to the development and use of the so-called”floating-head”heat exchangers.In this type of exchanger the tubes are rigidly attached to a stationary tube sheet which is fixed relative to the shell of the exchanger at one end,and are attached to a floating tube sheet at the other end.Hence,in operation,slidable movement obtains between the floating tube sheet and the shell and other fixed parts as the expanding and contracting tubes cause movement of the floating tube sheet,and stress and strains which may otherwise cause wear and failure in the exchanger are therefore avoided. In the shell and tube heat exchangers, one fluid usually enters the shell at one end and discharges from the opposite side of the shell at the other end,or at the same end,depending upon whether a singer-pass or a double-pass arragement of tubes is employed.The other fluid flows through the tubes from one end and is discharged at the other end(single pass flow),or the fluid may flow through part of the tubes at one end,re-rout