Return bends, heat exchanger

Response time constant 403 Rkster. S. 6-13,655 Return bends, heat exchanger 505 Reversed flow 668 Reversibility, isothermal flow 143 Reversible adiabatic, isentropic flow 148... 

In the recleaning of the heat exchanger, several of the parallel, return-bend U-tubes (1 inch in diameter) were purposely pitched to assure a long section (approximately 10 feet) of trapped sodium. As would be expected from the previous estimate of the diffusion coefficient for water through concentrated caustic, the humid gas was not effective in removing these sodium pockets. The humid gas did successfully reclean the balance of the heat-exchanger circuits. In this phase of the operation, the maximum temperature rise did not exceed 130 °F. 

The double pipe, or fin-tube, exchanger is used when one liquid has a greater resistance to heat flow than anotlier or when the surface area is small. In such cases, the addition of fins to the inner pipe evens out the resistance to heat flow of the two liquids. As shown in Exhibit 6-8, the double pipe exchanger consists of a pipe within a pipe both pipes have a return bend at one end. The inner pipe is fitted with fins the outer pipe acts as the shell. The shell nozzles are mounted venically from the outer pipe, and the tube nozzles are directly welded to the inner pipe ends. The units are generally supponed horizontally by brackets at-... 

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