Shell and tube heat exchanger design specifications (reprint)
Read the number：(3036) Time：2014/3/9 11:05:09
Shell and tube heat exchanger design specifications (reprint)
Shell and tube heat exchangers are generally used for gas - liquid, liquid - liquid heat exchange between the condenser and heater used to produce, use very extensive. Shell and tube heat exchanger design generally comply with the following design specifications:
1, process design: in tube heat exchanger, what kind of fluid conditions laid down in the tube (or shell), the general principle of choice is: (1) unclean should go easy scaling fluid tube process, because the tube for easy cleaning; (2) corrosive fluids should take the tube to avoid discipline and housing as well as by corrosion, and cleaning, easy maintenance; (3) should take the high fluid pressure tube, so the housing while compression; (4) of toxic fluids should take the tube, so that the opportunity to reduce leakage; (5) should take the fluid to be cooled shell, easy to heat, enhancing the cooling effect; (6) saturated steam should take the shell, to facilitate the discharge of condensate and non-condensable gas and steam clean without polluting; (7) low flow or high viscosity fluids should go shell, because the role of the baffle can tailgate at low Reynolds number (Re> 100) under Turbulence can be achieved, but it can also be a multi-tube in the tube; (8) If the larger temperature difference between the two fluids, the fluid should go so that α large shell, so that the wall and the shell wall temperature decreases.
2, baffle design: heat exchanger baffles installed shell to improve convective heat transfer coefficient, in order to obtain good results, the baffles must be properly size and spacing. Lack of commonly used round-shaped baffle, arched incision is too large or too small, will have a flow of "dead zones" are not conducive to heat, see P431 Figure 6-30. Arcuate notch than the average height of the shell diameter of 0.15 to 0.45, 0.20 and 0.25 is often used two kinds. baffle spacing is too large, we can not guarantee vertical fluid flow through the tubes, so that the flow rate decreases, the tube convective heat transfer coefficient decreased; spacing is too small is not easy maintenance, the flow resistance is also large. General admission baffle spacing of shell diameter of 0.2 to 1.0 times, the baffle spacing used in our series of standards is: there are 150,300 fixed tube plate and 600mm of three; floating head has 150,200,300,480 and 600mm five.
3, the diameter and arrangement: the smaller the diameter of heat transfer, heat transfer area per unit volume greater. For clean fluids desirable small diameter, while easy to scale unclean or fluid pipe diameter should be larger. Using Φ19 × 2mm, Φ25 × 2mm, Φ25 × 2.5mm and other specifications of the column tube heat exchanger in the current standard. tube length selection should be considered fair use and easy to clean pipes, due to the length of the production of steel, mostly 6m, so the series has a standard of 1.5, 2 or 6m pipe length of four, of which the most common 3m and 6m . Besides housing the tube diameter D and length L should be appropriate proportion, generally L / D = 4 ~ 6 is appropriate.
The method of arrangement of the tube plate of the tube is used equilateral triangles, squares and square staggered three-line, see Figure 4-40. Arranged in an equilateral triangle is relatively compact, tube sheet utilization, high degree of tube fluid turbulence, convection coefficient, but more difficult tube cleaning; square inline tube easy to clean, but small convective heat transfer coefficient for in easy to scale fluid; square staggered somewhere in between. T pitch pipe and tube and tube plate connection method pipe arranged on the board. Welding method usually take t = 1.25do; while expanding law take t = (1.3 ~ 1.5) do, and t ≥ (do +6) mm.
4, the housing design: heat exchanger shell diameter should be equal to or slightly larger than the diameter of the tube plate, typically arranged in a method according to the diameter, the number of tubes and pipes, the method used to determine the figure. When the tube again repeated a few more calculations, refer to the series of standards or by estimating the primary shell diameter, designed to be used after the completion of the tube arrangement shown in Figure Law figure. To make the tube evenly to prevent fluid go "short", you can increase or decrease a certain number of tubes or arrange some levers.
Preliminary design, the following formula can be used to estimate the shell diameter:
D = t (nc-1) +2 b '
Where: D - shell diameter, m;
t - pipe center distance, m;
b '- the center line of the center of the outermost tube bundle to the housing wall distance, m, and generally b' = (1 ~ 1.5) do;
nc - number of tubes located at the center line of the tube bundle, the value calculated by the following formula:
When the tubes are arranged according to an equilateral triangle, nc = 1.1n0.5
When the tubes are arranged in a square, nc = 1.19n0.5
Where: n - the number of manifold heat exchanger.
According to the calculated diameter of the shell should be rounded up to the standards prescribed by the State
