Clearance Ds Db mDb c
where m and c are empirical constants and assume following values for different head type:
– fixed and U tube (0。01, 0。008), outside packed head (0。0, 0。038), split ring floating head (0。027, 0。0446), pull through floating head (0。009, 0。0862)。
Baffle spacing is calculated as:
where coefficients m and c are evaluated from figure given by Sinnot [15] for different baffle cuts, as fol- lows: 15% baffle cut (-6。710-8; 0。100067); 25% baffle cut (-4。510-8; 0。070045); 35% baffle cut (-4。410-8; 0。063044); 45% baffle cut (-3。410-8; 0。050034)。
The overall heat transfer coefficient is calculated as follows:
Cross-sectional area normal to flow direction is determined by:
Compare and check the absolute error,%,
a s between Uassumed and Ucalc as per following:
t
Uassumed Ucalc
where Pt is tube pitch and given by Pt = 1。25 d0。
Flow velocity for shell side can be obtained from:
If error is more than 0。5%, assume new U as
and go back to Eq。 (5) and recalculate
Reynolds number and Prandtl number for shell side can be calculated as:
everything until error reaches less than 0。5%。
When error is less than 0。5%, i。e。, Uassumed and Ucalc is very near to each other proceeding for further
calculations as follows:
The tube side pressure drop includes distributed
where Des is the shell hydraulic diameter and com- puted as:
– For triangular pitch:
pressure drops along the tube length and concen- trated pressure losses in elbows and in the inlet and outlet nozzles:
The shell side pressure drop is given by:
where fs is given by:
Kern’s formulation for segmental baffle shell-
and-tube exchanger is used for computing shell side heat transfer coefficient hs:
j K Re Pr 0。333
where b0 = 0。72 valid for Res < 40000。 Objective function
Total cost Ctot is taken as the objective function,
which includes capital investment (Ci), energy cost
(Ce), annual operating cost (Co) and total discounted
where coefficient jh is calculated from the figure given
by Sinnot [15] for different baffle cuts。
operating cost (Cod
The following approximate equation was used:
j h m Rec
Ctot Ci Cod (29)
Adopting Hall’s correlation, the capital invest- ment (Ci) is computed as a function of the exchanger surface area:
Ci a1 a2S a3 (30)
where a1 = 8000, a2 = 259。2 and a3 = 0。93 for ex- changer made with stainless steel for both shell and tubes。 模拟退火技术来设计英文文献和中文翻译(5):http://www.youerw.com/fanyi/lunwen_100221.html