Apparate- und Anlagentechnik

Finite-element modelling of low-temperature autofrettage of thick-walled tubes of the austenitic stainless steel AISI 304 L: Part I. Smooth thick-walled tubes

“…The latter is essentially based on the (repeated) application of a high internal pressure in a thick-walled tube, causing partial yielding of the tube from the inner bore into the cross section. After autofrettage, a beneficial residual triaxial stress state whose most important component is a tangential (hoop) compressive stress is retained in the inner part of the tube (see, e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14]).…”

“…In order to find the optimal autofrettage conditions rapidly and economically, it is necessary to perform stress and strain analyses theoretically. So far, many quantitative calculations have been pursued concerning the influences of autofrettage pressures, see, for example, [1,3,9,13], work hardening [3,4,6,8,9], yield-criterion comparison [12], reverse yielding [3,4,8] and strain rate [15] on the residual stresses and strains introduced by autofrettage in thick-walled tubes. Different mathematical treatments have been employed, such as analytic approaches [1,3,6,8,12,13], the finite-element (FE) method [16][17][18][19] and 0965-0393/98/010051+19$19.50 c 1998 IOP Publishing Ltd the boundary element method [20,21].…”

“…So far, many quantitative calculations have been pursued concerning the influences of autofrettage pressures, see, for example, [1,3,9,13], work hardening [3,4,6,8,9], yield-criterion comparison [12], reverse yielding [3,4,8] and strain rate [15] on the residual stresses and strains introduced by autofrettage in thick-walled tubes. Different mathematical treatments have been employed, such as analytic approaches [1,3,6,8,12,13], the finite-element (FE) method [16][17][18][19] and 0965-0393/98/010051+19$19.50 c 1998 IOP Publishing Ltd the boundary element method [20,21]. Furthermore, the enhancement of the fatigue resistance by the autofrettage technique has been studied by many investigators, see, for example [10,11,13,14,[22][23][24][25].…”

Catalytic Fixed‐Bed Reactors

“…Gas cooling of strongly exothermic reactions is not possible for industrial reactors, and even not advisable for small-diameter reactors used for kinetic experiments. In addition, to achieve the same heat transfer at the same temperature difference, the necessary pumping energy would exceed the respective value of liquids by a factor of 100 to 200 [23,30]. Gases are therefore used exclusively as flue gases to supply heat at high temperatures (as discussed in Section 10.1.3.3.3).…”

Fixed-Bed Reactors

“…The following equation has been derived for the evaluation of heat-transfer media without phase change [26]: where Q Á is the heat flow transferred by the heattransfer medium while its temperature increases by exactly DT c , N Á is the required pump power, and r, c p , and h are the density, specific heat capacity, and viscosity of the heat-transfer medium. For liquid heat-transfer media, the equation is derived from the pressure drop in a turbulently traversed, hydraulically smooth pipe.…”