重庆时时彩0_9数字规律|重庆时时彩的规律

管壳换热器英文文献和中文翻译

时间:2018-01-07 19:40来源:毕业论文
Multiple shell and tube heat exchangers in the series are employed to handle the temperature cross in the chemical process industries. Depending on the degree of temperature cross, certain number of heat exchangers (either E or F shell type)
Multiple shell and tube heat exchangers in the series are employed to handle the temperature cross in the chemical process industries. Depending on the degree of temperature cross, certain number of heat exchangers (either E or F shell type) need to be connected in series such that the temperature cross in each exchanger is within allow-able limit. Determination of the number of exchangers for the given terminal temperatures is essential during heat exchanger design phase. In this paper, using ?nite difference calculus, modeling has been done to calculate the number of shells required for both E and F shell cases. In addition, equations are developed to determine hot and cold ?uid temperature pro?les across all heat exchangers. Design procedure is illustrated with the help of a case study and the capital cost of both cases is compared. Issues related to E shell and F shells are also discussed.17091
© 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Keywords: Multiple shells in series; Heat exchanger design; Temperature cross; E shell; F shell; Finite difference
1. Introduction
There are several shell con?gurations designated as E, F, G, H,
J, K and X by the Tubular Exchanger Manufactures’ Associa-
tion Inc. These are described in detail in literature (Perry and
Green, 1997). E shell is a single-pass shell, and the number
of tube passes may be one or multiples of two (two is most
common). The shell side ?uid enters at one end and leaves
the other end of the opposite side. F shell is a two-pass shell
that has a longitudinal baf?e piding the shell into two com-
partments, shell ?uid enters at one compartment, travels the
entire length of the shell through that compartment, turns
around and ?ows through the another compartment of the
shell and ?nally leaves at the same end of the other side.
The number of tube passes for F shell may be two or mul- 源自六"维%论:文*网!加7位QQ324'9114 重庆时时彩的规律 www.mamitama.com
tiples of four (four is most common). Considering ?rst the
1–2 heat exchanger in Fig. 1(a), the tube ?uid in the ?rst tube
pass is in parallel with the shell ?uid, and in the second tube
pass the tube ?uid is in the counter ?ow with the shell ?uid.
Hence, the log mean temperature difference (LMTD), which
applies to either parallel or counter ?ow but not to a mix-
ture of both types, cannot be used to calculate the true oreffective mean temperature difference (EMTD) without cor-
rection. Similarly for 2–4 heat exchanger, as may be seen in
Fig. 1(b), contact between shell ?uid and tube ?uid is a mix-
ture of both parallel and counter ?ows and hence correction
factor is necessary to get the EMTD. This EMTD is generally
obtained by multiplying LMTD of true counter current ?ow
by a ?ow correction factor (FT). This factor is correlated in
terms of two dimensionless ratios, R and P by Nagle (1933)
and Underwood (1934). For instance, derivations can be found
in Kern (1997) and following assumptions were made dur-
ing the derivation: stream ?ows are at steady state, overall
heat transfer coef?cient and speci?c heat remain constant
throughout the exchanger, there is no phase change and heat
losses are negligible. Eqs. (1) and (2), Kern (1997) are used
to calculate FT for 1–2 exchanger and FT for 2–4 exchanger,
respectively.
For 1–2 heat exchangerNomenclature
a, b, c cost law coef?cients
bc cost of base line exchanger
A heat transfer area (m2)
AT heat transfer area of total exchangers (m2)
B arbitrary constant
C capital cost of total heat exchangers
cp speci?c heat of cold ?uid (kJ/kgK)
Cp speci?c heat of hot ?uid (kJ/kgK)
Cpn average speci?c heat of hot ?uid for nth
exchanger (kJ/kgK)
Eb f.o.b. price of total heat exchangers on January 管壳换热器英文文献和中文翻译:/a/fanyi/20180107/18633.html
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