CN101338984A - Spiral traverse baffle shell type heat exchanger design method - Google Patents

Abstract

The invention relates to a design method for a screw deflector shell and tube exchanger. Firstly, the method for computing the pressure drop on the shell side of the screw deflector shell and tube exchanger and a coefficient of heat transfer can be obtained after the correlation of the drag produced from the sweep of hypothetical pipe columns by fluid and heat exchange is adjusted by referring to the adjustment factors relevant to geometric structure parameters of the screw deflector shell and tube exchanger. Subsequently, a method for designing the process and geometric parameters of the screw deflector shell and tube exchanger according to the known thermal parameters is proposed by adopting the Bell-Delawre design method which is widely used for designing a segmental baffle shell and tube exchanger based on the computing method. According to the design method provided by the invention, a heat exchange meeting the given heat load specification is designed more accurately and efficiently; the design efficiency and the accuracy are high; the performance of the designed heat exchanger is closer to the performance required by the design specification; the raw materials and the cost wastage are significantly reduced.

Description

A kind of method for designing of helical deflecting plate pipe and shell type heat exchanger

Technical field

The present invention relates to a kind of method for designing of heat exchanger, be specifically related to a kind of method for designing of helical deflecting plate pipe and shell type heat exchanger.

Background technology

Shell-and-tube heat exchanger is a kind of important equipment in the industry such as oil refining, chemical industry, environmental protection, the energy, electric power.Wherein use the historical the longest segmental baffle shell-and-tube heat exchanger that is.Though the segmental baffle shell-and-tube heat exchanger belongs to a kind of shell-and-tube heat exchanger of heat exchanger industry use amount maximum, because its design feature exists bigger along the journey pressure drop; Be prone to flow dead; Easily fouling and easily induce shortcoming such as heat exchanger tube vibration has the researcher constantly its structure to be improved for a long time always, but all fails to break away from its basic structure.

The beginning of the nineties, by Czech scientist Lutcha, Stehlik, Nemcansky and Kral etc. propose the screw baffle shell-and-tube shell-and-tube heat exchanger first, and it has been done the experimental study of system, studies show that helical deflecting plate pipe and shell type heat exchanger has that pressure drop is low, vibration is little, fouling is few, and advantage such as comprehensive heat exchange property is good.And researched and analysed of the influence of the main geometric parameters of helical baffles by experiment to its pressure drop and heat exchange property.But U.S. ABB AB has bought out its correlative study achievement subsequently, has all only provided very finite information for the detailed performance analysis and the method for designing of this heat exchanger in the document of publishing.

So far, the most ripe method for designing is the Bell-Delaware method at segmental baffle board heat exchangers in the shell-and-tube heat exchanger, and the detailed implementation process of this method generally sees among all kinds of heat exchanger handbooks.Based on this method, U.S.'s Heat Transfer Association (HTRI) has been developed relevant business software separately with Britain mass-and heat-transfer association (HTFS), is widely used in the heat exchanger industry, forms the trade monopoly status, has obtained huge trade benefit.

For the design of helical deflecting plate pipe and shell type heat exchanger, no matter there is no the data of literatures of publishing both at home and abroad, more do not see relevant business software is arranged, these are all given manufacturing and designing of helical deflecting plate pipe and shell type heat exchanger and apply and bring very big difficulty, have very important significance so sum up the effective design and calculation method tool of a cover.

Summary of the invention

The object of the present invention is to provide a kind of shell-side resistance and heat exchange correlation that uses the monoshell journey multitube pass spiral baffle shell-and-tube heat exchanger of single-phase medium and light pipe, and based on the Bell-Delaware method, the known procedures of giving chapter and verse parameter is carried out the method for designing of helical deflecting plate pipe and shell type heat exchanger.

For achieving the above object, the technical solution used in the present invention is:

1) determines thermic load according to known thermal parameter;

2) determine to restrain in the heat exchanger arrangement form according to corrosivity, viscosity, the fouling tendency of medium;

3) calculate logarithmic mean temperature difference (LMTD) according to tube bank arrangement form in heat exchanger inlet and outlet temperature and the heat exchanger, and calculate each required physical parameter;

4) estimate the overall heat-transfer coefficient of heat exchanger, and just calculate the required heat transfer area of heat exchanger according to known thermic load;

5) selected effective heat exchange length of pipe or heat exchanger shell internal diameter, if fixing effective pipe range then directly obtains required heat exchanger tube number according to the heat transfer area of just calculating, estimate the definite thereupon shell of stringing circular diameter footpath then, otherwise, if known shell internal diameter, then can estimate out the stringing circular diameter, can estimate the heat exchanger tube number according to the stringing circular diameter, last heat exchange area according to calculation just calculates required pipe range;

6) according to designing requirement primary election deflection plate helical angle and overlap joint ratio, calculate the shell-side flow velocity according to known parameters, pipe effluent speed and both sides Re number, subsequently, calculate geometric parameter and technological parameter that each modifying factor relates to, thereby determine heat exchange and pressure drop modifying factor;

7) according to the heat exchange and the pressure drop modifying factor that obtain, calculate the shell-side coefficient of heat transfer and the pressure drop of heat exchanger under current geometric parameter of primary election,

8) according to Gnielinski formula and the Weisbach-Darcy formula computer tube side coefficient of heat transfer and pressure drop;

9) calculate the thermic load that heat exchanger reached under the current design parameter, finish when this thermic load has remaining about 10-15% and the pressure drop of heat exchanger both sides all to satisfy to design when pressure drop allowable requires than the required thermic load of actual process, the heat exchanger under the current geometric parameter is both for satisfying the heat exchanger of technological requirement; Do not estimate overall heat-transfer coefficient if do not satisfy then to adjust, and repeating step (4)-(9) are until meeting the requirements.

The design of spiral baffle heat exchanger at present is with reference to experimental result mostly and the equipment in having used adopts the people to estimate and guess that the method for amplification reserve carries out in the past, design process efficient is low, the degree of accuracy is not high, lack reliable foundation, and usually undue amplification reserve guarantees to design and can satisfactoryly finish, cause designed heat exchanger performance and the required performance gap that reaches that goes out bigger, raw material and cost waste are more serious.And the method for designing in according to the present invention, can be more accurate and design the heat exchanger that satisfies given thermic load required by task efficiently, design efficiency and degree of accuracy height, designed heat exchanger performance are more pressed close to design objective and are required the performance that reaches, significantly reduce the waste of raw material and cost.

The specific embodiment

The present invention sums up the shell-side resistance and the heat exchange correlation of the monoshell journey multitube pass spiral baffle shell-and-tube heat exchanger that uses single-phase medium and light pipe, and based on the Bell-Delaware method, the known procedures of giving chapter and verse parameter is carried out the method for the technology geometric parameter design of helical deflecting plate pipe and shell type heat exchanger.

As follows according to resistance and heat exchange correlation that data of literatures is summed up:

Helical deflecting plate pipe and shell type heat exchanger shell-side average N u number:

${\mathrm{Nu}}_s=0.62\×(0.3+\sqrt{{\mathrm{Nu}}_{\mathrm{lam}}^2+{\mathrm{Nu}}_{\mathrm{turb}}^2})\×Y_2\×Y_3\×Y_4\×Y_7\×Y_8\×Y_9\×Y_{10}$

Helical deflecting plate pipe and shell type heat exchanger shell-side average heat transfer coefficient:

$h_s=\frac{{\mathrm{Nu}}_s\×{\mathrm{\λ}}_s}{l}$

Wherein:

Nu _lam＝0.664Re ^0.5Pr ^0.33

${\mathrm{Nu}}_{\mathrm{turb}}=\frac{0.037{\mathrm{Re}}^{0.7}\mathrm{Pr}}{1+2.433{\mathrm{Re}}^{-0.1}({\mathrm{Pr}}^{0.67}-1)}$

$l=\frac{{\mathrm{\πd}}_2}{2},$

d ₂---external diameter of pipe/mm

λ _s---the thermal conductivity factor/W/ (m K) of shell fluid;

The above-mentioned formula scope of application: 10＜Re＜10 ⁶, 10＜Pr＜10 ³, n _Re＞10, helical angle is between the 5-45 degree.

Wherein: n _Rc=n _Rp(n _p-1), n _RpBe pipe row number, n _pBe number of baffles.

Helical deflecting plate pipe and shell type heat exchanger shell-side resistance correlation:

The fluid spiral flow is not crossed the pressure drop of tube bank when not considering by-pass under the unit pitch:

${\mathrm{\ΔP}}_{t0}^1={2\mathrm{\λ}}_{22}{n}_r^1{\mathrm{\ρ}}_2{u}_2^2{Z}_2{Z}_6{Z}_7$

When considering that bypass is flowed, one-piece auger baffle shell-and-tube heat exchanger tube bank district's pressure drop:

${\mathrm{\ΔP}}_{t0}={\mathrm{\ΔP}}_{t0}^1\frac{l_{t0}}{H_s}{Z}_3$

The pressure drop of turnover oral region:

${\mathrm{\ΔP}}_{\mathrm{tn}}={\mathrm{\ΔP}}_{t0}^1{Z}_5{Z}_3$

Importing and exporting adapter droop loss size is:

ΔP _nozzle＝1.5×0.5×ρv ²

Heat exchanger shell-side overall presure drop:

ΔP _all＝ΔP _tn+ΔP _nozzle+ΔP _t0

Wherein: n _r ¹---the horizontal pipe row number of plunderring of fluid;

λ ₂₂---the horizontal ideal tube bank resistance factor of plunderring of fluid;

H _s---pitch/mm;

l _To---effective pipe range/mm;

V---take over inner fluid speed/m/s;

ρ---fluid density/kg/m ³

Y series is the modifying factor of heat exchanging coefficient in the above-mentioned formula, and Z series is the modifying factor to pressure drop.

Wherein: Y ₂, Z ₂Be hot rerum natura factor of influence;

Y ₃Extend to the factor of influence of tube bank for single tube;

Y ₄Laminar flow subinverse thermograde modifying factor; The Re number was not considered greater than 100 o'clock, is taken as 1;

Y ₇, Z ₃Tube bank and housing by-pass modifying factor;

Y ₈, Z ₅Import and export baffle(s) spacing and influence modifying factor;

Y ₉, Z ₆The crossing current characteristic variations factor; Only relevant with spiral angle;

Y ₁₀, Z ₇The turbulent flow enhancer; Only relevant with spiral angle.

Its detailed process is as follows:

1) determines thermic load according to known thermal parameter;

2) determine to restrain in the heat exchanger arrangement form according to corrosivity, viscosity, the fouling tendency of medium;

3) calculate logarithmic mean temperature difference (LMTD) according to tube bank arrangement form in heat exchanger inlet and outlet temperature and the heat exchanger, and calculate each required physical parameter;

4) estimate the overall heat-transfer coefficient of heat exchanger, and just calculate the required heat transfer area of heat exchanger according to known thermic load;

5) selected effective heat exchange length of pipe or heat exchanger shell internal diameter, if fixing effective pipe range then directly obtains required heat exchanger tube number according to the heat transfer area of just calculating, estimate the definite thereupon shell of stringing circular diameter footpath then, otherwise, if known shell internal diameter, then can estimate out the stringing circular diameter, can estimate the heat exchanger tube number according to the stringing circular diameter, last heat exchange area according to calculation just calculates required pipe range;

6) according to designing requirement primary election deflection plate helical angle and overlap joint ratio, calculate the shell-side flow velocity according to known parameters, pipe effluent speed and both sides Re number, subsequently, calculate geometric parameter and technological parameter that each modifying factor relates to, thereby determine heat exchange and pressure drop modifying factor;

7) according to the heat exchange and the pressure drop modifying factor that obtain, calculate the shell-side coefficient of heat transfer and the pressure drop of heat exchanger under current geometric parameter of primary election,

8) according to Gnielinski formula and the Weisbach-Darcy formula computer tube side coefficient of heat transfer and pressure drop;

9) calculate the thermic load that heat exchanger reached under the current design parameter, finish when this thermic load has remaining about 10-15% and the pressure drop of heat exchanger both sides all to satisfy to design when pressure drop allowable requires than the required thermic load of actual process, the heat exchanger under the current geometric parameter is both for satisfying the heat exchanger of technological requirement; Do not estimate overall heat-transfer coefficient if do not satisfy then to adjust, and repeating step (4)-(9) are until meeting the requirements.

When this method for designing being checked checking, five helical deflecting plate pipe and shell type heat exchangers having selected the process measuring for use are as example, design and the prediction of resistance and heat exchange property according to the procedure parameter of experiment measuring, the actual geometric parameter of result of calculation and heat exchanger and actual measurement pressure drop and the coefficient of heat transfer are compared, wherein the error of calculation of pressure drop and overall heat-transfer coefficient is within 20-30%, and its precision satisfies requirement of engineering fully.

Claims (1)

1, a kind of method for designing of helical deflecting plate pipe and shell type heat exchanger is characterized in that:

1) determines thermic load according to known thermal parameter;

2) determine to restrain in the heat exchanger arrangement form according to corrosivity, viscosity, the fouling tendency of medium;

3) calculate logarithmic mean temperature difference (LMTD) according to tube bank arrangement form in heat exchanger inlet and outlet temperature and the heat exchanger, and calculate each required physical parameter;

4) estimate the overall heat-transfer coefficient of heat exchanger, and just calculate the required heat transfer area of heat exchanger according to known thermic load;

5) selected effective heat exchange length of pipe or heat exchanger shell internal diameter, if fixing effective pipe range then directly obtains required heat exchanger tube number according to the heat transfer area of just calculating, estimate the definite thereupon shell of stringing circular diameter footpath then, otherwise, if known shell internal diameter, then can estimate out the stringing circular diameter, can estimate the heat exchanger tube number according to the stringing circular diameter, last heat exchange area according to calculation just calculates required pipe range;

6) according to designing requirement primary election deflection plate helical angle and overlap joint ratio, calculate the shell-side flow velocity according to known parameters, pipe effluent speed and both sides Re number, subsequently, calculate geometric parameter and technological parameter that each modifying factor relates to, thereby determine heat exchange and pressure drop modifying factor;

7) according to the heat exchange and the pressure drop modifying factor that obtain, calculate the shell-side coefficient of heat transfer and the pressure drop of heat exchanger under current geometric parameter of primary election,

8) according to Gnielinski formula and the Weisbach-Darcy formula computer tube side coefficient of heat transfer and pressure drop;

9) calculate the thermic load that heat exchanger reached under the current design parameter, finish when this thermic load has remaining about 10-15% and the pressure drop of heat exchanger both sides all to satisfy to design when pressure drop allowable requires than the required thermic load of actual process, the heat exchanger under the current geometric parameter is both for satisfying the heat exchanger of technological requirement; Do not estimate overall heat-transfer coefficient if do not satisfy then to adjust, and repeating step (4)-(9) are until meeting the requirements.