CN101434110B - Film wind-cooling and energy-saving control method of process for compounding rubber - Google Patents

Abstract

The invention relates to an air-cooled energy-saving control method for a rubber sheet in a rubber mixing process. The method comprises the following steps: (1) inputting working parameters of a draught fan such as a transmission speed m(rubber) of the rubber sheet, a cooling target temperature of the rubber sheet Tout and environmental state data; (2) according to the input parameters, calculating a heat balance equation and a heat transfer speed equation, namely firstly, calculating a heat discharge Q of the rubber sheet, and according to the flowing state of a jet flow of the draught fan calculating the average Nusselt number Nu of air cooling of the rubber sheet to obtain a corresponding heat transfer coefficient h, then calculating a heat Qw carried off by the gasification of moisture on the rubber sheet and heat Qh carried off by convection flow of air, according to the heat balance equation, calculating a heat transfer area F, and according to the heat transfer area F, calculating the number n of the draught fans needed for completing the cooling of the rubber sheet; and (3) according to the calculation result of the step (2), controlling the starting and the stopping of the draught fan. The method can reduce energy consumption, improve the service life of equipment and has low reconstruction cost.

Description

The film wind-cooling and energy-saving control method that is used for rubber mixing process

Technical field

The present invention relates to the film wind-cooling method of rubber processing process, especially a kind of film wind-cooling and energy-saving control method that is used for rubber mixing process.

Background technology

Rubber industry accounts for consequence in national economy.People's life be unable to do without rubber everywhere, and the little rubber of using always to us, sport footwear arrive giant tyre or the like greatly, make by rubber.

Compounding rubber is meant sneaks into the process of making the uniform elastomeric compound of quality in the rubber with various compounding ingredients, is one of most important technical process of fundamental sum in the rubber processing.Rubber (as natural rubber etc.) and various additive at first in banbury through mixing.Mixingly mainly carry out in banbury, elastomeric compound is discharged after supercooling, then through extruding, operations such as calendering, moulding, and then make various rubbers.

Mixer mixing adopts one section mixing and mixing two kinds of method of segmentation usually:

One section mixing is to begin once to finish mixingly to mixing finishing from enrich banburying chamber, and discharge sheet cooling to the tablet press machine is then parked standby.Adopt this compounding process, sizing material does not need sheet under the discharge, cooling to park in the middle of mixing process.

Segmentation is mixing to be divided into female refining and final mixing two steps.Twice mixing between, sizing material must and be parked through compressing tablet cooling, could carry out mixing then again.This method is the milling maternal rubber that carries out on banbury earlier beyond the sulphur removal sulphur, following sheet cooling and park certain hour after, drop into banbury more again and add sulphur mixing.Compounding process is the same with one section mixing method for the first time, and only the time is short slightly.

No matter adopt above-mentioned which kind of compounding process, the film cooling all is absolutely necessary.At present the film air conditioner that generally adopts can carry film, separant coating, air-cooled, dry, severing and production operation continuously such as folding, all be the air-cooled type of cooling of employing.Because air-cooled cooling heat transfer coefficient is lower, for guaranteeing cooling effect, existing equipment often adopts long cooling line, the on the high side and annual running of blower fan platform number, a large amount of electric energy of film cooling procedure consumption.Therefore design novel, energy-conservation film wind-cooling control method energy-conservation significant to rubber production.

Energy-conservation at the film cooling procedure, relevant in recent years both at home and abroad technology solves thinking and mainly adopts frequency converter timing, but frequency converter costs an arm and a leg, and the higher hamonic wave that decomposites has certain pollution to electrical network, so alternating frequency conversion technique is fewer in the rubber Application in Manufacturing Industry.The present domestic achievement that does not have as yet at rubber mixing process film wind-cooling and energy-saving control method aspect.

Summary of the invention

For the deficiency that energy consumption is big, service life is short, improvement cost is high of the film wind-cooling method that overcomes existing existing rubber processing process, the invention provides a kind of service life that can cut down the consumption of energy, improve equipment, the film wind-cooling and energy-saving control method that is used for rubber mixing process that improvement cost is low.

The technical solution adopted for the present invention to solve the technical problems is:

1), the running parameter, the transfer rate m of film of input blower fan a kind of film wind-cooling and energy-saving control method that is used for rubber mixing process may further comprise the steps: _Rubber, film cooling target temperature T _OutWith the ambient condition data, the running parameter of described blower fan comprises blower fan diameter D and air output

, described ambient condition data comprise environment temperature T _aAnd relative humidity

2), according to the parametric solution heat balance equation and the rate of heat transfer equation of described input, promptly at first calculate the thermal discharge Q of film, and solve the accurate number Nu of average Nu Saier of film wind-cooling according to the flow regime of fan jet flow, obtain corresponding heat transfer coefficient h; Calculate the heat Q that the moisture vaporization is taken away on the film again _wThe heat Q that takes away with convection flow of air _h

According to the heat balance equation:

Find the solution heat transfer area F:

Wherein, Δ T _mBe heat transfer temperature difference, h is air cooled convective heat-transfer coefficient, H _FilmBe the saturated humidity of air under the film surface temperature, H is the humidity of air, r _FilmThe latent heat of vaporization for water under the film surface temperature;

F=4lbn, l, b are respectively along the length of air-flow direction film, the short section radius of jet main body, b ≈ r ₀, r ₀Be the blower fan radius, n finishes the required blower fan platform number of film cooling;

Finishing the required blower fan platform of film cooling counts n and is:

n＝F/2lD (7)

Wherein D is the blower fan diameter;

3), according to step 2) result of calculation control the start and stop of blower fan.

As preferred a kind of scheme: in described step 2) in, the formula that calculates film thermal discharge Q is:

Q=c _RubberM _Rubber(T _In-T _Out) (1)

In the following formula (1): c _RubberBe the specific heat capacity of film, J/ (kgK); m _RubberBe the mass rate of film transport, kg/s; T _InBe the film inlet temperature, ℃; T _OutBe film cooling target temperature, ℃.

Further, in described step 2) in, the flow regime of fan jet flow is the turbulent flow circular jet, the process of calculating the heat transfer coefficient h of film wind-cooling cooling comprises:

The setting wall temperature is constant, physical data is constant, forms the dull and stereotyped accurate number of average Nu Saier that conducts heat of turbulent boundary layer and is tried to achieve by following formula:

The scope of application is 5 * 10 ⁵＜Re＜10 ⁷, Pr=0.6～2000;

In formula (2),

$\mathrm{Re}=\frac{\mathrm{ul}}{\mathrm{\υ}}$

Wherein, l is the film length along air-flow direction, and h is air cooled convective heat-transfer coefficient, and λ, ν, Pr are respectively qualitative temperature T _mThe thermal conductivity of following air, kinematic viscosity and Prandtl number; Qualitative temperature T _mBe boundary layer mean temperature, T _m=(T _a+ T _Film)/2; Film temperature T in film cooler _Film: T _Film=(T _In+ T _Out)/2;

Wind speed u is the muzzle velocity of blower fan, by blower fan diameter D and air output

Calculate:

$u=\frac{4\stackrel{\·}{V}}{\mathrm{\π}{D}^2}$

Through type (2) solves the accurate number Nu of average Nu Saier of film wind-cooling _{Turbulent flow}Afterwards, and then can get corresponding heat transfer coefficient h.

Or: in described step 2) in, the flow regime of fan jet flow is for plunderring flat plate laminar flow outward, and the process of calculating the heat transfer coefficient h of film wind-cooling cooling comprises:

Constant at wall temperature, when physical data is constant, forms the dull and stereotyped accurate number of average Nu Saier that conducts heat of laminar boundary layer and try to achieve by following formula:

Nu _{Laminar flow}=0.664Re ^1/2Pr ^1/3(3)

The scope of application is Re＜2 * 10 ⁵

In formula (3),

$\mathrm{Re}=\frac{\mathrm{ul}}{\mathrm{\υ}}$

Wherein, l is the film length along air-flow direction, and h is air cooled convective heat-transfer coefficient, and λ, ν, Pr are respectively qualitative temperature T _mThe thermal conductivity of following air, kinematic viscosity and Prandtl number; Qualitative temperature T _mBe boundary layer mean temperature, T _m=(T _a+ T _Film)/2; Film temperature T in film cooler _Film: T _Film=(T _In+ T _Out)/2;

Wind speed u is the muzzle velocity of blower fan, by blower fan diameter D and air output

Calculate:

$u=\frac{4\stackrel{\·}{V}}{\mathrm{\π}{D}^2}$

Through type (3) solves the accurate number Nu of average Nu Saier of film wind-cooling _{Laminar flow}Afterwards, and then can get corresponding heat transfer coefficient h.

As preferred another scheme: in described step 2) in, the heat Q that the moisture vaporization is taken away on the film calculated _wFormula be:

Q _w=k _HF (H _Film-H) r _Film(4)

Wherein, F is the contact area that heat, matter transmission take place between air and the film, H _FilmBe the saturated humidity of air under the film surface temperature, H is the humidity of air, r _FilmFor the latent heat of vaporization of water under the film surface temperature, for air-water system, h/k _H≈ 1.09kJ/ (kgK);

According to the characteristic of humid air,

r _Film=2500-2.35T _FilmWherein, r _FilmThe kJ/kg of unit, T _FilmUnit is ℃; Wherein, p _s(T _Film), p _s(T _a) be respectively the film temperature T _FilmWith air themperature T _aUnder Saturated water vapor pressure, p is an atmospheric pressure,

Relative humidity for air;

The empirical formula of water saturation vapour pressure is:

$\ln \left(p_s\right)=\frac{c_8}{T}+c_9+c_{10}T+c_{11}{T}^2+c_{12}{T}^3+c_{13}\ln \left(T\right)$

Pressure p in the formula _sUnit be Pa, the unit of temperature T is K, c ₈=-5800.2206, c ₉=1.3914993, c ₁₀=-0.04860239, c ₁₁=0.41764768 * 10 ^-4, c ₁₂=-0.14452093 * 10 ^-7, c ₁₃=6.5459673.

As preferred another kind of again scheme: in described step 2) in, the heat Q that convection flow of air is taken away calculated _hProcess be:

By the rate of heat transfer equation

Q _h＝h·F·ΔT _m (5)

Wherein, Δ T _mBe heat transfer temperature difference, h is the heat transfer coefficient of film wind-cooling cooling;

In film cooler, air and film cross-flow passes, its mean temperature difference Δ T _mCan draw by following formula:

Wherein, T _InBe film inlet temperature, T _OutBe film cooling target temperature, T _aBe environment temperature.

Technical conceive of the present invention is: under the different condition (under different blower fan running parameters, film transport speed, film cooling target temperature and the ambient condition) reach the required blower fan platform of film cooling count result of calculation will be as the input signal of blower motor controller, the start and stop of control blower fan realize the energy-conservation of rubber mixing process film wind-cooling.

By air mobility status in the film cooler bellows being carried out the CFD simulation as can be known, when fan jet flow enters in the stationary fluid, because the pulsation of turbulent flow, to entrainment on every side, stationary fluid enters jet, when the outside interlayer contacts with stationary fluid, stationary fluid also will obtain certain speed under the drive of stream motion; When jet ran into static solid boundary, diffusion also formed backflow.These all help the cooling of film, have therefore guaranteed the validity of result of calculation of the present invention.

Beneficial effect of the present invention is: 1, this method can reduce the energy consumption of rubber mixing process, improves the service life of equipment; 2, this method is simple and practical, and controllability is good, and improvement cost is low; 3, compare with conventional alternating frequency conversion technique, the cost performance height, easy to utilize.

Description of drawings

Fig. 1 is gas circle cross section submerged jets schematic diagrames.

Fig. 2 is cross-flow temperature difference correction factor figure (not mixing between the fluid).

Fig. 3 is the film wind-cooling and energy-saving control method figure of rubber mixing process.

The specific embodiment

Below in conjunction with accompanying drawing the present invention is further described.

With reference to Fig. 1～Fig. 3, a kind of film wind-cooling and energy-saving control method that is used for rubber mixing process may further comprise the steps:

1), input blower fan running parameter, film transport speed, film cooling target temperature, ambient condition data.

The data of input are only by blower fan diameter D, air output

, film transport speed m _Rubber, film cooling target temperature T _Out, environment temperature T _aAnd relative humidity

Six data are formed, i.e. the present invention need not the Energy Saving Control that placement process sensor gatherer process variable just can be realized the film cooling procedure.

2), find the solution heat balance equation and rate of heat transfer equation, obtain (or Various Seasonal) under the different air ambients and reach the required blower fan platform number of film cooling.

Specifically may further comprise the steps:

1. calculate film thermal discharge Q

Q=c _RubberM _Rubber(T _In-T _Out) (1)

In the formula: c _RubberBe the specific heat capacity of film, J/ (kgK); m _RubberBe the mass rate of film transport, kg/s; T _InBe the film inlet temperature, ℃; T _OutBe film cooling target temperature, ℃.For rubber mixing process, film transport mass rate m _Rubber, film cooling target temperature T _OutBe adjustable parameter, each other physical quantity on (1) formula equal sign the right are fixed value.

2. calculate the heat transfer coefficient h of film wind-cooling cooling

At first need determine the flow regime of blower fan air-supply.Freely to flood the turbulent flow circular jet is example, and jet enters in the stationary fluid in infinitely great space, because the pulsation of turbulent flow, entrainments on every side that stationary fluid enters jet, and the two blending travels forward.Entrainmenting the result with blending, is that the section of jet constantly enlarges, and flow velocity constantly reduces, and flow is then along Cheng Zengjia.Because the mobile of jet boundary place is a kind of compound movement of intermittence, so jet boundary is actually staggered irregular of forming.Jet is after forming stable nowed forming, and whole jet can be divided into following zone: begun by tube nozzle outlet, inside, the outer blending zone of expanding is called the jet boundary layer; Its external boundary contacts with stationary fluid, and inner boundary contacts with the core space of jet.The core of jet is not subjected to the influence of blending, still remains the zone of former muzzle velocity, is called the jet core district.Jet segment from the tube nozzle outlet to the core space between the terminal section is called the The initial segment L of jet ₀(see figure 1).

The spread angle alpha of main paragraph is a certain value, α=12 ° 15 ' and,, introduce outlet section momentum correction factor β in order to represent to export cross-sectional flow skewness degree.

$\mathrm{\&beta;}=\frac{\underset{A}{\&Integral;}\mathrm{\&rho;}{u}^2\mathrm{dA}}{\mathrm{\&rho;A}{\mathrm{<figure-callout\; id="0"\; label="v"\; filenames="H2008101216737E00021.png"\; state="\{\{state\}\}">v</figure-callout>}}_0^2}$

In the formula, v ₀Be the outlet mean velocity in section.According to experimental data, when velocity flow profile is even, β=1, $\stackrel{\&OverBar;}{x_o}=\frac{x_0}{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="H2008101216737E00021.png"\; state="\{\{state\}\}">r</figure-callout>}}_0}=0.6,$ $\stackrel{\&OverBar;}{L_o}=\frac{L_0}{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="H2008101216737E00021.png"\; state="\{\{state\}\}">r</figure-callout>}}_0}=12.4$ When velocity flow profile is inhomogeneous, $\stackrel{\&OverBar;}{x_o}=3.45,$ $\stackrel{\&OverBar;}{L_o}=6.3,$ The The initial segment contraction in length.

As shown in Figure 1, the short section radius of jet main body b=(x ₀+ L) tan α:

$\frac{\mathrm{<figure-callout\; id="0"\; label="b\; r"\; filenames="H2008101216737E00021.png"\; state="\{\{state\}\}">b</figure-callout>}}{r_{}}=\frac{(x_0+L)\tan \mathrm{\&alpha;}}{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="H2008101216737E00021.png"\; state="\{\{state\}\}">r</figure-callout>}}_0}=0.22\frac{x}{{\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="H2008101216737E00021.png"\; state="\{\{state\}\}">r</figure-callout>}}_0}=0.22\stackrel{\&OverBar;}{x}$

In this example, can think that the outlet wind speed profile is even, promptly

β＝1，x ₀＝0.6r ₀＝0.3d ₀＝0.3×0.56＝0.168m

L ₀＝12.4r ₀-x ₀＝12.4×0.56/2-0.168＝3304m

Because the width of film cooler bellows is generally less than fan jet flow The initial segment length L ₀=3.304m so the film cooling zone is positioned at the The initial segment of gas jet, can think that speed still keeps the muzzle velocity of blower fan, and jet has just arrived the bellows wall earlier when not arriving main paragraph, also can think b ≈ r ₀

Constant at wall temperature, when physical data is constant, forming the dull and stereotyped accurate number of average Nu Saier that conducts heat of turbulent boundary layer can be tried to achieve by following formula:

The scope of application is 5 * 10 ⁵＜Re＜10 ⁷, Pr=0.6～2000.

Constant at wall temperature, when physical data is constant, forming the dull and stereotyped accurate number of average Nu Saier that conducts heat of laminar boundary layer can be tried to achieve by following formula:

Nu _{Laminar flow}=0.664Re ^1/2Pr ^1/3(3)

The scope of application is Re＜2 * 10 ⁵When reynolds number Re between 2 * 10 ⁵～5 * 10 ⁵The transition flow state time, also adopt formula (3) to do conservative calculating.

In formula (2), formula (3),

$\mathrm{Nu}=\frac{\mathrm{hl}}{\mathrm{\&lambda;}},$ $\mathrm{Re}=\frac{\mathrm{ul}}{\mathrm{\&upsi;}}$

In the formula, l is flat board (the being film) length along air-flow direction, and h is air cooled convective heat-transfer coefficient, and λ, ν, Pr are respectively qualitative temperature T _mThe thermal conductivity of following air, kinematic viscosity and Prandtl number.Qualitative temperature T _mBe boundary layer mean temperature, T _m=(T _a+ T _Film)/2.Film temperature T in film cooler _FilmConstantly descend the mean value of desirable film out temperature, T with the transmission of film _Film=(T _In+ T _Out)/2.

According to the analysis of front as can be known, wind speed u can be similar to the muzzle velocity of getting blower fan, by blower fan diameter D and air output

Calculate:

$u=\frac{4\stackrel{\&CenterDot;}{V}}{\mathrm{\&pi;}{D}^2}$

Through type (2) or formula (3) solve after the accurate number Nu of average Nu Saier of film wind-cooling, and then can get corresponding heat transfer coefficient h, and the workload of computational process is less.

3. calculate the heat Q that the moisture vaporization is taken away on the film _w

Film before entering bellows coolings dip-coating interleaving agent, so the film cooling procedure is the process that a heat, matter transmission are carried out simultaneously.The mechanism of conducting heat has conduction, convection current and radiation; The mechanism of mass transfer has diffusion and convection current.When temperature is not too high, during flow velocity enough big (greater than 5m/s), thermal-radiating influence can be ignored, heat, matter transmission be all based on convection current, convection transfer rate h and mass tranfer coefficient k _HRatio and flow velocity irrelevant, only depend on the state of system character and gas phase.For air-water system, h/k _H≈ 1.09kJ/ (kgK).

Like this because the heat Q that film drying is taken away _wCan calculate by following formula:

Q _w=k _HF (H _Film-H) r _Film(4)

Wherein, F is the contact area that heat, matter transmission take place between air and the film, H _FilmBe the saturated humidity of air under the film surface temperature, H is the humidity of air, r _FilmThe latent heat of vaporization for water under the film surface temperature.

According to the characteristic of humid air,

r _Film=2500-2.35T _Film(kJ/kg, T _FilmUnit is ℃)

Wherein, p _s(T _Film), p _s(T _a) be respectively the film temperature T _FilmWith air themperature T _aUnder Saturated water vapor pressure, p is an atmospheric pressure, Relative humidity for air.

The empirical formula of water saturation vapour pressure is:

$\ln \left(p_s\right)=\frac{c_8}{T}+c_9+c_{10}T+c_{11}{T}^2+c_{12}{T}^3+c_{13}\ln \left(T\right)$

Pressure p in the formula _sUnit be Pa, the unit of temperature T is K, c ₈=-5800.2206, c ₉=1.3914993, c ₁₀=-0.04860239, c ₁₁=0.41764768 * 10 ^-4, c ₁₂=-0.14452093 * 10 ^-7, c ₁₃=6.5459673.

4. calculate the heat Q that convection flow of air is taken away _h

By the rate of heat transfer equation

Q _h＝h·F·ΔT _m (5)

Δ T wherein _mBe heat transfer temperature difference, 2. the heat transfer coefficient h of film wind-cooling cooling obtains in the step the.

In film cooler, air and film cross-flow passes, its mean temperature difference Δ T _mCan draw by following formula:

Δ T _m=φ Δ T _{M, adverse current}

Wherein φ is a temperature difference correction factor, Δ T _{M, adverse current}Be the mean temperature difference of counter-current flow,

Usually temperature difference correction factor φ can be expressed as:

φ＝f(R，P)

In the formula, R and P are nondimensional number, and its expression formula is:

$R=\frac{t_{h,\mathrm{in}}-t_{h,\mathrm{out}}}{t_{c,\mathrm{out}}-t_{c,\mathrm{in}}}$ $P=\frac{t_{c,\mathrm{out}}-t_{c,\mathrm{in}}}{t_{h,\mathrm{in}}-t_{c,\mathrm{in}}}$

Can check in φ by the temperature difference correction factor figure (Fig. 2) of cross-flow.

In film cooler, air is cold medium, and film is a thermal medium, air ports temperature approximately equal, i.e. t _{C, jn}=t _{C, out}, therefore

$P=\frac{t_{c,\mathrm{out}}-t_{c,\mathrm{in}}}{t_{h,\mathrm{in}}-t_{c,\mathrm{in}}}=0$

By consulting Fig. 2, can get temperature difference correction factor φ and equal 1.Therefore, for the heat transfer process of film cooler, its mean temperature difference Δ T _mFor:

5. calculate required blower fan platform and count n

According to the heat balance equation:

With formula (4) and formula (5) substitution following formula, find the solution heat transfer area F:

F=4lbn wherein, l, b are respectively along the length of air-flow direction film, the short section radius of jet main body, b ≈ r ₀(blower fan radius), n are to finish the required blower fan platform number of film cooling.

Like this, finishing the required blower fan platform of film cooling counts n and is:

n＝F/2lD (7)

Wherein D is the blower fan diameter.

3), utilizing under the different air ambients (or Various Seasonal) to reach the required blower fan platform of film cooling counts the start and stop that result of calculation is controlled blower fan, realizes the energy-conservation of rubber mixing process film wind-cooling.

Fig. 3 is the film wind-cooling and energy-saving control method figure of rubber mixing process.Under the different condition (under different blower fan running parameters, film transport speed, film cooling target temperature and the ambient condition) reach the required blower fan platform of film cooling count result of calculation will be as the input signal of blower motor controller, the start and stop of control blower fan realize the energy-conservation of rubber mixing process film wind-cooling.

By air mobility status in the film cooler bellows being carried out the CFD simulation as can be known, when fan jet flow enters in the stationary fluid, because the pulsation of turbulent flow, to entrainment on every side, stationary fluid enters jet, when the outside interlayer contacts with stationary fluid, stationary fluid also will obtain certain speed under the drive of stream motion; When jet ran into static solid boundary, diffusion also formed backflow.These all help the cooling of film, have therefore guaranteed the validity of result of calculation of the present invention.

Present embodiment adopts the suspension type film cooler, and concrete implementation step comprises:

(1) input blower fan running parameter, film transport speed, film cooling target temperature and ambient condition data

Blower fan diameter D=0.4m, air output $\stackrel{\&CenterDot;}{V}=4500m^3/h$ , film transport speed is a=30m/min, film cooling target temperature T _Out=55 ℃, environment temperature T _a=35 ℃, relative air humidity

With the film transport rate transition is the mass rate m of film transport _Rubber,

Density p=the 1150kg/m of elastomeric compound ³, film thickness δ=10mm, film width l=500mm.

(2) find the solution heat balance equation and rate of heat transfer equation, obtain (or Various Seasonal) under the different air ambients and reach the required blower fan platform number of film cooling.

The specific heat capacity of elastomeric compound film changes with temperature linearity in 50～100 ℃ of scopes, and the mean specific heat of therefore getting film when calculating the film thermal discharge gets final product c _Rubber=2.04kJ/kg-K.Film inlet temperature T _In=80 ℃.Then film thermal discharge Q is:

Q=c _RubberM _Rubber(T _In-T _Out)

＝2.04×2.875×(80-55)＝146.88kW

Under the atmospheric pressure, qualitative temperature T _m=(35+67.5)/2 thermal conductivity, kinematic viscosity and the Prandtl number of 51 ℃ of following air of ≈ are respectively λ=0.0283W/m-K, ν=17.95 * 10 ^-6m ²/ s, Pr=0.698.

Wind speed u can be similar to the muzzle velocity of getting blower fan, by blower fan diameter D and air output

Calculate:

$u=\frac{4\stackrel{\&CenterDot;}{V}}{\mathrm{\&pi;}{D}^2}=\frac{4\&times;4500/3600}{3.14\&times;0.4\&times;0.4}=9.95m/s$

Air is plunderred the Reynolds number of film outward $\mathrm{Re}=\frac{\mathrm{ul}}{\mathrm{\&upsi;}}=\frac{9.95\&times;500\&times;{10}^{-3}}{17.95\&times;{10}^{-6}}=2.77\&times;{10}^5<5\&times;{10}^5,$ So

Nu _{Laminar flow}=0.664Re ^1/2Pr ^1/3

＝0.664×(2.77×10 ⁵) ^1/2×0.698 ^1/3

＝310.12

Corresponding convective heat-transfer coefficient h is

h＝Nu·λ/l＝310.12×0.0283/0.5＝17.55W/m ²-K

Film surface temperature T _FilmGet the mean value of film out temperature, T _Film=(80+55)/and 2=67.5 ℃, corresponding Saturated water vapor pressure is p _s(67.5 ℃)=28338.0254Pa, the latent heat of vaporization r of water _Film=2500-2.35 * 67.5=2341.375kJ/kg, the saturated humidity H of air at this moment _FilmFor

Environment temperature Ta=35 ℃, relative humidity

The time, corresponding Saturated water vapor pressure is p _s(35 ℃)=5693.8419Pa, the humidity H of air is

For the Convective Heat Transfer of film cooler, its mean temperature difference Δ T _mFor:

According to formula (6), find the solution heat transfer area F:

$=\frac{146.88}{\frac{17.55\&times;30.83}{1000}+\frac{17.55}{1000\&times;1.09}\&times;(0.2415-0.0255)\&times;2341.375}$

$=16.9087m^2$

Like this, finishing the required blower fan platform of film cooling counts n and is:

$n=F/2\mathrm{lD}=\frac{16.9087}{2\&times;0.5\&times;0.4}=42.3$

Promptly under at present given condition, need 43 typhoon machines could realize required film cooling task.

Aforementioned calculation be summer hot moist ambient condition be issued to the required blower fan platform of film cooling and count result of calculation.As a comparison, can similarly calculate under the cold dry ambient condition, get environment temperature T winter _a=7 ℃, relative air humidity

The running parameter of blower fan and film is constant, realizes that the required blower fan platform number of film cooling will be reduced to 37, as following table.(3) utilize under the different air ambients (or Various Seasonal) to reach the required blower fan platform of film cooling and count the start and stop that result of calculation is controlled blower fan, realize the energy-conservation of rubber mixing process film wind-cooling.Table 1 is that the result of calculation of film cooling under two kinds of different air ambients compares, (D=0.4m, $\stackrel{\&CenterDot;}{V}=4500m^3/h,$ T _out＝55℃)

Table 1

The implementation case fall into a trap let it pass under two kinds of varying environment states (as table 1) realize that the required blower fan platform number of film cooling is respectively 43 and 37, the rated power of every typhoon machine is 250W, and then the blower fan power consumption will differ 1500W (=6 * 250) under two kinds of ambient conditions.Fig. 3 is the film wind-cooling and energy-saving control method figure of rubber mixing process.(under different blower fan running parameters, film transport speed, film ` cooling target temperature and the ambient condition) under the different condition reached the required blower fan platform of film cooling count the input signal of result of calculation as the blower motor controller, the start and stop of control blower fan, thus realized the energy-conservation of rubber mixing process film wind-cooling.

The foregoing description is used for the present invention that explains, rather than limits the invention, and in the protection domain of spirit of the present invention and claim, any modification and change to the present invention makes all fall into protection scope of the present invention.

Claims (6)

1. film wind-cooling and energy-saving control method that is used for rubber mixing process, it is characterized in that: described film wind-cooling and energy-saving control method may further comprise the steps:

1), the running parameter of input blower fan, the transfer rate m of film _Rubber, film cooling target temperature T _OutWith the ambient condition data, the running parameter of described blower fan comprises blower fan diameter D and air output V, and described ambient condition data comprise environment temperature T _aAnd relative humidity

2), according to the parametric solution heat balance equation and the rate of heat transfer equation of described input, promptly at first calculate the thermal discharge Q of film, and solve the accurate number Nu of average Nu Saier of film wind-cooling according to the flow regime of fan jet flow, obtain corresponding heat transfer coefficient h; Calculate the heat Q that the moisture vaporization is taken away on the film again _wThe heat Q that takes away with convection flow of air _h

According to the heat balance equation:

Find the solution heat transfer area F:

Wherein, Δ T _mBe heat transfer temperature difference, h is air cooled convective heat-transfer coefficient, H _FilmBe the saturated humidity of air under the film surface temperature, H is the humidity of air, r _FilmThe latent heat of vaporization for water under the film surface temperature;

F=4lbn, l, b are respectively along the length of air-flow direction film, the short section radius of jet main body, b ≈ r ₀, r ₀Be the blower fan radius, n finishes the required blower fan platform number of film cooling;

Finishing the required blower fan platform of film cooling counts n and is:

n＝F/2lD(7)

Wherein D is the blower fan diameter;

3), according to step 2) result of calculation control the start and stop of blower fan.

2. the film wind-cooling and energy-saving control method that is used for rubber mixing process as claimed in claim 1 is characterized in that: in described step 2) in, the formula that calculates film thermal discharge Q is:

Q=c _RubberM _Rubber(T _In-T _Out) (1)

In the following formula (1): c _RubberBe the specific heat capacity of film, J/ (kgK); m _RubberBe the mass rate of film transport, kg/s; T _InBe the film inlet temperature, ℃; T _OutBe film cooling target temperature, ℃.

3. the film wind-cooling and energy-saving control method that is used for rubber mixing process as claimed in claim 2 is characterized in that: in described step 2) in, the flow regime of fan jet flow is the turbulent flow circular jet, the process of calculating the heat transfer coefficient h of film wind-cooling cooling comprises:

The setting wall temperature is constant, physical data is constant, forms the dull and stereotyped accurate number of average Nu Saier that conducts heat of turbulent boundary layer and is tried to achieve by following formula:

The scope of application is 5 * 10 ⁵＜Re＜10 ⁷, Pr=0.6～2000;

In formula (2),

Wherein, l is the film length along air-flow direction, and h is air cooled convective heat-transfer coefficient, and λ, ν, Pr are respectively qualitative temperature T _mThe thermal conductivity of following air, kinematic viscosity and Prandtl number; Qualitative temperature T _mBe boundary layer mean temperature, T _m=(T _a+ T _Film)/2; Film temperature T in film cooler _Film: T _Film=(T _In+ T _Out)/2;

Wind speed u is the muzzle velocity of blower fan, is calculated by blower fan diameter D and air output V:

Through type (2) solves the accurate number Nu of average Nu Saier of film wind-cooling _{Turbulent flow}Afterwards, and then can get corresponding heat transfer coefficient h.

4. the film wind-cooling and energy-saving control method that is used for rubber mixing process as claimed in claim 2 is characterized in that: in described step 2) in, the flow regime of fan jet flow is for plunderring flat plate laminar flow outward, and the process of calculating the heat transfer coefficient h of film wind-cooling cooling comprises:

Constant at wall temperature, when physical data is constant, forms the dull and stereotyped accurate number of average Nu Saier that conducts heat of laminar boundary layer and try to achieve by following formula:

Nu _{Laminar flow}=0.664Re ^1/2Pr ^1/3(3)

The scope of application is Re＜2 * 10 ⁵

In formula (3),

Wherein, l is the film length along air-flow direction, and h is air cooled convective heat-transfer coefficient, and λ, ν, Pr are respectively qualitative temperature T _mThe thermal conductivity of following air, kinematic viscosity and Prandtl number; Qualitative temperature T _mBe boundary layer mean temperature, T _m=(T _a+ T _Film)/2; Film temperature T in film cooler _Film: T _Film=(T _In+ T _Out)/2;

Wind speed u is the muzzle velocity of blower fan, is calculated by blower fan diameter D and air output V:

Through type (3) solves the accurate number Nu of average Nu Saier of film wind-cooling _{Laminar flow}Afterwards, and then can get corresponding heat transfer coefficient h.

5. as claim 3 or the 4 described film wind-cooling and energy-saving control methods that are used for rubber mixing process, it is characterized in that: in described step 2) in, the heat Q that the moisture vaporization is taken away on the film calculated _wFormula be:

Q _w=k _HF (H _Film-H) r _Film(4)

Wherein, F is the contact area that heat, matter transmission take place between air and the film, H _FilmBe the saturated humidity of air under the film surface temperature, H is the humidity of air, r _FilmFor the latent heat of vaporization of water under the film surface temperature, for air-water system, h/k _H≈ 1.09kJ/ (kgK);

According to the characteristic of humid air,

r _Film=2500-2.35T _FilmWherein, r _FilmThe kJ/kg of unit, T _FilmUnit is ℃;

Wherein, p _s(T _Film), p _s(T _a) be respectively the film temperature T _FilmWith air themperature T _aUnder Saturated water vapor pressure, p is an atmospheric pressure,

Relative humidity for air;

The empirical formula of water saturation vapour pressure is:

Pressure p in the formula _sUnit be Pa, the unit of temperature T is K, c ₈=-5800.2206, c ₉=1.3914993, c ₁₀=-0.04860239, c ₁₁=0.41764768 * 10 ^-4, c ₁₂=0.14452093 * 10 ^-7, c ₁₃=6.5459673.

6. the film wind-cooling and energy-saving control method that is used for rubber mixing process as claimed in claim 5 is characterized in that: in described step 2) in, the heat Q that convection flow of air is taken away calculated _hProcess be:

Calculate Q by the rate of heat transfer equation _h:

Q _h＝h·F·ΔT _m (5)

Wherein, Δ T _mBe heat transfer temperature difference, h is the heat transfer coefficient of film wind-cooling cooling;

In film cooler, air and film cross-flow passes, its mean temperature difference Δ T _mCan draw by following formula:

Wherein, T _InBe film inlet temperature, T _OutBe film cooling target temperature, T _aBe environment temperature.

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