The way the air flow when drying meat and fish products

 

(57) Abstract:

The invention relates to methods of distribution and is intended for use in the meat industry for drying of smoked sausage and other meat products, for curing salami, and fisheries for curing fish products. The way the air flow when drying meat and fish products includes the use of the reverse air flow, the effect of laying supplied to the supply flow. The air supply to the zone of the processed product is carried out from bottom to top. This nastilanie carried out at a distance equal to half the height of the working area of the drying chamber. Moreover, the air supply is carried out using one-sided pyramidal nozzle having a vertical wall by laying jets and an inclined wall from the side of the working area. The technical result is to increase the quality of processed food products and reducing energy consumption. 3 C.p. f-crystals, 4 Il., table 1.

The invention relates to methods of distribution and is intended for use in the meat industry for drying son the industry for drying fish products.

There is a method of distribution providing for the distribution of supply air through distribution channels with flat nozzles (Fig. 1). This method is used in the drying chambers, the chambers packaging and storage of meat and dairy products, etc. In this method, the distribution of the supply air passes through channels, placed in the upper zone of the cameras, on the longitudinal walls of the cells or in the lower zone [1]. The method is simple devices for air distribution, but has the following disadvantages:

- uses imperfect view of the diffuser is a flat nozzle. Flat nozzle, made in the form of rectangular holes sizes from 200x300 to h mm, round holes with a diameter of 50-100 mm and cracks from h to 50x50 mm, etc. may not provide the necessary range of inlet jets due to the fact that the reduction in air velocity occurs at the beginning of the working area, not reaching her mid;

- due to the small range of inlet jets, there is a considerable non-uniformity of the velocity distribution of the air flow in the working area of drying chambers, which reaches 50 -60%;

- due to insufficient range supply air jets emerging from plastig fan, bypassing the working area and not participating in the processes of heat and mass transfer with the product, i.e. not all of the air involved in the processes of heat and mass transfer with the product. Therefore, partially this method of distribution is idle and therefore has a wasteful expenditure of energy;

- due to limited range of inlet jets and uneven conditions of heat exchange and mass transfer between air and product increases the duration of the drying process compared to the duration of the recommended technology standards, which reduces the quality of the processed products due to the formation of mold on the surface in stagnant areas of the chamber, where there is no movement of air;

- provides focused hood exhaust air, which also contributes to the creation of unequal conditions for the distribution of air in the working area of drying chambers and, consequently, the formation of mold on the product.

There is a method of air distribution through the upper perforated channels, ceilings and panels [2]. Perforated channels (Fig.2) use as diffusers perforated panel, in which preusmeravanje panel does not exceed 5 - 10%, that is, the area occupied by the holes is only 5-10% of the total area vozduhorazdelenija panel, which is several times less than in the previous method. The reduction factor screening is achieved through the use of a large number of holes of small diameter, which allows you to submit fresh air in the form of a single air flow (merger inlet jets occurs at a distance not exceeding 5 hole diameters). Supplied air flow is uniform distribution of the air velocity at any cross-section. But he has a different speed on the upper and lower level of product placement in height. Therefore, this method is not suitable for the distribution of air in the drying chambers, as the distance between the upper and lower level working area is 2 meters or more. The degree of uneven distribution of the air velocity should not exceed technological conditions of 30%, i.e., the speed in the area of product must be in the range of 0.15-0.2 m/s

When used in drying chambers for smoked sausages way air distribution through the upper perforated channels product, located on the top level of the working area, procesoare mold. Furthermore, the method provides focused hood exhaust air, which also contributes to the uneven distribution of the air velocity in the zone of the product and the formation of marriage.

The closest in technical essence and the problem at hand is how to distribute the air in the drying chambers, using a reverse flow of air created by the conical or cylindrical nozzles [3].

The method comprises the air supply through the two inlet air distributing channel (Fig. 3): the left and right placed in the upper part of the chamber along its longitudinal walls and equipped with a conical or cylindrical nozzles, installed evenly along the length of the channels. In the middle of the upper part of the chamber is provided an exhaust air channel. As the air in the exhaust duct using a flat nozzle rectangular, slit-like or round shape, diffusers and other Exhaust channel is placed directly over the area of product that provides a uniform hood exhaust air throughout the area, and not focused, as provided in the above ways.

This method provides the advantage is x walls, netilas on them, and then on the floor of the chamber. When nastilanie is the formation and merging of separate inlet streams, interaction, tightness and alignment speed of the resulting air flow (left and right) is not in the working area, and in the spaces between the longitudinal wall and a work area. Inlet stream in the form of return flows are included in the product area from the bottom and moving upwards. In this way, the flow is affected only by the resistance of the product. The fall velocity of the air in the working area does not exceed 0.05 m/s Therefore, the height of placement of the product equal to 2 m (height of the floor of the truck), the fall velocity corresponds to the technological standards.

The method involves the use of bevel and cylindrical nozzles with different values of the diameter and height of the nozzle, and a step of placing the nozzles along the length of the channels. In kilns of various firms are the most common conical nozzle with the diameter of the outlet d0=30-80 mm with step of placing nozzles t0= 180-400 mm Such indicators have a significant impact on the energy consumption required for the distribution of air in the working area.

As a result of the research we set the -2,2 kWh per 1 kg of dry product and are assessed as significant compared with other methods.

Thus, the distribution used in this method has advantages over the above-described method that uses the most effective type of diffuser, made in the form of a conical nozzle, providing the greatest range of the jets, while the nozzles are evenly placed along the length of the channel, provide the airflow to the product with uniformly distributed parameters, and flow by way of the return flow maintains the predetermined air speed in the product area, within the limits of technological conditions. All of the feed air stream is included in the product area and performs the necessary conditions of heat exchange and mass transfer on the product surface that promotes uniform drying conditions. Provides uniform hood exhaust moist air from the zone of the product throughout its length due to the presence of the exhaust channel over the Central part of the product area with evenly distributed in its distributors for fence humidified air.

The disadvantages of this method are

- increased energy consumption to provide fans due to the necessity of creation of air on the products, that has a negative effect on the quality of the processed products;

- increased the length of the air flow, which is caused by the fact that the principle of this method of distribution is based on the need to ensure conditions of a forced air circulation over the entire height of the working area. In this regard, the necessary length of the air flow is the sum of the lengths of the three sites

Xp=h+0.5 bR. C+hR. C,

where Xp- full length air flow, m;

h - the height of the suspension channels, m;

bR. C- the width of the working area, m;

bR. C- height of the working area, m;

This method has not only increased power consumption for fan operation. At the same time increase the cost of heat and cold on the drying of the product, since the increase in power consumption for fan operation occurs not only due to higher pressure losses by the use of tapered nozzles, but also due to increased air flow caused by the need to create increased air velocity at the exit of the nozzles.

The increased turbulence of the air surrounding the surface of the product, in most cases, causes solidification of the surface, brasaetsa uneven moisture distribution across the section of sausages. With the wet layer is on the inside of the loaf, which degrades the quality of the product and reduces the shelf.

To create the claimed invention is to improve the quality of processed food products and reducing energy consumption.

This goal is achieved by the fact that in the proposed method, including the use of the reverse air flow, ensure uniform conditions of its distribution in the area of the processed product, the effect of laying supplied inlet jets, the air supply to the zone of the processed product is carried out bottom-up, and nastilanie inlet jets on the walls carried out at a distance characterizing the length of the air flow from the outlet nozzle before entering the working area of the drying chamber, while the air supply is carried out using one-sided pyramidal nozzle, having a vertical wall by laying jets and an inclined wall from the side of the working area (to provide more reliable conditions of laying), while nastilanie air stream is carried out at a distance equal to the hollow thread force supplied by the fan in the present invention,

hR. C- height of the working area.

Under these conditions, fresh air pots, there is no need to install conical nozzles, providing the greatest range of inlet jets. We offer air supply, made in the form of pyramidal nozzle with one-sided bevel of the side wall on one side and a vertical wall on the other side, allowing the preload inlet jet and the reduction of area of the touch of the jet with the vertical wall of the chamber to ensure more reliable conditions of laying.

Furthermore, the method involves the use of unilateral pyramidal nozzle with geometrical parameters: the width of the outlet nozzle b0= 40-50 mm, the width of the inlet nozzle b=2b0the height of the nozzle hwith=2,4-2,5 b0the length of the nozzle Lwith=hwithstep placement of nozzles along the length of the inlet channels t0=4,8-5,0 b0.

The method involves in the exhaust duct, round holes with a diameter of dwit.corresponding to the equivalent diameter of the inlet nozzle, i.e., dwith= dE.; kolichestvennyh in one a number of nwith=2; pitch holes twith= t0. Furthermore, the method provides for the suspension height of channels: supply hCR=0,5 hR. C, exhaust hwith=hR. C+(0,10-0,15)m

The claimed method allows the air in the working area preemptive reverse laminar flow, moving from bottom to top in one direction (without twists) through the entire height of the working area to the openings of the exhaust channel.

Diagram of apparatus for carrying out the proposed method of air flow in the return flow pyramidal nozzles shown in Fig.4.

The device includes a fan 1,2, air conditioning 3, inlet channels 4,5, pyramidal nozzle 6, the drying chamber 7, the cart product 8, the exhaust channel 9.

The device operates as follows. Supply air fan 1,2 from the air conditioner 3 is fed into the left inlet channel 4 and the right air supply channel 5 and through pyramidal nozzle 6, evenly placed along the length of the supply channel, in the form of individual jets is supplied into the drying chamber 7. Jet laid on the longitudinal walls of the drying chamber with the left and right sides. When nastilanie merge jets, oppression, interaction and formirovanie from the outlet nozzles to the lower level of the working zone is chosen so that that forced turbulent air movement only occurs on the site, characterizing the distance from the outlet nozzle to the lower level of the working area.

Further movement of the air at the height of the working area (in this embodiment, the height of floor trolleys 8 with product) is provided due to the effect of extrusion formed of air streams (left and right) and feed them to the lower level of product placement and further raising the height of the area of the product laminar flow, which eliminates the vortex effect movement of air around the product and, consequently, to the maximum extent possible to facilitate uniform drying conditions of the product and the preservation of their quality. At the same time is achieved by reduction of the power consumption for the operation of the fans due to a decrease in the length of the forced movement of air currents.

Outgoing air flow moistened by contact with the surface of the product, up to the holes of the exhaust channel 9, and then arrive at the air-conditioned 3, where the corresponding heat-moisture treatment. Then the scheme of movement of air repeats.

An example of konkretniej, posted on 9 trucks in 2 rows, it is necessary to carry out the distribution of air in reverse flow through a conical nozzle (prototype) and one-sided pyramidal nozzle (the invention) and to compare the energy consumption for these methods in the following source data: height outdoor trolley hR. C=2 m, the width of the space between the wall of the chamber and a working area bCR= 0.25 m; the width of the drying chamber bCam=2.2 m, the height of the suspension inlet channels with conical nozzles hAve=2.1 m in the distribution of air through a conical nozzle; height suspension of the supply channels in the distribution of air through the pyramidal nozzle hAve p=0,5 hR. C=1 m, the length of the floor truck Ltel= 1.25 m; chamber length LCam=12 m, the recommended rate of air in the working areap.C.= 0.15 m/c.

When the air flow through a conical nozzle into account structural data, which provide the lowest energy consumption: the nozzle diameter d0=60 mm, d=120 mm, hwith=180 mm, t0=4d0=240 mm When applying air through unilateral pyramidal nozzle accept the following data: b0=50 mm, b= 100 mm, hc=120 mm, Lc=120 mm, t0=240 mm

Ltelntel=1,259=11,25 m

LKahnLR. C< / BR>
Accept the channel length LKahn=to 11.52 m with the placement of 48 nozzles (conical or pyramidal), given that t0=240mm

LKahn=nwitht0=480,24=to 11.52 m

Calculation of air distribution and specific consumption of electricity for the distribution of conical nozzles (prototype)

1. Determination of air flow

The air flow required for the flow through one inlet channel, to determine the recommended speed of the supply air leaving the conical nozzles,0= 10-15 m/c /1/.

Accepted0= 10 m/s. Then the air flow through one inlet channel with conical nozzles is

< / BR>
2. Determination of the air velocity at a distance X

The air velocity at a distance X

X=h+0.5 b1+hR. C=2,1+0,52,2+2=5.2 m,

when applying compact jets

< / BR>
where m is the aerodynamic coefficient for the conical nozzle is chosen equal to m=6,6;

Kwith- coefficient shy;

Kin- factor interaction;

Knis the coefficient of neizotermichnosti.

The coefficient of the constraint depends on the relative rasstoyaniyami (one nozzle)

fp=b1t0/2,

where b1- the width of the working area per distributor, m;

t0- step nozzle, m;

fp=(2,2-0,252)0,24/2=0,2 m

When Kwith=0,45,

where

The coefficient of the interaction of Kcenturydepends on the ratio X/t0< / BR>
X/t0=5,2/0,24=21,7; Kin=1,1.

The coefficient of neizotermichnosti Kncan be taken equal to 1, as in the drying chambers for sausages working temperature difference tpdoes not exceed 2-3oC.

Defined maximum velocityxwhen0= 10 m/s:

< / BR>
x=5,2= 0.3 m/c;

thus the average air velocity in the working area

xcp= 0,5x=5,2= 0.15 m/c.

Taking into account speed loss in the area of product placement ratexcpmust be set to 25% more, i.e.

xcp.opt= 0,151,25 = 0,19 m/c.

When the value of x=5,2= 0.38 m/c, the required speed of the supply air must be0= 12,84 m/c.

3. The specification of the necessary air flow

Air flow V1if speed0= 12,84 m/c is

V1=12,84480,7850,0623600=6270 m3/PM

4. Determination of the power of the motor, the ear, depends on air flow and pressure, and the coefficients of the efficiency of the fans and their drive

NFe= VHKC/(36001000inme)

where V is the air flow rate, m3/h;

H - head loss, PA;

in- Efficiency fanin= 0,7;

m- Efficiency mechanical transmission,m= 0,85;

e- Efficiency motore= 0,95;

KCthe factor of power; KC= 1,05-1,2.

Head losses consist of losses on friction, local resistance and dynamic. Head loss by friction is not more than 5% of the total losses, and therefore can be considered a correction factor. The pressure loss at the local resistance in the air flow through a conical nozzle equal to 450 PA /1/. The loss of dynamic pressure at the exit of air from the nozzle with a speed0= 12,84 m/c are

Hg=20/2 = 1,212,842/2 = 100 PA.

The total pressure loss in the distribution through a conical nozzle

H=(450+100)1,05=575,5 PA.

Taking into account pressure losses, unaccounted calculation, take H=600 PA.

The engine one fan

NFe=62706001,2/(360010000,7 0,950,85)=2,22 kW

5. Determination of the yield of goto.cheese=200 kg=3600 kg,

where 200 kg load one floor of the truck, and given that the normalized shrinkage of the product is gn= 23% when normalized duration of the drying process of smoked sausage Twith=25 hours=600 hours, expect a release of dry product per drying cycle

Gother dry=3600-360023/100=2772 kg

6. The definition of specific power consumption for air distribution during drying 1 kg of product

Nbeats=NmouthTh/Gother dry=22,22 600/2772=0,96 kWh/kg dry.etc.

Calculation of air distribution and specific consumption of electricity for the distribution of pyramidal nozzles (claimed invention)

1. Determining the required length of forced air movement

The proposed method has 2 plot of air flow: the first plot is a plot of the forced movement of air to the working area; the second plot is a plot of air flow from the bottom up due to the effect of thrust (push) force moving jets coming out of the nozzles.

The required length of forced air movement is the distance X1from the exit stream from the pyramidal nozzle to nastoyaniy X1= 1 m

For flat streams generated by pyramidal nozzles

< / BR>
For flat vertical jets coefficient constraint Kwithtaking into account the constraint of jets fence and mutual embarrassment

< / BR>
where KS.g- coefficient of hesitation fencing;

Xp- full length of the jet (Xp=1 m);

b0- the width of the nozzle, b0=0.05 m;

m - aerodynamic coefficient pyramidal nozzle; m=3,2;

t0- the step pyramid of nozzles, t0=0,24 m

The coefficient of the constraint KS.gdetermined depending on the relative distance

< / BR>
< / BR>
The coefficient of interaction:

when the ratio X/t0=1/0,24=4.2 Kin=1;

< / BR>
3. The determination of the velocity of the inflowing air

The speed of supply air0depends on the speed xat a distance of X1=1 m, which depends on the air speed in the reverse flow.

The maximum air speed in the reverse flow arr.max.= 0.38 m/c, which corresponds to the recommended air velocity in the area of productxcp.required.= 0,19 m/c).

On the other hand, the maximum air speed in the reverse flow should fell short of the

The flow rate of air supplied through one inlet channel, when using pyramidal nozzle is

< / BR>
5. Determination of the power motor fan

Power motor fan as in the previous case, as measured by the air flow and loss of his head. Air flow through channel 1 V1= 5800 m3/PM

The pressure loss at the local resistance made in the amount of 5% of the pressure losses in local resistance and dynamic losses. The pressure loss in the local resistances by 30% less than the same head loss by the use of tapered nozzles /1/. The dynamic pressure loss when air speed0= 5,6 m/c are

Hg= 1.2 x 5,62/2 = 18,8 PA.

The total head loss

H=(0,7450+18,8)1,05=383,2 PA.

Taking into account losses, unaccounted calculation, take H=400 PA

The power of the fan motor

NFe=58004001,2/(36001000 0,70,950,85)=1.4 kW.

6. The definition of specific power consumption for air distribution during drying 1 kg of product

Nbeats= 2 x 1.4 600/2772 = 0,61 kWh/kg dry.etc.

The results are shown in table 1.

So abrasivejet respectively for the method of the prototype and the proposed method and 0.61 to 0.96 kWh per 1 kg of dry product. Therefore, when the airflow method prototype electricity consumption for the operation of the fans is 1.5 times more than in the distribution of air in the claimed invention.

Sources of information taken into account.

1. A. M. Brazhnikov, N. D. Malova, "air Conditioning for the enterprises of meat and dairy industry), Food industry, 1979, S. 139, Fig.40.

2. A. M. Brazhnikov, N. D. Malova, "air Conditioning for the enterprises of meat and dairy industry), Food industry, 1979, S. 140, Fig. 41.

3. A. M. Brazhnikov, S. N. Kamensky, N. D. Malova and others, "Study of air flow in the chambers of the heat treatment of smoked sausage", Meat industry of the USSR, 1985, N4, pp. 39-45, Fig. 1,2.

1. The way the air flow when drying meat and fish products, including the use of the reverse air flow, ensure uniform conditions of its distribution in the area of the processed product, the use of laying supplied to the supply flow, characterized in that the air supply to the zone of the processed product is carried out from the bottom up, with nastilanie air stream is carried out at a distance equal pomolnyh one-way nozzles, having a vertical wall by laying jets and an inclined wall from the side of the working area.

2. The method according to p. 1, characterized in that use one-sided pyramidal nozzle with geometric dimensions equal to the width of the outlet of the nozzle is chosen in the range babout= 40 - 50 mm, a width of the inlet within b=2baboutthe height of the nozzle hwith= 2,4 - 2,5 baboutthe length of the nozzle - Lwith= hwithwith the step of placing the nozzles along the length of the inlet channel, is equal to tabout= 4,8 - 5,0 babout.

3. The method according to p. 1 or 2, characterized in that the exhaust duct hole diameter dwit.choose equal to the equivalent diameter of the inlet nozzle desthe number of holes in one row of nwith.resp.take equal to twice the number of nozzles 2nwithin the supply channels, and the step of holes twit.choose equal step of placing nozzles taboutthe length of the supply channels.

4. The method according to p. 1, or 2, or 3, characterized in that the height of the suspension of the supply channels is chosen equal to half the height of the working area and the exhaust channel is greater than the height of the working area by 0.10 to 0.15 m

 

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