RU2154788C1 - Method of distribution of air in drying of meat and fish products - Google Patents

Abstract

FIELD: meat industry; drying smoked sausage and other meat products; drying fish products. SUBSTANCE: proposed method includes use of return air flow and laying-on of supply flow. Air is supplied to area of product to be dried from below; laying-on is effected at distance equal to half height of working zone of drying chamber. Supply of air is effected by means of pyramidal one-sided nozzles having vertical wall on side of laying of jets and inclined wall on side of working zone. EFFECT: improved quality of food-stuff being processed; reduced power requirements. 4 cl, 4 dwg

Description

 The invention relates to air distribution methods and is intended for use in meat industry enterprises for drying smoked sausages and other meat products, for drying dried sausages, as well as in fish industry enterprises for drying fish products.

A known method of air distribution, providing for the distribution of supply air using distribution channels with flat nozzles (Fig. 1). This method is used in drying chambers, chambers for packaging and storage of meat and dairy products, etc. With this method, the distribution of the supply air is carried out through channels located in the upper zone of the chambers, on the longitudinal walls of the chambers or in the lower zone [1]. The method is characterized by the simplicity of devices for air distribution, but has the following disadvantages:
- uses an imperfect type of air diffuser - a flat nozzle. Flat nozzles made in the form of rectangular holes with sizes from 200x300 to 50x100 mm, round holes with a diameter of 50-100 mm and slots from 30x100 to 50x50 mm and others cannot provide the necessary range of the supply jets due to the fact that the air velocity decreases in the beginning of the working area, not reaching its middle;
- due to the short range of the supply jets, there is a significant uneven distribution of air velocity in the working area of the drying chambers, which reaches 50-60%;
- due to the insufficient range of the supply jets leaving the flat nozzles, a significant part of the air supplied to the drying chamber (up to 30%) enters the fan inlet, bypassing the working area and not participating in the processes of heat transfer and mass transfer with the product, t. e. not all supplied air is involved in the processes of heat transfer and mass transfer with the product. Therefore, partly such a method of air distribution is idle and therefore has unproductive energy costs;
- due to the insignificant range of the supply jets and the uneven conditions of heat transfer and mass transfer between air and the product, the duration of the drying process increases compared to the duration recommended by technological standards, which reduces the quality of the processed products due to the formation of mold on their surface in stagnant areas of the chamber where there is no movement air;
- a concentrated exhaust air extract is provided, which also contributes to the creation of uneven air distribution conditions in the working area of the drying chambers and, therefore, the formation of mold on the product.

 A known method of air distribution using the upper perforated channels, ceilings and panels [2]. Perforated channels (figure 2) use a perforated panel as an air diffuser, in which flat nozzles are provided, made in the form of round holes with a diameter of 3-20 mm. The coefficient of live section of the perforated panel does not exceed 5-10%, i.e. the area occupied by the holes is only 5-10% of the total area of the air-distributing panel, which is several times smaller than in the previous method. The reduction in the coefficient of living cross-section is achieved through the use of a large number of small-diameter holes, which allows supply air to be supplied as a single air stream (the supply jets merge at a distance not exceeding 5 hole diameters). The supplied air flow is characterized by a uniform distribution of air velocity in any section. But it has a different speed at 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, since the distance between the upper and lower levels of the working area is 2 meters or more. In this case, the degree of uneven distribution of air velocity should not exceed 30% under technological conditions, i.e. velocity in the product zone should be in the range 0.15-0.2 m / s.

 When using the method of air distribution using the upper perforated channels in drying ovens for raw smoked sausages, the product located on the upper level of the working area is overdried, and on the lower level under-dried, which causes product loss due to excessive drying and mold formation. In addition, the method provides a concentrated exhaust air exhaust, which also contributes to the uneven distribution of air velocity in the product zone and the formation of marriage.

 The closest in technical essence and the problem to be solved is the method of air distribution in the drying chambers using the reverse air flow created by conical or cylindrical nozzles [3].

 The method provides for the supply of fresh air through two supply air distribution channels (Fig. 3): left and right, located in the upper part of the chamber along its longitudinal walls and equipped with conical or cylindrical nozzles uniformly installed along the length of the channels. An exhaust air distribution channel is provided in the middle of the upper part of the chamber. As an air distributor in the exhaust channel, flat rectangular, slit-shaped or round nozzles, diffusers, etc. are used. The exhaust channel is placed directly above the product zone, which ensures uniform exhaust air exhaust throughout the zone, and not concentrated, as provided in the above methods.

 This method provides for the distribution of air in the product zone along the reverse flow, and the direct flow moves to the right and left along the longitudinal walls, laying on them and then on the floor of the chamber. When laying, the formation and merging of individual supply jets, the interaction, tightness and equalization of the speed of the formed air flow (left and right), not in the working area, but in the spaces between the longitudinal wall and the working area. Supply jets in the form of reverse flows enter the product zone from below and move up. With this method, only the resistance of the product affects the flows. In this case, the drop in air velocity in the working area does not exceed 0.05 m / s. Therefore, at a height of product placement equal to 2 m (the height of the floor trolley), the drop in speed corresponds to technological standards.

The method involves the use of conical and cylindrical nozzles with different values of the diameter and height of the nozzle, as well as with different spacing of the nozzles along the length of the channels. In drying chambers of various firms, conical nozzles with an outlet diameter d ₀ = 30-80 mm with a nozzle placement pitch t ₀ = 180-400 mm are most often found. Such indicators significantly affect the energy consumption necessary for the distribution of air in the working area.

 As a result of our studies, we found that the specific cost of electricity for the operation of the fans of the air distribution system is 0.9-2.2 kWh of electricity per 1 kg of dry product and are estimated as significant compared to other methods.

 Thus, the air distribution according to this method has advantages over the above methods in that it uses the most efficient form of the air distributor, made in the form of a conical nozzle that provides the greatest range of the jets, while the nozzles are evenly spaced along the length of the channel, provide air flow to the product uniformly distributed parameters, and the feed by the reverse flow method ensures that the specified air velocity in the product zone is maintained within the allowable range hnologicheskimi conditions. The entire supplied air stream enters the product zone and implements the necessary conditions for heat transfer and mass transfer on the product surface, which contributes to uniform drying conditions. Uniform extraction of the exhausted humidified air from the product zone along its entire length is provided for in connection with the presence of an exhaust channel over the central part of the product zone with distributors uniformly located in it for intake of humidified air.

The disadvantages of this method are
- increased energy consumption to ensure the operation of the fans due to the need to create air flows of increased range;
- increased turbulence of air flows washing the surface of the products, which negatively affects the quality of the processed products;
- increased length of air flows, which is caused by the fact that the principle of operation of this method of air distribution is based on the need to ensure conditions of forced air circulation over the entire height of the working area. In this regard, the required length of the air flow consists of the lengths of three sections
X _p = h + 0.5b _r.z. + h _r.z.
where X _p - the total length of the air flow, m;
h is the height of the suspension of the channels, m;
b _rz - the width of the working area, m;
b _r.z - the height of the working area, m;
In this method, there is not only an increased energy consumption for the operation of the fans. At the same time, the costs of heat and cold for drying the product increase, since an increase in the energy consumption for the operation of the fans occurs not only due to increased pressure losses when using conical nozzles, but also due to the increased air flow caused by the need to create an increased air velocity at the nozzle exit.

 The increased turbulence of the air washing the surface of the product, in most cases, causes the hardening of the surface layer ("hardening") and darkening of its color in comparison with the inner layers of the sausage loaf. At the same time, an uneven distribution of moisture is formed over the section of sausage loaves. Moreover, the wettest layer is inside the loaf, which affects the quality of the product and reduces its shelf life.

 The aim of the creation of the claimed invention is to improve the quality of processed foods and reduce energy consumption.

 This goal is achieved by the fact that in the claimed method, which includes the use of reverse air flow, providing uniform conditions for its distribution in the area of the processed product, the effect of laying the supplied supply jets, the air supply to the area of the processed product is carried out from the bottom up, and the supply jets are laid on the walls at a distance characterizing the length of the air flow from the nozzle outlet to the entrance to the working area of the drying chamber, while fresh air is carried out using pyramidal single-sided nozzles having a vertical wall on the side of the spraying jets and an inclined wall on the side of the working zone (to ensure more reliable laying conditions), while laying the air flow is carried out at a distance equal to half the height of the working zone, i.e. .

X _P.Z. = 0.5b _R.Z. ,
where X _pz - the total length of the air flow forced by the fan in the claimed invention,
h _rz - the height of the working area.

 Under such conditions of supply of forced air sweats, there is no need to install conical nozzles, providing the greatest range of the supply jets. We propose a supply air diffuser made in the form of a pyramidal nozzle with a one-sided bevel on the side wall on one side and a vertical wall on the other side, which makes it possible to compress the supply stream and reduce the contact area of the stream with the vertical chamber wall in order to provide more reliable laying conditions.

In addition, the method involves the use of pyramidal single-sided nozzles with geometric parameters: width of the nozzle outlet b ₀ = 40-50 mm, width of the nozzle inlet b = 2b ₀ , nozzle height h _c = 2.4-2.5b ₀ , nozzle length L _s = h _s , the step of the nozzles along the length of the supply channels t ₀ = 4.8-5.0b ₀ .

The method provides in the exhaust channel round holes with a diameter d out _. corresponding to the equivalent diameter of the supply nozzle, i.e. d = d _{e.s drawing;} the number of holes in one row n _prot . _holes = 2n _s , where n _{with the} number of nozzles in the supply channels placed in one row n _s = 2; _drawing hole pitch t = t _0. Furthermore, the method provides for the suspension height of channels: h _ave air-supply _RZ = 0,5h, _drawing exhaust h = h + _RZ (0.10-0.15) m.

 The claimed method allows to supply air to the working area by displacing reverse laminar flow, moving from the bottom up in one direction (without turbulence) through the entire height of the working area to the openings of the exhaust channel.

 A diagram of a device for implementing the inventive method of air distribution in the reverse flow by pyramidal nozzles is shown in figure 4.

 The device includes fans 1,2, air conditioning 3, supply ducts 4,5, pyramidal nozzles 6, a drying chamber 7, carts with a product 8, an exhaust duct 9.

 The device operates as follows. The supply air is supplied by fans 1.2 from the air conditioner 3 to the left supply channel 4 and the right supply channel 5 and through the pyramidal nozzles 6, evenly spaced along the length of the supply channels, enters into the drying chamber as separate jets 7. The jets are laid on the longitudinal walls of the drying chamber on the left and right sides. When laying, the jets merge, constrain, interact and form a common air flow (left and right). Moreover, the speed of air supply from the nozzles, their number and the distance from the nozzle outlet to the lower level of the working area is chosen so that forced turbulent air movement occurs only in the area characterizing the distance from the nozzle outlet to the lower level of the working area.

 Further air movement along the height of the working area (in this embodiment, along the height of floor trolleys 8 with the product) is provided due to the effect of extruding the formed air flows (left and right) and supplying them to the lower level of product placement and further lifting along the height of the product placement zone by laminar flows , which eliminates the vortex effect of air movement around the product and, therefore, to the maximum extent possible to promote uniform drying conditions of the product and the preservation of its quality display firs. At the same time, a reduction in the energy consumption for the operation of the fans is achieved in connection with a decrease in the length of the forced movement of air flows.

 Outgoing air streams moistened as a result of contact with the surface of the product rise to the openings of the exhaust duct 9, and then enter the air conditioner 3, where they undergo the appropriate heat and humidity treatment. Then the pattern of air movement is repeated.

 An example of a specific implementation of the claimed method.

In the drying chamber for raw smoked sausages for 18 floor trolleys, placed 9 trolleys in 2 rows, it is necessary to distribute air in the reverse flow through conical nozzles (prototype) and pyramidal single-sided nozzles (claimed invention) and compare the specific energy consumption for these methods in the following initial data: the height of the floor trolley h _rz = 2 m, the width of the space between the wall of the chamber and the working area b _ol = 0.25 m; drying chamber width b _kam = 2.2 m, the height of suspension of air-supply channels with conical nozzles _pr.k h = 2.1 m at an air distribution through the conical nozzle; the height of the suspension of the supply ducts during the distribution of air through the pyramidal nozzles h _ave.p = 0.5h _r.z = 1 m, the length of the floor trolley L _tel = 1.25 m; _Cams camera length L = 12 m, the recommended speed of the air in the working area ω _p.z. = 0.15 m / s.
When air is supplied through conical nozzles, we take into account design data at which the lowest energy consumption is ensured: nozzle diameter d ₀ = 60 mm, d = 120 mm, h _c = 180 mm, t ₀ = 4d ₀ = 240 mm. When air is supplied through pyramidal single-sided nozzles, we accept the following data: b ₀ = 50 mm, b = 100 mm, h _c = 120 mm, L _c = 120 mm, t ₀ = 240 mm.

The required length of the air distribution channels must correspond to the length of the working area
L _r.z. = L _bodies • n _bodies = 1.25 • 9 = 11.25 m.

L _kan ≥L _RZ
Accept channel length L = 11.52 meters _kan with the placement of nozzles 48 (conical and pyramidal), given that t ₀ = 240 mm
L _channel = n _s • t ₀ = 48 • 0.24 = 11.52 m.

Calculation of the distribution of air and specific energy consumption when using the method of air distribution with conical nozzles (prototype)
1. Determination of air flow
The air flow required when supplying through one supply channel is determined by the recommended speed of the supply air leaving the conical nozzles, ω ₀ = 10-15 m / s / 1 /.

2. Определение скорости воздуха на расстоянии X
Скорость воздуха на расстоянии X
X=h+0,5b₁+h_р.з=2,1+0,5•2,2+2=5,2 м,
при подаче компактными струями

где m - аэродинамический коэффициент для конического сопла выбирается равным m=6,6;
K_с - коэффициент стеснения;
K_в - коэффициент взаимодействия;
K_н - коэффициент неизотермичности.We take ω ₀ = 10 m / s. Then the air flow through one inlet channel with conical nozzles is

2. Determination of air velocity at distance X
Air speed at distance X
X = h + 0.5b ₁ + h _r.z. = 2.1 + 0.5 • 2.2 + 2 = 5.2 m,
when feeding in compact jets

where m is the aerodynamic coefficient for the conical nozzle is chosen equal to m = 6.6;
K _with - constraint coefficient;
K _in - interaction coefficient;
K _n - non-isothermal coefficient.

относительной площади

где f_р - площадь рабочей зоны, приходящаяся на один воздухораспределитель (одно сопло)
f_р=b₁•t₀/2,
где b₁ - ширина рабочей зоны, приходящаяся на один воздухораспределитель, м;
t₀ - шаг сопел, м;
f_р=(2,2-0,25•2)•0,24/2=0,2 м.The constraint coefficient depends on the relative distance.

relative area

where f _p - the area of the working area per one air distributor (one nozzle)
f _p = b ₁ • t _0/2 ,
where b ₁ - the width of the working area per one air distributor, m;
t ₀ - nozzle pitch, m;
f _p = (2.2-0.25 • 2) • 0.24 / 2 = 0.2 m.

коэффициент K_с=0,45,
где

Коэффициент взаимодействия K_в. зависит от отношения X/t₀
X/t₀=5,2/0,24=21,7; K_в=1,1.At

coefficient K _c = 0.45,
Where

The interaction coefficient K _in. depends on the ratio X / t ₀
X / t ₀ = 5.2 / 0.24 = 21.7; K _in = 1.1.

The non-isothermal coefficient K _n can be taken equal to 1, since in the drying chambers for sausages the working temperature difference Δt _p does not exceed 2-3 ^o C.

ω_x=5,2 = 0,3 м/c;
при этом среднее значение скорости воздуха в рабочей зоне
ω_xcp = 0,5ω_x=5,2 = 0,15 м/c.
С учетом потери скорости в зоне размещения продукта скорость ω_xcp должна иметь значение на 25% больше, т.е.We determine the maximum value of the velocity ω _x at ω ₀ = 10 m / s:

ω _{x = 5.2} = 0.3 m / s;
the average air velocity in the working area
ω _xcp = 0.5ω _{x = 5.2} = 0.15 m / s.
Given the loss of speed in the product distribution area, the speed ω _xcp should have a value of 25% more, i.e.

ω _xcp.req = 0.15 • 1.25 = 0.19 m / s.
With the value of ω _{x = 5.2} = 0.38 m / s, the necessary speed of the supply air should be ω ₀ = 12.84 m / s.
3. Clarification of the required air flow
Air consumption V ₁ at a speed of ω ₀ = 12.84 m / s is
V ₁ = 12.84 • 48 • 0.785 • 0.06 ² • 3600 = 6270 m ³ / h.

4. Determining the power of the fan motor
The power of the fan motor for the distribution and circulation of air depends on the air flow and pressure, as well as on the efficiency factors of the fans and their drive
N _dv = V • H • K _s / (3600 • 1000 • η _in • η _m • η _el ),
where V is the air flow, m ³ / h;
H - pressure loss, Pa;
η _in - fan efficiency, η _in = 0.7;
η _m - the efficiency of the mechanical transmission, η _m = 0.85;
η _el - the efficiency of the electric motor, η _el = 0.95;
K _s - power headroom; K _s = 1.05-1.2.

Losses of pressure consist of friction losses, local resistance and dynamic. Losses of friction pressure are not more than 5% of the total losses, and therefore they can be taken into account by a correction factor. Losses of pressure on local resistance during air supply through conical nozzles are 450 Pa / 1 /. The dynamic pressure losses when the air leaves the nozzles with a velocity of ω ₀ = 12.84 m / s are
H _g = ρ • ω $\genfrac{}{}{0ex}{}{\text{2}}{\text{0}}$ / 2 = 1,2 • 12,84 ^2/2 = 100 Pa.
Total pressure loss during air distribution through conical nozzles
H = (450 + 100) • 1.05 = 575.5 Pa.

 Taking into account the pressure loss, unaccounted for by the calculation, we take H = 600 Pa.

Engine power of one fan
N _dv = 6270 • 600 • 1.2 / (3600 • 1000 • 0.7 • 0.95 • 0.85) = 2.22 kW
5. Determination of the yield of finished products in one drying cycle
Given that the capacity of the drying chamber for the raw product
G _{raw cheese} = 200 kg • 18 = 3600 kg,
where 200 kg is the loading of one floor trolley, and taking into account that the standardized drying of the product is Δg _n = 23% for the normalized duration of the drying process of raw smoked sausages T _s = 25 days = 600 hours, we calculate the output of the dry product in one drying cycle
G _pr.dry = 3600-3600 • 23/100 = 2772 kg.

6. Determination of the specific energy consumption for air distribution during drying of 1 kg of product
N _beats = N _mouth • T _h / G _{dry dry} = 2 • 2.22 • _600/2772 = 0.96 kW • h / kg dry dry

Calculation of the distribution of air and specific energy consumption when using the air distribution method with pyramidal nozzles (the claimed invention)
1. Determination of the required length of the forced air movement
In the proposed method, there are 2 sections of the air flow: the first section is the section of the forced movement of air to the working area; the second section is the section of air movement from the bottom up due to the effect of forcing (pushing) it by forcefully moving jets coming from the nozzles.

The required length of the forced air movement is the distance X ₁ from the place where the jet exits the pyramidal nozzles to the lower level of the working area
X ₁ = 0.5h _r.z = 0.5 • 2 = 1 m
2. Determination of air velocity ω _x at a distance of X ₁ = 1 m

Для плоских вертикальных струй коэффициент стеснения K_с, учитывающий стеснение струй ограждением и взаимное стеснение

где K_{с. гр} - коэффициент стеснения ограждением;
X_п - полная длина струи (X_п=1 м);
b₀ - ширина сопла, b₀=0,05 м;
m - аэродинамический коэффициент пирамидального сопла; m=3,2;
t₀ - шаг пирамидальных сопел, t₀=0,24 м.For flat jets created by pyramidal nozzles

For flat vertical jets, the tightness coefficient K _s , taking into account the tightness of the jets with a guard and mutual tightness

where K _{s. gr} - coefficient of constraint by the fence;
X _p - the total length of the jet (X _p = 1 m);
b ₀ - nozzle width, b ₀ = 0.05 m;
m is the aerodynamic coefficient of the pyramidal nozzle; m = 3.2;
t ₀ - step of the pyramidal nozzles, t ₀ = 0.24 m

Коэффициент взаимодействия:
при отношении X/t₀=1/0,24=4,2 коэффициент K_в=1;

3. Определение скорости приточного воздуха
Скорость приточного воздуха ω₀ зависит от скорости ω_x на расстоянии X₁=1 м, которая зависит от скорости воздуха в обратном потоке.Constraint coefficient K _{s. gr is} determined depending on the relative distance

Interaction coefficient:
with the ratio X / t ₀ = 1 / 0.24 = 4.2, the coefficient K _in = 1;

3. Determining the supply air speed
The supply air velocity ω ₀ depends on the speed ω _x at a distance X ₁ = 1 m, which depends on the air speed in the return flow.

0,38 = 0,134ω_x; откуда ω_x = 2,8 м/c; ω₀ = 5,6 м/c.
4. Определение расхода воздуха
Необходимый расход воздуха, подаваемый через один приточный канал, при использовании пирамидальных сопел составляет

5. Определение мощности электродвигателя вентиляторов
Мощности электродвигателя вентиляторов так же, как и в предыдущем случае, определяем с учетом расхода воздуха и потерь его напора. Расход воздуха через 1 канал V₁ = 5800 м³/ч.The maximum air velocity in the reverse flow ω _obm.max. = 0.38 m / s, which corresponds to the recommended air velocity in the product placement area (ω _xcp.req. = 0.19 m / s).
On the other hand, the maximum air velocity in the return flow must meet the condition

0.38 = 0.134ω _x ; where ω _x = 2.8 m / s; ω ₀ = 5.6 m / s.
4. Determination of air flow
The required air flow supplied through one supply channel, when using pyramidal nozzles is

5. Determining the power of the fan motor
The power of the fan motor, as in the previous case, is determined taking into account the air flow and pressure losses. Air flow through 1 channel V ₁ = 5800 m ³ / h.

Losses of pressure on local resistances are also taken in the amount of 5% of pressure losses in local resistances and dynamic losses. The pressure loss in local resistances is 30% less than the similar pressure loss when using conical nozzles / 1 /. The dynamic pressure losses at an air velocity of ω ₀ = 5.6 m / s are
H _g = 1,2 x 5,6 ^2/2 = 18,8Pa.

Total pressure loss
H = (0.7 • 450 + 18.8) • 1.05 = 383.2 Pa.

Taking into account losses not taken into account in the calculation, we take H = 400 Pa
Fan motor power
N _dv = 5800 • 400 • 1.2 / (3600 • 1000 • 0.7 • 0.95 • 0.85) = 1.4 kW.

6. Determination of the specific energy consumption for air distribution during drying of 1 kg of product
N _beats = 2 x 1.4 600/2772 = 0.61 kWh / kg dry

 The results are shown in table 1.

 Thus, the specific energy consumption for the distribution of air in the drying chamber for smoked sausages is, respectively, for the prototype method and the proposed method, 0.96 and 0.61 kWh per 1 kg of dry product. Therefore, when distributing air according to the prototype method, the energy consumption for operation of the fans is 1.5 times greater than when distributing air according to the claimed invention.

 Sources of information taken into account.

 1. A.M. Brazhnikov, N.D. Malova, "Air conditioning in the meat and dairy industry", M., Food industry, 1979, p. 139, Fig. 40.

 2. A. Brazhnikov, N.D. Malova, "Air conditioning in the meat and dairy industry", M., Food industry, 1979, p. 140, fig. 41.

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

Claims (4)

 1. The method of air distribution during the drying of meat and fish products, including the use of a return air stream that provides uniform conditions for its distribution in the area of the processed product, the application of laying the supply air stream, characterized in that the air supply to the area of the processed product is carried out from the bottom up. the air flow is carried out at a distance equal to half the height of the working zone of the drying chamber, and the supply of fresh air is carried out using amide single-sided nozzles having a vertical wall on the side of the jetting and an inclined wall on the side of the working area. 2. The method according to claim 1, characterized in that use pyramidal one-sided nozzles with geometric dimensions equal to: the width of the nozzle outlet is selected within b _about = 40-50 mm, the width of the inlet within b = 2b _about , the nozzle height h _c = 2.4 - 2.5b _about , the nozzle length is L _s = h _s with a step of placing nozzles along the length of the supply channels equal to t _about = 4.8 - 5.0b _about . 3. The method according to claim 1 or 2, characterized in that in the exhaust duct, the diameter of the hole d _ex. chosen equal to the equivalent diameter of the supply nozzle d _es , the number of holes in the same row n _prot. take equal to twice the number of nozzles 2n _with in the supply channels, and the hole pitch t out _. choose equal to the pitch of the nozzles t _about along the length of the supply channels.  4. The method according to claim 1, or 2, or 3, characterized in that the suspension height 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 - 0.15 m

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