Air evocation is the most effective event for creating the required meteorological conditions in permanent workplaces (temperature, humidity and air velocity). The use of air shower with significant heat radiation or with open production processes is particularly effective if the technological equipment that emit harmful substances does not have shelters or local exhaust ventilation. Air stroke is a jet of air aimed at a limited workplace or directly on the worker.

Air mobility in the workplace during air stroke reaches from 1 to 3.5 m / s. Decoration is carried out by special nozzles, while the jet is sent to the irradiated areas of the body: head, chest. The size of the area of \u200b\u200bthe area is m. The stroke can be carried out by outer unprocessed air, adiabatic-cooled air or isolating cooling. In some cases, it is allowed to use recycling air, and there must be a slight thermal radiation and no harmful discharge.

The cooling effect of air scenario depends on the difference in temperature of the body of the working and air flow, as well as from the speed of flowing in air of the cooled body. When mixing the jet coming out of the hole, with the ambient speed, the temperature difference and the concentration of impurities in the cross section of the free jet change. The jet should be directed so that it is possible to sue hot or air polluted air polluted. For example, when finding a fixed working place near an open bake opening, there should be no stitching device near the opening with the direction of the jet to meet the worker, since in this case it is impossible to avoid suction of hot gases, as a result of which the superheated air will be applied to the worker. When calculating the air stroke systems, the calculated parameters are made for warm and calculated parameters B for cold periods of the year. To calculate the air stroke of the year-round operation for the calculated period, the warm period is taken, and for the cold period, only the temperature of the supply air is determined.

Systems supplying air to air stroke pipes are designed separately from other destination systems. The distance from the place of release of air to the workplace should be taken at least 1 m. Calculation procedure

1. Place air parameters in the workplace, the location of the nozzle is planned, the distance from the nozzle to the workplace, and are also set by the type of stroke pipe. 2. Determine the air velocity at the outlet of the nozzle depending on the normalized air mobility in the room, where is the normalized air mobility, is the distance from the nozzle to the workplace, M, - the coefficient of changes in the speed - the cross section of the selected pipe. 3. Determine the minimum temperature at the outlet of the nozzle, where the normalized temperature is the temperature change coefficient. 4. Determined air consumption required for feeding the pipe.

The intensity of thermal irradiation of a person is regulated on the basis of the subjective sensation by the man of irradiation energy. According to the requirements of regulatory documents, the intensity of thermal irradiation of the heat equipment operating from the heated surfaces, the lighting devices should not exceed:

- 35 W / m 2 when irradiated more than 50% of the body surface;

- 70 W / m 2 when irradiated from 25 to 50% of the body surface;

- 100 W / m 2 when irradiated not more than 25% of the body surface.

From open sources (heated metal and glass, open flames) The intensity of thermal irradiation should not exceed 140 W / m 2 when irradiated with no more than 25% of the body surface and the mandatory use of personal protective equipment, including the means of protecting the face and eye.

Sanitary standards are also limited to the temperature of the heated surfaces of the equipment in the working area, which should not exceed 45 ° C, and for equipment, inside which the temperature is close to 100 ° C, the temperature on its surface should be no higher than 35 ° C.

In production conditions, it is not always possible to fulfill the regulatory requirements. In this case, measures should be provided for the protection of workers from possible overheating:

- remote control of the process of the technological process;

- air or water-air searches for jobs;

- a device of specially equipped rooms, cabin or jobs for short-term recreation with air-conditioned air supply;

- use of protective screens, water and air curtains;

- Application of personal protective equipment, workwear, specialobuvi, etc.

One of the most common ways to combat thermal radiation is the screening of radiating surfaces. Three types of screens are distinguished:

1. Opaque - such screens include, for example, metal (including aluminum), alfolia (aluminum foil), lined (foam concrete, foamglass, crumples, pemps), asbestos, etc. In opaque screens, the energy of electromagnetic oscillations interacts with Screen substance and turns into thermal energy. Absorbing radiation, the screen is heated and, as any heated body, becomes the source of thermal radiation. In this case, the radiation of the screen surface, opposing the shielded source, is conditionally considered as a missed radiation of the source.

2. Transparent - these are screens made of various glasses: silicate, quartz, organic, metallized, as well as film water curtains (free and driving on glass), waterproof curtains. In transparent screens, radiation, interacting with the substance of the screen, passes the turning stage into thermal energy and is distributed inside the screen according to the laws of geometric optics, which provides visibility through the screen.

3. Translucent - These include metal grids, chain veins, glass-reinforced metal grid screens. Translucent screens combine the properties of transparent and opaque screens.

According to the principle of operation, the screens are divided into:

- heat-reflecting;

- heat-absorbing;

- heat sink.

However, this division is sufficiently conditionally, since each screen has simultaneously ability to reflect, absorb and distinguish heat. The attribution of the screen to a particular group is made depending on which its ability is stronger.

Heat-reflecting screens have a low degree of black surfaces, as a result of which they are a significant part of the radiant energy falling on them reflect in the opposite direction. Alpol, leaf aluminum, galvanized steel, aluminum paint are widely used as heat-reflecting materials in the screens designs.

The heat-absorbing screens are made of materials with high thermal resistance (small thermal conductivity coefficient). As heat-absorbing materials, refractory and thermal insulation bricks, asbestos, slag, are used.

As heat sink screens, water curtains are most widely used, freely falling in the form of a film, irrigating another shielding surface (for example, metallic), or enclosed in a special casing of glass (aquarial screens), metal (coilings), etc.

The effectiveness of heat radiation protection with screens is estimated by the formula:

where Q bz -the intensity of thermal radiation without the use of protection, W / m 2, Q h -the intensity of thermal radiation with the use of protection, W / m 2.

The multiplicity of heat flux, T, the protective screen is determined by the formula:

where Q bz - the intensity of the emitter stream (without using the protective screen), W / m 2, Q Z. - the intensity of the heat radiation stream, W / m 2.

The transmission coefficient of the heat flux screen, τ, is:

τ \u003d 1 / m. (2.8)

Local supply ventilation is widely used to create the required microclimate parameters in a limited volume, in particular, directly in the workplace. This is achieved by creating air oasis, air curtains and air shower.

The air flow directed directly to the worker allows you to increase heat removal from its body into the environment. The choice of air flow rate depends on the severity of the work performed, as well as on the intensity of irradiation, but it should not, as a rule, exceed 5 m / s, since in this case the worker has unpleasant sensations (for example, noise in the ears). The effectiveness of the air shower increases when the air is cooled into the workplace or when mixing it with finely sprayed water (water-air shower).

Air oases are in separate areas of work premises with high temperatures. To do this, a small working area is covered with light portable partitions with a height of 2 m and a cool air with a speed of 0.2 - 0.4 m / s is faded.

Air drifts to prevent penetration into the room of outer cold air by supplying warmer air at high speed (10-15 m / s) at a certain angle towards the cold stream.

Aerial souls are in hot workshops in workplaces under the influence of radiant heat flow of large intensity (more than 350 W / m 2).

The air flow directed directly to the worker allows you to increase heat removal from its body into the environment. The choice of air flow rate depends on the severity of the work performed, as well as on the intensity of irradiation, but it should not, as a rule, exceed 5 m / s, as in this case, the worker has an unpleasant feeling (for example, noise in the ears).

The effectiveness of the air shower increases when the air is cooled into the workplace or when mixing it with finely sprayed water (water-air shower).

The most effective event for creating on permanent jobs or areas where air parameters differ from the average in the working area required by the sanitary and hygienic standards of meteorological conditions of temperature, humidity and air velocity. VD is used in the following cases:

To combat radiant warmth

To combat convective heat when it is impossible to ensure the regulatory parameters of common ventilation

To combat gas emissions if the device is not possible, the device of localizing ventilation

The most common VD in foundry, blacksmith and thermal shops, where the heat flux is 175-350 W / m2 and more.

Decoration of jobs is carried out depending on the surface density of radiant thermal flow inner and outer air. If the density of the radiant heat flux is within 175-380 W / m 2 within the workplace of more than 0.2 m2, the inner air is used. In this case, the temperature and speed of air in the workplace must correspond to SNU.

The inner air is called aerators. Their main elements are:

1 axial fan with electric motor on one shaft

2 Automatic rotary device up to 600

3 Pneumatic nozzle with water supply

This VD is used to maintain the sites on which there are several people. Rotary aerators provide relatively uniform speeds in the air flow and a wider service area. However, at a temperature of more than 280, their cooling effect is significantly reduced. With a heat flux of 1800 W / m2, VD applies using screens.

The VD operating on the outer air includes:

1 supply chamber or central air conditioner with irrigation chamber (can work in any mode)

2 air duct networks that can be in underground channels and on the workshop

3 Serving nozzles, which are mounted on the floor at a distance of 1.8 m to the lower edge of the nozzle. The VD system cannot be combined with the system of influencing general ventilation. Serving nozzles can be of different designs. The pipe itself is swivel.

1 duct.

Features of the calculation:

The calculation of the WD comes down to:

1 selection of air processing mode

2 Determination of the parameters of the air-velocity and temperature.

3 Determination of the dimensions of the fragrant nozzle F0

4 selection of technological equipment

The existing method of calculation is based on solving the problem of optimizing the work of the VD in terms of consumption of energy resources and the laws of the supply jet. At the exit of their air distributor of the stitching nozzle, a compact jet is created. The zone of the jet is considered a zone of a width of more than 1 meter, and the high-speed limit is the zone of 50% of the speed of υx.

method for calculating prof. PV PARTROKINA- The temperature criterion is initially determined:

trolle- air temperature in the working area

tyrrmed \u200b\u200btemperature in the workplace

t0-air temperature, which is obtained with adiabatic cooling of outdoor air, that is, the minimum flow temperature that can be obtained without the use of artificial cold

tD- Adiabate Air Treatment

Δt-heating with fan \u003d 0.5-1,50c

With Pt.<1 принимается адиабатное охлаждение

1 Pt≤0,6 In this case, the air temperature in the workplace is greater than the temperature T0. In this mode, the decoration installation will work without artificial cold using adiabatic cooling. For ventilation of the workplace uses the main part of the working jet and then:

n-coefficient characterizing temperature change along the jet axis

the distance from the release to the workplace, this distance should not be less than 1M.

F0- The section of the cross section of the stitching nozzle

The speed of air at the outlet of the nozzle is determined as:

m- coefficient characterizing a change in speed along the axis of the jet

For speed at the workplace, taking into account the jet zone:

The temperature of the supply air is determined from the PT criterion:

0.6- Consides the average temperature parameters in the jet

The amount of air flowing out of the nozzle:

2 Pt≥1 The achievement of the required temperature of the inflow is possible only with artificial cooling. To save energy resources, the workplace should be scented with the initial section of the supply jet. In the initial section, the speed and temperature parameters are unchanged and equal to the initial one. In this case, the relative distance is recommended:

The dimensions of the frantic nozzle are determined by the dependence:

Since on the initial section Х \u003d υ0, and υrm \u003d 0.7υ0, then the air outlet rate of BP:

t0 \u003d \u200b\u200bTrm / 0.6 (7)

With the value of Pt \u003d 1, the nozzles calculated by the above formulas are obtained very large. In these cases, artificial air cooling is necessary and carry out the calculation by the formulas when PT\u003e 1

The temperature of the air flow from the supply nozzle must be determined by the formula:

5. Absorption Refrigerator:

The working cycle in these machines is carried out due to thermal energy. It works on a mixture of two substances, of which one is a refrigerant (HA), and the second absorbent, that is, with a substance absorbing or dissolving pairs of Ha.

Schematic diagram:

1 boiler

2 condenser

3Rurating valve

4 evaporator

5 adsorber

6 Regulating valve

7 pump for pumping mixture

As a rule, water is used as an absorber, and as ha ammonia or bromine lithium.

Principle of operation:

In the boiler, the rich ha mixture is heated either by steam or email. Energy. When heating, the ammonia pairs are released from the mixture, and the pressure in the boiler grows to the condensation pressure. Next, the ammonia pairs pass the transformation chain:

Condensed into liquid state

It is throttled in the adjusting valve 3 with a pressure drop to the initial value and temperature

Then liquid ammonia enters the evaporator 4, from it the ammonia pairs go to 5. Absorber, as well as condensate, is cooled with water, and in it the water-free mixture absorbs the ammonia pairs, enriched with an additional amount of gas.

This mixture of pump 7 is pumped into a boiler 1, at the same time a depleted water-free mixture through the 2nd regulating valve flows from a boiler into the absorber. Thus, in the absorption machine you can distinguish 2 traffic circuit:

For ammonia: Boiler - CD - regulating valve 3-Evapor-absorber

For a water-free mixture: Boiler - Control Valve 6 - Absorber - Pump - Boiler

6. The outer air, regardless of the load in the room, is processed so that the values \u200b\u200bof temperature and humidity parameters are constant at any time of the year, that is, a point behind the irrigation chamber is fixed. Wet apparatus is used for air treatment. This is an apparatus in which the thermal magazine air treatment is produced. It may be an irrigation chamber or a surface irrigated air cooler. When a sufficient amount of water is submitted, the process ends at J \u003d 85 ¸90%, that is, with real air processing processes in irrigation chambers, the ultimate moisture does not reach the value J \u003d 100%. The reason for this is the change in water temperature and short-term air contact.

The first adjustment node captures the outdoor air parameters after the "wet apparatus". Conditionally this is an irrigation chamber point and indirectly supports the humidity of the room.

Calculation of the air stroke system at the workplace of the metal progress

Air stamp is one of the most effective measures to combat radiant heat, as well as with toxic gases and pairs excreted when working in blacksmithing hammer and presses. Served from above through special devices heated (in winter) and cooled (summer) air supplies with a freshly humidized air, and the adjustment of the air movement speed can be achieved and partially decrease the air temperature at the workplace. Sometimes the air is fed to the workplace by means of flexible rubberized hoses from the mobile air fragrant installation. The appearance of the fragrant installation is depicted in fig. 3.4.

Figure 3.4 - Stringing Installation

Calculation of the air shower, we carry out according to the method of Zlobinsky B.M.

The calculation of the air shower is reduced to the determination of the diameter of the shower and the parameters of the air overlooking it.

The diameter of the cross section of the jet is calculated by Formula 2:

where is a turbulence-cell, depending on the shape of the output section (0.06 - 0.12). Let's take \u003d 0.12.

x-Transfer from the place of the jet exit from the nozzle to the workplace. Let's take x \u003d 2 m.

d 0 - the diameter of the output section of the pipe. Let's take 0 \u003d 0.7.

The speed with which the air comes out of the nozzle is calculated by the formula:

where the bad is the average air speed on the workstation. This speed should not exceed 0.3 m / s. We take the bad \u003d 0.3 m / s;

b is a coefficient varying from 0.05 to 1, depending on the relationship. We accept D R.PL. \u003d 2 m, then:

We substitute the obtained values \u200b\u200bin (3) and we get that

The required temperature at the outlet of the pipe is determined by the formula:

where t o.c. - ambient temperature, it is 20-25 0 C. We will take 22.5 0 S.

t CP is the average desired air temperature on the melting area. According to the standards of SanPine 2.2.4.548-96, the permissible temperature on the site 19-21 0 s, we take 20 0 S.

C is the coefficient depending as well as the ratio from the relationship and varies from 0.345 to 0.22. We will take C \u003d 0.25.

Thus, so that the temperature in the melting pad is equal to 20 0 C. The air jet d \u003d 2.05 m is provided at T Pat \u003d 19.3 0 C, which is supplied to the melting platform with a fan at a speed of 0.15 m / s and Performance 1800 m 3 / h.

Calculation of the economic efficiency of the installation of the air stroke system of the VD-1800 type at the workplace of the metal populator will be produced in the organizational and economic section of the thesis project.

Diseases caused by the impact of the heating microclimate of foundry (hot) workshops and their warning

The heating microclimate is a combination of parameters in which the change in the heat transfer of a person with the environment has been occurring, manifested in the accumulation of heat in the body (\u003e 2 W) and / or in increasing the share of heat losses by evaporation of moisture (\u003e 30%). The impact of the heating microclimate also causes a violation of health status, a decrease in working capacity and labor productivity.

Work in such conditions can lead to discomfort to thermostat, significant stress of thermoregulation processes, and with a high heat load - and to violation of health (overheating).

This kind of microclimate is created in rooms where technology is associated with significant heat discharges into the environment, that is, when production processes are coming at high temperatures (firing, calcination, sintering, smelting, cooking, drying). Heating sources are heated to high temperature surfaces of equipment, fences, processed materials, cooled products, knocking through disability of hot pairs and gases. Heat release is also determined by the operation of machines, machines, as a result of which mechanical and electrical energy goes into thermal.

1700 W / m2. Air temperature in the working area \u003d 25 0s. According to the table. 4.23 Average temperature \u003d 19 0 ° C, air mobility in the workplace

2.3 m / s. The distance from the stitching nozzle to the working x \u003d 1.8 m.

With the adiabatic cooling process at the outlet of the nozzle chamber, the air temperature is 18.5 0s.

We accept expanding PDN-4 pipe

Sizes 630 mm H1 \u003d 1540 mm L1 \u003d 1260 mm

Calculated area 0.23 m2

The coefficient M \u003d 4.5 n \u003d 3.1 \u003d 3.2 \u003d 00-200

Determine the area of \u200b\u200bthermal cross section of the pipe:

Table value \u003d 0.23 m2

We find air velocity at the outlet of the pipe:

We establish the air flow rate supplied by the fragrant nozzle:

In the cold period of the year and in transition conditions, the temperature and speed of air movement in the workplace must be in such limits:

18 ... 19 0s \u003d 2.0 ... 2.5 m / s \u003d 16 0s

We remain unchanged for a warm period, we determine the temperature of the air at the outlet of the fragrant nozzle at \u003d 16 0s and \u003d 19 0s using the formula:

Ventilation Cabronechikov

Ventilation system of crane workers with outdoor air supply. Ventilation should provide a sub-in line in stock 10-15 Pa.

The cabin ventilation system with the feed of the outer air is carried out according to the diagram shown in Fig. 1. The design contains a collector located along the path of the crane movement, the intake device moving in the collector's gap and rigidly connected from the crane driver. A rubber tape or hydraulic shutter is used as a sealing device of the collector.

Fig. one - Ventilation of the crane cabin with air supply through the collector: 1 - collector, 2 - fan, 3 - crane cabin, 4 - muffler, 5 - Sealing rubber tube

Local exhaust ventilation

Local compartments from the equipment of the highlighting pairs, gases, bad smells

Calculation of the umbrella - visor over the loading hole of the heating furnace

The umbrella - the visor over the loading hole of the furnace is designed to capture the flow of gases overlooking the hole under the influence of overpressure in the furnace. The dimensions of the suction opening of the umbrella must correspond to the size of the suction jet, taking into account its curvature under the action of gravitational forces (Fig. 2.)

Fig. 2.

We define the volume of the removed air and the size of the umbrella - the visor at the thermal furnace having the loading hole with the size of H? B \u003d 0.5? 0.5 m. In the furnace, the gas temperature is maintained Tg \u003d 1150 ° C, air temperature in the working area \u003d 25 0

1. We define the average speed, with which the gases are knocked out of the opening of the furnace, pre-calculate:

where is the flow rate of 0.65

Overpressure in the furnace, pas

h0 - Half of the height of the loading hole, m

and - the density of the air of the working area and gases of the ovens, respectively, kg / m3

2. The volume of gases coming out of the workflow of the furnace, M3 / s

where - the area of \u200b\u200bthe working side of the furnace, m2

2.78 (0.5? 0.5) \u003d 0.69 m3 / s

0,690,25 \u003d 0.17 kg / s

3. Calculate the criterion of Archimedes

where - the equivalent diameter of the working pass, M

and - the temperature of respectively gases in the furnace and air in the working area, to

Archimedes criterion at m

4. The distance on which the axis of the flow of gases from the gravitational forces, which reaches the plane of the suction opening of the zone, m

where m, n is the coefficients of change of speed and temperature at the ratio of the height of the loading hole H to its width and in the range of 0.5 ... 1 are used equal, respectively, 5 and 4.2. Determine the distance x at h0 \u003d 0.25 m \u003d 5 n \u003d 4.2

5. Gas stream diameter at a distance x

0.565 + 0.440,653 \u003d 0.852 m

6. Find departure and width of the umbrella

B \u003d B + (150 ... 200) \u003d b + 0.2 \u003d 0.5 + 0.2 \u003d 0.7 m

7. Determine the flow rate of a suction mixture of gases and air:

8. Air intake air consumption:

0,727-0.69 \u003d 0.037 m3 / s

0.0371.18 \u003d 0.044 kg / s

9. The temperature of the mixture of gases and mixtures, 0s

Which is unacceptably high and for natural (< 300 0С) и для механической (< 80 0С). Принимаем =300 0C, когда расход подсасываемого воздуха м/с, увеличивается до значения:

Summary:

We define the height of the chimney to remove the resulting mass of the air. Let's take the diameter of the pipe DT \u003d 500 mm

cross-section area:

0,7850,52 \u003d 0.196 m2

Air speed in the pipe M / s

Pre-set the height of the pipe HTP \u003d 6 m. On the pipe head, we install a deflector with a diameter DEF \u003d 500 mm, the height of the deflector HDEF \u003d 1,7ddef \u003d 1,70.5 \u003d 0.85 m

The coefficient of local resistance of the deflector

The coefficient of local resistance umbrella

Pressure loss in the exhaust pipe along with the deflector, taking into account the pollution of the walls, determine by the formula:

We clarify the approximate height of the exhaust pipe from the equality:

The outdoor temperature TN \u003d 21.2 0s, then:

Height of the umbrella:

We substitute the values \u200b\u200bin the formula:

5.73 m close to pre-applicable