Schematic diagram of air treatment in a local air conditioner with two-stage evaporative cooling. How water conditioners work. Evaporative air cooling What are the advantages of two-stage evaporative air cooling?

additional to auto. certificate Kl, V 60 b 3/04 210627 22) Declared on 01/03/7 by joining the application 3) Priority of the government committee of the USSR Minister of Isovert discoveries Bulletin 47 3) Published 1/25/629, 113/06/628.) Date of publication of the description O 3 O 3 ) Inventor V.V. Utkin Specialized design baro for special tracked tractors of class 2G traction (54) AIR CONDITIONER TWO-STAGE EVAPORATORS 1st COOLING 11 And foam-burning military equipment in heat transfer However 10 efficiency evaporator chamber for necks in the heat exchanger The invention concerns vehicles Two hundred air conditioners are known evaporative cooling, a soda-air heat exchanger and a force chamber for cooling are supplied by a water exchanger made with an air supply from the heat exchanger. The efficiency of evaporative cooling is insufficient. To increase this cooling 1 force cooling, the incoming water is equipped with a channel for supplying air from external environment, separated by a wave-shaped partition from the air supply channel from the heat exchanger, with both channels being made tapering in the direction of the inlet hole of the force night camera.Figure 1 shows the proposed air conditioner, longitudinal section; in fig. 2 - section along A-A in Fig. 1. The air conditioner consists of a fan 1 driven by a motor 2; a water-to-air heat exchanger 3 and a nozzle chamber 4 equipped with a drop catcher 5. Two rows of nozzles 6 are installed in the nozzle chamber 4. The nozzle chamber has an inlet 7 and an outlet 8 and air channel 9. To circulate water in the first stage, a water pump 10 is installed coaxially with the engine, supplying water through pipelines 11 and 12 from tank 13 to injectors 6. In the second stage of the air conditioner, a water pump 14 is installed, supplying water through pipelines 15 and 16 from the tank 17 to the spraying device 18, which wets the irrigated tower 19. A drip eliminator 2 O is also installed here. When the air conditioner is operating, fan 1 drives air through heat exchanger 3, while the air cools, and part of it is directed to the second stage (main flow), and part through channel 9 into the nozzle chamber 4. Channel 9 is made smoothly tapering towards the inlet opening of the nozzle chamber, due to which the flow speed increases into the gaps 21 between channel 9 and through the inlet opening of chamber 7, outside air is sucked in, increasing the mass of the auxiliary flow, which, having passed through chamber 4, is released into the atmosphere through opening 8. The main flow in the second stage passes through the irrigation layer tower 19, where it is additionally cooled and moistened and is directed through the droplet eliminator 20 to serviced room, The water circulating in the first stage is heated in the heat exchanger 3, cooled in the nozzle chamber 4, separated in the droplet eliminator 5 and through hole 22 flows back into the tank 13. The water in the second stage after irrigation of the tower 19 and separation in the dript eliminator 20 through the hole 28 flows into tank 17. Claim 1, Two-stage evaporative cooling air conditioner, primarily for. 4 vehicle containing a water-air heat exchanger and a nozzle chamber for cooling the water entering: the heat exchanger, made with an air supply channel from the heat exchanger, except that, in order to increase the efficiency of evaporative cooling, the nozzle chamber for cooling the incoming The water heat exchanger 10 is equipped with a channel for supplying air from the external environment, separated by a partition from the channel for supplying air from the heat exchanger, and both channels are made tapering towards the 15th inlet of the chamber.2. The air conditioner according to item 1, the only difference is that the partition is wavy.

Application

1982106, 03.01.1974

SPECIALIZED DESIGN BUREAU FOR SPECIAL TRACTOR TRACTORS OF 2T TRAFFIC CLASS

UTKIN VLADIMIR VIKTOROVICH

IPC / Tags

Link code

Air conditioner two-stage evaporative cooling

Similar patents

13 - 15 heat exchangers 10 - 12 are connected to cavity A of the drain chamber 16, cavity B of which is connected by a pipeline 17 with the kingston channel 3. The manifold 6 is hydraulically connected to the tank 18, which is connected by a pipeline 19 to the drain chamber 16, which has an outboard hole 20 and hole 21 in the partition between cavities A and B. The system operates as follows. Cooling pump 4 receives water entering the sea chest 3 through the jumper 2 from the sea chest 1, and supplies it through pressure pipes 5 and 7 - 9 through the manifold 6 to heat exchangers 10 - 12, from which heated water through drain pipes 13 - 15 enters cavity A of drain chamber 16. When cavity A is filled, water flows through hole 21 into...

Ea account thermal radiation from the surface of the heated strip directly to work surface refrigerator located above and below the processed metal with maximum angle coefficients radiation, Fig. 1 shows a device for cooling a hollow in a thermal furnace, section B-B in figure 2; and Fig. 2 convective cooling chamber along the strip, section A-A in Figure 1; Fig. 3 shows the design of an annular gas nozzle. The device for cooling strip 1 moving along Rollers 2 is installed in a thermal unit after radiation cooling chamber 3 and is sealed when the strip exits with a shutter 4. On both sides of the strip being processed there are cylindrical water-cooled surfaces 5, Circulation fan 6...

6 with coolers 7 and 8 oil and fresh water and branch 9 with charge air cooler 10 and muffler 11. Water from branch 6 is drained through the drain keystone 12, and from branch 9 through pipe 13 into the side pipe 14 of muffler 11. Automatic hydraulic resistance 15 installed on branch 6 consists from a body 16 of variable bore area, a cone-shaped plate 17 with a rod 18, a guide bushing 19, fixed to the body 16 by struts 20, a spring 21 and adjusting nuts 22. The system operates as follows. The sea water pump 4 takes water through the receiving seacock 2 and filter 3 and pumps it through branch 6 to oil and fresh water coolers 7 and 8. Through another parallel branch 9, water is supplied to the cooler...

In modern climate control technology Much attention is paid to the energy efficiency of equipment. This explains the recent increased interest in water evaporative cooling systems based on indirect evaporative heat exchangers (indirect evaporative cooling systems). Water evaporative cooling systems may be effective solution for many regions of our country, the climate of which is characterized by relatively low air humidity. Water as a refrigerant is unique - it has a high heat capacity and latent heat of vaporization, is harmless and accessible. In addition, water has been well studied, which makes it possible to fairly accurately predict its behavior in various technical systems.

Features of cooling systems with indirect evaporative heat exchangers

Main feature and the advantage of indirect evaporative systems is the ability to cool the air to a temperature below the wet bulb temperature. Thus, the technology of conventional evaporative cooling (in adiabatic humidifiers), when water is injected into the air flow, not only lowers the air temperature, but also increases its moisture content. In this case, the process line on the I d-diagram of wet air flows adiabatically, but minimally possible temperature corresponds to point “2” (Fig. 1).

In indirect evaporative systems, the air can be cooled to point “3” (Fig. 1). Process diagram in in this case goes vertically down the line of constant moisture content. As a result, the resulting temperature is lower, and the moisture content of the air does not increase (remains constant).

In addition, water evaporation systems have the following positive qualities:

• Possibility of combined production of cooled air and cold water.
• Low power consumption. The main consumers of electricity are fans and water pumps.
• High reliability due to the absence of complex machines and the use of a non-aggressive working fluid - water.
• Ecological cleanliness: low level noise and vibration, non-aggressive working fluid, low environmental hazard industrial production systems due to low manufacturing complexity.
• Simplicity of design and relatively low cost associated with the lack of strict requirements for the tightness of the system and its individual components, the absence of complex and expensive machines ( refrigeration compressors), small excess pressure in the cycle, low metal consumption and the possibility of widespread use of plastics.

Cooling systems that use the effect of heat absorption during water evaporation have been known for a very long time. However, on this moment Water evaporative cooling systems are not widespread enough. Almost the entire niche of industrial and household systems cooling in the region of moderate temperatures is filled with refrigerant vapor compression systems.

This situation is obviously associated with problems in the operation of water evaporation systems when negative temperatures and their unsuitability for operation at high relative humidity of outside air. It was also affected by the fact that the main devices of such systems (cooling towers, heat exchangers), previously used, had large dimensions, weight and other disadvantages associated with working in conditions high humidity. In addition, they required a water treatment system.

However, today thanks technical progress Highly efficient and compact cooling towers have become widespread, capable of cooling water to temperatures that are only 0.8 ... 1.0 ° C different from the temperature entering the cooling tower air flow by wet thermometer.

Here it is worth special mentioning the cooling towers of the companies Muntes and SRH-Lauer. Such a low temperature difference was achieved mainly due to original design cooling tower nozzles with unique properties— good wettability, manufacturability, compactness.

Description of the indirect evaporative cooling system

In an indirect evaporative cooling system atmospheric air from environment with parameters corresponding to point “0” (Fig. 4), is pumped into the system by a fan and cooled at constant moisture content in an indirect evaporative heat exchanger.

After the heat exchanger, the main air flow is divided into two: auxiliary and working, directed to the consumer.

The auxiliary flow simultaneously plays the role of both a cooler and a cooled flow - after the heat exchanger it is directed back towards the main flow (Fig. 2).

At the same time, water is supplied to the auxiliary flow channels. The point of supplying water is to “slow down” the increase in air temperature due to its parallel humidification: as is known, the same change in thermal energy can be achieved either by changing only the temperature or by changing temperature and humidity simultaneously. Therefore, when the auxiliary flow is humidified, the same heat exchange is achieved by a smaller temperature change.

In indirect evaporative heat exchangers of another type (Fig. 3), the auxiliary flow is directed not to the heat exchanger, but to the cooling tower, where it cools the water circulating through the indirect evaporative heat exchanger: the water is heated in it due to the main flow and cooled in the cooling tower due to the auxiliary one. Water moves along the circuit using a circulation pump.

Calculation of indirect evaporative heat exchanger

In order to calculate the cycle of an indirect evaporative cooling system with circulating water, the following initial data are required:

• φ os — relative humidity ambient air,%;
• t ос — ambient air temperature, ° C;
• ∆t x - temperature difference at the cold end of the heat exchanger, ° C;
• ∆t m - temperature difference at the warm end of the heat exchanger, ° C;
• ∆t wgr - the difference between the temperature of the water leaving the cooling tower and the temperature of the air supplied to it according to the wet thermometer, ° C;
• ∆t min - minimum temperature difference (temperature pressure) between the flows in the cooling tower (∆t min<∆t wгр), ° С;
• G r — mass air flow required by the consumer, kg/s;
• η in — fan efficiency;
• ∆P in - pressure loss in the devices and lines of the system (required fan pressure), Pa.

The calculation methodology is based on the following assumptions:

• Heat and mass transfer processes are assumed to be equilibrium,
• There are no external heat inflows in all areas of the system,
• The air pressure in the system is equal to atmospheric pressure (local changes in air pressure due to its injection by a fan or passing through aerodynamic resistance are negligible, which makes it possible to use the I d diagram of humid air for atmospheric pressure throughout the calculation of the system).

The procedure for engineering calculation of the system under consideration is as follows (Figure 4):

1. Using the I d diagram or using the program for calculating moist air, additional parameters of the ambient air are determined (point “0” in Fig. 4): specific enthalpy of air i 0, J/kg and moisture content d 0, kg/kg.
2. The increment in the specific enthalpy of air in the fan (J/kg) depends on the type of fan. If the fan motor is not blown (cooled) by the main air flow, then:

If the circuit uses a duct-type fan (when the electric motor is cooled by the main air flow), then:

Where:
η dv — electric motor efficiency;
ρ 0 — air density at the fan inlet, kg/m 3

Where:
B 0 — ambient barometric pressure, Pa;
R in is the gas constant of air, equal to 287 J/(kg.K).

3. Specific enthalpy of air after the fan (point “1”), J/kg.

i 1 = i 0 +∆i in; (3)

Since the “0-1” process occurs at a constant moisture content (d 1 =d 0 =const), then using the known φ 0, t 0, i 0, i 1 we determine the air temperature t1 after the fan (point “1”).

4. The dew point of the ambient air t dew, °C, is determined from the known φ 0, t 0.

5. Psychrometric temperature difference of the main flow air at the outlet of the heat exchanger (point “2”) ∆t 2-4, °C

∆t 2-4 =∆t x +∆t wgr; (4)

Where:
∆t x is assigned based on specific operating conditions in the range ~ (0.5…5.0), °C. It should be borne in mind that small values ​​of ∆t x will entail relatively large dimensions of the heat exchanger. To ensure small values ​​of ∆t x it is necessary to use highly efficient heat transfer surfaces;

∆t wgr is selected in the range (0.8…3.0), °C; Lower values ​​of ∆t wgr should be taken if it is necessary to obtain the minimum possible cold water temperature in the cooling tower.

6. We accept that the process of humidifying the auxiliary air flow in the cooling tower from state “2-4”, with sufficient accuracy for engineering calculations, proceeds along the line i 2 =i 4 =const.

In this case, knowing the value of ∆t 2-4, we determine the temperatures t 2 and t 4, points “2” and “4” respectively, °C. To do this, we will find a line i=const such that between point “2” and point “4” the temperature difference is the found ∆t 2-4. Point “2” is located at the intersection of the lines i 2 =i 4 =const and constant moisture content d 2 =d 1 =d OS. Point “4” is located at the intersection of the line i 2 =i 4 =const and the curve φ 4 = 100% relative humidity.

Thus, using the above diagrams, we determine the remaining parameters at points “2” and “4”.

7. Determine t 1w - the water temperature at the outlet of the cooling tower, at point “1w”, °C. In the calculations, we can neglect the heating of water in the pump, therefore, at the entrance to the heat exchanger (point “1w’”) the water will have the same temperature t 1w

t 1w =t 4 +.∆t wgr; (5)

8. t 2w - water temperature after the heat exchanger at the inlet to the cooling tower (point “2w”), °C

t 2w =t 1 -.∆t m; (6)

9. The temperature of the air discharged from the cooling tower into the environment (point “5”) t 5 is determined by the graphic-analytical method using an i d diagram (with great convenience, a set of Q t and i t diagrams can be used, but they are less common, therefore in this i d diagram was used in the calculations). The specified method is as follows (Fig. 5):

• point “1w”, characterizing the state of water at the inlet to the indirect evaporation heat exchanger, with the specific enthalpy value of point “4” is placed on the t 1w isotherm, separated from the t 4 isotherm at a distance ∆t wgr.
• From the point “1w” along the isenthalp we plot the segment “1w - p” so that t p = t 1w - ∆t min.
• Knowing that the process of heating the air in the cooling tower occurs at φ = const = 100%, we construct a tangent to φ pr = 1 from point “p” and obtain the tangent point “k”.
• From the point of tangency “k” along the isenthalpe (adiabatic, i=const) we plot the segment “k - n” so that t n = t k + ∆t min. Thus, a minimum temperature difference between the cooled water and the auxiliary air in the cooling tower is ensured (assigned). This temperature difference guarantees the operation of the cooling tower in the design mode.
• We draw a straight line from point “1w” through point “n” until it intersects with the straight line t=const= t 2w. We get point “2w”.
• From point “2w” we draw a straight line i=const until it intersects with φ pr =const=100%. We get point “5”, which characterizes the state of the air at the outlet of the cooling tower.
• Using the diagram, we determine the desired temperature t5 and other parameters of point “5”.

10. We compose a system of equations to find the unknown mass flow rates of air and water. Thermal load of the cooling tower by auxiliary air flow, W:

Q gr =G in (i 5 - i 2); (7)

Q wgr =G ow C pw (t 2w - t 1w); (8)

Where:
C pw is the specific heat capacity of water, J/(kg.K).

Thermal load of the heat exchanger along the main air flow, W:

Q mo =G o (i 1 - i 2); (9)

Thermal load of the heat exchanger by water flow, W:

Q wmo =G ow C pw (t 2w - t 1w) ; (10)

Material balance by air flow:

G o =G in +G p ; (11)

Heat balance for cooling tower:

Q gr =Q wgr; (12)

The heat balance of the heat exchanger as a whole (the amount of heat transferred by each flow is the same):

Q wmo =Q mo ; (13)

Combined thermal balance of the cooling tower and water heat exchanger:

Q wgr =Q wmo; (14)

11. Solving equations from (7) to (14) together, we obtain the following dependencies:
mass air flow along the auxiliary flow, kg/s:

mass air flow along the main air flow, kg/s:

G o = G p ; (16)

Mass flow of water through the cooling tower along the main flow, kg/s:

12. The amount of water required to recharge the water circuit of the cooling tower, kg/s:

G wn =(d 5 -d 2)G in; (18)

13. Power consumption in the cycle is determined by the power spent on the fan drive, W:

N in =G o ∆i in; (19)

Thus, all the parameters necessary for structural calculations of the elements of the indirect evaporative air cooling system have been found.

Note that the working flow of cooled air supplied to the consumer (point “2”) can be additionally cooled, for example, by adiabatic humidification or any other method. As an example in Fig. 4 indicates the point “3*”, corresponding to adiabatic humidification. In this case, points “3*” and “4” coincide (Fig. 4).

Practical aspects of indirect evaporative cooling systems

Based on the practice of calculating indirect evaporative cooling systems, it should be noted that, as a rule, the auxiliary flow rate is 30-70% of the main flow and depends on the potential cooling ability of the air supplied to the system.

If we compare cooling by adiabatic and indirect evaporative methods, then from the I d-diagram it can be seen that in the first case, air with a temperature of 28 ° C and a relative humidity of 45% can be cooled to 19.5 ° C, while in the second case - up to 15°C (Fig. 6).

"Pseudo-indirect" evaporation

As mentioned above, an indirect evaporative cooling system can achieve lower temperatures than a traditional adiabatic humidification system. It is also important to emphasize that the moisture content of the desired air does not change. Similar advantages compared to adiabatic humidification can be achieved through the introduction of an auxiliary air flow.

There are currently few practical applications of indirect evaporative cooling systems. However, devices of a similar, but slightly different operating principle have appeared: air-to-air heat exchangers with adiabatic humidification of the outside air (systems of “pseudo-indirect” evaporation, where the second flow in the heat exchanger is not some humidified part of the main flow, but another, completely independent circuit).

Such devices are used in systems with a large volume of recirculated air that needs cooling: in air conditioning systems for trains, auditoriums for various purposes, data processing centers and other facilities.

The purpose of their implementation is to reduce the operating time of energy-intensive compressor refrigeration equipment as much as possible. Instead, for outside temperatures up to 25°C (and sometimes higher), an air-to-air heat exchanger is used, in which the recirculated room air is cooled by the outside air.

For greater efficiency of the device, the outside air is pre-humidified. In more complex systems, humidification is also carried out during the heat exchange process (water injection into the heat exchanger channels), which further increases its efficiency.

Thanks to the use of such solutions, the current energy consumption of the air conditioning system is reduced by up to 80%. Annual energy consumption depends on the climatic region of operation of the system; on average, it is reduced by 30-60%.

Yuri Khomutsky, technical editor of Climate World magazine

The article uses the methodology of MSTU. N. E. Bauman for calculating the indirect evaporative cooling system.

In heating, ventilation and air conditioning systems, adiabatic evaporation is usually associated with air humidification, but recently the process has become increasingly popular around the world and is increasingly being used to “naturally” cool air.

WHAT IS EVAPORATIVE COOLING?

Evaporative cooling is the basis of one of the very first space cooling systems invented by man, where air is cooled due to the natural evaporation of water. This phenomenon is very common and occurs everywhere: one example would be the feeling of cold you experience when water evaporates from the surface of your body due to the influence of the wind. The same thing happens with the air in which water is atomized: since this process occurs without an external source of energy (this is what the word “adiabatic” means), the heat necessary to evaporate the water is taken from the air, which, accordingly, becomes colder.

The use of this cooling method in modern air conditioning systems provides high cooling capacity with low power consumption, since in this case electricity is consumed only to support the process of water evaporation. At the same time, instead of chemical compounds, ordinary water is used as a coolant, which makes evaporative cooling more economically profitable and does not harm the environment.

TYPES OF EVAPORATIVE COOLING

There are two main methods of evaporative cooling - direct and indirect.

Direct evaporative cooling

Direct evaporative cooling is the process of reducing the temperature of the air in a room by directly humidifying it. In other words, due to the evaporation of atomized water, the surrounding air is cooled. In this case, moisture is distributed either directly into the room using industrial humidifiers and nozzles, or by saturating the supply air with moisture and cooling it in a section of the ventilation unit.

It should be noted that in conditions of direct evaporative cooling, a significant increase in the humidity of the supply air indoors is inevitable, therefore, to assess the applicability of this method, it is recommended to take as a basis the formula known as the “temperature and discomfort index”. The formula calculates the comfortable temperature in degrees Celsius, taking into account humidity and dry bulb temperature readings (Table 1). Looking ahead, we note that the direct evaporative cooling system is used only in cases where the outdoor air in the summer has high dry bulb temperatures and low absolute humidity levels.

Indirect evaporative cooling

To increase the efficiency of evaporative cooling when outdoor air humidity is high, it is recommended to combine evaporative cooling with heat recovery. This technology is known as “indirect evaporative cooling” and is suitable for almost any country in the world, including countries with very humid climates.

The general operating scheme of a supply and ventilation system with recuperation is that hot supply air, passing through a special heat exchange cassette, is cooled by cool air removed from the room. The operating principle of indirect evaporative cooling is to install an adiabatic humidification system in the exhaust duct of supply and exhaust central air conditioners, with subsequent transfer of cold through the recuperator to the supply air.

As shown in the example, due to the use of a plate heat exchanger, the street air in the ventilation system is cooled by 6 °C. The use of evaporative cooling of the exhaust air will increase the temperature difference from 6°C to 10°C without increasing energy consumption and indoor humidity levels. The use of indirect evaporative cooling is effective for high heat fluxes, for example in office and shopping centers, data centers, industrial premises, etc.

Indirect cooling system using the CAREL humiFog adiabatic humidifier:

Case: Estimating the costs of an indirect adiabatic cooling system compared to cooling using chillers.

Using the example of an office center with a permanent residence of 2000 people.

Payment terms
Outdoor temperature and humidity content:	+32ºС, 10.12 g/kg (indicators taken for Moscow)
Room temperature:	+20 ºС
Ventilation system:	4 supply and exhaust units with a capacity of 30,000 m3/h (air supply according to sanitary standards)
Cooling system power including ventilation:	2500 kW
Supply air temperature:	+20 ºС
Extract air temperature:	+23 ºС
Sensible heat recovery efficiency:	65%
Central cooling system:	Chiller-fan coil system with water temperature 7/12ºС

Calculation

• To make the calculation, we calculate the relative humidity of the exhaust air.
• At a temperature in the cooling system of 7/12 °C, the dew point of the exhaust air, taking into account internal moisture releases, will be +8 °C.
• The relative humidity in the exhaust air will be 38%.

*It must be taken into account that the cost of installing a refrigeration system, taking into account all costs, is significantly higher compared to indirect cooling systems.

Capital expenditures

For analysis, we take the cost of equipment - chillers for the refrigeration system and a humidification system for indirect evaporative cooling.

• Capital cost for supply air cooling for an indirect cooling system.

The cost of one Optimist humidification rack manufactured by Carel (Italy) in an air handling unit is 7570 €.

• Capital costs for supply air cooling without an indirect cooling system.

The cost of a chiller with a cooling capacity of 62.3 kW is approximately 12,460 €, based on a cost of 200 € per 1 kW of cooling capacity. It must be taken into account that the cost of installing a refrigeration system, taking into account all costs, is significantly higher compared to indirect cooling systems.

Operating costs

For analysis, we assume the cost of tap water is 0.4 € per 1 m3 and the cost of electricity is 0.09 € per 1 kW/h.

• Operating costs for supply air cooling for an indirect cooling system.

The water consumption for indirect cooling is 117 kg/h for one supply and exhaust unit; taking into account losses of 10%, we will take it as 130 kg/h.

The power consumption of the humidification system is 0.375 kW for one air handling unit.

The total cost per hour is 0.343 € per 1 hour of system operation.

• Operating costs for supply air cooling without an indirect cooling system.

The required cooling capacity is 62.3 kW per air handling unit.

We take the cooling coefficient equal to 3 (the ratio of cooling power to power consumption).

The total cost per hour is 7.48 € per 1 hour of operation.

Conclusion

Using indirect evaporative cooling allows you to:

Reduce capital costs for supply air cooling by 39%.

Reduce energy consumption for the building's air conditioning systems from 729 kW to 647 kW, or by 11.3%.

Reduce operating costs for building air conditioning systems from 65.61 €/hour to 58.47 €/hour, or by 10.9%.

Thus, despite the fact that fresh air cooling accounts for approximately 10–20% of the total cooling needs of office and shopping centers, it is here that there are the greatest reserves for increasing the energy efficiency of a building without a significant increase in capital costs.

The article was prepared by TERMOKOM specialists for publication in ON magazine No. 6-7 (5) June-July 2014 (pp. 30-35)

2018-08-15

The use of air conditioning systems (ACS) with evaporative cooling as one of the energy-efficient solutions in the design of modern buildings and structures.

Today, the most common consumers of thermal and electrical energy in modern administrative and public buildings are ventilation and air conditioning systems. When designing modern public and administrative buildings to reduce energy consumption in ventilation and air conditioning systems, it makes sense to give special preference to reducing power at the stage of obtaining technical specifications and reducing operating costs. Reducing operating costs is most important for property owners or tenants. There are many ready-made methods and various measures to reduce energy costs in air conditioning systems, but in practice the choice of energy-efficient solutions is very difficult.

One of the many HVAC systems that can be considered energy efficient is the evaporative cooling air conditioning systems discussed in this article.

They are used in residential, public and industrial premises. The process of evaporative cooling in air conditioning systems is provided by nozzle chambers, film, nozzle and foam devices. The systems under consideration can have direct, indirect, or two-stage evaporative cooling.

Of the above options, the most economical air cooling equipment is direct cooling systems. For them, it is assumed that standard equipment will be used without the use of additional sources of artificial cold and refrigeration equipment.

A schematic diagram of an air conditioning system with direct evaporative cooling is shown in Fig. 1.

The advantages of such systems include minimal maintenance costs during operation, as well as reliability and design simplicity. Their main disadvantages are the inability to maintain supply air parameters, the exclusion of recirculation in the serviced premises and dependence on external climatic conditions.

Energy consumption in such systems is reduced to the movement of air and recirculated water in adiabatic humidifiers installed in the central air conditioner. When using adiabatic humidification (cooling) in central air conditioners, it is necessary to use potable quality water. The use of such systems may be limited in climate zones with a predominantly dry climate.

Areas of application for air conditioning systems with evaporative cooling are objects that do not require precise maintenance of heat and humidity conditions. Usually they are run by enterprises in various industries, where a cheap way to cool internal air is needed in conditions of high heat intensity of the premises.

The next option for economical cooling of air in air conditioning systems is the use of indirect evaporative cooling.

A system with such cooling is most often used in cases where the internal air parameters cannot be obtained using direct evaporative cooling, which increases the moisture content of the supply air. In the "indirect" scheme, the supply air is cooled in a heat exchanger of the recuperative or regenerative type in contact with an auxiliary air stream cooled by evaporative cooling.

A variant diagram of an air conditioning system with indirect evaporative cooling and the use of a rotary heat exchanger is shown in Fig. 2. Scheme of SCR with indirect evaporative cooling and the use of recuperative heat exchangers is shown in Fig. 3.

Indirect evaporative cooling air conditioning systems are used when supply air is required without dehumidification. The required air parameters are supported by local closers installed in the room. The determination of the supply air flow is carried out according to sanitary standards, or according to the air balance in the room.

Indirect evaporative cooling air conditioning systems use either outside or exhaust air as auxiliary air. If local closers are available, the latter is preferred, as it increases the energy efficiency of the process. It should be noted that the use of exhaust air as auxiliary air is not allowed in the presence of toxic, explosive impurities, as well as a high content of suspended particles contaminating the heat exchange surface.

Outside air is used as an auxiliary flow when the flow of exhaust air into supply air through leaks in the heat exchanger (i.e. heat exchanger) is unacceptable.

The auxiliary air flow is cleaned in air filters before being supplied for humidification. An air conditioning system design with regenerative heat exchangers has greater energy efficiency and lower equipment costs.

When designing and selecting circuits for air conditioning systems with indirect evaporative cooling, it is necessary to take into account measures to regulate heat recovery processes during the cold season in order to prevent freezing of heat exchangers. It is necessary to provide for reheating the exhaust air in front of the heat exchanger, bypassing part of the supply air in a plate heat exchanger and regulating the rotation speed in the rotary heat exchanger.

Using these measures will prevent freezing of heat exchangers. Also in calculations when using exhaust air as an auxiliary flow, it is necessary to check the system for operability during the cold season.

Another energy-efficient air conditioning system is a two-stage evaporative cooling system. Air cooling in this scheme is provided in two stages: direct evaporative and indirect evaporative methods.

“Two-stage” systems provide for more precise adjustment of air parameters when leaving the central air conditioner. Such air conditioning systems are used in cases where greater cooling of the supply air is required compared to direct or indirect evaporative cooling.

Air cooling in two-stage systems is provided in regenerative, plate heat exchangers or in surface heat exchangers with an intermediate coolant using an auxiliary air flow - in the first stage. Air cooling in adiabatic humidifiers is in the second stage. The basic requirements for auxiliary air flow, as well as for checking the operation of SCR during the cold season, are similar to those applied to SCR circuits with indirect evaporative cooling.

The use of air conditioning systems with evaporative cooling allows you to achieve better results that cannot be obtained using refrigeration machines.

The use of SCR schemes with evaporative, indirect and two-stage evaporative cooling allows, in some cases, to abandon the use of refrigeration machines and artificial refrigeration, and also to significantly reduce the refrigeration load.

By using these three schemes, energy efficiency of air handling is often achieved, which is very important when designing modern buildings.

History of evaporative air cooling systems

Over the centuries, civilizations have found original methods to combat the heat in their territories. An early form of cooling system, the “windcatcher,” was invented many thousands of years ago in Persia (Iran). This was a system of wind shafts on the roof that caught the wind, passed it through the water and blew cooled air into the interior. It is noteworthy that many of these buildings also had courtyards with large reserves of water, so if there was no wind, then as a result of the natural process of evaporation of water, hot air rising upward evaporated the water in the courtyard, after which the already cooled air passed through the building. Nowadays, Iran has replaced “wind catchers” with evaporative coolers and uses them widely, and the Iranian market, due to the dry climate, reaches a turnover of 150 thousand evaporators per year.

In the US, the evaporative cooler was the subject of numerous patents in the 20th century. Many of them, dating back to 1906, proposed the use of wood shavings as a gasket, carrying large amounts of water in contact with moving air and maintaining intense evaporation. The standard design from the 1945 patent includes a water reservoir (usually equipped with a float valve to adjust the level), a pump to circulate water through the wood chip pads, and a fan to blow air through the pads into the living areas. This design and materials remain central to evaporative cooler technology in the southwestern United States. In this region they are additionally used to increase humidity.

Evaporative cooling was common in aircraft engines of the 1930s, such as the engine for the Beardmore Tornado airship. This system was used to reduce or completely eliminate the radiator, which would otherwise create significant aerodynamic drag. External evaporative cooling units were installed on some vehicles to cool the interior. They were often sold as additional accessories. The use of evaporative cooling devices in automobiles continued until vapor compression air conditioning became widespread.

Evaporative cooling is a different principle than vapor compression refrigeration units, although they also require evaporation (evaporation is part of the system). In the vapor compression cycle, after the refrigerant evaporates inside the evaporator coil, the cooling gas is compressed and cooled, condensing under pressure into a liquid state. Unlike this cycle, in an evaporative cooler the water evaporates only once. The evaporated water in the cooling device is discharged into a space with cooled air. In a cooling tower, the evaporated water is carried away by the air flow.

1. Bogoslovsky V.N., Kokorin O.Ya., Petrov L.V. Air conditioning and refrigeration. - M.: Stroyizdat, 1985. 367 p.
2. Barkalov B.V., Karpis E.E. Air conditioning in industrial, public and residential buildings. - M.: Stroyizdat, 1982. 312 p.
3. Koroleva N.A., Tarabanov M.G., Kopyshkov A.V. Energy-efficient ventilation and air conditioning systems for a large shopping center // ABOK, 2013. No. 1. pp. 24–29.
4. Khomutsky Yu.N. Application of adiabatic humidification for air cooling // Climate World, 2012. No. 73. pp. 104–112.
5. Uchastkin P.V. Ventilation, air conditioning and heating in light industry enterprises: Textbook. allowance for universities. - M.: Light industry, 1980. 343 p.
6. Khomutsky Yu.N. Calculation of an indirect evaporative cooling system // Climate World, 2012. No. 71. pp. 174–182.
7. Tarabanov M.G. Indirect evaporative cooling of supply external air in SCR with closers // ABOK, 2009. No. 3. pp. 20–32.
8. Kokorin O.Ya. Modern air conditioning systems. - M.: Fizmatlit, 2003. 272 ​​p.

Union of Soviets

Socialist

Republics

State Committee

USSR for Inventions and Discoveries (53) UDC 629. 113. .06.628.83 (088.8) (72) Authors of the invention

V. S. Maisotsenko, A. B. Tsimerman, M. G. and I. N. Pecherskaya

Odessa Civil Engineering Institute (71) Applicant (54) TWO-STAGE EVAPORATORY AIR CONDITIONER

COOLING FOR VEHICLE

The invention relates to the field of transport engineering and can be used for air conditioning in vehicles.

Air conditioners for vehicles are known that contain an air slot evaporator nozzle with air and water channels separated from each other by walls made of microporous plates, while the lower part of the nozzle is immersed in a tray with liquid (1)

The disadvantage of this air conditioner is the low efficiency of air cooling.

The closest technical solution to the invention is a two-stage evaporative cooling air conditioner for a vehicle, containing a heat exchanger, a tray with liquid in which the nozzle is immersed, a chamber for cooling the liquid entering the heat exchanger with elements for additional cooling of the liquid, and a channel for supplying air from the external environment into the chamber , made tapering towards the inlet of the chamber (2

In this compressor, elements for additional air cooling are made in the form of nozzles.

However, the cooling efficiency in this compressor is also insufficient, since the limit of air cooling in this case is the wet bulb temperature of the auxiliary air flow in the pan.

10 In addition, the known air conditioner is structurally complex and contains duplicate components (two pumps, two tanks).

The purpose of the invention is to increase the degree of cooling efficiency and compactness of the device.

The goal is achieved by the fact that in the proposed air conditioner the elements for additional cooling are made in the form of a heat exchange partition located vertically and fixed to one of the chamber walls with the formation of a gap between it and the chamber wall opposite it, and

25, on the side of one of the surfaces of the partition, a reservoir is installed with liquid flowing down the said surface of the partition, while the chamber and the tray are made in one piece.

The nozzle is made in the form of a block of capillary-porous material.

In fig. 1 shows a schematic diagram of an air conditioner; Fig. 2 raeree A-A in Fig. 1.

The air conditioner consists of two stages of air cooling: the first stage is cooling the air in heat exchanger 1, the second stage is cooling it in nozzle 2, which is made in the form of a block of capillary-porous material.

A fan 3 is installed in front of the heat exchanger, driven so rotation by an electric motor 4 °. To circulate water in the heat exchanger, a water pump 5 is installed coaxially with the electric motor, supplying water through pipelines 6 and 7 from chamber 8 to reservoir 9 with liquid. Heat exchanger 1 is installed on a tray 10, which is made integral with the chamber

8. A channel is adjacent to the heat exchanger

11 for supplying air from the external environment, while the channel is made planally tapering in the direction towards the inlet 12 of the air cavity

13 chambers 8. Elements for additional air cooling are placed inside the chamber. They are made in the form of a heat exchange partition 14, located vertically and fixed to the wall 15 of the chamber, opposite the wall 16, relative to which the partition is located with a gap. The partition divides the chamber into two communicating cavities 17 and 18.

The chamber is provided with a window 19, in which a drip eliminator 20 is installed, and an opening 21 is made on the pallet. When the air conditioner is operating, fan 3 drives the total air flow through heat exchanger 1. In this case, the total air flow L is cooled, and one part of it is the main flow L

Due to the execution of channel 11 tapering towards the inlet hole 12! cavity 13, the flow rate increases, and external air is sucked into the gap formed between the mentioned channel and the inlet hole, thereby increasing the mass of the auxiliary flow. This flow enters the cavity 17. Then this air flow, going around the partition 14, enters the chamber cavity 18, where it moves in the opposite direction to its movement in the cavity 17. In the cavity 17, a film 22 of liquid flows down the partition towards the movement of the air flow - water from the reservoir 9.

When the air flow and water come into contact, as a result of the evaporation effect, heat from the cavity 17 is transferred through the partition 14 to the water film 22, promoting its additional evaporation. After this, a flow of air with a lower temperature enters the cavity 18. This, in turn, leads to an even greater decrease in the temperature of the partition 14, which causes additional cooling of the air flow in the cavity 17. Consequently, the temperature of the air flow will decrease again after going around the partition and entering the cavity

18. Theoretically, the cooling process will continue until its driving force becomes zero. In this case, the driving force of the evaporative cooling process is the psychometric temperature difference of the air flow after its rotation relative to the partition and coming into contact with the film of water in cavity 18. Since the air flow is pre-cooled in cavity 17 with a constant moisture content, the psychrometric temperature difference of the air flow in cavity 18 tends to zero as it approaches the dew point. Therefore, the limit of water cooling here is the dew point temperature of the outside air. Heat from the water enters the air flow in cavity 18, while the air is heated, humidified and released into the atmosphere through window 19 and drip eliminator 20.

Thus, in chamber 8, a countercurrent movement of heat-exchanging media is organized, and the separating heat-exchange partition makes it possible to indirectly pre-cool the air flow supplied for cooling water due to the process of water evaporation. The cooled water flows along the partition to the bottom of the chamber, and since the latter is completed in one whole with the tray, then from there it is pumped into heat exchanger 1, and is also spent on wetting the nozzle due to intracapillary forces.

Thus, the main flow of air.L.„, having been pre-cooled without changes in moisture content in heat exchanger 1, is supplied for further cooling to nozzle 2. Here, due to the heat and mass exchange between the wetted surface of the nozzle and the main air flow, the latter is humidified and cooled without changing its heat content. Next, the main air flow through the opening in the pan

59 yes it cools, at the same time cooling the partition. Entering the cavity

17 of the chamber, the air flow flowing around the partition is also cooled, but there is no change in moisture content. Claim

1. A two-stage evaporative cooling air conditioner for a vehicle, containing a heat exchanger, a sub-tank with liquid in which the nozzle is immersed, a chamber for cooling the liquid entering the heat exchanger with elements for additional cooling of the liquid, and a channel for supplying air from the external environment into the chamber, made tapering in direction to the inlet of the chamber, i.e. in that, in order to increase the degree of cooling efficiency and compactness of the compressor, the elements for additional air cooling are made in the form of a heat exchange partition located vertically and mounted on one of the chamber walls with the formation of a gap between it and the chamber wall opposite it, and on the side of one of the On the surface of the partition, a reservoir is installed with liquid flowing down the said surface of the partition, while the chamber and the tray are made as one whole.