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Condensing units (CCUs) for ventilation cooling are becoming more widespread in the design of central cooling systems for buildings. Their advantages are obvious:

Firstly, this is the price of one kW of cold. Compared to chiller systems, supply air cooling with the KKB does not contain an intermediate refrigerant, i.e. water or antifreeze solutions, therefore it is cheaper.

Secondly, the convenience of regulation. One condensing unit works for one supply unit, therefore the control logic is the same and is implemented using standard controllers for supply units.

Thirdly, the ease of installation of the KKB for cooling the ventilation system. No need for additional air ducts, fans, etc. Only the evaporator heat exchanger is built in and that's it. Even additional insulation of the supply air ducts is often not required.

Rice. 1. KKB LENNOX and a diagram of its connection to the supply unit.

Against the background of such remarkable advantages, in practice, we are faced with many examples of air conditioning ventilation systems in which KKBs either do not work at all or fail very quickly during operation. Analysis of these facts shows that the reason is often the wrong selection of the KKB and the evaporator for cooling the supply air. Therefore, we will consider the standard methodology for the selection of condensing units and try to show the mistakes that are made in this case.

WRONG, but the most common, method of selection of KKB and evaporator for direct-flow supply units

1. As initial data, we need to know the air flow supply unit... Let's set for example 4500 m3 / h.
2. The supply unit is direct-flow, i.e. no recirculation, operates on 100% outdoor air.
3. Let's define the construction area - for example, Moscow. Estimated parameters of outdoor air for Moscow + 28C and 45% humidity. We take these parameters as the initial parameters of the air at the inlet to the evaporator of the supply system. Sometimes the air parameters are taken "with a margin" and set + 30C or even + 32C.
4. Let's set the required air parameters at the outlet of the supply system, i.e. at the entrance to the premises. Often these parameters are set 5-10C lower than the required supply air temperature in the room. For example, + 15C or even + 10C. We will focus on the average value of + 13C.
5. Further with i-d diagrams (Fig. 2) we build the process of air cooling in the ventilation cooling system. Determine the required consumption of cold in given conditions... In our version, the required cold consumption is 33.4 kW.
6. We select KKB according to the required cold consumption of 33.4 kW. There is the nearest large and the nearest smaller model in the KKB line. For example, for the manufacturer LENNOX these are the models: TSA090 / 380-3 for 28 kW of cold and TSA120 / 380-3 for 35.3 kW of cold.

We accept a model with a margin of 35.3 kW, i.e. TSA120 / 380-3.

And now we will tell you what will happen at the facility during the joint operation of the supply unit and the KKB we have selected according to the method described above.

The first problem is the overestimated productivity of the KKB.

The ventilation air conditioner is matched to the parameters of the outside air + 28C and 45% humidity. But the customer plans to operate it not only when it is + 28C outside, it is often already hot in the premises due to internal heat surpluses starting from + 15C outside. Therefore, the controller sets the supply air temperature to best case+ 20C, and even lower at worst. KKB gives either 100% capacity or 0% (with rare exceptions of modulating control when using VRF outdoor units in the form of KKB). With a decrease in the temperature of the outside (intake) air, the KKB does not decrease its performance (in fact, it even increases a little due to greater supercooling in the condenser). Therefore, with a decrease in the air temperature at the inlet to the evaporator, the KKB will tend to produce a lower air temperature at the outlet from the evaporator. With our calculation data, the outlet air temperature is + 3C. But this cannot be, because the boiling point of freon in the evaporator is + 5C.

Consequently, a decrease in the air temperature at the inlet to the evaporator to + 22C and below, in our case, leads to an overestimated KKB performance. Further, freon does not boil in the evaporator, the liquid refrigerant returns to the compressor suction and, as a result, the compressor fails due to mechanical damage.

But this is where our problems, oddly enough, do not end.

The second problem is the REDUCED EVAPORATOR.

Let's take a close look at the selection of the evaporator. When selecting an air handling unit, specific parameters of the evaporator operation are set. In our case, this is the air temperature at the inlet + 28C and humidity 45% and at the outlet + 13C. Means? the evaporator is selected EXACTLY for these parameters. But what will happen when the air temperature at the inlet to the evaporator is, for example, not + 28C, but + 25C? The answer is quite simple if you look at the heat transfer formula for any surfaces: Q = k * F * (Tv-Tf). k * F - heat transfer coefficient and heat exchange area will not change, these values ​​are constant. Tf - the boiling point of freon will not change, because it is also kept constant at + 5C (in normal operation). But TV - the average air temperature has decreased by three degrees. Consequently, the amount of heat transferred will become less proportional to the temperature difference. But KKB “does not know about it” and continues to deliver the required 100% performance. The liquid freon returns to the compressor suction again and leads to the above problems. Those. the design temperature of the evaporator is the MINIMUM operating temperature of the KKB.

Here you can argue - "But what about the work of on-off split systems?" the design temperature in the splits is + 27C in the room, but in fact they can work up to + 18C. The fact is that in split systems the surface area of ​​the evaporator is selected with a very large margin, at least 30%, just to compensate for the decrease in heat transfer when the temperature in the room decreases or the fan speed of the indoor unit decreases. And finally,

The third problem is the selection of KKB "WITH A RESERVE" ...

The performance margin when selecting KKB is extremely harmful, because the reserve is liquid freon at the compressor suction. And in the final we have a jammed compressor. In general, the maximum evaporator capacity should always be greater than the compressor capacity.

We will try to answer the question - how is it CORRECT to select KKB for supply systems?

First, it is necessary to understand that the source of cold in the form of a condensing unit cannot be the only one in the building. Air conditioning of the ventilation system can only remove part of the peak load entering the room with ventilation air. And maintaining a certain temperature inside the room in any case falls on local closers ( indoor units VRF or fan coil units). Therefore, the KKB should not maintain a certain temperature when cooling ventilation (this is impossible due to on-off regulation), but reduce heat input into the premises when a certain outside temperature is exceeded.

Example of a ventilation system with air conditioning:

Initial data: the city of Moscow with design parameters for air conditioning + 28C and 45% humidity. Supply air consumption 4500 m3 / h. Heat surplus of the room from computers, people, solar radiation, etc. are 50 kW. The design temperature in the premises is + 22C.

The air conditioning capacity must be selected in such a way that it is sufficient under the worst conditions (maximum temperatures). But ventilation air conditioners should also work without problems with some intermediate options. Moreover, most of the time, ventilation air conditioning systems work just at a load of 60-80%.

• We set the calculated outdoor temperature and the calculated indoor temperature. Those. The main task of the KKB is to cool the supply air to the room temperature. When the outside air temperature is lower than the required room air temperature, the KKB DOES NOT turn on. For Moscow, from + 28C to the required room temperature of + 22C, we get a temperature difference of 6C. In principle, the temperature difference across the evaporator should not be more than 10C, because the supply air temperature cannot be less than the boiling point of freon.

• We determine the required performance of the KKB based on the conditions for cooling the supply air from the design temperature + 28C to + 22C. It turned out 13.3 kW of cold (i-d diagram).

• We select according to the required performance 13.3 KKB from the line of the popular manufacturer LENNOX. We select the nearest SMALL KKB TSA036 / 380-3s with a capacity of 12.2 kW.

• We select the supply evaporator from the worst parameters for it. This is the outdoor temperature equal to the required room temperature - in our case + 22C. The cooling capacity of the evaporator is equal to that of the KKB, i.e. 12.2 kW. Plus a 10-20% capacity margin in case of fouling of the evaporator, etc.

• Determine the supply air temperature at an outdoor temperature of + 22C. we get 15C. Above the boiling point of freon + 5C and above the dew point temperature of + 10C, which means that insulation of the supply air ducts can be omitted (theoretically).

• We determine the remaining heat surplus of the premises. It turns out 50 kW of internal heat surplus plus a small part of the supply air 13.3-12.2 = 1.1 kW. Total 51.1 kW - design capacity for local control systems.

Conclusions: The main idea that I would like to draw your attention to is the need to calculate the compressor condensing unit not for the maximum outside air temperature, but for the minimum in the range of operation of the ventilation air conditioner. The calculation of the KKB and the evaporator, carried out at the maximum temperature of the supply air, leads to the fact that normal operation will be only at the range of outdoor temperatures from the calculated one and above. And if the outside temperature is lower than the calculated one, there will be incomplete boiling of freon in the evaporator and the return of liquid refrigerant to the compressor suction.

Evaporators

In the evaporator, the liquid refrigerant boils and turns into a vapor state, removing heat from the medium to be cooled.

Evaporators are subdivided:

by the type of medium to be cooled - for cooling gaseous media (air or other gas mixtures), for cooling liquid heat carriers (coolants), for cooling solids (products, technological substances), evaporators-condensers (in cascade refrigeration machines);

depending on the conditions of movement of the media to be cooled - from natural circulation cooled medium, with forced circulation of the medium to be cooled, for cooling stationary media (contact cooling or freezing of products);

by filling method - flooded and non-flooded types;

according to the method of organizing the movement of the refrigerant in the apparatus - with natural circulation of the refrigerant (circulation of the refrigerant under the influence of the pressure difference); with forced circulation of the coolant (with a circulation pump);

depending on the way of organizing the circulation of the liquid to be cooled - with a closed system of the cooled liquid (shell-and-tube, shell-and-shell), with open system cooled liquid (panel).

Most often, the medium for cooling is air - a universal heat carrier that is always available. Evaporators differ in the type of channels in which the refrigerant flows and boils, the profile of the heat exchange surface and the organization of air movement.

Types of evaporators

Sheet-tube evaporators are used in household refrigerators. Made from two sheets with stamped channels. After aligning the channels, the sheets are connected by roller welding. The assembled evaporator can be given the appearance of a U- or O-shaped structure (in the form of a low-temperature chamber). The heat transfer coefficient of sheet-tube evaporators is from 4 to 8 V / (m-square * K) at temperature head 10 K.

a, b - O-shaped; в - panel (evaporator shelf)

Smooth tube evaporators are coiled tubes that are braced or brazed to the racks. For ease of installation, smooth-tube evaporators are made in the form of wall-mounted batteries. A battery of this type (wall-mounted smooth-tube evaporating batteries of the BN and BNI types) is used on ships to equip chambers for storing food products. For cooling the provision chambers, smooth-tube wall batteries designed by VNIIkholodmash (ON26-03) are used

Finned tube evaporators are most widely used in commercial refrigeration equipment. Evaporators are made of copper pipes with a diameter of 12, 16, 18 and 20 mm with a wall thickness of 1 mm or brass tape L62-T-0.4 with a thickness of 0.4 mm. To protect the surface of the pipes from contact corrosion, they are coated with a layer of zinc or chromium-plated.

To equip refrigerating machines with a capacity of 3.5 to 10.5 kW, IRSN evaporators are used (wall-mounted finned tube evaporator). The evaporators are made of a copper pipe with a diameter of 18 x 1 mm, the fins are made of a brass strip 0.4 mm thick with a fin pitch of 12.5 mm.

Finned tube evaporator equipped with a fan for forced circulation air, received the name of the air cooler. The heat transfer coefficient of such a heat exchanger is higher than that of a finned evaporator, and therefore the dimensions and weight of the apparatus are smaller.

evaporator failure technical heat transfer

Shell and tube evaporators are evaporators with a closed circulation of the cooled liquid (heat carrier or liquid process medium). The liquid to be cooled flows through the evaporator under the pressure generated by the circulation pump.

In shell and tube flooded type evaporators, the refrigerant boils on the outside of the tubes and the liquid to be cooled flows inside the tubes. Closed system circulation allows to reduce the refrigeration system by reducing contact with air.

For cooling water, shell-and-tube evaporators are often used with boiling of the refrigerant inside the pipes. The heat exchange surface is made in the form of pipes with internal ribbing and the coolant boils inside the pipes, and the cooled liquid flows in the annular space.

Operation of evaporators

· When using evaporators, it is necessary to comply with the instructions of the manufacturers, these Rules and production instructions.

· When the pressure on the discharge lines of the evaporators is higher than that provided for by the project, the electric motors and coolants of the evaporators must be automatically turned off.

It is not allowed to operate evaporators with faulty or off ventilation, with faulty instrumentation or their absence, in the presence of a gas concentration in the room exceeding 20% ​​of the lower concentration limit spreading the flame.

· Information on the operating mode, the number of hours worked by the compressors, pumps and evaporators, as well as malfunctions in the work should be reflected in the operating log.

· The withdrawal of the evaporators from the operating mode to the reserve must be carried out in accordance with the production instructions.

· After shutting down the evaporator, the shut-off valves on the suction and discharge lines must be closed.

Air temperature in the evaporating compartments in work time must be at least 10 ° C. When the air temperature is below 10 ° C, it is necessary to drain the water from the water supply system, as well as from the cooling system of the compressors and the heating system of the evaporators.

The evaporation compartments must be technological schemes equipment, pipelines and instrumentation, operating instructions for installations and operational logs.

· Maintenance Evaporators are carried out by operating personnel under the guidance of a specialist.

· Maintenance evaporative equipment includes maintenance and inspection operations, partial disassembly of equipment with repair and replacement of wearing parts and parts.

When operating the evaporators, the requirements for safe operation pressure vessels.

Maintenance and repair of evaporators should be carried out in the amount and terms specified in the manufacturer's passport. Maintenance and repair of gas pipelines, fittings, safety automation devices and instrumentation of evaporators should be carried out within the time limits established for this equipment.

Operation of evaporators is not allowed in the following cases:

1) increase or decrease in pressure of the liquid and vapor phases above or below the established norms ;

2) malfunctions of safety valves, instrumentation and automation equipment;

3) failure to verify control and measuring devices;

4) faulty fasteners;

5) detecting gas leakage or sweating in welds, bolted connections, as well as violations of the integrity of the evaporator structure;

6) ingress of the liquid phase into the gas pipeline of the vapor phase;

7) stopping the supply of the coolant to the evaporator.

Evaporator repair

Evaporator too weak ... Generalization of symptoms

In this section, we will use the term “evaporator too weak” to mean any malfunction that results in an abnormal decrease in cooling capacity due to the fault of the evaporator itself.

Diagnostic algorithm

A “too weak evaporator” fault and, as a consequence, an abnormal drop in evaporating pressure is most easily identified, since this is the only malfunction in which normal or slightly reduced superheating occurs simultaneously with an abnormal drop in evaporating pressure.

Practical aspects

3 tubes and heat exchange fins of the evaporator are dirty

The risk of this defect arises mainly in installations that are poorly maintained. A typical example of such an installation is an air conditioner that does not have an air filter at the inlet to the evaporator.

When cleaning the evaporator, it is sometimes sufficient to blow through the ribs with a jet compressed air or nitrogen in the direction opposite to the movement of air during operation of the unit, but in order to completely cope with dirt, it is often necessary to use special cleaning and detergents... In some particularly severe cases, it may even be necessary to replace the evaporator.

Dirty air filter

In air conditioners, contamination of the air filters installed at the inlet to the evaporator leads to an increase in the resistance to air flow and, as a result, to a decrease in the air flow through the evaporator, which leads to an increase in the temperature difference. Then the repairman must clean or change the air filters (for filters of similar quality), not forgetting to provide free access to outside air when installing new filters.

It is helpful to remember that the air filters must be in perfect condition. Especially at the outlet facing the evaporator. The filter material should not be torn or lost thickness during repeated washes.

If the air filter is in poor condition or is not suitable for a given evaporator, dust particles will not be well captured and over time will cause fouling of the evaporator tubes and fins.

Evaporator fan belt slips or torn

If the fan belt (or belts) slips, the fan speed decreases, which leads to a decrease in air flow through the evaporator and an increase in the air temperature difference (in the limit, if the belt is torn, there is no air flow at all).

Before tightening the belt, the repairer should check its wear and, if necessary, replace it. Of course, the repairer should also check the alignment of the belts and completely inspect the drive (cleanliness, mechanical clearances, grease, tension) and the condition of the drive motor with the same care as the fan itself. Each repairer, of course, cannot have all existing models of drive belts in stock in his car, so you first need to check with the client and choose the right kit.

Poorly adjusted pulley with variable chute width

Most modern air conditioners are equipped with fan drive motors, on the axis of which a pulley of variable diameter (variable chute width) is installed.

At the end of the adjustment, it is necessary to fix the movable cheek on the threaded part of the hub using a locking screw, while the screw should be tightened as tightly as possible, carefully making sure that the screw leg rests on a special flat on the threaded part of the hub and prevents damage to the thread. V otherwise If the thread is crushed by the locking screw, further adjustment of the groove depth will be difficult, if not impossible. After adjusting the pulley, in any case, check the amperage consumed by the electric motor (see the description of the next malfunction).

High pressure losses in the evaporator air path

If the variable-diameter pulley is adjusted to the maximum fan speed, and the air flow remains insufficient, which means that the losses in the air path are too large in relation to the maximum fan speed.

After you are firmly convinced that there are no other malfunctions (a shutter or valve is closed, for example), it should be considered advisable to replace the pulley in such a way as to increase the fan speed. Unfortunately, increasing the fan speed not only requires replacing the pulley, but also entails other consequences.

The evaporator fan rotates in the opposite direction

The risk of such a malfunction always exists when commissioning a new installation when the evaporator fan is equipped with a three-phase drive motor (in this case, it may be sufficient to swap two phases in order to restore the desired direction of rotation).

The fan motor, being designed for power supply from a 60 Hz mains, is connected to a 50 Hz mains

This problem, fortunately quite rare, can mainly affect motors manufactured in the USA and intended to be connected to a 60 Hz AC mains. Note that some motors manufactured in Europe for export may also require a 60 Hz supply frequency. To quickly understand the cause of this malfunction, you can very simply just read the repairman specifications motor on a special plate attached to it.

3 pollution a large number evaporator fins

If many fins of the evaporator are covered with dirt, resistance to air movement through it increased, which leads to a decrease in air flow through the evaporator and an increase in the air temperature difference.

And then the repairman will have no choice but to thoroughly clean the contaminated parts of the evaporator fins on both sides using a special comb with a tooth pitch that exactly matches the distance between the fins.

Evaporator maintenance

It consists in providing heat removal from the heat transfer surface. For this purpose, the supply of liquid refrigerant to the evaporators and air coolers is regulated to create the required level of flooded systems or in the amount required to ensure optimal superheating of the exhaust steam in non-flooded systems.

The safety of work largely depends on the regulation of the refrigerant supply and the order of switching on and off the evaporators. evaporative systems... The regulation of the refrigerant supply is carried out in such a way as to prevent the breakthrough of vapors from the side high pressure... This is achieved by smooth control operations, maintaining the required level in the linear receiver. When disconnected evaporators are connected to the operating system, it is necessary to prevent the compressor from running wet, which can occur due to the release of steam from the heated evaporator together with drops of liquid refrigerant during its sharp boiling up after careless or thoughtless opening of the shut-off valves.

The procedure for connecting the evaporator, regardless of the duration of the shutdown, must always be as follows. Cut off the supply of refrigerant to the running evaporator. Close the suction valve on the compressor and gradually open the shut-off valve on the evaporator. Thereafter, the suction valve of the compressor is also gradually opened. Then the supply of refrigerant to the evaporators is controlled.

To ensure efficient heat transfer in evaporators refrigeration units with brine systems, ensure that the entire heat transfer surface is immersed in the brine. In evaporators open type the brine level should be 100-150 mm above the evaporator section. When operating shell-and-tube evaporators, the timely release of air through the air taps is monitored.

When servicing evaporative systems, they monitor the timeliness of thawing (warming up) the frost layer on the batteries and air coolers, check if the melt water drainage pipeline is frozen, monitor the operation of the fans, the tightness of closing hatches and doors in order to avoid losses of cooled air.

During defrosting, the uniformity of the heating vapor supply is monitored, avoiding uneven heating of individual parts of the apparatus and not exceeding the heating rate of 30 S h.

The supply of liquid refrigerant to air coolers in non-pumping units is controlled by the circuit according to the level in the air cooler.

In installations with a pumping circuit, the uniformity of the flow of refrigerant into all air coolers is controlled depending on the freezing rate.

Bibliography

Installation, operation and repair refrigeration equipment... Textbook (Ignatiev V.G., Samoilov A.I.)

In the evaporator, the process of transition of the refrigerant from the liquid phase state to the gaseous one with the same pressure takes place, the pressure inside the evaporator is the same everywhere. In the process of transition of a substance from liquid to gaseous (its boiling off) in the evaporator - the evaporator absorbs heat, in contrast to the condenser, which releases heat into the environment. then. by means of two heat exchangers, the process of heat exchange takes place between two substances: the cooled substance, which is located around the evaporator and the outside air, which is around the condenser.

The scheme of movement of liquid freon

Solenoid valve - shuts off or opens the refrigerant supply to the evaporator, always either completely open or completely closed (may not be present in the system)

Thermostatic expansion valve (TRV) is precise instrument, regulating the supply of refrigerant to the evaporator, depending on the intensity of boiling of the refrigerant in the evaporator. It prevents liquid refrigerant from entering the compressor.

The liquid freon enters the expansion valve, the refrigerant throttles through the membrane in the expansion valve (freon is sprayed) and begins to boil due to the pressure drop, gradually the drops turn into gas throughout the entire section of the evaporator pipeline. Starting from the expansion valve, the pressure remains constant. Freon continues to boil and in a certain area of ​​the evaporator completely turns into gas and then, passing through the evaporator, the gas begins to be heated by the air that is in the chamber.

If, for example, the boiling point of freon is -10 ° C, the temperature in the chamber is +2 ° C, freon, having turned into a gas in the evaporator, begins to heat up and at the outlet of the evaporator its temperature should be equal to -3, -4 ° C, thus Δt ( the difference between the boiling point of the refrigerant and the temperature of the gas at the outlet of the evaporator) should be = 7-8, this is the normal operation of the system. For a given Δt, we will know that there will be no particles of non-boiled freon at the exit from the evaporator (they should not be), if boiling occurs in the pipe, then not all the power is used to cool the substance. The pipe is insulated so that the freon does not heat up to ambient temperature, because The refrigerant gas cools the compressor stator. If, nevertheless, liquid freon gets into the pipe, it means that the dose of its supply to the system is too large, or the evaporator is weak (short).

If Δt is less than 7, then the evaporator is filled with freon, it does not have time to boil off and the system does not work correctly, the compressor is also filled with liquid freon and fails. Overheating upward is not so dangerous than overheating downward; at Δt ˃ 7, overheating of the compressor stator may occur, but a slight excess of overheating may not be felt by the compressor in any way and it is preferable during operation.

With the help of fans located in the air cooler, the cold is removed from the evaporator. If this did not happen, then the tubes would be covered with ice and at the same time the refrigerant would reach its saturation temperature, at which it stops boiling, and then, even regardless of the pressure drop, liquid freon would enter the evaporator without evaporating, filling the compressor.

→ Installation of refrigeration units

Installation of main apparatus and auxiliary equipment

The main apparatus of the refrigeration unit include apparatus directly involved in mass and heat exchange processes: condensers, evaporators, subcoolers, air coolers, etc. Receivers, oil separators, dirt traps, air separators, pumps, fans and other equipment that are part of the refrigeration unit to auxiliary equipment.

The installation technology is determined by the degree of factory readiness and design features of the apparatus, their weight and the installation design. First, the main devices are installed, which allows you to start laying pipelines. To prevent moistening of the thermal insulation, a layer of waterproofing is applied to the supporting surface of devices operating at low temperatures, laid thermal insulation layer, and then again a layer of waterproofing. To create conditions that exclude the formation of thermal bridges, all metal parts (fastening belts) are placed on the apparatus through antiseptic wooden bars or gaskets 100-250 mm thick.

Heat exchangers. Majority heat exchangers factories supply ready for installation. So, shell-and-tube condensers, evaporators, subcoolers are supplied assembled, element, irrigation, evaporative condensers and panel, submersible evaporators are supplied as assembly units. Finned tube evaporators, direct expansion coils and brine can be fabricated on site by the installer from finned tube sections.

Shell-and-tube devices (as well as tank equipment) are mounted in a flow-combined manner. When laying welded machines on supports, make sure that all welded seams are accessible for inspection, tapping with a hammer during inspection, as well as for repair.

The horizontality and verticality of the apparatus are checked by level and plumb line or with the help of geodetic instruments. The permissible deviations of the apparatus from the vertical are 0.2 mm, horizontally - 0.5 mm per 1 m. The verticality of shell-and-tube vertical condensers is especially carefully checked, since it is necessary to ensure a film flow of water along the walls of the pipes.

Element capacitors (due to their high metal content, they are used in rare cases in industrial installations) are installed on a metal frame, above the receiver along the elements from bottom to top, adjusting the horizontality of the elements, the uniplanarity of the flanges of the fittings and the verticality of each section.

The installation of irrigation and evaporative condensers consists in the sequential installation of the sump, heat exchange pipes or coils, fans, oil separator, pump and fittings.

Apparatus with air cooled used as condensers in refrigeration units are mounted on a plinth. For centering axial fan Relative to the guide vane, there are slots in the plate, which allow the gear plate to be moved in two directions. The fan motor is aligned to the gearbox.

Panel brine evaporators are placed on insulating layer, on a concrete cushion. The metal tank of the evaporator is installed on wooden beams, mount the mixer and brine valves, connect drain pipe and test the tank for density by bulk water. The water level should not drop during the day. Then the water is drained, the bars are removed and the tank is lowered onto the base. Before installation, panel sections are tested with air at a pressure of 1.2 MPa. Then, one by one, the sections in the tank are mounted, collectors, fittings, a liquid separator are installed, the tank is filled with water and the evaporator assembly is again tested with air at a pressure of 1.2 MPa.

Rice. 1. Installation of horizontal condensers and receivers by the flow-combined method:
a, b - in a building under construction; c - on supports; d - on overpasses; I - position of the capacitor before slinging; II, III - positions when moving the crane boom; IV - installation on supporting structures

Rice. 2. Installation of capacitors:
0 - elemental: 1 - supporting metal structures; 2 - receiver; 3 - capacitor element; 4 - plumb line for verifying the verticality of the section; 5 - level for checking the horizontal element; 6 - a ruler for checking the location of the flanges in one plane; b - irrigation: 1 - water drain; 2 - pallet; 3 - receiver; 4 - sections of coils; 5 - supporting metal structures; 6 - water distribution trays; 7 - water supply; 8 - overflow funnel; in - evaporative: 1 - catchment; 2 - receiver; 3, 4 - level indicator; 5 - nozzles; 6 - droplet separator; 7 - oil separator; 8 - safety valves; 9 - fans; 10 - pre-capacitor; 11 - float water level regulator; 12 - overflow funnel; 13 - pump; d - air: 1 - supporting metal structures; 2 - drive frame; 3 - guiding device; 4 - section of finned heat exchange tubes; 5 - flanges for connecting sections to collectors

Immersion evaporators are mounted in a similar manner and tested with an inert gas pressure of 1.0 MPa for systems with R12 and 1.6 MPa for systems with R22.

Rice. 2. Installation of the panel brine evaporator:
a - testing the tank with water; b - air testing of panel sections; c - installation of panel sections; d - test of the evaporator with water and air as an assembly; 1 - wooden beams; 2 - tank; 3 - stirrer; 4 - panel section; 5 - goats; 6 - air supply ramp for testing; 7 - water drain; 8 - oil sump; 9-liquid separator; 10 - thermal insulation

Capacitive equipment and auxiliary devices. Linear ammonia receivers are mounted on the high pressure side below the condenser (sometimes under it) on the same foundation, and the vapor zones of the apparatus are connected by an equalizing line, which creates conditions for the liquid to drain from the condenser by gravity. During installation, the difference in elevation from the liquid level in the condenser (the level of the outlet pipe from the vertical condenser) to the level of the liquid pipe from the overflow cup of the oil separator And is not less than 1500 mm (Fig. 25). Depending on the brands of the oil separator and the linear receiver, the differences in elevation marks of the condenser, receiver and oil separator Yar, Yar, Nm and Ni, set in the reference literature, are maintained.

On the side low pressure install drainage receivers for draining ammonia from cooling devices during thawing of a snow coat with hot ammonia vapors and protective receivers in non-pumping circuits for receiving liquid in case of its release from the batteries when the heat load increases, as well as circulation receivers. Horizontal circulation receivers are mounted together with liquid separators located above them. In vertical circulating receivers, the vapor from the liquid is separated in the receiver.

Rice. 3. Installation diagram of a condenser, a linear receiver, an oil separator and an air cooler in an ammonia refrigeration unit: КД - condenser; LR - linear receiver; VOT - air separator; SP - overflow glass; MO - oil separator

In aggregated freon units, linear receivers are installed above the condenser (without equalizing line), and freon enters the receiver in a pulsating flow as the condenser fills.

All receivers equip safety valves, pressure gauges, level indicators and valves.

Intermediate vessels are installed on supporting structures on wooden beams, taking into account the thickness of the thermal insulation.

Cooling batteries. Direct refrigeration refrigeration batteries are supplied by manufacturers in a ready-to-install form. Brine and ammonia batteries are manufactured at the installation site. Brine batteries are made of steel welded pipes. For the manufacture of ammonia batteries, seamless hot-rolled steel pipes (usually with a diameter of 38X3 mm) of steel 20 are used for operation at temperatures up to -40 ° C and of steel 10G2 for operation at temperatures up to -70 ° C.

Cold rolled steel strip made of low carbon steel is used for the transverse spiral finning of the tubes of the batteries. Pipes are ribbed on a semi-automatic tooling in the conditions of procurement workshops with a spot check with a probe of the tightness of the fit of the ribbing to the pipe and the specified pitch of the ribbing (usually 20 or 30 mm). Finished pipe sections are hot-dip galvanized. In the manufacture of batteries, semi-automatic welding in carbon dioxide or manual arc welding is used. Finned pipes connect the batteries with collectors or rolls. Collector, rack and coil batteries are assembled from unified sections.

After testing ammonia batteries with air for 5 minutes for strength (1.6 MPa) and for 15 minutes for density (1 MPa), the welded joints are galvanized with an electrometallization gun.

Brine batteries are tested with water after installation at a pressure equal to 1.25 working pressure.

The batteries are attached to embedded parts or metal structures on ceilings (ceiling panels) or on walls (wall panels). Ceiling batteries are fixed at a distance of 200-300 mm from the pipe axis to the ceiling, wall-mounted - at a distance of 130-150 mm from the pipe axis to the wall and at least 250 mm from the floor to the bottom of the pipe. When installing ammonia batteries, the following tolerances are maintained: in height ± 10 mm, deviation from verticality of wall batteries - no more than 1 mm per 1 m of height. When installing batteries, a slope of no more than 0.002 is allowed, and in the direction opposite to the movement of the refrigerant vapor. Wall-mounted batteries are installed by cranes before installing the floor slabs or using loaders with an arrow. Ceiling batteries are mounted using winches through blocks attached to the ceilings.

Air coolers. They are installed on a pedestal (per-staing air coolers) or attached to embedded parts on ceilings (hinged air coolers).

Pedestal air coolers are mounted using the flow-combined method using a jib crane. Before installation, the insulation is laid on a pedestal and a hole is made to connect the drainage pipeline, which is laid with a slope of at least 0.01 towards the drain into the sewer network. Suspended air coolers are mounted in the same way as ceiling radiators.

Rice. 4. Battery installation:
a - batteries by an electric forklift; b - ceiling battery with winches; 1 - overlap; 2- embedded parts; 3 - block; 4 - slings; 5 - battery; 6 - winch; 7 - electric forklift

Glass tube cooling batteries and air coolers. For the manufacture of coil-type brine batteries, glass pipes are used. The pipes are attached to the racks only in straight sections (the rolls are not fixed). The supporting metal structures of the batteries are attached to the walls or suspended from the ceilings. The distance between the posts should not exceed 2500 mm. Wall-mounted batteries to a height of 1.5 m are protected with mesh fences. Glass tubes of air coolers are mounted in a similar way.

For the manufacture of batteries and air coolers, pipes with smooth ends are taken, connecting them with flanges. After the installation is completed, the batteries are tested with water at a pressure equal to 1.25 working pressure.

Pumps. Centrifugal pumps are used to pump ammonia and other liquid refrigerants, refrigerants and chilled water, condensate, and also to empty drainage wells and circulate cooling water. For the supply of liquid refrigerants, only sealed, non-sealed pumps of the KhG type with an electric motor built into the pump housing are used. The stator of the electric motor is sealed, and the rotor is mounted on one shaft with impellers. The shaft bearings are cooled and lubricated with liquid refrigerant taken from the discharge pipe and then bypassed to the suction side. Sealed pumps are installed below the liquid intake point at a liquid temperature below -20 ° C (in order to avoid disruption of the pump, the suction head is 3.5 m).

Rice. 5. Installation and alignment of pumps and fans:
a - installation of a centrifugal pump along the logs using a winch; b - installation of the fan with a winch using guy wires

Before installing the stuffing box pumps, check their completeness and, if necessary, carry out an audit.

Centrifugal pumps are installed on the foundation with a crane, hoist, or along logs on rollers or a sheet of metal using a winch or levers. When installing the pump on a foundation with blind bolts embedded in its array, wooden beams are laid near the bolts so as not to jam the threads (Fig. 5, a). Check the elevation, horizontal position, centering, the presence of oil in the system, the smoothness of rotation of the rotor and the stuffing box packing (stuffing box). Stuffing box

The wives must be carefully stuffed and bent evenly without distortion. Excessive tightening of the stuffing box leads to its overheating and an increase in power consumption. When installing the pump above the receiving tank, a check valve is installed on the suction pipe.

Fans. Most fans are supplied as a unit ready for installation. After installing the fan with a crane or a winch with guy wires (Fig. 5, b) on the foundation, pedestal or metal structures (through vibration-insulating elements), the altitude and horizontal position of the installation are verified (Fig. 5, c). Then they remove the rotor locking device, inspect the rotor and the housing, make sure that there are no dents or other damage, check manually the smoothness of the rotor rotation and the reliability of fastening of all parts. Check the gap between the outer surface of the rotor and the casing (no more than 0.01 of the wheel diameter). The radial and axial runout of the rotor is measured. Depending on the size of the fan (its number), the maximum radial runout is 1.5-3 mm, axial 2-5 mm. If the measurement shows that the tolerance is exceeded, static balancing is carried out. Also measure the gaps between the rotating and stationary parts of the fan, which should be within 1 mm (Fig. 5, d).

During a test run within 10 minutes, the level of noise and vibration is checked, and after a shutdown, the reliability of fastening of all connections, heating of the bearings and the state of the oil system. Duration of tests under load - 4 hours, while checking the stability of the fan under operating conditions.

Installation of cooling towers. Small film-type cooling towers (I PV) are delivered for installation with a high degree of prefabrication. The horizontal installation of the cooling tower is verified, connected to the pipeline system, and after filling the water circulation system with softened water, the irrigation uniformity of the nozzle made of miplastic or PVC plates is adjusted by changing the position of the water spray nozzles.

When installing larger cooling towers, after the construction of the pool and building structures, a fan is installed, its alignment with the cooling tower diffuser is verified, the position of the water distribution troughs or collectors and nozzles is adjusted to evenly distribute water over the irrigation surface.

Rice. 6. Alignment of the coaxiality of the impeller of the cooling tower axial fan with the guide vanes:
a - by moving the frame relative to the supporting metal structures; b - by the tension of the cables: 1 - impeller hub; 2 - blades; 3 - guiding device; 4 - cooling tower cladding; 5 - supporting metal structures; 6 - reducer; 7 - electric motor; 8 - centering cables

The alignment is regulated by moving the frame and the electric motor in the slots for the fastening bolts (Fig. 6, a), and in the largest fans, alignment is achieved by adjusting the tension of the cables attached to the guide vane and supporting metal structures (Fig. 6, b). Then check the direction of rotation of the electric motor, smoothness, beating and vibration level at operating speeds of rotation of the shaft.