Air piping system
The air duct system of special air conditioner for computer room usually consists of motor, fan and air filter.
1. Engine
The motor is completely sealed and air-cooled according to safety standard P54, and has R-class insulation. The motor is installed on the adjustable movable base, and the air volume is adjusted by the motor pulley, which can be described as calibration.
2. Fan
The fan is a centrifugal fan with double width, double inlets and forward blades, and has been tested and adjusted by static and dynamic balance. The low-speed design of the fan minimizes the running noise, and the self-centering bearing and double-belt transmission system ensure the continuous and stable operation of the unit throughout the year.
3. Air filter
In order to meet the requirements of high cleanliness of air-conditioned rooms, an air filter is installed in the air duct system. The filter device is a standard multi-fold replaceable filter screen, and the efficiency value of the filter screen is 25%~30% according to ASHRAE52-76 standard.
4. Air volume adjustment
Mechanical adjustment. In some types of air conditioners, the air volume can be adjusted through adjustable stations and motor pulleys.
Electrical adjustment. The air volume adjustment of most air conditioners is realized by the change of motor speed. The fan motor is designed into multiple groups of taps. According to the wiring position, the adjustable speed is 95r/min, l200r/min and 1400r/min.
Second humidifying device
In IDC computer room, there are not only certain range requirements for temperature, but also strict range requirements for relative humidity. In order to achieve the relative humidity index, a humidification device is installed in the special air conditioner of the machine room, which is controlled by the computer board of the air conditioner of the machine room: when the relative humidity of the machine room is lower than the set lower limit of relative humidity, the humidification cycle is automatically started; When the relative humidity of the machine room is higher than the set upper limit of relative humidity, humidification will automatically stop to keep the relative humidity of the machine room within the normal range.
Humidifiers are divided into infrared humidifiers and electrode boilers according to humidification methods.
1. infrared humidifier
(1) humidifier
The infrared humidifier consists of a high-intensity time lamp, a stainless steel reflector, a stainless steel evaporation water tray, a temperature overheat protector, a water inlet solenoid valve, a manual valve and a humidification water level controller.
(2) The working principle of infrared humidifier
When the relative humidity of the air-conditioned room is lower than the set relative humidity, the computer outputs a humidification signal, and the power supply of the lamp is turned on when the intensity is high. After the water is reflected by the stainless steel reflector, it can be evaporated in s~6s and sent to the air supply system to achieve the purpose of humidification.
The water level control is realized by the float valve, which forms an automatic water supply system together with the water inlet solenoid valve. If there is water supply,
If there is too little water or no water supply, a delay device will automatically cut off the power supply of the contactor coil of the infrared humidifying lamp system and make it stop working. The upper part of the stainless steel reflector and the lower part of the humidifier water tray are provided with overheating protection devices. When the water supply is stopped or the water pressure is insufficient, the equipment will overheat. When the temperature reaches the set value, the protection device will disconnect the working state of the humidifier and trigger the humidification alarm.
2. Electrode boiler humidifier
(1) humidifier
Electrode boiler humidifier consists of electrode boiler, steam nozzle, water inlet solenoid valve, water outlet solenoid valve and water level controller.
(2) Working principle of electrode boiler humidifier.
When the relative humidity of the air-conditioned room is lower than the set relative humidity, the computer outputs the humidification signal, turns on the power supply, opens the electromagnetic valve, and the water will be added to the level of the container. When the electrodes in the humidifier are energized, the generated current will move the ions (impure substances) in the water, gradually raise the temperature, and steam will be generated after reaching the boiling point. Within a few minutes, there is a lot of water vapor in the humidifier water tank, which continuously overflows from the steam outlet pipe, enters the box evaporator and is sent to the computer room by the fan, so that the relative humidity of the environment is improved. During normal operation, the water supply solenoid valve will be opened every few minutes to replenish water. After the humidifier works for a certain period of time, there will be a lot of impurities left in it, especially in areas with poor water quality. These impurities will form a scale layer if they stay for a long time, so the drainage solenoid valve of the system will be opened regularly to discharge the residual water.
Three refrigeration systems
The basic refrigeration system in special air conditioning is mainly composed of compressor, evaporator, condenser and expansion valve.
In order to improve the performance of refrigeration system and achieve better use effect, there are usually many auxiliary devices, such as liquid pipeline electromagnetic valve, liquid observation mirror, liquid pipeline drying filter, high and low pressure controller and so on.
1. compressor
Compressors are divided into three types according to structure: open, semi-closed and fully closed. At present, most of the special air conditioners for computer rooms use fully enclosed compressors, and only some models of Libert air conditioners use semi-enclosed compressors. The fully enclosed refrigeration compressor is a whole formed by installing the compressor and the motor in a closed iron shell at the same time. From the outside, there are only the suction and exhaust pipe joints of the compressor and the wires of the motor. The compressor shell is divided into upper and lower parts. After the compressor and motor are installed, the upper and lower iron shells are welded into a whole by electric welding, which can not be disassembled at ordinary times and has high reliability.
Among the totally enclosed refrigeration compressors, there are piston compressors and scroll compressor.
In the recently produced special air conditioning system for computer room, the compressors used are all fully enclosed scroll refrigeration compressors. Its structure mainly consists of the following items: rotary intake valve, rotary exhaust valve, pressure gauge interface, built-in overload protection, elastic base, crankcase heater and built-in lubricating oil pump.
The biggest advantages of scroll refrigeration compressor are:
(1) has a simple structure. Compressor body only needs two parts (moving plate and fixed plate) to replace 15 parts in piston compressor.
(2) High efficiency. The suction gas is separated from the shift treatment gas to reduce the heat transfer between suction and treatment and improve the efficiency of the compressor.
(3) Low noise. The compression process and transformation process of vortex are very quiet.
Second step evaporator
Classification of (1) evaporators
According to the type of cooled medium, evaporators can be divided into two types: evaporators for cooling liquid (thousand-type evaporator) and evaporators for cooling air (surface cooling evaporator). Evaporators used in air conditioning systems are usually evaporators for cooling air. The liquid freon in the refrigeration system enters the expansion valve and is sent to the evaporator after throttling, which belongs to the vaporization process. At this time, it needs to absorb a lot of heat, and the room temperature will gradually decrease, achieving the effect of refrigeration and dehumidification.
(2) Type A evaporator
The structure of evaporator can be generally divided into single board type, A type and V type, and A type is the most commonly used. A-type evaporator has large windward area and low head-on wind speed to prevent water from being carried against the wind. The evaporator is equipped with 0.5-inch copper tube aluminum fin and stainless steel condensing plate to promote better heat transfer. The evaporator coil is divided into multiple paths and staggered, so that each refrigeration system can be distributed on the windward side of the coil. When a single refrigeration system is running, the sensible heat refrigeration capacity can reach 55%~60% of the total refrigeration capacity.
(3) Dehumidification function of evaporator
In the normal refrigeration cycle, the indoor fan runs at normal speed, providing the design air volume and the most economical energy to meet the requirements of refrigeration capacity.
① Simple dehumidification function
When dehumidification is needed, the compressor runs, but the indoor fan speed is reduced, usually 26% of the original speed, so the air volume is also reduced by 1/3, and the outlet air temperature passing through cooling coils becomes too cold, and the condensation effect is good (that is, the dehumidification capacity is increased).
The disadvantages of increasing dehumidification by this method are:
When the air volume decreases by 1/3, the temperature usually drops by 2C~3C in a few seconds. When the speed of sudden cooling reaches the maximum allowable value, the control reliability will be reduced by lowering lC every 10 minute.
When the air supply volume decreases by 1/3, the filtration efficiency decreases, which has a great influence on the air exchange times and ventilation volume, resulting in the decrease of indoor control accuracy and uneven temperature distribution;
With the decrease of air outlet temperature, it is necessary to turn on the electric heater to improve the room temperature, which leads to inaccurate temperature control and increased operating cost.
② Special dehumidification cycle
The cooling winding is divided into upper and lower parts, accounting for 2/3 of the total cooling winding. In the normal cooling mode, the refrigerant flows through two parts of the cooling winding. In the dehumidification mode, the normally open solenoid valve is closed, thus cutting off the Freon refrigerant leading to the upper winding (1/3 part) of the cooling winding, and all the Freon refrigerant flows to the lower winding (2/3 part) of the cooling winding. The air temperature passing through the lower coil is very low, usually at least 3℃ lower than that in the refrigeration cycle, so the dehumidification effect is increased, but its disadvantage is that the total refrigeration capacity will be reduced and the suction pressure will be reduced.
③ Bypass gas regulator
The bypass gas regulator is installed at the top of Type A evaporator. In the normal cooling mode, the regulator is closed, and all the returned gas passes through the two cooling windings evenly. When dehumidification operation is needed, the bypass gas regulator is fully opened, so that 1/3 of the return air bypasses the top of the A-frame winding without cooling, and the other 2/3 of the return air uniformly passes through the A-frame winding, so that the exhaust gas temperature is rapidly reduced and the dehumidification effect is increased.
This dehumidification method has the same effect as the special dehumidification cycle, and its advantage is that the refrigeration is relatively stable.
3. Capacitor
Condensers can be divided into three types according to their cooling forms: water-cooled, air-cooled, evaporative and shower.
Water-cooled condenser: In water-cooled condenser, the heat released by refrigerant is taken away by cooling water. Cooling water is generally recycled. If some areas are rich in natural water bodies, they can be used once. When using circulating water, a cooling tower or cold water pool is needed. Water-cooled condenser has shell-and-tube structure, sleeve structure and submerged structure.
Air-cooled condenser: In air-cooled condenser, the heat released by refrigerant is taken away by air. Its structural form is mainly composed of several groups of copper pipes. Because of the poor heat transfer performance of air, fins are usually added outside the copper tube to increase the heat transfer area of the air side, and at the same time, fans are used to accelerate the air flow, so that the air is forced to convection and the heat dissipation effect is increased.
Evaporation type and water spray type: In this type of condenser, the refrigerant is condensed in the tube and cooled by water and air at the same time outside the tube.
At present, air-cooled air conditioning is the main type of imported air conditioning for computer rooms. The air-cooled condenser will be described in detail below.
The air-cooled condenser adopts10 copper tube aluminum fin structure, and the fan adopts adjustable speed motor to ensure that the condenser can be used evenly in winter and summer, that is, the condensation pressure will not change greatly in extremely cold and hot environment. The air-cooled condenser is suitable for the ambient temperature range of -30℃~+40℃. When the ambient temperature is high, it will cause the condenser pressure to rise, which will be sensed by the pressure sensor of the governor, and this change will be transformed into the change of output voltage, which will change the motor speed and achieve the purpose of adjusting the forced convection effect. Of course, because of the stepless speed regulation device, the change of motor speed can be smooth. The outdoor condenser of the special air conditioner in the machine room has been adjusted and calibrated before leaving the factory, but the setting drift of the governor occurs from time to time due to the vibration during long-distance transportation or long-term use. If this happens, you can refer to the instructions of the corresponding models to make appropriate adjustments. Usually, the process of adjusting the outdoor unit speed is as follows: when the outdoor unit high pressure is about14kgf/cm2 (14kgf/cm2 = 0.0980665mpa), the fan starts to rotate, reaching the full-load speed at 20~24kgf/cm2 and at14 ~/kloc-0.
4. Thermal expansion valve
Although the thermal expansion valve is only a small component, it plays an indispensable role in the refrigeration system, so it is called the four major components of the refrigeration system together with the refrigeration compressor, evaporator and condenser.
(1) Structure of thermal expansion valve
The appearance of the thermal expansion valve is shown in Figure 2, and its working principle is shown in Figure 3. At the top of the expansion valve, a sealed container is composed of a corrugated film temperature sensor with a sealed box cover and a capillary tube, and Freon is filled into the container to become an induction mechanism. The refrigerant filled in the suction mechanism may be the same as or different from the refrigerant in the refrigeration system. For example, the refrigeration system uses F-22, and the temperature sensor can be filled with F- 12 or F-22. The temperature sensing ball is used to sense the superheated steam temperature at the outlet of the evaporator. As a connecting pipe between the sealed box and the temperature sensing bulb, the capillary tube transfers the pressure to the diaphragm. The transmission diaphragm is stamped from a thin alloy sheet of about 0.2 mm, and its cross section is wavy, so it has good elastic deformation performance after being stressed. The adjusting lever is used to adjust the opening superheat of the expansion valve and the elastic force of the spring during debugging. When the adjusting lever rotates inward, the spring is compressed, and when the adjusting lever rotates outward, the spring is released. The transmission rod pushes the valve needle seat to transmit pressure, and the valve needle is installed on the valve needle seat to open or close the valve hole.
(2) Working principle of thermal expansion valve
The expansion valve senses the change of superheat at the outlet end of the evaporator through the temperature sensing bulb, which leads to the pressure change of the filling material in the temperature sensing system (the temperature sensing system is a closed system composed of the temperature sensing bulb, capillary tube, transmission diaphragm and transmission bellows), and acts on the transmission diaphragm to make the diaphragm move up and down, and then transmits the force to the transmission rod through the transmission diaphragm to push the valve needle to move up and down, so as to close or open the valve. It plays the role of reducing pressure and throttling, automatically adjusts the refrigerant supply of the evaporator, so that the outlet end of the evaporator keeps a certain degree of superheat, thus ensuring the full utilization of the heat transfer area of the evaporator and reducing the phenomenon of liquid colliding with the cylinder.
(3) Types of expansion valves (internal balance and external balance)
The pressure acting on the lower part of the transmission diaphragm in the valve body of the thermal expansion valve is the evaporation pressure after throttling (this pressure enters the space below the diaphragm through the gap between the transmission rod and the transmission plate). This structure is called internal balanced expansion valve.
The pressure acting on the lower part of the transmission diaphragm in the valve body of the thermal expansion valve is not the evaporation pressure after throttling, but the pressure at the outlet end of the evaporator is introduced into the valve of the lower space structure of the transmission diaphragm through the external balance pipe, which is called the external balance thermal expansion valve.
Compared with the internal balance expansion valve, the superheat of the external balance thermal expansion valve is much smaller, so the heat transfer area of the evaporator can be fully exerted and the effect of the refrigeration device can be improved when the external balance thermal expansion valve is adopted. In the case of small evaporator resistance and small pressure loss, the internal balance thermal expansion valve can be selected; When evaporation resistance is high, pressure loss is high or there is a liquid distributor, an external balanced thermal expansion valve should be selected, and the distributor is generally used. External balanced thermal expansion valve is usually used in special air conditioners.
(1) liquid pipeline solenoid valve
The pulse signals from the pressure relay and temperature relay in the refrigeration system can automatically control the solenoid valve in the liquid pipeline. When the compressor stops, due to the inertia and thermodynamic properties of freon, a large amount of freon enters the evaporator. When the compressor starts again, the wet steam enters the suction port of the compressor to cause a wet stroke, which is not easy to start, and even causes the valve plate to rupture in serious cases. The arrangement of the solenoid valve in the liquid pipeline can avoid this situation. In an ideal air conditioning system, the start of the compressor also depends on the solenoid valve. At rest, the solenoid valve divides the high and low pressure into two parts, and the pressure of the low pressure part is lower than the opening value of the low pressure controller, so the compressor is in a stopped state. When the compressor needs to be started, the electromagnetic valve is opened by the computer output signal. When the valve is opened, the high pressure is quickly released to the low pressure. Only when the low pressure reaches the opening value of the low pressure controller can the compressor be started.
(2) liquid mirror
As the name implies, the mirror is used to observe the liquid flow state. According to the number of bubbles, it can be used as a reference for refrigerant injection, and according to the color of the mirror, the water content in the system can be seen. The observation window is located between the refrigeration solenoid valve and the drying filter in the refrigeration system.
(3) Liquid pipeline dry filter
Usually, the liquid pipeline filter is not detachable. The molecular sieve structure is adopted inside, which can remove a small amount of impurities and moisture in the pipeline and achieve the purpose of making a profit. When the filter in the liquid pipeline is blocked, the suction pressure will decrease and the temperature difference will appear at both ends of the filter. If this happens, the filter needs to be replaced.
(4) High and low pressure controller
The high and low pressure controllers in the cooling system are protective devices. High voltage protection is the upper limit protection. When the high pressure reaches the set value, the high pressure controller is disconnected, so that the compressor contactor coil is released, and the compressor stops working, so as to avoid damaging parts when running under ultra-high pressure. The high voltage protection was reset manually. When the compressor starts again, press the reset button first. Of course, before restarting the compressor, you should first check the cause of high pressure, and the machine can operate normally after troubleshooting.
Low pressure protection is a protective device to prevent the refrigeration system from running at too low pressure. Its setting is divided into upper limit and lower limit. The control principle is that the low-pressure disconnection value is the pressure difference between the upper limit and the lower limit, and the restart value is the upper limit. The low-pressure controller is automatically reset, which requires the operator to observe the operation of the machine frequently and deal with the alarm in time to prevent the compressor from starting and stopping frequently for a long time and affecting its service life.