Most of the condenser is placed in front of the car water tank, but the parts of the air conditioning system can transfer the heat in the pipe to the air near the pipe in a very fast way. In the distillation process, the device that converts the gas or vapor into a liquid state is called a condenser, but all condensers operate by taking away the heat of the gas or vapor. In the condenser of automobiles, the refrigerant enters the evaporator, the pressure is reduced, and the high-pressure gas becomes a low-pressure gas. This process absorbs heat, so the surface temperature of the evaporator is very low, and then the cold air can be blown out through the fan. Condensation The compressor is the high-pressure, high-temperature refrigerant from the compressor, which is cooled to high pressure and low temperature. Then it is vaporized by capillary tube and evaporated in the evaporator.
Condensers can be divided into four categories: water-cooled, evaporative, air-cooled, and water-sprayed condensers according to their different cooling media：
(1) Water-cooled condenser
The water-cooled condenser uses water as the cooling medium, and the temperature rise of the water takes away the heat of condensation. Cooling water is generally used in circulation, but a cooling tower or a cold pool should be installed in the system. Water-cooled condensers can be divided into vertical shell-and-tube and horizontal shell-and-tube condensers according to their different structures. There are many kinds of tube type and casing type, the most common is shell and tube type condenser.
1. Vertical shell and tube condenser
Vertical shell and tube condenser, also known as vertical condenser, is a water-cooled condenser widely used in ammonia refrigeration systems. Vertical condenser is mainly composed of shell (cylinder), tube sheet and tube bundle.
The refrigerant vapor enters the gap between the tube bundles from the steam inlet at 2/3 of the height of the cylinder, and the cooling water in the tube and the high-temperature refrigerant vapor outside the tube conduct heat exchange through the tube wall, so that the refrigerant vapor is condensed into liquid. It gradually flows down to the bottom of the condenser and flows into the liquid reservoir through the liquid outlet pipe. The heat-absorbing water is discharged into the lower concrete pool, and then pumped into the cooling water tower for cooling and recycling.
In order to distribute the cooling water evenly to each nozzle, the water distribution tank at the top of the condenser is provided with a water distribution plate, and each nozzle on the top of the tube bundle is equipped with a deflector with a chute, so that the cooling water can flow along the inside of the tube. The wall flows downward with a film-like water layer, which can improve heat transfer and save water. In addition, the shell of the vertical condenser is also provided with pipe joints such as pressure equalizing pipe, pressure gauge, safety valve and air discharge pipe, so as to be connected with corresponding pipelines and equipment.
The main features of vertical condensers are:
1. Due to the large cooling flow and high flow rate, the heat transfer coefficient is high.
2. The vertical installation occupies a small area and can be installed outdoors.
3. The cooling water flows straight and has a large flow rate, so the water quality is not high, and the general water source can be used as cooling water.
4. The scale in the tube is easy to remove, and it is not necessary to stop the refrigeration system.
5. However, because the temperature rise of the cooling water in the vertical condenser is generally only 2 to 4 °C, and the logarithmic average temperature difference is generally about 5 to 6 °C, the water consumption is relatively large. And because the equipment is placed in the air, the pipes are easily corroded, and the leakage is easier to find.
2. Horizontal shell and tube condenser
The horizontal condenser and the vertical condenser have a similar shell structure, but there are many differences in general. The main difference is the horizontal placement of the shell and the multi-channel flow of water. The outer surfaces of the tube sheets at both ends of the horizontal condenser are closed with an end cap, and the end caps are cast with water-dividing ribs designed to cooperate with each other, dividing the entire tube bundle into several tube groups. Therefore, the cooling water enters from the lower part of one end cover, flows through each tube group in sequence, and finally flows out from the upper part of the same end cover, which requires 4 to 10 round trips. This can not only increase the flow rate of the cooling water in the tube, thereby improving the heat transfer coefficient, but also make the high-temperature refrigerant vapor enter the tube bundle from the air inlet tube at the upper part of the shell to conduct sufficient heat exchange with the cooling water in the tube.
The condensed liquid flows into the liquid storage tank from the lower liquid outlet pipe. There is also a vent valve and a water drain cock on the other end cover of the condenser. The exhaust valve is on the upper part and is opened when the condenser is put into operation to discharge the air in the cooling water pipe and make the cooling water flow smoothly. Remember not to confuse it with the air release valve to avoid accidents. The drain cock is used to drain the water stored in the cooling water pipe when the condenser is out of use to avoid freezing and cracking of the condenser due to water freezing in winter. On the shell of the horizontal condenser, there are also several pipe joints such as air inlet, liquid outlet, pressure equalizing pipe, air discharge pipe, safety valve, pressure gauge joint and oil discharge pipe which are connected with other equipment in the system.
Horizontal condenser is not only widely used in ammonia refrigeration system, but also can be used in Freon refrigeration system, but its structure is slightly different. The cooling pipe of ammonia horizontal condenser adopts smooth seamless steel pipe, while the cooling pipe of freon horizontal condenser generally adopts low-ribbed copper pipe. This is due to the low exothermic coefficient of Freon. It is worth noting that some Freon refrigeration units generally do not have a liquid storage tank, and only use a few rows of tubes at the bottom of the condenser to double as a liquid storage tank.
For horizontal and vertical condensers, in addition to the different placement positions and water distribution, the water temperature rise and water consumption are also different. The cooling water of the vertical condenser flows down the inner wall of the tube by gravity, and it can only be a single stroke. Therefore, to obtain a large enough heat transfer coefficient K, a large amount of water must be used. The horizontal condenser uses a pump to send the cooling water into the cooling pipe, so it can be made into a multi-stroke condenser, and the cooling water can obtain a sufficiently large flow rate and temperature rise (Δt=4～6℃). Therefore, the horizontal condenser can obtain a sufficiently large K value with a small amount of cooling water.
However, if the flow rate is excessively increased, the heat transfer coefficient K value does not increase much, but the power consumption of the cooling water pump increases significantly, so the cooling water flow rate of the ammonia horizontal condenser is generally about 1m/s. The cooling water flow rate of the device is mostly 1.5 ~ 2m/s. The horizontal condenser has high heat transfer coefficient, small cooling water consumption, compact structure and convenient operation and management. However, the quality of the cooling water is required to be good, and it is inconvenient to clean the scale, and it is not easy to find the leakage.
The vapor of the refrigerant enters the cavity between the inner and outer tubes from above, condenses on the outer surface of the inner tube, and the liquid flows down in sequence at the bottom of the outer tube, and flows into the liquid receiver from the lower end. The cooling water enters from the lower part of the condenser and flows out from the upper part through each row of inner pipes in turn, in a countercurrent manner with the refrigerant.
The advantages of this type of condenser are simple structure, easy to manufacture, and because it is a single-tube condensation, the medium flows in the opposite direction, so the heat transfer effect is good. When the water flow rate is 1 ~ 2m/s, the heat transfer coefficient can reach 800kcal/(m2h °C). The disadvantage is that the metal consumption is large, and when the number of longitudinal pipes is large, the lower pipes are filled with more liquid, so that the heat transfer area cannot be fully utilized. In addition, the compactness is poor, cleaning is difficult, and a large number of connecting elbows are required. Therefore, such condensers have been rarely used in ammonia refrigeration plants.
(2) Evaporative condenser
The heat exchange of the evaporative condenser is mainly carried out by evaporating the cooling water in the air and absorbing the latent heat of gasification. According to the air flow mode, it can be divided into suction type and pressure delivery type. In this type of condenser, the cooling effect generated by the evaporation of the refrigerant in another refrigeration system is used to cool the refrigerant vapor on the other side of the heat transfer partition, and promote the condensation and liquefaction of the latter. Evaporative condenser is composed of cooling pipe group, water supply equipment, fan, water baffle and box body. The cooling pipe group is a serpentine coil group made of seamless steel pipes, and is housed in a rectangular box made of thin steel plates.
There are ventilators on both sides or the top of the box, and the bottom of the box doubles as a cooling water circulation pool. When the evaporative condenser works, the refrigerant vapor enters the serpentine tube group from the upper part, condenses and releases heat in the tube, and flows into the liquid receiver from the lower liquid outlet tube. The cooling water is sent to the water sprayer by the circulating water pump, sprayed from the surface of the steering wheel pipe group directly above the serpentine coil group, and evaporates by absorbing the condensed heat in the pipe through the pipe wall. A fan located on the side or top of the box forces air to sweep over the coil from bottom to top, promoting the evaporation of water and taking away the evaporated moisture.
Among them, the fan is installed on the top of the box, and when the serpentine tube group is located on the suction side of the fan, it is called a suction evaporative condenser, while the fan is installed on both sides of the box, and the serpentine tube group is located on the outlet side of the fan. With the evaporative condenser, the suction air can pass through the serpentine tube group evenly, so the heat transfer effect is good, but the fan is prone to failure when running under high temperature and high humidity conditions. Although the air through the serpentine tube group is not uniform in the pressure feeding type, the working conditions of the fan motor are good.
Features of Evaporative Condenser:
1. Compared with the water-cooled condenser with DC water supply, it can save about 95% of water. However, the water consumption is similar when compared to the combination of a water-cooled condenser and a cooling tower.
2. Compared with the combined system of water-cooled condenser and cooling tower, the condensation temperature of the two is similar, but the evaporative condenser has a compact structure. Compared with air-cooled or direct-flow water-cooled condensers, its size is relatively large.
3. Compared with the air-cooled condenser, its condensing temperature is lower. Especially in dry areas. When operating throughout the year, it can be air-cooled in winter. Compared with the water-cooled condenser with direct water supply, its condensing temperature is higher.
4. The condensing coil is easy to corrode, and it is easy to scale outside the tube, and it is difficult to maintain.
In summary, the main advantages of evaporative condensers are that the water consumption is small, but the circulating water temperature is high, the condensation pressure is large, it is difficult to clean the scale, and the water quality is strict. It is especially suitable for dry and water-deficient areas. It should be installed in a place with open air ventilation, or installed on the roof, not indoors.
(3) Air-cooled condenser
The air-cooled condenser uses air as the cooling medium, and the temperature rise of the air takes away the heat of condensation. This type of condenser is suitable for occasions where there is extreme water shortage or no water supply, and is commonly used in small Freon refrigeration units. In this type of condenser, the heat given off by the refrigerant is carried away by the air. The air can be natural convection or forced flow by means of a fan. This type of condenser is used for Freon refrigeration equipment in places where water supply is inconvenient or difficult.
(4) Water shower condenser
It is mainly composed of heat exchange coil, water spray tank and so on. The refrigerant vapor enters from the steam inlet at the lower part of the heat exchange coil, and the cooling water flows from the gap of the water spray tank to the top of the heat exchange coil, and flows downward in a film shape. The water absorbs the heat of condensation. Under the natural convection of the air, Due to the evaporation of water, part of the condensation heat is taken away. The heated cooling water flows into the pool, and is then cooled by the cooling tower for recycling, or part of the water is drained, and part of the fresh water is replenished and sent to the shower tank. The condensed liquid refrigerant flows into the accumulator. The water spray condenser is the temperature rise of water and the evaporation of water in the air to take away the heat of condensation. This condenser is mainly used in large and medium ammonia refrigeration systems. It can be installed in the open air or below the cooling tower, but it should be kept out of direct sunlight. The main advantages of the sprinkler condenser are:
1. Simple structure and convenient manufacture.
2. It is easy to find out the ammonia leakage and easy to maintain.
3. Easy to clean.
4. Low requirements for water quality.
weakness is:
1. Low heat transfer coefficient
2. High metal consumption
3. Large area