Condenser type and characteristics
Condensers can be divided into four categories: water-cooled, evaporative, air-cooled and water-drenched condensers according to their different cooling media.
(1) water-cooled condenser
Water-cooled condenser uses water as cooling medium, and the temperature rise of water takes away the condensing heat. Cooling water is generally recycled, but the system needs to be equipped with a cooling tower or cooling pool. Water cooling condenser can be divided into vertical shell and tube type, horizontal shell and tube type water cooling condenser can be divided into vertical shell and tube type, horizontal shell and tube type and casing type according to its different structure type, the common shell and tube 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 system at present. Vertical condenser is mainly composed of shell (cylinder), tube plate and tube bundle.
The refrigerant steam enters the gap between the pipe beams from the steam inlet at 2/3 of the height of the cylinder. The cooling water in the pipe and the high temperature refrigerant steam outside the pipe exchange heat through the pipe wall, so that the refrigerant steam is condensed into liquid and gradually flows down to the bottom of the condenser, and flows into the liquid storage device through the liquid outlet pipe. After absorbing heat, the water is discharged into the lower concrete pool, and then sent to the cooling water tower by water pump after cooling and recycling.
In order to make the cooling water evenly distributed to each pipe mouth, the water distribution tank at the top of the condenser is provided with a leveling plate and a diversion with a chaining groove is provided at each pipe mouth at the upper part of the pipe, so that the cooling water flows down the inner wall of the pipe with a film water layer, which can not only improve the heat transfer effect but also save water. In addition, the shell of the vertical condenser is also provided with pipe joints such as pressure equalization pipe, pressure gauge, safety valve and air discharge pipe, so as to connect with the corresponding pipelines and equipment.
The main characteristics of vertical condenser are:
1. Due to the large cooling flow rate 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 directly and the flow rate is large, 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 ~ 4℃, and the logarithmic average temperature difference is generally about 5 ~ 6℃, the water consumption is large. And because the equipment is placed in the air, the pipe is easy to corrosion, leakage is easier to be found.
2. Horizontal shell and tube condenser
Horizontal condenser and vertical condenser have similar shell structure, but there are many differences in general, the main difference lies in the horizontal placement of the shell and the multi-channel flow of water. The tube plates at both ends of the horizontal condenser are closed with a end cover, and the end cover is cast with a designed and coordinated water separator, which divides the whole tube bundle into several tube groups. In this way, the cooling water enters from the lower part of the end cover, flows through each tube group in sequence, and finally flows out from the upper part of the same end cover, it takes 4 ~ 10 return trips. In this way, the flow rate of the cooling water in the tube can be increased, so as to improve the heat transfer coefficient, and the high temperature refrigerant vapor from the upper part of the shell into the pipe bundle and the cooling water in the tube for sufficient heat exchange.
The condensed liquid flows into the storage cylinder from the lower outlet pipe. On the other end of the condenser end cover is also a permanent exhaust valve and water cock. The exhaust valve is in the upper part and opens when the condenser is put into operation to discharge the air in the cooling pipe and make the cooling water flow smoothly. Remember not to confuse with the exhaust valve to avoid accidents. Drain all the water stored in the cooling water pipe when the condenser is stopped, so as to avoid freezing and cracking the condenser due to water freezing in winter. The shell of the horizontal condenser also has a number of pipe joints connected with other equipment in the system, such as air intake, liquid outlet, pressure pipe, air discharge pipe, safety valve, pressure gauge joint and oil discharge pipe.
Horizontal condensers are not only widely used in ammonia refrigeration systems, but can also be used in Freon refrigeration systems, but their structure is slightly different. The cooling tube of ammonia horizontal condenser adopts smooth seamless steel pipe, while the cooling tube of Freon horizontal condenser generally adopts low rib copper pipe. This is due to the low heat release coefficient of Freon. It is worth noting that some Freon refrigeration units are generally not equipped with liquid storage cylinder, but only use a few rows of pipes at the bottom of the condenser, which are also used as liquid storage cylinder.
Horizontal and vertical condensers, in addition to the location and water distribution are different, the temperature rise of water and water consumption are also different. The cooling water of the vertical condensor is * gravity flowing down the inner wall of the tube, which can only be a single stroke, so to obtain a large enough heat transfer coefficient K, it is necessary to use a large amount of water. The horizontal condenser uses a pump to pressure the cooling water into the cooling pipe, so it can be made into a multi-stroke condenser, and the cooling water can get a large enough flow rate and temperature rise (Δt=4 ~ 6℃). So the horizontal condenser can obtain a sufficiently large K value with a small amount of cooling water.
