High-low temperature hot and humid test chamber Water-cooled condenser Introduction Role: The condenser is a heat exchanger for the refrigerant to heat outward, its role is to make the compressor discharge high-pressure and high-temperature refrigerant Xenon lamp liquefaction, into a high-pressure liquid refrigerant. The amount of heat released by the refrigerant in the condenser contains some: the amount of heat drawn from the object being cooled by the transpiration apparatus; and the amount of heat converted by the external mechanical work when compressed in the compressor.
Variety: According to the cooling medium and cooling method:
â–² water-cooled condenser: vertical shell, horizontal shell, sleeve type;
â–² air-cooled;
â–² water air cooling: such as transpiration, water type;
â–² Refrigerant transpiration or other technical media cooling.
The equipment that uses water as the cooling medium to condense the high-temperature and high-pressure gas refrigerant is called a water-cooled condenser. Because the water temperature in nature is usually relatively low, the condensing temperature of the water-cooled condenser is relatively low, which is beneficial to both the refrigeration capacity and the operating economy of the compressor. Most water-cooled condensers are now used in refrigeration equipment. In the meantime, the cooling water can flow once and can also be recycled. When circulating water is used, a cooling tower or a cooling pool needs to be built so that the water leaving the condenser is cooled again.
Commonly used water-cooled condensers have the type of shell and tube, vertical shell and tube and other types.
1. Horizontal shell-and-tube condenser â—† The main part of the structure and operation principle are as shown in the figure. Its shell is a cylindrical cylinder welded and rolled into steel plates. Two circular tube plates are welded on two ends of the cylinder. The two tube plates drill holes with many orientations corresponding to each other. A tube is inserted into the hole, and the two ends of the tube are press-fitted into the tube hole of the tube plate by expansion or welding. This constitutes a group of straight tube controls.
The horizontal shell-and-tube condenser is placed horizontally and its structure is shown in the figure. The xenon lamp of the refrigerant condenses on the outer surface of the tube, and the cooling water moves in the tube under the action of the pump. The xenon lamp of the refrigerant enters the cylinder from the upper part (intake pipe), and is condensed into a liquid and flows into the accumulator from the discharge pipe at the lower part of the cylinder. During normal operation, only a small amount of liquid remains in the lower part of the barrel.
However, with regard to the small-scale refrigeration equipment, in order to simplify the equipment, a separate liquid reservoir may not be provided, and the lower part of the condenser cylinder must have a necessary liquid storage function, and a few rows of tubes can be installed. The discharge pipe of the condenser is connected to the lower part of the cartridge. With regard to the ammonia condenser, a dirt collecting bag is also welded under the cylinder to collect lubricant and mechanical impurities.
Both ends of the horizontal tube and shell condenser are sealed with two end caps. There is a water separator in the end cap. The separation of the two end caps cooperates with each other, completing the multiple-pipe movement of the cooling water. The number of tubes in the condenser is usually even, so the inlet and outlet of the cooling water are arranged on the same end cap, and the cooling water flows in from below and flows out. The air-discharging plug on the upper part of the end cap is used to sweep the air in the tube when the first end is filled with water, and the lower water-discharging cock is used to sweep out the water in the condenser when it stops to prevent the tube from being corroded or cracked.
â—† Excellent defects:
Advantages: Compact structure, high heat transfer coefficient K, low cooling water consumption, convenient operation, wide application, suitable for large, medium and small-sized ammonia and freon refrigeration equipment; small Freon compressor and condenser usually do As a compression condensing unit, the equipment is convenient and the floor space is small.
Defects: High water quality requirements, low water temperature, large resistance to cooling water activity, inconvenient cleaning scale, and shutdown operations.
2. Vertical shell-and-tube condenser â—† Construction and operation principle This condenser upright equipment is only used for large and medium-sized ammonia refrigeration equipment. Its structure is shown in the figure. Compared with the horizontal type, the vertical type is not only an upright device, but also has no end caps on both sides. The water and ammonia methods are also different.
The ammonia deuterium lamp enters the outside space of the cylinder from the upper side of the condenser shell, the condensed liquid flows down the tube wall from the top, and accumulates at the bottom of the condenser and flows into the reservoir via the discharge tube. The cooling water enters into the condenser tube from the upper part, but the water does not overflow the entire section of the steel tube, but flows down the inner wall of the tube in the form of a film and is discharged into the pool below the condenser. Usually, the water is pumped to the cooling tower for recycling. .
In order to evenly distribute the cooling water into each steel pipe, the top of the condenser is equipped with a water distribution tank. Each pipe has a diversion nozzle with a water separation function on the pipe mouth, as shown in the figure. The cooling water flows into the pipe through the chute on the nozzle of the diversion pipe, and flows down spirally along the inner wall of the pipe. In this way, a layer of water film can be formed on the inner wall of the tube, which absorbs the heat of the refrigerant abundantly, which not only improves the cooling effect of the condenser but also saves water.
Similar to the horizontal condenser, there are pipeline connectors such as inlet, outlet, air release, pressure equalization, oil discharge, and safety valve on the vertical housing, which are connected with the corresponding piping and equipment.
Excellent defect superiority: high heat transfer coefficient K (but less than horizontal); straight equipment, small footprint; no risk of freezing, equipment can be outdoors, does not occupy indoor space; not very high on water quality, easy to descaling , can clean the water pipe in operation.
Lack: large amount of cooling water; large volume, relatively heavy and stupid; low water velocity in the condenser tube, easy to scale, open sand equipment, easy to fall into the lime sand, the demand is often clean.
3. The tube condenser is mainly used in small Freon air conditioning units, and the single unit cooling capacity is usually less than 25 kW.
◆Structural and Operational Principles Condenser tube condensers are constructed of two tubes of different diameters. The outer tubes are mostly φ50 mm seamless steel tubes with one or more steel tubes or low-ribbed steel tubes (called inner tubes). ). After nesting, it is wound into a spiral shape on the bender.
The refrigerant neon lamp enters the space of the outer tube from the upper part, condenses on the outer surface of the inner tube, and the condensed liquid flows out from the lower part. The cooling water enters the inner tube from the lower part and flows out of the upper part after absorbing heat. In this way, it is counter-current to the refrigerant and the asymmetrical counter-current heat exchange is completed, so the heat transfer coefficient K is high.
â—† Excellent defects:
Excellent: counter-current heat exchange, good heat transfer, high K; simple structure, easy production, can be placed around the compressor, does not occupy a special orientation, saving the area of ​​the compressor condensing unit.
Lack: The condensed liquid exists in the lower part of the tube, so that the heat transfer surface is not fully utilized; the metal consumption of the unit heat transfer area is large; the cleaning scale is difficult.
4. Development trend of shell-and-tube condenser (enhance heat transfer method)
(1) Change in aspect ratio: usually L/D = 6 to 9;
(2) The new condensing pipe is used to strengthen the heat-generating finned pipe around the wire, and the d=1.5mm steel wire is wrapped around the Φ16×1.5 steel pipe, and the heat transfer coefficient is 60 to 100% higher than that of the light pipe. The outer edges of the fins have sawtooth-shaped notches, F↑, and liquid film ↓. In the case of Φk and the same amount of water, save 50% of copper tubes and reduce the volume by 1/3.
4 Condenser and transpiration Xenon lamps The compression refrigeration cycle has four thermal processes and it is therefore essential that there are four thermal devices.
Compression - through the compressor;
· Exothermic (condensing) - through the condenser;
· Save - After expansion valve;
· Heat absorption (cooling) - through the transpiration apparatus;
The condenser and transpiration equipment are heat exchange equipment. Refrigeration cycle heat transfer equipment features:
(1) The scale of operating pressure and temperature change is relatively narrow. Such as frozen room t0=-23～-30°C, cooling room t0=0～-2°C
(2) Small heat transfer temperature difference. Such as: condenser, water cooling Δt = 5 ~ 7 °C; air cooling Δt = 10 ~ 15 °C. The temperature difference is small, the warm current density is low, the heat transfer coefficient is small, and the device volume component is ↑. If Δt is advanced, irreversible loss of ↑, s↑ causes the whole machine to run uneconomically.
(3) Heat exchanger and refrigeration compressor match. Compressor discharge heat = condenser heat exchange, when the condenser F is hel
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