The refrigerated air dryer is a compressed air dryer equipment that uses physical principles to freeze the moisture in the compressed air below the dew point, condensing it into liquid water from the compressed air and discharging it. Limited by the freezing point of water, theoretically its dew point temperature can be close to 0 degrees. In practice, the dew point temperature of a good freeze dryer can reach within 10 degrees.
According to the difference between the heat exchangers of refrigerated air dryers, there are currently two types of air dryers with tube-fin heat exchangers and plate-type heat exchangers (referred to as plate exchanges) on the market. Due to its mature technology, compact structure, high thermal efficiency, and no secondary pollution, the heater air dryer has become the mainstream of the air dryer market. However, there are many disadvantages in the design and use of the old tube-fin heat exchanger. The main performance in the following aspects:
1. Huge volume:
The tube-fin heat exchanger generally has a horizontal cylindrical structure. In order to adapt to the shape of the heat exchanger, the whole design of the refrigerating and drying machine can only follow the heat exchanger mechanism. Therefore, the whole machine is bulky, but the internal space is relatively empty. , Especially for medium and large equipment, 2/3 of the space inside the whole machine is surplus, thus causing unnecessary space waste.
2. Single structure:
The tube-fin heat exchanger generally adopts a one-to-one design, that is, the corresponding processing capacity air dryer corresponds to the corresponding processing capacity heat exchanger, which results in limitations in the production process and cannot be flexibly used in combination. Ways to use the same heat exchanger to form air dryers with different processing capacities, which will inevitably lead to an increase in raw material inventory.
3. Average heat exchange efficiency
The heat transfer efficiency of the tube-fin heat exchanger is generally about 85%, so it is necessary to achieve an ideal heat transfer effect.The design of the entire refrigeration system must increase by more than 15% on the basis of calculating the required refrigeration capacity, thus increasing the system cost and power consumption.
4. Air bubbles in tube-fin heat exchanger
The square fin structure and circular shell of the tube-fin heat exchanger leave non-heat exchange space in each channel, causing air bubbling. The baffles of the evaporator allow some of the compressed air to escape without heat exchange. This limits the dew point of the product gas, and increasing the cooling capacity does not completely solve the problem. Therefore, the pressure dew point of the tube-fin freeze dryer is generally above 10°C, which cannot reach the optimal 2°C.
5. Poor corrosion resistance
Tube-fin heat exchangers are generally made of copper tubes and aluminum fins, and the target medium is ordinary compressed gas and non-corrosive gas. When applied to some special occasions, such as marine refrigeration dryers, special gas cooling and drying Machines, etc., are prone to corrosion, which greatly shortens the service life, or even cannot be used at all.
In view of the characteristics of the above-mentioned tube-fin heat exchanger, the plate heat exchanger can make up for these shortcomings. The specific description is as follows:
1. Compact structure and small size
The plate heat exchanger has a square structure and occupies a small space. It can be flexibly combined with refrigeration components in the equipment without excessive space waste.
2. The model is flexible and changeable
The plate heat exchanger can be assembled in a modular fashion, that is, it can be combined into the required processing capacity in a 1+1=2 manner, which makes the design of the whole machine flexible and changeable, and can more effectively control the raw material inventory.
3. High heat exchange efficiency
The flow channel of the plate heat exchanger is small, the plate fins are waveforms, and the cross-section changes are complicated. A small plate can obtain a larger heat exchange area, and the flow direction and flow rate of the fluid are constantly changed, which increases the flow rate of the fluid. Disturbance, so it can reach turbulent flow at a very small flow rate. In the shell-and-tube heat exchanger, the two fluids flow in the tube side and the shell side respectively. Generally, the flow is cross-flow, and the logarithmic average temperature difference correction coefficient is small. , And plate heat exchangers are mostly co-current or counter-current flow, and the correction coefficient is usually about 0.95. In addition, the flow of cold and hot fluid in the plate heat exchanger is parallel to the heat exchange surface without bypass flow, making the plate heat exchanger The temperature difference at the end of the heat exchanger is small, which can be lower than 1°C. Therefore, the pressure dew point of a refrigeration dryer using a plate heat exchanger can be as low as 2°C
4. There is no dead angle of heat exchange, basically achieving 100% heat exchange
Due to its unique mechanism, the plate heat exchanger makes the heat exchange medium fully contact the plate surface without heat exchange dead angles, no drain holes, and no air leakage. Therefore, compressed air can achieve 100% heat exchange. Ensure the stability of the dew point of the finished product.
5. Good corrosion resistance
The plate heat exchanger is made of aluminum alloy or stainless steel structure, which has good corrosion resistance and can also avoid secondary pollution of compressed air. Therefore, it can be adapted to various special occasions, including marine ships, with corrosive gases The chemical industry, as well as the more stringent food and pharmaceutical industries.
Combining the above characteristics, the plate heat exchanger has the insurmountable advantages of the tube and fin heat exchanger. Compared with the tube and fin heat exchanger, the plate heat exchanger can save 30% under the same processing capacity. Therefore, the configuration of the refrigeration system of the whole machine can be reduced by 30%, and the energy consumption can also be reduced by more than 30%. The volume of the whole machine can also be reduced by more than 30%.
The latest frequency conversion plate-change refrigerated air dryer display
Post time: May-15-2023
