As a kind of plate heat exchanger, plate condenser is specially designed for condensing condition. When the condensing capacity is small and the temperature is high,
we can use the ordinary plate as the condenser. But in many condensing conditions, especially when the flow is large and the temperature is low, the plate condenser specially designed for the condensing condition will bring incomparable advantages.
The common plate heat exchanger is generally designed for liquid-liquid heat transfer condition, which is liquid on both sides. Its plate structure generally adopts herringbone corrugated design. Figure 1 shows the gj-a-m series plate type of our company, which is a general plate heat exchanger with wide application range and high heat transfer efficiency. By analyzing its layout structure, it is easy to see that the corrugated is herringbone corrugated and adopts uniform size corner hole design.
The special condenser is generally optimized for the steam-liquid condition, that is, the hot fluid is steam with large volume flow, and the cold fluid is circulating cooling water (or other cooling medium, generally liquid). Figure 2 shows our gj-l series plate type, which is a special plate condenser specially designed for condensing condition. It adopts concave convex corrugated design and special corner hole design.
Figure 1: gj-a-m series plate heat exchanger Figure 2: gj-l series plate condenser
Through the comparative analysis of two types of plate corrugated, channel, corner hole and other characteristics, the results are as follows:
1: Ripple. The common plate heat exchanger is generally designed with herringbone ripple, the main purpose of which is to make the fluid turbulent and enhance heat transfer. Different corrugation angles are used to balance heat transfer and resistance loss. The plate condenser adopts a special corrugated design. The corrugated on the steam side mainly supports the flow channel, while the corrugated on the cooling water side enhances the heat transfer.
2: Flow channel. The common plate heat exchanger generally adopts the design of 2-4mm plate spacing, which can be designed as shallow dense corrugation, so as to obtain higher turbulence and enhance heat transfer. The plate condenser adopts wide and narrow channel design, with large and straight steam wide channel, small and tortuous cooling water narrow channel, which greatly improves the steam water heat transfer capacity.
3. Corner hole. The corner holes of common plates are usually the same size, which is also in line with the characteristics of liquid-liquid heat transfer on both sides; Different from plate condenser, the special feature of plate condenser is that the steam inlet is very large. This is because the volume of general condensing steam is very large, which is more than ten or even dozens of times that of cooling fluid, and the volume of condensate is sharply reduced, so the condensate interface can be designed smaller. The plate condenser adopts the optimized design of steam inlet and condensate outlet, which can meet the needs of a large number of steam condensation, even a large number of low-temperature steam condensation.
Through simple comparison, we can answer the question whether plate heat exchanger can be used as plate condenser. The answer is: small condensing capacity and small volume can be used, but with large flow and gross volume, we recommend that special plate condenser be preferred.
Due to the late development of plate condenser in China, many domestic manufacturers use ordinary plate heat exchanger instead of plate condenser, and the effect is also good. Of course, the effect of this refers to the comparison with the tube condenser, not with the professional plate condenser. Therefore, many people mistakenly believe that the ordinary plate condenser can completely replace the plate condenser. In fact, ordinary plate heat exchanger as
condenser has some limitations, the specific reasons are as follows:
1: Ordinary plate heat exchanger usually has four corner holes of the same size. Because the density difference between gas and liquid is huge, considering that the steam flow rate can not be too fast under the same mass flow rate, we need a particularly large inlet. We can imagine that a common plate heat exchanger with four corner holes of DN500 will be a very huge plate, which not only increases the manufacturing difficulty, but also leads to a waste of resources, because the four corner holes are particularly large, But the space they occupy is not involved in the heat transfer. Therefore, when the steam flow rate is relatively large, it is difficult to find the plate with large plate area and corner hole. At this time, ordinary plate heat exchanger can not replace plate evaporator.
2: In the process of condensation, we always want the pressure drop of condensed steam to be as small as possible, because if the steam pressure becomes smaller, the corresponding condensation temperature will also become smaller. At this time, the temperature difference between hot and cold fluids will become smaller, and the required heat exchange area will increase. Cause unnecessary waste. Due to the small corner hole of ordinary plate heat exchanger, the steam inlet velocity is too fast and the pressure drop increases. The steam pressure decreases and the area increases.
3: The corrugated form of plate condenser is different from that of ordinary plate heat exchanger. Herringbone corrugated is mainly used to enhance turbulence and heat transfer. Concave convex corrugated is mainly used to support, which is to quickly discharge condensate and reduce the thickness of liquid film, so as to reduce thermal resistance and enhance heat transfer. In addition, the distance between the condensing side of the plate condenser and the circulating water measuring plate is not the same. This design can make the steam flow wider, reduce the flow rate, and reduce the pressure drop. The circulating water flow narrower, so as to increase the flow rate and strengthen the heat transfer.
To sum up, ordinary plate heat exchanger can be used as plate condenser, but due to the limitation of condensing steam flow, the flow difference is too large, and the pressure drop will be higher than plate condenser. Therefore, when choosing plate condenser and ordinary plate heat exchanger, plate condenser should be the first choice. If limited by conditions, ordinary plate heat exchanger can be used temporarily.
