Spiral plate heat exchanger is a new type of heat exchanger, which is composed of two parallel thin steel plates welded on a partition plate (central partition) and rolled into a pair of spiral flow channels that are separated from each other. A distance column is welded between the two plates to maintain the distance between the flow channels and also enhance the stiffness of the spiral plate. The two ends of the spiral plate are welded with cover plates, and the two end surfaces and the spiral plate are equipped with inlet and outlet connections for cold and hot fluids. Cold and hot fluids flow in two spiral channels respectively, exchanging heat through spiral plates.

The diameter of a spiral plate heat exchanger is generally within 1.6m, the plate width is 200-1200mm, the extreme thickness is 2-4mm, and the distance between the two plates is 5-25mm. Commonly used materials are carbon steel or stainless steel. The main advantage of spiral plate heat exchangers is their compact structure, which provides a large heat transfer area per unit volume (approximately three times that of tubular heat exchangers); The fluid is allowed to have a high flow velocity (up to 2m/s for liquids and 20m/s for gases), a high degree of turbulence, and a high heat transfer coefficient (about 1-2 times that of a tube heat exchanger); Can achieve pure countercurrent operation; Not easy to scale and block. Its main disadvantages are that the operating pressure and temperature should not be too high, the fluid flow resistance is high, it is difficult to maintain, and it requires high welding quality. Therefore, the general operating pressure is below 2Okgf/cm2, and the temperature is below 300-400 ℃.

A plate heat exchanger is assembled by a set of rectangular metal thin plates arranged in parallel, with adjacent plates lined with gaskets and clamped with a frame. There are circular holes at the four corners of the plate, forming fluid channels. Cold and hot fluids flow through the same plate on both sides and exchange heat through the plate. Assemble the flow for it. The thickness of the board is 0.5-3mm, usually pressed into various corrugated shapes.

The main characteristics of plate heat exchangers are compact structure and large heat transfer area per unit volume of equipment, about 250-1000m2/m3, while tube heat exchangers only have 40-150m2/m3; High heat transfer coefficient, for low viscosity liquids, the heat transfer coefficient can reach 1500-4700W/(m2. ℃), with a maximum of 7000W/(m2. ℃). The operation is flexible and adaptable, and the number of plates can be adjusted according to the needs to adjust the heat transfer area. It is easy to process and manufacture, easy to maintain and clean, and has less heat loss. Its main disadvantage is that due to the limitations of plate stiffness, gasket types, and groove structures, the allowable operating pressure is relatively low; Due to the limitation of gasket material, the operating temperature cannot be too high. For synthetic rubber gaskets, the operating temperature should not exceed 130 ℃, and for compressed asbestos gaskets, it should also be below 250 ℃; Due to the small spacing between the plates and the small cross-sectional area of the flow channel, the flow rate cannot be too high, resulting in a small processing capacity, making it difficult to seal, prone to leakage, and prone to blockage.

The performance of a spiral plate heat exchanger is similar to that of a plate heat exchanger. But it also has its unique features, and its main advantages are:

1. High heat transfer efficiency. The centrifugal force of the helical flow of the medium inside the spiral plate heat exchanger can enhance turbulence. According to experiments, turbulence can be formed when Re=1400-1800, and the flow velocity can be increased due to the smaller flow resistance compared to the shell and tube type. As a result, the heat transfer coefficient K can be increased by 2.5 times. In addition, the average temperature difference of heat transfer in the fully counter current spiral plate heat exchanger is the largest, which helps to improve heat transfer efficiency.

2. Compact structure, no need for pipes. Due to the large area of the heat transfer surface of the plate type, the heat transfer surface per unit volume can reach 44-100m2/m3, which is about 2-3 times that of the shell and tube heat exchanger. In addition, the heat transfer coefficient and average temperature difference are both large, which inevitably leads to a compact and lightweight structure.

3. Not easily clogged with dirt. Due to the single channel, high flow rate, and difficulty in sedimentation of dirt, once sedimentation occurs, the cross-sectional area of the channel decreases and the flow rate increases, thereby enhancing the flushing effect on the fouling material. This "self-cleaning" effect is not present in shell and tube heat exchangers. According to statistics, the rate of fouling of the spiral plate is only one tenth of that of the shell and tube type.

4. Can effectively utilize low-temperature heat sources and precisely control temperature. By opening a double spiral flow channel, reverse heat transfer can be more completely formed and the flow channel is longer, which helps to reduce the allowable (between two media) for continuous and uniform heat transfer or temperature rise and fall in heat exchanger design. Sources (such as underground heat sources) or precise control of medium temperature provide favorable conditions, and empirical data shows that the medium temperature difference between plate and spiral plate heat exchangers is the lowest. 5. The flow resistance is relatively small. Experiments have shown that compared to shell and tube heat exchangers under the same conditions, the flow resistance of spiral plate heat exchangers is smaller.