The Role and Advantages of Plate Heat Exchangers in Heat Exchange Stations of Hydropower Stations

As a clean and renewable energy source, hydropower plays an irreplaceable role in the global energy structure, contributing significantly to energy conservation, emission reduction and sustainable development. The heat exchange station is a key supporting facility of hydropower stations, responsible for regulating the temperature of various working media (such as cooling water, lubricating oil, and electrolyte) in the power generation process, ensuring the safe, stable and efficient operation of hydropower units. Plate Heat Exchangers (PHEs), with their unique structural design and excellent heat transfer performance, have gradually replaced traditional heat exchange equipment such as shell-and-tube heat exchangers and become the core equipment in heat exchange stations of hydropower stations. Compared with traditional heat exchangers, plate heat exchangers have obvious advantages in heat transfer efficiency, space utilization, maintenance convenience and corrosion resistance, which can perfectly match the complex working conditions and diverse heat exchange needs of hydropower stations. This article will systematically elaborate on the specific roles and core advantages of plate heat exchangers in heat exchange stations of hydropower stations, combining practical application scenarios, to provide a comprehensive reference for relevant engineering and technical personnel.

The heat exchange station of a hydropower station undertakes the important task of heat exchange and temperature control for key equipment and working media in the power generation process, involving links such as unit cooling, lubrication system temperature control, waste heat recovery and auxiliary system temperature regulation. Plate heat exchangers, with their high heat transfer efficiency and flexible application capabilities, are deeply integrated into various links of the heat exchange station, effectively solving key technical problems such as low heat exchange efficiency, difficult temperature control and high energy consumption in traditional heat exchange systems. Their specific roles can be divided into the following aspects:

Hydropower units (including water turbines, generators, etc.) will generate a lot of heat during operation. If the heat cannot be dissipated in time, it will lead to overheating of the unit, aging of insulation materials, reduction of operational efficiency, and even serious failures such as unit shutdown, which will affect the continuity and safety of power generation. The heat exchange station uses plate heat exchangers as the core cooling equipment to realize efficient heat exchange between the cooling medium and the hydropower unit, ensuring that the unit operates within the safe temperature range.

In the generator cooling system, for example, the stator and rotor of the generator will generate a lot of heat due to electromagnetic induction and friction during operation. The plate heat exchanger can quickly exchange heat between the cooling water (or cooling oil) and the generator, reducing the temperature of the generator to the safe operating range (usually 60-75℃). Especially in large hydropower stations such as Baihetan Hydropower Station, the closed cooling tower and plate heat exchanger composite system is used to control the temperature of the generator winding below 65℃, ensuring the full-load operation of the million-kilowatt unit. For water turbines, plate heat exchangers are used to cool the bearing bush and casing of the water turbine, avoiding bearing wear and casing deformation caused by overheating, and extending the service life of the water turbine.

In addition, plate heat exchangers are also used in the cooling of transformers in hydropower stations. The windings and iron cores of transformers will generate heat during operation, which will cause the temperature of transformer oil to rise. If the temperature is too high, it will lead to the aging of insulating oil and the decrease of dielectric strength. Plate heat exchangers can effectively cool the transformer oil, control its temperature within the specified range, and ensure the safe and stable operation of the transformer. For hydropower stations in coastal or corrosive water environments, plate heat exchangers made of titanium alloy plates can be selected to resist the corrosion of seawater or corrosive water, ensuring long-term stable operation of the cooling system.

Hydropower stations are equipped with a large number of lubrication systems and hydraulic systems, such as the lubrication system of water turbines, the hydraulic system of gates and the lubrication system of air compressors. The operating temperature of the working oil (lubricating oil and hydraulic oil) directly affects the performance and service life of the system. If the oil temperature is too high, it will lead to the deterioration of the oil quality, reduce the lubrication and sealing performance, and even cause equipment failures such as component wear and oil leakage.

Plate heat exchangers (commonly shell-and-plate type) are widely used in the temperature control of lubrication and hydraulic systems in heat exchange stations. They can efficiently exchange heat between the working oil and the cooling medium, reducing the oil temperature to the normal operating range (usually 40-55℃), maintaining the performance of the oil, and preventing equipment failures caused by overheating. For example, in the thrust bearing system of hydropower units, the oil temperature exceeding 60℃ will cause failures. Plate heat exchangers can accurately control the oil temperature to about 45℃, extending the service life of the bearing by 2-3 times. The lubricating oil of air compressors in hydropower stations exchanges heat through plate heat exchangers. The cooled lubricating oil returns to the air compressor for work, while the heated water enters the hot water storage tank for reuse, realizing the dual effects of equipment protection and energy saving.

In the operation process of hydropower stations, a large amount of waste heat will be generated, such as the waste heat of cooling water after unit cooling, the waste heat of lubricating oil, and the waste heat of industrial wastewater. If these waste heats are directly discharged, it will not only cause energy waste but also increase environmental pressure. The plate heat exchanger in the heat exchange station has excellent waste heat recovery capabilities, which can effectively recover the residual heat in these waste media and reuse it in the production and living of the hydropower station, thereby improving the comprehensive utilization rate of energy and reducing energy consumption.

For example, the high-temperature cooling water after cooling the hydropower unit and transformer can recover heat through plate heat exchangers, and the recovered heat can be used to preheat the domestic hot water in the hydropower station, heat the workshop and office area, or preheat the makeup water of the boiler, which not only reduces the energy consumption of electric heating or boiler heating but also saves energy costs. In some large hydropower stations, such as the Three Gorges Hydropower Station, after adopting plate heat exchangers for waste heat recovery, the annual power saving of a single unit exceeds 200,000 kWh. In addition, the waste heat of the hydraulic system and lubrication system can also be recovered through plate heat exchangers, and the recovered heat can be reused in the temperature regulation of the system, forming an energy-saving cycle.

The heat exchange station of a hydropower station also needs to provide temperature regulation services for various auxiliary systems, such as the circulating water system, the water treatment system, and the fire-fighting water system. Plate heat exchangers, with their flexible temperature regulation capabilities, can meet the different temperature requirements of various auxiliary systems, ensuring the normal operation of supporting facilities.

In the water treatment system, for example, the water quality treatment process (such as filtration, disinfection) needs to be carried out at a specific temperature. Plate heat exchangers can accurately adjust the temperature of the treated water to ensure the effect of water quality treatment and avoid the impact of temperature changes on water treatment efficiency. In the circulating water system, plate heat exchangers can adjust the temperature of the circulating water to maintain the stability of the system, prevent the circulating water from freezing in winter or overheating in summer, and avoid pipeline blockage or corrosion. For hydropower stations in northern regions, plate heat exchangers can also be used to heat the输水 pipeline, preventing ice blockage and ensuring the normal operation of the water supply system. In addition, plate heat exchangers are also used in the temperature regulation of the fire-fighting water system, ensuring that the fire-fighting water is in a suitable temperature range and improving the reliability of fire fighting.

In recent years, with the increasing emphasis on ecological protection, hydropower stations have higher and higher requirements for ecological environment protection. When the hydropower station releases ecological flow, the deep low-temperature water may affect the survival of aquatic organisms in the downstream. The plate heat exchanger in the heat exchange station can be used to adjust the temperature of the ecological flow, mixing surface and deep water to raise the water temperature to the range suitable for aquatic organisms (such as 12-18℃ for fish spawning), thereby protecting the downstream ecological chain. This application has been successfully implemented in some hydropower stations in Fujian, effectively restoring the downstream ecological environment.

Compared with traditional heat exchange equipment such as shell-and-tube heat exchangers, plate heat exchangers have obvious advantages in structure, performance and operation, which make them highly adaptable to the complex working environment of hydropower station heat exchange stations (such as high temperature, high humidity, corrosive media, and variable load operation) and diverse heat exchange needs. The specific advantages are as follows:

The core advantage of plate heat exchangers is their high heat transfer efficiency. The plate surface is designed with special corrugations, which can strongly disturb the fluid when the fluid flows through the plate, breaking the laminar boundary layer of the fluid, increasing the heat transfer coefficient, and thus significantly improving the heat transfer efficiency. The heat transfer coefficient of plate heat exchangers is generally 1300~4000 kcal/m²·°C·h, which is 3~5 times that of shell-and-tube heat exchangers. This high heat transfer efficiency enables plate heat exchangers to complete the heat exchange task quickly under the condition of the same heat exchange demand, reducing the energy consumption of the heat exchange system.

In the heat exchange station of hydropower stations, the high heat transfer efficiency of plate heat exchangers can effectively reduce the power consumption of circulating pumps and fans, saving energy costs for hydropower stations. For example, in the cooling system of hydropower units, compared with shell-and-tube heat exchangers, plate heat exchangers can reduce the power consumption of circulating pumps by 20%~30%, and the energy-saving effect is significant. In addition, the high heat transfer efficiency also enables plate heat exchangers to achieve efficient heat recovery, improving the comprehensive utilization rate of energy and further reducing energy waste. The heat transfer coefficient of plate heat exchangers can be increased from 1200 W/(m²·℃) to 3500 W/(m²·℃) after optimization, and the heat exchange efficiency can be increased to 105%.

Plate heat exchangers are composed of many corrugated thin plates pressed at a certain interval, sealed around by gaskets, and clamped by a frame and compression bolts. The plate spacing is generally only 2~8mm, and the corrugations on the plate surface greatly increase the effective heat exchange area, making the unit volume heat exchange area of the equipment as high as 40 ㎡/m³, even up to 250 ㎡/m³ for some models, which is much higher than that of shell-and-tube heat exchangers.

This compact structure makes the plate heat exchanger have the advantages of small volume and light weight. Under the condition of the same heat exchange capacity, the volume of the plate heat exchanger is only 1/3~1/10 of that of the shell-and-tube heat exchanger, and the weight is only 1/5~1/8 of that of the shell-and-tube heat exchanger. For hydropower station heat exchange stations with limited space (especially underground hydropower stations), the compact structure of plate heat exchangers can greatly save the occupied space of the plant, making the layout of the heat exchange station more flexible. At the same time, the light weight of the plate heat exchanger also reduces the difficulty of transportation and installation, saving installation costs and construction time. For example, in the East Route Pumping Station Group of the South-to-North Water Diversion Project, full-welded plate heat exchangers are used to cool 10kV high-voltage motors, which not only saves space but also reduces installation difficulty.

The heat exchange medium of hydropower station heat exchange stations is mostly water (such as river water, lake water, seawater, or circulating water), which may contain impurities, salts, and corrosive substances, putting forward high requirements for the corrosion resistance of heat exchange equipment. Plate heat exchangers can be made of different corrosion-resistant materials according to the characteristics of the medium, such as 304 stainless steel, 316L stainless steel, titanium alloy, Hastelloy, etc., to adapt to different corrosive environments.

For example, for hydropower stations using river water or lake water as the cooling medium, 304 or 316L stainless steel plates can be selected, which have good corrosion resistance and can avoid equipment corrosion caused by impurities in the water. For coastal hydropower stations using seawater as the cooling medium, titanium alloy plates with excellent corrosion resistance can be selected, whose service life can reach 15 years or more, effectively resisting the corrosion of seawater. For hydropower stations with high water quality requirements, fully welded plate heat exchangers can be selected, which have passed strict air tightness pressure test to achieve zero leakage, effectively preventing the leakage of process media and mutual cross-contamination, and ensuring the safe and stable operation of the heat exchange system under harsh conditions. For hydropower stations with high sediment content in water, wide-flow channel plate heat exchangers (flow channel ≥6mm) with self-flushing design can be selected to prevent blockage, and the descaling cycle can be extended to 2-3 years.

In the heat exchange station of hydropower stations, the heat exchange medium (such as river water, lake water) often contains impurities and suspended solids, which are easy to scale and block the heat exchange surface, reducing the heat transfer efficiency of the equipment. Plate heat exchangers have the advantages of easy disassembly and assembly, which can be quickly disassembled by loosening the compression bolts, and the plate surface can be directly cleaned, which is convenient and efficient, and can effectively remove scale and impurities on the plate surface.

Compared with shell-and-tube heat exchangers, which are difficult to clean and require professional equipment and a lot of time, plate heat exchangers can greatly shorten the cleaning cycle and cleaning time, reduce the labor intensity of maintenance, and reduce the maintenance cost. In addition, the gaskets and plates of the plate heat exchanger are independent components, which can be replaced separately when damaged, without replacing the entire equipment, further reducing the operating and maintenance costs of the equipment. For example, in the heat exchange system of some hydropower stations, the cleaning cycle of the plate heat exchanger is shortened from 2 hours to 40 minutes, which greatly saves the cleaning cost. However, it should be noted that plate heat exchangers are sensitive to scaling and have high requirements for cooling water quality. Regular maintenance is needed to avoid blockage affecting the heat exchange effect.

The power generation load of hydropower stations often changes with seasonal changes (such as rainfall) and power grid demand, which requires the heat exchange system of the heat exchange station to have good flexibility and scalability. The plate heat exchanger is composed of independent plates, and the number of plates can be increased or decreased according to the change of heat exchange demand, so as to adjust the heat exchange area and heat exchange capacity of the equipment, which is simple and convenient to operate and has strong adaptability.

For example, in the flood season, the power generation load of the hydropower station increases, and the heat generated by the unit also increases accordingly. At this time, the number of plates of the plate heat exchanger can be increased to improve the heat exchange capacity, ensuring the normal cooling of the unit. In the dry season, the power generation load decreases, and the number of plates can be reduced to reduce energy consumption. In addition, by changing the combination mode of the plates, the flow direction and flow rate of the fluid can be adjusted to adapt to different heat exchange processes and medium characteristics. This flexible scalability enables the plate heat exchanger to adapt to the variable load operation of hydropower stations, improving the operational flexibility and economy of the heat exchange system. For high-head hydropower stations with pressure fluctuations, brazed plate heat exchangers with pressure bearing ≥4.0MPa can be selected to resist water hammer impact and achieve zero leakage.

The plate heat exchanger has a small heat loss during operation. Only the edge of the plate and the gasket are exposed to the air, and the heat loss coefficient is generally only 0.1%, which is much lower than that of shell-and-tube heat exchangers. Therefore, it does not need to be equipped with a special insulation layer, which not only saves the cost of insulation materials but also further reduces energy waste.

In addition, the high heat transfer efficiency and excellent waste heat recovery capacity of the plate heat exchanger can help hydropower stations reduce the consumption of auxiliary energy (such as electric energy and fuel), reduce energy costs, and at the same time reduce the emission of carbon dioxide and other harmful gases, which is in line with the national "double carbon" goal and the development trend of energy conservation and emission reduction in the hydropower industry, and helps hydropower stations achieve green and sustainable development. For example, some hydropower stations can save 30% or more energy by using plate heat exchangers compared with traditional air cooling systems.

Plate heat exchangers adopt advanced structural design and high-quality materials, which have high operational safety and reliability. For example, the fully welded plate heat exchanger adopts an elastic structure design, which can compensate for thermal expansion stress, ensuring that the equipment can operate stably for a long time in a high-temperature environment and extending the service life of the equipment. The sealing groove of the detachable plate heat exchanger is equipped with a liquid discharge channel, which can prevent the cross-contamination of various media. Even if leakage occurs, the medium will be discharged outward, avoiding safety accidents caused by medium leakage.

In addition, some manufacturers have introduced intelligent monitoring systems for plate heat exchangers, which can perform online health prediction, energy efficiency diagnosis, and cleaning effect evaluation of the equipment, and use machine learning technology to recommend the best operating conditions, further ensuring the safe and stable operation of the equipment and extending its service life. Compared with traditional heat exchange equipment, the service life of plate heat exchangers is longer, which can reduce the frequency of equipment replacement and reduce the overall operating cost of hydropower stations. For example, the service life of titanium alloy plate heat exchangers in coastal hydropower stations can reach more than 15 years, which is much longer than that of traditional shell-and-tube heat exchangers.

In the context of the continuous development of clean energy and the increasing requirements for energy conservation and environmental protection, the heat exchange station of hydropower stations, as a key supporting facility for power generation, plays an increasingly important role. Plate heat exchangers, with their unique structural advantages and excellent performance, have become an indispensable core equipment in the heat exchange station of hydropower stations. They play a crucial role in unit cooling, lubrication and hydraulic system temperature control, waste heat recovery, auxiliary system temperature regulation and ecological water temperature regulation, effectively ensuring the safe, stable and efficient operation of hydropower units, improving energy utilization efficiency, and protecting the ecological environment.

Compared with traditional heat exchange equipment, plate heat exchangers have obvious advantages such as high heat transfer efficiency, compact structure, strong corrosion resistance, easy cleaning and maintenance, flexible scalability, low heat loss, and safe and reliable operation, which make them highly adaptable to the complex working environment and variable load operation characteristics of hydropower station heat exchange stations. With the continuous advancement of hydropower technology and the increasing requirements for energy conservation and environmental protection, plate heat exchangers will be further improved and optimized in terms of material selection, structural design, and intelligent level. They will play a more important role in the green and sustainable development of the hydropower industry, helping hydropower stations achieve higher efficiency, lower energy consumption, and cleaner operation, and make greater contributions to the global energy transformation and environmental protection.