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MDP Hydraulics
The detachable gasket-type plate heat exchanger is an efficient and compact wall-type heat exchange device specifically designed for industrial applications that require frequent cleaning, maintenance, or process changes. Its core consists of a series of stamped metal thin plates with specific wave-shaped patterns, elastic sealing gaskets, and compression frames. The plates are sealed by the gaskets and arranged alternately to form narrow channels where cold and hot fluids flow alternately, enabling efficient heat exchange through the plates. Its detachable feature means that the entire plate bundle can be easily disassembled into individual plates, facilitating thorough inspection and mechanical/chemical cleaning on both sides of the plates, thus effectively addressing situations with easy scaling, particle content, or strict hygiene standards. In the field of mechanical manufacturing, it is a key thermal management component that ensures the stable and efficient operation of hydraulic systems, lubrication systems, and process cooling systems.
Under the condition that the two fluids do not mix with each other, heat transfer occurs through the plates.
1. Flow channel formation: When the plates with angular holes and the gaskets are stacked together, separate flow channels for cold and hot fluids are formed. Usually, the cold and hot fluids flow in opposite directions to achieve the maximum logarithmic mean temperature difference and heat transfer efficiency.
2. Turbulent flow enhanced heat transfer: The wave pattern design on the plates forces the fluid to generate intense turbulence in the flow channels. Even at a lower Reynolds number (Re), it can break the boundary layer and greatly enhance the heat transfer process. This enables its heat transfer coefficient to reach 3-5 times that of shell-and-tube heat exchangers.
3. Efficient heat exchange: Heat is transferred from the fluid with higher temperature through the extremely thin metal plates (usually 0.4-0.8mm) to the fluid with lower temperature, achieving rapid and efficient heat exchange.
• Heat transfer efficiency: The heat transfer coefficient is high, typically ranging from 3000 to 7000 W/(m²·K) (water-to-water condition), and the heat exchange efficiency far exceeds that of shell-and-tube heat exchangers.
• Compactness: The heat exchange area per unit volume is 2 to 5 times that of the shell-and-tube type, while the occupied floor space is only 1/5 to 1/8 of the latter.
• Design pressure and temperature:
Design pressure: Typically ranging from 0.6 to 2.5 MPa (6 - 25 bar), depending on the model and frame design.
◦ Design temperature: It is mainly limited by the material of the gasket. The conventional gasket (such as NBR) can operate at temperatures ranging from -20°C to 135°C; high-temperature gaskets (such as EPDM, FKM) can reach -25°C to 180°C or even higher.
• Small temperature difference at the end: It can achieve a temperature difference of approximately 1℃, with a heat recovery rate of over 90%, resulting in remarkable energy-saving effects.
• Flexibility: The heat exchange area can be easily adjusted by increasing or decreasing the number of plates; various process configurations can be achieved by changing the arrangement of the plates, enabling adaptation to different process requirements.
• Hydraulic system cooling: Cool the hydraulic oil to prevent the oil from overheating, which could lead to oil oxidation, viscosity reduction and decreased equipment efficiency. This ensures the stable operation of the hydraulic system.
• Cutting fluid/oil cooling: Used in CNC machines and machining centers, for cooling the circulating cutting fluid and lubricating oil, ensuring processing accuracy and prolonging the lifespan of the tools.
• Air compressor system cooling: Used for inter-stage coolers and post-coolers to reduce the temperature of compressed air, improve efficiency and separate condensed water.
• Injection molding machine temperature control: Used in the cooling water circuit of the mold to precisely regulate the mold temperature; or for cooling the hydraulic oil.
• Lubricant cooling for large equipment: such as lubricant cooling for wind turbine gearboxes, large compressors, and diesel engines.
Selection is a systematic process that requires detailed process parameters:
1. Define process conditions: Determine the types of fluids on both sides, flow rates, inlet and outlet temperatures, allowable pressure drop, and the physical and chemical properties of the fluids (such as viscosity, corrosiveness, and whether they contain particles).
2. Calculate heat load: Calculate the required heat exchange capacity (in kW) based on flow rate and temperature difference.
3. Select plate material and wave form: Choose the plate material based on the corrosiveness of the medium. Select the plate wave angle (high angle provides good heat transfer but has a large pressure drop; low angle is the opposite) based on flow rate, viscosity, and allowable pressure drop.
4. Select gasket material: Choose the gasket material based on fluid compatibility and working temperature.
5. Determine model and number of plates: Manufacturers usually provide selection software. Input the above parameters to calculate the required model, number of plates, and process arrangement.
6. Check pressure drop: Ensure that the calculated equipment pressure drop is within the allowable range of the system pump.
The equipment should be installed horizontally, with at least 1 meter of space reserved around it for maintenance purposes. When connecting the pipelines, excessive stress should be avoided on the heat exchanger interfaces. Before the first startup, the system pipelines should be thoroughly flushed.
When starting up, the valve on the low-temperature side should be opened first, followed by the valve on the high-temperature side slowly to avoid thermal shock. During normal operation, it is necessary to monitor the inlet and outlet temperatures and pressures.
• Maintenance and cleaning: Regular maintenance is crucial for ensuring efficient operation.
Regular inspection: Monitor the temperature and pressure differences at the inlet and outlet. A significant increase indicates signs of scaling or blockage.
Cleaning cycle: Depending on the cleanliness of the medium, it is usually necessary to clean the equipment once every 6 months to 2 years.
▪ Chemical cleaning (online/offline): For scale and other deposits, a cleaning solution composed of citric acid, phosphoric acid, etc. along with corrosion inhibitors can be used for continuous cleaning. It is strictly prohibited to use hydrochloric acid and other acid solutions containing chloride ions to clean stainless steel plates.
▪ Mechanical cleaning (after disassembly): Remove the plate bundles, and clean them using a high-pressure water gun, soft-bristled brush or nylon brush. It is strictly prohibited to use hard tools such as steel wire brushes to scrape the plates, as this may damage the protective film on the surface of the plates.
O-ring replacement: When the O-ring becomes aged, hardened, or undergoes permanent deformation, it needs to be replaced. During the replacement process, the sealing groove of the plate should be cleaned, and the new O-ring should be correctly installed using the appropriate adhesive or snap fasteners.
1. Pre-filtering: Install Y-type filters or basket filters (with a recommended precision of 100-500 μm) at the inlet pipeline of the heat exchanger and perform regular cleaning to reduce impurities from entering at the source.
2. Water quality/oil management: Soften, prevent scaling, and sterilize the circulating water; regularly test and replace hydraulic oil/lubricating oil.
3. Establish maintenance records: Record the time of each cleaning, maintenance, and component replacement, as well as changes in operating parameters, to facilitate predictive maintenance.
4. Standard operating procedures: Avoid frequent rapid cooling and heating operations and pressure surges (water hammer), to extend the lifespan of gaskets and plates.
