What are Key Considerations in Plate Heat Exchangers Selection

  
Plate heat exchangers play a crucial role in industrial processes, with their selection and application directly impacting production efficiency and energy utilization. This article delves into the key considerations involved in the selection process of plate heat exchangers, including plate type selection, determination of flow patterns and channels, pressure drop verification, and specific considerations for their use as condensers and evaporators.
 

1. Plate Type Selection

 
The selection of plate type should be based on the actual heat exchange requirements, considering factors such as fluid pressure, temperature, and pressure drop. For situations allowing for higher pressure drops, plate types with lower resistance should be chosen to enhance heat transfer efficiency; conversely, situations requiring lower pressure drops necessitate plate types with higher resistance. Additionally, it's important to avoid selecting plates with excessively small surface areas to prevent issues such as reduced inter-plate flow velocities and diminished heat transfer coefficients.
 

2. Determination of Flow Patterns and Channels

 
Flow patterns refer to groups of parallel flow channels within the plate heat exchanger, where fluids move in the same direction, while channels represent the passages through which fluids flow, formed by adjacent plates. To maximize heat transfer efficiency, it's common to employ a combination of parallel or series-connected flow channels to create different configurations of cold and hot fluid pathways. These configurations should be determined based on the requirements of heat exchange and fluid resistance, aiming to equalize or closely match convective heat transfer coefficients within the cold and hot fluid channels. Despite variations in flow velocities between plates, calculations for heat exchange and resistance are typically based on average flow velocities.
 

3. Pressure Drop Verification

 
During the design and selection process of plate heat exchangers, there are specific requirements regarding pressure drop. Excessive pressure drops can adversely affect equipment efficiency and production costs, necessitating verification of pressure drop. If the verified pressure drop exceeds the allowable range, redesign and selection calculations must be conducted until the process requirements are met. From a technical and economic standpoint, the pressure drop for water-to-water heat exchangers should ideally be kept below 0.06 MPa.
 

4. Considerations for Use as Condensers and Evaporators

 
Plate heat exchangers also require special considerations when used as condensers and evaporators. Traditionally, these applications often employed shell-and-tube heat exchangers, but the advantages of plate heat exchangers, such as compact size and high heat transfer efficiency, have led to their increasing adoption. Despite being primarily designed for liquid-to-liquid heat exchange, plate heat exchangers still outperform shell-and-tube exchangers when used as condensers without any modifications. In recent years, specialized plate evaporators and condensers have been developed abroad and widely applied with excellent results.
 
In conclusion, optimizing the selection and application of plate heat exchangers requires a comprehensive consideration of multiple factors, including plate type selection, determination of flow patterns and channels, pressure drop verification, and specific requirements for their use as condensers and evaporators. Only by thoroughly addressing these key issues can plate heat exchangers deliver optimal heat transfer efficiency and energy utilization in industrial processes.