Optimize Heat Exchanger Efficiency by Reducing Resistance

Heat exchangers play a crucial role in industrial production, serving as one of the key pieces of equipment for achieving efficient energy utilization. As the demand for energy conservation and emissions reduction continues to grow, reducing fluid resistance and improving heat transfer efficiency in heat exchangers has become a primary focus for engineers. This article delves into several effective strategies for optimizing heat exchanger design, aiming to enhance overall system performance by reducing resistance, thereby lowering energy consumption and costs.

Balancing Increased Flow Rate and Reduced Resistance

 
In heat exchangers, increasing the flow rate of the medium is a common method for enhancing the heat transfer coefficient. As flow rate increases, turbulence intensifies, significantly improving heat transfer and thereby reducing the required heat exchange area. However, a higher flow rate also leads to greater fluid resistance, meaning the circulation pump must consume more energy, which in turn raises operating costs. Since the power consumption of the circulation pump is proportional to the cube of the flow rate, achieving a higher heat transfer coefficient solely by increasing the flow rate is generally not economical.
 
To achieve an optimal balance between flow rate and resistance, designers need to consider the physical properties of the medium, the structure of the heat exchanger, and actual operating conditions. In practice, a reasonable flow rate is generally in the range of 0.3 to 0.6 m/s, and resistance should be controlled within 100 kPa to ensure cost-effective operation.

Application of Thermal Mixing Plates

 
Thermal mixing plates optimize heat transfer and resistance characteristics by adjusting the structure of the plates. Based on the corrugated geometry on both sides, plates can be classified as hard plates (H) and soft plates (L). Hard plates typically have a corrugation angle greater than 90 degrees (about 120 degrees) and offer a higher heat transfer coefficient but greater fluid resistance. Soft plates have a corrugation angle less than 90 degrees (about 70 degrees), resulting in a lower heat transfer coefficient but also reduced fluid resistance.
 
By combining hard and soft plates, it is possible to create flow channels with high heat transfer and high resistance (HH), medium heat transfer and medium resistance (HL), and low heat transfer and low resistance (LL) to meet various operational needs. For instance, when there is a large flow of hot and cold media, thermal mixing plates can effectively reduce the plate area while maintaining high heat transfer efficiency. However, when the flow ratio of hot to cold media is too large, thermal mixing plates may struggle to achieve optimal thermal matching, requiring careful selection.

Asymmetric Plate Heat Exchangers

 
Asymmetric plate heat exchangers optimize heat transfer and pressure drop characteristics by altering the corrugated geometry on both sides of the plates, resulting in unequal flow passage cross-sectional areas for hot and cold channels. Typically, the side with the wider channel has larger corner hole diameters, which significantly reduces fluid pressure drop.
 
Compared to symmetric heat exchangers, asymmetric designs can significantly lower pressure drops without changing the heat transfer coefficient, making them particularly suitable for scenarios with large flows of hot and cold media. Data shows that asymmetric plate heat exchangers can reduce plate area by 15% to 30% under the same operating conditions, effectively decreasing equipment size and cost while improving overall performance.

Multi-Path Configuration

 
Multi-path configuration is an optimization strategy that adjusts the number of flow channels based on differences in hot and cold media flow rates. In cases of uneven flow rates, the side with lower flow can have more channels to increase flow velocity and heat transfer coefficient, while the side with higher flow has fewer channels to reduce heat exchanger resistance.
 
Although this configuration may introduce mixed flow patterns, slightly reducing the average heat transfer temperature difference, it effectively balances flow rate and resistance, enhancing overall heat exchanger efficiency. When designing multi-path heat exchangers, attention should be paid to the configuration of inlet and outlet pipelines to ensure convenient maintenance.

Installation of Bypass Pipes

 
For high-flow conditions, installing bypass pipes can effectively reduce flow within the heat exchanger, thereby lowering fluid resistance. The design of bypass pipes requires the installation of control valves to flexibly adjust flow distribution as needed. Additionally, using a counterflow arrangement helps to improve heat exchange efficiency, ensuring that the cold medium reaches the desired temperature at the outlet.
 
While the installation of bypass pipes increases system complexity and regulation difficulty, it provides an effective solution for conditions where the heat exchanger needs to meet both high heat transfer coefficient and low resistance requirements.

Comprehensive Optimization Recommendations

 
Optimizing the design and operation of heat exchangers requires a comprehensive consideration of various factors, including the physical properties of the medium, flow ratios, pressure drops, and heat transfer coefficients. Generally, the average flow velocity of the medium in the inter-plate channel should be controlled between 0.3 and 0.6 m/s, and resistance should be kept within 100 kPa. Depending on different application requirements, symmetric or asymmetric, single-path or multi-path plate heat exchangers can be selected, or bypass pipes can be combined to optimize performance.
 
By applying the above methods and strategies, fluid resistance in heat exchangers can be effectively reduced, and their heat transfer performance optimized. In practical applications, selecting the appropriate type and arrangement of heat exchangers, and reasonably controlling flow velocity and pressure drop, can not only enhance heat transfer efficiency but also extend the service life of the equipment and reduce operating costs. In the face of complex and variable industrial demands, the flexible application of these optimization techniques will provide strong support for achieving more energy-efficient and effective heat exchange processes.