In industrial production, plate heat exchangers, as highly efficient and compact heat transfer devices, are widely used in various process flows. However, their pressure drop issues have always been a key factor affecting equipment operation efficiency and stability. This article will delve into the causes, impacts, and effective control and management methods of pressure drop in plate heat exchangers, helping relevant professionals better understand and address this issue, ensuring long-term stable operation of the equipment.
The pressure drop of a plate heat exchanger refers to the decrease in fluid pressure as it flows through the exchanger due to channel resistance and other factors. Pressure drop is an important parameter to measure fluid flow conditions and the performance status of the heat exchanger. Generally, the maximum acceptable pressure drop in design and operation ranges from 0.05 to 0.1 MPa, but the actual pressure drop is usually lower. The specific value needs to be calculated and confirmed according to design parameters and operating conditions. Excessive pressure drop brings many adverse effects, such as decreased operational efficiency, increased energy consumption, and even potential equipment damage. Therefore, reasonable control and monitoring of pressure drop are crucial for the efficient and stable operation of plate heat exchangers.
Pressure drop is a critically important indicator during the operation of plate heat exchangers. It not only directly relates to equipment efficiency and energy consumption but may also have a profound impact on equipment service life. Only by fully understanding the root causes of pressure drop increase can we take targeted measures to effectively control and reduce pressure drop, ensuring that plate heat exchangers maintain efficient and stable operation under various complex working conditions.
Impurity Deposition and Fouling: Whether it is industrial cooling water, heat transfer oil, or other process media, if water quality does not meet standards, long-term operation will result in scale, oil deposits, or impurity accumulation on the plate surfaces. These deposits reduce the cross-sectional area of the channels, increase fluid resistance, and cause pressure drop to rise. For example, in some cooling water systems, if water quality is not effectively treated, calcium and magnesium ions in the water will precipitate on plate surfaces, forming hard scale that seriously affects fluid flow.
Increased Fluid Viscosity: In low-temperature environments, the viscosity of heat transfer oil rises; if the solid phase content in the fluid exceeds standards, internal friction during flow increases, leading to pressure drop rise. For instance, in certain chemical production processes, when the viscosity of reactants increases due to temperature or composition changes, the pressure drop through the plate heat exchanger correspondingly increases.
Plate Blockage or Deformation: If plates experience local deformation due to impurity impact or chemical corrosion, flow channels narrow; in long-term uncleaned equipment, channels between plates may be completely blocked by debris, causing poor fluid flow and increased pressure drop. For example, media containing particulate impurities may block microchannels between plates after long-term operation, preventing smooth fluid flow.
Unreasonable Flow Channel Design: If the flow channel cross-section does not match the actual flow during selection, pressure drop will also increase. For example, when the actual flow is much greater than the design flow, the relative channel area is too small, fluid velocity becomes too high, and resistance naturally increases.
Aging Seals: When gaskets age, partial detachment may block channels, causing pressure drop to rise. Aged seals not only affect sealing performance but may also fall into channels, obstructing normal fluid flow.
Sudden Flow Increase: When the actual operating flow exceeds the design flow, fluid velocity in the channels becomes too high, naturally increasing resistance. For example, during production, if operational errors or equipment faults cause a sudden flow increase exceeding the heat exchanger's design capacity, pressure drop will sharply rise.
Improper Adjustment of Inlet and Outlet Valves: Improper valve adjustment can lead to uneven fluid distribution or pipeline blockage and pump pressure anomalies, indirectly causing increased pressure drop. For example, if the valve opening is too small or too large, normal fluid flow is affected, causing local pressures to be too high or low, thereby affecting pressure drop.
After deeply analyzing the many causes of pressure drop increase, we can more effectively explore targeted control and management methods. Simply knowing the problem is far from enough; the key is how to transform this theoretical knowledge into practical, feasible solutions to ensure that plate heat exchangers maintain an ideal pressure drop during long-term operation, achieving efficient, energy-saving, and stable heat transfer.
Regular cleaning is an important measure to control pressure drop. Choose cleaning methods according to the type of fouling: scale can be cleaned with chemical agents like citric acid or hydrochloric acid; debris blockage can be removed by high-pressure water jets or manual brushing after disassembly. At the same time, optimize fluid quality by installing filters at system inlets, regularly testing water quality, and adding antiscalants and corrosion inhibitors to reduce the likelihood of impurities and fouling at the source. For equipment-related issues, deformed plates and aged gaskets should be promptly replaced to ensure the equipment is in good operating condition.
During the design phase, determine the maximum allowable pressure drop according to the fluid transport pressure and flow requirements of the production process. Through economic analysis, determine the balance point between pressure drop, energy consumption, and equipment cost. For example, reducing pressure drop can lower pump energy consumption but may require larger equipment volume; calculate the total lifecycle cost to select the optimal pressure drop value. For highly viscous media, pressure drop limits should be relaxed; for easily vaporizing media, pressure drop should be strictly controlled, usually ≤30 kPa.
Flow velocity is the core factor affecting pressure drop, which is proportional to the square of flow velocity. Therefore, select a reasonable flow velocity according to the fluid type:
Tube side: liquid 0.5–3 m/s, gas 5–20 m/s
Shell side: liquid 0.3–1.5 m/s, gas 3–15 m/s
Avoid excessively high velocity causing overpressure drop or too low velocity reducing heat transfer coefficient. In shell-and-tube heat exchangers, increasing tube diameter reduces tube-side pressure drop but must balance heat transfer area; in plate-fin heat exchangers, increasing fin height enlarges flow channel cross-section, lowering pressure drop, suitable for high flow and low-pressure media.
Reducing the number of baffles can lower shell-side pressure drop but avoid overly large spacing causing tube bundle vibration. Replacing segmental baffles with spiral baffles enables spiral flow, reducing dead zones and local resistance, decreasing pressure drop by 20–30%. Reducing tube passes increases tube-side channel area, lowering pressure drop, but note that fewer passes may shorten residence time; compensate heat transfer area by increasing tube length. For large temperature differences, multiple heat exchangers in series with staged heat transfer can prevent excessive local velocities and pressure drop in a single unit.
Using low-resistance, high thermal conductivity materials, such as high-efficiency spiral corrugated plates, can effectively reduce pressure drop. Optimizing heat exchanger structures, such as adding flow channels or new plate types, also reduces pressure drop. Additionally, select structures that are less prone to fouling or equip the device with online cleaning systems for regular scale removal, maintaining unobstructed channels. For fluctuating flow, adjustable flow structures ensure pressure drop remains within allowable limits under variable conditions.
During plate heat exchanger operation, pressure drop stability is an important indicator of equipment condition. Normal pressure drop typically deviates by no more than 10% from design parameters; exceeding this range affects system circulation efficiency and may accelerate equipment wear. Therefore, real-time monitoring is needed to detect abnormalities promptly. When abnormal pressure drop occurs, comprehensive analysis should consider equipment operation records, fluid properties, and other information to determine whether it is caused by fluid property changes, equipment issues, or improper operation, and take corresponding measures.
To more intuitively demonstrate the combination of theory and practice, we present several real cases. These cases vividly show how precise analysis and effective measures resolve plate heat exchanger pressure drop issues in different industrial scenarios, achieving efficient operation and cost control.
Pressure Drop Solution in a Chemical Plant: A chemical plant experienced excessive pressure drop in a plate heat exchanger during production. Initial inspection revealed that impurity deposition in the fluid was the cause. The plant used chemical cleaning agents to clean the exchanger, installed filters at the system inlet, regularly tested water quality, and added antiscalants. After these measures, the pressure drop was effectively controlled, equipment efficiency significantly improved, and energy consumption was reduced.
Pressure Drop Optimization in an Industrial Cooling System: In an industrial cooling system, the plate heat exchanger had consistently high pressure drop, affecting system efficiency. Analysis showed that unreasonable flow channel design was the cause. The company worked with the manufacturer to adjust the flow path configuration and optimize channel design, increasing channel cross-section. After adjustment, pressure drop was significantly reduced, system operation stabilized, and cooling performance improved.
Pressure drop in plate heat exchangers is a very important parameter directly affecting equipment efficiency, stability, and energy consumption. By deeply analyzing the causes of pressure drop increase and implementing measures such as regular cleaning and maintenance, reasonable design and selection, optimizing operating parameters, improving exchanger structure, and using new materials and technologies, pressure drop can be effectively controlled and reduced, ensuring long-term stable operation. Additionally, strengthening pressure drop monitoring and fault diagnosis to detect and address abnormalities in time is also an important means of ensuring normal equipment operation.
