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Design
Correlation between pressure drop and performance of a heat exchanger
Pressure drop plays a critical role in the design and performance of heat exchangers, influencing both efficiency and operational costs. This article delves into the correlation between pressure drop and heat exchanger performance, exploring ways to optimize it for maximum efficiency. From understanding its impact on flow rates to mitigating fouling and reducing pressure loss through design choices, we provide insights that help engineers create cost-effective and long-lasting heat exchanger solutions.
By Mehul K. Mehta, Founder and Managing Director, Kinam
During the journey of fluid inside the heat exchanger, high-velocity results in a pressure drop. The maximum allowable Delta P is defined by the process requirement and available pumping capacity. About 10 % accumulation is used up in this process. About 20 % is reserved to tackle variations in the process. When it is too high, the flow rate is reduced. While a small amount of pressure drop is essential for fluid movement, a larger one impacts operations. It may even cause higher operational cost and too much Delta P can result in equipment failure which is undesirable and affects the investment.
• What exactly is the correlation between pressure drop and the actual performance of a heat exchanger?
• How is the pressure drop reduced for optimal performance of Heat Exchanger?
• Is the flow rate also affected by a higher pressure drop?
• Why curtailing fouling is equally significant to pressure drop?
These are some noteworthy and major questions an experienced Heat Exchanger designer needs to tackle while calculating and preparing an optimal product for clients. Considering the importance of pressure drop for shell and tube designs, our experts throw light on these queries. The designer can prepare measurable metrics to curtail fouling: one of the critical factors affecting the Heat Exchanger application. The design should be so watertight that during normal conditions, there is no problem in the operational journey. And, the equipment remains a long-term investment for a plant. What this article aims to uncover:
• How does pressure drop affect heat exchangers?
• Prevention of failure due to pressure drop in process design of heat exchangers
• Thermal design fundamentals of shell and tube heat exchanger
Chlorine liquefier used in refrigeration process.
Pressure drop formulations terminology for reference: The pressure drop on circular pipe is calculated by Darcy Weisbach equation: ΔP = f( L / D)( ρV ²) = ρghl, where ΔP = Pressure Loss, N / m ² hl = frictional head loss, m L = pipe length, m D = pipe diameter, m V = average flow velocity of fluid(= Q / A), m / s g = acceleration due to gravity = 9.81 m / s ² f = friction factor, a dimensionless empirical factor that is a function of Reynolds Number( Re = DVρ / μ), where ρ = fluid density, kg / m ³
How does pressure drop affect heat exchangers? A pressure drop is recognized as an alteration in total pressure between two points in a fluid-carrying device / equipment. The fluid enters one end of the heat exchanger and leaves the other one. During this process, a pressure drop is created. This normally happens when there are restrictions or blockages to the flow. When the velocity is low, the pressure drop also reduces. And in the case of higher velocities, the pressure drop increases. Hence the pressure drop is related to the velocity and velocity is an important parameter to decide on heat transfer coefficients in the exchanger. Higher the velocity, higher will be the heat transfer coefficient and ultimately will result in higher pressure drop. The optimum design is one which offers lowest possible pressure loss with highest heat transfer coefficient. Hence as a designer most important is to select the right construction of the exchanger.
This is the reason why a designer has to find ways to optimize the pressure drop across the exchanger Correlated to this is the performance of the HE which a designer has to control. It is a significant perimeter that has to be factored. Erosion issues,
34 Heat Exchanger World April 2025 www. heat-exchanger-world. com