I have a shell-and-tube heat exchanger I need to test. It is a water-to-water exchanger. My customer wants me to simulate the fouling of the heat exchanger by raising the cooling water inlet temperature. I have the calculations for this in a refrigerant condenser and evaporator but not in a fluid-to-fluid heat exchanger. Does anyone have the calculations for this?
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Heat exchanger preformance testing
- Thread starter RWR
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Much of basic information is missing. That is needed to understand the question.
Water fouling is based on velocity, temperature, metallurgy, and composition.
By 'simulating' you might mean by raising water temperature as far as you can and maintain required cooling. You need to know the actual clean heat transfer coefficients plus the tube wall resistance from a rigorous calculation and that referred to the tube od is your clean overall heat transfer resistance calculation. Then you apply the higher inlet temperature and for a fixed duty the outlet goes up about the same. If that temperature satisfies LMTD rules with the original hot stream outlet, apply the LMTD and surface to "back" out the allowed fouled overall heat transfer rate. That, as resistance mince the clean resistance is the sum of overall fouling resistance.
But you are simulating numbers since "fouling" is a physical substance for which the idea of simulating variance is practically a whole different science. If water min.velocity, composition and temperatures remain nearly the same, fouling will reach an asymptotic value and stay there. Low velocity or very high surface may introduce scaling or deposits beyond the scope of good practice "fouling factors"
Water fouling is based on velocity, temperature, metallurgy, and composition.
By 'simulating' you might mean by raising water temperature as far as you can and maintain required cooling. You need to know the actual clean heat transfer coefficients plus the tube wall resistance from a rigorous calculation and that referred to the tube od is your clean overall heat transfer resistance calculation. Then you apply the higher inlet temperature and for a fixed duty the outlet goes up about the same. If that temperature satisfies LMTD rules with the original hot stream outlet, apply the LMTD and surface to "back" out the allowed fouled overall heat transfer rate. That, as resistance mince the clean resistance is the sum of overall fouling resistance.
But you are simulating numbers since "fouling" is a physical substance for which the idea of simulating variance is practically a whole different science. If water min.velocity, composition and temperatures remain nearly the same, fouling will reach an asymptotic value and stay there. Low velocity or very high surface may introduce scaling or deposits beyond the scope of good practice "fouling factors"
EdStainless
Materials
You would need the design model for the HX.
What people do is raise the cooling water temp and watch the process outlet temp.
You don't really need to. Taking actual measurements at any point will confirm if the performance matches the design model.
But some people like to see that the heat transfer margin is real, they don't trust the math that they used in design.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
What people do is raise the cooling water temp and watch the process outlet temp.
You don't really need to. Taking actual measurements at any point will confirm if the performance matches the design model.
But some people like to see that the heat transfer margin is real, they don't trust the math that they used in design.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
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