I’m confused; could you please tell me the key factors that determine the heat transfer coefficient of a heat exchanger?

This post was last edited by wiseboy on 2017-6-23 21:55. Your view is completely wrong; it shows no understanding at all of the concept of convective heat transfer. Let’s look at the \"series resistances\" in heat transfer: fluid core —> boundary layer —> fouling —> tube wall —> the other side. {1. Convective heat transfer} {2. Thermal conduction} {3. Thermal conduction} {4. Thermal conduction}. Yet you overlook the core portion: the red area. When calculating heat exchangers, these 4 resistances are treated as a single \"heat transfer film,\" which can be considered as a \"total boundary layer\" – encompassing the resistances of all 4 components. And you have only considered the narrow sense of the true boundary layer; you have no awareness of an important aspect related to convective heat transfer. Clearly, you lack basic knowledge, which is why you are a \"amateur scientist\". This is also the origin of the “membrane coefficient”. Heat has to make a significant effort to move from the center of the fluid to what you call the boundary layer; this process involves \"convection (the main mechanism)\" plus \"heat conduction (a much less important mechanism)\". That’s why, for calculations, we need the fluid’s thermal conductivity (required for heat conduction) as well as its flow velocity (required for convection); of course, these two parameters are also necessary for calculating the boundary layer.

First of all, thank you for your reply. However, I regret the *habit of arbitrarily deducting points from you. Rationality isn’t about withholding criticism; it can be expressed. The boundary layer can be calculated using formulas, and it can match the boundary layer thickness derived from the overall heat transfer coefficient. First, by temporarily excluding the effect of scaling, the only factor that determines the heat transfer coefficient is the boundary layer. This is clearly stated in the book \"Heat Transfer Enhancement Techniques for Tubular Heat Exchangers\": most of the thermal resistance is concentrated in the lower layer of laminar flow, that is, the boundary layer. Returning to the unavoidable issue of scaling, my numerous experiments have clearly proven that by eliminating the boundary layer, the conditions for scaling are removed. Meanwhile, my experiments to eliminate the boundary layer also yielded terrifying heat transfer coefficients. Just to be safe, more tests should also be conducted. It is not appropriate to make it public for now. Questioning is a good way to discover the truth, but the habit of dismissing all new technologies based on assumptions rather than solid theory needs to be corrected.

This post was last edited by wiseboy on 2017-6-25 at 16:26. “There’s no reason to put a label on anyone.” Hello, you’re being unreasonable; you’re the one who puts those labels on yourself. I’m just repeating what you said: “Got a thorough beating from experts and was labeled as a pseudo-scientist.” Moreover, no matter which book you read, you’re wrong, without a doubt. The boundary layer is just one of them; you haven’t taken into account the convective heat transfer of the main body. The greater the viscosity, the larger the proportion of convective heat transfer resistance.

I have a question: what is heat exchange? Return to basic concepts. What are the three elements of heat exchange? Please take another look at the heat transfer textbook.