Introduction to Heat Transfer

by Patrick Ford
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Hey, guys, in this video, we're gonna talk about the different methods of heat transfer. Okay. When we started talking about thermodynamics, we talked about the idea of heat being transferred between two substances okay, that were in contact with each other. That's Onley, one type of heat transfer, though we even went so far as to talk about particles colliding at the boundary between two different substances and how that transferred heat between two different substances. But there are other kinds of heat transfer than direct conduction. Okay? And that's we're going to focus on in this video. All right, let's get to it. So far, we've discussed a lot about the quantity of heat transferred to do things. Okay, we talked about changing the phase right with latent heat. We talked about changing the temperature using our M cat equation way back when we talked about changing the size of things in thermal expansion. Now we need to talk about how he is transferred, okay? And like I said, we did spend some time in the beginning talking about two substances. Let's say A and B in direct contact where a had particles moving in random directions and every now and then A and B would have particles that would collide, and the collision between them would transfer heat from one substance to the other. In this case, from a to B, if a is hotter than be. But that's only one type of heat transfer. That's the heat transfer called conduction. There's also conviction, and lastly, there's radiation. Okay, okay. So as of right now, the Onley type of heat transfer that we've ever been talking about is conduction the direct transfer of heat between two objects that are in contact with one another. But there are still two other types to talk about. Okay. Each method of heat transfer has its own set of equations that govern how quickly or how much heat is transferred. Okay, but no matter how he does transferred, the equations of calorie amatrice still apply. So we still have are in cat equation and we still have our latent heat equation. Those still apply no matter how an object gets the heat. Whether that object gets it through conduction, whether it gets it through conviction or whether it gets it through radiation and vice versa for how it releases heat. If it releases heat through conduction through conviction or through radiation. Those two equations still apply. Okay, so let's talk briefly about the differences or not the differences. But what in fact, each of these methods entail. Okay, conduction is the transfer of heat from one substance in contact with another substance. Okay. And this is the type of heat. Transfer that up to this point, we've spent all of our time talking about the direct contact leads toa particle collisions along the boundary that exchange energy from one substance to the other. Right? That's conduction. We know all about it. Conviction is that indirect. So conduction is direct contact and directly transfer. Conviction is indirect. Transfer heat from one substance to another and this is accomplished by heating of fluid surrounding the hot substance. Okay, a classic example is a candle. So a candle with a flame on it heats the air in the immediate vicinity of that candle. Okay, that hot fluid then rises, so you can see I drew right this thing, implying that all of this hot fluid this hot air was rising up due to increased buoyancy. Okay, when a fluid gets hotter, the buoyancy of that fluid increases when it becomes more buoyant, it starts to rise in the fluid that it's in. So the air immediately around the candle starts to heat up, gets more buoyant than the air around it, and it starts to rise. That causes heat to go upwards. Okay, Now, the problem with conviction is that it's really, really, really complicated. Talk about it's a very complicated, fluid dynamics problem. And so we're not gonna talk about it any more than this. Just what conviction is. Okay, but conduction and now radiation, which I'm gonna talk about. Those have simple equations that we can learn how to use and how to apply to solve problems with them. That's not true for conviction. Okay, now, radiation is the release of heat emitted via Sorry of Let me start. Radiation is the release of heat via the emission off electro magnetic waves. Okay, electromagnetic waves carry and energy equal to the heat lost by the substance. Okay, So the substance is really, really hot. If it can radiate, it will radiate electromagnetic. I forgot the dick Electromagnetic waves and those electromagnetic waves will carry and energy equal to the heat lost by the substance. Like I said, not every substance can emit what we would call thermal radiation. Okay, I called it radiation here, but the technical name is thermal radiation. Because there are other types of radiation to Onley. Certain types of substances can emit thermal radiation. And we'll talk about that later. A common example of thermal radiation. Admission is ah, hot metal, glowing red or white as we can see here with this piece of whatever kind of metal it is in a blacksmith shop, the metal is heated so that it becomes pliable so that they can bend it and transform it into whatever they need. And when it's heated, it glows. Okay. And that glowing is the release of electromagnetic waves. Electromagnetic waves. I didn't say it is just a fancy name for light. Alright, guys, that wraps up our introduction to heat transfer and a brief overview of the three different types of heat transfer. Thanks for watching