Welcome back. So you were thinking about which sector had the most demanding requirement for power for energy transience. And so you went through the list of residential. commercial, industrial and transportation sectors. And you might have thought residential and commercial sectors both have diurnal needs, so from day to night, and there are seasonal needs, as you move from, let's say, winter to summer. So that provides demands for heating, ventilation and air conditioning. And then you might have moved on to the manufacturing sector, where you say hmm, well, the manufacturing demands might change again, both by day, different shifts, things like that. But I challenge you to look at the transportation sector, and consider the issues associated with energy and power demands of transportation. For example, let's say you're driving down the highway, semi-tractor truck pulls out in front of you, you need to get out of the way. You push your pedal, you push your foot down on the pedal, and you have an expectation that, that car will deliver power in a fraction of a second. Similarly, if you're on a jet airliner and you're getting ready to take off, that jet airplane needs to be able to provide thrust, in a matter of seconds. And it's a huge amount of energy. So the transportation sector not only requires, you know, very fast demand of energy but it also has to operate over a really broad range of speeds. And we have the additional constraint that the transportation sector has to carry its energy with it. The energy carrier Has to be on board, because the device is moving. So I'd argue the transportation sectors actually the most difficult to make changes because the demands for performance are so high. Okay, so now we've kind of discussed what are our drivers, we have supply and demand, we know there's population growth, we know that we are a global community and we have different needs around the world. Now what we need are the tools for us to be able to analyze these systems. And that's where thermodynamics is the tool set, that we need to be able to understand what we can accomplish, what we can't accomplish, what are the limits, what are the ideal behaviors? So thermodynamics is the study of energy and the interaction of energy with matter. So we want to consider energy systems, how we can obtain energy, how we, how we can transfer energy from one type of energy to another, and how we can apply energy to specific systems and processes. So now what I want to do is give you some examples, of those different types of energy transfer that we're going to consider in this class. So if we start with transforming energy, [SOUND] an excellent example that we're all familiar with is the classic pushing a ball up a hill. So we know that as we push the ball up the hill. We increase the potential energy of the ball and as we release the ball that potential energy is converted to kenetic energy. So we can see the conversion very obviously from potential to connect energy. So that's a good example of transforming energy. For example, [SOUND] Another good example that's relevant to the stationary power sector is a dam. So we know if we have a hydraulic system, that the water is elevated before it comes into the dam. And, then that water passes through turbine which are used to spin shafts, to generate power. And then they exit the damn at a lower elevation. So, we know there is a conservation of kinetic energy, of the water that's moving through the river. And potential energy because it's at a high high height prior to go through the damn. Into mechanical media, which is the spinning of the shaft associated with the turbines. So, thermodynamics helps us quantify the transfer of energy from one type of energy, one category of energy, to another. Additionally we want to be able to obtain energy. And that's, probably the best example is actually my, is extracting energy, is the example of the dam that we just considered. So, for example, we want to [SOUND] Convert that kinetic and potential energy to electrical energy ultimately to mechanical. To mechanical work which we will define in detail to electrical as we move further along in the course. So we'll transform, we'll obtain, we'll want to generate and apply. Energy in a number of different systems. And so there we can think about, lets generate power. For example to power a battery or excuse me. To use a battery to power a laptop computer, for example. So, how do we apply that energy transfer? Really involves three kind of classic energy transfer mechanisms, and we'll discuss those again in detail in this class. So, these would be examples where sometimes the actual example is to generate power. So that would be, you know charging a battery, for example. And sometimes, electrical power isn't the ultimate goal. So we might be generating, let's say, again, our example of a jet engine is actually, the goal is to generate thrust, not to generate power, in the conventional electrical energy sense, but it's to generate the thrust that's necessary to, get the jet off the ground. So again, thermodynamics covers all of these systems. Whether or not you're, you're, you know, key here is to generate stationary power or propulsion. Or whether or not you, might be almost a parasitic loss or, or a supporting need for whatever your application is. As long as there's any t, transfer involved. We have the tools within thermodynamics to analyze the system. Now heat transfer is a classic example of where we may not necessarily, we may not be generating, making a power plant or designing a new jet engine. But, heat transfer could be very relevant to our system. So here heat transfer is very specifically how energy is transferred when there's a temperature difference. So, any time you have two systems that are at two different temperatures, there's energy transfer due to heat transfer. So, so, any time, [SOUND] a temperature difference. Okay. So, heat transfer is a form of energy. So, lets just take kind of a classic academic example of, we have two bricks. And one is made of, one is a mass of an amount mass A, and the other has an amount mass B, and they can be the same amount of material or different, it doesn't matter. And we have two temperatures, where one is greater than the other, so let's say T, the temperature of material B is greater than the temperature of material A, and, because we want to make our life easier We'll just assume that the mass of the two systems is, are the same. If we bring those two breaks together we know because there's a temperature difference that there's going to be heat transfer between the two systems, intuitively we know the heat transfer will be from the high temperature material to the cold temperature material. So, we know also that the final state. When the system comes into equilibrium, which it will do, it will reach a thermodynamic a equilibrium that the termperature will be somewhere between the two temperatures of A and B. So if we bring them together, and add equilibrium. [SOUND] The temperature of A will equal the temperature of B. And this will be a temperature, so this will be, we'll call this the temperatures all the initial state, or state one. And the temperatures at state two or the final state will be equal, so again if we see any temperature difference between two systems, we know that there will be heat transfer, so that's a very easy energy transfer process for us to identify, now there are three types of heat transfer. And they're physics associated with each of those three transfers. Key transfer mechanisms. And those three types of key transfer are conduction, convection, and radiation. And we won't cover the details of the physics of these different mechanisms in this class. We'll just identify whether or not there is heat transfer present, and we'll quantify them in a general form. But we won't quantify them from initial princicples based on these conduction, and convection, and radiation principles. So that's heat transfer. Next we'll talk about fluid mechanics. So, fluid mechanics is a motion of the fluids which include, when I say a fluid, we don't just mean liquids. A lot of times people will think, oh, that's a liquid. But we mean liquids and gasses are both in the category of fluids. And the transormation of energy between mechanical and thermal forms of energy. So, fluid mechanics is the motion of the fluids. Thermodynamics doesn't consider the details of the fluid mechanics. We only consider the high-level pictures associated with. Energy transfer due to the motion and processes of fluids. So, now we need to go through some definitions. It's going to take us a little while to go and develop the tools so we, the vocabulary so we can actually go through and do quantitative analysis. So let's start with defining a system. So, system is the object that we're going to study. That's the object under consideration. And closed systems are systems where the mass is fixed. The mass does not vary in the time that we're considering. So like a brick, you know if we're considering maybe my brick cooling, or my two bricks coming into contact with each other, and equillibrating. That's going to be a closed system, where there is no mass crossing the system boundaries. An open system is one where mass can cross the system boundaries. So a great example for an open system would be, like your garden hose. So let's say you're directing water through a fire hose or a garden hose. You know that the water enters one end of hose and then it exits the other end of the hose. So that would be an open system. So what I want you to think about right now is if, let's consider a system that's maybe your coffee mug. If you want to consider the coffee inside your mug. Maybe we're going to do a heat transfer analysis to see how long it takes for my coffee to cool. Would that system be best described as an open system or a closed system? So I want you to think about that. And then the other example I want you to consider is the CPU or the mem, the power or the brain, if you will, in your computer. Is that best described as a control mass or a control volume? As an open or closed system? That's the best way to consider these two examples. So next time, we'll review what's the best way to approach these from a thermodynamic standpoint, and how to consider them, whether they should be considered open or closed? Thank you.
