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00:00:00Marco Marigo: Okay. Today, I will finish the lecture that we started to yesterday about the domestic or total production systems.
00:10:460Marco Marigo: Just to summarize very quickly. We have seen different types of domestic water production systems, how they are classified and how we can, starting from the energy balance, find the volume and the thermal power of the coil inside the
00:32:750Marco Marigo: inside the tank. By selecting, by by deciding the preheating time and the delivery time of the domestic hot water that that was more or less the content of the lecture that we did yesterday
00:51:915Marco Marigo: today. My colleague, Marco Marigo, will show you how to do it for how to do the calculations in a simplified way for the report of this course.
01:06:670Marco Marigo: But just before I start, please apologize because I had problems with the recording also yesterday. So you don't find the video the video recording of yesterday's lecture. I hope I will not have this problem again in the future.
01:27:615Marco Marigo: Also because I changed laptops. So there should not be the issue anymore. Anyway. Today, I just need the 5 min, because I want to.
01:41:560Marco Marigo: talk about 2 other things before I leave the floor to to Marco. And the topic of today is about what to do when we find when we have buildings with many
01:57:450Marco Marigo: dwellings, like, for example, apartment blocks, or with the many users, like many offices that have. Okay, in case of offices. Normally we don't have a significant domestic or total demand.
02:15:450Marco Marigo: but especially for residential units. You might have the case of many dwellings, many building units, and in that case the calculation of the mass flow rate that we called dot u yesterday depends.
02:36:842Marco Marigo: Is not merely a sum of the mass flow rate of all the users, but it it takes into account the fact that not all the users demand for the domestic hot water simultaneously, if you remember. In one of the 1st slides I showed just a drawing with many peaks. Okay? Because, domestic hot water demand. I I
03:06:10Marco Marigo: I just refresh
03:08:730Marco Marigo: from yesterday. It's it's very user dependent demand. So it it depends on the habits of the of the users involved.
03:20:540Marco Marigo: Therefore, when we have many users, we should account for this diversity of the users that for example, they don't. They don't all make the showers at the same hour in the morning, and they don't have the same use patterns, therefore, for sizing purpose. We use this contemporaneity factor, which tells us how many
03:49:870Marco Marigo: which gives us a factor that we should multiply to the sum of the mass flow rates. Okay? So for each
03:58:816Marco Marigo: dwelling we have a certain muslerator, and in case of many
04:05:300Marco Marigo: dwellings, we make the sum of these mass flow rates, and we multiply the contemporaneity factor. For example, if you see here in this plot that I'm showing you for 9 building units, you would consider a contemporaneity factor of 50%.
04:29:260Marco Marigo: Okay? And as you can see, it is more or less reaching an asymptote. So after a certain number of units, you don't decrease anymore. So this is very important. Otherwise you would oversize the domestical water system.
04:50:120Marco Marigo: Another
04:53:370Marco Marigo: Another thing which I I think is very important is the integration of renewable heat for
05:07:730Marco Marigo: comment.
05:11:130Marco Marigo: I also per cal pdf.
05:17:194Marco Marigo: so the as you can see one of the in in these slides, please focus only on the figure on the left. Now, you can see there is a solar collector
05:32:770Marco Marigo: which delivers heat, which supplies heat to the domestic auto tank in parallel to the gas boiler, which is the other coil supplying heat to the tank.
05:48:200Marco Marigo: and then you have the blue pipe on the bottom, which is the pipe coming from the aqueduct and the red pipe on top, which is the
06:02:690Marco Marigo: which is the pipe. Go the supply pipe to the users. Okay, so
06:10:20Marco Marigo: this is an example of a mixed hot water tank where we use the
06:18:280Marco Marigo: the lower coil for the integration of solar heat.
06:23:640Marco Marigo: Why do we use the lower part, because normally these tanks are stratified. So it is. We cannot. In the reality. There is stratification in the, in the.
06:41:560Marco Marigo: in the tanks, and some tanks are designed to favor stratification. Okay? So from a geometrical point of view, they enhance the stratification, and therefore you have the water in the bottom, which is colder than the water on on the upper part of the tank.
07:04:820Marco Marigo: so it the the
07:10:110Marco Marigo: The performance of a gas boiler, would not change much, depending on the position of the coil. Okay, so. But the
07:22:970Marco Marigo: the performance of a solar collector is affected by the capability of the of the tank to lower down the temperature. So if you want to have a
07:41:280Marco Marigo: ideally cold temperature back to the solar thermal collectors, it is better to place the coil in the lower part of the tank because of stratification.
07:53:140Marco Marigo: And now you can also have a look to the other figure where you can see that there might be that there are tanks that are able to combine both domestic hot water production and to have also and to also provide heat for space heating
08:15:880Marco Marigo: just just for you to know, depending on the number of of connection points in the in the tank, you might be able to to use the tank as a also as a thermal buffer for space for the space heating system. Okay.
08:38:919Marco Marigo: then, the very last thing that I would like to show is in the other
08:48:390Marco Marigo: computer. So let me let me make a last trial because
09:10:670Marco Marigo: I want to show you some real layouts
09:15:420Marco Marigo: of domestic with the drawings of domestic hot water systems.
09:22:50Marco Marigo: So
09:40:780Marco Marigo: Marcostair, La la Mail Yamanato link.
09:55:925Marco Marigo: we need.
10:17:520Marco Marigo: Okay, so you should be able to see
10:21:430Marco Marigo: the website. So this is taken from a Hvac system a manufacturer of components of Hvac systems.
10:36:370Marco Marigo: And here you can see some examples of design of domestic tutor system.
10:47:21Marco Marigo: This is an example where you can see the tank which is on the left side. It is supplied by the circulation pump of the heat generation unit. And on the right part you have the secondary side of the system. Okay? The green. The green pipe is the pipe coming from the aqueduct. As you can see, it is
11:15:890Marco Marigo: more complex than the simplified scheme that I that I showed so far. But this is a a real schematic. So how it would look like in a in a real design.
11:30:420Marco Marigo: And you can see that we have different pipes going to the users.
11:37:710Marco Marigo: The users are
11:39:730Marco Marigo: different showers sinks in the same building. Okay? And we have 3 pipes going to the, to the users, to the loads.
11:51:910Marco Marigo: So these pipes are this one which is the coming from the aqueductor which is already pressurized by the water distributor. So it comes with a certain pressure that that's why you don't find the pump here, and when you tap and ask for cold water this will deliver this pipe will deliver the cold water.
12:18:60Marco Marigo: and the other 2 pipes are the supply pipe coming from the domestic water tank and the recirculation pipe, which is kind of the return in case the domestic hot water demand. There is no domestic hot water demand. But you you want to keep the pipes warm.
12:43:440Marco Marigo: Okay, because you want to have. You don't want to wait for 2 min to have hot water. Therefore we have a recirculation pipe which has the purpose of making warm water circulate through the plant even when the demand is low. Okay.
13:09:950Marco Marigo: province of water management, even. Gmail account.
13:16:590Marco Marigo: Okay? And in in this case, you also see that we have a 3 way valve here that enables the recirculation of water. So it will. So normally you would mix the cold water with the hot water coming from the tank to the to reach the desired supply temperature to the users.
13:46:280Marco Marigo: And this 3 wave valve can be also
13:52:940Marco Marigo: controlled in a way to
13:57:600Marco Marigo: to basically to circulate more hot water, reaching a higher set point, and therefore to make what we called yesterday the thermal shocks or antigenella cycles.
14:14:830Marco Marigo: So instead of being only okay. This schematics does not show the controller. It is another one, but it doesn't. It doesn't matter that there should be a controller here where where you don't want only to have a constant supply temperature to the users.
14:41:280Marco Marigo: but it is programmed to also make some temporized anti Legionella cycles, so that instead of having, for example, I don't know. 45. Imagine you have. If this is a mixed hot water tank, you have 60 degrees in the
15:04:930Marco Marigo: hot in the mixed hot water tank. You don't want to send 60 degrees to the shower. You want to send more or less 45 degrees. Okay, so you normally mix with cold water. And in case of anti legionella cycles.
15:21:230Marco Marigo: this set point is increased to I don't know 70 degrees, so that the heat generation will continue heating up the plant, and there is a recirculation of hot water coming from the recirculation pipe until the the tank reaches this temperature to do the until Juneela cycle.
15:49:20Marco Marigo: Okay, for I don't know 30 min every day. For example, it is set inside the Controller, which opens and close the 3 way valve later on in the in this course, we will
16:04:610Marco Marigo: specifically look at how these valves work. So for now I think this is enough.
16:12:990Marco Marigo: Do you have any any questions?
16:18:460Marco Marigo: Otherwise I leave the floor to Marcumarigo for the calculation part for the record.
16:32:935Marco Marigo: Any?
16:35:230Marco Marigo: Yes, this is the pump?
16:39:150Marco Marigo: Yeah.
16:59:90Marco Marigo: I need to share directly this one. Right? Okay
17:07:520Marco Marigo: with the queries.
17:17:440Marco Marigo: Okay, so thank you. Jacopo.
17:21:200Marco Marigo: I know that there is someone that
17:24:935Marco Marigo: already knows me. But for those that have never seen me I'm Marco Marigo, Researcher, and my supervisor is Professor Michael, and during this course I will take
17:36:880Marco Marigo: 2 topics. We will talk about this sizing part for the domestic hot water, and then we will see also a second topic about the sizing of the duct for a ventilation of layer system. But today the focus is just on this part on domestic hot water. I know that yesterday, and also with the
17:58:30Marco Marigo: explain you about this this topic, but I want briefly to refresh the topic you have already talked about.
18:12:762Marco Marigo: So we started by talking about the practical realization of this system for sizing and for producing domesticated water. So which are the systems which are the
18:30:490Marco Marigo: and
18:33:20Marco Marigo: gauge back that we can use to the production systems we can use to produce domestic hot water. And also we will move then to the sizing of domestic hot water. So for each one of these systems we will see how to size these systems.
18:52:190Marco Marigo: then we will also see the main assumption for the sizing process. So we will have. The 1st 2 points in this list are about the practical application of the theory you have seen until now. Then, the 3rd point is about a typical question for designers. So if we want to design a system which are the assumptions we have to make.
19:15:220Marco Marigo: okay, and this is the point that we will try to answer in the 3rd part of this lecture.
19:23:30Marco Marigo: then at the end, we will see about the calculation of the energy needs.
19:27:750Marco Marigo: So it's important for us to start by distinguishing 2 points, 2 very important points. The sizing is a procedure that help us in deciding 2 parameters. The 1st one is the power that we have to install. The second one is the water volume that we have to install.
19:49:450Marco Marigo: So when you are designers. You have to decide these 2 parameters. When you have power and water volume, you can take a catalog. You can read, you can search and decide. Okay, this is the machine I want to install in my building.
20:04:30Marco Marigo: And this is the 1st part. We will talk about it in this point
20:13:350Marco Marigo: in this point. Okay, in the second part we will see a difference.
20:20:960Marco Marigo: and it is the calculation of the energy need. So
20:24:262Marco Marigo: these are 2 situations. The 1st one. I am the designer, and I have to design
20:29:820Marco Marigo: the second part. I have the system, and I want to estimate how much is the energy that the system uses to produce the domestic water. So these are the 2 main topics. And it's very important for you for you not to make confusion between these 2 points. Okay? So in the 1st part, we are talking about power and water volume for sizing. In the second part, we are talking about energy, that the system I have installed is using to produce my domestic water.
21:00:880Marco Marigo: At the end we will give some instruction for the record. But if someone has not understood, understood what I'm talking about. Please rise your hand and ask for at the end of the lecture.
21:12:640Marco Marigo: Okay, so let's start from this point.
21:18:500Marco Marigo: A brief sum up of what you we have talked about in the theoretical part you have seen.
21:27:660Marco Marigo: Is there the possibility of taking out this.
21:41:260Marco Marigo: mister?
21:43:680Marco Marigo: Oh, nice.
21:46:100Marco Marigo: Okay, so this is the 1st
21:54:660Marco Marigo: the 1st distinction you have made during the the previous lecture.
21:58:990Marco Marigo: It's about the production with storage or the instantaneous production. Okay, usually in the system. So you can install at your house, in a building or in whatever you want, whatever you want.
22:10:840Marco Marigo: There is the possibility of installing a system with the water storage. Okay? So heating up the water inside the storage and then delivering the water, or to make an instantaneous production. Okay, in the instantaneous production. You don't have any storage. Okay? But you have to produce the water at the temperature that is required
22:35:780Marco Marigo: instantaneously. So in the moment that the user open the sink, open the shower you have to produce instantaneously an amount of water. Okay, a big amount of water at the temperature requirement.
22:49:180Marco Marigo: And this is the distinction in the 1st one you have to.
22:54:660Marco Marigo: heat up the water volume, and then when it's open, okay
22:59:836Marco Marigo: the the sink or the shower, the water flows to the user.
23:06:110Marco Marigo: This is a very important difference, because,
23:10:670Marco Marigo: there is advantages. There are advantages, advantages for both the systems. But as you have talked about yesterday in the instantaneous system, okay, you have lower volumes. So you don't need a big room installing a big tank, for example. Okay? And so you can
23:32:730Marco Marigo: install, for example, your boiler, your gas boiler in your bathroom. It's more compact.
23:39:30Marco Marigo: But the problem is that that system must have a high power. Okay, so this is the disadvantage, the disadvantages of the instant data system.
23:49:190Marco Marigo: And why is it a problem to install a high power, a high power system.
23:55:520Marco Marigo: Well, if you are thinking about designing a 0 energy building or a low energy building.
24:03:930Marco Marigo: the 1st thing you have to do is to reduce consumption, of course, and installing low power is a 1st step for reducing consumption. Okay.
24:15:840Marco Marigo: on the other side, there are some advantages of a water storage system. For example, in that case you you can install, for example, lower power.
24:29:470Marco Marigo: We will see in the example. But the problem is that you have a volume of water that is stagnant. Okay, as you have learned yesterday, for example, so you will have to use energy to carry out some cycle. Then you will need probably a room to install the the water storage, and so these are the disadvantages of the production with storage.
24:51:940Marco Marigo: But then we can also make another distinction. We can work with the direct production of domestic hot water or an indirect production.
25:01:910Marco Marigo: as you can see from this picture. That is very simple. You can directly heat up the water.
25:08:610Marco Marigo: both in the storage or in the instantaneous production, through the combustion of gas, for example, or through an electrical resistance. So, for example, you have your water storage in this case, with domestic water inside, it's called. You want to directly heat the water. And so you put an electrical resistance with the power that we are calculating. Now. Okay, you put inside the electrical resistance that push up the temperature of your storage.
25:38:270Marco Marigo: So this is the director. With electricity or or with gas.
25:44:930Marco Marigo: I can use a different approach.
25:47:240Marco Marigo: That is an indirect approach.
25:49:540Marco Marigo: So I can, for example, heat up another fluid, and with this fluid at high temperature I can heat up the volume of water domestic heater.
26:01:00Marco Marigo: and also in this case I have different approaches. I can use an immersed heat exchanger. Okay, like this. So, for example, here I have my boiler.
26:10:340Marco Marigo: I am heating up a fluid. This fluid releases the heat to my tank of domestic hot water.
26:22:200Marco Marigo: I have a second approach. I can use an external heat exchanger. So, for example, here my boiler heat up another fluid and through a plate heat. Exchanger, I'm releasing heat to my volume of domestic hot water
26:41:400Marco Marigo: on the instantaneous part. Okay, I just want to focus on these 2 type of systems. For example, I have the plated exchanger.
26:52:260Marco Marigo: so I can produce instantaneously the water domestic hot water through this plated exchanger, or I can have this system with a water tank
27:03:230Marco Marigo: with an immersed heat exchanger that is eating up the domestic water pay attention. There is a difference between the right and the left part of this table.
27:15:130Marco Marigo: for example, this plated exchanger is different from this one, as as you can see
27:21:210Marco Marigo: here after the heat exchanger, there is a volume of water. In this case. I'm just delivering the domestic hot water to the user, which is the difference. The difference is that this
27:34:190Marco Marigo: plated exchanger will have a higher size than this one, because, for example, here I must provide a delta T to the domestic cold water around 30 40 degrees. In this case I can also have a lower Delta T, because I can use the energy that
27:55:408Marco Marigo: is stored in the water volume. Okay? So in this case I will have a much lower surface of exchange in the plated exchanger.
28:07:590Marco Marigo: which is the problem of this kind of system. Of course, I have to buy a tank. Okay, is the 1st one and the second one. I need an additional pump this one that in this case I don't have, because I have just this pump and this pump. Okay, the 2 pumps on the 2 sides of the heat exchanger in the middle with an external heat exchanger and the water tank. I need 3 pumps.
28:32:470Marco Marigo: The 1st one is the internal of the production system. The second one is the domestic water pump. And then I have also a 3rd pump.
28:45:780Marco Marigo: Yeah, exactly in this table, always
28:57:350Marco Marigo: the domestic water is green and orange, and the technical water is blue and red.
29:06:860Marco Marigo: There is also another difference that I want to to notice is between these 2 technologies. Here we have
29:15:560Marco Marigo: domestic hot water inside of the tank. Okay? So I heat up the domestic hot water through any exchanger inside, where there is an operative fluid, a working fluid isolator, which are these working fluids? In this case I have the reverse. So I have a tank with technical water inside, and the domestic water is flowing inside
29:41:500Marco Marigo: the go with.
29:53:00Marco Marigo: So
29:55:680Marco Marigo: I also have to tell you that there is another possibility you find on the market another kind of system.
30:04:360Marco Marigo: That are used to produce domestic hot water through heat pumps.
30:10:370Marco Marigo: Okay, in Italian we used to say something like, so you find a heat pump inside with the tank for the domestic production. Usually you need at least 50 liters of water storage. Okay, it's very easy. And then schematics is very easy. So you have, for example.
30:36:190Marco Marigo: oh, a a tag.
30:39:840Marco Marigo: And on the top part, for example, you have the the fan. Okay? And here
30:48:630Marco Marigo: you have the thermodynamic cycle.
30:52:130Marco Marigo: And how can we do it like this?
30:55:920Marco Marigo: Okay, it's something like this.
31:02:610Marco Marigo: Okay? And here you have your tank. So the condenser side. Okay, is a heat exchanger inside the the tank of Mexico. But here, for example, with this kind of system, so the production through heat pumps can never do instantaneously. Okay, you need. You must have a
31:30:460Marco Marigo: a a tank, a water volume, because, you know, you can't reach high too high power and too high temperatures in the production for the with the heat pumps. So in order to
31:46:240Marco Marigo: being able of delivering domestic hot water, so keeping the energy producing the energy required for domestic hot water. You need to have the tank. So no instantaneous production through heat pumps. This is very important.
32:03:910Marco Marigo: Okay, but apart from this, we can move to the sizing part.
32:11:910Marco Marigo: So let's don't know how to do it. Okay, okay, so let's start from the easiest.
32:21:110Marco Marigo: Okay, the easiest is the instantaneous production
32:24:880Marco Marigo: of domestic hot water. And let's see how to perform this sometimes production.
32:30:310Marco Marigo: Hmm, please go on the possibility of it to clean the blackboard. No.
32:43:90Marco Marigo: okay, we'll do like this without any problem.
32:48:270Marco Marigo: Someone store. The, okay, we finally planned.
33:03:380Marco Marigo: Thank you so much.
33:08:40Marco Marigo: Okay, so let's start from the simultaneous production of domestic hot water
33:13:18Marco Marigo: the equation is very easy, and you already know it.
33:16:160Marco Marigo: So if I want to instantaneously produce domestic hot water, I just need to focus on this equation.
33:29:460Marco Marigo: Okay? So it's just up to decide which is
33:37:170Marco Marigo: the flow rate of domestic hot water. I already know the Cp of domestic hot water. I need to decide the
33:46:850Marco Marigo: temperature supply, because I can assume that
33:52:420Marco Marigo: I receive the water from the apple at 10. So this is a very easy equation. And starting from this point, I can already understand which are the factors that affect the production of my domestic water. The 1st one is the quantity of domestic water I need to produce. Okay, probably you have
34:15:489Marco Marigo: talked about this as the mass of delivered domestic hot water that this, this amount that usually we
34:26:659Marco Marigo: use the kilograms or the liters.
34:30:909Marco Marigo: Later we will come back on. Why are we using liters for talking about the mass? But in technical volumes you can find both of these units of measurement for
34:43:840Marco Marigo: this parameter. The second parameter is, of course, this one. So which is the supply temperature
34:51:139Marco Marigo: at which I can deliver this domestic hot water, and the 3rd one is the time in which I need that I need to deliver
35:02:830Marco Marigo: these 2, I think, on Twitter
35:05:280Marco Marigo: in seconds or in power. Then we will see how we will organize
35:10:910Marco Marigo: in a proper way all these.
35:15:540Marco Marigo: This point I can define this domestic hot water.
35:22:660Marco Marigo: this flow of domestic out of water
35:26:320Marco Marigo: as the mass of water delivered per the unit of time in which I have to deliver this mass. Okay, this is quite easy. But in this way I can focus on the 3 aspects that are very important in my case to define which is
35:44:580Marco Marigo: the amount of which is the power that they need to produce this domestic water. So these 3 parameters are the time in which I have to deliver the water, the mass of water I have to deliver and the supply temperature.
36:03:700Marco Marigo: Okay, so once, by starting with this, I can move to everything.
36:11:130Marco Marigo: So let's think, really.
36:15:180Marco Marigo: And I think we have to supply.
36:18:900Marco Marigo: or better, to size and instantaneous domestic hot water production system. Or
36:31:110Marco Marigo: if that
36:35:610Marco Marigo: oh, okay, Pascobagno Italia, that must.
36:43:560Marco Marigo: Which? 500,000. Sorry
36:47:825Marco Marigo: that means 150 liters of domestic hot water in the 10 min
36:59:830Marco Marigo: at 40 40,000 min.
37:03:670Marco Marigo: So this is a typical requirement for this time type of system. So usually, bathroom needs 150 liter in very short time, because you open it, and then you make it flow.
37:16:750Marco Marigo: Okay? And so in this situation I can understand that
37:22:560Marco Marigo: now it's quite easy to see.
37:27:810Marco Marigo: Don't worry here. I will
37:30:480Marco Marigo: use the capital. L. It's quite easy to see that if I am talking about water, I just remind you the density of water is one kilo per liter. Okay?
37:43:940Marco Marigo: And so I can define which is the mass flow of domestic of the water. I will call you like this.
37:54:160Marco Marigo: That is 900
37:59:450Marco Marigo: kilogram per hour if I need 150 liter per 10 min. Okay, this means that I need 900 kg per hour. And so when I have to size
38:13:740Marco Marigo: the power that they need, they require the power. In this case it's just like this, and you Cp of the water
38:25:630Marco Marigo: supply temperature minus the temperature of the aqueduct.
38:33:960Marco Marigo: Now, I'm using technical units, so pay attention to this.
38:41:940Marco Marigo: The mass of water is 900.
38:45:620Marco Marigo: The Cp. Of water is
38:49:280Marco Marigo: one. And this is why I use technical units, because the Cp of water in technical units is one kilocalories per hour plus per liter per celsius liquid. So this simplify a lot. The calculations.
39:04:350Marco Marigo: The supply water is this, the supply temperature is 40 is required, and
39:12:80Marco Marigo: the temperature of the apple is 10.
39:15:60Marco Marigo: Okay. So also the dimensions, for example, in this case with Ryan, another quarter here I have.
39:25:260Marco Marigo: I don't know if you can see good kilograms per hour.
39:33:00Marco Marigo: Is this our requirements?
39:38:650Marco Marigo: We get it because.
39:47:300Marco Marigo: can you see? Well, in blue or not? Okay.
39:51:250Marco Marigo: here we have kilogram per hour.
39:54:50Marco Marigo: Okay, here one. The Cp is in Philip countries her power.
40:02:490Marco Marigo: We have either size of the week.
40:08:700Marco Marigo: and here the Doctor King is in the news.
40:16:240Marco Marigo: You can see easily that we are talking about 900 per 30. And so the result here
40:27:740Marco Marigo: I finish the platform.
40:29:580Marco Marigo: It's equal to 27,000 kilo calories per hour.
40:39:230Marco Marigo: How much is it?
40:44:930Marco Marigo: Thank you.
40:46:460Marco Marigo: No. Okay, okay, yeah, yeah, exactly. There is no square in the right?
41:03:767Marco Marigo: Right? Right? Right?
41:09:766Marco Marigo: Got it.
41:15:600Marco Marigo: Are you sure about that?
41:20:430Marco Marigo: We can work on this.
41:22:310Marco Marigo: Okay, now we are okay.
41:26:780Marco Marigo: How much is it?
41:28:860Marco Marigo: It is around for the, you know.
41:34:490Marco Marigo: Okay?
41:37:80Marco Marigo: And this is the 1st point about my instantaneous production of domestic. I have sized an instantaneous system of domestic water. So I need, for example.
41:49:680Marco Marigo: a gas boiler that provides me this
41:53:420Marco Marigo: power or an electrical resistance that provide me this power, but, as you can understand, I cannot install in my house 30 kilowatt of electrical resistance to heat up the domestic water, for my bathroom is something that can is not possible.
42:12:250Marco Marigo: So we have 2 approaches we can use. Okay, this is the 1st point that I've talked to you about the problems of this system is about the high power that is required. So I need to reduce this power. If I have a fire gas boiler. I can reach these values, but I must use all for domestic water or for the heating system of my building. If I need to install electrical resistance. I need to do something else
42:41:60Marco Marigo: which are the 2 approaches that I can follow. I can both reduce the flow rate.
42:47:60Marco Marigo: So this flow rate is quite high, so I can reduce the flow rate. But the most useful approach that I must call that I can follow is to install a water storage. Okay, so change the kind of system I have to produce the domestic oculator. So to reduce the power I need, I must install the domestic water system.
43:12:140Marco Marigo: So this is about the sizing of this kind of system. Very easy, because once you have the requirements of domestic hot water, you can immediately calculate this sometimes power. You need to produce that domestic hot water at the temperature you decide. You can see here inside 46 degrees. It's
43:31:60Marco Marigo: kind of usual choice.
43:36:220Marco Marigo: You can see also here the problem. I have only size for one
43:41:740Marco Marigo: device. Okay? Probably if I add to this device, maybe one shower, one sink, and so on. I will obtain also a higher power that is not possible to install in a building.
43:57:400Marco Marigo: Okay, so this is the 1st one, let's think about having
44:05:140Marco Marigo: a another system. Okay. But an indirect production of domestic hot water. We are talking about the second case. So we imagine, to have a plated exchanger.
44:20:530Marco Marigo: And so by having this plated exchanger I want to show you
44:28:20Marco Marigo: the application through a numerical exercise, but just
44:32:960Marco Marigo: the logic behind the sizing of these kind of systems.
44:41:100Marco Marigo: So which is the logic behind the sizing. You know that
44:44:960Marco Marigo: if I have to size the same power. So let's imagine that we are talking about the same power. We're calculating before the required power is always the same. Okay.
45:00:810Marco Marigo: But here I have another fluid that is heating. My
45:08:720Marco Marigo: my! My domestic hot water. So the fluid must deliver
45:16:130Marco Marigo: must yeah. Exchange this energy, and the energy of the fluid is the mass of the fluid.
45:26:250Marco Marigo: the Cp of the fluider
45:31:890Marco Marigo: and the true temperatures. Okay, the inlet in the plated exchanger and the outlet in the plate exchanger. But at the same time you know that the same power delivered by the fluid can be calculated as
45:48:960Marco Marigo: the second equation with the E transfer coefficient of the creative exchanger, the surface
45:55:500Marco Marigo: in the plated exchanger and the mean logarithmic main recording.
46:05:240Marco Marigo: that's the main waiting term. Okay, that's right.
46:08:260Marco Marigo: And so if I want to produce
46:12:20Marco Marigo: the same power. So the amount of power required by my domestic water system that is, the one that is on this side of the plated exchanger must be equal to this one, so I can put here this one, which is the only unknown value here is this one.
46:31:390Marco Marigo: Why? Because if I'm making a process of using water. Of course I know the Cp, okay, I can expect. I know also the
46:44:459Marco Marigo: the flow of the mass flow rate on the side
46:50:590Marco Marigo: on this side of the of the plating. This changer and I make the bodies that I also know the supply temperature of this fluid. If this fluid is technical water, I can produce with a gas boiler, for example.
47:05:520Marco Marigo: a certain amount of water at a certain temperature. These are all known values in sizing this plate heat exchanger. And so, when I have all these parameters, I can calculate the only unknown value in this case, that is this one.
47:23:480Marco Marigo: the surveys of exchange for this system. So if I can
47:31:105Marco Marigo: calculated this temperature T. 4, I can also calculate the mill operating temperature, and then by assuming this K. That is quite easy. I can also calculate this. As
47:44:900Marco Marigo: so, the procedure is this one. I calculated the required power by for instantaneously produce the domestic hot water. Then
47:55:420Marco Marigo: I can. It is equal to the power in the fluid side in the working fluid side. Then from this I can calculate the outlet temperature of the plated exchanger on the technical motor side, and then from this I can calculate the Delta T and L.
48:16:400Marco Marigo: And from this the last part is calculating the S. Of course, I need to estimate this Cape value.
48:27:990Marco Marigo: That is something that it's easily calculated. You have also attending the course of
48:35:714Marco Marigo: heat exchanger, and the the K value is very easy to calculate the 4 plate heat exchangers water water.
48:46:520Marco Marigo: Okay?
48:50:590Marco Marigo: And then there are the last 2 points that we will focus a little more on these, because these are more complex.
48:58:970Marco Marigo: The 1st one is the one on the left part, so we will see how to find the Q value and the volume of water for a mixed hot storage water
49:13:890Marco Marigo: production system. We will see in this case a simplification in the next slide
49:30:40Marco Marigo: will simplify this kind of problem like this.
49:34:730Marco Marigo: Well, I'm sure we do thank you.
49:40:730Marco Marigo: In this case we will simplify with the drawing like this.
49:46:100Marco Marigo: So this is, for example, the banker.
49:49:720Marco Marigo: Okay?
49:51:190Marco Marigo: And we will see that we will have.
49:56:00Marco Marigo: Yeah, this system that these
50:00:110Marco Marigo: the water sorry, the power delivered, or, better not, the power delivered, the power, the heat products released into the water tank. Okay. And here we will have
50:15:420Marco Marigo: water entry and water entertainment.
50:19:300Marco Marigo: Don't look at where I'm putting the
50:24:700Marco Marigo: these arrows. Okay, the position is not important. Now, now, it's just simplification. To understand how it is built. Usually, as you know, there is certification inside. And so we should also think about that. But by now we are just simplifying this approach. And so here I supply
50:46:490Marco Marigo: a flow, and I'm exiting with the same flow.
50:52:960Marco Marigo: Here I have the temperature of the output. And here I have the temperature of supply.
51:01:940Marco Marigo: I think if you later, we will see with the regulatory.
51:06:240Marco Marigo: Okay. So this is done, the simplification. And here we have the losses.
51:15:830Marco Marigo: But this general approach
51:18:590Marco Marigo: is valid for all this system of production on the left part of the table. So this Qs. We will assume it constant, but can be given to the volume of water through gas burning through electrical resistance.
51:36:360Marco Marigo: through an immersed heat exchanger or through an external heat. Exchanger. Okay.
51:42:438Marco Marigo: in this last part is kind of strong simplification. Because this, Us.
51:50:140Marco Marigo: Okay, maybe it's constant. But okay, it's quite a strong hypothesis, but for the 1st 2 hypothesis having a constant Qs. Is quite a good, a realistic also hypothesis.
52:06:800Marco Marigo: So this will be the layout. The general layout that can
52:15:20Marco Marigo: contain all these production system on the left part of this slide.
52:19:830Marco Marigo: And the last approach is this immersive exchanger? It's the same concept. Okay. But
52:28:90Marco Marigo: we will simplify this representation with the same. So the same Qs that is delivered to the water volume, the same
52:39:570Marco Marigo: thermal losses.
52:41:720Marco Marigo: But here the difference is that
52:44:290Marco Marigo: in this point we are introducing the domestic of the water, or better domestic and the domestic enters. The volume mixed with the water inside reaches the temperature of delivery, and then is supplied. In this second part there is an exchange.
53:05:700Marco Marigo: so there is no contact between the water inside the bank that is in this case technical water and the water inside in this ginger. That is the domestic hot or cold water. Here it's hot.
53:21:210Marco Marigo: And here this one.
53:28:180Marco Marigo: Okay, I'll book.
53:30:180Marco Marigo: It's clear enough. So these are the 2 more general systems in which you can produce your domestic computer
53:41:110Marco Marigo: excluding the those that we have seen before.
53:46:110Marco Marigo: So we will start right now by propaging on this 1st system
53:56:520Marco Marigo: the mix of orders over the season so, and I will just
54:07:430Marco Marigo: stop a little bit on the general
54:13:910Marco Marigo: concepts, because I know that you have already talked about this in detail.
54:18:920Marco Marigo: As you can see. There, there is the representation that is more or less the same that we have done here. The domestic cold water enters the tank at around 10 census degrees. It's heat output through a constant heat flux, that is Qs, and then it's when it reaches the
54:40:910Marco Marigo: the temperature to be supplied is supplied to the user.
54:45:870Marco Marigo: I want you to pay attention to this point. Remember always that we are moving from flow rates. This is the flow rate that is delivered. The domestic hot water flow rate. But sometimes we will talk about the mass of delivered water that is, as I wrote down before. It is the mass flow rate of domestic water divided the delivery time.
55:14:670Marco Marigo: and let's go very fast. So assuming that the the this
55:21:850Marco Marigo: well temperature is a temperature to you, so I am assuming that I already heated up this volume of water. I can make a representation
55:32:950Marco Marigo: of this system, considering it as an thermodynamic system to be analyzed. And if I look
55:42:300Marco Marigo: at the fluxes, at the heat fluxes and the mass fluxes that are moving
55:49:310Marco Marigo: inside and outside the boundary of this system, I can see that there are some fluxes that I can see very well. You have already known this, seen this equation, and so I can have a term that is the internal energy variation of the system.
56:06:110Marco Marigo: Okay?
56:07:773Marco Marigo: That is depends. Okay on the time variation of the internal temperature. This tu is the temperature of the water inside the tank. It's also the same. Then the delivery water temperature, because, of course, I am delivering this
56:29:550Marco Marigo: temper. The water inside of the same temperature. I'm assuming no stratification, so I can assume that
56:36:800Marco Marigo: tu is the temperature of the delivery and also of the water inside the tank. So the internal energy variation of the system depends on the variation of the
56:49:580Marco Marigo: temperature of the water inside the water of the tank and its variation on time.
56:58:830Marco Marigo: So this internal energy variation depends on the sum between the fluxes, the heat fluxes that are entering the system, and I have that the power Qs. Is entering the system. The power gas is the heat released by my source to the water.
57:20:140Marco Marigo: and the other flux that is entering is that flux. That is the
57:26:900Marco Marigo: cold flux. Okay, so is the mass entering. Okay, I have
57:33:140Marco Marigo: a mask that is entering the
57:36:670Marco Marigo: the tank at the temperature of the aqueduct. That is this one?
57:42:250Marco Marigo: Then I have also some fluxes that are exiting the water tank.
57:48:260Marco Marigo: The the fluxes that are exiting are the mass flux
57:53:737Marco Marigo: that is delivered to the user. And this this term, okay, the same flow rate at the temperature to you.
58:03:90Marco Marigo: And the last one is this flux that is around the thermal losses
58:10:50Marco Marigo: of this system. That depends on, of course, the heat exchange coefficient, so the insulation of my tank, the surface of the tank, and the temperature difference between the internal water temperature and the temperature of the environment. Where, again.
58:29:750Marco Marigo: my bank, so I can simplify and say, Okay, I have this internal variation that depends on
58:41:140Marco Marigo: the heat released by the heating flow, the heating fluid, or released by the electrical resistance or released by my power system. I don't know which it is.
58:53:580Marco Marigo: The heat exchange, due to the heat
58:56:200Marco Marigo: of the water that enters and exit the tank, and then the losses through the ammo
59:04:850Marco Marigo: I have simply copied the equation in the 1st part. So this is the same equation than before.
59:15:700Marco Marigo: Okay?
59:17:580Marco Marigo: And now what we are doing to go on with our approach is that instead of solving this as a
59:31:720Marco Marigo: as an equation, a differential equation.
59:36:590Marco Marigo: I'm integrating the general thermal balance.
59:40:160Marco Marigo: Taking into account these 2 times.
59:45:120Marco Marigo: This is just a simplified equation the detailed equation is the one that showed you yesterday. Okay, but this simplified method
59:57:910Marco Marigo: usually can be used, and don't take too large error in the size, in the sizing of the system, despite is quite good.
00:09:800Marco Marigo: So we have to distinguish between true timing.
00:15:840Marco Marigo: So when I'm installing them, these systems with the water storage.
00:24:110Marco Marigo: I am doing this because, as I've mentioned before.
00:28:690Marco Marigo: I can lower down the power released to the water. Okay, and give this power in a higher range of time. Okay. So, as you already know, because you are engineering students at the last year
00:45:620Marco Marigo: I can give the same energy, the system, deliver the same energy
00:51:550Marco Marigo: in a short amount of time with the high power, or with a large amount of time with lower power. Okay? And in this case we are doing this point, we are trying to reduce the power. And so
01:06:710Marco Marigo: this time, okay, I can assume. I have a preparation time and then a delivery time.
01:13:980Marco Marigo: I move to the next slide, and then we will come back to this.
01:19:570Marco Marigo: What's happening in these 2 amounts of time.
01:24:520Marco Marigo: So I have a preheating time in which I'm moving from the starting temperature, the temperature of the aqueduct, that is, the temperature inside the tank to the maximum temperature that I can have inside the tank.
01:40:610Marco Marigo: So I'm preparing the water. But in this time, okay, during this preheating time. I won't have any water exiting the tank. This value is equal to 0. This value is equal to 0. I'm not delivering water, so I'm not making other water entering the tank. So I have just my losses and the heating system that is heating my water.
02:06:850Marco Marigo: So I'm moving from this temperature of the aqueduct to the maximum temperature.
02:13:730Marco Marigo: Then, when I reach the maximum temperature, I have to supply the water, because now the user will switch on the the shower I don't know, and then
02:26:420Marco Marigo: the water starts flowing and being delivered to the user. So we will choose the
02:41:20Marco Marigo: the time in order to have this
02:44:290Marco Marigo: profile of water temperature inside the tank at the end of the delivery time. Okay, I need to have at least the temperature required by the user.
02:59:450Marco Marigo: We will see more in detail later. This point, but
03:06:105Marco Marigo: what is required is that at the end of the delivery time I'm not going too low with the with the water temperature, because if
03:16:689Marco Marigo: I don't size properly the volume of water. Okay, I risk that at the end of the delivery. My user is still opening the shower, and the water that is flowing is lower than 40 60 degrees. If 30 or is 20, okay? And then this is not comfortable, for the user is what we are trying to avoid.
03:40:600Marco Marigo: Okay, so what I'm doing is to
03:46:200Marco Marigo: once it's clear. This division in the 2 timing. So preparation, time and delivery time.
03:53:180Marco Marigo: I am integrating this equation.
04:00:480Marco Marigo: taking into account the 2 in 2 periods, the 1st one.
04:09:510Marco Marigo: The 1st equation is the integration of this one, considering
04:14:770Marco Marigo: the sum of the preparation and the delivery time. So all that the the range of time
04:22:380Marco Marigo: in which we are working.
04:26:30Marco Marigo: And so you can see that this term, okay, as we are integrating on the true timing becomes the volume.
04:35:10Marco Marigo: the Cp.
04:36:540Marco Marigo: The density is considered as one. Okay, for this reason it disappears.
04:42:390Marco Marigo: and the temperature difference between the 2 timing.
04:48:150Marco Marigo: As you can see, we are moving from.
04:51:120Marco Marigo: If we are integrating in the whole amount of time. The final temperature is the temperature tu, and the starting temperature is ta.
05:00:690Marco Marigo: And so this is the reason why here we have tu minus ta tu is the temperature
05:09:490Marco Marigo: that I have to deliver the water to the user. And PA is the temperature of the aqueduct.
05:17:810Marco Marigo: Yes.
05:23:810Marco Marigo: 1, 3
05:29:270Marco Marigo: eating what? Yeah, we are also, yeah, yeah, we're considering we are decoupling the heating of the hot water and the supply. So they can also happen simultaneously. Okay, I have no, no problem about this.
05:45:680Marco Marigo: Okay, so the temperature is lower than the maximum temperature, because we are extracting more heat than the one that we are providing during each one.
05:56:380Marco Marigo: The profile temperature is this one, yeah, yeah, exactly. Exactly. But yeah.
06:19:30Marco Marigo: yeah, because for this reason we are using lower powers. Okay, if
06:26:770Marco Marigo: we are able to keep the temperature constant with the power we supply, we are using an instantaneous system.
06:33:850Marco Marigo: Okay.
06:35:640Marco Marigo: the the reason of using this is that we can keep the power lower. And for this, okay, this is just a simplified representation. So probably the the coefficient of this line is lower. So
06:49:690Marco Marigo: I'm continuously heating up the water and supplying it. Yeah, if the question was how to control the supply temperature.
07:06:910Marco Marigo: yeah, of course.
07:08:70Marco Marigo: Okay, the control of the supply temperature is always mixing.
07:15:230Marco Marigo: Yeah, we are mixing bag. So you have your water, for example, at 40
07:19:610Marco Marigo: or 50. I don't know. Yeah, you deliver water. Okay, to the user one
07:26:510Marco Marigo: with the same water from the aclude.
07:29:560Marco Marigo: Okay.
07:34:140Marco Marigo: we are using a mixing volume to control the temperature supply. Okay? So the control of the temperature supplied is always made me mixing the temperature from the tank with the one from the aqueduct.
07:51:840Marco Marigo: This is something that did we
08:00:210Marco Marigo: exactly in the sink, for example, in the shower manually.
08:20:560Marco Marigo: Okay. So this is one of the terms. The others are the power that is released.
08:28:479Marco Marigo: and, as you can see, we are moving by integrating this equation that is based on terms that are power terms, heat flux terms. We are integrating on time, and we obtain energy terms. And so this energy is the energy delivered by my
08:48:60Marco Marigo: production system in the true timing, the sum of the true timing. And so we are
08:56:600Marco Marigo: putting this term as
09:00:510Marco Marigo: this energy term as the multiplication of the factor between the power and the time in which this power is delivered
09:13:380Marco Marigo: the second term. Okay, is the the change
09:20:270Marco Marigo: in internal energy due to the continuous flux. Okay of mass that is delivered in the total period.
09:30:310Marco Marigo: So when I, integrating the
09:35:630Marco Marigo: this term in the time I obtain that this, that before was a
09:44:130Marco Marigo: in mass flow rate, becomes the total mass of water delivered in that time.
09:54:430Marco Marigo: Total mass of water delivery in that time in the delivery time, of course, because before this is equal to 0, okay, but this term enters the
10:08:50Marco Marigo: internal energy variation.
10:10:270Marco Marigo: Okay, and the second term depends on the mass of water that is delivered.
10:17:830Marco Marigo: Who they're using.
10:19:80Marco Marigo: The last term is the thermal losses. Okay.
10:24:470Marco Marigo: distinguished between the thermal losses in the preheating time and the thermal losses in the supply time.
10:34:560Marco Marigo: Here, as my unknown values are the power
10:39:440Marco Marigo: and the volume that are the true terms that I need to size the system. I need also a second equation to have.
10:47:960Marco Marigo: and
10:50:630Marco Marigo: a system, a linear system of 2 unknown variables in 2 equations, and this second equation is obtained by integrating the same equation only in the heat up period. So in the heat up period. As I said before, I have that this flow rate is equal to 0, so all this term will be neglected. Sorry all this term will be neglected.
11:16:560Marco Marigo: and the balance is the energy delivered to the water tank. Only in the preheating time.
11:25:170Marco Marigo: with the internal energy variation. Here you can see that the Delta T is different, because
11:32:840Marco Marigo: in the preheating time the temperature
11:35:630Marco Marigo: is between the maximum temperature and the aqueduct temperature
11:40:870Marco Marigo: and the thermosis we will take into account in this second equation is only the part about the preheating time.
11:52:240Marco Marigo: but how to calculate the thermal losses?
11:55:150Marco Marigo: There is a simplified approach that you can see here at this slide, and
12:03:100Marco Marigo: we have distinguished between the normal losses in the supply
12:07:330Marco Marigo: phase and the in the preheating phase.
12:11:100Marco Marigo: Hmm.
12:17:290Marco Marigo: and the equation is very easy.
12:20:110Marco Marigo: It's calculated as the transfer coefficient. The surface of the tank, the transfer coefficient of the tank
12:28:410Marco Marigo: and the delta T between the environment temperature, the environment where we have placed the tank and the 1st temperature is a temperature that is assumed. Okay, if I assume that this is the profile of the water temperature inside the tank. I can assume that in the preheating time
12:50:590Marco Marigo: my temperature inside is the mean, a mean temperature between the TA. And the T. Max.
12:58:700Marco Marigo: Okay, it's just a really simplified method in the supply time. So in this second part, I can assume that it's the average between the maximum temperature and the supply temperature. And so I'm just considering these 2 terms as to very simplified terms that enters the thermal losses. Calculations.
13:22:190Marco Marigo: Why can we use these
13:25:50Marco Marigo: simplified approach? Because we will see in calculations. This term is very, very low compared to the other terms. And so we can also neglect this term, and if we don't consider the thermosis, we don't make it high at all in the sizing of the system.
13:44:270Marco Marigo: This is because water tanks are really insulated with a lot of insulation very high level of insulation, and so the thermal losses can be considered can be neglected in the total calculations.
14:00:120Marco Marigo: So to make a recap which are the parameters that I need to size my system as
14:15:960Marco Marigo: you can read the slide
14:18:900Marco Marigo: for sizing, so for deciding the thermal Ps and the capacity P of the storage, you must decide the supply time.
14:30:00Marco Marigo: the preheating time, the amount of hot water supply.
14:35:810Marco Marigo: the temperature at which you supply the water to the user, the temperature of the available fresh, cold water, and then the maximum temperature inside the tank. I'm assuming in these calculations that the power queue is constant.
14:54:340Marco Marigo: And so this is the
14:59:400Marco Marigo: The 1st 2 equations are those that we have calculated right now for the mix of water storage system.
15:09:260Marco Marigo: In the second part of the stop the slide.
15:13:70Marco Marigo: You can see also the equations that you are using to size another kind of system. That is
15:24:210Marco Marigo: this one.
15:26:440Marco Marigo: Okay?
15:27:690Marco Marigo: So the instantaneous system, with the technical water inside and immersed heat exchanger internal heat exchanger.
15:38:640Marco Marigo: I have explained only the detailed calculation for a
15:46:630Marco Marigo: the mix of the water stat storage system.
15:52:30Marco Marigo: But the I don't know. Maybe next time I will have time to to show you about this.
16:01:220Marco Marigo: then I will decide. I don't know if I have time. I will do also the detailed calculation for this system with internal. Now I want to move. I prefer to move to the exercise
16:14:900Marco Marigo: that is this one.
16:18:130Marco Marigo: So we will try to make some calculations and the size
16:30:410Marco Marigo: that must supply 100 kg of water
16:34:630Marco Marigo: at 40 Celsius degrees, with a supply time of 1 h.
16:40:970Marco Marigo: Alright, I will try to do at the blackboard.
16:46:476Marco Marigo: Let's see, how are you close?
16:49:930Marco Marigo: Pretty much.
17:01:210Marco Marigo: Okay. So we are talking about a master of quarters
17:11:790Marco Marigo: that must be delivered at 100 kilometers.
17:19:580Marco Marigo: the temperature at which it is required to increase
17:30:20Marco Marigo: and the supply time it's going on right.
17:41:390Marco Marigo: Assume a preheating time of 5 h.
17:44:110Marco Marigo: and that the maximum temperature inside the tank is 16 Celsius, so the maximum temperature is 60. Sensitivity and
17:57:160Marco Marigo: the preheating time doll be simple to follow ours
18:07:720Marco Marigo: for the calculations assume also that the water from the output enters at tensions degrees.
18:14:910Marco Marigo: So this is another important value.
18:19:550Marco Marigo: The temperature of the room where the tank is installed is 20,
18:30:650Marco Marigo: and for the terminal circulation assume that T is 0 point 8, you know, economies
18:39:190Marco Marigo: an hour per square meter, 10 degree, and the surfings
18:47:370Marco Marigo: of the text is 1.3 square inches.
18:53:270Marco Marigo: so what they need to know is the US.
18:59:680Marco Marigo: And the volume of storage.
19:02:790Marco Marigo: And also they asked me to repeat this calculation without neglecting the thermosis, I changed my mind.
19:14:790Marco Marigo: Now I don't know if I am still recording.
19:18:590Marco Marigo: because I will try to do this on the whiteboard.
19:24:540Marco Marigo: So let's see.
19:40:460Marco Marigo: let's try.
19:42:310Marco Marigo: Okay.
20:02:250Marco Marigo: no.
20:05:50Marco Marigo: Does it work perfect?
20:14:340Marco Marigo: And okay, now, it's working.
20:17:950Marco Marigo: Okay.
20:19:620Marco Marigo: So
20:29:710Marco Marigo: as you can see here, you have the data.
20:35:490Marco Marigo: Okay?
20:39:90Marco Marigo: And the 1st step
20:44:90Marco Marigo: we're performing the calculation.
20:47:105Marco Marigo: Is the point. One
20:54:140Marco Marigo: is calculating the thermosis.
21:12:400Marco Marigo: as we have seen before, we have to calculate the thermosis on the preheating time
21:19:370Marco Marigo: and on the delivery time, on the preheating time
21:26:640Marco Marigo: we have that the thermal losses, or okay S.
21:35:850Marco Marigo: The medium temperature in preheating mine was the ambient temperature.
21:49:30Marco Marigo: The mean temperature in the preheating is, as we have seen before, is the maximum temperature
22:02:410Marco Marigo: plus the temperature of the aqueduct
22:06:340Marco Marigo: divided by 2, so in this case is 60 plus 10, divided by 2 35 Celsius degrees.
22:17:800Marco Marigo: So here we have key is 0 point 9 3 1.3 35 minus 20,
22:33:480Marco Marigo: that is equal to 18.1 Watt.
22:38:800Marco Marigo: Pay attention. I have put 0 point 9 3, because here I made the conversion. This is in bad
22:45:750Marco Marigo: on square meter calving.
22:48:260Marco Marigo: In the data of the exercise. I have it in kilocalories per hour, square meter. Such a degree.
22:55:730Marco Marigo: This is in square meters.
22:58:920Marco Marigo: This is in Calvin.
23:01:240Marco Marigo: And so this is you.
23:05:840Marco Marigo: If I had used the technical units, I would have obtained the 15.6
23:14:910Marco Marigo: kilo calories per hour.
23:24:310Marco Marigo: The thermal losses in the delivery time
23:35:760Marco Marigo: is K.
23:37:260Marco Marigo: S.
23:38:520Marco Marigo: The mean temperature in the delivery minus the I mean temperature.
23:45:840Marco Marigo: But here the temperature is the temperature maximum temperature plus the temperature
23:58:800Marco Marigo: of the supply to the user.
24:02:90Marco Marigo: And in this case we are talking about 40 plus
24:13:420Marco Marigo: 16, th divided by 2 50 Celsius degrees.
24:18:720Marco Marigo: and also in this case, 0 point 9 3 1.3 50 minus 20, that is equal to
24:31:470Marco Marigo: 36.3. What?
24:38:00Marco Marigo: 31.2 kilocalories per hour.
24:49:270Marco Marigo: Okay? I think we have to go to continue tomorrow. Right?
24:59:60Marco Marigo: Yeah, I need 10 min more. So I think that we can continue tomorrow, not not tomorrow. Sorry on Monday, Monday. Okay, so we will go on from this point on Monday we will finish this exercise, and then
25:12:990Marco Marigo: we will finish also the lecture.
25:31:930Marco Marigo: Exactly. So. I like to remember you that tomorrow there is the one. Is that okay, visit
25:45:220Marco Marigo: still valid the the possibility to have one additional point. If you come. This is the 1st point. The second point your colleague has gently
25:55:740Marco Marigo: offer the buildings. Okay, that you can select. So the ones of you who have not the buildings. Okay, not today. But Monday, okay? Or even today. You can send me. Okay, no. Make a list of
26:16:460Marco Marigo: who of you? Okay, don't write separate email. I just need the the list of people who need the the, let's say, virtual meeting offered by your colleague. Okay? Who are living in a dollar?
26:34:90Marco Marigo: Right?
26:38:480Marco Marigo: Oh, okay, on the shamanic report.
26:43:397Marco Marigo: Yes, but you cannot do the the same room repeated, because then the load is everywhere the same.
26:52:648Marco Marigo: Just assuming the the house.
27:02:660Marco Marigo: Yes, but I have to check it.
27:04:970Marco Marigo: Yes, you can do. If you have already assumed some kind of house. Okay, we can do that. But I have to check it.
27:11:880Marco Marigo: Okay, alright. So please, okay, make the list.
27:18:140Marco Marigo: Okay of people who need the the, okay? So that with the list, I can say, building, one, building, 2, building 3 building. Okay, don't send me separate emails.
27:30:940Marco Marigo: Okay? If you send me separate emails, then you have 3 points less. Okay? So your maximum both will be 27. Okay?
27:42:350Marco Marigo: Right? Okay. If you don't know each other, it's time that you know each other. Okay, right? Everything clear.
27:50:410Marco Marigo: You understand?
27:51:850Marco Marigo: Okay? Good.
27:57:390Marco Marigo: Like, judgment will show often.
28:01:440Marco Marigo: No, no, I have no idea at all.
28:08:860Marco Marigo: Is there any? Oh, Monica, do you know anything? No.
28:15:940Marco Marigo: okay, I will let you know. Okay, all right
28:23:767Marco Marigo: to be exactly there. So if you if you are later, some- Okay, don't worry.