Assistente AI
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00:00:00Michele De Carli: Okay, so we can start.
00:05:430Michele De Carli: Alright, so we were here last time, okay? We have seen how to…
00:11:810Michele De Carli: We have seen… sorry, we have seen… yes, yes, so we have seen what happens if we increase the air… the flow rate, okay? So…
00:27:600Michele De Carli: In this day, we have seen that, by, in, in, cooling, in conditions, when we supply air, they, dehumidify and cool the air, okay, have it there. We, of course, we, on one hand, we have to spend,
00:46:110Michele De Carli: or we need to provide power to the, to the chiller, sorry, to the cooling coil, which has to be, let's say, considered for the chiller. On the other side, we have an effect, a cooling effect.
01:02:420Michele De Carli: on, the room, on the building, okay? Now, we have seen that if we have
01:09:500Michele De Carli: 0.501 air changes power. The, cooling, the cooling,
01:18:470Michele De Carli: load, which can be, let's say, given by the ventilation system, could provide up to, let's say, 10 watts per square meter in this case, okay? So when we divide the power by the floor area, we have the clean load, okay, which can be provided.
01:38:690Michele De Carli: In, I mean, for a dwelling, we could consider, okay, we see that when you make the calculation for your house, okay.
01:49:930Michele De Carli: The cooling demand would be roughly, okay, 30 watts per square meter, so that means that one air change is… sorry, one air change per hour is not sufficient.
02:03:550Michele De Carli: So if we need… if with 1A change per hour, we need… we might have 10 watts per square meter. If we need 30 watts per square meter.
02:14:500Michele De Carli: we… it means that you need 3 air change rates, okay? Easy, okay? So, let's suppose that, then, the granule needs 30 watts per square meter, and as a matter of fact, okay, by considering the
02:33:570Michele De Carli: the… this, this power, okay, which has to be provided by the building, sorry, which is needed by the building, okay. Then, okay, so we assume to have this…
02:47:170Michele De Carli: Specific load, okay? And that means that, overall, it's roughly.
02:53:320Michele De Carli: 3 kilowatts, sensible load, okay? Then, if we… what you should do, okay, is to estimate the flow rate that you need, okay, to
03:07:700Michele De Carli: In order to, let's say, provide these 3 kilowatts of cooling.
03:14:80Michele De Carli: In the room, okay? In the building.
03:16:800Michele De Carli: you know that the maximum delta T is 10 degrees C, okay? So, in that case, you calculate the…
03:26:40Michele De Carli: muscle rate that is needed, which is 0.29, okay, kilograms per second. And…
03:35:170Michele De Carli: Okay, this is,
03:38:160Michele De Carli: This is to… and if you want to look at the volumetric flow rate, or the air changes per hour, okay, then this
03:47:110Michele De Carli: Master flow rate, okay, leads to three air changes. Okay, so we have seen how to get there in two ways, okay? So this is the usual way you should do the calculation, okay? And this was, let's say… okay, let's… don't think about it.
04:03:620Michele De Carli: So…
04:05:170Michele De Carli: we assume to need 30 watts per square meter. That means that you need 3 air change rates, okay? So, how can we do it? Okay, so, in the room, we need… we don't have it here, but if we… if we want to cool the room by the… by…
04:24:970Michele De Carli: by means of air, okay? It's called a full air system, okay? So in that case, we need to provide this volumetric fluorate in the room, in the building, okay?
04:40:990Michele De Carli: So we have two options, okay? One is to, have, one is to have,
04:48:610Michele De Carli: One is to have, the, all fresh air, so we will… one option is to provide directly 0.29.
04:59:990Michele De Carli: kilograms per second, okay?
05:03:560Michele De Carli: Meaning that we need to… Yes, we need to provide All the,
05:12:310Michele De Carli: enthalpy difference, okay, from outer condition to the, let's say, inlet condition at 16 degrees, okay? This is the delta
05:23:630Michele De Carli: in enthalpy, which, specific entropy, which we have seen last time, okay? So in that case, okay, we, it means that, this, enthalpy, specific enthalpy change.
05:39:540Michele De Carli: Times, of course, the master rate leads to 9 kilowatts of power.
05:45:640Michele De Carli: cooling, okay, which is needed by the cooling guy, okay? So.
05:51:710Michele De Carli: What I want to say is that we need 3 kilos for the cooling demand in the room, okay? What we calculate with the Ashram method. Sorry.
06:04:20Michele De Carli: with the Carrie method, okay. And, and in order to get this cooling demand. Bye!
06:16:310Michele De Carli: or air system, you need 9 kilowatts, okay, so 3 times the power.
06:21:270Michele De Carli: for the cooling coil. Of course, in this case, you are also… you are including also the La Pentro, okay, which is not included in these 3 kilowatts, which was just the… the sizeable…
06:36:820Michele De Carli: What happens if you have a heat recovery unit, okay? So, in the case of heat recovery unit, we said that we could assume to have 75%, so with the heat recovery unit of
06:49:210Michele De Carli: I didn't mention that here, but we assume to have, as we have seen in the case… in the calculations that we have seen last week.
06:57:120Michele De Carli: 75% of efficiency, okay? So, it means that, we have just sensible, just sensible
07:06:700Michele De Carli: heat recovery, okay? So it means that the outer air, okay, will cool down, but you have no dehydification, okay, because you have, on one hand, outer air at 34 degrees, and on the other hand, you have
07:21:750Michele De Carli: here, okay, at 26 degrees. So, you can cover 75% of this delta T of about 8 degrees C, okay?
07:34:750Michele De Carli: Which means that the, after the heat recovery unit, the outer air enters at 29… 28, what is this? Okay, 28 degrees C, with a sales humidity ratio, because in this case, the cooling is just sensitive. Okay, so the pink line is representing
07:54:590Michele De Carli: the sensible, effective, a sensible cooling, free cooling effect that we have with the electric company here.
08:02:60Michele De Carli: Okay? So, in that phase.
08:05:380Michele De Carli: We have a drop, okay, of about, let's say, 6 kilojoules per kilogram, okay, of, of air, which means
08:19:590Michele De Carli: Okay.
08:22:610Michele De Carli: We'll cancel it.
08:23:980Michele De Carli: Which means 6% 63, this is 63.
08:28:970Michele De Carli: Yep, okay, 63? Okay.
08:32:289Michele De Carli: 63, okay. So 63 minus 40… 39, okay, this is the cooling.
08:39:370Michele De Carli: power, okay, which means 7 kilowatts, okay? So, the heat recovery limit is
08:45:460Michele De Carli: Able to, let's say, save 2 kilos, so we're…
08:50:240Michele De Carli: 9 cables, okay? It's not that much, but it's okay, it's fine, it's serious.
08:56:730Michele De Carli: So this is one option, okay? So this is the option to bring the outer air and all these three air changes per hour, then we supply them into them. Of course, in this case.
09:10:970Michele De Carli: We are, let's say, considering all the outer air entering, okay? Of course, you need to cool and amplify this air.
09:20:680Michele De Carli: But in principle, we might not need all this,
09:25:580Michele De Carli: air as fresh air, okay? But we could, in principle, okay, just consider an air change rate of one
09:34:600Michele De Carli: of one, okay? We could… we are in a residential. We are in a residential building, okay, so that it means that we might even need half of the urgent rate, okay? But let's consider one urgent rate, okay? So, in this case, what you could do, you could then use
09:53:600Michele De Carli: the… Okay, I will do that.
09:57:930Michele De Carli: the sketch here.
10:00:690Michele De Carli: pain.
10:04:410Michele De Carli: Okay?
10:06:180Michele De Carli: I think we are clearing this.
10:11:870Michele De Carli: Just a minute.
10:15:320Michele De Carli: Okay?
10:20:930Michele De Carli: Okay? So, what we are doing is, basically, we are…
10:27:780Michele De Carli: We are intaking one air change rate, okay, of fresh air out of air.
10:35:600Michele De Carli: And that means, okay, that we are going to exhaust also the same volumatic fluoride. So we are also, okay, this is exhaust.
10:47:330Michele De Carli: Also, one air change rate, okay?
10:54:20Michele De Carli: We have… We might have, or not, the heat recovery unit, okay.
11:01:880Michele De Carli: Okay, so there are these two fluxes.
11:05:530Michele De Carli: Okay, exchanging heat, okay. And then, okay, we have… Since we are supplying.
11:17:100Michele De Carli: Three air change rates, okay, we, we can, okay, recirculate 2 air change rates.
11:24:490Michele De Carli: Alright? So, basically, what we do, we have…
11:29:290Michele De Carli: Of course, we are also, in the return, okay, we have 3… Here.
11:36:210Michele De Carli: change rates. Okay, so we are…
11:40:710Michele De Carli: Supplying 3 air change rates, okay, three, air change rates in the room.
11:48:730Michele De Carli: Two of them will be recirculated with the fresh air coming from outside, and one air change rate will be exhausted outside. Okay, so this is what we do.
11:59:840Michele De Carli: So, from… on the… on… if we have not the heat recovery unit, okay, so in case we are just mixing up outer air, one air change rate of outer air with two air change rates, so…
12:13:750Michele De Carli: email there. Okay, but, you know, like, the… the… This isolation, okay?
12:22:130Michele De Carli: ease,
12:23:790Michele De Carli: In, is on the, segment, okay, connecting the outer air and the indoor air. And the, resulting point, since it's… we are recirculating to
12:38:90Michele De Carli: The change rates and… so it's two-thirds of this segment, so this is the out.
12:43:550Michele De Carli: our bread, okay? So, in that case, we will, okay, have more or less 56, okay, kilojoules per kilogram of
12:56:350Michele De Carli: Air, okay? So in that case, okay, we will, of course, save, okay?
13:03:220Michele De Carli: Power on the… Holy God, okay? So, in that case, Who is you?
13:13:450Michele De Carli: Okay, so in that case, okay, we have, okay.
13:19:850Michele De Carli: As a result, okay, 5.7 kilos, okay, which is less than
13:27:580Michele De Carli: What we get here, or similar, let's say, okay.
13:32:190Michele De Carli: If we also consider a heat recovery unit, like I did here, okay, then the resulting
13:40:480Michele De Carli: The resulting, the resulting, transformation, okay, is…
13:48:490Michele De Carli: One air change rate, okay? Fresh air is, of course, we have one air change rate of outdoor air with one air change rate of exhaust air, so it's the same transformation, okay, as we have seen before, as we have seen here.
14:07:950Michele De Carli: But in this case, it's gone.
14:10:580Michele De Carli: The exchange rate instead of 3, okay?
14:13:560Michele De Carli: And now… The… Fresh air.
14:18:430Michele De Carli: Mixes up with the recirculating air, so the segment is this, and again, as in the previous transformation, we are
14:27:230Michele De Carli: In this point, okay? At 2 thirds distance from here, or one-third distance from here.
14:32:400Michele De Carli: Okay.
14:33:490Michele De Carli: And in that case, we have 54, okay, exchange rates that we can enter in, so we have even further reduced the entropy, okay, difference
14:47:440Michele De Carli: that we had before, okay? And in that case, the power is Okay, is 4.6, okay.
14:58:960Michele De Carli: Which is, I mean, not that far from the 3 kilowatts that we need just for the sensible load.
15:07:30Michele De Carli: Okay?
15:09:480Michele De Carli: So this is, okay, one possibility, okay, to, let's say, cool the building, okay? So this is…
15:19:500Michele De Carli: This is the, the basics, okay, the philosophy of the full air systems, okay? So, full air systems, depending on the
15:29:970Michele De Carli: amount of fresh air that you need, and the overall air that you need to provide to the room, okay, you can either circulate or not. Imagine that
15:40:220Michele De Carli: For instance, we have a roof where we need 3 or 4 air changes per hour, okay, then we will use just pressure, we will have no recipulation.
15:52:970Michele De Carli: Means that we need a big amount of power?
15:58:200Michele De Carli: energy at the end.
16:00:10Michele De Carli: But you cannot avoid it, because you need
16:03:60Michele De Carli: air quality in the room, okay? So if you need to supply 3 or 4 air change rates, no way, okay?
16:10:850Michele De Carli: So, you need to, you, you use a TV system, okay?
16:19:430Michele De Carli: Okay, so this is… so what I wanted from this example was to
16:25:380Michele De Carli: Make you understand what is the basic philosophy of the Twitter system, because we are going to see
16:31:880Michele De Carli: next week, okay, that's for your sister. And, on the other side, I wanted…
16:40:80Michele De Carli: I want you to understand, okay.
16:43:520Michele De Carli: the different concept of, or let's say, to split the power between the air handling unit and the cooling load. Okay, so one hand, the lap vent load, and the other hand, the susceptible load. Okay,
17:01:470Michele De Carli: As you should do in this case, in case of a mix, okay, a primary air of a mixed water and air.
17:09:270Michele De Carli: system, okay? Good. Now, to, to, to conclude…
17:17:89Michele De Carli: Let's see also what we could expect to have for, in winter, okay? So, what happens if… now, what… let's suppose that we use a fuller system, as we have seen for some, okay? Now, in winter, okay.
17:37:650Michele De Carli: What happens if we want to use a fuel system for heating the buildings.
17:44:80Michele De Carli: Here we have, let's say, I just, I just, I just introduced two different, okay, power of the building. Okay, the first one is 40W, which is a pure, poorly insulated building, okay? You can see, based on the calculation that we did.
18:03:980Michele De Carli: What these four keywords mean, okay?
18:07:470Michele De Carli: And, various rapid beating, okay, where you have 1 kilowatt of transmission loss, okay?
18:17:440Michele De Carli: So let's start with the first one, with the first, with the first type. And we won't delete these buildings just with the
18:26:100Michele De Carli: With a full air system, okay? So, what I want to see now is, let's say, the power that is needed on the heating coil, okay?
18:36:910Michele De Carli: Similarly, all, to what we have seen for the…
18:41:570Michele De Carli: cooling case, okay? So in the cooling case, what we have seen was to check which were the powers
18:48:40Michele De Carli: Required by the… by the cooling coil for the different options that we have, okay.
18:54:110Michele De Carli: Now I want to do the same, okay, exercise in winter condition, with two different buildings, one poor inspected building, and one
19:03:740Michele De Carli: Well, it's not a complete, okay? So… Yeah, so…
19:11:710Michele De Carli: Let's consider first the polity. Okay, so politically means 4 kilowatts of power, okay? Completion.
19:21:910Michele De Carli: So, if we, in winter, as you will see.
19:28:850Michele De Carli: We have, no really,
19:35:460Michele De Carli: we have no, really, temperature… I mean, there is not a bigger extrusion on the
19:43:240Michele De Carli: level of temperature that you can get in entering the room, okay, as you had in cooling, because in cooling, you need to avoid the condensation. In winter, okay, in principle, you're free to
19:56:630Michele De Carli: To keep the temperature that you want. But of course, the higher the temperature that you supply in the room, the higher the stratification problem that you buy.
20:05:820Michele De Carli: Okay, so usually it is recommended not to exceed 35, 40 degrees for the entering time.
20:12:800Michele De Carli: temperature of the air, or the temperature of the entire year. So I, I just fixed 40 degrees, which is, let's say, a reasonable temperature in order to avoid, too, big stratification, okay, in the
20:28:400Michele De Carli: Of course, we could even lower this, okay, but I just fixed it at 40 degrees.
20:33:520Michele De Carli: So, we fixed this temperature, okay, and we would like to see
20:40:510Michele De Carli: Similarly to what we have done in the… in the heating case… in the cooling case, okay? We want to check which is the…
20:49:40Michele De Carli: master rate that we need to provide to the room in order, okay, to… to satisfy these four…
20:55:780Michele De Carli: 1,000 watts, okay, for kilowatts of transmission losses, with entering air at 40 degrees, okay? So, the, the equation is the same, of course, yes, okay. In this case, okay, since we are, yes, in this case, we consider
21:15:100Michele De Carli: So if we consider this 40 degrees C entering in the room, and 20% indoor air, then, okay, we have 0.18175 kilohertz per second.
21:30:40Michele De Carli: This flow rate, okay, in terms of air change rates, is, let's say, 1.8, okay, so…
21:40:380Michele De Carli: Slightly more than half of the airflow rate that we needed in winter, in summer condition, okay?
21:49:320Michele De Carli: Now, if, if I want to provide this
21:58:260Michele De Carli: effer rate in the room, okay.
22:01:270Michele De Carli: And if I use… Just outer air, just fresh air, outer condition, design condition, minus 5, okay?
22:11:770Michele De Carli: I need to heat up the air from minus 5 degrees to 40 degrees, okay, when… because we have to enter this
22:19:510Michele De Carli: the air at this temperature. So that means…
22:23:730Michele De Carli: Okay, 8 kilowatts of power for heating, okay?
22:29:610Michele De Carli: So, it means that the cooling color needs to be sized for 8 kilos, and I need to size the generation system, okay, for 8 kilos to provide the
22:40:510Michele De Carli: the heating.
22:42:720Michele De Carli: Okay? The heating power for the beating, okay?
22:49:450Michele De Carli: Now, what happens, of course, we are going to see what happens in case of a heat recovery unit, but let's say we will see that later.
22:57:30Michele De Carli: Now, what happens if I have just one kilo? So, imagine that I have a very well insulated building, okay? A new building, okay?
23:06:520Michele De Carli: The new building, then, okay,
23:12:130Michele De Carli: In a new building, okay, there is…
23:18:90Michele De Carli: let's say, not… it is not a problem on fixing the temperature, okay, but it's just a question on how much air per rate I need… I want, okay? So, if I use one air change rate, okay, of…
23:33:940Michele De Carli: For the ventilation, okay, which means…
23:40:410Michele De Carli: 0.1, let's say, kilograms per second, okay, then I can calculate the supply temperature, which yeast?
23:50:610Michele De Carli: Okay? 31 degrees C. Okay, so it means that
23:54:720Michele De Carli: In all buildings, I have the one, if I wanted to use the full air systems, okay, I had, first of all, to, to supply air at a relatively high temperature, 40 degrees.
24:10:900Michele De Carli: and with high air change rates, okay, 3 air change rates. In an EBD, okay.
24:18:70Michele De Carli: Just with one air change rate, okay?
24:22:70Michele De Carli: I can, with a moderate temperature, okay, or low temperature, 31 degrees C, I can, okay, I can, I can satisfy the
24:35:40Michele De Carli: heating load, okay, the peak power for heating for the peak, okay?
24:43:100Michele De Carli: Okay, so… In the past, the Tarshal buildings were… Where many of them.
24:55:780Michele De Carli: could use the Fourier system, okay? So you can see that for tracing a power of 4 kilowatts, okay, we needed the double of the power, okay?
25:12:930Michele De Carli: Okay, so today you can see that the power needed in this case… Okay, sorry. The heating coil, okay, for covering the temperature gap between minus 5 and 31, and with this
25:31:40Michele De Carli: Limited.
25:32:920Michele De Carli: airflow rate, okay? In this case, we need just 3.5 kilowatts, okay? But, of course.
25:43:920Michele De Carli: Where… how can we further reduce this gap? Okay, by means of a heat recovery unit. Okay, so in this case.
25:53:620Michele De Carli: The heat recovery unit, okay, how does it work?
25:56:790Michele De Carli: We have indoor air at 20 degrees.
26:00:230Michele De Carli: We have outdoor air-5, okay? We said we can have an efficiency of 75%, Okay.
26:12:680Michele De Carli: Of the heat recovery unit, so it means that we can
26:17:860Michele De Carli: supply the air, okay, sorry, we can have at the outlet of the heat recovery unit, okay, before the heating power in this case, we have air at 13.5 14 degrees, okay? Sorry?
26:33:500Michele De Carli: Okay, and in that case, okay, we can see that the power for 3 change rates is,
26:44:190Michele De Carli: 4.6, and you can see that the power for
26:49:950Michele De Carli: for the… for value exchange rate is just 1.7 kilowatts, okay? Since that.
26:58:200Michele De Carli: to the power needed for the transmission use. Okay, also here, similar to this.
27:03:830Michele De Carli: Okay, so…
27:06:360Michele De Carli: This example shows you, okay, how the heat recovery units can play a big role in reducing the energy, the power.
27:17:110Michele De Carli: The size of the power system, and of course, all over the system, the energy demand, the energy consumption of the building, okay, when we need to provide, high ventilation flow rates, or when we want to use the full air system.
27:34:950Michele De Carli: Okay?
27:36:520Michele De Carli: Here, okay, so now you have seen, more or less the different transformation, okay? So we played a little bit with the figures. Okay, don't worry, because we come back to these points when we are going to see, and when you are going to see, okay, the
27:52:480Michele De Carli: the group project that you have to do in a few weeks, okay, on sizing a full air system, okay? So, we will let you know, but, I mean, in 3 weeks from now, okay, you will have the chance to work together in group, and to…
28:11:640Michele De Carli: and to science a fuller system, okay, and what you will do is basically this kind of exercise, okay, and you are going to, of course, then as first steps for the, for the science.
28:28:870Michele De Carli: So, that is what you could also understand based on this example, okay? Based on this example here.
28:38:770Michele De Carli: Well, for instance, okay, today, in small buildings, small residential buildings, or residential buildings, okay, there is, one possibility, okay, is to, or there are some,
28:57:50Michele De Carli: There are some, examples, okay, of,
29:01:370Michele De Carli: cooler systems, okay, for heating, the residential buildings, okay, because in that case, once you reduce the lot of the
29:13:640Michele De Carli: the heating power, okay? Then you could, in principle, work with a fuller system, okay, for heating the building.
29:22:680Michele De Carli: Of course, on the other side, this one air change rate might not be sufficient to cool the good thing, okay, because
29:33:810Michele De Carli: as we have seen, we need the 2-3 year changes, okay? Anyway, this is something that we are going to see,
29:44:80Michele De Carli: In the future, okay? So, what I wanted from this example was to show you, how, okay, to understand the figures that you might need, how important the envelope is.
30:00:160Michele De Carli: the cooling, the sensible cooling, what happens if you consider, then, the energy unit, what happens when you consider the cooling power on the coil, and so on, okay? And also, the effect of the heat recovery unit, both in winter and in summer, but particularly in winter, okay?
30:21:320Michele De Carli: Okay, so if you have no questions, Oops.
30:32:230Michele De Carli: Okay, we can go to the next point, to the next.