Transcript
00:08:39Michele De Carli: Alright. So we have seen yesterday. The what what happens
00:15:835Michele De Carli: or let's see what how you can manage the relative humidity in the 2, let's say different seasons. So we have seen the case study in
00:30:20Michele De Carli: in winter. Basically, we have seen that due to the low humidity of the outer air by supplying outdoor air with a sufficient flow rate. Okay, with a sufficient ventilation rate, it is possible to limit the relative humidity, let's say
00:53:720Michele De Carli: to 1450% of value. And we have seen that basically summer, we have to dehumidify the air. And one of the possibilities is to install is to consider a
01:11:500Michele De Carli: is to consider and coil a cooling coil. Right before the air supply. Okay.
01:25:600Michele De Carli: or after the heat recovery unit in order to dehumidify and cool the air. And we have seen the the case of the possibility to let's say
01:39:550Michele De Carli: size, or to have a suitable cooling coil which allows to to get out from the cooling coil with a specific or humidity ratio of about 8.5 and a temperature of 16 degrees.
02:00:711Michele De Carli: Now, grams of vapor per kilograms of dry air. Okay. Now then, we have seen what what per, which are, let's say, the
02:13:930Michele De Carli: required power for cooling the air and humid, and they humidify the air. So we have seen that basically, if you want to cool half air change rate of about 300 cubic meter of volume of the air. Okay, which is more or less
02:36:140Michele De Carli: the the case study that we have considered. Okay, you need the 1.5 kilowatts of power for for the children, for the cooling machine. Where we have seen that basically 500 watts are necessary or will help or will provide
02:58:155Michele De Carli: sensible cooling for the building, for the room. Okay? And one kilowatts. So the difference between my 1.5 and 0 point 5, okay, is one kilowatt. This is the necessary power for the humidification for the let's say, basically the
03:20:550Michele De Carli: of course, if we double so if we increase
03:26:130Michele De Carli: the ventilation rate. So if we consider 1 1 air change rate in this case.
03:34:590Michele De Carli: Sorry in this case. We have, of course, the the double of the the power necessary to
03:45:860Michele De Carli: cool and humidified in here. So the chiller has, instead of 1.5 meets. Is, the is the 3 kilowatts. Okay?
03:56:730Michele De Carli: And of course, on the other side, we are able to. Let's say to face one kilowatt of cooling load from the building, which is more or less 10 watts per square. Okay? So you when you calculate the carrier the carrier when you use the carrier method. Okay?
04:19:720Michele De Carli: Then, in this case, either you don't consider at all the the ventilation the, the.
04:30:860Michele De Carli: the, the ventilation rate, or, if you know which is and then you work, let's say, on the on.
04:40:800Michele De Carli: on the siding. Okay?
04:44:320Michele De Carli: Which temperature is suitable to enter in the room. Okay, so
04:49:110Michele De Carli: as to get as reference, then the cooling load from the air, or instead, if you know already when or which is the level of temperature of the air entering the room, you can use in the equation that we have seen.
05:06:660Michele De Carli: and
05:08:640Michele De Carli: maybe 2 lectures ago. Okay, the ventilation rate. Okay, with the with the correspondent. So this 500 Watts, okay, will be included in the calculation of the carrier. Okay? So it's up to you if you want to.
05:27:930Michele De Carli: If you want to avoid this
05:31:180Michele De Carli: power at the beginning. Okay, when you write the equation. So you you don't consider the ventilation rate in case in case you don't know exactly which is the temperature, or in case you consider the effect of ventilation. Okay.
05:50:830Michele De Carli: then, this power is already included. Okay, in your calculations in the cooling.
05:58:720Michele De Carli: Okay, so in this case, okay, we have. So let's say.
06:09:620Michele De Carli: this slide. Okay, is representing. The, let's see what is necessary just for the
06:20:250Michele De Carli: fresh air. Okay, so that is, these are 2 possible cases. Okay?
06:29:110Michele De Carli: 2 potential cases of, let's say, a residential use.
06:36:20Michele De Carli: Okay with half air change rate, or like an office
06:40:910Michele De Carli: an office application. Okay? Where we have said that in an office, usually we can roughly estimate the ventilation rate as one air change rate. Okay, half a change rate for residential purposes. One air change rate for
06:57:270Michele De Carli: office purposes. Okay, so what we have estimated here is just what is necessary from the ventilation, from fresh air point of view. If we want to provide fresh and humidified.
07:11:630Michele De Carli: Of course the power which is suitable, or which can be provided by the fresh air could not be sufficient, because 5 or 10 watts per square meter is quite a low value of cooling demand of cooling load on the building.
07:29:260Michele De Carli: So usually in buildings you might need. From, let's say, 30 minimum, okay t060-70-8100 watts per square meter. Okay? And then we will see what this means in terms of types of
07:46:30Michele De Carli: terminal units that you can provide to the building to the room. Okay, in order to get this 30, 40, 5,100 Watts per kilometer. Okay? So usually, when we talk about cooling.
07:59:300Michele De Carli: we consider the cooling power divided by the flow rate. We have seen that in heating basically, we usually consider the power per cubic meter. So we consider the volume as reference. Usually when we talk about the cooling load, then we, the specific cooling load is usually expressed in terms of watts per meter in terms of flowing.
08:21:890Michele De Carli: So we in this case, then, we have
08:27:330Michele De Carli: this type of terminal unit. Okay, we have seen in yesterday. In this case, this is a a suitable condition in case we have air and water cooling. Okay, so we we handle the air.
08:42:720Michele De Carli: So with the air we consider we are limiting the relative ability. We can have some, let's say, help in the cooling load, but
08:52:270Michele De Carli: most of the cooling load is provided by the cabinet, which is water based that, I mean, are you
08:59:180Michele De Carli: okay? So inside the coils there is flowing water. That is then put down by the chiller, so the chiller will cool down the
09:09:280Michele De Carli: water for this terminal unit and for the cooling oil on the machine. Okay, on the ventilation machine.
09:19:40Michele De Carli: Now, what should we do if we would like to cool down the building? Okay, this building that we have considered just with air. Okay, imagine with the full air system. Okay. So in a case of full air system, what you have to do is to consider
09:39:800Michele De Carli: the power right that you might need. So imagine that you have
10:11:920Michele De Carli: just in there. And of course, one limiting values of your choice is represented by the supplier that you need to
10:41:890Michele De Carli: then what you do, you have to consider, or you have to calculate which is the mass flow rate that you need to move inside of the room. Okay, in order to meet the power, which is the let's say, 2,008
11:14:340Michele De Carli: and 2, and the room temperature.
11:17:610Michele De Carli: So you can see that in case you want to pull your your building with just air. So with full air system, you need more or less
11:28:30Michele De Carli: 0 0 point 29 kg per
11:50:900Michele De Carli: doesn't work.
12:25:470Michele De Carli: okay, so i i i'm not able to click on this idea.
12:51:700Michele De Carli: So let's check it. I can.
12:54:890Michele De Carli: If I'm able to continue.
13:31:880Michele De Carli: This is the power. Okay, that you?
13:35:820Michele De Carli: So this is 3 air change rates. Okay? So now, basically, there are 2 options. So you you need in the in the room. You need to move. Okay, 3 times the volume. Okay per hour. 3 times the volume that you are you have inside of the room.
13:52:420Michele De Carli: But the fresh air. Okay, is just part of it. Okay, so in this case.
14:02:169Michele De Carli: you have either you use. Let's imagine that you need the one air change rate. Okay, let's see the the first.st The 1st point is, you have all fresh air. So you want to use just fresh air. Okay, so these 3 air change rates. Okay.
14:24:850Michele De Carli: we coming from outside. You cool down them. Okay? So you have to face the overall enthalpy difference that we have seen yesterday. It is
14:36:700Michele De Carli: the the difference is, everything is stopped now. So okay. So the difference is between 69 and 37, kilojou per kilogram. Okay, in the 2, in the outer condition and in the inlet condition. Okay.
14:52:270Michele De Carli: so that means that if we want to cool down and to dehumidify these 3 year change rates that will lead to 9 kilowatts of power. Okay,
15:05:350Michele De Carli: So in that case, okay, imagine that you have like, you want to you, or you need to have provide just a share. Okay? So in that case, imagine that you have to. I mean the the power which is needed is not
15:23:830Michele De Carli: okay. So 9 kilowatts is the power wind power that you need to cool down. 3 air change rates of 300 cubic meter of volume. Okay? So which means 900 cubic meter per hour. Okay, of air flow rate. Okay, 3 times 300. Okay.
15:44:830Michele De Carli: of course.
15:46:350Michele De Carli: if you need to provide this amount of fresh air. Then you use a a fuller system. Okay? And and maybe but of course, that will lead to a greater power. Okay, required.
16:00:20Michele De Carli: Imagine that you instead, you would need one air change rate as fresh air. Okay, so what you do, basically.
16:09:840Michele De Carli: you mean in the room.
16:16:900Michele De Carli: You need to move precaur change rates. Okay? So that means that you have to supply
16:23:330Michele De Carli: 3 year change rates. Okay? And you have to
16:27:507Michele De Carli: to. You have to bring from the exhaust 3 exchange rates, but from outside you need one exchange rate.
16:38:240Michele De Carli: Hey, Cheryl, you don't need to use
16:41:700Michele De Carli: 3 air change rates as fresh air, because the renewal of air is just for 1 3.rd So what you do, you recirculate 2 air change rates. Okay.
16:58:194Michele De Carli: which will be at 26 degrees, and all more or less
17:05:520Michele De Carli: 50% of relative humidity instead of 34 degrees C, and
17:12:630Michele De Carli: 40%. Oh, God, at the beginning.
17:16:200Michele De Carli: Okay, so in this case.
17:18:730Michele De Carli: since you are recirculating the air, okay, and not able to go to the following the following slide, okay.
17:31:790Michele De Carli: maybe I can.
17:38:290Michele De Carli: It's impossible if anything is not. But if you go and see the slides in your in your your laptop, okay.
18:03:930Michele De Carli: because the amount, the flow rate is 2 times here than the fresh air that you are that you're bringing from outside. Okay? And in that case, okay, in the
18:35:600Michele De Carli: thank you.
18:37:120Michele De Carli: Yeah, try it, please, please.
18:40:170Michele De Carli: So now, the power that you need to cool down this, because then all this stuff
18:48:190Michele De Carli: here, you get 56.
18:54:730Michele De Carli: They know you are cooling down in the cool.
19:20:380Michele De Carli: You need 5.7 kilowatts of green.
19:25:250Michele De Carli: Okay, so this is the cooling load that is needed by the chipper. Okay.
19:33:270Michele De Carli: I want to just highlight that in case you want
19:41:522Michele De Carli: in case you need them. As we have seen before.
19:47:70Michele De Carli: We need you said 3 kilowatts more or less
19:55:840Michele De Carli: for for one air change rate.
20:02:640Michele De Carli: Okay, we had the 1.5 kilowatts right?
20:10:680Michele De Carli: Plus 1 45 kilowatts for one exchange rate in the previous slide.
20:16:690Michele De Carli: How much was it? 3, 3, 25. Okay, 3. Okay.
20:26:380Michele De Carli: So if we provide one air change rate with fresh air plus water based solution.
20:44:290Michele De Carli: In this case we need 3 kilowatts for cooling and dehumidifying the outer air. Okay.
20:55:40Michele De Carli: but we have a benefit
21:02:430Michele De Carli: or 500 or one kilowatt of one kilowatt of cooling for the sensible load.
21:11:70Michele De Carli: one kilowatt, right? So we have one, the benefit of one kilowatt.
21:15:630Michele De Carli: Okay?
21:17:360Michele De Carli: So that need that we need 3 kilowatts on board. So for the drink coil plus.
21:26:210Michele De Carli: we need to provide these 2.9 kilowatts with the
21:33:600Michele De Carli: the cooling load is 2.9.
21:37:250Michele De Carli: What that one kilowatt is given by the fresh air. Okay? So the water based solution
21:48:790Michele De Carli: is 2.9 minus one.
21:52:20Michele De Carli: Okay, which is not 1.9
22:14:840Michele De Carli: 5 7 with full air system.
22:19:860Michele De Carli: Okay, so what is the message? So what
22:43:130Michele De Carli: more efficient than the fuller system?
22:47:730Michele De Carli: Okay, of course, if you need a high ventilation rate in a building. Then you
23:13:810Michele De Carli: high air rate. The the ventilation flow rate for fresh air
23:19:750Michele De Carli: is small compared to the power that we need for cooling
23:25:10Michele De Carli: the air and water, the combined air and water, mixed air and water solution.
23:47:750Michele De Carli: Oh, it's it's less than yes, 4.9. Yes, sure.
23:51:630Michele De Carli: Another pricing.
23:54:200Michele De Carli: Is there any analytical way to define the energy of point 0 of the reciprocal?
24:17:20Michele De Carli: And you can you can insert the the equations
24:25:466Michele De Carli: correlating the temperature with the saturation pressure. Then, based on the vapor, the partial pressure you can get.
24:47:870Michele De Carli: Okay, okay, you? Of course, I'm not able, because everything is blocked now. But I mean, we you work with the on the on the carrier chart. Okay, on the psychometric chart. But what you do in the psychometric chart could be implemented in an excel file. Okay? Or I don't know in a Matlab or python. Okay?
25:11:220Michele De Carli: More familiar if you like, then. But you can simply work in an Excel file.
25:17:450Michele De Carli: and what you get is perfect result
25:21:470Michele De Carli: better than working with the diagram. But of course the diagram is quite
25:25:810Michele De Carli: quick and simple. But once you implement the questions in an excel file, then you just change a little bit and everything is
25:34:330Michele De Carli: fine.
25:39:330Michele De Carli: Okay.
25:41:530Michele De Carli: I think it was the last slide. I'm not able to look at the to follow, because my PC is completely
25:52:310Michele De Carli: blocked. Okay? So what I want you to make is 5
26:19:560Michele De Carli: into technologies and see which are the, let's say, the how to proceed with the sizing and looking at the Hvac system. We look at the other. Let's say, power that is needed power and energy which is required by the building. Okay, which is the sanitary hot water
26:42:670Michele De Carli: that
26:58:850Michele De Carli: we are going to work more and more with the heat pumps. Okay, is also to how to
27:07:824Michele De Carli: combine the heat pump with a water tank. Okay, in order to. Let's say, store.
27:29:240Michele De Carli: we will see the fuller system and automation. So we go more into the technology.
27:38:50Michele De Carli: Okay, just a minute