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00:05:130Jacopo Vivian: Yeah.
00:09:420Jacopo Vivian: everything is fine. Now you can see
00:12:890Jacopo Vivian: I'm recording. You have the slides, so I can start
00:19:450Jacopo Vivian: good. So what are we talking about in the next
00:25:460Jacopo Vivian: 3 today and 3 lectures. We are talking about the hydronic systems.
00:31:940Jacopo Vivian: So what are hydronic systems like the radiant systems that you have. Just see, they are
00:41:80Jacopo Vivian: systems. They are distribution system of the Hvac system that use water as heat carrier fluid.
00:49:840Jacopo Vivian: Okay?
00:52:90Jacopo Vivian: Of course, in case of radiant systems. This is not a distribute part of the distribution, but it's part of the
01:04:489Jacopo Vivian: hit, the emission exactly. So. You know that there is
01:10:450Jacopo Vivian: in a in every H box system. You have
01:15:230Jacopo Vivian: the emission. So we start from the building envelope with the ventilation. So the energy needs of the building. Okay? And then we start looking at hbo systems from the closest component, which is the heat emission system, like terminal units of different systems.
01:37:340Jacopo Vivian: And then we have the distribution.
01:41:390Jacopo Vivian: Okay? So which connects the generation units to the heat emission. So now we are talking about something in the middle, between the generation and the heat emission.
01:52:990Jacopo Vivian: When this heat distribution is done with water, we call, we call it hydraulic system.
02:00:970Jacopo Vivian: Since water at ambient temperature and pressure, it's an incompressible fluids. We can assume that we can use the Bernoulli's principle, as you know, from the physics.
02:21:40Jacopo Vivian: So we know that the pressure the pressure drop along a circuit can be calculated with this formula here.
02:34:120Jacopo Vivian: So where we have where we had the.
02:43:730Jacopo Vivian: that's we have some
02:51:440Jacopo Vivian: continuous pressure losses.
02:54:430Jacopo Vivian: Okay? And some concentrated pressure losses and the Delta P depends on the square of the of the flow.
03:03:580Jacopo Vivian: The flow rate is normally expressed in, for example, cubic meters per hour or liter per second, okay, or liters per hour, depending on the size.
03:16:170Jacopo Vivian: and therefore from the volumetric flow rate, you can calculate the velocity by knowing the the cross surface area is crossed or the other way around. So if you have the velocity, you can calculate by knowing the diameter of a certain type, you can calculate the area and therefore the flow rate.
03:41:890Jacopo Vivian: Okay?
03:43:550Jacopo Vivian: So I mean.
03:55:100Jacopo Vivian: so what is if we replace the the ratio between flow rate and surface area. In the velocity
04:08:670Jacopo Vivian: we can express the Delta P as
04:15:210Jacopo Vivian: the square of the flow rate times. This sums with all the all these terms here, and this is called hydraulic resistance.
04:28:860Jacopo Vivian: So, as you can see, this is not a linear flow, so it's not like
04:38:80Jacopo Vivian: For example, in the electrical analogy we have that the Delta V is equal to the electrical resistance times the intensity, the current intensity. In this case the law is not linear for hydronic circuit. It is a quadratic low.
04:57:420Jacopo Vivian: so the the Delta P,
05:00:130Jacopo Vivian: which would be similar to the Delta V in the electrical analogy, is the the product of the hydraulic resistance times the square of the flow.
05:13:790Jacopo Vivian: Right?
05:14:830Jacopo Vivian: Okay?
05:16:830Jacopo Vivian: Yes.
05:28:40Jacopo Vivian: It's okay. Yes. Okay.
05:31:670Jacopo Vivian: I just replaced U is equal to qv, so the flow rate divided by S, okay, so
05:43:473Jacopo Vivian: we can express the pressure loss in secret by using this this log here
05:50:330Jacopo Vivian: and over a single element. You. You have this this law, as I told you, it's different from what you have in other
06:03:640Jacopo Vivian: physical phenomena, like the Joule effect where you have Delta V is equal to electrical resistance times the intensity of the current.
06:15:350Jacopo Vivian: So we need to start the thinking of secrets in this part of the course. Okay? So that's what I'm talking about in this course.
06:25:850Jacopo Vivian: because there are a lot of cases where you need to understand what's happening in Hvac systems in practice. So you need to think, okay, you see a lot of pipes. Okay, but
06:42:470Jacopo Vivian: what is the problem? Now, let's start to simplify things. If we have 2 secrets that are connected to each other, and we have. You can see, a common pipe connecting those 2 sequences.
07:01:910Jacopo Vivian: and we have the pump only in one of the circuits. We call it primary circuits, and then we will see why, later on, in the next lectures
07:14:320Jacopo Vivian: and the the second one, the one without the pump is, it will be, as you will see, the one connecting to the terminal units. We call it, secondary pipe.
07:27:80Jacopo Vivian: In this case, the how is the flow rate in such a case?
07:37:200Jacopo Vivian: Where where does the flow rate go? So we have the pump here.
07:43:10Jacopo Vivian: So we assume that here there is the circulation of the nominal flow of the pump, the circulation pump.
07:52:210Jacopo Vivian: and here, when it reaches a where does it go?
07:57:360Jacopo Vivian: It depends on the hydraulic resistance between A and B.
08:03:890Jacopo Vivian: If the hydraulic resistance between A and B is very low, all the flow will remain
08:12:740Jacopo Vivian: in the primary circuit.
08:14:890Jacopo Vivian: Okay.
08:16:260Jacopo Vivian: So, for example, if the length between A and B is very short, or if there is no valve, no anything that cause, and a delta P between A and B, all the flow will remain in the primary circuit.
08:37:809Jacopo Vivian: Of course there is always it. It always depends on what is in the secondary secret, but here we assume that
08:48:50Jacopo Vivian: there is a high resistance because there are
08:52:690Jacopo Vivian: terminal units. Okay? So if we have a significant hydraulic resistance in the secondary sequet. And here. We don't have a significant
09:05:530Jacopo Vivian: hydraulic resistance. Most of the flow will remain in the primary shift.
09:11:330Jacopo Vivian: Is the concept clear? Can I go on? Okay.
09:17:660Jacopo Vivian: what happens if we place a pump, another circulation pump in the secondary circuit.
09:27:790Jacopo Vivian: Okay? So if in the common section
09:32:560Jacopo Vivian: the the hydraulic resistance is very low, or, for example, if the length is very limited.
09:40:970Jacopo Vivian: there is no circulation in the secondary secret. We said that without the pump.
09:47:630Jacopo Vivian: but if we place a pump. Of course there will be circulation. And the basically, you will have
09:58:290Jacopo Vivian: the the sum of the of the flow rates.
10:05:40Jacopo Vivian: considering the flow in between A and B, okay.
10:10:270Jacopo Vivian: so you have a certain flow rate. Q. 2. Here, going in this direction and a certain flow rate. q. 1. Here.
10:20:670Jacopo Vivian: Okay, so you just need to make the mass flow the balance of the mass flow rate
10:29:00Jacopo Vivian: in A, and you will calculate the mass circulating between A and B.
10:35:250Jacopo Vivian: What happens if the pump? 2 stops?
10:40:580Jacopo Vivian: Okay.
10:46:530Jacopo Vivian: we come back to the 1st situation. And of course, also, if the pump one stops.
10:53:650Jacopo Vivian: But this is not a common situation, because normally, you have the generation units in the primary circuit and the terminal units in the secondary circuit. Yeah.
11:10:810Jacopo Vivian: like, basically, this goes.
11:23:90Jacopo Vivian: Yes. So you have. Q 2 here circulating and the q 1 here.
11:31:340Jacopo Vivian: So, yeah, there are 7.
11:33:900Jacopo Vivian: They are separate. Yes, they are driven by their but their circulation pumps.
11:40:900Jacopo Vivian: So what happens here is just the result of the mass flow rate balance between the q. 1 and Q 2
11:49:820Jacopo Vivian: in the common pipe.
11:52:140Jacopo Vivian: Okay, yes, so it's a high number of 39 degrees really never required that. There is no way.
12:10:520Jacopo Vivian: Yes, but there there is also there is always a return. Yes, it's not an open loop. So
12:18:580Jacopo Vivian: and now and now we will see it. So it's just the the next topic. We see what how this sec. Especially secondary secret, are
12:32:880Jacopo Vivian: made. This the 1st type.
12:36:630Jacopo Vivian: So thanks for introducing the next topic is the 1 5 secret within series. Connection.
12:45:999Jacopo Vivian: This is not very usual layout, because, although we have some advantage, like, we have limited installation costs
12:59:170Jacopo Vivian: and simple sizing, we have some drawbacks.
13:06:300Jacopo Vivian: What are the drawbacks.
13:09:520Jacopo Vivian: 1st of all, the supply temperature decreases with the distance from the generation units.
13:17:340Jacopo Vivian: So of course, if you have
13:23:310Jacopo Vivian: 55 degrees outside the generation unit assume you have a radiator here the
13:33:850Jacopo Vivian: the outlet temperature of the 1st radiator. It will not be
13:39:190Jacopo Vivian: 55 degrees because it has released some heat to the environment.
13:45:410Jacopo Vivian: And so the temperature of the heat carrier fluid of the water circulation circulating in the system is lower.
13:55:40Jacopo Vivian: Therefore this in the second radiator, you will have something lower, say 50 degrees.
14:02:810Jacopo Vivian: and in the in the 3rd you will have a 45, and so on. So what happens is that in the with this layout you have the
14:18:610Jacopo Vivian: the farthest radiator or terminal units, because we don't always have radiators having lower
14:28:430Jacopo Vivian: supply temperature, and therefore also lower heat flow rate. Given the same size. Okay, imagine they are all the radiators of the same size with an E series connection.
14:42:160Jacopo Vivian: the latest, the one that is most far away from the generation does not, is not able to deliver the same amount of heat as the 1st one, because it receives a flow rate with a lower supply temperature.
15:00:990Jacopo Vivian: Also there is another issue.
15:03:830Jacopo Vivian: Which is it that heat meters with high flow resistance
15:11:280Jacopo Vivian: can limit the total heat output
15:16:980Jacopo Vivian: you. You can see that in other, you can say, in other words, imagine you have a problem in the 1st radiator.
15:26:560Jacopo Vivian: Okay, you have an obstruction. So with a very high hydraulic resistance that will prevent a high circulation of flow in a radiator one.
15:41:520Jacopo Vivian: This means that also all the other radiators will receive a lower flow rate.
15:47:720Jacopo Vivian: So you have also this problem here. Okay, the problem of reliability. Because if you have the damage in the 1st heat emission system. Then you have a problem also in the next one, because they they are in series.
16:04:870Jacopo Vivian: And then you have not the Po, the possibility to individually control the the heat flow.
16:17:900Jacopo Vivian: Why? Because if I close the flow rate the 1st one, it will also.
16:24:779Jacopo Vivian: There will be no flow circulation in the second one.
16:29:570Jacopo Vivian: And typically, we have a terminal units in different
16:35:440Jacopo Vivian: rooms in different parts of the same building that have different heat demand.
16:43:290Jacopo Vivian: So you can imagine a room which is exposed to the south, which receives heat from the sun.
16:51:40Jacopo Vivian: It has a high high temperature inside, and then you have imagine you are in school, and then you have a room which is exposed to the north that never receives the sun.
17:06:800Jacopo Vivian: Okay.
17:08:300Jacopo Vivian: these 2 rooms with the children inside have very different situations in terms of thermal comfort. So you always want to guarantee controllability, individual control for different thermal zones. Okay?
17:24:859Jacopo Vivian: So in this case we can't, we cannot have it.
17:33:10Jacopo Vivian: Okay.
17:35:990Jacopo Vivian: And last, but not least, you have noise.
17:40:380Jacopo Vivian: because, you have that. All the flow goes in all the terminal units.
17:47:630Jacopo Vivian: You know that the higher the flow, the higher the velocity, and the higher the velocity, the higher the noise.
17:55:240Jacopo Vivian: Okay, therefore, you have also this problem. So all of these to say, this layout is not very common.
18:05:700Jacopo Vivian: so we have an option to have a 1 pipe circuit within parallel connection. What does it mean?
18:14:250Jacopo Vivian: It means that although we don't have a supply pipe and the return pipe, they are still in series.
18:25:390Jacopo Vivian: But there is a bypass for each terminal unit.
18:31:610Jacopo Vivian: So you see.
18:34:290Jacopo Vivian: for example, this is, assume, this is a radiator. You have the flow to the radiator, and then it's in series with the next one, you see.
18:45:820Jacopo Vivian: but both of them all the 3 of them have a bypass, which means that the
18:55:60Jacopo Vivian: we still have limited cost, because we don't have an entire supply and return line. We only have one pipe circuit so still limited cost.
19:07:930Jacopo Vivian: But, you you don't have the problems we had before.
19:14:530Jacopo Vivian: You also have lower pressure overall pressure drop, because if most of the flow does not go in the radiator, it will also not decrease the pressure as much.
19:29:280Jacopo Vivian: Okay. So it is better than the situation we had before, plus, we have the possibility of individual flow control
19:40:180Jacopo Vivian: because we can choose how much flow giving to be given to each terminal unit.
19:49:890Jacopo Vivian: we still have the problem of decreasing the supply temperature to the next radiators
19:57:770Jacopo Vivian: or to the next terminal units, because, even if not all of the flow will go in the radiator. Still, you have mixing here between the flow that is not entered the 1st radiator and the return of the 1st radiator. So you still have the problem, although it is not as big as in the previous situation. Okay? Because you have this mixing.
20:26:660Jacopo Vivian: And then so here you can see.
20:34:260Jacopo Vivian: This is a typical situation. So we have one pipe seal with with the bypasser.
20:43:340Jacopo Vivian: So with the in parallel connection. And this is a situation where you have radiators, for example.
20:52:700Jacopo Vivian: with these valves they are called divertities, which are simply fittings that are designed to divert the flow, a portion of the flow
21:05:870Jacopo Vivian: to the terminal unit.
21:08:811Jacopo Vivian: So normally it is fine to place only one diverter T. You can place it either on the on the flow, on the supply here, or on the return, as you can see here.
21:27:160Jacopo Vivian: To to connect terminal units with this inferral connection.
21:36:540Jacopo Vivian: And then there should be something that regulates the the flow. Okay.
21:44:220Jacopo Vivian: which is a thermostatic valve that you can see here. So basically, the thermostatic valve is opening and closing. So it's changing the hydraulic resistance inside here. Okay, according to the temperature of the indoor environment.
22:04:190Jacopo Vivian: Okay, so there is a bulb here which expands with the environmental temperature.
22:11:920Jacopo Vivian: and as long as it expands it obstructed the flow in the in this yellow valve here.
22:20:500Jacopo Vivian: So
22:22:970Jacopo Vivian: the, this is the individual flow control that I was speaking about. Okay, now you can have it with the one pipe circuit within parallel connection.
22:38:208Jacopo Vivian: A single diverter t is usually sufficient to create the flow through the low resistance. Heat emitters like a radiator.
22:52:232Jacopo Vivian: Assuming that the heat meter is above the piping loop containing the diverted T, okay.
23:02:170Jacopo Vivian: But in some cases it it is needed to place 2 diverties in order to divert the flow.
23:12:320Jacopo Vivian: so to create a greater pressure difference across the branch
23:19:520Jacopo Vivian: the higher the the pressure difference, the higher
23:26:420Jacopo Vivian: the the capacity to divert the flow. Because, as we said, if imagine.
23:34:520Jacopo Vivian: this is the primary secret we were speaking about before.
23:39:210Jacopo Vivian: and you can see that you can consider this heat emission system to be the secondary circuit.
23:47:880Jacopo Vivian: So that means, if there is no pressure difference between this point and this point.
23:54:910Jacopo Vivian: no flow will go to the radiator. Right?
23:58:450Jacopo Vivian: So the diver T is exactly meant for this to create a pressure difference between this point here and this point here.
24:10:100Jacopo Vivian: Otherwise no flow, no water will go in the radius.
24:15:830Jacopo Vivian: Okay? Because here the flow resistance is much lower than here.
24:25:460Jacopo Vivian: Okay, so this is an example of how this
24:31:120Jacopo Vivian: see if it would look like
24:37:141Jacopo Vivian: so all the terminal units are connected in parallel to a single pipe system. You see here.
24:48:680Jacopo Vivian: look at, look at the mouse.
24:51:850Jacopo Vivian: This is the single pipe. So you have a loop
24:56:750Jacopo Vivian: connecting all the units in parallel to the generation unit which is here. And you have the circulation pump here.
25:07:680Jacopo Vivian: Okay.
25:09:630Jacopo Vivian: so we have seen 2 layouts for the one pipe secret. And now we can see the other case with the typical case of a 2 pipe secret with direct return.
25:24:340Jacopo Vivian: Direct return means that so, 1st of all, what is the advantage?
25:31:810Jacopo Vivian: We have seen that with both layouts of the one pipe. Cfp, we have the problems of having lower supply temperature to the next to the last radiators.
25:46:10Jacopo Vivian: In this case we don't have this problem because all the radiators are supplied with the same supply temperature. There is no temperature drop between this point here, the flow
26:00:300Jacopo Vivian: coming from the generations. And this point here.
26:05:730Jacopo Vivian: Okay? Because there is no
26:10:40Jacopo Vivian: heat emission system. Between these 2 points.
26:13:270Jacopo Vivian: You only have the heat losses, but the heat losses are inevitable.
26:18:680Jacopo Vivian: They are unavoidable. Okay, so you can only insulate thermally, insulate the pipes to avoid
26:27:410Jacopo Vivian: losing temperature for the heat emission systems.
26:36:180Jacopo Vivian: And then the return of this radiator will mix in this point
26:43:860Jacopo Vivian: with the radiator, with the return of the second radiator.
26:48:130Jacopo Vivian: and both of them will mix with the return of the 3rd radiator, and so on.
26:55:390Jacopo Vivian: So here you see 2 different types of double pipe distribution with direct return.
27:03:170Jacopo Vivian: What is the difference between the 2?
27:05:990Jacopo Vivian: It is that in the 1st case, you have a vertical distribution.
27:15:220Jacopo Vivian: We call it the risers okay? Or in Italian colony, Montanti, montanti, or
27:25:520Jacopo Vivian: you can have an horizontal distribution. In this case you still have this
27:32:284Jacopo Vivian: direct return, but they all. They are all at the same on the same floor. Okay, in this case you have 2 risers.
27:43:60Jacopo Vivian: for example, connecting apartments that are in different
27:48:677Jacopo Vivian: in different floors. Okay. So that means that the same apartment could be supplied by these 2 risers
27:57:780Jacopo Vivian: imagine we have a okay. This is not the typical situation. We have more than 2 risers. But imagine we only have 2 risers.
28:06:640Jacopo Vivian: You have the apartment in the imagine. We have 3 floors
28:12:830Jacopo Vivian: and one apartment per floor, in the reality would be more apartments for each floor and more risers. But
28:20:290Jacopo Vivian: the principle is exactly the same. So you can imagine that here we have an apartment that is supplied by 2 risers
28:29:760Jacopo Vivian: and at the same con floor. You have an apart, another apartment supplied by the same tourizers.
28:38:20Jacopo Vivian: And what is the problem of this situation, which is very, very typical, you should know this
28:48:730Jacopo Vivian: pressure drops. Why.
28:54:980Jacopo Vivian: yes, yes, this is correct. So the up. The terminal units that are closer to the generation have a higher Delta P.
29:11:440Jacopo Vivian: But we are no more talking about Delta. P.
29:18:610Jacopo Vivian: No, the Delta T is not the problem, because we said that we have the same supply temperature. We assume the pipes are thermally insulated. Okay? Or that the Delta T, due to the heat losses is negligible. Now
29:33:853Jacopo Vivian: so the Delta P is not a problem. The Delta P could be a problem for which floor?
29:43:40Jacopo Vivian: For the for the last one? Exactly, because between this point, so the supply
29:52:272Jacopo Vivian: to the 1st radiator. And this point we have a lot of meters.
29:58:990Jacopo Vivian: Imagine we've had more floors.
30:01:660Jacopo Vivian: So all these meters are a pressure drop.
30:07:290Jacopo Vivian: And here, in order to have when when is when this would be a problem.
30:17:790Jacopo Vivian: when there is not enough delta P between the supply and the return. So between this point here. And this point here.
30:28:760Jacopo Vivian: Okay? Because
30:32:980Jacopo Vivian: And now I draw.
30:44:110Jacopo Vivian: Okay, this is another.
30:53:380Jacopo Vivian: So
31:00:580Jacopo Vivian: you have pressure here.
31:03:160Jacopo Vivian: Okay? And here you have the distance from the
31:08:927Jacopo Vivian: from the generations, from the pump, from the main pump of the system. Okay. So what you have is that close to the generation system. There is a pump which increase the pressure.
31:24:260Jacopo Vivian: Okay, in order for the flow to circulate and reach all the terminal units of the system.
31:31:530Jacopo Vivian: And then between, you have a certain pressure dropper until you reach
31:39:700Jacopo Vivian: until you reach. So imagine the pump is here. We have a certain pressure drop until we reach this point. Okay.
31:49:350Jacopo Vivian: so imagine we are here, then we have still a pressure drop
31:57:310Jacopo Vivian: to reach this point, and then another pressure drop to reach this point. So that means that
32:05:310Jacopo Vivian: here you have the radiator of the supplies of the radiator on the 1st floor. Then you have this one, and then you have this one.
32:18:110Jacopo Vivian: So now we are in this point. Here we reach the 3rd floor.
32:24:230Jacopo Vivian: What happens in the radiator?
32:26:940Jacopo Vivian: We have a pressure drop due to the pipes in the radiator. Okay, which is a localized pressure drop. It's not a continuous. This is a continuous pressure drop depending on the you know how to calculate continuous pressure losses, I guess.
32:44:700Jacopo Vivian: And then you have a pressure drop between this point. So the supply to the last radiator and the return of the last radiator. Okay, so we represent it as a pressure drop here.
32:59:90Jacopo Vivian: We don't change the distance because we are on the same regulator, and then you have
33:08:610Jacopo Vivian: the return align, which is a usually it is a a mirror
33:14:740Jacopo Vivian: of the of the supply line. If the diameter is the same. Of course the slope of this line depends on the diameters.
33:26:430Jacopo Vivian: because the big, because the flow would be the same.
33:30:100Jacopo Vivian: Okay for each section, the flow would be the same.
33:36:390Jacopo Vivian: So basically, the material of the pipe is the same between supply and return. What can change is the diameter if the diameter is the same? Typically, it should be the same, because it is designed for the same flow rate.
33:53:490Jacopo Vivian: This local of supply and return line should be the same until you reach the inlet to the circulation pump.
34:01:490Jacopo Vivian: So your colleague was correct. The problem of this
34:07:170Jacopo Vivian: layout is exactly the Delta P, which Delta P. Exactly this Delta P.
34:14:310Jacopo Vivian: So the Delta P.
34:17:199Jacopo Vivian: Between up there it seems. Forward.
34:22:389Jacopo Vivian: the Delta P. Between the supply and the return in the last terminal units.
34:28:260Jacopo Vivian: It's should be higher than a minimum.
34:32:870Jacopo Vivian: There's a PIN.
34:34:380Jacopo Vivian: This is for all closed loops.
34:39:520Jacopo Vivian: for all hydronics circuits with 2 pipes. Okay.
34:48:199Jacopo Vivian: Okay, is it clear? Or should I fleet.
35:02:750Jacopo Vivian: Yes, the absolute pressure should be the end of the
35:18:506Jacopo Vivian: the even important thing when you design closed loops is that you consider to have this Delta P
35:31:210Jacopo Vivian: and the Absolute. So this is a relative pressure difference. But you are asking about the absolute value of pressure in this point.
35:43:20Jacopo Vivian: Right?
35:44:911Jacopo Vivian: Yes, this should be considered
35:48:840Jacopo Vivian: in order to not to have cavitation in the pump.
35:55:850Jacopo Vivian: Okay?
35:57:520Jacopo Vivian: And and you will see in the next slide in one of the next lectures
36:08:280Jacopo Vivian: how to avoid having a low pressure at the inlet of the pump.
36:18:610Jacopo Vivian: Yeah, it's pressurized. But you need to commission the system. So you need to start when you start the system. You might have this problem
36:28:410Jacopo Vivian: if I have as a service for yes, yes.
36:34:970Jacopo Vivian: I need the 9, 8 7
36:38:780Jacopo Vivian: of water, the pressure drop along the path.
36:45:570Jacopo Vivian: Yes, otherwise you. The pump will not reach that point. Yes.
36:51:820Jacopo Vivian: yes, yes, yes, it's correct. So you need to have a
36:56:940Jacopo Vivian: here a pressure which not only makes the water safely in all the you know the system, but since you have a vertical distribution. You need to have an absolute pressure there which is high enough
37:17:315Jacopo Vivian: to so you you should have a pressure added in the plan, which is a high enough to reach that point. So it's a matter of choosing the right one.
37:33:60Jacopo Vivian: Okay? So
37:41:240Jacopo Vivian: the of course, the the disadvantage is that
37:46:970Jacopo Vivian: okay? It's on. I just finish. Now just let me finish this slide.
37:53:00Jacopo Vivian: The disadvantage now is that you have double the piping compared to the one pipe solution, because you don't only have.
38:03:800Jacopo Vivian: You see, for each radiator we have
38:07:570Jacopo Vivian: 2 pipes in this. In the 1st case we have 2 risers, one for the supply and one for the return
38:19:750Jacopo Vivian: And then another problem is that we need to follow us.
38:27:230Jacopo Vivian: The flow because the radiators on the 1st floor have a pressure difference, which is much bigger.
38:39:700Jacopo Vivian: Then the pressure difference from the last floor.
38:45:720Jacopo Vivian: That means, if you don't do anything, and you just connect the radiators like this
38:51:440Jacopo Vivian: in the 1st floor you will have much more water circulating in the radiators compared to the last floor.
38:58:540Jacopo Vivian: But we will speak about how to solve this problem in the next lecture. Okay?
39:07:770Jacopo Vivian: Okay, that's it.
39:10:660Jacopo Vivian: 8, 100.