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00:18:990Marco Marigo: Okay, welcome we can go on with the with the topics of domestic hot water. And
00:28:30Marco Marigo: I will start from the point where we are left during right? No problem.
00:38:900Marco Marigo: Okay? So we started from the point where we have concluded last time. I started to solve these exercises. So
00:49:550Marco Marigo: just to remind you about the
00:55:700Marco Marigo: It's the size of me trying to size and mix of system, and so
01:04:470Marco Marigo: to deliver 100 kilos of water
01:08:500Marco Marigo: at 40 Celsius degrees during a supply time of 1 h.
01:12:830Marco Marigo: We have already started with the the
01:17:70Marco Marigo: delivery time, and now what we are doing is A
01:28:260Marco Marigo: to take the 2 equations for the mixed water storage system, and to solve the system according to these equations, in order to know the volume of the tank, and the power to be given by the system to the domestic outwater in order to heat it up until 40 Celsius degrees.
01:51:970Marco Marigo: So I will move to the tablets now, and we are going on with the exercise.
02:19:420Marco Marigo: Okay? So I will upload at the end of the lecture this
02:26:550Marco Marigo: exercise in Pdf in the model page.
02:35:450Marco Marigo: So the second point is the writing of the equations.
02:43:410Marco Marigo: And, as we have seen,
02:47:210Marco Marigo: also in the in the slide.
02:56:720Marco Marigo: don't worry
03:08:220Marco Marigo: the equations. The 1st one is that the power with the true timing
03:20:320Marco Marigo: is equal to the mass of water.
03:24:460Marco Marigo: the Cp of the water, and the temperature difference between the supply and the aqueduct.
03:34:620Marco Marigo: Here there are the 2 terms for the thermal losses during the delivery time.
03:42:350Marco Marigo: and during the supply time the preparation time sorry.
03:51:860Marco Marigo: And then there is a term that accounts
04:01:550Marco Marigo: for the variation of the internal energy of the system.
04:10:780Marco Marigo: The second equation is the same thermal balance equation, as we have said, but just considering the preheating time.
04:27:160Marco Marigo: the term about variation of energy inside the tank.
04:45:210Marco Marigo: And so this is the system of equation that we are solving and in our exercise.
04:55:980Marco Marigo: what I'm going to do is to solve
05:00:00Marco Marigo: before considering the thermal losses and then
05:03:620Marco Marigo: neglecting the thermal losses. But another point that I want to show you is the solution in units of measurement of the international system and in unit of measurement of the technical system, you will see that there is a big difference in calculation, and at the end you will see why, usually engineers adopt the technical units to do the calculations.
05:33:510Marco Marigo: So 1st of all, I will solve the system
05:42:210Marco Marigo: with the the units of measurement of the international system.
05:48:580Marco Marigo: The 1st equation is that us? I will put the number inside. I have
05:56:150Marco Marigo: the preparation time. That is 1 h.
05:59:280Marco Marigo: the delivery time, that is, 5 h.
06:03:610Marco Marigo: and here I have to put
06:06:180Marco Marigo: the conversion between hour and seconds.
06:11:950Marco Marigo: Then I have the mass of water delivered that is, 100 kg, according to the requirements of the of the exercise and the Cp of water, that is, 4, 1, 8, 5, joule per kilogram per kelvin.
06:29:210Marco Marigo: The Delta T is in Kelvin, so I can make the difference between 40 and 10 Celsius degree. We know that we can use the Celsius degrees inside this equation.
06:42:220Marco Marigo: Then I have the losses in the delivery time, that is 36.3 watts.
06:53:500Marco Marigo: The delivery time is 1 h and the conversion in second, sir.
07:05:750Marco Marigo: and then I have the term
07:10:290Marco Marigo: about the preheating time, the losses that is, 18.1 watt.
07:15:890Marco Marigo: In 5 h, and the constant for the conversion the last term easier.
07:27:40Marco Marigo: The volume, the S.
07:32:830Marco Marigo: The Cp, 4, 1, 8, 6,
07:38:130Marco Marigo: 40, minus 10 is the Delta. T,
07:43:830Marco Marigo: okay, so as we can see here, I will.
07:49:500Marco Marigo: But I will write the second equation, that is, Qs, the preheating time. 5 h.
08:00:70Marco Marigo: The conversion, 3,600
08:07:470Marco Marigo: is equal to BS.
08:10:70Marco Marigo: The
08:14:890Marco Marigo: the maximum temperature inside the tank is 60,
08:19:110Marco Marigo: and the temperature of the aqueduct is 10.
08:22:520Marco Marigo: Blast odp is equal to 18.1 per 5 h, and
08:32:580Marco Marigo: 3,600 for the conversion.
08:36:429Marco Marigo: Here you can see that this
08:40:100Marco Marigo: unit of measurement here is an hour.
08:42:669Marco Marigo: Here we have seconds divided by hours.
08:48:340Marco Marigo: the system for the conversion. Here we have kilogram
08:52:440Marco Marigo: jewel on kilogram Kelvin. And here we have Calvin.
08:59:500Marco Marigo: This is what hour and seconds on our here it's the same, and here we have the volume
09:13:60Marco Marigo: that is kilogram the Cp. Joule on kilogram Kelvin. And here we have Kelvin.
09:21:350Marco Marigo: Of course, I'm considering the volume in kilogram, as we have seen in this equation, the density is neglected, as it's considered 1 kg per liter. Okay, so the correct would be volume in liters, density, 1 kg per liters, and then all the other. But in this point we can neglect this.
09:42:340Marco Marigo: and the equation below is the same here. The
09:46:440Marco Marigo: Us. Would be in vato in water. Of course, here it's in power.
09:52:330Marco Marigo: and the same are the other units of measurement.
09:56:170Marco Marigo: This is in Joule Kilogram Kelvin.
09:59:740Marco Marigo: It's in Calvin but hour, and this is the second recover.
10:04:810Marco Marigo: So what I can see is that
10:08:800Marco Marigo: for all this term I will have here what per second. Here we have jewel here. I have jewel.
10:19:560Marco Marigo: Okay?
10:25:150Marco Marigo: So all the terms are expressed in June, and the same is below
10:44:980Marco Marigo: for this reason. I can solve, and I will obtain the results in jewel.
10:53:10Marco Marigo: But before seeing this, the solution, let's see
10:58:20Marco Marigo: how this became. This equation become in a technical unit.
11:06:310Marco Marigo: So I will write down the same equation, but using the units of measurement of the technical units.
11:15:740Marco Marigo: So in this case I will have the value. Qs.
11:20:00Marco Marigo: One plus 5 equal to 100 multiply 1 40 minus 10 last, sir.
11:33:750Marco Marigo: Yeah, I have do it.
11:37:690Marco Marigo: And power. That is 15.6. Later we will see also the units of measurement for 5 plus
11:48:950Marco Marigo: 31.2 1 plus BS.
11:59:50Marco Marigo: Multiply one and 40 minus 10.
12:13:500Marco Marigo: Here the units are in kilocalories per hour.
12:19:750Marco Marigo: and inside here we have powers
12:27:190Marco Marigo: I change the color. So that maybe it's better for you you see
12:43:870Marco Marigo: and inside here, we have hours here, we have in kilogram.
12:48:900Marco Marigo: This unit is in kilocalories
12:57:10Marco Marigo: enogram Calvin.
13:00:30Marco Marigo: And this is in Calvin, or, better.
13:02:660Marco Marigo: Here we have associate degrees.
13:10:500Marco Marigo: Okay.
13:12:220Marco Marigo: And here we have kilocalories per hour, and here hours and the same here.
13:25:90Marco Marigo: The Easter is in kilogram.
13:27:750Marco Marigo: This is in Kilocalories, the power
13:37:560Marco Marigo: per kilogram per Celsius degree, and here we have Celsius degree, so the calculation here will give that the unit of measurement here will be in kilocalories
13:49:930Marco Marigo: for all the terms of the equation.
13:57:60Marco Marigo: But, as you can see, the solution of this equation is much easier because I have to perform less calculation. If I have to do it by hand. It's very easy to solve this equation, and much easier than the equations for the units of measurement of the international system.
14:18:220Marco Marigo: I will write also the second one, that is us 5 h, that is equal to vs.
14:27:270Marco Marigo: To multiply 1, 60, minus 10 last 15.6 hold on.
14:38:740Marco Marigo: And this is the second equation.
14:52:330Marco Marigo: The solution of this system
14:59:580Marco Marigo: with losses
15:05:790Marco Marigo: gives a volume of 100 going, 5 kg, and the power like this, 1,021
15:21:140Marco Marigo: kilocalories per hour that is equal to 1, 1, 8, 7 watts.
15:30:270Marco Marigo: If I don't consider the term with the with with the losses.
15:36:310Marco Marigo: So the calculation without losses gives, as a result 100 kg, and the power is 1,000
15:53:750Marco Marigo: kilo calories per hour.
16:01:160Marco Marigo: So what is important for you to see from this exercise
16:05:750Marco Marigo: is that if we neglected the term of the
16:09:270Marco Marigo: thermal losses. We are not making any mistake in the sizing, as we can see that in these 2 different values
16:18:260Marco Marigo: I will, of course, choose the same tank that will be around 100 liters. Okay, there is no possibility for me to change my choice. If I consider, or if I neglect the thermal losses. So in this kind of calculations, in the sizing of the domestic auto system, I can neglect the thermal losses without making a big mistake in the calculations
16:43:970Marco Marigo: business.
16:45:560Marco Marigo: Where do we in the calculation? What's the difference between? Yes.
16:55:100Marco Marigo: the calculation is in this point. So if I neglect.
17:05:00Marco Marigo: if I neglect the thermal losses, I want to consider these 2 terms in the 1st equation
17:15:660Marco Marigo: and this term in the second one.
17:35:160Marco Marigo: Any other questions about the exercise. Otherwise I will go on.
17:40:690Marco Marigo: Okay.
18:01:250Marco Marigo: okay. So we have only
18:07:460Marco Marigo: consider the the solution of an exercise about the size of a mixed auto water storage system. But
18:18:780Marco Marigo: and in the theoretical part I've shown you also the equations for the indirect system with an internal exchanger.
18:28:970Marco Marigo: I won't solve the exercise also for this system. But actually, I just want to focus on a little difference about these 2 equations in order for you to know how to apply eventually these equations instead of the 1st one.
18:47:180Marco Marigo: So if you will have to face this kind of sizing, and
18:55:340Marco Marigo: you will find the different equations, but the terms that you find inside can be the same than the 1st case. So all the assumptions are absolutely the same. You can assume the same maximum temperature, the same temperature, or the aqueduct, and so on. But the only parameter that is different is this value. That is the minimum temperature that is not present in the 1st part.
19:24:70Marco Marigo: and this minimum temperature depends on water.
19:29:900Marco Marigo: We have seen in the previous lecture that in order to make the sizing of this kind of system, we have assumed a temperature profile inside the tank of the water. Okay, in the mixed water system. I only remind you that we are talking about
19:47:140Marco Marigo: a tank in which there is domestic water. Okay? So the water is heated from domestic cold water inside the tank to the domestic hot water.
19:59:10Marco Marigo: and as we are heating directly the domestic hot water, we are assuming that at the end of the supply time there is a temperature that is enough to be supplied to the user.
20:15:00Marco Marigo: So my hypothesis is that at the end of the supply time, in the last second of my time in which I'm delivering water. The temperature don't go below the temperature at which it is required by the user. So this limited temperature will be the temperature to you the supply temperature to the user 40 Celsius degrees in the exercise
20:41:260Marco Marigo: in a system with the indirect
20:50:70Marco Marigo: heating out of water with the one that we are seeing. Now
20:54:200Marco Marigo: I remind you that you are in this case.
20:57:700Marco Marigo: So in this case, I'm considering that I've not directly the domestic water inside the tank, but the domestic hot water flows inside the heat exchanger. I have the technical water inside of the tank. So what it means
21:14:820Marco Marigo: that if I'm taking the tank
21:25:60Marco Marigo: here. I have it at the temperature of the accurate.
21:29:460Marco Marigo: Okay, I have my for a heating time
21:37:310Marco Marigo: here. I reached always the maximum temperature. But at the end of the supply or delivery time.
21:46:910Marco Marigo: okay, I will have to reach a temperature that cannot be equal
21:52:850Marco Marigo: to the temperature given to the user. Because
21:57:510Marco Marigo: for the technical watering side, I will have
22:01:110Marco Marigo: a heat exchanger. Okay? And the the water that is
22:07:140Marco Marigo: given to the user must be at the temperature tu. Okay? So the temperature of the technical water insider must be q plus
22:17:120Marco Marigo: in other delta. T, okay?
22:24:620Marco Marigo: Because at the end of the supply time I needed to have inside of the technical water a temperature that is slightly higher than the limited temperature that I have to supply to the user. And this temperature is named minimum temperature. That is the one that you see
22:46:570Marco Marigo: in the equation.
22:49:860Marco Marigo: Ian.
22:51:110Marco Marigo: So the minimum temperature
22:53:810Marco Marigo: is the temperature minimum that can be accepted for the technical water inside the tank in order to be able to provide the user, the temperature
23:07:50Marco Marigo: that is at 47 degrees usually.
23:14:160Marco Marigo: and for our sizing.
23:19:500Marco Marigo: We can fix this Delta T equal to 5,
23:26:800Marco Marigo: that it's used to do it.
23:31:890Marco Marigo: So in my sizing. Once I set the temperature to you that must be delivered to the user. For example, 40, I can also
23:44:260Marco Marigo: have the temperature T minimum, that is 45 in this case.
23:51:30Marco Marigo: So if you are
23:54:500Marco Marigo: using this second kind of system. If you are sizing this kind of system, remember that all the assumptions are the same, but this minimum temperature is not equal to the temperature to be supplied to the user. So tu, okay, but is slightly higher. That takes into account the temperature difference between the domestic water inside the heat exchanger and the technical water outside of the heat exchanger.
24:25:310Marco Marigo: is it clear this point?
24:33:600Marco Marigo: Okay?
24:39:208Marco Marigo: I added, this slide you find in moodle then, and the upload of the presentation.
24:50:823Marco Marigo: But I added this slide just because I wanted to show you a typical example that most of us, I think we have in our house. This is the
25:01:250Marco Marigo: scheme of a typical, instantaneous boiler, spontaneous gas boiler that provides domestic hot water and the space heating. Okay. And
25:13:230Marco Marigo: just to show you a very fast how it works.
25:19:590Marco Marigo: Here you can see that we have the heating of the gas in order to heat up the water inside the boiler, and then there is a main circuit that is the circuit, for example, of the radiators, or fun coils, or whatever we have in our house to heat up the house. This is the circuit. So we have the technical water that goes inside the combustion chamber.
25:42:960Marco Marigo: It is heated up until the supply time of the water in this case, and then it is delivered in this way to the radiators to heat up our house.
25:54:570Marco Marigo: But once we have
25:59:250Marco Marigo: the requirements for domestic hot water. So when you open the domestic hot water in your sink in your shower, for example.
26:08:960Marco Marigo: here we are the priority valve that switches
26:12:420Marco Marigo: the the circuit inside of the boiler. So the technical water that is entering inside the combustion chamber. Don't go to the
26:26:330Marco Marigo: to the radiators, for example, but is deviated inside this plate heat exchanger, and the circuit becomes this one. So inside the plate heat exchanger, and then comes back to the combustion chamber.
26:37:660Marco Marigo: And so we have this closed circuits of technical water, and on the other side there is the domestic cold water that is heated up and then becomes domestic hot water. So usually in your instantaneous boiler with gas burning, that is a technology that is sometimes very
26:58:790Marco Marigo: usually very often present in our houses. We have this kind of system that heat up both the technical water for the heating system and the domestic hot water using a plate heat exchanger.
27:12:990Marco Marigo: And this is why this priority valve is why, usually in your house when you heat up.
27:19:950Marco Marigo: but when you open the sink or the shower you have that your heating system is reached off. So there is no more hot water that is flowing inside of the system. This kind of
27:34:690Marco Marigo: preparation for domestic hot water is this one? So we are talking about the indirect preparation of domestic hot water through a plating heat exchanger, and on the other side, we have technical water.
27:51:440Marco Marigo: Okay?
27:53:870Marco Marigo: I will, firstly, move to the second, the last part of the presentation.
28:01:980Marco Marigo: So when we are
28:06:680Marco Marigo: looking to solve an exercise. We have the input data, as we have seen in our exercise. But when you have to size a system, you must do your own assumptions. And so now we are seeing on the equations that we have solved, which are the assumptions that we can make in order to size a system, for example, for your house or for
28:31:710Marco Marigo: whatever you want, and a different building I don't know.
28:37:330Marco Marigo: So the sizing
28:39:910Marco Marigo: already spread last time it's deciding the volume of water and the power required for my system to be given to the water and the 3 Assumption. The 3 most important assumption that depends on your case study. Are those listed in the upper part of this slide. So
29:00:820Marco Marigo: in this case we are preparing.
29:05:490Marco Marigo: we are choosing these 3 assumptions that are the domestic hot water demanded during the peak load. We will have to calculate this value, and then we will have to assume the time of reparation and the time of supply and delivery
29:22:370Marco Marigo: on the other side. We also have some other assumptions, but these assumptions are usually made like this, so the temperature of supply usually is acceptable to be fixed at 46 degrees.
29:38:960Marco Marigo: The maximum temperature inside the tank usually is around 60. Okay, and the temperature of the water of the aqueduct depends on where we are in terms of geographical position, but can be assumed between 10 and 15 Celsius degrees.
29:54:950Marco Marigo: usually in the colder parts of the of Italy in the northern part is closer to the 10 Celsius degrees Assumption. In the southern part of Italy. You can also assume 15 Celsius degrees. There are in some technical guidelines. It is the advice is to choose the temperature according to the average yearly temperature of the year.
30:20:360Marco Marigo: So there are different way of sizing, but usually the range is in this temperatures.
30:31:140Marco Marigo: and how to choose the 1st value. That is the
30:40:616Marco Marigo: the use of domestic hot water during the the day during the peak load, and there is no
30:54:790Marco Marigo: or better. There are some regulations about this. There is, there are some standards, but
31:01:720Marco Marigo: the probably the best solution is to size the system according to a German standard, that is, the buddy, 1988.
31:12:540Marco Marigo: There is also an Italian standards that try to and
31:17:750Marco Marigo: make an assumption and make the design for this peak load, but
31:23:830Marco Marigo: it overestimates a lot to the volume of water to be used by the user. So
31:30:110Marco Marigo: it is better to use these standards. There will be also an European standards that is going to be uploaded, the 806 in which there is
31:42:440Marco Marigo: of looking at these calculations. But actually there is not the final version of these standards. And so it's under revision
31:51:890Marco Marigo: by now we can use this this table that is taken from a Vdi standard.
31:59:220Marco Marigo: And in this case you you have to know about your case study. So you must know which is the case. Study the number of fixture you have inside. And so you just list
32:12:860Marco Marigo: the number of fixture you have in your case study. So how many bath tub we you have, how many showers, how many toilet sinks. Okay? And here you have an estimation on the water used per fixture. So each one of this fixture is assumed to use this amount of water at 40 sizes degrees per one user
32:34:660Marco Marigo: of it.
32:36:490Marco Marigo: And so by now you can calculate the amount of water used for the total number of fixture in your house. So, for example, here you have
32:46:320Marco Marigo: 2. So 2 showers. Each shower uses 60 liters, and so you have 120 liters.
32:54:880Marco Marigo: Then you must calculate the or better, you must assume the number of times that that feature could be used during the peak load.
33:05:430Marco Marigo: So if I have a shower, I can assume that I use it twice.
33:11:510Marco Marigo: but if I have 2 showers I can assume that I use just once, but this also depends on your case study. If there are 6 people in your case study, you must use a number that is higher than this.
33:25:880Marco Marigo: if you have just one, probably also
33:30:260Marco Marigo: the true number of shower you can use 0 point 5 in this coefficient. So this assumption must be done according to your case study.
33:40:120Marco Marigo: When you have decided.
33:42:250Marco Marigo: You have fixed the number of fixture and the number of times per each fixture to be used during the peak load. You can calculate the total volume of water
33:53:970Marco Marigo: that is required by this fixture during the peak load, and then, by summing all the values, you will obtain. The total volume of water
34:05:860Marco Marigo: during the peak load for your case study, and this value is the detailed value that you can use for your calculation is the value
34:15:929Marco Marigo: that here we have called Md. And that was also the nomenclature in the equations
34:25:780Marco Marigo: for the supply and the preparation time.
34:30:20Marco Marigo: We can refer to this table
34:33:989Marco Marigo: for the residential units. So for the residential units. Usually this line is the
34:40:800Marco Marigo: the most frequently used, so usually we use it, deliver
34:45:510Marco Marigo: 1.5 h, and the preheating time of 2 h.
34:49:639Marco Marigo: This is
34:50:940Marco Marigo: mostly used. If you have a higher surface, you can also increase the delivery time. If you have a lower surface, you can decrease the delivery time. But in this case there is no strict rule. Okay? And if you make this assumption.
35:07:430Marco Marigo: it's usually would for a residential unit.
35:18:570Marco Marigo: And what we're going to do now is to move to the second calculation
35:26:860Marco Marigo: about the domestic water. As I said, you last time told you last time the 1st part was about the sizing, and then we have a second part. That is, about the energy calculation
35:38:380Marco Marigo: for domestic automotive preparation.
35:42:690Marco Marigo: In your effort. You will be asked to do both these calculations.
35:47:170Marco Marigo: but this one is much easier.
35:50:740Marco Marigo: The method to calculate the energy need for domestic hot water is explained in an Italian standard. That is, the 11300, part 2,
36:03:190Marco Marigo: and all the equations that I will show you in the next slides are about this part of the standard
36:10:670Marco Marigo: pay attention. I will use the letters according to what is written in the standard. So in this case vw. Is not has nothing in common with the the storage volume
36:27:500Marco Marigo: that I showed in the 1st part of the presentation. In this case it was the volume of the tank. Here we are talking about the liters per day of water delivered for a case study.
36:38:760Marco Marigo: Here we have a different name of the of the terms.
36:44:450Marco Marigo: So this part of the standard says that for calculating the daily volume of water used
36:52:980Marco Marigo: by residential buildings, we can use this equation.
36:58:600Marco Marigo: That depends on 2 constants
37:01:650Marco Marigo: that must be calculated in a table that you can find in the same standard.
37:07:140Marco Marigo: The table is this one, and
37:11:150Marco Marigo: and so I need to know the surface of my house, and then assuming
37:20:830Marco Marigo: the parameters accordingly to the surface of my house at the floor area, I can calculate the volume in liters per day.
37:34:620Marco Marigo: So this is just a 1st example. If we are having a single unit, residential building
37:41:900Marco Marigo: with the 6 people and the floor area of 180 m².
37:49:770Marco Marigo: I go in the table. 180 is in this part of the table. I can assume C. 0 equal to 1.0 6 7 and c. 1 to 36.6 7.
38:02:220Marco Marigo: Once I've done these assumptions that are here, I can calculate the daily volume of domestic hot water
38:10:190Marco Marigo: as 228.7 3 liters per day.
38:18:760Marco Marigo: This value has nothing to do with this value.
38:25:600Marco Marigo: Okay, this value is a value I want to remember that is calculated for sizing, and this
38:34:420Marco Marigo: the worst case scenario in
38:39:530Marco Marigo: peak load. So if I have the peak load that, for example, 2 h. Okay, in those 2 h. The worst case scenario is that I use 247 volume of domestic hot water at 40 degree, but it's just the worst case to go on with the sizing.
38:58:220Marco Marigo: In this case this is a statistical equation, and the standard standards tell me that in one day
39:05:530Marco Marigo: this is the amount of water that I use, and
39:11:180Marco Marigo: for my purposes my user uses, uses
39:15:140Marco Marigo: and it changes according to the surface of the floor area of my house.
39:26:880Marco Marigo: But if we are not talking about a residential building, but another type of building, I have a different equation. That is this one. So I just have to take the assumption on the
39:39:360Marco Marigo: coefficient of C. 2.
39:42:270Marco Marigo: And in this case the volume of water, the daily volume of water must be calculated according to the number of units.
39:50:280Marco Marigo: This is a parameter that is given in the table, always from the same standard.
39:56:100Marco Marigo: and it depends on the user of my building. So, for example, in the hotel, in the residencies in the Airbnb and in the Bnb. Sorry bed and breakfast
40:07:680Marco Marigo: hospitals is related to the number of beds, so I will calculate the volume of water according to the number of beds that I have in that
40:19:880Marco Marigo: case study, for example, in the sport hall the number of units depends on the number of showers.
40:26:410Marco Marigo: That is quite
40:27:900Marco Marigo: easy, and in the school it depends on the number of children, so I will have to look at my non residential building. See which is my case. Go and check for the number of units, and then choose the constant.
40:43:310Marco Marigo: For example, in this case, in a 3 Star Hotel I have 10 beds. For example, I take the Associated
40:51:890Marco Marigo: coefficient of 4 10 beds, and they can calculate that the daily volume of domestic hot water is in this case 600 liters per day.
41:10:750Marco Marigo: And why is it important to calculate this parameter because it is the main input for the final equation for the calculation of the energy needed for domestic hot water.
41:23:80Marco Marigo: So the same standard, the unity. S.
41:26:430Marco Marigo: 11300, part 2. Give us this equation, and this equation is the final equation to calculate in kilowatt hour
41:36:160Marco Marigo: the amount of energy to be used to heat up my need of domestic contributor
41:43:760Marco Marigo: here. I will put the value that I've just calculated with the previous equation pay attention. It's in cubic meters per day. So I will have to change the unit of measurement.
41:56:340Marco Marigo: and then I will ask the other parameters. So the density in 1,000 kg per cubic meter.
42:03:950Marco Marigo: The specific heat with this unit of measurement in kilowatt hour per kilogram per cabin.
42:12:650Marco Marigo: I have just said that the daily water volume is in cubic meter per day.
42:17:340Marco Marigo: The water supply temperature is assumed at 40 Celsius degrees.
42:21:940Marco Marigo: The cold water supply temperature comes
42:25:990Marco Marigo: from the assumption that I've made in the acquit. So 10 sizes the reason.
42:31:710Marco Marigo: and at the end I have the number of days for my
42:35:240Marco Marigo: time in which I'm analyzing my system to understand which is the requirement for the energy need for domestic hot water.
42:47:910Marco Marigo: These are the examples for the calculations for the 2 K study we have just seen.
42:53:630Marco Marigo: So the 1st one is the unit, the residential unit with the 6 people.
42:58:710Marco Marigo: I have just calculated the volume of water 2,028 liters per day. I change
43:05:760Marco Marigo: the 2,029 liter. Per day in 0 point 2 2 9 cubic meters per day.
43:12:50Marco Marigo: and then I use all the numbers that I have just shown in order to calculate the energy, need the annual energy. Need you see that here I have booted 365 days.
43:28:810Marco Marigo: and I can calculate
43:31:60Marco Marigo: the energy that is 2,257 kilowatt hours per year. This is the annual energy need of domestic hot water.
43:40:920Marco Marigo: For that case study.
43:44:110Marco Marigo: If I take the no residential one, I have the same assumptions, so
43:48:710Marco Marigo: 40 Celsius degrees. Here you can see in this calculation there is 14 Celsius degrees for the assumption, for the cold water from the aqueduct.
43:56:320Marco Marigo: This is something that depends on your assumption.
44:01:260Marco Marigo: And this is the calculation for the energy needed for the non residential planes.
44:07:440Marco Marigo: So what I, yeah, presenting you to conclude this part
44:15:70Marco Marigo: is that in your report you will have to submit
44:22:840Marco Marigo: a section which is called the Calculations for Domestic Automotor.
44:27:620Marco Marigo: This section is divided into 2 parts.
44:31:310Marco Marigo: You will have to size. 1st point for your case. Study the domestic hot water system for your home.
44:41:120Marco Marigo: You can decide to use both the system we have seen. So
44:48:840Marco Marigo: the system with an indirect internal exchanger, or a mixed hot water for a system. So
44:57:250Marco Marigo: it's up to you to decide which of the shoe system to install.
45:01:120Marco Marigo: Okay, but you have to
45:03:490Marco Marigo: write down in the report which is the system you have chosen, and then provide the calculations and the true output of the sizing process. So the power and the volume.
45:18:20Marco Marigo: then the second part, that is, you are asked to submit is the calculation of the energy need for your domestic automotor system according to the equation that we have just seen.
45:34:530Marco Marigo: I think that everything is clear.
45:38:860Marco Marigo: I don't know if you have question about this. Otherwise I will tell you just
45:43:470Marco Marigo: just few couple of things.
45:48:420Marco Marigo: Okay.
45:52:960Marco Marigo: the last point is that I ask you for the report. So just for the report to use this equation to calculate
46:01:730Marco Marigo: the
46:03:190Marco Marigo: mass of water used during the peak load. So don't use the detailed calculation. Don't use the buddy. 1988. Use this equation. Put inside here your floor area and calculate the mass of water to be used during the peak load.
46:19:940Marco Marigo: This is a simplified equation just for the course. He has no validity outside this course.
46:31:590Marco Marigo: and this is the table that you can use for your calculations, and is the same that then the one I showed you before.
46:41:430Marco Marigo: So, according just I, I want to be clear just for the report. You must use this equation, so don't
46:50:480Marco Marigo: deliver, submit the reports with the detailed calculation. I want this equation and disable for the assumption of the preparation and the delivery time.
47:04:70Marco Marigo: A.
47:06:740Marco Marigo: The last things I want to tell you is how I check the report you deliver.
47:12:910Marco Marigo: So when you deliver a reporter.
47:16:130Marco Marigo: the 1st thing I look is your calculation, so I check. If your calculation are correct, if your calculation are not correct in this part of domestic automotor sizing and calculation for energy needs.
47:29:910Marco Marigo: your vote is 0, because we are really talking about just 4 equations.
47:36:500Marco Marigo: If the results of these equations is wrong, I have to put 0 in the calculations. Okay, so please check your results. Last year there were
47:48:170Marco Marigo: at least 30% of you. That of course it was. It was not you, your colleague, submitted the record with a completely wrong calculation.
47:58:950Marco Marigo: The main mistakes where the 1st one is someone choose
48:04:570Marco Marigo: a wrong equation. So they wrote that they were sizing the mixed water solar system, and then they chose the other equations for the sizing.
48:14:90Marco Marigo: Some of them
48:15:570Marco Marigo: was wrong with the units of measurement, so forgot to put the conversion factors from how hard to seconds or assume the wrong value for the specific heat. So please check your calculation. There are a lot of people, and I hope not. But I
48:34:390Marco Marigo: there could be also some of you that deliver the report with the wrong calculation, so please check the the calculation, and also pay attention of what you write in the report. If in the report the result is not clearly written, and the assumption are not written, I must
48:53:50Marco Marigo: believe some point.
48:54:510Marco Marigo: because sometimes there are, there is some of you that make also the calculation perfect that deliver the calculation in the excel, and then in the report there is written nothing, there is not the result. There is no the assumption. And so also, in that case I must take on some point. So
49:10:850Marco Marigo: please check that. Your report is written clearly, correctly. There is, there are just the important information. But all those information are presented clearly, and they can understand the results.
49:27:990Marco Marigo: and at last, but I think that is general for all the reporter.
49:33:680Marco Marigo: All the calculations you show in the report in the Pdf. Must be also delivered in excel form, and I must check the calculation. It's important that I am able to check your calculation, otherwise I am also
49:52:500Marco Marigo: lowering the the points of your report. So please, when you submit to the report in Pdf, be sure that you are also delivering an Excel file where I can check all the calculations. So there must be the equations inside that I can check.
50:13:580Marco Marigo: If there are no more question clarifications or something else.
50:19:880Marco Marigo: I leave the floor.
50:23:150Marco Marigo: Okay, yes, just to remember that you? Yes, please.
50:30:930Marco Marigo: Yes, they are.
50:32:690Marco Marigo: If you write on the wrappers, it's okay.
50:56:940Marco Marigo: The excel is just to check the calculation, just to check the calculation in case you make some mistake which are not visible in the report
51:07:490Marco Marigo: conversions. No, that's okay. No, no, that's okay. It's up to you.
51:12:810Marco Marigo: I mean, we just need the report. I mean, we just we just need the Excel file in order to see
51:19:540Marco Marigo: in detail what you did. Okay, to check. If there are some mistakes that are not visible, or to find mistakes that
51:29:340Marco Marigo: might be Downing from like reading the room.
51:34:100Marco Marigo: The reference, the record is in word, and should, let's say, represent what you you did. Okay.
51:46:30Marco Marigo: it is. It is needed to be, let's say summarized. But here, right
51:51:740Marco Marigo: then, in case we have some doubt, we go in the Excel file to see what could be. If you, if you deliver the record without the Excel file
52:03:890Marco Marigo: we cannot trust. You cannot write all the questions in the report
52:19:20Marco Marigo: you have. You have 24 values for the cooling order, and they come from I don't know how many you you cannot write all the all the I mean the list, I mean.
52:29:850Marco Marigo: like the 1st step. Take a example that thanks.
52:39:620Marco Marigo: So you did those energy. Right? Yeah. So the report is similar. Okay? But in this case we want the Excel file as well.
52:50:350Marco Marigo: But okay, yes, that is a good point. You have to push. Yes, yes.