Latest / The Refrigeration Mentor Podcast / Episode 192. Designing CO2 Supermarket Refrigeration Systems: Understanding Heat Loads with Chris Griffiths of Omega Solutions (Part 2 of 5)

Transcript

Episode 192. Designing CO2 Supermarket Refrigeration Systems: Understanding Heat Loads with Chris Griffiths of Omega Solutions (Part 2 of 5) · The Refrigeration Mentor Podcast

• 0:00
  Chris: It becomes the, uh, no brainer. It's number one thing you should do. Reduce the energy consumption through the lifespan, but also allow you to have smaller equipment. It's a win win situation. All adds up and more, more you can bring to your customers with that sort of cost benefit analysis and more they're going to.
• 0:01
  Come back to you for extra work.
• 0:02
  Trevor: Welcome to the refrigeration mentor podcast. I'm your host Trevor Matthews as a former technician turned entrepreneur.
• 0:03
  Chris: My goal is to really help train you, educate you and mentor you in the commercial refrigeration industry. Each week, I'm going to have top guests from
• 0:04
  Trevor: technicians.
• 0:05
  The manufacturers
• 0:06
  Chris: to experts around the world to really help
• 0:07
  Trevor: us grow and learn together by sharing their knowledge in commercial refrigeration, commercial HVAC. And not only on the technical side, but really the professional and the personal development side as well.
• 0:08
  Chris: I'm really excited that you're
• 0:09
  Trevor: here.
• 0:10
  Now let's get a conversation going. Hey, I want to take a minute to talk about the upcoming refrigeration mentor learning programs. Every couple of months, we continue to roll out live instructor led sessions by subject matter experts on
• 0:11
  Chris: compressors,
• 0:12
  Trevor: supermarket refrigeration, and CO2 refrigeration. We're really here to help you grow.
• 0:13
  Get to that next level. Head to the Refrigeration Mentor webpage, refrigerationmentor. com. Check out the events page. There's a compressor masterclass, there's a supermarket refrigeration program, and there's a CO2 program. There's also free trainings, free workshops. Really, check them out. See if this interests you.
• 0:14
  Read a little bit about it because we're really here to help you. These live sessions are for you to come and ask questions, to learn a little bit, to grow. We've trained thousands of technicians from technicians from three to four to five years in the industry, all the way up from 20 to 30 years in the industry.
• 0:15
  Either get them to the next level or get them back on track, build that confidence, that knowledge and that skill set. We'd love to see you there. We'd love to have you. Now let's get a conversation going. Welcome, welcome to part two of our five part series last week was fantastic. I learned so much from Chris.
• 0:16
  We dove in and got a real good understanding on all the different compressor sizing, gas cooler sizing. And this is just the beginning. You know, we got another four more sessions to go, which leads up to our advanced course. Coming up now, and it's going to start in, in the spring 2024. This, this course is going to be game changing for designers out there learning how to design transcritical CO2 system.
• 0:17
  And this is what it's all about. And this is why we're here. We want to share some valuable knowledge, and I really appreciate all the people that email me, send questions in. Who took a huge amount of value away from part one of the series this week. We're going to be diving into understanding heat load calculations, because this is super important to really, uh, get you to the next level.
• 0:18
  And when you understand how to, uh, you understand the heat load calculations from different cabinets from different systems for CO2, it's going to make you so valuable to your life. Organization as well as other organization. Chris, welcome back to part two. How
• 0:19
  Chris: you doing brother? It's a pleasure last week It was very enjoyable.
• 0:20
  We had some really good responses and some good questions. So looking forward to it
• 0:21
  Trevor: Yeah, no, we we got a ton of uh knowledge to share here today. That's really gonna really help you So ask the questions in the chat because we want to get you to where you need to be Because if you're, you're, you're new to design or you're already designing systems for CO2, but, or HFC systems, and you just want that next level stuff.
• 0:22
  This is it. Chris is the expert and that's why we're doing this today. So Chris, why don't
• 0:23
  Chris: we get kicked off? So straight in, I think we'll see leading on from last week, where we looked to compressors and condensers and gas cooler selection, we've looked to be. Energy and how we're going to reject the heat we pick up.
• 0:24
  Now we're going to look at what we actually need to get rid of with our heat load. This is the basis of our system. There's so many advances coming out at the moment. We're working with some end users, trying to think ultra low duty refrigeration display cases. Uh, you're looking less than one kilowatt for a 12 foot case.
• 0:25
  It's unheard of. All glass doors, super energy efficient fans, lights. It's, it's going to be game changing. So going back to understanding how the heat loads all interact is going to be really key. going forwards. Hopefully after today's session people should be able to understand the basis of heat loads, how they're calculated and hopefully we can move on to a little bit on expansion valve selection because that tends to work quite well in terms of when we're using evaporators, that's how we feed our refrigerant into it, having the size of how much duty we need to cool, we can set the valve appropriately.
• 0:26
  Hopefully this isn't a strange principle to most refrigeration experts out there, but heat transfers in three different ways. We have conduction, convection, and radiation. Just to summarize, conduction, where materials are physically touching, the energy will pass from the molecules, vibrating in contact with each other, and will transfer from high energy to lower energy.
• 0:27
  Convection, which is where most of the heat transfer takes place in refrigeration, where we're moving air across a product. The cooler fluid will absorb the heat from the warmer surface, or fluid which is being passed across it. And then we have radiation. A small amount of heat transfer occurs, for our purposes, that is emitted by a line of sight from a warmer body to a colder one.
• 0:28
  It doesn't transfer through a medium, it is just pure line of sight, hot body, cold body, and eventually all that heat transfers from an area of high energy to low energy. More usefully, we measure this in temperature. So Celsius and Fariclight are the terms most people are going to be familiar with. We use Celsius in metric.
• 0:29
  Our North American market are going to be mostly familiar with Fahrenheit, I expect. We also have Kelvin and Rankine, which are the absolute scales. They start at zero, no energy being used whatsoever. I'm not sure of the conversion between Rankine and Fahrenheit, but Celsius to Kelvin is around 273. 5 degrees different.
• 0:30
  It's the same scale, it just starts at a lower point.
• 0:31
  Trevor: One of the things that I've learned over the years, especially working at a manufacturer that has European companies, is that Calvin is used for a temperature difference when you do superheat. And we use Fahrenheit here, so that was a big thing that I needed to understand because I would read these manuals from Dan Foss, from Bitzer, and it would say, okay, you need 10 Kelvin.
• 0:32
  And I'm like, well, what does that really mean? And that's actually, it's 18 degrees Fahrenheit. So you have multiplied iCalvin only temperature difference by 1. 8, and then you would get the Fahrenheit scale for superheat for a temperature
• 0:33
  Chris: difference. Yeah, you have to do a lot of conversions unfortunately in this industry.
• 0:34
  I feel like there's no other industry out there on the planet which needs to go between imperial and metric so often, other than refrigeration. Lastly, hopefully you've processed everyone's menu with hot goes to cold. It's second law of thermodynamics, energy changes from one to another, higher grade to lower grade energy.
• 0:35
  And the whole point of why we need refrigeration, sometimes it's hotter outside than it is where we want it inside. So we need to put some sort of mechanical process in place to drive that process, which brings solid to heat loads. So, when we're designing, thankfully display case manufacturers put huge amounts of R& D effort in and they'll give you a nice data sheet which says exactly how much duty bag cabinets require at certain conditions.
• 0:36
  So, purpose of today, I figured let's go through the process of sizing a, a cauldron, cool box, however you want to refer to it. In here we're gonna have our, our evaporator, one of the installs I managed a couple of years ago. Not quite fully finished, this one has some dirt on the walls, it hasn't had it's quite sparkle clean ready yet.
• 0:37
  But we can run through the process of how we size it and how we set the equipment to go in it. So first off, we have fabric loads. So fabric loads refers to the fabric or the envelope of the structure that it's sitting in. So this would be the walls, the floor, the roof, um, any doors or any air gaps involved in that as well.
• 0:38
  We're also then going to have product loads, which is the actual and then the item we want to cool, the purpose that we're building the room for. That's going to be, it could be produce, it could be meat, it could be ice cream, it could be anything, anything that the customer wants to put in there. Each thing goes in there is going to have its own specific sheet capacity needs to be taken out of that to achieve that temperature which is desired.
• 0:39
  Infiltration loads, so infiltration loads tend to refer to air movement working through a room. The main one for a cold room is going to be the door opening, although you may have extract fans if you're storing a volatile product or gas. If it's a CO2 room, for example, and it's a fairly large scale, you may have extract fans which turn CO2 leak.
• 0:40
  You're going to have to take that into account, because if that does then Ultimately your room is going to start to fail because you've lost your refrigeration equipment, but how long will it take for that room to increase in temperature until it really becomes a concern? I meant ancillary loads, so ancillary loads covers everything else which doesn't fall into the first three.
• 0:41
  Generally, we have lighting, we have defrost heaters, we have evaporators, we have fan motors, we may have people working inside the room, you might have forklift trucks if you're in a large warehouse, you might have rapid rise doors, you could have anything else which produces heat in a space. The same process works for air conditioning as well, but certain weights will be applied, so in terms of fabric load, you may have windows now.
• 0:42
  Now the solar gain, that's gonna be a large part in how much energy you need to take out of that space. Instead of product loads, the main thing you're going to want to actually cool down are people. It's different priorities. And that gives us our total loads. So the total load could be then split into multiple evaporators, or, for example this room, we had two evaporators for roughly 7 evaporator, but for similar reasons to what we mentioned last week in terms of redundancy, for energy split, and also if you want one incubator continuing to run whilst another one's out of commission for maintenance, you can make sure it maintains the temperature in the room without too much issue.
• 0:43
  Thank you very much.
• 0:44
  Trevor: This is so important because this is the investigation you need to find out you need to find out I was at a CO2 site last week, where they're just like you said they got forklifts going driving in all the way through. And if you have four forklifts there and you only schedule for one for 10 hours a day.
• 0:45
  That makes a big difference on the load because actually that system that I was at was actually Um shutting down because they were I think it was I don't know if it's oversized or not But they were satisfying very quickly way quicker than they expected which caused havoc on the rack actually So this is important when you're doing this design as a design engineer You got to get the facts and sometimes you got to ask multiple times because maybe that job changes a little bit over time.
• 0:46
  So you do your one first design on your heat load calculation. You might have to do it again. Have you ever come across that, Chris?
• 0:47
  Chris: Yeah, so when customers requirements change throughout, this room is actually a good example of that. When we started designing it, it was 10 meters wide, halfway through the design process.
• 0:48
  They want to extend it, store product, makes sense. Unfortunately, that went over the original design conditions of the evaporator, which was selected. So that involves adding an additional evaporator, which then involves different pipe routes, an additional set of refrigeration services. Do they want it on the same pack, or do they want it on a separate system, when you have to introduce a condensing unit, and it soon starts to add up in terms of complexity, what might seem a simple change to begin with, where it's halfway through the design process, sometimes your strategy has to change, and You have to make the best of what you'll give up, rather than be able to think, well, if we had two systems to begin with, we could have, maybe, if there's two packs in place, we could just split it off and even load.
• 0:49
  But it might not be an option any further down the road. What you said about over sizing or under sizing as well is very important. If you have a product which needs to be maintained at a premium, If you oversize the equipment, it's going to achieve temperature before it's had a chance to suck a lot of the moisture out of the space.
• 0:50
  Um, for dehumidification, so you may end up getting sweating in the room. Or all sorts of other issues that you might not get if it's sized for the application it should
• 0:51
  Trevor: be. And what I see a lot of time too, when you get into more of the larger processes, processing plants, you don't have as much different loads as like I say, a supermarket.
• 0:52
  So you might have just one big room where if all of a sudden those coils start to satisfy, you got to really understand. That do you need to add extra loads? Cause I've seen a lot of CO2 systems where they'll have an extra coil, maybe in the mechanical room to keep the system running. If there's example, like hot gas, defrost, things like that.
• 0:53
  So this is a designer that, uh, this is, we'll be diving into that, that full on course.
• 0:54
  Chris: So, yeah. So at the end of the day, we want the total load. Which gives us a simple number we can set equipment from, which over here, we use kilowatts, uh, very handily. It's the same as the unit of electricity that is used to drive the system.
• 0:55
  So we can work out some easy efficiencies as well. Elsewhere, you may have BTUs or cans of refrigeration. Basically, we just want that one number which allows us to select the equipment that we need. Go through those, we'll split it down, break it down, go through each section of that bit slower and in a bit more detail.
• 0:56
  So, let's look at fabric loads to begin with. Generally, there's four parts which we need for each one of these equations. We have material thickness. How much heat is going to get through that wall will have structure. The room to continue heating up Inside this material thickness will have a property called transmittance.
• 0:57
  That basically is how good it is at insulating against heat transfer. We have the surface area of the, of the room of each wall. So the larger surface area, more heat is going to transfer our purity 'cause there's more. availability for it to do so. I mean, going back to everything seems to have an refrigeration, the importance of the temperature difference of the wall outside to the space inside.
• 0:58
  If your condition outside is, say, 10 degrees more than your room inside, you're going to need smaller equipment, less refrigeration duty, than you would if it was 20 degrees or 30 degrees higher. And
• 0:59
  Trevor: that was like the site I was at. The wall, the outside building walls was the cooler. So the, you know, the building's actually the cooler.
• 1:00
  It wasn't like there's a box inside the The facility, like in kind of a supermarket application where it could be, you know, 75 degrees at all times where now the outdoor ambient changes. Like it's minus 20, it was minus 20 out when I was there and in the middle of summer it's going to be 110 degrees Fahrenheit out there.
• 1:01
  So this is what you really need to understand as a designer. We've had
• 1:02
  Chris: some agricultural buildings I've worked on in the past where, again, as you say, the structure of a room is directly outside. So not only have you got to worry about overheating in the summer, you've got to worry about that room getting too cold in the winter.
• 1:03
  So you're going to have to install evaporators with heater elements on them to make sure it's actually maintaining that product so it doesn't start to freeze. So it's all parts which need to come into play as a designer. You need to consider every opportunity, every scenario that equipment might be required to operate in.
• 1:04
  As we add up through, we start getting to the scientific notation. Q equals U A delta T, which is one of those things that looks absolutely nonsense until you start breaking it down, whereas a Q is just a symbol for the heat load aspect, or the energy required. So, in this aspect, Q is our throughput load.
• 1:05
  It's made up of a U value, A value, and delta T. Our U value is that transmittance through the wall. So we sum all those, multiplied by the area, meter squared, or square footage of that structure. And then we have our temperature difference from inside to outside. Multiplying all those together, and then adding up the sum of every single wall or surface of that room so you have a different value For your floor, ceiling, each wall, wherever you've got windows, doors, uh, open gaps entirely in them, you get out to different areas and that gives us our total fabric load for the space.
• 1:06
  We'll always size up a worst case scenario, so hottest, highest temperature difference from inside to outside. Before I move on, one of the projects we've been looking into at Amiga is actually the payback time and the difference in energy usage from just increasing that standard cauldron thickness size.
• 1:07
  Over here it's 100mm. If you go to a slightly thicker panel of 125 mil, 150 mil, so 5 inches, 6 inches, you can have a real significant difference in the amount of energy that plant can see over the lifespan of it. You're talking thousands, tens of thousands of pounds or dollars if you, for the sake of a tiny amount of extra fabric in the start.
• 1:08
  And this
• 1:09
  Trevor: is a good point when you're talking about, you know, capital costs versus operational costs, because right now, you know, capital costs, everyone's looking at, okay, well, we want to keep it as the price, the best, but that operational costs. Now, if you're not working together with your teams and as a designer talking about this with your end users, it's going to be very challenging because maybe you save in the front end and the capital costs.
• 1:10
  But that operation cost is going to cost you hundreds of thousands of dollars, depending on the size of it. So this is where as a good designer, you can bring this information up and talk to them and show them. Because at the end of the day, the end user is going to make that decision, the final decision.
• 1:11
  But when this brings value to them, when you're showing them and lay these different plans and paths out for that total cost of ownership.
• 1:12
  Chris: It can actually have a cost neutral increase as well, because any extra you spend on this. is going to reduce and reduce the cooling load and effectively reduce the size of your refrigeration equipment going in so you can Remove a compressor from your rack.
• 1:13
  You've saved probably more money from that alone as the extra fabric material costs added to the project. So it's definitely a place where it becomes the no brainer. It's the number one thing you should do. Reduce the energy consumption through the lifespan, but also allow you to have smaller equipment.
• 1:14
  It's a win win situation. And this is
• 1:15
  Trevor: why Omega Solutions is one of the top designers for CO2 systems in the world. So always reach out to. To them i'll put the details in the episode and i'll shoot it in the the chat here But this is this is the conversations you need to get into and this is what the program is going to be all about How to build that perfect system for your
• 1:16
  Chris: customer all adds up and you're more More you can bring to your customers with that sort of cost benefit analysis and more they're gonna Come back to you for extra work.
• 1:17
  You do yourself a favor at the end of the day. Product load. What do we actually want to cool? So, we need to know exactly how much we're going to cool. This is going to be your mass of product or product throughput. So, say you have a cauldron which is being constantly loaded every six hours and then depleted as it proceeds.
• 1:18
  We need to make sure that product's cooled in that period of time. We have the specific heat of a product. So that is the amount of energy each kilogram or pound of that product material is going to absorb, require to absorb or expel to adjust in temperature by one degree. Again the temperature difference and the cooling duration for this.
• 1:19
  So it's going to require more cooling load to cool a ton of fruit and veg over three hours as it would over six hours. It's directly proportional. So if we double the amount of time we have to cool it, we have the size of the equipment. You could cool the entire room in a second, but you might need 250 kilowatts.
• 1:20
  You cool it over six hours, you might need two and a half. So it's always a trade off. Calculation for this, Q, our energy, is equal to our mass of our product times by the specific heat capacity of that product. This can get more complicated if you have a variety of products, you may have a portion of meat, vegetables, ice cream, anything else inside that room.
• 1:21
  They're all going to have slightly different properties. I think the ASHRAE refrigeration guide has a very, very long list of this. Or a lot of cold sizing software out there will do it for you as well. Our databases with all these different properties, and by we are a temperature difference again at the start and end product temperature.
• 1:22
  Say it enters at five degrees or that B 30 37 Fahrenheit, A want to cooler it down to one degree Celsius or three to two Fahrenheit. First two zero degrees. It's a three to three, then divided that by the number of seconds in an hour. Now I get to sell
• 1:23
  Trevor: a potential product load. And this is important too because you could have a customer that changes their product throughout the year.
• 1:24
  So you want to understand what products they'll be putting in there and potential products they've put in there. Because I work with a lot of industrial companies now where they're like, okay, we're going to expand in two to three years. So let's build the equipment now for two to three years down the road.
• 1:25
  But you got to be careful when you're doing those designs because you can run into a lot of issues. Okay. Designing an oversized system for future projects. So we'll get into that later as well. There's another one
• 1:26
  Chris: as well, a lot of agricultural places, they'll only be running for maybe a month of the year.
• 1:27
  For example, turkeys at Thanksgiving and Christmas, they'll have a blast chiller application. So you'll oversize the equipment to pull that temperature down from body temperature as they carry out their slaughtering down to a storage temperature. But once they store it, you need such a fraction of the energy you need.
• 1:28
  to keep it at that temperature. So generally, you'll have a very, very large evaporator or two evaporators, which run for that short period of time, and then it just operates off of one to maintain that temperature in the space. So it's a way of splitting equipment rather than sizing it. One system for that peak load, that worst case scenario, you can size it.
• 1:29
  So it's based on just the storage temperature and then have an additional system for what I pulled out and added complexity reduces the best, most energy efficient solution throughout the range of the product.
• 1:30
  Trevor: And that's the smart design, right? And that's working with your customers and getting a good understanding of their needs over the year of their company
• 1:31
  Chris: or their product.
• 1:32
  Exactly, they understand their business better than, better than you, well, to begin with, as you're coming in as an outsider. You might start to learn it over time, but 99 percent of the time, they know exactly what they want, and you've got to try and meet their, meet their needs. Infiltration loads. This is the air movement through this space, so generally we refer to it as air changes per hour.
• 1:33
  So the amount of time, the volume of air in that space is going to change on an hourly basis. As it changes, all that air is assumed to be the heat of that temperature of the outside condition as it moves in. Where you need to know the specific heat of the air, available in tables, you can look up online, it stays fairly stable throughout the temperature ranges we operate at.
• 1:34
  With our read volume and our temperature difference. Same equations earlier, but a slight difference here. That m, that mass, is now a mass flow rate. That little dot above means kilograms per second, not just a kilogram total in an SI. Here we have, how we calculate that. We say the read volume, the amount of air changes through that space, which then gives us the total amount of air which moves through in one hour.
• 1:35
  So there may be two air changers for a fairly high use room, might be one air changer that's fairly used to storage. In medical applications, if you had an operating physician doing air conditioning, that can be up to 25 air changers per hour, so very large changeover of air, it's a very large heat. load you need to take into account.
• 1:36
  To go from volume to dense, uh, volume to mass, we need to do the density of the air, which we can find again from tables, and then we divide that by the number of seconds in an hour, which then gives us our flow rate in kilograms per second of air. Our temperature difference, air entering versus the storage temperature inside the room, and then we have our specific heat capacity of the air as well.
• 1:37
  Plug all that in, that gives us our kilowatt value, or BTE value, for our infiltration loads. Main things you can do to reduce that, reduce the number of door openings per hour, reduce the duration of a door opens, if it does open. You can have rapid rise doors, a lot of warehouses use these. It'll detect a forklift coming up to it, it will rise up in a second, forklift passes through, and it will shut very quickly.
• 1:38
  They tend to be insulated as well. You have door curtains, or air curtains above, which will maintain a steady flow of air down across the doorway on the outside. So any of the warm air trying to enter, hits into it, and is bounced back away. Those are the main ones I can think of. You can also have An additional set of doors, um, quite good in, we use them quite a lot in the United Kingdom.
• 1:39
  They're sort of a semi insulated door, and they just plop in and out. As the main door is pulled open, these will bounce back into position once all cliffs or trolleys and trucks go through them. And then lastly, you'll see the PVC strip curtains, which again, it just creates a barrier for the air passing in and out.
• 1:40
  Normally, they tend to be removed by the staff members almost immediately after being installed. I don't think I've ever seen a supermarket or end user not ripping them to shreds within a month of that room being handed over. But, you can only do what you can do. Lastly, we have ancillary levels. As I said earlier, this is the none of the above section.
• 1:41
  Anything which adds a heat load to a room but doesn't fall under what we've just looked at. The main ones, lighting, less so in modern times with LED energy efficiency, energy efficient lighting, PIR sensors to detect if occupants are actually inside the room. Fans, this could be extra fans for volatile gases or more normally the fans on the evaporators which are blowing the air through the room.
• 1:42
  Again with the, and then with the modern addition of EC fan motors rather than AC fan motors, slightly less energy is used, this adds less heat to the which means your equipment size. According to the review it says. Defrost heaters, trim heaters, drain heaters. Again, any other electric or heating element which adds heat to that room.
• 1:43
  Most evaporators will use a defrost heater above a certain size. You can't rely on off cycle defrost entirely in a lot of commercial applications. You may have hot gas defrost. Again, all heat loads which then need to be taken into account for your equipment to then remove once it turns back on. And then people.
• 1:44
  That's the other one. You can also have forklifts or equipment. If it was air conditioning, you may have IT equipment, you may have printers, printing press, newspapers, see the whole reason air conditioning was created was to maintain those environmental conditions for printing. So it goes back a long way.
• 1:45
  I'm assuming the ancillary loads were actually the main reason behind, uh, modern vapor compression refrigeration cycle. I was
• 1:46
  Trevor: at a site, uh, that the same site I was at last week had in floor heat for the freezer. So now that would be considered an auxiliary load, wouldn't
• 1:47
  Chris: it? If it's running, yeah. I'm saying it's that thermal barrier, assuming the insulation allows some of that heat to rise through, then definitely.
• 1:48
  Trevor: And so the thing is, is that. They were running at a lot higher temperature than what I expected, and I think it was too high, personally. Uh, and it was a new system, but running it, I think it was 65 Fahrenheit at that point. I'm like, that's really warm for floor heating, so that would put a lot of extra load.
• 1:49
  So these are things that you need to think about when you're designing them, especially when with CO2 systems, you're going to see a lot more designs where you're doing heat recovery, heat reclaim, parking light heat, in floor heat. And this is important as a designer to understand this. You're going to see a lot of systems, CO2 design
• 1:50
  Chris: with that stuff.
• 1:51
  Definitely. When you say that, I don't think I've ever seen an underfloor TrinHeater more than 10 degrees Celsius or 50 Fahrenheit. Yeah, around 50.
• 1:52
  Trevor: So it's way higher than what I So, so maybe it was just to start up, they were testing, but that was, that's a lot of load into that room. So now your system needs to run a lot more.
• 1:53
  So when you're talking about efficiency, these are things that you need to think about because now a contractor going to set this up or start it up or design it. That could really affect the load of the system and your design. So you need to really have this written out for your customer to give them an idea because they may not think of this stuff.
• 1:54
  And this here is like a fine tuning of the system or maintenance of the system because you designed this great system for your customer, but they run it. 15 degree higher floor temperature. That's a lot of BTUs that they're going to pay for a kilowatts that they're going to pay for, for no, maybe no reason
• 1:55
  Chris: at all.
• 1:56
  Nick, I'd be interested to see if anyone else on the chat on the call has experience of higher temperature, threshold heaters, a fair application, which really demanded that nice and easy appraisal on here. It's just a total of all those individual parts added up. Obviously you may have to take into account.
• 1:57
  diversity that the fans are going to be running when the defrost and trim heaters are. But you may have a scenario where one evaporator is running with that, or one isn't. So you can use your best judgment, make sure you go back through your calculations, make sure you can justify them. That should give you a fairly sensible indication of what the load is going to be for that space.
• 1:58
  Hopefully, software does it for you. But you need to understand what the output is going to give you. I can enter all this in. I might put an extra zero, for example, on quantity per day of mixed products. If it spits out a value ten times greater than it should be, but I'm not aware that it is incorrect, I can then start going out to suppliers.
• 1:59
  Start selecting equipment, which is hundreds of times larger than it needs to be for the space. It's never going to fit. It's never going to get through any feasibility stage, but other cultures actually pick that up. If your customer is only coming to you, they may think actually this isn't feasible. It may completely disrupt their business plans all because of a slight miscalculation you've done in a feasibility stage.
• 2:00
  So making sure you're aware of what results you're expected to get is very important, which is more software. Can't do for you. You need to have that experience and knowledge, that mindset to think actually I need to be able to second guess what this is doing. So hopefully, the one available for free to most people is the Danfoss CoolSelector 2 program.
• 2:01
  It's available as a webpage and as a downloadable software package, but it's very user friendly. You click through, you can input the size of the room. It automatically populates it with a 6 by 5 meter room with 3. 6 meter internal height. Input room conditions, you could go through and select your relative humidity based on psychometric charts, or you can just pick a roughly appropriate value.
• 2:02
  Again, I believe that's automatically populated for you. Input the goods, mixed products, what's going to be stored inside that room. You have your quantity per day, again that's over a 24 hour period. If you need to reduce it so it's a smaller amount over, say, 72 hours, you could change that to a third. If you need to cool that product in a shorter period of time, you'd have to multiply it up and see how much of the actual quantity I'd be moving through on a daily 24 hour basis.
• 2:03
  In that temperature, this would be our T1, at the start of our temperature difference for our products. And then our outlet temperature, or our final cool temperature, would be our room condition. Alongside that, we have our air exchange, our infiltration. You can calculate it based on an exact amount, or you can have an air exchange rate, which is our air changes per hour, which we take earlier.
• 2:04
  Good design for a small, small ish room in a commercial kitchen, potentially. Uh, 45 air changes an hour during a busy process. Cooking, lots of hot air, possibly steam engine in that room, that might be a sensible option. A larger room which is used less, again you may go down to one or two air changes. If you're in a huge warehouse, industrial applications, it may be less than one per hour, er, sorry, one per day.
• 2:05
  You think of the size of those buildings and how small the openings are in comparison, it's going to take a lot of time for all of that air to change over to be replaced with entirely new air.
• 2:06
  Trevor: Yeah, it's crazy in the size of some systems that I'm seeing that co2 transcritical is going in like industrial applications It takes you 20 minutes to walk across the walk in box.
• 2:07
  It's crazy. You can draw, you know, you can drive vehicles through them That's how big they are So going from a small little small one to a big one makes a big difference in the air changes
• 2:08
  Chris: Incredible as well is going with transcritical co2 As before, it was ammonia, and that was the only option people had, or very, very large HFC plow, which, let's face it, is, was never particularly a sensible option for
• 2:09
  Trevor: them.
• 2:10
  And now with the price of the, that HFC, I don't, there's even R 22 ones that I've still even heard about. Just if they have one leak, it costs almost the same amount for a brand new system, the price of these refrigerants that are being delistens and phased out. So these are the things that you want to think about with your customer, because maybe your customer is looking for a low GWP option, like an HFO option, if it can handle that in your certain location.
• 2:11
  But what about down the road? You know, what's the cost of that as refrigerants start to increase in price? So things that you need to think about as a designer.
• 2:12
  Chris: That cliche to my right. Right technology for right application. It's very important that as a specialist, you're going to be relied upon by your end users to have their best interests at heart.
• 2:13
  So you need to select the correct equipment, whether it's not the cheapest option. If it's the best option moving down the road, industrial applications will be operating for 20, 30 years, potentially. You need to make sure it's going to be fit for purpose for that lifespan. Going back to this, you could have your external conditions for air infiltration at 28 degrees.
• 2:14
  There's a box outside, I may be increased, uh, yeah, I suppose. As people expect the world to warm up a bit more, maybe 32, 35, 40. Telling which part of the world you're going could be even higher. And lastly on here we have the heat transfer through panels. You can select the insulating material inside, polyurethane, others, thickness of that panel, the temperature of the surroundings.
• 2:15
  Temperature below floor. This is fairly simple in design because it only allows you to set one temperature to surround the entire box. But you may have scenarios where you have a chilled application on the box and immediately next to it is a frozen application. So instead of having positive heat transfer through all the entire, entire surface, you may have negative.
• 2:16
  So you'd have. You know, a 20, a minus 25 temperature difference on one side versus the other. So that's going to reduce the size of your equipment. But, we'll see you need to have equipment operating in the cold store next to it. And lastly, additional loads, lights, fans, people, other. You might have other, could be forklifts, any other equipment operating inside.
• 2:17
  You have to do your, your survey, your best judgment. And then we have defrost, electric, or natural, natural off cycle defrost, go for electric, calculate what you expect it's going to require. And it should then total up everything and give you your size of equipment. Moving on from that, very briefly, we'll run through how that then plays into expansion valve selection.
• 2:18
  So again, still using Danfoss. Through Tres software, we have a huge number of different valve and applications we can use and select from solenoid valves and mechanical systems, electronic expansion valves, high pressure valves, transcript gas bypass valves, all the stuff which we're going to be able to use and through this program, be able to select and design a system accordingly, we can do most of our part selection using manufacturer software, such as Cooler Selector.
• 2:19
  So, build an expansion valve, we must size it to suit a full heat load. But, also solves it, so it accommodates part loads. We may need to be operating a full load for four hours a year. There may be a part load, 50 percent duty, for 95 percent of the time. We need to make sure it operates across both of those conditions without operating incorrectly.
• 2:20
  It needs to meet the system working pressure rating. Very important with CO2. We're operating at higher pressures than other refrigerants. We need to make sure the body of the barrel is suitable. It's not going to burst. It's designed for that pressure. And just make sure everyone's aware this is our Danfoss cool selector too.
• 2:21
  Yeah,
• 2:22
  Trevor: and it doesn't really matter the manufacturer of the expansion valve, you, you need to reach out to them, get that software because it could be Sporlin, Corel, whoever it is, you got to get into the software and you got to learn that stuff as a designer so you can select it quickly and get the right product for your customer.
• 2:23
  Chris: Exactly. The principles in this apply to all expansion valves, all valve selections entirely.
• 2:24
  Trevor: Because as we said last week is like you got to understand that if you help a design a system for your customer The contractor still need to be able to purchase replacements if things happens like that So these are things that you should be thinking about as a designer So you can make sure your customer is protected in case something does does fail or something happens
• 2:25
  Chris: like that Definitely.
• 2:26
  Again, we're assisting contractors with equipment, which is very much end of life or surpassed end of life. And the equipment which was designed around is no longer accessible. That's the exact part we need to assist. I mean, finding or identifying alternatives, which are going to be able to be fit for purpose.
• 2:27
  I actually maintain my customer's equipment for just slightly longer until it can be replaced. Spanish for valve. On here, we can select our valve type, sort of mid height on the left hand side, we can select our different valve types. For a commercial application on CO2, well Dan Foster's an AKV10P. Make sure we select our refrigerant, just directly above, R744CO2.
• 2:28
  We input our operating conditions at the very top, say we have a 5 kilowatt evaporator, our evaporating temperature of minus 6, we have our, rather than constantly condensing temperature, we'll input our pressure, so from our liquid receiver, we're going to expect probably the lower end of it to be 38 bar, put in some sub cooling, use some soup heat, generally that'll come from your pipe sizing and your equipment selection, it should give us all the information we need then to select an appropriate valve.
• 2:29
  I've clicked on the A KB 10 P five as a maximum capacity of 8.6 kilowatts, so a fair bit higher than our actual maximum GT is. And at the very bottom it will give us a nice little performance curve. So as the valve linearly opens, it shows the cooling capacity that we can achieve, uh, that valve condition.
• 2:30
  So if that valve opens a hundred percent. It would allow for, you know, non kilot securely, 8. we only need 5. So our valve is going to be sitting around that 60 percent opening point for full load. If we state a valve which was too small, it will shoot straight into the oversize or undersize section. So, if we try to achieve 5 kilots, we need a valve 400 percent times larger.
• 2:31
  than we actually achieve from that valve as it is. If we're in too large, however, it'd be the complete opposite end of that spectrum and as any sort of valve opening happens, it's going to wildly over sheet, shoot or under shoot its conditions. Valve too small on this section, not enough refrigerant to actually provide your cooling.
• 2:32
  It's just not enough, not able to get that liquid refrigerant through to reduce that cooling effect. But if it's too large, we have a lack of control of those power loads. As I said earlier, about 5 kilowatts may only be for a few hours a year, and you may be running at 3 kilowatts, particularly on duty.
• 2:33
  But if our fully open valve is operating so far down its possible curve, the tiniest change is going to either undershoot or overshoot those conditions. So when we're selecting our valves, we need to make sure we're checking those operations at lower cooling capacity to simulate that part load. So to do that, I'd go back in, change the cooling capacity, change any of the other aspects, because if that cooling capacity goes down, you may be able to increase your evaporating temperature if you have a floating suction pressure operation.
• 2:34
  All these things you can check to make sure your valve is still suitable for operating in those conditions.
• 2:35
  Trevor: Yeah, and that's, as we know, So doors are often left open, so there has to be some sort of safety margin put in in that room load calculation. So these are the things you need to think about. I always was taught, you know, between 50 and 80 percent if you can get in that range, it's pretty good.
• 2:36
  But now you got to think about the design. Do they have glycol defrost? Do they have a hot gas defrost? Depending on the defrost, you might be doing reverse flow. Uh, straight through or reverse, uh, reverse around the, around the valve. So these are the things you really need to understand when you're designing a system, especially when you have hot gas or, uh, yeah, hot gas
• 2:37
  Chris: design systems.
• 2:38
  You can also have issues here with liquid flood back. If that valve opens or defrost, it goes fully open. It's not able to throttle that refrigerant. It's not going to boil off. You can slide straight back to your compressors. And then you're gonna start to get some real damages. Very important as well of electronic expansion valves is to check that the transducers are operating correctly and, uh, in calibration.
• 2:39
  I had a slight once horrible issue to try and diagnose. Took several weeks, if not months, to find out it was actually the transducer was sticking a certain pressure. Every time I'd come off a defrost, it would spike, send that liquid straight through, and start having compressor issues and oil issues.
• 2:40
  Trevor: And so, Chris, would you, like, what valve, there's lots of different electronic valves out there, there's pulse valves, there is stepper valves, and there's actually now TXV for CO2 systems, uh, which ones do you advise and, and, and why?
• 2:41
  Chris: I always go for stepper valve for improved control. So, but for those who aren't aware, a pulse modulating valve will take a certain amount of time. And if you said 50 percent open, if it's a six second period, it'll open fully for three seconds, close fully for three seconds. Whilst a stepper valve will open proportionally, according if they want 60%, it will wind the spindle open to 50 percent open and allow that liquid through.
• 2:42
  There's more, more control over a stepper valve. They are, they do come with an improved or increased cost. I've not seen one of the, um, TVs yet, the CO2 ones. I'd love to see one in action. I think it's one of the main things which will drive down the size of CO2 systems and make them more obtainable, achievable for small scale scenarios.
• 2:43
  Trevor: I think you'll see them more in the smaller systems, Chris. I don't, in a big large industrial, maybe something that's processed potentially for a supermarket. I don't know for an application like that yet, but I've been seeing more and more tests on them. Different manufacturers have built them. I know Danfoss has theirs.
• 2:44
  I know other manufacturers are designing them, have designed them. Uh, just haven't seen many on the market yet, but this is, this is, What's really cool about the refrigeration industry as we start
• 2:45
  Chris: to grow, right? So yeah, you should be able to simplify retiology again back to a mechanical thing. Solution, it just shows how mature the technology is becoming.
• 2:46
  I think the more we see about it, the more accessible it's going to be to more customers. It's going to dive away from just the industrial application and commercial application is going to move to, to the light commercial, light, industrial, residential, if ever required. I know there's CO2 heat pumps coming out, but just having that familiarity with it, but high pressure, it's not too scary if a normal expansion valve could operate with it.
• 2:47
  It's not too bad. And we're going to see more and more of that, which is cool. Brings us to the end of it. So hopefully after that, people should understand the base of heat loads to cooling systems. Understand, hopefully be able to carry out a little cooling load and understand the principles behind expansion device selection, but again, By signing up to this course, you'll be able to do all that, be second nature, be an expert on it for all applications, not just cold rooms, you'll be able to size air conditioning systems, you'll be able to size your large industrial freezer applications.
• 2:48
  The stuff which will set you apart, uh, step up as an
• 2:49
  Trevor: engineer. Totally. And that's what we're going to be putting into this design course is where you can go design a CO2 secondary system because we're going to see a lot of those coming in the near future. A lot of transcritical boosters, especially here in North America.
• 2:50
  You got to get in a course like this. It takes, it's going to take you to the next level because it's not what they talk about in school. You know, you go do, you Your engineering degree and stuff. We dive into real life, practical application. And by the end of the course, you're going to be able to design your own CO2 equipment, uh, throughout the program.
• 2:51
  So I'm super excited about this, this course, and it's going to definitely take you to that next level in your game. Chris, man, that was awesome. I learned so much, just those little tips and tricks really helping me out, uh, getting my engineering, you know, ideas even better because there's things that I've been thinking about.
• 2:52
  And learning about, cause we're going to get into heat recovery. We'll talk about the plate design, when you should use a plate and when you should use, let's say, uh, that air cooled, uh, exchange or, um, a fin type exchanger, these are so many different designs that I'm seeing out there. I'm seeing actually.
• 2:53
  Uh, a new system design I just seen using, um, a brace plate heat changer as the gas cooler, super cool things. And maybe this could be a design that your customer may need. Any final thoughts, Chris? Cause if you're looking for a design company, reach out to Omega solutions. This is what they do day in, day out, designing systems, helping other engineering firms design their systems, you know, to teach them and grow, grow that, but this is all the stuff that they will be bringing into this refrigeration course.
• 2:54
  Sure, and
• 2:55
  Chris: find us on LinkedIn, find us on our website, or reach out, add us on LinkedIn, find me on there, Christopher Griffiths, connect with me, email me, anything, always happy to, always happy to chat, probably too happy to chat about fridges, but it is a passion. That's what
• 2:56
  Trevor: I love, that's why we hang out, we love this stuff.
• 2:57
  Should we talk about safety margins a little bit in for a room load? So like we do a calculated load, you get that load for that walk in. So we get all the. All the total load. Is there any safety margin you would put in
• 2:58
  Chris: into that? So traditionally you would normally add say 10 percent or even 20 percent back capacity.
• 2:59
  Cause rule was customers are never going to complain that it's too large. Are you going to complain if it's not doing the job? Obviously. Energy costs have skyrocketed, it should be reduced. But also, a lot of the software, even though it likes to not save it and includes it, a lot of it will automatically include a safety margin, so then you're adding safety on top of safety on top of safety.
• 3:00
  This is where the good engineering acumen comes in to identify, well actually, that doesn't seem quite right. If I did a reel a few months ago and it actually seemed a bit oversized, would this one be undersized or oversized?
• 3:01
  Trevor: Do you have any experience with, uh, transcritical units which do not provide sub cooling for the expansion?
• 3:02
  Are there any tips for solid mold? For sure, if you don't have any insulation, bad insulation, any heat gain in that suction, uh, in that liquid line would cause, cause issues at that point. expansion valve. It doesn't matter if it's an electronic expansion valve. You need a full column of good quality liquid to any expansion valve to run
• 3:03
  Chris: properly.
• 3:04
  But I think, oh gosh, any of the slaughtered condensing units, CO2 translucent critical condensing units have inbuilt sub cooling. We've never specified a particular actual mechanical sub cooler for CO2 outside of what's already fitted on a rack, or um, a system which has come Um, prebuilt, uh, as for tips on sizing analysis, such scenarios size as you always have to be fair sizes.
• 3:05
  So it stays within that range of, you know, between, between 40 and 80%. So below or above that. And generally I've never had a system go wrong cheapening to that.
• 3:06
  Trevor: Yeah, I think you're right. That's a design flaw or issue when you don't have the right insulation or you don't have the right amount of sub cooling.
• 3:07
  That should be all in your design, which we get into in our program. We got another question here. Do you use check valves in the suction line of the evaporator for safety reasons? Well, some designs do. So I've seen them where if you have a leak, they'll have a check valve in there. So it'll reduce the amount of leak.
• 3:08
  There is a design, uh, design thing in there where you may add. Add that. And this is the things we'll talk about into the, into the course as a bypass. Uh, so I've seen them in the suction line for, uh, to reduce the amount of, uh, leak loss, if there's a leak in the coil or something like that. Not sure about you, Chris.
• 3:09
  Chris: So we've used some check valves before for reducing risk of over pressurization. For example, it. It allows that liquid in, it starts to build up pressure, it starts to exceed the maximum working pressure of that valve, the evaporator, to make sure that it has somewhere to pass out to get to a pressure relief valve or pressure relief device.
• 3:10
  We have come up with a pass as a cost saving measure, was to have that, into the liquid side of the system. So it uses a liquid pressure relief valve rather than fitting an additional suction pressure relief valve. It reduces the requirements for testing and replacement every five years. Whilst using that safety device or whose safety device is already fitted to the system.
• 3:11
  So there's one one application there. I would rather have a safe, a separate safety device on the system anyway. But if it's not feasible, or if you're retrofitting it to a system, that is one of the opportunities which you could use that for.
• 3:12
  Trevor: Uh, we'll take one last question here. Uh, what if any conditioner given to the age, like panel joints?
• 3:13
  etc. So for the new system, I don't think you'd have to worry about that if you're retrofitting a system and you're trying to reuse panels, that's something you have to consider when you're designing the system. You need to get that information. Like how old are those panels? Are they actually to spec that they were when they were original 10 years ago?
• 3:14
  Probably not. So these are considerations that you would have to take in. I think that's the question that was
• 3:15
  Chris: asked. Yeah, so some, again, I think some software packages already offer this at an AG allowance, so it just adds that additional safety margin that, you know, in 10 years time, as you say, once those panels have allowed a bit of moisture into them, rather than replacing the entire room, it just allows that extra safety margin to continue that.
• 3:16
  operation before it's replaced. We'll see as those panels start to build up moisture, that's going to increase the transmittance through the panel and more heat's going to transfer. And, um, yeah, effectively you would be undersized by the end of it if you kept to that original design.
• 3:17
  Trevor: And these are definitely things you need to think about when you're designing for a retrofit versus a new application all things that we'll talk about in the Refrigeration design course.
• 3:18
  Oh chris. I want to thank you for taking the time to hang out and then next week We're going to be diving into some more Co2 design. This is this is what we're doing each week. I love talking about we're going to get into how to properly Uh, size or apply heat recovery. Another game changing webinar.
• 3:19
  We're going to be diving into this stuff. And we want to just show you the value of learning this stuff as a designer. Because it's only going to make you better. And be able to share this knowledge with your colleagues. To help them grow their knowledge. Chris, thank you so much. We'll see you next
• 3:20
  Chris: week.
• 3:21
  Great. Thanks for having me, Trevor.
• 3:22
  Trevor: I want to thank you so much for
• 3:23
  Chris: hanging out with me and the Refrigeration Mentor Podcast. If you enjoyed this episode, please leave a comment. Let me know what were your key highlights, what you took away from myself or my guests, as well as if you have not subscribed yet, head over to Apple Podcasts or Spotify and subscribe.
• 3:24
  And if you enjoyed this episode, please share with a friend, let your friends know that there are people who care, who want to share the refrigeration information to help them
• 3:25
  Trevor: get to the next level in their career. If you have not been
• 3:26
  Chris: to the refrigeration mentor website at refrigeration mentor. com, go check it out.
• 3:27
  There's
• 3:28
  Trevor: a ton more guest
• 3:29
  Chris: podcasts I've been on as well as the event page. Check out the events page because there's a lot more free trainings. Well, it's paid training to really
• 3:30
  Trevor: help you grow your knowledge
• 3:31
  Chris: base. Super excited. Can't wait to see it. The next refrigeration mentor podcast.
• 3:32
  Trevor: Let's get a conversation
• 3:33
  Chris: going.