Video Transcript – Creating the most efficient ice rink

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Text: Team CFM
Jonathan Bowman, Robert Herat, Adam King, Matthew Mahoney, Andrew Knutson

Hey everyone and welcome to team CFM’s project video. And to start
things off I’m going to give a brief overview of our project. Our project consists of the theoretical design of the chiller systems and HVAC systems for the facility pictured here, which is a theoretical ice skating facility in the Treasure Valley. So everything’s going to be designed for our elevation and atmospheric conditions. This facility contains two Olympic sized ice skating rinks as well as a smaller facility in the middle that would contain locker rooms, a dining area, and administrative areas. Here is a blueprint picture, and the blueprint shows the two ice rinks in their orientation as well as the mechanical areas in the back and what they would contain. And let’s move on to discussing the specifics of chiller systems.

All right well now the first topic to discuss when you’re talking about chiller systems is whether or not you’re going to go with a direct or indirect system. What’s pictured here is a direct system and you can see the refrigerant is being pumped directly from the condenser unit through a reservoir and then into the ice rink itself. This is the most efficient way to go about doing things because your refrigerant is coming in direct contact with the surface you need to chill and you’re not losing any sort of energy to a heat exchanger. However, this sort of system can be problematic because due to refrigerant toxicity such as ammonia if you have any sort of leak in your system it becomes a hazard to everyone in the building and therefore the trade-off of efficiency versus safety becomes an issue.

Now moving on to an indirect system we can see that now instead of directly pumping our refrigerant into the piping underneath the ice rink we are putting it through a heat exchanger first where it exchanges its heat with a neutral solution such as brine or glycol which is much safer overall than directly pumping your refrigerant. Granted you’re going to lose some efficiency because you have to exchange the heat between your refrigerant and your intermediary but you have to do much less safety precautions because all of your refrigerant can be contained inside a mechanical room which is much safer than directly pumping your refrigerant underneath the ice rink where you’re going to have the majority of people staying.

Speaking of refrigerants let’s talk about those next. First off we have ammonia which has been the industry standard for several decades now. It’s highly efficient – it’s ubiquitous – however as i’ve discussed previously there is some issues with it being a hazard to those in the facility especially if you have any kind of piping that goes directly into an occupied area in the building. It’s hard to beat its efficiency though. However, in a recent decade or so there’s been a new player on the block, and that player is CO2. CO2 has been seeing a lot more use especially above the 45th parallel because of its efficiencies in those areas because it’s colder during more of the year where CO2 tends to shine through. In areas down here in the Treasure Valley we’re gonna have better luck with ammonia because ammonia is more efficient during the summer months when it’s hotter.

Now we can talk all we want about CO2 versus ammonia or direct versus indirect. That’s lingo that we can throw around. N ow we got to talk about real world analysis and real world analysis is the cost analysis because almost always the solution that people want to go with is the solution that costs the least. Lowest operating costs usually correlates to highest efficiencies and that’s what we’re aiming for with this project is high efficiency, low operating cost.

Now looking at this chart here CO2 direct and CO2 indirect both have really high operating costs compared to ammonia, almost double. Now seeing that ammonia has a operating cost that is actually slightly lower for direct is telling because it’s yes highly efficient because of the efficiency of direct systems. But you notice how up there we have estimated that’s because nobody that we could find does a direct ammonia system due to the safety issues. Almost every single system that we could find uses an indirect ammonia system and now the cost of direct versus indirect is only slightly higher for indirect given the theoretical nature of direct. So at this point in time we are moving forward with a ammonia indirect system and at this stage we are currently moving towards figuring out the actual specifics of that system and what the costs and design is going to look like.

Thank you for your time.