As you’ve heard us say before, there’s no more efficient way to transfer heat than steam. But in order to turn the combustion of your boiler’s furnace into steam, and put that steam to work, that heat energy has to pass through several different media. It does that through the use of a heat exchanger, which is where all the action takes place.
Because steam is so versatile and useful, it can be used for a multitude of purposes. That’s why there may be several different parts of a typical boiler system that can be classified as heat exchangers. The same steam that is keeping your factory operating can be the same steam that’s heating up the water in the employee locker rooms, and keeping the administrative offices warm during the winter. Here’s how the different types of heat exchangers do their thing.
KEEP IT MOVING
When you operate a boiler, your end goal is to start with a flame, and turn that into a process. How that happens exactly will depend on what kind of boiler you have, a water tube or a firetube boiler. But the process of exchanging heat will still happen in the heat exchanger.
In a fire tube boiler, an assembly of tubes passes through a tank full of water. Hot combustion gases flow through those tubes, which heat up the tube surfaces and pass the heat through them to the water that’s flowing around the tubes. In a water tube boiler, the water flows through tubes which are themselves surrounded by hot combustion gases, absorbing the heat as they pass. In both cases, the part of the boiler where the heat flows from the combustion gases to the water is the heat exchanger.
HOT AND COMFY
While the term heat exchanger refers to the area in your boiler where the heat transfers from medium to medium, it’s also the place where some of the steam generated by the boiler may be used to create hot water. For example, if you have a large residential building, the boiler in the basement may be sending steam to the radiators in each apartment to provide heat in the winter. But that same boiler may also be creating the hot water that the residents use to wash their dishes and their clothes, or take baths and showers.
Why, then, don’t you just siphon off some of the hot water you already have in the boiler tank? Two main reasons. First, the water in the boiler tank isn’t considered potable. In order for water to be converted into steam efficiently, and in order to prevent corrosion and scale in the boiler tank from forming, the boiler’s feedwater is treated with an array of chemicals. That makes the water in the tank unsuitable for drinking, bathing, cooking, or cleaning.
The second reason you can’t just yank away some boiler water when you want to do the dishes has to do with pressure and demand. Steam boilers operate under pressure, and they have to maintain that pressure to create steam. If someone in the apartment building turned on their dishwasher, the boiler would lose water and, more importantly, pressure.
Since the volume of water in the boiler tank has to be kept at a consistent level for safe steam production, there can’t be a random demand on that water that could come at any time. In this instance, another kind of heat exchanger is needed to take the heat from the boiler water and transfer that heat into a source of clean, potable water. That’s where the steam heat exchanger comes in.
A steam heat exchanger works by passing a supply of clean water, usually from the utility line, through pipes around which hot steam is circulating. As the water flows through, it absorbs the heat from the steam and becomes hot itself. Now it’s ready to help someone draw a bath, wash some towels, or do the dishes.
If you’re losing efficiency to an old or outdated heat exchanger, or if you suspect you have a leak, let one of WARE’s highly trained technicians take a look and get it fixed. If you’re in the market for a new boiler with modern efficiency and performance, we’re here to help with that, too. Of course, if you’d like to learn more about heat exchangers or any other part of your boiler, WARE’s Boiler University has an array of classes available online and in person. Whatever you need, just let us know. We’re here to help.