1. Hot or chilled water coils are still water coils. There is really no difference between hot water coils and a chilled water coils in construction. Hot water coils are usually 1 or 2 rows and chilled water coils are usually 3 to 12 rows deep.
Contact us to discuss your requirements of Water-Cooled Chiller System. Our experienced sales team can help you identify the options that best suit your needs.
2. The vast majority of chilled water coils are constructed from either 1/2″ OD tubes or 5/8″ OD tubes. A lot of that depends on the tooling of the original equipment manufacturer and what is more economical. Either size can be used and substituted for each other, which makes replacing your coil that much easier.
3. 1/2″ Tubes are on 1.25″ center to center distance. 5/8″ tubes are on 1.5″ center to center distance. For example, if a chilled water coil has a 30″ fin height, there will be (24) 1/2″ tubes per row or (20) 5/8″ tubes per row. The tube area of the coil is remarkably the same. They are almost interchangeable.
4. The quality of the coil often times is directly tied to the tube thickness. Many installations have water not treated properly or tube velocities that are too high. There are few perfect installations in real life. Increasing the tube wall thickness on a chilled water coil is a great way to ensure longer life.
5. Fins make great filters! Of course, they are not designed to be filters, but it happens. You can make any coil cheaper by making them 14 fins/inch with less rows rather than 8 or 10 fins/inch. Just remember that deep coils are very difficult to clean. Cheap is not the way to go most of the time!
6. Fins are designed for maximum heat transfer. They are much more complicated in design than they appear to be when looking at the chilled water coil. They are rippled on the edge to break up the air. They are corrugated throughout the depth of the fin. The tubes are staggered from row to row and the fin collars are extended. All of this to maximize heat transfer. Unfortunately, the byproduct of this is the fins can end up being great filters. Be careful in the design of any chilled water coil.
7. Fins are aluminum for a reason! They give you great heat transfer at an economical cost. You need a compelling reason to switch to copper fins as copper is very expensive, and you’re likely to double (or maybe triple) the cost of the coil. Coatings are popular for this very reason.
8. Many chilled water coils are built with 304 stainless steel casings. The casings are stronger, they last longer, they are stackable, and it’s fairly inexpensive. After all, what is the point of building the best coil possible and have the casing disintegrate over time around the coil? Sometimes, it’s money well spent!
9. Circuiting the coil is the tricky part of any coil. Circuiting is nothing more than the number of tubes that you want to feed from a header. There are two rules. You must keep the water velocity over 1 foot/second and below 6 feet/second. 3-4 feet/second is optimum. The second is the number of tubes that you feed must divide evenly into the number of tubes in the coil.
10. Replacing your chilled water coil is easy. Rarely do you have to worry about the performance. When you replace a 20 year old coil, it is dirty and the fin/tube bond is not good. The coil is probably operating at 1/2 of its capacity at best. When you put a new coil on the job, your performance will automatically be terrific. Your main concern is now making the sure the coil physically fits in the space allowed. And always have this in the back of your mind: Smaller is always better than too large. Smaller you can always work with, whereas too large makes for a very ugly and expensive coffee table.
There you have it – everything you need to know about chilled water coils. Interested in learning more, please reach out to Capital Coil & Air! We look forward to the opportunity to be your coil replacement specialists!
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Top 5 Reasons HVAC Coils Prematurely Fail
Tags: Chilled Water Coils, Commercial Coils, cooling coils, DX Coils, Evaporator Coils, HVAC Coils, Quick-ships, replacement coils, water coils
– Albrand Velthuizen, 24/05/2019
You may already know that chilled water is the icy lifeblood of the HVAC system. But why is it so important? And which parts of the system need special attention? How does one keep the installation healthy and in good shape, preventing problems? Here’s what you need to know.
The temperature range of a chilled water system is 6 to 12 °C or 5 to 11 °C, with a temperature difference of six degrees. Chilled water is produced by a chiller – in other words, it’s created artificially. The chiller can be seen as the heart of the system, and the chilled water pipes as its arteries. The pipes weave throughout the entire vessel, from the tender garage to the wheelhouse and from the bowthruster room to the radar systems inside the mast.
The water inside the pipes is a mixture of water and glycol, a product that prevents the water from freezing. The higher the proportion of glycol in the system, the lower the freezing point of the mixture: for example, a 10% glycol content lowers the freezing temperature to -4°C. Besides protecting the water from freezing, glycol also protects the pipes themselves: being slightly greasy, it leaves a film on the inside of the pipes, protecting them against corrosion.
The chilled water acts as an energy carrier as it flows into the heat exchangers of fan-coil units and cooling coils of air-handling units and air conditioners. Here, it pulls heat out of the environment and brings it back to the chiller, where it is cooled. Pure water naturally has a high specific heat capacity (the amount of energy that needs to be removed to lower its temperature). The more glycol there is in a system, the lower its specific heat capacity will be.
In addition to specific heat and temperature, the capacity of a cooling coil depends on the flow of the medium, that is, the amount of chilled water that flows through the pipes. When a fan-coil unit in a tender garage, say, no longer cools, this can be a sign of a flow problem. You may be able to prevent this by adjusting the installation to correct functioning. A properly commissioned installation ensures that chilled water is well distributed among the users as well as preventing cavitation and noise problems.
One of the most frequent problems with chilled water is air inside the system, which manifests as small bubbles collected in pockets. These prevent the flow of water and leave the heat exchanger dry so that it no longer cools. This is especially common after a new vessel has just been delivered and the chilled water still contains a lot of air. Placing automatic air filters prevents this from happening. It’s important to note that the position of the filters is crucial to their correct operation. Air is lighter than water, so it will tend to collect in more elevated parts of the system. To ensure the best results, the filter needs to be placed on the highest deck.
Although the chilled water lines are thoroughly flushed before operation, there will always be some smudge inside the lines, for example coming out of heat exchangers mounted inside air-handling units. Using filters prevents particles in the chilled water from causing wear to components or blocking narrow pipes. Available filters range from solid-pipe filters to advanced filtration units which even filter air and keep pH levels up.
Like to know more about filtration units or some of the other topics mentioned in this blog? Check out the links below.
Albrand Veldhuizen | Commissioning Engineer
Albrand has been working at Heinen & Hopman since 2006. He has worked himself up to the position of Commissioning Engineer and nowadays he is stationed at one of the largest yacht builders in Germany. During his many years working onboard numerous luxury yachts, he has developed a great expertise in HVAC systems for superyachts.
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