A standard air fluid cooler can be used in free cooling and energy saving applications.
The phrase “custom cooling equipment” usually brings to mind a large, overly complicated and expensive piece of equipment unique in every aspect. This is a costly misconception because the truth is, custom cooling units can save money, save energy and help protect process equipment from excessive wear and tear.
For every specialized application that requires a unique and costly piece of custom equipment, there is a common process that can be made more efficient with a simple tweak to an off-the-shelf cooling solution. Here, several case histories show how this can be achieved.
Figure 1. The manufacturer suggested a loop-in-loop process so the RO water would not have to run through the chiller itself.
Air-Cooled Chiller for Optics
Take the example of a job recently completed for an optics company. The customer needed an air-cooled chiller specially designed to work with a reverse osmosis (RO) water optics process. The optics company contacted a chiller manufacturer, described the need for elaborate customization of the internal piping and components of the air-cooled chiller to ensure the integrity of the RO water, and asked for pricing.
Changing the internal components was both costly and unnecessary, the chiller manufacturer explained. Instead, the manufacturer suggested a loop-in-loop process so the RO water would not have to run through the chiller itself (figure 1). The loop-in-loop process would utilize an off-the-shelf, five-ton air-cooled chiller with a small amount of specialized piping for the process side, and a shell-and-tube heat exchanger mounted to the chiller frame to maintain the RO water process. By adding a few standard components, the out-of-the-box approach to the process allowed for a significant cost savings for the optics manufacturer.
Keep in mind that a loop-in-loop design is not limited to RO water applications. This process design is used regularly on deionized water (DI) applications, food-grade applications and with all sorts of corrosive chemical and hazardous material cooling. Loop-in-loop designs also are used in more commonplace applications where large temperature drops are required. In these cases, the heat exchanger is used to add a large amount of surface area, allowing the chiller to handle large-differential process temperatures. This saves the customer from having to buy an expensive chiller and tank system.
Saving Energy with Free Cooling
Figure 2. Employing a free cooling process design a facility can save money by reducing utility consumption and saving energy.
Free cooling, a method that uses low ambient air temperatures - by way of an air fluid cooler - to cool process water, is making a buzz in the process cooling world, and for good reason. Simply put, when the ambient temperatures rise in the summer, a chiller is used to cool the process; likewise, when the temperatures fall in autumn, winter and spring, the chiller is bypassed and the air fluid cooler is used at much lower operating costs due to the energy savings (figure 2). Employing a free cooling process design, a facility can save money by reducing utility consumption and saving energy.
Of course there is a tradeoff - initial investment cost goes up. When free cooling is employed, a chiller and air fluid cooler must both be purchased, which raises the cost of the job significantly. However, if you can muster the foresight and reach out to an expert in the field to do the energy-saving calculations, you could find that these units typically have a payback of one to two years.
For instance, a free cooling system was designed for a glass manufacturer in Pittsburgh. Before free cooling, their glass manufacturing process involved the consumption and elimination of a large amount of city water used to cool the glass when it came out of the ovens. Not only was the company being charged for all of the water they consumed but the sewage authority began charging them for the water that they were discharging because it was such a large volume.
A closed-loop, free cooling system was recommended following a thorough examination of the process as it would be the total cost of ownership solution. The completely integrated cooling system included a chiller, a fluid cooler, two pumping stations, a thermocouple-operated three-way valve and dual 2,000-gal holding tanks (figure 3).
Figure 3. The completely integrated cooling system for the glass manufacturer included a chiller, a fluid cooler, two pumping stations, a thermocouple-operated three-way valve and dual 2,000-gal holding tanks.
The process now consumes far less water, and they are discharging almost none. The process water is recycled through the cooling loop and stored in the holding tanks. In the summer, the water is cooled by the chiller; during most of the rest of the year, the water is cooled by the air fluid cooler. Their process is more efficient and they are saving real money today, resulting in a short return on investment.
Free cooling requires more upfront cost compared to the purchase of just a chiller, but this type of equipment can last up to 15 years. With the cost of utilities going up, especially for water, a free cooling consultation is a good idea.
Protecting a Process by Customizing a Chiller
A city water bypass valve assembly is used to protect many processes from catastrophic failure, and the cost of this important assembly is minimal when compared to the cost of a new chiller. A city water bypass valve assembly, sometimes called an emergency bypass valve, is mounted on the inlet of a standard, off-the-shelf chiller. It is designed to automatically switch from using the cooling fluid recirculating in the chiller to using city water to cool the process. On city water bypass assemblies, the solenoid valve manifold is wired “hot” to a standard chiller alarm so that when the alarm on the chiller trips or the hot contact loses power, the valves go into action and switch to city water. By now you might ask why someone would want to use city water to cool their process when they have just bought an air-cooled chiller - fair question.
An off-the-shelf air cooled chiller was customized with a city water bypass valve assembly.
The answer is maintenance or component failure. As reliable as the best chillers are, they are still composed of many components that are not bulletproof. Applications that benefit from a city water bypass are those that are common but vital. For instance emergency bypass valve assemblies are used on most of the chillers sold to the medical field, specifically for MRI and LINAC machine cooling. In this environment, there is the real possibility of a fuse blowing and shutting down the power to the chiller. If this were to happen to a chiller cooling an MRI machine while it is in use, personal injury could occur and the million dollar MRI machine would be destroyed. If the chiller is cooling a process that runs 24/7, the addition of a bypass valve assembly will allow it to continue uninterrupted in the event of maintenance. As you can imagine, there are many applications where this minor customization will save money by protecting the process machinery.
Chillers customization is about creating a solution that is as economic as it is efficient. Customers are regularly surprised that a custom solution using off-the-shelf components is an option when they are expecting the price tag that comes with building a specialized chiller from the ground up. “Custom” does not always mean expensive. “Custom” does not mean specialized design held together by a wing and a prayer. Custom chillers save money. Custom chillers improve process efficiency.