Keeping evaporator and condenser tubes as clean as possible is one of the most important factors of maintaining chiller efficiency. If interior tube surfaces become fouled with scale, mud, algae, sludge, or other contaminants, even in small amounts, thermal resistance causes the chiller to work harder and energy efficiency plummets. In fact, inefficient chillers can expend as much as 30% more in energy, according to the DOE.
Manufacturers typically recommend cleaning condenser tubes annually. Evaporator tubes should be cleaned about once every three years for closed systems, more often for open systems. There are two basic methods of cleaning chiller tubes: chemical and mechanical. In chemical tube cleaning, an acid solution is circulated through tube bundles to break down or soften calcium, lime, rust, and other deposits. This process should always be followed by a thorough mechanical cleaning. While chemical cleaning can be quite effective in many cases, it can be costly and time consuming.
Mechanical cleaning is effective for removing accumulate materials such as mud, sand, and algae from smooth-bore tubes, and there are several means with which to do it. The old-fashioned rod and brush method is sometimes still used, but is time and labor intensive and is only moderately effective. The chiller tube cleaning gun is a good alternative for lighter deposits in which brushes, rubber bullets, or scrapers are propelled through tubes using compressed air and water, or high-pressure water alone, to remove deposits. Rotary tube cleaners utilize a motor to rotate a flexible shaft that can be fitted with a variety of brushes and other tools, and this method is affordable and very effective. They are the best choice for internally-enhanced chiller tubes, which employ spiral grooves to provide better heat transfer.
Many new chillers come equipped with online tube cleaning systems, which can also be retrofit onto existing chillers. One type utilizes brushes that are trapped in plastic baskets attached to both ends of each tube. The direction of water flow is periodically reversed, causing the brush to travel to the opposite end of the tube. Another type of system features sponge balls that circulate through the tubes and keep surfaces clean. With proper water treatment, automatic systems can be extremely effective and eliminate the need for tube cleaning. Though retrofits can be expensive to purchase and install, payback periods are typically less than two years.
For more information about chiller tube cleaning, please contact PJM Mechanical Contractors, Inc., at (609) 496-8696.