Florida is a high-corrosivity region due to several factors, mainly due to marine atmosphere with high airborne salinity, and falls into the range provided for an ISO C3 category classification and even C4 for coastal areas. For C3 category environments, aluminum coils like microchannel heat exchangers without protective coating are unsuitable but are often used because of their low cost compared to coils with electrophoretic epoxy-coated ones. Traditional uncoated copper-aluminum coils demonstrate even worse corrosion resistance in C3/C4 regions.
Condensation management is essential to ensuring the efficient function of heat exchangers and critical for the correct operation of evaporators.
Hydrophilic topcoats, surfaces tending not to adsorb water or be wetted by water, are effective in environments of excessive condensation, as they enable water to flow easily off the heat exchanger surface by virtue of lowered surface tension, thereby enhancing heat transfer performance in wet and frost conditions. At the same time, hydrophilic coatings protect heat exchangers from the corrosive effect of water and exhibit fine performance in providing protection in salty environments.
Kaltra has launched new twin-slab microchannel condenser coils that maximize performance and efficiency in air-to-refrigerant applications. Previously employed and evaluated in Kaltra air-cooled chillers, this solution achieved superior performance results and is now available for end customers and OEMs.
High global warming potential refrigerants for refrigeration systems are being phased out because they are one of the culprits of climate change, while, at the same time, nearly 50 alternative refrigerants are classified as environment-safe.
Due to the high and constantly growing market demand for compact microchannel coils, Kaltra expands its manufacturing capabilities of serpentine heat exchangers by installing new tube bending machines and assembly lines equipped with semi-automatic core builders, fin mills and fin inserting machines.
In carrying forward work on microchannel evaporator designs, Kaltra presented its successive generation of coils intended for both indoor and outdoor use in air conditioners and air-source heat pumps. Thanks to the ingenuity of its dual-circuit arrangement, new evaporators offer maximum efficiency while at the same time dealing with challenges of operation in frosting conditions.
Recently, Kaltra developed special series of microchannel condenser coils tailored for the most challenging refrigeration applications in reliability – refrigerated containers and trailers.
Aluminum alloys, surface treatments and thickness of tube walls of these coils have all been specially sourced for application to contribute to system reliability and extended lifespan.
Propane (R290) is a naturally occurring hydrocarbon used successfully in industrial refrigeration for many years received attention from designers, contractors, operators, and retailers to reduce greenhouse emissions. An indication of the increasing acceptance of propane is its adoption by many key customers from large supermarket and shopping mall chains to franchise food stores and minimarts at gas stations throughout the world. The latest trend in this market segment is adopting microchannel heat exchangers – condensers and evaporators.
This month, Kaltra announced the completion of a service project for the replacement of condenser coils for the chilled water production plant of a Tier-III data center in Munich, Germany. More than 120 original heat exchangers reaching the end of service life have been replaced with Kaltra coils providing a long lifespan and additional corrosion protection.
Microchannel coils are here to stay. Their use is rapidly spreading to a variety of HVAC applications. Microchannel heat exchangers are stronger, lighter, offer higher heat transfer compared to other types of air-to-refrigerant coils. They are smaller in size and also in internal volume, resulting in a refrigerant charge that is significantly reduced.
At Kaltra, the importance of top-notch service has always been seen as essential in the delivery of components. Kaltra’s forward-focused strategic approach, which always led to a successful relationship with our customers right in the early stages, ensures our competitive advantages in the long run and a key to our successful businesses. In the framework of this strategy, Kaltra continually strives to improve its service to customers.
Brazed all-aluminum microchannel coils perform superior heat transfer efficiency and capacity at the compact size compared with the conventional tube-fin heat exchangers. Another important factor of growing of microchannel heat exchanger popularity is the high corrosion resistance of aluminum, which is, however, achievable through the careful selection of aluminum alloys, surface treatments, and other protective measures.
Air-conditioning and refrigeration industries have been evolving rapidly over the past decades. The latest energy efficiency regulations and phase-out of ozone-depleting refrigerants spur further development of air-to-refrigerant heat exchangers, making microchannel heat exchangers the better alternative to conventional heat exchangers for the majority of HVAC manufacturers. Heat transfer technology based on microchannel coils offers the largest potential for improving energy efficiency, reducing refrigerant volumes required, while also providing a number of other benefits.
Microchannel heat exchangers have been broadly used in automotive applications due to their advantages of compactness, low weight, and high efficiency. There are numerous heat exchangers designs based on microchannel technology with folded fins and flat tubes which are connected to manifolds. These designs are predominantly used for automotive radiators, condensers, and, more recently, automotive air conditioning evaporators.
Although modern microchannel heat exchangers made from highly corrosion-resistant alloys and able to withstand any type of corrosion, be it galvanic, formicary, or other types, even without any protective coating, there are some harsh conditions under which additional treatment may extend their service life and guarantee trouble-free HVAC equipment operation.
Corrosion, the deterioration of metals and alloys through a physical and/or chemical reaction with the environment, is expensive. Heat exchangers used in HVAC equipment, specifically condenser and cooling/heating coils are exposed in the environment, and this can lead to corrosion, failures, and performance degradation of the equipment in the cases of improper heat exchanger protection in corrosive locations.
Compact heat exchangers, especially those of serpentine design, are widely used for cooling in many industries, products and systems, from consumer products to IT cooling to military applications. In recent times, with the advances in microfluidics and progress in manufacturing, compact microchannel heat exchangers are becoming widespread. The principal idea behind using microchannel heat exchangers is their potential for enhanced heat transfer capabilities. The use of such heat exchangers enables the transfer of large amounts of heat while benefiting from high heat transfer coefficients.
Single-phase heat exchangers are widely used today for a variety of cooling and heating applications and in different types of equipment. These include free cooling systems, dry coolers, air conditioners, and more, where the most common media is water or glycol mixtures. Microchannel coils in practice became the norm in condenser applications, and, more recently, microchannel heat exchangers became an alternative to finned tube coils that used traditionally for water applications.
For over three decades now, air-to-refrigerant microchannel heat exchangers have been successfully used in a number of industries, including automotive and chemical processing. More than a decade ago, microchannel heat exchangers were introduced in the HVAC industry; but it must be noted that requirements concerning heat exchangers and their operating conditions in refrigeration and air conditioning systems are different from those applicable in the automotive and other industries. Because of this, the first adaptations of microchannel heat exchangers to HVAC applications, principally as condensers, were not entirely successful.
In recent times, microchannel heat exchangers (MCHE) have started to attract attention from the HVAC industry as an alternative to fin/tube evaporators. The enhancement of heat transfer and compactness are major advantages of microchannel heat exchangers, as well as reduced refrigerant charge, lower airside pressure drop, and a reduction in materials used for manufacturing. Under current tight regulations of energy efficiency, microchannel heat exchangers are appreciated by many leading manufacturers.
Corrosion is the deterioration of metals arising from the chemical reactions between a metal and the surrounding environment. In HVAC equipment, such as air-cooled chillers, condensers, and dry coolers, corrosion of the heat exchangers may lead to performance and efficiency losses, as well as to equipment failures.
In order to avoid unwanted corrosion, microchannel heat exchangers and chilled water system, in general, must be properly protected based on environmental conditions.
Alcoil announces the issuance of US Patent No. 9,459,057 and European Patent EP 2 948 725, which relates to an improved and advanced refrigerant evaporator design. The patented technology is used as an air-to-refrigerant microchannel heat exchanger to cool air or reject heat in residential, commercial or industrial evaporators and heat pump systems.
Kaltra offers the latest heat transfer technology for electronics cooling, cooling of laser devices, medical appliances, and other small cooling applications with serpentine heat exchangers based on microchannel technology.
Air-based free cooling uses low-temperature ambient air as a cooling medium for chilled water systems, thus providing significant opportunities to generate energy savings. The more time the chilled water system can operate in the free cooling mode, the higher the energy savings it can deliver.
The HVAC and process industries are making a transition to microchannel heat exchangers. This is evidenced by the extensive use of microchannel condensers by major HVAC manufacturers and many smaller OEMs manufacturing cooling and refrigeration equipment. Significant energy efficiency improvements drive the trend, the need for smaller equipment footprints and weight, conversion to lower GWP refrigerants, and the ongoing rise in the cost of copper.
Microchannel coils are becoming quite popular as an alternative to bulky finned tube heat exchangers. For the desired capacity, microchannel coils are smaller in size resulting in less refrigerant charge in the system, offer higher heat transfer performance, and lower weight. However, until now, microchannel coils used only to a very limited extent in HVAC units exposed to freezing conditions like heat pumps.
The efficiency of air-cooled chiller is dictated by the condensing temperature, which may be decreased with increasing heat transfer performance of the condensing coil. Microchannel heat exchangers have become popular in chiller applications due to better thermo-hydraulic characteristics in comparison to conventional finned tube heat exchanger designs. The most straightforward way to improve heat exchanger performance is to increase its face area by combining two microchannel coils in V form.
by Steven Wand
Although not traditionally used in industrial process applications, microchannel designs may offer advantages over traditional coil technologies in most process cooling applications. Long considered a coil technology primarily used in commercial and residential air-conditioning, microchannel coils are being used by more manufacturers who have discovered how they can improve process cooling applications.
by Lance Robinson
I vote for fix. Anytime you can fix a condenser as opposed to replacing it, is a good day for all in the repair business. Less time = more money. Customers are happier and all around better vibe. Replacement of perfectly good coil makes no sense. Instead make the fix in less than 5 minutes with a propane torch and a few simple instruments all HVAC techs have on hand.
Approximately 10% of heat exchanger failures are connected with leaks caused by formicary corrosion. Organic compounds remain on copper tubes during manufacturing and fabrication of the HVAC equipment, are able to advance to formicary corrosion only with the simultaneous presence of moisture, oxygen, and acids. Read more
by Carter Stanfield
Aluminum coils are here to stay. Not only have they been applied successfully for years by Kaltra in their spiney fin condenser coils, they have also been used for years as evaporator coils in refrigerators.
Since the introduction of the next generation all-aluminum microchannel coils, their acceptance in the process and HVAC industries has been nothing short of remarkable! The microchannel coil advantages are the future and rapidly becoming the norm because of the many benefits they provide in new HVAC equipment.
Field tests for evaluating microchannel heat exchangers with variable fin pitch (VFP-MCHE) performance have been started this week. VFP-MCHE design features variable fin pitches and dimensions, tube geometries, port shapes, and the location of fins and tubes within the same heat exchanger core.
All-aluminium microchannel heat exchanging products are now being widely used in the HVAC industry: they provide higher performance, smaller size, features and capabilities not found in traditional fin/tube heat exchangers.
WHO WE ARE
Kaltra is a customer-focused developer and supplier of reliable, energy efficient thermal management equipment and solutions.
From the professionalism of our research and development engineers to the wide experience of our service team, we are dedicated to delivering you the best service possible.