Industrial facilities and power plants Copper alloys are extensively used as heat exchanger tubing in fossil and nuclear steam generating
electric power plants, chemical and
petrochemical plants, marine services, and
desalination plants. The largest use of copper alloy heat exchanger tubing on a per unit basis is in utility power plants. These plants contain surface condensers, heaters, and coolers, all of which contain copper tubing. The main
surface condenser that accepts turbine-steam discharges uses the most copper. Today, aluminum-brass, 90%Cu-10%Ni, and other copper alloys are widely used in tubular heat exchangers and piping systems in
seawater,
brackish water and
fresh water. Aluminum-brass, 90% Cu-10% Ni and 70% Cu-30% Ni alloys show good corrosion resistance in hot de-aerated seawater and in
brines in multi-stage flash desalination plants. Fixed tube liquid-cooled heat exchangers especially suitable for marine and harsh applications can be assembled with brass shells, copper tubes, brass baffles, and forged brass integral end hubs. Copper alloy tubes can be supplied either with a bright metallic surface (CuNiO) or with a thin, firmly attached oxide layer (aluminum brass). These finish types allow for the formation of a protective layer. The biofouling resistance of Cu-Ni alloys enables heat exchange units to operate for several months between mechanical cleanings. Cleanings are nevertheless needed to restore original heat transfer capabilities.
Chlorine injection can extend the mechanical cleaning intervals to a year or more without detrimental effects on the Cu-Ni alloys. Further information about copper alloy heat exchangers for industrial facilities is available.
Solar thermal water systems Solar water heaters can be a cost-effective way to generate hot water for homes in many regions of the world. Copper heat exchangers are important in solar thermal heating and cooling systems because of copper's high thermal conductivity, resistance to atmospheric and water corrosion, sealing and joining by soldering, and mechanical strength. Copper is used both in receivers and in primary circuits (pipes and heat exchangers for water tanks) of solar thermal water systems. Various types of solar collectors for residential applications are available with either direct circulation (i.e., heats water and brings it directly to the home for use) or indirect circulation (i.e., pumps a heat transfer fluid through a heat exchanger, which then heats water that flows into the home) systems. In an evacuated tube solar hot water heater with an indirect circulation system, the evacuated tubes contain a glass outer tube and metal absorber tube attached to a fin.
Solar thermal energy is absorbed within the evacuated tubes and is converted into usable concentrated heat. Evacuated glass tubes have a double layer. Inside the glass tube is the copper heat pipe. It is a sealed hollow copper tube that contains a small amount of thermal transfer fluid (water or glycol mixture) which under low pressure boils at a very low temperature. The copper heat pipe transfers thermal energy from within the solar tube into a copper header. As the solution circulates through the copper header, the temperature rises. Other components in solar thermal water systems that contain copper include solar heat exchanger tanks and solar pumping stations, along with pumps and controllers.
HVAC systems Air conditioning and heating in
buildings and
motor vehicles are two of the largest applications for
heat exchangers. While copper tube is used in most air conditioning and refrigeration systems, typical air conditioning units currently use aluminum fins. These systems can harbor bacteria and mold and develop odors and fouling that can make them function poorly. Stringent new requirements including demands for increased operating efficiencies and the reduction or elimination of harmful emissions are enhancing copper's role in modern
HVAC systems. Copper’s antimicrobial properties can enhance the performance of HVAC systems and associated
indoor air quality. After extensive testing, copper became a registered material in the U.S. for protecting heating and air conditioning equipment surfaces against bacteria,
mold, and
mildew. Furthermore, testing funded by the
U.S. Department of Defense is demonstrating that all-copper air conditioners suppress the growth of bacteria, mold and mildew that cause odors and reduce system
energy efficiency. Units made with aluminum have not been demonstrating this benefit. Copper can cause a galvanic reaction in the presence of other alloys, leading to corrosion.
Gas water heaters Water heating is the second largest energy use in the home. Gas-water heat exchangers that transfer heat from gaseous fuels to water between 3 and 300 kilowatts thermal (kWth) have widespread residential and commercial use in water heating and heating boiler appliance applications. Demand is increasing for energy-efficient compact water heating systems. Tankless gas water heaters produce hot water when needed. Copper heat exchangers are the preferred material in these units because of their high thermal conductivity and ease of fabrication. To protect these units in
acidic environments, durable coatings or other surface treatments are available. Acid-resistant coatings are capable of withstanding temperatures of 1000 °C.
Forced air heating and cooling Air-source heat pumps have been used for residential and commercial heating and cooling for many years. These units rely on air-to-air heat exchange through evaporator units similar to those used for air conditioners. Finned water to air heat exchangers are most commonly used for forced air heating and cooling systems, such as with indoor and outdoor wood furnaces, boilers, and stoves. They can also be suitable for liquid cooling applications. Copper is specified in supply and return manifolds and in tube coils.
Electronic systems Copper and aluminum are used as
heat sinks and
heat pipes in
electronic cooling applications. A
heat sink is a passive component that cools
semiconductor and
optoelectronic devices by dissipating heat into the surrounding air. Heat sinks have temperatures higher than their surrounding environments so that heat can be transferred into the air by
convection,
radiation, and
conduction. Aluminum is the most prominently used heat sink material because of its lower cost. Copper heat sinks are a necessity when higher levels of thermal conductivity are needed. An alternative to all-copper or all-aluminum heat sinks is the joining of aluminum fins to a copper base. Copper heat sinks are die-cast and bound together in plates. They spread heat quickly from the heat source to copper or aluminum fins and into the surrounding air. Heat pipes are used to move heat away from
central processing units (CPUs) and
graphics processing units (GPUs) and towards heat sinks, where thermal energy is dissipated into the environment. Copper and aluminum heat pipes are used extensively in modern computer systems where increased power requirements and associated heat emissions result in greater demands on cooling systems. A heat pipe typically consists of a sealed pipe or tube at both the hot and cold ends. Heat pipes utilize
evaporative cooling to transfer thermal energy from one point to another by the evaporation and condensation of a working fluid or coolant. They are fundamentally better at heat conduction over larger distances than heat sinks because their effective thermal conductivity is several orders of magnitude greater than that of the equivalent solid conductor. When it is desirable to maintain junction temperatures below 125–150 °C, copper/water heat pipes are typically used. Copper/
methanol heat pipes are used if the application requires heat pipe operations below 0 °C. ==New technologies==