A brief glance at the latest trends in cooling technology and coil design show a more intensified focus on energy efficiency and comfort.

Nearly 110 years have passed since the first installation of air conditioning in 1902. Although Thermodynamics is widely considered a complete science today, new designs of heat pumps, air conditioners and refrigerators are flourishing, with an increased interest in the design of air conditioning and refrigeration (ACR) products in recent years.

A CLIMATE OF INNOVATION

Many factors have contributed to the new environment of innovation in the ACR industry today, with the following being the primary reasons:

  • Phase out of high-ODP and high-GWP refrigerants
  • Use of eco-friendly refrigerants being encouraged or made mandatory
  • Higher energy efficiency standards
  • Focus on sustainable development
  • Computer simulation of components and system performance
  • Responsiveness to needs and wants in the marketplace

The phasing out of popular CFC and HCFC refrigerants has been a major factor in spurring innovations in cooling technology in the past 20 years. Likewise, energy efficiency and sustainability have necessitated invention. End-users have their eyes on energy efficiency ratings, and OEMs are highly motivated to use less material in their products.

Computer modelling is now commonly used to simulate total system design. Consequently, decisions about refrigerants, coils and components are made with the assistance of increasingly accurate performance simulations.

ADVANCEMENT IN COIL DESIGN

Redesign of the coil has seen the use of smaller diametre copper tubes with inner-grooves increasing the internal heat transfer coefficient and raising COPs. Such improvements in coil performance may also be favourable for the use of new refrigerants, less materials, higher operating pressures (due to smaller diametre tubes) and variable refrigerant flow (due to an increase in the number of branches).

Also, system design has dramatically changed for the better with the use of smaller diametre inner grooved copper tubes in coil designs gaining ground.

NATURAL REFRIGERANTS

Natural refrigerants, such as carbon dioxide and propane are fast becoming more attractive to OEMs and end-users for ACR and heating applications as technology has advanced. Also known as R744, carbon dioxide is used as a refrigerant in a growing number of applications, ranging from vending machines and refrigerated supermarket display cases to ice skating rinks.

Another natural refrigerant under consideration for use in air conditioning systems is propane. Known as R290, propane is an eco-friendly hydrocarbon (chemical formula C3H8) with outstanding thermodynamic properties that make it well-suited as a refrigerant for residential air conditioners.

The advantages of copper tubes in these applications include high thermal conductivity, corrosion resistance and strength. Smaller diametre copper tubes have even higher burst strengths, and allow for lower overall refrigerant volumes.

The use of copper is a proven technology with a well-established supply chain, including a network of trained installers with the know-how to ensure safety and reliability.

COPPER – A VIABLE OPTION

Another factor influencing the design of air conditioning and refrigeration systems is new published research on copper’s efficacy against the spread of fungi in air conditioning systems. OEM companies, such as the Chinese air conditioning manufacturer, Chigo, and Hydronic in France, have already developed all-copper products, expressly for their antimicrobial properties.

Webinar

MicroGroove, the manufacturer of ACR coils with smaller diametre copper tubes, has announced its upcoming Webinar. The details are given below:

Tuesday, March 27 at 1pm ET
Presented by: The News and Appliance Design.
Speaker: John Hipchen, President, Exel Consulting Group

The use of all-copper coils is not new, but their use specifically to inhibit the growth of fungi and bacteria is a recent development that is expected to be an important factor in designing innovative air conditioning and refrigeration products.

It has been found that bio build-up on the coil may be reduced by using all-copper coils, thus helping to maintain high levels of energy efficiency for longer times and avoiding energy-efficiency drop off over a period of time.

THE DECISIVE FACTOR

Perhaps the most important factor driving the development of new products is a better understanding of attitudes towards comfort and refrigeration in different climates and cultures. ACR product developers are responding better to the real needs and wants of end- users in the built environment. They are right-sizing air conditioning and refrigeration products to allow for precise temperature and humidity control in specific zones, while trying to eliminate waste. The result is that end-users will enjoy healthy, eco-friendly products that deliver cooling capacity with high energy efficiency when and where it is most desirable.

Taking a closer look at copper
The air conditioner manufacturer, Chigo, has revealed that it has reduced the tube weight in one of its air conditioning systems by 30%. It has claimed that the weight reduction was achieved simply by switching to smaller diametre copper tubes in the evaporator and condenser coils of the system. The tube diametre was reduced from 9.52mm to 5mm in the condenser, and from 7mm to 5mm in the evaporator, it said.

According to Chigo, the air conditioner is a split system with a cooling capacity of 2,500 W and a COP of 3.2, or EER of 10.9. It needs to be noted that the energy efficiency ratio (EER) in units of Btu/hr per W is obtained from the coefficient of performance (COP) in units of W/W by multiplying by 3.412 since 1 W=3.412 Btu/hr.]

The ground-breaking antimicrobial copper coil air handling unit harnesses the antimicrobial properties of copper in hospital applications. It is made in Europe by French manufacturer Hydronic in association with Centre d’Information du Cuivre, Laitons et Alliages (CICLA).