More heat can be transferred using less copper coil material by making the tubes smaller

Introduction

• Conventional ³/₈’’copper tubes were so entrenched in coil technology for many decades there was little thought of change
• Yet the efficiency of a.c units depends on cooling the refrigerant temperature as quickly and as close as possible to the ambient outdoor temperature in the condenser and conversely raising its temperature to the indoor temperature in the evaporator.
• This depends on the efficiency of the coils more than anything else.

Environmental concerns prompted the phase out of refrigerants with high ozone depletion potential (ODP) and global warming potential(GWP)

• The Carrier Corporation spent hundreds of man-years on R&D and introduced 7mm tubing in 2006
• In 2008 Goodman introduced SmartCoil technology which is a 5mm diameter inner-grooved tube that greatly increases the efficiency of the system

Inner Grooves

• Experiments show that even for tube diameters 0f 4mm or less, inner grooves or microfin patterns can further improve the local heat transfer coefficients
• The exact patterns of the inside tube surface enhancements remains a subject of intense research
• ICA refers to the technologies associated with smaller diameter inner-groove tubes as Microgroove technology

Laboratory Confirmation

• In a series of experiments Professor Guoliang Ding of SJTU measured the local heat transfer coefficients (HTOs) inside the tubes and found that the HTOs were significantly increased by reducing the tube diameter
• In a condenser tube, for example , the heat energy moves outward through the flowing refrigerant ; and across the insulating boundary layer of the slowly moving refrigerant near the inside surface of the tubes
• These results show how more heat can be transferred using less coil material by making the tubes smaller