MicroGroove® Technology
By Mr. Ghanashyam M. Chendke
Copper tubes are used in the heat exchangers as it has many desirable properties for
efficient heat transfer & durability. Firstly, copper is an excellent conductor of heat as it is
having high thermal conductivity which allows heat to pass through it rapidly. Other
desirable properties include its corrosion resistance, biofouling resistance, maximum
allowable stress and internal pressure, creep rupture strength, fatigue strength, hardness,
thermal expansion, specific heat, antimicrobial properties, tensile strength, yield strength,
high melting point, alloy ability, ease of fabrication and ease of joining. [1]
Due to these properties, copper is widely used in heat exchangers for industrial use,
Heating, Ventilating & Air Conditioning Industries (HVAC) systems.
A research team supported by ICA (International Copper Association) developed the
MicroGroove® technology platform, which utilizes small diameter (≤ 5 mm) inner-grooved
copper tubes. The motto behind the research was to reduce the consumption of copper used in
HVAC systems. [2] [3] [4]
The MicroGroove® technology enhances heat transfer due to grooving the inside
surface of the tube. This gives additional benefits like increase in the surface to volume ratio,
mixing of the refrigerant and homogenizes refrigerant temperatures across the tube. [4][5][6][7]
Weight Reduction:
In a study, it is found that for equivalent 5-kW HVAC heat exchangers, tube materials
in the coils weighed was 3.09 kg for 9.52-mm diameter tube, 2.12 kg for 7-mm diameter
tube, and 1.67 kg for 5-mm diameter tube. So there is nearly tube weight was reduced by
46% when copper tube diameters were downsized from 9.52-mm to 5 mm. [4] [5]
Fig.1. Microgroove Tubes [8]
Fig.2. Microgroove Tubes – a closer view [9]
Design consideration:
When the small diameter copper tubes are used, higher pressures are required to
condense the refrigerant. Working pressure is directly proportional to wall thickness and
inversely proportional to diameter. In other words, for tubes with the same thickness, smaller
diameter tubes can withstand higher pressures than larger diameter tubes. The refrigerant
‘pressure drop’ increases for smaller diameter tubes. More work is required to circulate the
refrigerant through a given length of tube when the pressure drop is high. This pressure drop
can be offset by designing coils with shorter tube lengths. [4] [10]
Refrigerant:
Propane (R290) is an eco-friendly refrigerant, having less pressure requirement as
compared to CO2 with outstanding thermodynamic properties but R290 is extremely
flammable. [4][11] Research has demonstrated that MicroGroove is suitable for R290-charged
room air conditioners because the refrigerant charge requirement is dramatically reduced with
smaller diameter copper tubes. The risk of tube explosions is dramatically reduced as well.
[4] [12] [13]
Benefits of MicroGroove® Technology:
The technology is eco-friendly as Propane (R290) - an eco-friendly refrigerant can be
used safely with lower GWP (global warming potential) and ODP (ozone depletion potential)
ratings. [14]
Energy efficiency and reduced overall system size can be achieved at a lower material
cost with smaller diameter tubes,. Smaller tubes result in reduced usage of tube materials, fin
materials and refrigerants, contributing to overall reduction in system cost. Also, as
mentioned, smaller diameter tubes can operate at higher pressures. Copper tube offers other
advantages, such as corrosion resistance, durability, superior properties and familiar
manufacturing methods. [10]
References:
1.
2.
3.
4.
5.
https://en.wikipedia.org/wiki/Copper_in_heat_exchangers
http://copperalliance.org/core-initiatives/technology/technology-projects/
http://www.microgroove.net/
https://en.wikipedia.org/wiki/Copper_MicroGroove
FAQs: Thirty Questions with Answers about Economical, Eco-friendly Copper Tubes
for Air Conditioner Applications;
http://www.microgroove.net/sites/default/files/overview-ica-questions-and-answersqa30.pdf
6. Microgroove Brochure: http://www.microgroove.net/sites/default/files/microgroovebrochure-game-changer.pdf
7. Microgroove™ Update Newsletter: Volume 1, Issue 2, August 2011:
http://www.microgroove.net/sites/default/files/4315_microgroove_newsletter_august_
2.pdf
8. http://www.appliancedesign.com/articles/94226-smaller-diameter-copper-tubessupport-manufacturing-and-design
9. https://www.researchgate.net/figure/223415444_fig1_Fig-1-Micro-groove-fin-insidetubes-of-copper
10. http://www.copper.org/applications/plumbing/comml_tube/hvac_info.html
11. Microgroove™
Update
Newsletter:
Volume
1,
Issue
3,
December
2011:http://www.microgroove.net/sites/default/files/4473_ica_microgroove_nl_final.pdf
12. Principle of Designing Fin-And-Tube Heat Exchanger with Smaller Diameter Tubes
for Air Conditioner" by Wei Wu, Guoliang Ding, Yongxin Zheng, Yifeng Gao and Ji
Song, The Fourteenth International Refrigeration and Air Conditioning Conference,
Purdue University, July 2012;
http://www.conftool.com/2012Purdue/index.php?page=browseSessions&abstracts=sh
ow&mode=list&search=2223
13. "Developing Low Charge R290 Room Air Conditioner by Using Smaller Diameter
Copper Tubes" by Guoliang Ding, Wei Wu, Tao Ren, Yongxin Zheng, Yifeng Gao, Ji
Song, Zhongmin Liu and Shaokai Chen; The Tenth IIR Gustav Lorentzen Conference
on Natural Refrigerants, June 2012 (GLC)
14. http://copperalliance.org/wordpress/wp-content/uploads/2014/04/ICA-AR2013lowres-web-r2.pdf