considering issues of tribology to address sustainable development

Encuentro de Tribología (20, 21 Setiembre 2001)
Universidad de Bournemouth
Mark Hadfield
School of Design, Engineering & Computing
Bournemouth University, Studland House
12 Christchurch Road, BH1 3NA. UK.
Fax: +44 1202 503751
Sustainable development has evolved to incorporate social, economic and
environmental dimensions. The environmental dimension requires a whole life cycle
approach to minimise the aggregate impact of a product by exploring alternative
routes. For this reason, knowledge on all the life cycle phases of a product is required
but the difficulty lies in integrating the different compartments into which engineering
has developed (tribology, refrigeration, etc.), each of which being maintained and
progressed independently.
This presentation focuses on a case study: domestic refrigerators. Refrigerant
tetrafluoroethane (HFC-134a) has an impact on the mechanical system in terms of
wear, life cycle and energy consumption. HFC’s half the direct contribution
chlorofluorocarbons (CFC’s) have on global warming. However, this scientific
assessment assumes that all production of this compound is equivalent to emissions
and therefore fails to gauge the impact of other influential life cycle phases. Any
ensuing indirect emissions are not due to the chemical action a compound has as a
greenhouse gas but due to the energy-related effect resulting from the combustion of
fossil fuels needed to energise equipment which uses this compound.
Refrigeration compressors are lubricated by oil, some of which dissolves in
the refrigerant. The use of HFC-134a required the traditional mineral oil used with
CFC’s to be replaced with a synthetic lubricant to maintain the compatibility the oil
has with the refrigerant. This is likely to influence a number of product attributes
including heat transfer characteristics at the heat exchangers as well as the refrigerant
properties. Moreover, this change in lubricant has to overcome the effect chlorine in
CFC’s has to form laminate layers on metallic surfaces and which reduce friction.
This case study demonstrates that tribological analysis has a role in assessing
the environmental impact of design change. The in-use environmental impacts can
have a significant contribution compared with other phases during a product life
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