Rigid polyurethane (PUR) foams continue to be the dominant insulation
used in domestic refrigerator-freezers. It is estimated that
approximately 75-80 per cent is used in refrigerator-freezers and the
remaining 20-25 per cent is used in other appliances such as display
cabinets, water heaters, portable coolers, commercial appliances and
vending machines...." *
Until recently, primarily CFC-11 has been used to to produce PUR foams
for appliances. The total amount of CFC-11 used for the manufacture of
polyurethane insulating foam in the refrigerator and freezer industry
was approximately 16,000 tonnes in 1994. **
Since the domestic refrigerator-freezers manufacturing industry expects
to complete transition from CFCs (in industrialized countries) in 1995
making the right choice for an alternative blowing agent is all the more
pressing. *** Today there are only two serious contenders being
considered by those moving to CFC-free foam blowing: HCFC-141b and
(cyclo) pentane. **** However, HCFC-141b is not only destructive to the
ozone layer, but is also a potent global warming susbstance. It is
therefore not an acceptable alternative to CFCs.
Cyclopentane has proven to be the optimal replacement for CFCs. It is
already in wide use
in Europe. From an efficiency point of view cyclopentane blown foams
have been found to perform better than even CFC-11 blown foams. As the
1994 UNEP report on the "Elimination of CFC from Domestic Refrigeration
Manufacture" states: " Insulating properties of cyclopentane do not
deteriorate with time as fast as do those of CFC-11 blown foam. In a
standard test cyclopentane foam and CFC-11 foam may both have initial
values of 19 mW/mK. With a few days or weeks of aging cut samples at 60
degrees C or 70 degrees C, the CFC-11 foam will have deteriorated to be
worse than the cyclopentane foam. Its final value may be 2 or 3 mW/mK
worse than the cyclopentane version." *****
In the Nordic region, a major area of manufacture of PUR foam,
conversion to pentane-blowing is almost complete. For example, both
Electrolux and Vestfrost in Denmark have eliminated the use
fluorocarbons for this purpose.
Major refrigerator manufacturers in Japan, such as Matsushita, Sharp and
Sanyo are insulating some of their models with foam blown by
cyclopentane. Most of the major refrigerator manufacturers in Europe,
as mentioned above, have now converted to using only cyclopentane blown
foams.
Vacuum Panels
As an alternative to polyurethane foam, vacuum panels are able to act as
an appliance insulant. These vacuum panels are filled with silica or
fibreglass, or ceramic spacers. Degussa in Germany are developing this
product and the panels, which are manufactured in collaboration with
Electrolux Sweden, have already been used in certain applications.
Vacuum panels in appliances are used by General Electric and
Owens-Corning in the USA. In Japan, Sharp combines the use of vacuum
panels with PUR foam blown with cyclopentane in domestic refrigerators.
AEG in Germany has introduced some vacuum panel insulated fridges.
It is likely that more widespread use of the panels will occur as higher
standards of energy efficiency become mandatory.
The Swiss Ecofridge Project uses vacuum insulation, where the vacuum is
filled with diathomaceous Earth. The thermal conductivity is about 0.005
compared with 0.020 in conventional refrigerator insulation.
** UNEP, "Proposed Three-Year plan and Budget of the Multilateral Fund (1994-1996)", Submitted by the Executive Committee of the Multilateral Fund for the Implementation of the Montreal Protocol at the Open-Ended Working Group of the Parties to the Montreal Protocol: August, 1993, Geneva, p. 11 [return]
*** UNEP, "Proposed Three-Year plan and Budget of the Multilateral Fund (1994-1996)", Submitted by the Executive Committee of the Multilateral Fund for the Implementation of the Montreal Protocol at the Open-Ended Working Group of the Parties to the Montreal Protocol: August, 1993, Geneva, p. 1 [return]
**** United Nations Environment Programme (UNEP), Industry and the Environment: "Elimination of CFC from Domestic Refrigeration Manufacture : Refrigerant, Foam Blowing Agent": [return]
***** United Nations Environment Programme (UNEP), Industry and the Environment: "Elimination of CFC from Domestic Refrigeration Manufacture : Refrigerant, Foam Blowing Agent": Part 2, p.3 [return]