Cooling India: hydrocarbons for supermarkets and at high ambients

By Sabine Lobnig, May 27, 2011, 12:15 4 minute reading

The latest issue of Cooling India, India’s premier magazine on the cooling industry, includes contributions on alternative refrigerants such as hydrocarbons, suited to India’s high ambient temperature conditions, as well as on lessons learnt and progress made with rolling out hydrocarbon cooling systems throughout the retail estate of Waitrose in the UK.

Alternative Refrigerants for High Ambient Temperature Conditions, N. Cox, Earthcare Products

Moving away from using HCFC R22 in line with its Montreal Protocol commitments, India has many reasons not to widely adopt HFC refrigerants with high Global Warming Potential, the most important being that there are many other more efficient refrigerants, even for India’s higher ambient temperatures.

“… by using hydrocarbon refrigerants, it is possible to attain higher critical temperatures to those achieved by R22. The hydrocarbon R290, for instance, has a critical temperature of 97°C and R432A (80.0% R1270/20.0% E170) has a critical temperature of 99.37°C whilst matching the capacity characteristics of R22 even at higher ambients”, writes Nicholas Cox.

In his article, Cox provides an introduction to several alternative refrigerants, including hydrocarbons and hydrocarbon blends, that are well suited to high ambient conditions:
  • Blends of hydrocarbons R290/R600a, for example, have been used extensively as an alternative to CFC R12 and HFC R134A and conversions of car air conditioners. The 52%/48% R290/R600a blend designated R436B by ASHRAE is well suited to high ambient applications.
  • Dimethyl ether (RE170, DME), which has been extensively adopted as the replacement for R12 and R134a in propellant applications, makes a better refrigerant than R290/R600a blends as it has no temperature glide and does not separate during leakage. R510A, a RE170/R600a (88.0/12.0) blend has been shown to have superior performance in some R134a replacement applications such as water coolers, and has been proposed for MAC applications.
  • The greatest success of hydrocarbons has been the use of R600a (isobutane) in domestic refrigerators, while the author assesses that R600 (butane) should prove a commercially attractive refrigerant for chiller manufacturers.
The author concludes that for high ambient applications, the optimum replacement for HCFC R22 is R432A, and for HFC134a it is R510A. However, further research is required to identify the optimum replacement for the HCFC R123, which is well suited to high ambient temperature applications due to its very high critical temperature of 183.7 °C. Used in conventional vapour compression systems, HCFC R123 (NBP 27.0 °C) could simply be replaced with isopentane (NBP 27.7 °C). In centrifugal compressor applications, however, the molecular mass is more important in determining capacity and lower molecular mass can only partially be compensated for with higher vapour pressure.

Frascold’s Propane Compressors at the heart of Waitrose Hydrocarbon Cooling system

UK food retailer Waitrose makes use of integral refrigerated cases on the retail floor, running on the hydrocarbon propene (R1270), using chilled water/glycol as the condensing medium. This is supplied by roof-top-mounted Geoclima chillers based on Frascold compressors running on R290 (propane).

The Geoclima chillers use a combination of Liquid Pressure Amplification (LPA) technology with a floating head pressure, high efficiency aluminium coils and traditional glycol-based free cooling to significantly increase operating efficiency. The roof-top-mounted chillers provide a supply of chilled water or glycol mixture at between 10°C and 18°C, with a typical return temperature 6°C higher, ensuring optimum performance and efficiency of both integral cases and chiller. Typically, at ambient temperature below 16°C, compressors are switched off and the chillers run in free-cooling mode, providing significant energy savings.

The Frascold compressors at the heart of the propane chiller were selected by UK specialist Klima-Therm following evaluation trials with machines from a number of manufacturers. Some winning features included the resilience of the compressor to liquid return and the availability of a variable speed option that further improves efficiency and compressor control. As a result, Frascold’s semi-hermetics are now the default choice for use in Geoclima’s Waitrose chillers.

The compressor manufacturer has also modified the position of the pressure transducer, which is now mounted on the body of the compressor itself rather than positioned remotely, reducing pipe work and connections and further improving safety and reducing the potential for leaks. Waitrose reports zero leakage in the trial supermarket set up monitoring the performance of the system.

Overall, the use of hydrocarbon refrigerants improves the energy efficiency of individual systems by between 10 and 20%, with further gains of around 10% delivered as a result of heat recovery and store-wide integration. When added to the 100% containment of refrigerant, the CO2 emissions reduction in stores to date is running at around 32%.

The retailer will be installing the new refrigeration solution in all new stores and major refurbishments of existing stores, while it is also now being introduced to the new smaller format Waitrose convenience stores. The aim is to convert all Waitrose UK stores by 2020, with about 55 hydrocarbon-based systems due this year.

About Cooling India

Launched in 2005, Cooling India is India’s premier magazine on the cooling industry dedicated to air conditioning, refrigeration and building automation with a large reach across India and overseas. It is published by Chary Publications, one of the oldest publishing houses in India dedicated to the energy sector and now diversified into publishing magazines on HVACR, lighting and medical equipment. For more information about subscriptions contact nafisa@charypublications.in


Contact Information

If you would like to contact Earthcare Products for any enquiries, you may send a request to Nicholas Cox directly.

If you would like to contact Frascold for any enquiries, you may send a request to Luciana Beretta directly.


MORE INFORMATION

By Sabine Lobnig

May 27, 2011, 12:15




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