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FEATURE
INCORPORATING COLD CHAIN using hydrocarbons , particularly R290 in Australia , Germany and the UK . However , they do not seem to have become commercialised on a wider scale .
This article describes the development of a prototype R290 system for use in a medium-sized RRV . The starting point for the development was a baseline R404A system and it involved a number of stages , as illustrated in Figure 1 .
Since the primary concern is overcoming the flammability hazard of R290 , the majority of the steps address risk minimisation . This involved reduction of refrigerant charge , development of a leak control and safety system , improving leak tightness , identification of potentially flammable zones and subsequently addressing potential sources of ignition within those zones .
If the failure modes and effects analysis ( FMEA ) and quantitative risk assessment ( QRA ) yield any concerns , prior steps are re-evaluated in order to help minimise the risk further ; these steps are consistent with the approach given in EN 1127-1 . When the risk is believed to be sufficiently low , final compliance against a safety standard is carried out followed by drafting of guidance for users and finally applying the prototypes for field trials . In addition to safety matters , performance ( capacity and efficiency ) is also important . Since these parameters are closely linked to the charge reduction process , they were carried out simultaneously .
Figure 1 : Summary of the main stages in the development of an R290 transport refrigeration system .
Final remarks
A prototype refrigeration system for RRVs has been developed . Major aspects of the development were significantly reducing the refrigerant charge and adopting a special leak control and safety system . A risk assessment indicates that the level of flammability safety of the prototype should not present any concerns . Now that the prototype has been developed and tested , it is undergoing field trials , so far with favourable results .
The motivation behind the project is to reduce the emissions of greenhouse gases . An initial assessment of lifecycle emissions suggests about 16 % lower diesel consumption — which translates directly into reduction in ‘ indirect ’ emissions — and on account of the negligible GWP of R290 an elimination of ‘ direct ’ global warming emissions . Overall , the R290 model is expected to generate only 34 % of the global warming emissions ( in terms of tCO 2
-eq) compared to the R404A baseline model .
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Acknowledgements
The authors would like to acknowledge the German Ministry for Environment , Nature Conservation , Building and Nuclear Safety and the Deutsche Gesellschaft für Internationale Zusammenarbeit ( GIZ ) GmbH and Transfrig Ltd for giving permission for publication .
Overall , the R290 model is expected to generate only 34 % of the global warming emissions
( in terms of tCO 2
-eq ) compared to the R404A baseline model .
Checking in on the project
The field trial of the joint venture between Transfrig and GIZ on the R290 prototype successfully kicked off on 29 November last year at Transfrig ’ s premises in Linbro Park , Johannesburg .
The next step is for Transfrig and GIZ to approach suitable customers for an extended field trial with 10 units . In January , Daniel Colbourne visited South Africa again to check up on the project and talk to various key role players in the industry about this research . CLA
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34 www . coldlinkafrica . co . za COLD LINK AFRICA • March | April 2017