Design reducing refrigerant charge by 27% and safety standards at GL 2012

By Past Member, Jul 09, 2012, 16:31 3 minute reading

A comprehensive comparison of safety standards, novel designs resulting in lower refrigerant charge and new measures addressing the concentration of leaked refrigerants were presented at the 10th Gustav Lorentzen Conference. in this final article provides an overview of discussed papers.

Safety standards for hydrocarbon refrigerants – Asbjørn L. Vonsild

Compliance with the coming version of ISO 5149 draft makes it possible for system manufacturers to sell large hydrocarbon systems across the world, including EU. That is one of the conclusions in Vonsild’s paper where he addresses a major barrier for using hydrocarbon refrigerants - navigating the safety standards. He explores and compares the differences and similarities between EN 378:2008, ISO 5149 (draft standard) and ASHRAE 15:2010. The focus of the paper is on the charge limits and the components design requirements. Vonsild also concludes that systems using hydrocarbon refrigerants and built according to EN 378, will comply with ISO 5149 draft provided that they:

  • obey the charge limits of ISO 5149 draft
  • use zone 2 compliant components
  • use relief valves that are large enough to comply with EN 378 and ISO 5149 draft

Experimentally validated micro-channel heat exchanger performance and charge predictions used to compare charge reduction potentials of some refrigerants – Yadira P. Fuentes and Pega Hrnjak

Researchers from the University of Illinois presented a validated model of an air-cooled micro-channel that was used to compare the charge reduction potential of various refrigerants. It was found that ammonia, followed by R744 and propane, has the highest potential for charge reduction. The criterion for evaluation was a reduction in internal volume until refrigerant side pressure drop caused 1% COP reduction over zero pressure drop case. According to the results, natural refrigerants ammonia, R744 and propane proved to have higher charge reduction potential than HFCs R134a, R1234yf and R410A. The reason for ammonia being the best option is its high latent heat of vaporization that reduces mass flow for the same air side conditions and light vapour.

Developing low charge R290 room air conditioner by using smaller diameter copper tubes – Guoliang Ding, Tao Ren, et al

Also this paper addressed the safety concerns regarding hydrocarbon refrigerants by designing components that help reduce refrigerant charge. A novel design of heat exchangers for R290 with 5mm diameter copper tubes resulted in reduction of total refrigerant charge by 27% while maintaining the performance of split-type room air conditioner. In their study, a simulation-based design method was developed and a knowledge-based evolution method was applied to optimize the design of a heat exchanger with smaller diameter tubes. Authors see R290 as a suitable drop-in refrigerant for existing R22 systems and the reduction of refrigerant charge as a suitable design strategy to address the safety concerns.

Safety concept for hydrocarbon refrigerants in split air conditioner – Daniel Colbourne, Rolf Hühren and Asbjørn L. Vonsild

In this article, options for certain safety concepts for medium refrigerating systems such as split-type air conditioning systems using R290 or R1270 are discussed. Combination of sensing methods and mitigation actions is proposed to extend the range of system sizes without diminishing the level of safety. The authors show that two-thirds of the refrigerant charge can be prevented from entering the inside space, thus avoiding concentrations of refrigerant exceeding 50% of lower flammability limit. Depending on the system, the operating mode and the cost, various sensing methods (e.g. gas detection, system parameters, liquid level sensor, flow meter) are used to activate the mitigation actions (e.g. initiate full ventilation, terminate compressor, solenoid/shut-off valves, redirect dumpers). In conclusion, provided some of the proposed measures are adopted, relatively large split systems using hydrocarbons as refrigerants can be designed and constructed to achieve a high level of safety.


By Past Member

Jul 09, 2012, 16:31

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