Safer, greener, cheaper route to ultra-cold freezers

Scientists at Brunel University London have engineered a new method to build the next generation of freezers capable of reaching temperatures as low as - 180°C by using advanced cryogenically cooled heat pipe technology.

Explained Dr Hussam Jouhara, of Brunel’s Institute of Energy Futures: “At the heart of the new system is the concept that what we needed was to be able to efficiently transfer cold.

“The cold in our design comes from liquid nitrogen. But unlike conventional cold storage using the liquefied gas we don’t need to physically transfer the nitrogen. The cryogenic heat pipe is literally just moving the cold.

“In safety terms this has major implications as in the US alone eight deaths a year are attributed to nitrogen asphyxiation. Our innovations mean the gas tanks can be situated safely outside in the open air.”

The system’s green and money-saving credentials come from a highly efficient energy recovery process which means a potential of up to 50 per cent reduction in liquid nitrogen use compared to conventional equipment.

“Liquid nitrogen is expensive in both cash terms and energy consumption to produce,” added Dr Jouhara. “And quite rightly there are strict health and safety rules because of the attendant dangers of asphyxiation. The Brunel system has no such special requirements.”

Once installed heat pipes are regarded by engineers as a “fit and forget” technology as they have no moving parts and require no routine maintenance.

The research work is done with direct funding from the industrial gases giant Air Products PLC successfully passed laboratory trials, Dr Jouhara is partnering with Air Products to commercialise the new freezer technology.

Initial real world users are likely to be for medical storage and the team will be working with the NHS Blood and Transplant Service to develop prototype freezers to rapidly cool and store plasma made from donated blood.

Also a strong demand from facilities which store cord blood or eggs or sperm or other biological materials at very low temperatures.

A litre of liquid nitrogen expands to 700 litres of odourless, non-toxic colourless gas at room temperature. The risk to health comes if the nitrogen displaces the oxygen in an enclosed space.

The danger from very low oxygen levels is that you become unconscious after two breaths – you do not even have time to realise that something is wrong. If you remain in that atmosphere for a few minutes you die.

Multiple fatalities are common in such circumstances because a passer-by or colleague, seeing someone collapsed, rushes into the room to render assistance but succeeds only in becoming a casualty. One in ten of recorded nitrogen asphyxiations were would-be rescuers.










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