The ancient Greek oracles, priestesses through whom the gods supposedly relayed their divine advice to mortals, were renowned across the Greek, and subsequently the Roman, Empires. The most famous was the Oracle at Delphi, where the priestess, known as the Pythia, seemingly possessed in a trance by Apollo, would deliver advice and prophecies to those properly prepared by the temple priests after, of course, having made a suitably substantial offering.

A theory, first suggested in the 19th Century, proposed that the Pythia’s utterances were made under the influence of hydrocarbon gases such as ethylene seeping from a vent opening into the cavern, the Adyton, where she sat on a tripod. A 2002 multi-disciplinary, peer-reviewed study, published in the Journal of Clinical Toxicology, supported this idea, although it has been challenged. Interestingly, visitors to the Oracle in Antiquity remarked upon the sweet smell, which would be consistent with ethylene. 

This gas, known to our industry as the natural, low temperature refrigerant, R1150, can affect human consciousness and was used as an anaesthetic in the mid-20th century, but was later replaced by safer, non-flammable and more potent fluorinated products.

Following the recent release by OpenAI of the ChatGPT AI app perhaps we now have the modern equivalent of the Delphic Oracle which we can access on our laptops without the long and dangerous journeys faced by the ancient Greeks. In response to typed questions, ChatGPT scans the internet for information to provide coherent and consistent answers, which can be mini-essays depending upon the query, raising concern in the media that less-conciencious students would use the app to write their assignments.  

But can the app be trusted to provide accurate answers? I feel it timely to explore the scope and limitations of ChatGPT when consulted about refrigerants. 

Simply typing in ‘natural refrigerants’ produced the following reasonable reply: 'Natural refrigerants are substances that are used as a coolant in refrigeration and air conditioning systems that are not harmful to the environment. Examples of natural refrigerants include carbon dioxide (CO2), ammonia (NH3), and propane (C3H8). These refrigerants have a lower global warming potential (GWP) compared to synthetic refrigerants such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). Natural refrigerants are considered to be a more sustainable alternative to synthetic refrigerants as they do not contribute to ozone depletion or global warming.'

Personally, I think the term ‘synthetic’ can be equally applied to the so-called ‘natural’ refrigerants which are just as much products of the chemical and oil/gas industries as the fluorinated refrigerants. Typing in ‘HFO refrigerants’ evoked the following, which also wouldn’t be considered incorrect if presented in a student essay: 'HFO (hydrofluoroolefin) refrigerants are a type of synthetic refrigerant that are being developed as a more environmentally friendly alternative to HFC (hydrofluorocarbon) refrigerants. They have a lower global warming potential (GWP) compared to HFCs, which means that they have a smaller impact on climate change. HFO refrigerants are also non-ozone depleting, which means that they do not contribute to the depletion of the ozone layer.'

Again reasonable, but since the answer lacks detail I next tried a more specific query – ‘What HFOs are being used as refrigerants?’

The answer that came back was: 'Some of the HFO refrigerants that are currently being used or considered for use as refrigerants include:

• R-1234yf: This is a HFO refrigerant that is being used as a replacement for R-134a in automotive air conditioning systems. It has a GWP of less than 1, making it one of the lowest GWP refrigerants available.
• R-1233zd(E): This is a HFO refrigerant that is being used as a replacement for R-404A in commercial refrigeration systems. It has a GWP of less than 1, making it one of the lowest GWP refrigerants available.
• R-1234ze(E): This is a HFO refrigerant that is being used as a replacement for R-410A in air conditioning systems. It has a GWP of less than 1, making it one of the lowest GWP refrigerants available.

It's worth noting that these refrigerants have been developed as a short-term solution to phase-out of HFCs, they are not necessarily the final solution, and more research and development are needed to find long-term solutions.'

While I accept that description of R1234yf, I find the comments on R1233zd(E) and R1234ze(E) surprising since they have significantly higher boiling points than the products they are claimed to replace. As regards the final comment, I suspect that manufacturers who have invested in these products do not consider them as 'short-term' developments, but I guess ChatGPT is designed to reflect the range of opinions expressed on the Internet.

My follow-up question was: ’Which company is offering R-1233zd(E) as a replacement for R-404A?’

Which generated the reply: 'Several companies are offering R-1233zd(E) as a replacement for R-404A, some of the examples are:

• Honeywell: They are one of the leading suppliers of R-1233zd(E) refrigerant and offer it under the brand name Solstice® ze.
• DuPont: They are offering R-1233zd(E) under the brand name Suva 1233zd.
• Chemours: They are offering R-1233zd(E) under the brand name Opteon XP40.'

Citing both DuPont and Chemours suggest ChatGPT is unable to process historical changes where earlier information is superseded by later developments, as well as making other obvious errors.

I then tried a simple request for a specific piece of information: ‘What is the boiling point of R-1233zd(E)?’. 

The answer according to ChatGPT: 'The boiling point of R-1233zd(E) is -28.9°C or -20°F at atmospheric pressure. It is a hydrofluoroolefin (HFO) refrigerant that is being used as a replacement for R-404A in commercial refrigeration systems. It has a global warming potential (GWP) of less than 1, making it one of the lowest GWP refrigerants available. It is a low pressure refrigerant, which makes it suitable for low-temperature refrigeration systems. It should be used with care, as it requires special handling and training due to its low boiling point. It's important to note that this information might vary depending on the supplier, so it's always best to check with them for the latest information on the product.'

The inaccuracies in this reply need no further comment. A further question wrongly suggested that the structure of R1233zd(E) is CH2=C(CH3)2CF3 and is non-flammable. 

In summary, ChatGPT is a remarkable and entertaining development giving clear replies to simple questions based on information plucked from the internet in comprehensible, if somewhat pedestrian, English.  

Unfortunately, questions about refrigerants, can give grossly erroneous answers but, to be fair to OpenAI, they expect to improve the app as feedback is provided by users. At present students of refrigeration certainly should not depend upon it for information, nor should we expect ACR to feature articles with a ChatGPT by-line anytime soon.  Human intelligence still reigns supreme over artificial intelligence, at least in this area. Maybe the Pythia gave her prophecies under influence of the hydrocarbon gas, ethylene, but I wonder whether she was any more accurate than ChatGPT?

This article and much more can be found in the March 2023 issue of ACR News: