ACProf,
Ultimately, you are entitled to your opinion and I respect that.
I was trying to engage in respectful and polite discussion of the facts. If anything I said came across as a personal attack then I apologize as that was not my intent.
Please consider that I could have posted anonymously, not revealing who I was and my link to HyChill. If I wanted to manipulate the readers of this forum and do a sales pitch I would have been better off posting as though I was a well-informed and satisfied user - but I deliberately chose not to.
We can examine and postulate every which-way at the properties of refrigerants and still be at disagreement - as has been occurring since the first widespread commercial application of HC's in vehicle AC since the early 1990's. We can each conduct our own risk assessments and come up with different conclusions - as has been occurring since the first widespread commercial application of HC's in vehicle AC since the early 1990's.
Why? Because all the above assessment approaches are only estimates and are therefore not conclusive, and they *can* be affected by our initial conditions or underlying bias (in either direction), a fact I would trust you agree with.
Because the stakes were so high (e.g. fluorocarbon industry possibly losing their monopoly position) and these theoretical assessments were 'flexible' so to speak, these theoretical approaches were taken to attempt to discredit HC safety right from the outset. Not surprisingly, natural refrigeration proponents countered with their own models and reasoning.
The truth or error in the theorizing can be seen quite clearly in the now over 20 years of commercial application in the vehicle aftermarket. It is a FACT that HyChill (which is just one the HC suppliers in Australia) is used in between 10% and 15% of the automobiles currently on the road in Australia. This is based on a simple comparison of our sales volume versus fluorocarbon sales volume. In the USA, the absolute quantities are many times larger (you have a much larger population), although the market share is lower. The total usage is well in excess of 20 million car user years.
Over the entire period there has not been one single cabin fire incident on the roads, stationary or moving.
Accordingly, real world data trumps theories, because it removes the bias. The real world data supports my argument. I invite you to produce solid data to the contrary.
I absolutely agree with you that HC's are more flammable than R-134a, but this cannot, by any reasonable standard, be sufficient argument to support a claim that hydrocarbons are point-blank unsafe in motor vehicle AC.
Regarding your HC vs R134a cabin challenge:Obviously, you would win the challenge according to the implicit simplifications in your challenge versus the real world of vehicle AC. But what does it prove about the safety of HC refrigerants in motor vehicle AC? Not much, particularly because the conditions of your challenge do not reflect real circumstances. Even the USEPA (historically staunchly opposed to HC's) admits that 'there are no credible sources of ignition in a vehicle cabin'. Once again, this is supported by the 20+ years of safe commercial use.
What we need is a series of challenges to more accurately represent the real situation. Here are some, for example:
[*] How about a simulation of the more common kind of leak - a hose or coupling failure in the engine bay?
My projections: Engine bay: Both R134a and HC system will have flammability risk. Chance of ignition in the engine bay is marginally higher with HC's+mineral oil, with low to negligible toxicity of emitted gases. R134a+PAG oil will have seriously toxic emitted gases. Cabin: Gases sucked in to the cabin low to negligible with HC+mineral oil, high toxicity with R134a+PAG.
[*] R134a is yesterday and not an option for motor vehicles of the future as it is being phased out in most major regions of the world over the coming years (except in the home of FC's, the USA, of course). So if you want to do a side-by-side comparison of a simplistic direct cabin release and intentional high-energy ignition that has relevance for the future, you'll need to choose fluorocarbon R-152a (toxic and flammable), HF-1234yf (toxic and flammable) or natural refrigerant CO2.
My projections: Your only hope to win this particular challenge would be to choose CO2, but a victory would be by no means certain as CO2 release would reach the asphyxiation level well before a HC release, if my understanding of CO2 vehicle AC systems is correct.
I'll draw this post to a conclusion with some responses to your various comments.
I read all your sales pitch. Very impressive. I noted that you seem to infer that the longer and more its used for a/c, the safer propane becomes. Amazing!! I'll bet you would have faired equally well if you had been in charge of selling AGENT ORANGE or DDT in its time.
I fail to recognize how your clearly intended sarcasm adds value to this forum or credibility to your argument.
For the record, I never made such an inference. The safety of propane has NEVER CHANGED over time. The safety of refrigeration and aircon SYSTEMS incorporating flammable (or non-flammable, for that matter) refrigerants, definitely HAVE become safer over time. Surely this is not in dispute?
Remind me again what was the cause of this fire and initial explosion that killed a firefighter. The amount of burning of the remaining contents isn't really pertinent. Fire investigators are interested in the CAUSE of the fire, and not what was subsequently burned as a result.
An HC refrigerant alone cannot be the CAUSE of the fire. The fire MUST have multiple causes, some of which may involve the refrigerant to some degree. The short answer is we DO NOT KNOW what the causes of the fire were at this stage. All we have is speculation of various shades of expertise at this stage. Similarly, if someone died, as has occurred often, from asphyxiation due to exposure to a release of fluorocarbon R-22, that does not mean I should blame R-22 as 'the cause'. The cause is usually human error and/or gross failures to follow well established procedures and usually a number of other contributing factors. It does not serve either 'side' to be simplistic here.
With respect, the amount of burning and presence of other combustible materials involved in the Tamahere fire ARE pertinent. Cool store fires happen all the time, do similar levels of property and personal damage and there is not a hydrocarbon in sight. There has been at least one more in that region of NZ since Tamahere and it was not an HC system by all reports. There was no HC's used there and the human got out without injury this time so it naturally didn't get the same news coverage. Globally, such fires are almost as regular as clockwork - the main reason such sites have always contained a wide range of flammable materials and potential ignition sources beyond the refrigerant itself.
I would also make the point that a single incident does not establish a trend, and it's trends that important from the point of view of determining whether or not a certain application is appropriate. I can quote you numerous cases of R134a system fires - does that mean R134a should not be used in those applications because of fire risk? Absolutely not! There would have to be a clear and statistically significant trend of fire incidents. We cannot afford to be simplistic in our assessment of refrigerants here - it does neither 'side' any long term benefit. If you can show such a trend to the members of this forum it would indeed be a useful and positive contribution and go a long way to supporting your point of view. As far as I am aware, there is none. If there had been, you can be sure the fluorocarbon lobby would have brought it to light by now.
Response: Is it reasonable to assume that a room full of leaked Hychill (regardless of the room size) or how much the source of the leak contained would result in the same ignition result as Tamahere?
It is a completely unreasonable assumption, sir. I'm a little surprised you would even contemplate that it might be so! It appears I may have assumed your knowledge of the flammability profile of hydrocarbons was greater than it is. If there is any further discussion, we might have to go back to basics first.
Hydrocarbons, if ignite, burn and are exhausted very quickly. Dramatic photos, but misleading.
Response: Quite true. Dynamite shares these two same properties.
I'm not quite sure how to state this without the risk of offense being taken: Equating the speed of a flame front of a burning hydrocarbon gas and the speed of a wave front of a dynamite blast reveals the depth of your lack of understanding of hydrocarbons and their properties.
I was hoping we could encourage a more respectful debate with a solid understanding of the underlying physics, but I now doubt this will be possible. So, unless you request otherwise, I'm content for you to have the last word.
Regards,
John W Clark
Technical Advisor
HyChill Australia
(comp currently has 175ml of PAG oil in it) & a rough guide