| Author | Message | ||
     Randy Roberson Grand Master Username: wascator Post Number: 475 Registered: 5-2009 |
Imagine using liquid natural gas (LNG) as motor fuel. One cubic foot of LNG vaporizes to about 600 cubic feet of natural gas: a great fuel for engines which burns very clean and has high Octane rating. Assume you need about 25 HP for steady-on down the road: assume efficiency of 10,000 BTU per HP-hour (I have no idea what it would be for an auto engine at part load; this is a fairly common heat rate for older natural gas industrial engines, maybe a little high but easy to calculate with) then you would be using 250 cubic feet per hour of gaseous NG, expanded from LNG this would be less than 1/2 cubic foot of liquid per hour. It's at -260F or -162C, so free air conditioning all day long, plus it's a good use for some engine heat which is otherwise dumped to atmosphere. United Parcel Service is running long-haul trucks in the USA today on LNG. I see them on the Interstates and there is frost on the saddle tank outlets. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1444 Registered: 6-2009 |
The problem being that to get that free AC you have to have air meant for the passenger compartment flowing over an evaporator filled with LNG. I presume there would be some way that leak detection and/or fire detection could be worked in, but one tiny pin hole and you can get a cabin filled with enough natural gas to "be problematic" fairly quickly. My A/C guy and I were talking about refrigerants the other day and how many of the things we use as liquified fuel gasses would be ideal, far better than what we use, were it not for the fact that they burn so easily. He mentioned once seeing a demonstration of propane being used, and a tiny leak intentionally created and ignited. The flame plume was, apparently, quite impressive. Brian | ||
| Randy Roberson Grand Master Username: wascator Post Number: 479 Registered: 5-2009 |
One would need a heat exchanger to prevent flammable gas from the possibility of entering the ventilation system, of course. Refineries routinely use petroleum products as refrigerants for their processes: propane is an excellent refrigerant, aside from the obvious flammability. A couple of local attorneys (husband and wife) got a good start to their career representing a renter whose landlord had filled a window air conditioner with propane. when it shot fire out and burned them (figure out the rest). | ||
| Omar M. Shams Grand Master Username: omar Post Number: 477 Registered: 4-2009 |
Randy - you beat me to it. In the oil and gas industry we regularly use very explosive gases for their Joules Thompson properties. if you separate the gas from "people" using water - you have a perfectly safe set up. Omar | ||
| Robert Noel Reddington Prolific User Username: bob_uk Post Number: 225 Registered: 5-2015 |
I recently posted a similiar thread but not the idea of using the fuel to work the aircon. I was explaining that a gas system with a water heated vapouriser gives a car extra cooling capacity for the engine. The use of propane as a refrigerant in cars is reasonably safe IMO because of the small amount used. LPG is so good that less than 1/2 the amount is needed in comparison to R12. 750 ml of LPG. But if the gas available is say a 100 litres then if the system goes wrong then the danger factor will go up a few hundred fold. If it fills the car with lpg then its going to go bang and kill. An indirect system using antifeeze as a medium to move heat around is much safer. The amount of extra fuel required to run aircon on large engine cars is not a lot. Smaller engines can lose much as 5mpg. | ||
| Jan Forrest Grand Master Username: got_one Post Number: 834 Registered: 1-2008 |
If you're an avid (too avid in my case) follower of the Eastern European and Asian 'car crash' clips on YouTube you will see the effects of poor gas installations on cars. Several simply catch fire in the passenger compartment with no warning. A few more start to burn at the engine end and the flames rapidly work back towards the gas tank and the remaining few explode with the ferocity of an IED. I prefer to evaporate the liquid gas with engine coolant and spend the extra on fuel to run the air con. Ps. Has nobody read my thread on recharging old r12a based air con systems? | ||
| Robert Noel Reddington Prolific User Username: bob_uk Post Number: 234 Registered: 5-2015 |
Our Asian brothers seem not to use ignition pulse safety solenoids. They probably use a manual valve. |
