Honda has hot gas heating

[nova]

New Honda Accord diesel has ac hot gas heating system.
Any additional info?

There's surely use for it as this week Northern-Finland had -42C

[Peter_1]

Where does the energy come from at -42°C?
Do the engines not heat up over there when running?
It's waste of energy, almost all of the energy available in the fuel is converted to heat.

[chillin out]

From the engine waste heat?

If the engine has heat up then why the need for a heat pump?

I think this has not been designed for -42 temps but just for cold mornings.

I know for sure my wife would want one.

Chillin

[phil68]

I guess it's so you get instant heat, otherwise you have to wait for the engine to heat the engine coolant

[chillin out]

Should have put an extra alternator in, and then run a 3 bar fire inside.


Chillin

[nova]

I guess it's so you get instant heat, otherwise you have to wait for the engine to heat the engine coolant

I believe this is the idea of the system. We all know nowadays diesel engines doesn't provide too much heat energy.

If you start up your diesel engine at -30C, you'd appreciate the instant heat a/c hot gas system is providing. Another thing is that how windshield is taking that instant heat...

[nova]

Where does the energy come from at -42°C?

From a/c compressor

Do the engines not heat up over there when running?

No. Diesel engines runs cold at -20C and colder. For example Volvo has additional heater (Ardic) in their diesel engines as a standard to achieve normal engine operating temperatures at cold ambients.

It's waste of energy, almost all of the energy available in the fuel is converted to heat.

All available energy is converted to hp in diesel engines. The efficiency of current diesel engines is very high, so there's not much heat energy available for heating system.

[phil68]

All available energy is converted to hp in diesel engines. The efficiency of current diesel engines is very high, so there's not much heat energy available for heating system.[/QUOTE]
Not true, from memory spark-ignition (petrol) I.C. engines run at about 40% efficiency i.e. 40% of the fuel's energy is converted into motive power, the rest is wasted as heat. The compression-ignition (diesel) I.C. engine is about 50% efficient

[nova]

All available energy is converted to hp in diesel engines. The efficiency of current diesel engines is very high, so there's not much heat energy available for heating system.

Not true, from memory spark-ignition (petrol) I.C. engines run at about 40% efficiency i.e. 40% of the fuel's energy is converted into motive power, the rest is wasted as heat. The compression-ignition (diesel) I.C. engine is about 50% efficient[/QUOTE]

Ok, I forgot to mention "almost all energy"...
Anyway diesel engine has better efficiency than petrol engine and therefore produces less heat than petrol engine.

[hybridjunction]

so how does it work? Is the hot gas ine running parrallell to the fuel line? Even here in Australia with high ambients pre heaters are sometimes fitted to diesels or a line brased to the manifold.

[nova]

I had new Citroen HDi (fortunetly HAD) and it never reached normal operating temperature @ -20C or so. I recall some manufacturers are installing additional heater wires inside the coolant hoses to achieve normal temperatures / enough heat to the cabin.

[phil68]

Diesel fuel has trouble flowing below -10 or so too, the waxes seperate out & clog the lines so manufacturers fit fuel line heaters for those climates. I've seen footage of HGV drivers trying to defrost their fuel lines with a blow torch

I had new Citroen HDi (fortunetly HAD) and it never reached normal operating temperature @ -20C or so. I recall some manufacturers are installing additional heater wires inside the coolant hoses to achieve normal temperatures / enough heat to the cabin.

[nova]

Diesel fuel has trouble flowing below -10 or so too, the waxes seperate out & clog the lines so manufacturers fit fuel line heaters for those climates. I've seen footage of HGV drivers trying to defrost their fuel lines with a blow torch

There's different fuel grades for cold climates. In Finland we have:
Summer grade: chill point -12C
Winter grade: chill point -34C
Arctic grade: chill point -44C

Pour point is below these temperatures.

Just last week our service affiliate had an English customer, who's unit fuel tank was almost full of some british grade fuel which of course was not working too well at -26C ambient. Our SA mixed 8 litres of petrol and some two-stroke oil to the diesel and the unit started to work. Not necessarely recommended, but sometimes only way to get unit up and running.

But this fuel issue is of course not the reason for current diesel engines running cold at colder ambients. Volvo has additional fuel heater (like Webasto) as a standard in their diesel models. They are simply not generating enough heat, whether it's because of the engine efficiency or whatever

[Karl Hofmann]

I'm surprised that they haven't developed a heat exchanger that capitalises on the heat expelled in the exhaust gasses to heat the cabin, rather like they used to have on VW Beetles but passing heat to refrigerant. If you had a small diesel powering a large heavy vehicle, then the engine and the engine coolant will heat far mor quickly than would a large powerfull diesel in a realatively light vehicle. My 1.9TD Transporter would heat by the end of my road, my lazy slow reving 174 T5 takes about four miles before it is at operating temperature.

[phil68]

That's a good idea as far as the exhaust is the quickest thing to heat up but I reckon car manufacturers don't do it because a.) there is the possibility of cross-over & exhaust fumes ending up in the cabin & b.) engines run more efficiently if the exhaust temperature is kept as high as possible (raises gas velocity).

I'm surprised that they haven't developed a heat exchanger that capitalises on the heat expelled in the exhaust gasses to heat the cabin, rather like they used to have on VW Beetles but passing heat to refrigerant. If you had a small diesel powering a large heavy vehicle, then the engine and the engine coolant will heat far mor quickly than would a large powerfull diesel in a realatively light vehicle. My 1.9TD Transporter would heat by the end of my road, my lazy slow reving 174 T5 takes about four miles before it is at operating temperature.

[Karl Hofmann]

Yeh plenty of folks got smoked when the heat exchanger rotted away on the Beetles

In order to prevent this, I would suggest that the gasses be passed over an evaporator rather than use the air directly fron the heat exchanger, only a portion of the exhaust gases would need to be passed over the evaporator, and the evaporator would need to be isolated from excess heat in the Summer.

Hmm, have we just invented the condensing exhaust system?

Last I heard was cars were going to CO2 heat pumps, but even so there is little heat to scavenge in minus 40

[phil68]

There's heat to be scavenged right down to -256 deg.C (absolute zero on the Kelvin scale) but you're right, refrigerants in general usage aren't much cop past -20. What I propose is using R23 (as used on cascade systems) as it'll scavenge heat past -40 with a huge expansion tank mounted on the roof

Yeh plenty of folks got smoked when the heat exchanger rotted away on the Beetles

In order to prevent this, I would suggest that the gasses be passed over an evaporator rather than use the air directly fron the heat exchanger, only a portion of the exhaust gases would need to be passed over the evaporator, and the evaporator would need to be isolated from excess heat in the Summer.

Hmm, have we just invented the condensing exhaust system?

Last I heard was cars were going to CO2 heat pumps, but even so there is little heat to scavenge in minus 40

[nova]

I read from somewhere that indeed this Honda's a/c is co2 system. I know that Denso has made a working co2 a/c system, which is going to be adopted by car manufacturers very shortly. Surprisingly, co2 a/c consumes LESS energy, than traditional R134 system, even though head pressure can be as high as 140 bar

Some info on Denso co2 a/c:
http://www.theautochannel.com/news/2...04/151245.html
http://www.sae.org/automag/techbriefs/04-2002/page2.htm


What comes to the waste energy (heat), BMW has some focus on that. Interesting system this "Turbosteamer": http://www.autoblog.com/2005/12/09/b...-hot-and-goes/

[reefermadness]

Webasto, everyone has a diesel heater here. You can't drive without one. Price of fuel just too expensive. I have one in my Honda CRX (1990). Unfortunatly, honda doesn't bring Diesels to Canada, or i'd buy one. i'm talking about highway tractors, off highway vehicles etc.... I just happen to have one because i too like the instant heat.

Reefermadness