On 24/04/17 22:52, Steve Walker wrote:
On 22/04/2017 10:48, The Natural Philosopher wrote:
On 22/04/17 09:45, Nightjar wrote:
On 21-Apr-17 6:46 PM, harry wrote:
On Friday, 21 April 2017 09:58:50 UTC+1, Nightjar wrote:
On 21-Apr-17 8:47 AM, harry wrote:
On Thursday, 20 April 2017 19:24:26 UTC+1, Nightjar wrote:
On 20-Apr-17 6:18 PM, Tim Streater wrote:
In article ,
Nightjar
wrote:

On 20-Apr-17 8:18 AM, harry wrote:
On Wednesday, 19 April 2017 19:47:29 UTC+1, Murmansk wrote:
I've just been for a ride in someone's Nissan Leaf - it was
impressive, so
quiet and amazing acceleration.

Do electric cars have a gearbox (an automatic one I presume)? Or
does the
motor just run faster the faster you go? I was told by the
owner the
optimum speed for economy of battery usage is about 55mph.

It doesn't sound like it's changing gear.

Internal combustion engines are inherently unsuitable for
traction,
hence
the need for gearboxes/clutches etc.
Electric motors can be designed to be ideal for traction.
Max torque at zero rpm.

I could get that with a steam engine.

And a small one at that for a car. But AIUI, it's the condenser
that's
the problem.


With a 24 gallon water tank, the 1924 Doble E had a 1500 mile range
and
it could move off from cold in under 30 seconds.

Drivel.
Water is not fuel.

I was answering the point about the condenser. However, recent
advances
in catalytic splitting of water could make it feasible to use water as
fuel, if you really wanted to.

Drivel.
Have you never heard of the Law of Conservation of Energy?

The principle has been demonstrated. A few years ago the Japanese
demonstrated a fuel cell car that ran entirely on water.

All steam engines and boilers are inherently inefficient.
They will never come anywhere near the ICE efficiency wise.

Typical modern steam power station 37%. More with supercritical steam
Typical diesel. 25%.



Petrol cars achieve a tank to wheel thermal efficiency of about 16%.
Non-condensing third generation steam locomotives achieve a drawbar
thermal efficiency of about 16%.

No use telling harry anything. The thermodynamics are all well
understood, but not by harry



I spent forty years running them. And getting rid of them where
possible.

I suspect that the boilers and engines you are familiar with are more
nineteenth century technology than twenty-first century. A titanium tube
flash boiler can supply steam at up to 4,000 psi and 650C. Ceramics
allow engines to work at those temperatures and pressures and achieve
efficiencies not even dreamed of with conventional materials.

Exatamondo. I cant remember what the law is called, but the hotter the
working fluid (steam in this case) is to start with, and the colder the
final exhaust, the more efficient is the engine.

Which is why a combined cycle gas turbine that starts with 1000C gases
in the jet engine, then heats a boler to get steam, and has a final
after condenser temp of around 50C, willnet you over 60% thermal
efficiency.

There was an article some time ago saying that you can do better than
that. Follow up the whole train with a closed circuit system containing
LPG. The waste heat boils the LPG which drives an expander to produce
more power. Extracting the energy cools the gas to a mixed vapour/liquid
which can then be cooled a little further in a condenser to re-liquify
it for re-circulation.

The law of diminishing returns steps in. You cant get lower than
ambient, and even if you could get back to ambient its still only around
70% from memory.

You need to have a hotter gas to start with.

Steve W



--
"Women actually are capable of being far more than the feminists will
let them."