Hello everybody,
One thing that has distinguished this hot spell from the one in August
1990 has been that the humidity has been much higher. Over SE England in the
last few days the dewpoints have been in the range 17-20°C yet I have not heard
one mention of it in a forecast despite the fact that these are high figures
and add greatly to the discomfort. Yet in 1990 many people I spoke to
attributed their discomfort to the humidity, due, no doubt to the fact that in
those days humidity was all the rage. Yet when I pointed out that the air was
quite dry (DP about 11°C) and the reason they felt hot was because it *was* hot
some even refused to believe it, presumably having absorbed the then current
hype.
I would have thought the forecasters would have made a right meal of the
current humidity levels, but barely a dicky-bird. I wonder why.

Tudor Hughes, Warlingham, Surrey.

On 07 Aug 2003 13:03:24 GMT, (TudorHgh) wrote:

Hello everybody,
One thing that has distinguished this hot spell from the one in August
1990 has been that the humidity has been much higher. Over SE England in the
last few days the dewpoints have been in the range 17-20°C yet I have not heard
one mention of it in a forecast despite the fact that these are high figures
and add greatly to the discomfort. Yet in 1990 many people I spoke to
attributed their discomfort to the humidity, due, no doubt to the fact that in
those days humidity was all the rage. Yet when I pointed out that the air was
quite dry (DP about 11°C) and the reason they felt hot was because it *was* hot
some even refused to believe it, presumably having absorbed the then current
hype.
I would have thought the forecasters would have made a right meal of the
current humidity levels, but barely a dicky-bird. I wonder why.

Yes, that's strange. They occasionally mention "humid nights" though.
Perhaps they are all so used to working in air conditioned offices
with low humidity that they forget about it.

Talking of which, I've got a portable A/C unit in my "home office" and
I've noticed that some people dismiss them as "useless" because they
only lower temperatures by 3 or 4 degrees C in a single room i.e. they
won't keep it at 21 like the big office systems. At first, I was
disappointed but then I realised that they make it feel much cooler
than the temperature indicates. I'm certain now that it's lower
humidity created by such units that make it *feel* cooler than it
really is. I'm emptying 10 litres of water a day from mine, all
extracted the room air.

All of which reinforces your point about the importance of humidity
and I, too, am surprised that the forecasters don't make more of it.

Currently 28C outside, 25 in the room but feeling rather pleasant as
the A/C unit battles with my 2 PCs, 2 monitors, a TV, sunshine at the
front window - and *me*.

--
Dave
Fareham

On Thu, 07 Aug 2003 14:25:42 +0100, Dave Ludlow
wrote:


Talking of which, I've got a portable A/C unit in my "home office" and
I've noticed that some people dismiss them as "useless" because they
only lower temperatures by 3 or 4 degrees C in a single room i.e. they
won't keep it at 21 like the big office systems. At first, I was
disappointed but then I realised that they make it feel much cooler
than the temperature indicates. I'm certain now that it's lower
humidity created by such units that make it *feel* cooler than it
really is. I'm emptying 10 litres of water a day from mine, all
extracted the room air.


Also, the lower humidity would allow an increase in the rate of
evaporation of perspiration resulting in a lower skin temperature.

--
Alan White
Twenty-eight miles NW of Glasgow.
Overlooking Loch Goil and Loch Long in Argyll, Scotland.
http://tinyurl.com/55v3

On 07 Aug 2003 20:07:23 GMT, (TudorHgh) wrote:

I'm emptying 10 litres of water a day from mine, all
extracted the room air.

Just done a quick calculation. Your 10 litres of water is equivalent to
lowering the dewpoint from 20°C to 15°C (worth it!) of about 1900 cubic metres
of air. The latent heat released is about 24 megajoules, which is equivalent
to 6.8 kilowatt-hours. You must be sucking in a lot of humid air from outside,
but that's inevitable. Your own contribution, by the way, is about 200 watts
of sensible heat, and an unknown quantity, which I am far too gentlemanly to
estimate, of latent heat as evaporated perspiration.

Keep cool!

Yes, cooler than the average thermometer tells me! Nice explanation of
why my portable A/C does indeed work better than at first it seems

--
Dave

Dave,
My figure of 6.8 KWh means that over, say, an 8-hour working day it
consumes getting on for a kilowatt, but that's assuming 100% efficiency. So I
presume it uses rather more than this. Even so, that's only one bar of an
electric fire or a bit more. It would seem to be worth it if your office is
your livelihood.

Tudor Hughes, Warlingham, Surrey.

On 07 Aug 2003 23:36:20 GMT, (TudorHgh) wrote:

Dave,
My figure of 6.8 KWh means that over, say, an 8-hour working day it
consumes getting on for a kilowatt, but that's assuming 100% efficiency. So I
presume it uses rather more than this. Even so, that's only one bar of an
electric fire or a bit more. It would seem to be worth it if your office is
your livelihood.

Yes, it is. I bought it last weekend and couldn't have worked in here
this week without it as I need to be able to think clearly 100% of the
time (online stock trading). Target for the week: to recover the cost!

It's a small one, 5500 BTU/hour cooling capacity which I think
converts to 1.6 KW. I make it work hard, forever in and out of the
room! Power input is only 720W, I don't understand that at all.
*shakes head confusedly*

--
Dave

"Dave Ludlow" wrote in message
...

It's a small one, 5500 BTU/hour cooling capacity which I think
converts to 1.6 KW. I make it work hard, forever in and out of the
room! Power input is only 720W, I don't understand that at all.
*shakes head confusedly*

Congratulations!
You appear to have created energy out of nothing.
Have you told the guys at the National Physics Laboratory?
I think they might be interested.........

Col
--
Bolton, Lancashire.
160m asl.
http://www.reddwarfer.btinternet.co.uk

"TudorHgh" wrote in message
...
I would have thought the forecasters would have made a right meal of
the
current humidity levels, but barely a dicky-bird. I wonder why.


To be honest, I think I've heard it quite a few times and not just referring
to night time either. It's often in conjunction with the word 'opressive'.

Col
--
Bolton, Lancashire.
160m asl.
http://www.reddwarfer.btinternet.co.uk

On Fri, 08 Aug 2003 01:35:02 +0100, Dave Ludlow in
wrote:

On 07 Aug 2003 23:36:20 GMT, (TudorHgh) wrote:

Dave,
My figure of 6.8 KWh means that over, say, an 8-hour working day it
consumes getting on for a kilowatt, but that's assuming 100% efficiency. So I
presume it uses rather more than this. Even so, that's only one bar of an
electric fire or a bit more. It would seem to be worth it if your office is
your livelihood.

Yes, it is. I bought it last weekend and couldn't have worked in here
this week without it as I need to be able to think clearly 100% of the
time (online stock trading). Target for the week: to recover the cost!

It's a small one, 5500 BTU/hour cooling capacity which I think
converts to 1.6 KW. I make it work hard, forever in and out of the
room! Power input is only 720W, I don't understand that at all.
*shakes head confusedly*

Dave - I have just found this thread and see you bemusement. I know little
about "heat pumps" but would guess that is what is happening in your case.
You get more out than you put in, as much is coming from the environment.

Here's a link that goes into more detail about them:

http://www.heatpumpcentre.org/tutorial/intro.htm

A key sentence is "A typical electrical heat pump will just need 100 kWh of
power to turn 200 kWh of freely available environmental or waste heat into
300 kWh of useful heat."

Mind you, I could be barking up the wrong tree totally:-)

--
Mike posted to uk.sci.weather 08/08/2003 08:56:47 UTC
Coleraine
Seeking information about the Internet and the way it works? - Subscribe to
news:uk.net.beginners

"TudorHgh" wrote in message
...
Over SE England in the
last few days the dewpoints have been in the range 17-20°C yet I have
not heard
one mention of it in a forecast despite the fact that these are high
figures
and add greatly to the discomfort.

I believe one BBC presenter did show a chart of RH values with the
comment "we don't show this very often". No doubt some viewers now
believe that 65% is a high humidity and are wondering what the record
might be for the UK. :-)

Tom Allen