Precisely. But the level of radiation is also affected by the thermal
conductivity of the walls. The lower the thermal conductivity of the walls,
the higher the temperature gradient through the walls. Therefore, all things
being equal, the surface temperature of a rubber coolant hose would be lower
than that of the radiator core. To stay with Dave's example, the heat sinks
on the back of a hi-fi are usually made of aluminum, while the Thermos
bottle is double walled with a (near) vacuum between the walls to maximize
the thermal gradient and to reduce heat loss (or gain, if you fill the
Thermos with ice).
But, I'm getting carried away here; you guys know all this stuff anyway. I
must have been thinking about preparing a lecture for one of my classes.
Come to think of it, I may just use Willie's "experiment" as an example.
Chuck
> ----------
> From: Dave.Vodden@uk.ecitele.com[SMTP:Dave.Vodden@uk.ecitele.com]
> Reply To: Dave.Vodden@uk.ecitele.com
> Sent: Friday, September 24, 1999 2:57 AM
> To: Greg Solow
> Cc: William G. Lamb, III; Stein, Ross; Lorne Goldman; Morgan Mailing
> List
> Subject: Re: Cooling
>
>
>
>
> This is because an infra red gun is measuring the radiation from the
> surface not the temperature. The level of radiation is affected by the
> colour. Dull and dark surfaces radiate more and shiny and light surfaces
> less. Hence radiators, brake drums and the heat sinks on the back of your
> hi-fi should be matt black and Thermos (vaccuum) bottles silver.
>
> Dave Vodden
> 1992 Plus4
> Hampshire
> UK
>
>
>
>
> "Greg Solow" <Gregmogdoc@surfnetusa.com>@autox.team.net on 24/09/99
> 04:44:58
>
> Please respond to "Greg Solow" <Gregmogdoc@surfnetusa.com>
>
> Sent by: owner-morgans@autox.team.net
>
>
> To: "William G. Lamb, III" <lambroving@worldnet.att.net>, "Stein, Ross"
> <Ross.Stein@kp.org>, "Lorne Goldman" <gomog@angelfire.com>
> cc: "William C.W. Lamb" <chip@wmsbrg.com>, "Morgan Mailing List"
> <morgans@autox.team.net>
>
> Subject: Re: Cooling
>
>
> When using a Raytec or any other infared heat measurment device, we have
> found that the color and material of what you are measuring has a very
> substantial effect on the readings obtained. A black metal object, like
> the
> top tank of the radiator will read 20 degrees hotter F than a silver or
> aluminum colored metal surface like a thermostat housing even though they
> are the same temperature.
>
> Regards, Greg Solow
>
> ----- Original Message -----
> From: William G. Lamb, III <lambroving@worldnet.att.net>
> To: Stein, Ross <Ross.Stein@kp.org>; Lorne Goldman <gomog@angelfire.com>
> Cc: William C.W. Lamb <chip@wmsbrg.com>; Morgan Mailing List
> <morgans@autox.team.net>
> Sent: Thursday, September 23, 1999 3:30 PM
> Subject: Re: Cooling
>
>
> >
> > Ross, et al.
> >
> > To satisfy myself as to the accuracy of the VDO water temperature gauge
> > in my 4.0 Plus 8, I had the water temperature measured at the top and
> bottom
> > of the radiator near the location of both sensors, i.e. that for the
> fan,
> > and that
> > for the gauge, with a Raytek infrared gun. The fan kicks in for a few
> seconds
> > whenever the gauge reads ~ 99 - 102 C. The actual water temp at the
> return
> > elbow is 93 C. +/- 1. At the same time, the temperature at the top of
> the
> > radiator is ~ 88 C. So... the VDO is most likely reading 12 - 14 C
> higher
> > than actual water temperature. I know this info will come as a relief to
> many
> > of you. It may also apply to owners of 3.9's since I believe the
> thermostat
> > housings are the same, but you will need to check the VDO part numbers
> > for the 3.9 and 4.0 to see if they are the same.
> >
> > Regards,
> >
> > Willie
> >
> > Land Rover Specialist
> > NAS 4.0 Litre Plus 8 (R-11953)
> > MSCC # 9096, Morgan 3/4 Owners Group
> >
>
>
>
>
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