Mailing List Archive Mailing List Archive
> This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. --MS_Mac_OE_3065594570_4348691_MIME_Part Content-type: text/plain; charset="ISO-8859-1" Content-transfer-encoding: quoted-printable On a more practical note, when breathing open circuit, as the gas expands from the tanks to the outlet of the second stage, it cools. This is the sam= e principle that air conditioners work on. This would be the primary source o= f heat loss rather than the composition of the gas being breathed. If you have ever tried a rebreather, one thing that immediately strikes you is how warm and humid your breathing air is. Another comment is that therma= l transfer infers that you are moving heat from A to B, certainly not a facto= r when the heat has nowhere to go, i.e. inside your lungs. While in a drysuit the transfer is from your body to the water which surrounds you. As far as gas of various mixtures acting as a heat transport mechanism, the expansion cooling effect has far more consequences on heat loss on a diver than the composition of your breathing gas to the point of rendering it inconsequential. I am no physicist but this seems to be fairly obvious to me. Jim ------------------------------------------------------------------- Learn About Trimix at http://www.cisatlantic.com/trimix/ From: "moorea(uol)" <moorea@uo*.co*.br*> Date: Wed, 21 Feb 2001 09:34:23 -0300 To: <techdiver@aquanaut.com> Subject: More about breathing Helium thermal loss First of all i wanna thank you people, this is helping so much. But maybe i did not made myself clear. I was talking about breathing gas, there=B4s no question about drysuit inflation, but it stills (not for me at all) about gas breathing. Many people wrote that the thermal conductivity is related with gas density (breathing again). Another one wrote what i think it=B4s the truth, the thermal conduction is related with the thermal properties of gas more than the density (i agree that density is a factor, but not the main one). =20 when i said about Q =3D m c (det t) Q=3D total heat exchange m=3D mass c=3D specific heat delta t=3Dtime variation =20 Still the question. =20 And more, the biggest heat loss is really on the water vapour ? if so the heat exchanges are not the biggest concern ? =20 thanks again=20 =20 Marcelo Moorea --MS_Mac_OE_3065594570_4348691_MIME_Part Content-type: text/html; charset="ISO-8859-1" Content-transfer-encoding: quoted-printable <HTML> <HEAD> <TITLE>Re: More about breathing Helium thermal loss</TITLE> </HEAD> <BODY> On a more practical note, when breathing open circuit, as the gas expands f= rom the tanks to the outlet of the second stage, it cools. This is the same = principle that air conditioners work on. This would be the primary source of= heat loss rather than the composition of the gas being breathed.<BR> <BR> If you have ever tried a rebreather, one thing that immediately strikes you= is how warm and humid your breathing air is. Another comment is that therma= l transfer infers that you are moving heat from A to B, certainly not a fact= or when the heat has nowhere to go, i.e. inside your lungs. While in a drysu= it the transfer is from your body to the water which surrounds you.<BR> <BR> As far as gas of various mixtures acting as a heat transport mechanism, the= expansion cooling effect has far more consequences on heat loss on a diver = than the composition of your breathing gas to the point of rendering it inco= nsequential.<BR> <BR> I am no physicist but this seems to be fairly obvious to me.<BR> <BR> Jim<BR> -------------------------------------------------------------------<BR> Learn About Trimix at http://www.cisatlantic.com/trimix/<BR> <BLOCKQUOTE><BR> <B>From: </B>"moorea(uol)" <moorea@uo*.co*.br*><BR> <B>Date: </B>Wed, 21 Feb 2001 09:34:23 -0300<BR> <B>To: </B><techdiver@aquanaut.com><BR> <B>Subject: </B>More about breathing Helium thermal loss<BR> <BR> </BLOCKQUOTE><BR> <BLOCKQUOTE><FONT SIZE=3D"2"><FONT FACE=3D"Arial">First of all i wanna thank yo= u people, this is helping so much.<BR> But maybe i did not made myself clear. I was talking about breathing gas, t= here=B4s no question about drysuit inflation, but it stills (not for me at all= ) about gas breathing.<BR> Many people wrote that the thermal conductivity is related with gas density= (breathing again).<BR> Another one wrote what i think it=B4s the truth, the thermal conduction is re= lated with the thermal properties of gas more than the density (i agree that= density is a factor, but not the main one).<BR> </FONT></FONT> <BR> <FONT SIZE=3D"2"><FONT FACE=3D"Arial">when i said about Q =3D m c (det t)<BR> Q=3D total heat exchange<BR> m=3D mass<BR> c=3D specific heat<BR> delta t=3Dtime variation<BR> </FONT></FONT> <BR> <FONT SIZE=3D"2"><FONT FACE=3D"Arial">Still the question.<BR> </FONT></FONT> <BR> <FONT SIZE=3D"2"><FONT FACE=3D"Arial">And more, the biggest heat loss is really= on the water vapour ? if so the heat exchanges are not the biggest concern = ?<BR> </FONT></FONT> <BR> <FONT SIZE=3D"2"><FONT FACE=3D"Arial">thanks again <BR> </FONT></FONT> <BR> <FONT SIZE=3D"2"><FONT FACE=3D"Arial">Marcelo Moorea<BR> </FONT></FONT><BR> </BLOCKQUOTE><BR> </BODY> </HTML> --MS_Mac_OE_3065594570_4348691_MIME_Part-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]