alluminum block
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From: Michael Robinson on 14 Jan 2010 19:11 "elahetal" <elahetale(a)yahoo.com> wrote in message news:1cednUIyaMjf5dLWRVn_vwA(a)giganews.com... > Hello all, > > If I need an Al Block to heat up and I need the least possible dimensions > but I need to increase its temperature from ambient temp(20 degree) to 60 > degree. how many watts I need and what the dimensions should be? I do not > know from which point I should start. > Do you have a practical application you're trying to work out?
From: bw on 15 Jan 2010 01:37 "elahetal" <elahetale(a)yahoo.com> wrote in message news:1cednUIyaMjf5dLWRVn_vwA(a)giganews.com... > Hello all, > > If I need an Al Block to heat up and I need the least possible dimensions > but I need to increase its temperature from ambient temp(20 degree) to 60 > degree. how many watts I need and what the dimensions should be? I do not > know from which point I should start. > > Thanks Start as simply as possible. Al has a specific heat capacity of 0.9 joules per gram. If your aluminum weighs 1 gram it will take 0.9 joules to raise the temp 1 degree C. To raise the temp 40 degrees then you need 40*0.9 = 36 Joules A Watt is a Joule per second. So it will take 36 seconds at the rate of 1 watt to heat your one gram by 40 degrees using one watt of power. If you want to heat 1 gram in 3.6 seconds then you will need 10 watts.
From: pimpom on 15 Jan 2010 05:58 bw wrote: > "elahetal" <elahetale(a)yahoo.com> wrote in message > news:1cednUIyaMjf5dLWRVn_vwA(a)giganews.com... >> Hello all, >> >> If I need an Al Block to heat up and I need the least possible >> dimensions but I need to increase its temperature from ambient >> temp(20 degree) to 60 degree. how many watts I need and what >> the >> dimensions should be? I do not know from which point I should >> start. >> >> Thanks > > Start as simply as possible. Al has a specific heat capacity of > 0.9 > joules per gram. > If your aluminum weighs 1 gram it will take 0.9 joules to raise > the > temp 1 degree C. > To raise the temp 40 degrees then you need 40*0.9 = 36 Joules > > A Watt is a Joule per second. So it will take 36 seconds at the > rate > of 1 watt to heat your one gram by 40 degrees using one watt of > power. > > If you want to heat 1 gram in 3.6 seconds then you will need 10 > watts. That's a good starting point. However, it assumes that there's no loss. In practice, there will be loss of heat from conduction, convection, radiation and imperfect transfer from the heat source. The extent of the loss depends on the environment. The temperature will stabilize when the rate of loss balances the rate of heating energy supplied. If heat loss is zero (impossible in practice but can be approximated), the temperature will continue to rise indefinitely as long as power is applied.
From: John Larkin on 15 Jan 2010 06:42 On Fri, 15 Jan 2010 00:37:38 -0600, "bw" <bwegher(a)hotmail.com> wrote: > >"elahetal" <elahetale(a)yahoo.com> wrote in message >news:1cednUIyaMjf5dLWRVn_vwA(a)giganews.com... >> Hello all, >> >> If I need an Al Block to heat up and I need the least possible dimensions >> but I need to increase its temperature from ambient temp(20 degree) to 60 >> degree. how many watts I need and what the dimensions should be? I do not >> know from which point I should start. >> >> Thanks > >Start as simply as possible. Al has a specific heat capacity of 0.9 joules >per gram. >If your aluminum weighs 1 gram it will take 0.9 joules to raise the temp 1 >degree C. >To raise the temp 40 degrees then you need 40*0.9 = 36 Joules > >A Watt is a Joule per second. So it will take 36 seconds at the rate of 1 >watt to heat your one gram by 40 degrees using one watt of power. > >If you want to heat 1 gram in 3.6 seconds then you will need 10 watts. > > The numbers work out, pretty close, that you can use Spice to model thermal systems, using 1 gram of aluminum to be one farad, 1 K/W as one ohm, 1 K becoming 1 volt. You can approximate thermal diffusion with a string of R-Cs, sorta. John
From: George Herold on 15 Jan 2010 12:08
On Jan 15, 5:58 am, "pimpom" <pim...(a)invalid.invalid> wrote: > bw wrote: > > "elahetal" <elahet...(a)yahoo.com> wrote in message > >news:1cednUIyaMjf5dLWRVn_vwA(a)giganews.com... > >> Hello all, > > >> If I need an Al Block to heat up and I need the least possible > >> dimensions but I need to increase its temperature from ambient > >> temp(20 degree) to 60 degree. how many watts I need and what > >> the > >> dimensions should be? I do not know from which point I should > >> start. > > >> Thanks > > > Start as simply as possible. Al has a specific heat capacity of > > 0.9 > > joules per gram. > > If your aluminum weighs 1 gram it will take 0.9 joules to raise > > the > > temp 1 degree C. > > To raise the temp 40 degrees then you need 40*0.9 = 36 Joules > > > A Watt is a Joule per second. So it will take 36 seconds at the > > rate > > of 1 watt to heat your one gram by 40 degrees using one watt of > > power. > > > If you want to heat 1 gram in 3.6 seconds then you will need 10 > > watts. > > That's a good starting point. However, it assumes that there's no > loss. In practice, there will be loss of heat from conduction, > convection, radiation and imperfect transfer from the heat > source. The extent of the loss depends on the environment. The > temperature will stabilize when the rate of loss balances the > rate of heating energy supplied. If heat loss is zero (impossible > in practice but can be approximated), the temperature will > continue to rise indefinitely as long as power is applied.- Hide quoted text - > > - Show quoted text - Yup, Is the block floating in space or attached to something? The smaller the block the faster you can rasie it's temperature. (As long as it's not attached to some other heat sink.) I always seem to end up with heaters in the 10 Watt range. Can you give us more details? George H. |