Hahahahahhahahaha I knew it!! I knew there was some very small and simple disconnection between the 2 of us. Thanks. -Mario -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of James Newtons Massmind Sent: Thursday, January 12, 2006 6:33 PM To: 'Microcontroller discussion list - Public.' Subject: RE: [OT] Need help with some thermodynamics concepts (or source of it) Arrgh.... a <-> b Got the a and b reversed. Heat a to x degrees above b... What I understood you were going to do with method one was heat a to 100' and let b catch up on its own. That won't work. How you described method 1 just now is basically what I was saying. --- James. > -----Original Message----- > From: piclist-bounces@mit.edu > [mailto:piclist-bounces@mit.edu] On Behalf Of Mario Mendes > Sent: 2006 Jan 12, Thu 15:06 > To: 'Microcontroller discussion list - Public.' > Subject: RE: [OT] Need help with some thermodynamics concepts > (or source of it) > Importance: Low > > Hi James, > > I see what you are saying, but (looking at the diagram): > > | | | | > |---|------|---| > | | b | | > | a | milk | | > | |______| | > | | > | water | > |______________| > ^^^^^^^^^^^^^^ <- heat from stove > > I don't understand what you're trying to explain to me, there > is a disconnection between the two of us somewhere. > > 1) How can I heat b to x degrees above a, if I can't directly heat b? > not only because direct heat from the stove would make the bottom of > b's pan a hot spot, but I also can't use a heater immersed in b > because as the milk curdles and can't be stirred, the heater itself > would become a hot spot, no? > 2) If a < x = b, even applying heat to a, wouldn't b start to > cool until a = x = b and only then start to heat up again as > a become hotter than b? > > With the previous option 1, if a = 90 and b = 90, we're ok, > then I slowly increase a to 91 and keep it there until b = > 91, at which point I then slowly increase a again to 92 and > keep it there until b = 92 and so on, until they're both at > 100. I don't see how the 1F/min rule would be violated if I > increase a at 0.5F/min. > > Thanks. > > > -Mario > > > > -----Original Message----- > From: piclist-bounces@mit.edu > [mailto:piclist-bounces@mit.edu] On Behalf Of James Newtons Massmind > Sent: Thursday, January 12, 2006 2:24 PM > To: 'Microcontroller discussion list - Public.' > Subject: RE: [OT] Need help with some thermodynamics concepts > (or source of it) > > > > 6. over the period of 30 minutes raise the temperature of > the milk to > > 100F, and never raise more than 1F/minute. > > Again, method 1 or 2 will violate this rule. As I said before > you need to use a third method: > > 3) heat b to a temperature that is x degrees above a and keep > increasing b until a hits the target then remove b. This one > will give you a straight line temperature increase which will > make it easy for you to predict when the target will be > reached and adjust x accordingly on the fly. "A" WILL reach > the target temp, and will probably overshoot it slightly > unless you can remove b instantly. > > You can avoid the overshoot by not increasing the temperature > of b past the target temperature so that it curves off like > 1) as it approaches the target. > > I have some (minor) experience with this and I know if you > try to go from 90 to 100 by floating the curd pan in 100 > water, the initial temperature change in the curd will exceed > 1' per minute. > > As the curd can't be mixed, you must keep it fairly thin and > measure its temperature from about half way between the > center and the outside edge. > > --- > James. > > > > > -----Original Message----- > > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On > > Behalf Of James Newtons Massmind > > Sent: 2006 Jan 11, Wed 15:54 > > To: 'Microcontroller discussion list - Public.' > > Subject: RE: [OT] Need help with some thermodynamics concepts (or > > source of it) > > > > > 1) heat a to the temperature I want b to be heated up to > > and then keep > > > a constant there until b reaches the same temperature > > > > I don't see why you need any calculations... This option > will bring b > > up to temp at a rate dependant on the mass of b and the insulation > > between the two assuming they are both mixed to uniform temperature > > inside. The temp graph in b will be a curve which will > flatten out as > > b approaches the target temperature. It will never /actually/ reach > > the target but will come very close. > > > > > 2) heat b to a higher temperature than I want b to be at > > and then let > > > it cool down while b heats up with the heat given off by a until > > > eventually both reach the same temperature > > > > We assume this should have started with "heat /a/ to a higher..." > > > > This one depends on the ratio of masses between a and b and the > > insulation... And the mixing... The curve will be steeper at first > > and then flatten out again. Same problems. > > > > 3) heat b to a temperature that is x degrees above a and keep > > increasing b until a hits the target then remove b. This > one will give > > you a straight line temperature increase which will make it > easy for > > you to predict when the target will be reached and adjust x > > accordingly on the fly. "A" WILL reach the target temp, and will > > probably overshoot it slightly unless you can remove b instantly. > > > > Feedback removes variables. > > > > --- > > James. > > > > > > -- > > http://www.piclist.com PIC/SX FAQ & list archive View/change your > > membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive View/change > your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist