[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

*To*: dinosaur@usc.edu*Subject*: [Fwd: Re: PLEUROCOELOUS VERTEBRAE IN SAUROPODS]*From*: Russ Andersson <randersson@monmouth.com>*Date*: Thu, 14 Nov 1996 13:56:48 -0500 (EST)*Reply-to*: randersson@monmouth.com*Sender*: owner-dinosaur@usc.edu

---Begin Message---> 1: Does heat loss progress at a different rate than heat gain, > ceteris paribus? If so, is it possible to guesstimate a ballpark figure of > the coefficient for a big sauropod? > 2: Is rate of heat loss dependant on outside temperature? Just a quick review of back-of-the-envelope thermodynamics. You can think about thermal problems by their electrical equivalents. Temperature -> Voltage Thermal resistance -> electrical resistance Power burned ie watts -> amps "Thermal inertia" -> capacitance (use def. of "calorie" to get #'s) So two thermal resistances (say a layer of skin over a layer of subcutaneous fat) add together. Two parallel paths, say a dermal path and an aspirated path, add as 1(1/R1+1/R2). [I believe that's missing a solidus: resistance = 1/(1/R1+1/R2) -- MR ] You can trivially model many useful thermal problems quite nicely this way, incl 1 and 2 above. I don't have the time to be able to do a complete job here for such a model(it would require graphics too), but a basic dino model would include a capacitor representing the body mass a constant-current source representing metabolic heat a resistor network representing various heat-dumping mechanisms a fixed- or constant-voltage element(battery) representing the ambient external temperature When you set these up they can be solved easily with 1st-year physics Ohm's Law equations, and with a little calculus you get REAL NUMBERS for thermal time constants. The short answers are NO and YES. But really, the rate is dependent on the DIFFERENCE between internal and ambient temperature. Russ Andersson Autonomous Effects engineering lurker... [ I think the above is reasonably good, but probably a bit too simplistic for anything but very rough calculations. First off, all of the thermal conductivities (the reciprocals of the thermal resistances) are dependent upon temperature (though I suspect this is a small effect for physiologically reasonable temperatures). Bigger neglected effects are a) metabolic heat production isn't necessarily constant -- it will vary with activity levels, gut loading and probably temperature. The ambient temperature isn't fixed. Finally, no mention is made of the variable current source provided by solar (and to a much lesser extent indirect solar) radiation. But it's a good start, and I'll allow such messages because I think people should have some understanding of the basic physics before they try to conclude anything about the not so basic biology. -- MR ]

---End Message---

- Prev by Date:
**Re: Biped advantage** - Next by Date:
**Re: ?New species/genera** - Previous by thread:
**Re: pleurocoels** - Next by thread:
**Pterodaustro** - Indexes: