- #1
bugatti79
- 794
- 1
Folks,
I am having difficulty correctly representing a mechanical system within a correct "control volume at an instant" in order to identify the various energy balance terms given below
##\displaystyle \dot E_{st}=\frac{d E_{st}}{dt}=\dot E_{in} - \dot E_{out}+ \dot E_g## (1)
that correlates to this derived expression
##\displaystyle m*c_p*\frac{dT}{dt}=q=P_{loss}-hA(T_s-T_{amb})## (2) where q is Watts. The last term is the general term for convection and radiation.
We have the measured power loss ##P_{loss},dt, T_s,T_{amb}## from test. Then we approximate ##m, h, A,h## in order to predict ##dT## which was done successfully.
However, despite all this, i would like to know how the above expression (2) was derived from first principles, ie from (1) in the first place.
Ie, is ##P_{loss}=\dot E_g## the energy generated?
I can write out my interpretation and post it as a picture if anyone is interested in correcting me where i have gone wrong...
thanks
bugatti
I am having difficulty correctly representing a mechanical system within a correct "control volume at an instant" in order to identify the various energy balance terms given below
##\displaystyle \dot E_{st}=\frac{d E_{st}}{dt}=\dot E_{in} - \dot E_{out}+ \dot E_g## (1)
that correlates to this derived expression
##\displaystyle m*c_p*\frac{dT}{dt}=q=P_{loss}-hA(T_s-T_{amb})## (2) where q is Watts. The last term is the general term for convection and radiation.
We have the measured power loss ##P_{loss},dt, T_s,T_{amb}## from test. Then we approximate ##m, h, A,h## in order to predict ##dT## which was done successfully.
However, despite all this, i would like to know how the above expression (2) was derived from first principles, ie from (1) in the first place.
Ie, is ##P_{loss}=\dot E_g## the energy generated?
I can write out my interpretation and post it as a picture if anyone is interested in correcting me where i have gone wrong...
thanks
bugatti