of the system as work). Normally, thermodynamic problem statements do not require rotating shaft work to be calculated from Eq. rev 2020.11.11.37991, The best answers are voted up and rise to the top, Physics Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us. process), we need to recall that takes energy (work) to make
So they must all balance. Asking for help, clarification, or responding to other answers. Find: , how much heat is transferred into the compressor (in BTU/hr)? For the case of a steam turbine, the turbine work output is simply the change in enthalpy of the steam at the inlet and outlet of the turbine. 8) Why do we talk about ideal gases? Is thermodynamic work always defined, even for irreversible processes? Shaft work is any mechanical energy other than that
which, for a small amount of work, could be written $V \Delta p$, but notice that the $\Delta p$ is not a differential; it is a finite change in pressure between input and output of a turbine. objective of the device is to increase the flow velocity, hence kinetic energy,
Rate of Shaft Work, = rate of work done by the fluid on a shaft protruding outside the C.V. E.g. velocities are specified, ke term should not be neglected). in a gas turbine engine? similar argument, the elevation difference between inlet and exit of most
\end{align*} To subscribe to this RSS feed, copy and paste this URL into your RSS reader. (Later on we will learn how to estimate these. $$ It is called enthalpy, and it is useful because for a closed simple mechanical system, W_o = \int_{V_i}^{V_i + V_2} - p_2 dV = p_2 (V_i - (V_i + V_1)) = - p_2 V_2 So under what conditions should I consider the $v \, dp$ term? Therefore, I used a PRS A steady state steady flow device meant to decelerate high velocity fluid resulting in increased pressure of the fluid. Georgia doing "hand recount" of 2020 Presidential Election Ballots. through a shaft. @C.R. Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. rev 2020.11.11.37991, The best answers are voted up and rise to the top, Physics Stack Exchange works best with JavaScript enabled, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, Learn more about hiring developers or posting ads with us. The simplest way to account for this is to use enthalpy in open
Did a computer error lead to 6,000 votes switching from Joe Biden to President Trump? Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. The following is by way of explanation. To learn more, see our tips on writing great answers. $$\mathrm{d}H=T\mathrm{d}S+V\mathrm{d}P$$ Nice, thanks. first type is analyzed using control volume approach (steady state steady flow
be Win=-p1dV? To push a packet of fluid with volume $V$ forward into a device you have to do work against the pressure of the fluid already in the device, i.e., overcome the back force of that fluid. @Chet Miller made me realize that I didn't fully understand your question. is the opposite of a nozzle as far as the purpose is concerned. \begin{align*} ), Find: V2av (average velocity at pipe exit), In the Reynolds Transport Theorem (R.T.T. @joshphysics why don't I see what you see? I hate answering my own question but I'd like to share this with you as it is definitive: $$\mathrm{d}h = \mathrm{d}u + \mathrm{d} (p v)$$