When discussing Carnot engines, it is assumed that the engine is in thermal equilibrium with the source and the sink during the heat addition and heat rejection processes, respectively. That is, it is assumed that T* H 5 TH and T* L 5 TL so that there is no external irreversibility. In that case, the thermal efficiency of the Carnot engine is hC 5 1 2 TL/TH. In reality, however, we must maintain a reasonable temperature difference between the two heat transfer media in order to have an acceptable heat transfer rate through a finite heat exchanger surface area. The heat transfer rates in that case can be expressed as Q # H 5 (hA)H(TH 2 T * H) Q # L 5 (hA)L(T * L 2 TL) where h and A are the heat transfer coefficient and heat transfer surface area, respectively. When the values of h, A, TH, and TL are fixed, show that the power output will be a maximum when T * L T * H 5 a TL TH b 1/2 Also, show that the maximum net power output in this case is W # C,max 5 (hA)HTH 1 1 (hA)H/(hA)L c1 2 a TL TH b 1/2 d
American federal Government Week 5 and Lecture 2/23 Materials, Slides, readings (MindTap) lec 2/23: Guantanamo bay island where the U.S. Stores suspected terrorists, a treaty makes it so that we can have a naval base there. Prisoners are mistreated, some have been tried, some sent back to countries of origin, president Obama promised to close Guantanamo. When he took steps to close it, republicans started to make laws that said that the president could spend no money moving the prisoners to U.S. soil, and could spend no money to make a new prison for them here. Congress has control over appropriations; in this case congress used that power as a veto. Illustrated problems and power struggle between president and congress. President: Election is a long and arduou
