Write a program to solve Problem 6.74 with the thermal storage rock bed in Problem 5.60. Let the size and temperatures be input variables so that the heat engine work output can be studied as a function of the system parameters.
Problem 6.74
Find the total work the heat engine can give out as it receives energy from the rock bed as, described in Problem 5.60 (see Fig. P6.74). Hint: write the entropy balance equation for the control volume that is the combination of the rock bed and the heat engine.
Problem 5.60
Thermal storage is made with a rock (granite) bed of 2 m3 that is heated to 400 K using solar energy. A heat engine receives a QH from the bed and rejects heat to the ambient at 290 K. The rock bed therefore cools down, and as it reaches 290 K the process stops. Find the energy the rock bed can give out. What is the heat engine efficiency at the beginning of the process and what is it at the end of the process?
