Provide some suggestions as to how the following processes could have lower degrees of irreversibility:
(a) a piston sliding against a cylinder wall;
(b) condensing water vapor at 1 atm;
(c) heating a metal to its melting point in a furnace.
What will be an ideal response?
(a) Friction between the piston and the cylinder wall could be reduced by using a lubricant or by machining the surfaces to a smoother finish.
(b) Use a coolant temperature whose temperature is below, but close to 100oC, to minimize the temperature difference across which heat transfer occurs.
(c) Keep the furnace temperature just above the melting point temperature of the metal. Slowly preheat the metal with heat from sources closer in temperature to the metal temperature – for instance, pass the furnace exhaust gases over the metal in a counter-flow fashion.
You might also like to view...
A baker has developed a marvelous cookie recipe that works best if the cookie is cooled in a vacuum chamber through radiation heat transfer alone. The cookie is placed inside the chamber with a surface temperature of 125°C. Assume that the cookie is thin enough so that the temperature is uniform throughout during the cooling process. The walls of the chamber are maintained at 10.0°C. If the surface area of the cookie is 0.005 m2, and if the emissivity of the cookie is 0.80, determine the initial radiation heat transfer rate from the cookie to the walls of the chamber.
Given: Ts = 125°C = 398 K; Tsurr = 10°C = 283 K; A = 0.005 m2; ? = 0.80 What will be an ideal response?
In the accompanying figure, a(n) ____________________ has been used to step down the 480-volt supply line voltage to 120 volts for use by the control circuit.
Fill in the blank(s) with the appropriate word(s).
Cheese and yogurt are the only milk products with decreased consumption from 1970 to 2009
Indicate whether the statement is true or false.
Who coined the expression laissez faire to describe the benefits of an unrestricted market economy?
a. the physiocrats b. Adam Smith c. David Hume d. Robert Burns