THE UNIVERSITY OF MICHIGAN Department of Mechanical ...
THE UNIVERSITY OF MICHIGAN Department of Mechanical Engineering ME 235 Thermodynamics I / Winter 2014 / Section 002 HW 9 Solutions Due date: Mar. 27 2014
6.25 Determine the missing property among P, T, s, and x for R-410A at: a. T = –20°C, v = 0.1377 m3/kg b. T = 20°C, v = 0.01377 m3/kg c. P = 200 kPa, s = 1.409 kJ/kgK Solution:
6.30 Two kg water at 120°C with a quality of 25% has its temperature raised 20°C in a constant volume process. What are the new quality and specific entropy?
6.44 A piston cylinder maintaining constant pressure contains 0.1 kg saturated liquid water at 100°C. It is now boiled to become saturated vapor in a reversible process. Find the work term and then the heat transfer from the energy equation. Find the heat transfer from the entropy equation, is it the same? Solution:
6.49 A piston/cylinder has 2 kg water at 1000 kPa, 200°C which is now cooled with a constant loading on the piston. This isobaric process ends when the water has reached a state of saturated liquid. Find the work and heat transfer and sketch the process in both a P-v and a T-s diagram.
6.54 A piston/cylinder has 2 kg of R-410A at 60°C, 100 kPa which is compressed to 1000 kPa. The process happens so slowly that the temperature is constant. Find the heat transfer and work for the process assuming it to be reversible.
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6.55 A heavily insulated cylinder/piston contains ammonia at 1200 kPa, 60°C. The piston is moved, expanding the ammonia in a reversible process until the temperature is −20°C. During the process 200 kJ of work is given out by the ammonia. What was the initial volume of the cylinder? Solution:
6.60 Two 5 kg blocks of steel, one at 250°C the other at 25°C, come in thermal contact. Find the final temperature and the change in entropy of the steel? Solution:
6.66 A piston cylinder has constant pressure of 2000 kPa with water at 20°C. It is now heated up to 100°C. Find the heat transfer and the entropy change using the steam tables. Repeat the calculation using constant heat capacity and incompressibility.
6.25 Determine the missing property among P, T, s, and x for R-410A at: a. T = –20°C, v = 0.1377 m3/kg b. T = 20°C, v = 0.01377 m3/kg c. P = 200 kPa, s = 1.409 kJ/kgK Solution:
6.30 Two kg water at 120°C with a quality of 25% has its temperature raised 20°C in a constant volume process. What are the new quality and specific entropy?
6.44 A piston cylinder maintaining constant pressure contains 0.1 kg saturated liquid water at 100°C. It is now boiled to become saturated vapor in a reversible process. Find the work term and then the heat transfer from the energy equation. Find the heat transfer from the entropy equation, is it the same? Solution:
6.49 A piston/cylinder has 2 kg water at 1000 kPa, 200°C which is now cooled with a constant loading on the piston. This isobaric process ends when the water has reached a state of saturated liquid. Find the work and heat transfer and sketch the process in both a P-v and a T-s diagram.
6.54 A piston/cylinder has 2 kg of R-410A at 60°C, 100 kPa which is compressed to 1000 kPa. The process happens so slowly that the temperature is constant. Find the heat transfer and work for the process assuming it to be reversible.
2
1
2
1
6.55 A heavily insulated cylinder/piston contains ammonia at 1200 kPa, 60°C. The piston is moved, expanding the ammonia in a reversible process until the temperature is −20°C. During the process 200 kJ of work is given out by the ammonia. What was the initial volume of the cylinder? Solution:
6.60 Two 5 kg blocks of steel, one at 250°C the other at 25°C, come in thermal contact. Find the final temperature and the change in entropy of the steel? Solution:
6.66 A piston cylinder has constant pressure of 2000 kPa with water at 20°C. It is now heated up to 100°C. Find the heat transfer and the entropy change using the steam tables. Repeat the calculation using constant heat capacity and incompressibility.
