MEEN 315 PRINCIPLES OF THERMODYNAMICS SPRING 2017 Homework Cover page Student Last Name Student First Name UIN Section Select 204 OR 504 HW Date Submitted 5 Grading Completion All problems attempted Quality Neatness clarity legible Accuracy Accuracy of selected problem s Cover page this page attached on the top and all pages stapled together Total 10 points Max Score 4 1 4 1 Your Score 10 If you wish to compare your answers with the posted solution on eCampus before Exam 1 please make a copy of your solutions before turning it in You will not receive the graded HW 5 before the Exam 1 This cover page should be completed and stapled to the top of your homework solution MEEN 315 PRINCIPLES OF THERMODYNAMICS SPRING 2017 A Note from Your Instructor Your early feedback on lectures course material and teaching learning outcomes in general are very important for the overall success of this course The Early Feedback period is now open so please go to http pica tamu edu to submit your feedback as soon as possible Thank you MEEN 315 PRINCIPLES OF THERMODYNAMICS SPRING 2017 Homework Assignment 5 Due Feb 21 2017 At the beginning of the class Topics covered Property tables Energy balance specific heats Internal energy and enthalpy of ideal gases Question 1 A piston cylinder apparatus initially contains 10 kg of saturated water vapor at 100 C In an isothermal compression process pressure is applied until the water reaches saturated liquid state Indicate the process on a T v diagram Calculate the work done and heat transferred Indicate the direction If the initial state is now changed to saturated water vapor at 40 kPa pressure repeat the calculation for the work and heat transfer Indicate this process on a T v diagram Question 2 A group of students have designed an experiment to demonstrate the First Law of Thermodynamics They use a well insulated piston cylinder filled with air A paddle wheel connected to an external electric motor is inserted through a sealed hole in the cylinder wall as shown in the figure below The piston cylinder walls are well lubricated such that the frictional forces become negligible The outside of the piston is exposed to the atmospheric pressure The initial volume of the air in the cylinder is 0 02 m3 the pressure is 1 2 bar and the temperature is 300 K The electric motor is now turned on the paddlewheel turns and work transfer occurs After a certain period of time the electric motor is turned off and the temperature of the air at the final state was found to be is 400 K a Draw the initial and final states of the air on a P v diagram b Determine the final volume of the air in the cylinder c Calculate the paddle wheel work transfer kJ for the process Consider air as an ideal gas and use the ideal gas tables to find the properties MEEN 315 PRINCIPLES OF THERMODYNAMICS SPRING 2017 Question 3 In a certain chemical process a 5 lbm block of ice with an initial temperature of 20 F is added into an insulated tank containing 25 lbm of liquid water at an initial temperature of 70 F Immediately after adding the block of ice a firm lid is added to keep the volume fixed The specific heat of the solid ice is 0 477 Btu lbm F The latent heat of fusion for melting water is 143 5 Btu lbm Assume that all of these quantities are independent of temperature Determine the final state and the temperature of the material inside the tank 5 lbm 30 lbm T 25 lbm 70 F Initial State Final State Hint Note that from Table A 2E we can find that at the reference point of T 32 018 F the internal energy of saturated water is 0 Btu lbm You can start by calculating internal energies of all states with respect to this reference state Problem 4 A rigid tank contains 2 lbm of air at 14 696 psia and 77 F The tank is heated adding 30 Btu of heat to the system Assuming air to be an ideal gas determine the final temperature F assuming a constant specific heat at 80 F Table A 20E b constant specific heat at the average temperature hint you may want to guess a final temperature and solve the problem iteratively Use the value from part a as your initial guess c variable specific heat given by the polynomial expression in Table A 21E hint you may generate a plot of U vs T for the range of expected T values or use a numerical solver such as Mathlab to find the T value d variable specific heats using table A 22E MEEN 315 PRINCIPLES OF THERMODYNAMICS SPRING 2017 Problem 5 The double acting piston cylinder shown below consists of two chambers separated by a frictionless piston The piston is initially locked in place dividing the device into two equal 1 m3 sub chambers Side A contains water at 90 C and a quality of x 0 7 Side B contains 4 kg of R 134a at 90 C The piston lock is then released allowing the piston to move freely until the pressure equalizes on both sides The temperature of both water and R134a sides remain equal to the surroundings temperature at 90 C during the process Determine a the direction the piston moves when released left or right b the final pressure of the system kPa c boundary work done on by the water kJ d the total heat transfer to from the entire tank kJ Piston lock Piston moves when lock removed H2O 90 C x 0 7 1 m3 R134a 90 C 4 kg 1 m3 Piston initially fixed