Unit I First Law of Thermodynamics PDF

“First Law oF thermodynamics” By Dr.. M. P. Joshi Learning Goals Students will be able to recognize basic terminology used in thermal engineering. Students will be able to understand the first law of thermodynamics. 2 9-Dec-24 1] Cir...

“First Law oF thermodynamics” By Dr.. M. P. Joshi Learning Goals Students will be able to recognize basic terminology used in thermal engineering. Students will be able to understand the first law of thermodynamics. 2 9-Dec-24 1] Circle all of the true statements: (a) closed system = control mass (b) closed system = control volume (c) open system = control surface (d) open system = control volume 2] Which of the following process is a quasi-equilibrium process? (a) the stirring and mixing of cold creamer in hot coffee (b) a balloon bursting (c) combustion (d) very slow compression of air in a cylinder 3] Which of the following items is not a path function? A] Heat B] Work C] VdP D] Thermal conductivity. 4] List I List II A] Heat to work 1] Nozzle B] Heat to lift weight 2] Endothermic chemical reaction C] Heat to strain energy 3] Heat engine D] Heat to electromagnetic energy4] Hot air ballon 5] Thermal radiation 6] Bimetallic strips a) A-3 B-4 C-6 D-5 b) A-2 B-4 C-1 D-6 c) A-3 B-4 C-6 D-2 d) None of the above 5] List I List II A] Irreversibilities 1] Thermal equilibrium B] Mechanical work 2] Inexact differentials C] Zeroth law 3] High grade energy D] Heat 4] entropy 5] Thermal radiation 6] Bimetallic strips a) A-3 B-4 C-6 D-5 b) A-2 B-4 C-1 D-6 c) A-4 B-3 C-1 D-2 d) None of the above  THERMODYNAMICS AND ENERGY Conservation of energy principle: During an interaction, energy can change from one form to another but the total amount of energy remains constant. Energy cannot be created or destroyed. The first law asserts that energy is a thermodynamic property. Energy cannot be created or destroyed; it can only change forms (the first law).  The First Law of Thermodynamics The first law of thermodynamics is a statement of the conservation of energy. If a system’s volume is constant, and heat is added, its internal energy increases.  The First Law of Thermodynamics If a system does work on the external world, and no heat is added, its internal energy decreases.  The First Law of Thermodynamics The change in a system’s internal energy is related to the heat Q and the work W as follows:  First Law of Thermodynamics  12 9-Dec-24  The First Law of Thermodynamics dU = đQ + đW “The change in internal energy of a system is equal to the heat supplied plus the work done on the system” The sum of the heat transfer into the system and the work done on the system equals the change in the internal energy of the system The energy balance of a system –as a consequence of FLT- is a powerful tool to analyze the interchanges of energy between the system and its environment. Note that đQ and đW are not functions of state. However, dU is a function of state. Limitations of first law : Second Law of Thermodynamics  First law assumes that all types of energies are equal.  It does not specify the direction in which heat transfer and work transfer can take place.  The first law of thermodynamics sets no limit on how much amount of 14 work produced out of supplied heat. 9-Dec-24  The total energy that a system exchanges with surroundings in any process is dependent only on the initial and final state of the system, and not on the way this change was achieved. 15 9-Dec-24  Q. A gas has constant pressure in a system. There is a loss of 45 J of heat in the surroundings around the system. 450 J of work is done onto the system. Find the system’s internal energy? Solution: ΔU = q+w ΔU = 45J + 450J ΔU = 495J 16 9-Dec-24  How do you rate today’s session? 0--------------------5--------------------10 Very Poor Excellent 17 9-Dec-24 THANK YOU!!!