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Unformatted text preview: Chapter 1 Introduction and Overview Chapter 1 INTRODUCTION AND OVERVIEW Thermodynamics, Heat Transfer, and Fluid Mechanics 1-1C Classical thermodynamics is based on experimental observations whereas statistical thermodynamics is based on the average behavior of large groups of particles. 1-2C On a downhill road the potential energy of the bicyclist is being converted to kinetic energy, and thus the bicyclist picks up speed. There is no creation of energy, and thus no violation of the conservation of energy principle. 1-3C There is no truth to his claim. It violates the second law of thermodynamics. 1-4C Thermodynamics deals with the amount of heat transfer as a system undergoes a process from one equilibrium state to another. Heat transfer, on the other hand, deals with the rate of heat transfer as well as the temperature distribution within the system at a specified time. 1-5C The driving force is ( a ) the temperature difference for heat transfer, ( b ) the electric potential difference for electric current flow (voltage), and ( c ) the pressure difference for fluid flow. 1-6C Heat transfer is a non-equilibrium phenomena since in a system that is in equilibrium there can be no temperature differences and thus no heat flow. 1-7C No, there cannot be any heat transfer between two bodies that are at the same temperature (regardless of pressure) since the driving force for heat transfer is temperature difference. 1-8C Stress is defined as force per unit area, and is determined by dividing the force by the area upon which it acts. The normal component of a force acting on a surface per unit area is called the normal stress , and the tangential component of a force acting on a surface per unit area is called shear stress . In a fluid, the normal stress is called pressure . Mass, Force, and Units 1-9C Pound-mass lbm is the mass unit in English system whereas pound-force lbf is the force unit. One pound-force is the force required to accelerate a mass of 32.174 lbm by 1 ft/s 2 . In other words, the weight of a 1-lbm mass at sea level is 1 lbf. 1-10C Kg is the mass unit in the SI system whereas kg-force is a force unit. 1-kg-force is the force required to accelerate a 1-kg mass by 9.807 m/s 2 . In other words, the weight of 1-kg mass at sea level is 1 kg-force. 1-11C There is no acceleration, thus the net force is zero in both cases. 1-12 A plastic tank is filled with water. The weight of the combined system is to be determined. Assumptions The density of water is constant throughout. Properties The density of water is given to be = 1000 kg/m 3 . Analysis The mass of the water in the tank and the total mass are m w = V = (1000 kg/m 3 )(0.2 m 3 ) = 200 kg m total = m w + m tank = 200 + 3 = 203 kg Thus, 1-1 m tank =3 kg V=0.2 m 3 H 2 O Chapter 1 Introduction and Overview N 1991 m/s kg 1 N 1 ) m/s kg)(9.807 (203 2 2 = = = mg W 1-13 The interior dimensions of a room are given. The mass and weight of the air in the room are to be The interior dimensions of a room are given....
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- Spring '08
- Heat Transfer