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The second law of thermodynamics states that processes occur in a certain direction, not in just any direction. Physical processes in nature can proceed toward equilibrium spontaneously: Water flows down a waterfall. Gases expand from a high pressure to a low pressure. Heat flows from a high temperature to a low temperature.

34 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 742 | Lượt tải: 0

If we neglect the changes in kinetic and potential energies as fluid flows through an adiabatic turbine having one entrance and one exit, the conservation of mass and the steady-state, steady-flow first law becomes

43 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 910 | Lượt tải: 0

Conservation of Energy for Control volumes The conservation of mass and the conservation of energy principles for open systems or control volumes apply to systems having mass crossing the system boundary or control surface. In addition to the heat transfer and work crossing the system boundaries, mass carries energy with it as it crosses the syste...

25 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 859 | Lượt tải: 0

The first law of thermodynamics is an expression of the conservation of energy principle. Energy can cross the boundaries of a closed system in the form of heat or work. Energy transfer across a system boundary due solely to the temperature difference between a system and its surroundings is called heat. Work energy can be thought of as the energ...

67 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 732 | Lượt tải: 0

We now turn our attention to the concept of pure substances and the presentation of their data. Simple System A simple system is one in which the effects of motion, viscosity, fluid shear, capillarity, anisotropic stress, and external force fields are absent. Homogeneous Substance A substance that has uniform thermodynamic properties throughout...

61 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 748 | Lượt tải: 0

We will soon learn how to apply the first law of thermodynamics as the expression of the conservation of energy principle. But, first we study the ways in which energy may be transported across the boundary of a general thermodynamic system. For closed systems (fixed mass systems) energy can cross the boundaries of a closed system only in the form ...

48 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 855 | Lượt tải: 0

INTRODUCTION The study of thermodynamics is concerned with the ways energy is stored within a body and how energy transformations, which involve heat and work, may take place. One of the most fundamental laws of nature is the conservation of energy principle. It simply states that during an energy interaction, energy can change from one form to an...

34 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 816 | Lượt tải: 0

Stagnation Properties Consider a fluid flowing into a diffuser at a velocity , temperature T, pressure P, and enthalpy h, etc. Here the ordinary properties T, P, h, etc. are called the static properties; that is, they are measured relative to the flow at the flow velocity. The diffuser is sufficiently long and the exit area is sufficiently large t...

58 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 732 | Lượt tải: 0

Since the percent theoretical air is known, the N2 balance gives B. The H balance gives G. Then the C and O balances give two equations that relate the remaining three unknowns D, E, and F. Therefore, we need one more equation. To obtain this last equation relating the mole numbers of the products, we assume that the products are in chemical equil...

32 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 865 | Lượt tải: 0

Initially, we shall consider only those reactions that go to completion. The components prior to the reaction are called reactants and the components after the reaction are called products. For more information and animations illustrating this topic visit the Animation Library developed by Professor S. Bhattacharjee, San Diego State University, at...

49 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 798 | Lượt tải: 0