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We will be concerned with the mixture of dry air and water vapor. This mixture is often called atmospheric air. The temperature of the atmospheric air in air-conditioning applications ranges from about –10 to about 50oC. Under these conditions, we treat air as an ideal gas with constant specific heats. Taking Cpa = 1.005 kJ/kgK, the enthalpy of ...

38 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 886 | Lượt tải: 0

The discussions in this chapter are restricted to nonreactive ideal-gas mixtures. Those interested in real-gas mixtures are encouraged to study carefully the material presented in Chapter 12. Many thermodynamic applications involve mixtures of ideal gases. That is, each of the gases in the mixture individually behaves as an ideal gas. In this sect...

22 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 734 | Lượt tải: 0

Some thermodynamic properties can be measured directly, but many others cannot. Therefore, it is necessary to develop some relations between these two groups so that the properties that cannot be measured directly can be evaluated. The derivations are based on the fact that properties are point functions, and the state of a simple, compressible sys...

38 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 726 | Lượt tải: 0

The vapor compression refrigeration cycle is a common method for transferring heat from a low temperature to a high temperature. The above figure shows the objectives of refrigerators and heat pumps. The purpose of a refrigerator is the removal of heat, called the cooling load, from a low-temperature medium. The purpose of a heat pump is the trans...

20 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 1012 | Lượt tải: 0

We consider power cycles where the working fluid undergoes a phase change. The best example of this cycle is the steam power cycle where water (steam) is the working fluid. For more information and animations illustrating this topic visit the Animation Library developed by Professor S. Bhattacharjee, San Diego State University, at this link.

51 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 817 | Lượt tải: 0

Our study of gas power cycles will involve the study of those heat engines in which the working fluid remains in the gaseous state throughout the cycle. We often study the ideal cycle in which internal irreversibilities and complexities (the actual intake of air and fuel, the actual combustion process, and the exhaust of products of combustion amon...

75 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 858 | Lượt tải: 0

The energy content of the universe is constant, just as its mass content is. Yet at times of crisis we are bombarded with speeches and articles on how to “conserve” energy. As engineers, we know that energy is already conserved. What is not conserved is exergy, which is the useful work potential of the energy. Once the exergy is wasted, it can neve...

28 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 777 | Lượt tải: 0

Example 7-9 Air, initially at 17oC, is compressed in an isentropic process through a pressure ratio of 8:1. Find the final temperature assuming constant specific heats and variable specific heats, and using EES.

52 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 877 | Lượt tải: 0

Entropy and the Clausius Inequality The second law of thermodynamics leads to the definition of a new property called entropy, a quantitative measure of microscopic disorder for a system. Entropy is a measure of energy that is no longer available to perform useful work within the current environment.

53 trang | Chia sẻ: nguyenlinh90 | Ngày: 25/07/2019 | Lượt xem: 799 | Lượt tải: 0

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. Once it has tak...

36 trang | Chia sẻ: nguyenlinh90 | Ngày: 23/07/2019 | Lượt xem: 886 | Lượt tải: 0