相关概念视频
Heat Engines
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A heat engine is a device used to extract heat from a source and then convert it into mechanical work used for various applications. For example, a steam engine on an old-style train can produce the work needed for driving the train.
Whenever we consider heat engines (and associated devices such as refrigerators and heat pumps), we do not use the standard sign convention for heat and work. For convenience, we assume that the symbols Qh, Qc, and W represent only the amounts of heat transferred...
Whenever we consider heat engines (and associated devices such as refrigerators and heat pumps), we do not use the standard sign convention for heat and work. For convenience, we assume that the symbols Qh, Qc, and W represent only the amounts of heat transferred...
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Mechanisms of Heat Transfer
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Heat transfer between the human body and its environment occurs through four main mechanisms: conduction, convection, radiation, and evaporation.
Conduction, accounting for approximately 3% of body heat loss at rest, is the process of exchanging heat between molecules of two materials in direct contact. This can result in both heat loss and gain. For instance, when the body is submerged in water, which conducts heat 20 times more effectively than air, it can either lose or gain significant...
Conduction, accounting for approximately 3% of body heat loss at rest, is the process of exchanging heat between molecules of two materials in direct contact. This can result in both heat loss and gain. For instance, when the body is submerged in water, which conducts heat 20 times more effectively than air, it can either lose or gain significant...
1.6K
Mechanisms of Heat Transfer I
5.9K
Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature difference, heat transfer occurs. It may occur rapidly, such as through a cooking pan, or slowly, such as through the walls of a picnic ice box. So many processes involve heat transfer that it is hard to imagine a situation where no heat transfer occurs. Yet, every heat transfer takes place by only three methods: conduction, convection, and radiation.
5.9K
Mechanisms of Heat Transfer II
4.2K
In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the buoyancy of warm air and water, transfer hot air from the tropics toward the poles and cold air from the poles toward the tropics. The Earth’s rotation interacts with those flows, causing the observed eastward flow of air in the temperate zones. Convection dominates heat transfer by air, and the amount of available space for the airflow...
4.2K
The Carnot Cycle
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Converting work to heat is an irreversible process, and the purpose of a heat engine is to reverse the effect partially. Heat engines aim to increase the efficiency of the reversal, that is, maximize the work retrieved from heat. If the efficiency of a heat engine were 100%, it would imply reversing the process completely without introducing any other effect. Thus, it would violate the second law of thermodynamics.
What could be the theoretical limit to the efficiency of a heat engine? The...
What could be the theoretical limit to the efficiency of a heat engine? The...
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Mechanism of heat transfer
1.8K
Understanding heat transfer mechanisms is essential for understanding how our bodies maintain balance in different environmental conditions. When the environment is thermoneutral, the body is in a state of balance, neither using nor releasing energy to maintain its core temperature. However, when the environment is not thermoneutral, the body employs four heat transfer mechanisms to maintain homeostasis: conduction, convection, evaporation, and radiation. These mechanisms facilitate heat...
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带有水力动力流动的微观热力发动机
P S Pal1, Sourabh Lahiri2, Arnab Saha3
1Korea Institute for Advanced Study, School of Physics, Seoul 02455, Korea.
Physical review. E
|November 18, 2025
概括
水力动力学流动对随机热发动机有很大的影响. 与循环流的偏差允许从流场中利用工作,但高旋转频率阻止了热力学工作生产.
科学领域:
- 体科学是一种体科学.
- 统计力学就是统计力学.
- 热力学是一种热力学.
背景情况:
- 体颗粒是随机热引擎的关键组成部分.
- 在体悬浮液中常见地观察到水力动力流.
- 这些流量对发动机性能的影响尚未完全理解.
研究的目的:
- 调查水力动力流如何影响合体静态热发动机的输出参数.
- 分析外部剪切流和内部陷力所做的工作.
- 探索一个扩展模型,其中一个旋转粒子影响发动机动力学.
主要方法:
- 在稳定的线性剪切流下,在周期性波陷中研究单个环状颗粒.
- 分析不同的流量性质:圆形,圆形和过度波形.
- 模拟一个扩展模型,其中一个旋转粒子影响着体粒子动态.
主要成果:
- 在准静态极限中,流量工作占据了非循环流的陷工作的优势.
- 圆流所做的工作是正的;高波流可以产生负的工作 (利用能量).
- 在扩展模型中,高旋转频率导致流动工作占主导地位,防止热力学工作.
结论:
- 水力动力流的性质决定了合热发动机中的能量动力学.
- 在特定的条件下,可以利用外部流动进行工作,特别是超标流动.
- 在扩展系统中,在高旋转频率下,发动机性能受到流量主导的限制.


