ThermodynamicsのA-Zガイド、熱&アンプ、質量移動、流体工学
English Русский 中文 Português Español Français Deutsch 概要 編集委員会 連絡先 アクセス Begell House
View in A-Z Index

One of the most important applications of thermodynamic processes is to do work. Work is any interaction between the system and its surrounding which can be used to lift a weight. The definition of work is

(1)

i.e., force multiplied by displacement in direction of force. The unit of work is 1 N m (Newton meter) = 1 J (Joule). Any force, such as the weight of a body, the force of a compressed spring or the attraction between two magnets can produce work. However, the force most commonly used is the pressure force, for example, in an internal combustion engine.

(2)

where p is the pressure, A the area, ds the distance moved and dV the change in volume.

If the fluid expands, V2 > V1, the piston moves upwards and work is done by the system. If the fluid is compressed, V2 < V1, the piston moves downward and work is done to the system. From this the definition of work follows: Work done by the system is positive. Work done to the system is negative.

In an open system, such as a steam turbine, the flow work during inlet and exit into the system contributes to the total work. The shaft work Ws which may be obtained by a rotating or reciprocating shaft is

(3)
表示回数: 13268 記事追加日: 2 February 2011 記事最終修正日: 11 February 2011 ©著作権 2010-2022 トップへ戻る
A-Z索引 著者/編集者 意味マップ ビジュアルギャラリー 寄稿 Guest