THM-27

Enthalpy

Definition of enthalpy.

Reading speed

GoverningEnthalpy

Governing equation

H=U+pV

$p \in \left[10, 1000\right]$

where

U: U (kJ)
p: p (kPa)
V: V (m³)
H: Enthalpy (kJ)

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

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①

Governing law — red

H=U+pV

$p \in \left[10, 1000\right]$

$p = 10$ $H = 208$

Along the curve

②

Domain of the variable — blue

p_{\min} = 10,\quad p_{\max} = 1000

$p \in \left[10, 1000\right]$

$p = 10$ $p = 10$

Along the curve

③

Response curve — green

H=U+pV

$p \in \left[10, 1000\right]$

$p = 10$ $H = 208$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}H}{\mathrm{d}p}

$p \in \left[10, 1000\right]$

$p = 16.23$ $H^{\prime} = 0.8$

Along the curve

Lecture brief

Historical brief

Carnot (1824), Clausius entropy, the first law and later van der Waals and Gibbs potentials turned heat into a state science. The sheets compute work, efficiency and vapour pressure. This sheet (THM-27 — Enthalpy) is the form associated with Enthalpy. Working symbols: $U$ , $p$ , $V$ $\rightarrow$ $H$ . Definition of enthalpy. Pedagogical SI sheet with a live model and a swept parameter.

Purpose

Purpose: compute

H

from

U

p

V

in Thermodynamics via

H=U+pV

Definition of enthalpy. Use it when a real thermodynamics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

U = 200.000\,\mathrm{kJ}

p = 101.000\,\mathrm{kPa}

V = 0.800\,\mathrm{m^{3}}

, the governing relation

H=U+pV

yields

H = 280.800\,\mathrm{kJ}

. One governing identity, SI units, a single sweep on the sheet. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

U U200 kJp p101 kPaV V0.8 m³

Outputs

Enthalpy H280.800 kJ

Reading speed

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Narration of this film

One governing identity, SI units, a single sweep on the sheet.

Definition of enthalpy. Pedagogical SI sheet with a live model and a swept parameter.

Reading speed

Watch on YouTube