Engineering Theory Articles
Theory articles and study notes on mechanical engineering, electrotechnics, HVAC and fluid dynamics.
Boyle's law
where P is the pressure of the gas, V is the volume of the gas, and k is a constant "Constant (mathematics)")
Darcy–Weisbach equation
In fluid dynamics, the Darcy–Weisbach equation is an empirical equation that relates the head loss, or pressur
Controls & Hysteresis - Why the Compressor Starts and Stops
HVAC — Lesson 11 · Controls & Hysteresis — Why the Compressor Starts and Stops The core idea A thermostat is t
Sensible vs Latent Heat: Why Humid Air Costs More
HVAC — Lesson 10 · Sensible vs Latent Heat — Why Humid Air Costs More to Cool The core idea Every cooling job
NPSH – Net Positive Suction Head: Preventing Pump Cavitation
NPSH-R vs NPSH-A explained: the NPSH-A formula with a worked example, safety margins, and how to stop pump cavi
AC Fundamentals - Why 230 V Mains Peaks at 325 V
Electrotechnics — Lesson 3 · 21 September 2026 AC Fundamentals — Why "230 V" Mains Actually Peaks at 325 V The
Superheat & Subcooling: A System's Vital Signs
HVAC — Lesson 9 · Superheat and Subcooling — Reading a System's Vital Signs The core idea Two temperatures tel
Buckling — Why Columns Fail Long Before They Crush
Buckling — Why Columns Fail Long Before They Crush The core idea Compress a short block and it fails by crushi
Heat Loads — Sizing a Cooler From First Principles
Heat Loads — Sizing a Cooler From First Principles The core idea A heat load is the rate at which heat enters
Parallel Circuits - Why Every Appliance Gets Full Voltage
Electrotechnics — Lesson 2 · 17 September 2026 Parallel Circuits — Why Every Appliance Gets the Full 230 V The
Duct Sizing — Why Area Beats Velocity
Duct Sizing — Why Area Beats Velocity The core idea A duct's job is to move a set volume of air (m³/h) with th
Torsion — Twisting Shafts & Why Tubes Beat Rods
Torsion — Twisting Shafts & Why Tubes Beat Rods The core idea Twist a shaft and every cross-section shears aga
Humidity - Relative vs Absolute, and the Dew Point
HVAC — Lesson 3 · Humidity, Relative vs Absolute, and the Dew Point The core idea Air's appetite for water vap
Ohm's Law & Electric Power
⚡ ELECTROTECHNICS — Lesson 1 · Saturday, 12 September 2026 Ohm's Law & Electric Power — Voltage, Current, and
COP — Why a Heat Pump Can Be 400% Efficient
COP — Why a Heat Pump Can Be "400% Efficient" The core idea An engine's efficiency is useful output divided by
Section Shape & the Second Moment of Area — Why Beams Stand on Edge
Section Shape & the Second Moment of Area — Why Beams Stand on Edge The core idea A beam's resistance to bendi
Vapour-Compression Cycle: How Machines Move Heat
The Vapour-Compression Cycle: How Machines Move Heat The core idea Nothing actually makes cold. Heat is energy
Elasticity & Hooke's Law
Elasticity & Hooke's Law The core idea Stretch any solid object and it pushes back. Below a limit, that push-b