Library / Engineering / KEVOS® original book

Heat Transfer by the Numbers

Conduction, insulation, convection, radiation, heat exchangers and warm-up times, worked through one factory hot water system

Calculate heat flows in plant: energy and power, conduction through walls and pipe insulation, convection, radiation, economic insulation, heat exchangers and heating and cooling times.

8 chapters · About 80 minutes · Free to read · Intermediate engineering physics

Start reading
KEVOS® LibraryENGINEERING92%Heat Transfer bythe NumbersKEVOS® ORIGINAL BOOK8 CHAPTERS

About this book

Heat moves wherever there is a temperature difference, by three routes: through solids by conduction, into and out of moving fluids by convection, and across space by radiation. Every factory pays for it. Hot water cools in its pipes, ovens lose heat through their walls, tanks take hours to warm up, and heat that could be recovered from waste streams goes down the drain. The physics was settled a century ago, and the arithmetic is short. What is often missing is the habit of putting numbers on heat flows before deciding what to insulate, what to buy and how long things will take.

This book builds that habit. It starts with energy and power, then works through conduction in flat walls and pipe insulation, convection and radiation at surfaces, the economic thickness of insulation, heat exchangers sized by the log mean temperature difference, and the time it takes to heat and cool a tank. Each chapter works one question through the running case, shows an error and how it is caught, and ends with an exercise and its worked answer.

It assumes school algebra and a calculator. The physics is explained from the start.

The running case

The book follows HW-60, the wash-down hot water system at a fictional food factory. A gas-fired water heater supplies 85 °C water to a 3,000 L stainless steel storage tank, 1.5 m in diameter and 1.8 m tall, and from the tank along 60 m of stainless steel pipe, 60.3 mm in outside diameter, to hose stations on the production floor. The plant room and the floor are at about 20 °C. The hot water runs about 6,000 hours a year.

All quantities, prices, coefficients chosen for the case and results are invented for teaching. This is an illustration. None of it describes a KEVOS® client, supplier or project. Heat is costed at an assumed gas price of A$22 per gigajoule and a heater efficiency of 85%, about A$0.093 per kilowatt-hour of heat delivered. Money is in Australian dollars, excluding GST.

How to use the book

Chapters 1 to 5 build the tools: energy and power, conduction, convection and radiation. Chapter 6 uses them to choose insulation, Chapter 7 to size a heat exchanger, and Chapter 8 to estimate warm-up and cool-down times. Calculators for several steps are in the KEVOS® tools, including insulated pipe heat loss, radiant heat and LMTD heat exchanger. The companion book Thermal Expansion by the Numbers follows the same system through the movement and stress that heat causes.

Source limits and professional responsibility

The supplied 1925 textbook informed the range of subjects. The methods here are standard engineering heat transfer, simplified for hand calculation, with sources given for material data. Convection coefficients in particular are labelled teaching values within published ranges; detailed correlations give better estimates for real design. Hot surfaces and hot water can burn, and pressure systems, gas appliances and their controls are regulated. Real installations must be designed, installed and checked by competent people under the standards and laws that apply.

Who this book is for

Maintenance and production engineers, energy managers, plant designers and technicians who need to estimate heat losses, insulation, heat exchanger duty and heating times with defensible numbers.

What you will learn

  • Convert between energy and power and calculate the heat to warm a quantity of water or metal.
  • Calculate conduction through layered walls and pipe insulation using thermal resistances.
  • Estimate convection and radiation from surfaces and see how surface finish changes them.
  • Choose an economic insulation thickness from heat cost and installed cost.
  • Size a counterflow heat exchanger by LMTD and estimate warm-up and cool-down times.

Inside this book

Chapters

  1. 01Heat, temperature and energySeparate temperature from heat, convert between energy and power, calculate the heat to warm water with Q = m c ΔT, cost it, and meet the three ways heat moves and the idea of thermal resistance.
  2. 02Conduction through walls and layersCalculate conduction through flat walls with Fourier's law, add layer and surface resistances to get a U-value, find each layer's temperature and see why wet or bridged insulation fails.
  3. 03Conduction through pipe insulationCalculate heat loss from insulated pipe with the cylindrical conduction formula, see why each extra millimetre of insulation helps less, account for valves and fittings, and meet the critical radius.
  4. 04Convection at surfacesUse Newton's law of cooling with sensible convection coefficients, tell natural from forced convection, see when insulation makes convection irrelevant, and allow for wind and fans.
  5. 05Radiation from hot surfacesCalculate radiant heat with the Stefan-Boltzmann law in kelvins, see how emissivity changes losses and surface temperatures, add radiation to convection and read thermal cameras correctly.
  6. 06Economic insulation thicknessChoose how thick to insulate by weighing installed cost against the value of heat saved: annual losses, simple payback, marginal payback, discounted totals and the effect of a higher heat price.
  7. 07Heat exchangersRecover heat from waste water: an energy balance on both streams, a plate's overall coefficient, the log mean temperature difference, counterflow, area, effectiveness and fouling.
  8. 08Heating up and cooling downEstimate how fast tanks, pipes and parts heat and cool with the lumped model and its time constant, check when the model applies, decide whether to switch heat off overnight, and watch dead legs.

Apply This in Practice

Use these KEVOS® tools to try the method from this reading with your own numbers.

References and source notes

The manuscript and worked examples are original KEVOS® writing. References inform particular concepts; their authors do not endorse this book. Web references were consulted on 26 October 2026.

  • J. H. Poynting and J. J. Thomson, Charles Griffin and Company, London. A Text-Book of Physics: Heat, eighth edition (1925). Supplied source, read as a subject map of temperature, quantity of heat, specific heat, conduction, convection, radiation and the mechanical equivalent of heat. Both authors died before 1955. No text, figures, examples or problems are reproduced; this book's case, calculations and figures are original and in SI units.
  • The Engineering ToolBox. Thermal Conductivity of Common Materials; Emissivity Coefficients of Common Materials; Convective Heat Transfer (current web pages). Source for conductivities of mineral wool (0.04 W/m·K) and stainless steel (17 W/m·K), emissivities (paint 0.96, aluminium foil 0.04, stainless steel polished 0.075 and weathered 0.85) and typical convection coefficient ranges. The emissivity and convection pages are at engineeringtoolbox.com/emissivity-coefficients-d_447.html and engineeringtoolbox.com/convective-heat-transfer-d_430.html.
  • The Engineering ToolBox. Specific Heat Capacity of Water (current web page). Source for the specific heat of water, between about 4.18 and 4.21 kJ/kg·K from 10 °C to 90 °C; this book uses 4.19 kJ/kg·K.
  • National Institute of Standards and Technology. CODATA value: Stefan-Boltzmann constant (current). Source for σ = 5.670 374 419 × 10⁻⁸ W/m²·K⁴, an exact value, used in Chapter 5.

Continue exploring

← All Library books