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physics

Process heat

Process heat is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Process heat rather than just read about it. In short: Process heat refers to the application of heat during industrial processes. Some form of process heat is used during the manufacture of many common products, from concrete to glass to steel to paper.

Process heat — main illustration
Process heat — illustration

Key takeaways

  • Process heat belongs to physics; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Process heat to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Process heat from memory before moving on to harder problems.

Reference excerpt

Process heat refers to the application of heat during industrial processes. Some form of process heat is used during the manufacture of many common products, from concrete to glass to steel to paper. Where byproducts or wastes of the overall industrial process are available, those are often used to provide process heat. Examples include black liquor in papermaking or bagasse in sugarcane processing.

Requirements

Process heating encompasses a wide variety of applications, including boiling water, cooking, distillation, annealing, and forging. The required temperature of the process varies widely, with about half the industrial process heat having operating temperatures above 400 °C (752 °F). These higher-temperature processes can generally only be supplied by dedicated supplies like natural gas or coal, although pre-heating from other sources is also common in order to reduce fuel use. Those processes operating below the median can draw on a much wider variety of sources, including waste heat from other processes in the same industrial process. Resistive heating would in theory be a possible source of process heat but even as it converts nearly 100% of the supplied electricity to heat, it is obviously less efficient to burn a fuel in a thermal power plant to produce electricity only to use that electricity for process heat than to use the fuel directly. Thus this source of heat is only used where electricity from non-thermal sources (such as hydropower) is cheap and plentiful. Heat pumps which are commonly employed for home heating, warm water and other heat applications below 100 °C (212 °F) have too low a Carnot efficiency at high temperature differences between "hot" and "cold" end to be worthwhile. Some processes such as molten salt electrolysis provide the required process heat by the same electricity that is also needed to keep the endothermic reaction going.

Heat is usually described by "grade" with higher temperatures having a higher "grade". This is because heat naturally flows from hot to cold and it is thus always possible to use a high temperature source of heat for lower temperature applications but not vice versa. As higher grade heat is more cumbersome and expensive to produce and as materials have limited heat resistance, there are efforts to reduce working temperatures wherever possible through the use of catalysts and fluxes. In equilibrium reactions where temperature is one of the factors influencing the equilibrium, temperature requirements can be reduced by removing the desired products in a continuous process. For example, if an equilibrium reaction between AB and CD produces AC and BD and the equilibrium can be shifted rightward by increasing temperature, continuously removing AC or BD from the reaction can serve to reduce the temperature requirements (cf. principle of Le Chatelier). However, there are limits to this as the speed of reaction is also temperature-dependent. Catalysts can serve to increase the speed of reaction at any given temperature but they, by definition, do not shift the equilibrium.

Decarbonization

… excerpt ends here. Continue reading the full article.

Illustrations

Process heat: Glass or metal may be annealed at high temperature to increase durability
Glass or metal may be annealed at high temperature to increase durability
Process heat: Cooking is a common application of process heat
Cooking is a common application of process heat
Process heat: Precious-metal tubing heated in an industrial oven during processing
Precious-metal tubing heated in an industrial oven during processing
Process heat: A high-temperature nuclear reactor can provide process heat for hydrogen production
A high-temperature nuclear reactor can provide process heat for hydrogen production

Worked examples

Example 1 — a first encounter with Process heat

Start with the simplest possible case. Write down what Process heat claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Process heat before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Process heat ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Process heat

In research
Process heat appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Process heat in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Process heat is common in secondary-school and first-year university syllabi. It links to neighbouring topics Industrial processes, Renewable energy, so understanding it makes those chapters shorter.
In everyday life
Look for Process heat outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Process heat in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Process heat means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Process heat out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Process heat in simple terms?

Process heat refers to the application of heat during industrial processes. Some form of process heat is used during the manufacture of many common products, from concrete to glass to steel to paper.

Why does Process heat matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Process heat?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Process heat.

Tags

  • Industrial processes
  • Renewable energy

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