Heat Flux Formula

Heat Flux Formula

The rate of thermal energy flow across a heat transfer surface, such as in a heat exchanger, is known as heat flux. Heat flux is the primary factor when calculating heat transfer. Heat fluxes by convection, heat conduction and radiation can all be distinguished using one of three generalised classifications. The Heat Flux Formula is used to calculate heat flux. The temperature difference between the solid, liquid, or gaseous media involved in the convection process directly relates to the heat flux. The temperature gradient vector and the heat flux vector are directly proportional to each other in the conduction process. An electromagnetic radiation flux is produced when heat is exposed to radiation. It can happen without a medium in between, unlike convection and heat conduction. Students having difficulties with solving questions related to the Heat Flux Formula can take advantage of NCERT solutions provided by Extramarks. There is a variety of study materials available on Extramarks for students to download. All the study materials are error-free and upgraded from time to time. 

What is Heat Flux?

Heat flux, also referred to as thermal flux, is a flow of energy per unit of area per unit of time and is also known as heat flux density. Watts per square metre are the units used in SI. Heat flux is a vector quantity because it has both a direction and a magnitude. A number of techniques can be used to measure heat flux. Measuring a temperature difference over a piece of material with known thermal conductivity is a widely used—but frequently impractical—method. This technique is comparable to the common practice of measuring an electric current by measuring the voltage drop across a known resistor. Since the thermal resistance of the material being tested is frequently unknown, performing this method is typically challenging. To calculate thermal resistance, precise values for the material’s thickness and thermal conductivity would be necessary. Heat flux can then be indirectly calculated using the thermal resistance, temperature measurements on both sides of the material, and other information. 

What is the formula for Heat Flux?

It is important for students to keep practising questions and get a deeper understanding of the concepts. All the important formulae need to be learned in order to practice questions.  


  1. The most popular, but frequently impractical method involves comparing the temperatures of two pieces of material with known thermal conductivities. Due to the fact that it is frequently unknown what a material’s thermal resistance is, this method is improper and very challenging to use.
  2. Utilising a heat flux sensor, also known as a heat flux transducer, is the second most accurate way to measure heat flux. It calculates the rate of heat transfer from and to the surface on which the heat flux sensor is fixed. A thermopile with a differential temperature is a typical type of heat flux sensor. No known parameter is required for this thermal resistance/conductivity method.


It is important for students to understand the applications of heat flux. Questions can come from the application of heat flux in the examination. Students need to revise all the topics consistently in order to score well in the examination. It is also crucial to pay close attention to the derivation of the Heat Flux Formula. Each step given in the Heat Flux Formula derivation must be focused on. Students are required to revise the Heat Flux Formula before solving questions. The Heat Flux Formula is helpful in solving numerical problems. The Heat flux value has a wide range of uses. In many industrial applications, including thermal management of electronics, metal heat treatment, boiler and nuclear reactor maintenance, spray cooling, geophysics, etc., it aids in the evaluation of heat transfer performance. 

Heat Flow Rate Formula

The amount of heat that is transferred in a material per unit of time is calculated using the heat flow rate formula. The cross-sectional area of a material rod, the temperature difference between its ends and its length are all inversely correlated with the rate of heat flow in that rod.

Solved Examples for Heat Flux Formula 

It is necessary to learn the Heat Flux Formula to be able to solve questions. Students also need to revise the Heat Flux Formula. Solving questions based on the Heat Flux Formula is important. All the important questions regarding the Heat Flux Formula need to be practised from time to time. Solving questions is important for retaining the Heat Flux Formula for a longer time in the memory.

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