In the study of thermodynamics, the heat transfer coefficient is the amount of heat that is transferred per unit area. For heat transfer to have a physical meaning, there must be a temperature difference between the heated surface and the contact area.

    There are many units of heat transfer coefficient that can be converted into each other. The easiest and most efficient way is to use a heat transfer coefficient converter. Try ours for free.

    For a full explanation of what the heat transfer coefficient is measuring, check out our comprehensive Q&A below.


    What is heat transfer co-efficient?

    Heat transfer coefficient is defined as a quantitative characteristic of convective heat transfer between a fluid medium and the surface.

    In Simpler Terms

    Basically, heat transfer coefficient is the way heat moves from one thing to another. For heat to transfer, there must be a difference in temperature.

    The heat will move from the hotter body into the cooler body. Once the two are the same temperature, the process is complete.

    See, the world has its own homeostasis. It looks for stability in many ways, and heat transfer coefficient is simply one of those ways.

    With this intuition, understanding heat transfer coefficient can made easier.

    What's the unit of heat transfer coefficient?

    We need to be able to measure heat for many, many reasons. We heat our food, our houses, and even our bodies heat themselves.

    The heat transfer coefficient has SI units in watts per squared meter kelvin: W/(m2 K).

    However, there are a number of other units that we use to measure the heat transfer coefficient: the Joule, BTU, and often the calorie. They are expressed as:

    • calorie/second square centimeter Celcius (cal/s cm2 C)
    • joule/second square meter Kelvin (J/s m2 K)
    • kilocalorie/hour-square foot Celcius (kcal/h ft2 C)
    • kilocalorie/hour-square meter Celcius (kcal/h m2 C)
    • BTU/second-square foot Fahrenheit (BTU/s ft2 K)
    • watt/square meter Celcius (W/m2 C)

    How do you calculate heat transfer coefficient?

    Heat transfer coefficient is expressed in terms of overall conductance. This is determined by the following formula:

    h = q / (T2-T1)


    • T1 and T2 are temperature readings at two different points
    • And q is the heat energy transferred between the points

    There are three types of heat transfer, conduction, convection, and radiation.

    Heat Conduction

    Heat conduction, also known as thermal conduction, is the transfer of heat from one solid to another when they are touching each other.

    Think of putting a hot water bottle on top of a cool water bottle. After a few minutes, both bottles will be warm as a result of heat conduction.

    Convection Heat Transfer

    Convection heat transfer is the transfer of heat through the movement of matter. Air, for example, moves easily.

    If you open a window in a hot room, the hot air will meet with the cold air and transfer. This is why air the cools off.

    Radiation Heat Transfer

    Radiation heat transfer happens when the movement of heat goes from one place to another by electromagnetic radiation rays.

    Perhaps one of the most common examples of radiation heat transfer is the way that the sun warms the earth.

    How do you convert heat transfer coefficient units?

    The traditional method for conversion is worked out on paper.

    As aforementioned, there are multiple units of heat transfer coefficient including calories, kilocalories, joules, and BTU.

    The formulas to convert these units are as follows:

    Calories to Joules

    1 cal(th) = 4.184 J

    Calories to BTU

    BTU = 0.003968320716 cal

    Calories to Watts

    1 cal/s = 4.19 W

    Joules to BTU

    1 J = 0.00094781712 BTU(IT)

    BTU to Joules

    BTU(IT) = 1055.05585262 J

    When doing your conversions, you'll have to account for the magnitude, whether its in meters, centimeters, or feet, the temperature aspect of your measurement (i.e. C, F, or K), and the time factor (i.e. hour, second, minute).

    Now that you have a better grasp on how it works, you can better understand how to convert the units.

    Our calculator is a fast and easy option to help you with that time intensive conversion work.

    What are some examples of heat transfer coefficient?

    We've all heard of people talking about having too many calories. Heat is a form of energy. Your body requires energy to function.

    Everything that you do requires energy. Running, eating, and even blinking all require a certain amount of energy.

    Calories From Food

    When someone talks about having a muffin but worries that there are over 400 calories, they're worried about the amount of heat (i.e energy) that they're consuming.

    When the body has excess energy, it stores it. We all know how it's stored: tummy, thighs, etc.

    This is a prime example of the heat transfer coefficient.

    The heat/energy from the food is transferred into your body, which is then transferred to your brain, muscles, or possibly expelled from the body.


    Let's consider another example. If you take an ice cube and hold it in your hand you'll experience heat transfer coefficient through conduction.

    The heat from your hand is transferring itself to the cooler object (the ice). Because of the increase in water temperature, the ice starts to melt because it elevates past water's freezing point.

    Wait, why does your hand start to feel cold if cold can't be transferred? Good question.

    What you're feeling is the heat leaving your hand. Once the ice is removed your body notices that your hand is no longer in homeostasis, so it transfers heat to your hand and warms it back up.

    It's really pretty cool if you think about it.

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