Calorie (th) per Hour per Square Centimeter [cal(th)/(h·cm²)]

The unit calorie (th) per hour per square centimeter, written as cal(th)/(h·cm²), measures heat flux density or thermal power per unit area using the thermochemical calorie (1 cal(th) = 4.184 J). It represents the amount of heat energy transferred through 1 cm² of surface in 1 hour.

This unit is often used in solar energy studies, calorimetry experiments, and building physics, especially when small surface areas and long durations are considered. Typical applications include:

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  Solar radiation incident on small surfaces

  
  
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  Thermal testing of materials over time

  
  
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  Calorimetry experiments

  
  

Mathematically, heat flux is expressed as:

where q is heat flux in cal(th)/(h·cm²), Q is energy in calories, A is area in cm², and t is time in hours.

Conversion to SI units:

While SI units such as W/m² are standard, cal(th)/(h·cm²) remains convenient in small-scale laboratory and historical studies, providing an intuitive way to quantify energy transfer per hour per unit area.

Calorie (th) per Second per Square Centimeter [cal(th)/(s·cm²)]

The unit calorie (th) per second per square centimeter, written as cal(th)/(s·cm²), measures heat flux density or power per unit area using the thermochemical calorie (1 cal(th) = 4.184 J). It represents the amount of heat energy transferred through 1 cm² of surface every second.

This unit is commonly used in laboratory-scale heat transfer experiments, solar energy studies, and focused radiation applications, especially where the energy is concentrated over a small surface area. Applications include:

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  Solar radiation intensity measurements

  
  
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  Laser or concentrated light experiments

  
  
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  Calorimetry experiments on small samples

  
  

Heat flux can be expressed mathematically as:

where q is heat flux in cal(th)/(s·cm²), Q is energy in calories, A is area in cm², and t is time in seconds.

Conversion to SI units:

While W/m² is the SI standard, cal(th)/(s·cm²) remains useful in laboratory and historical references, providing a practical measure for high-intensity, small-area heat transfer.