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While W/m² is the SI standard, cal(th)/(s·cm²) remains useful in laboratory and historical references, providing a practical measure for high-intensity, small-area heat transfer.

Dyne per Hour per Centimeter [dyne/(h·cm)]

The unit dyne per hour per centimeter, written as dyne/(h·cm), measures force per unit length over time, often used in contexts such as viscous drag, material creep, or very slow mechanical processes in cgs (centimeter-gram-second) units.

A dyne is the cgs unit of force, defined as the force required to accelerate 1 gram of mass by 1 cm/s². Therefore, 1 dyne = 10⁻⁵ newtons in SI units. The additional division by centimeter represents a per-unit-length measure, and division by hour accounts for time rate.

Mathematically, the quantity can be expressed as:

where F is force in dynes, L is length in cm, and t is time in hours.

Applications include:

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  Creep or stress studies in materials under very small forces over long periods

  
  
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  Lubrication or viscous flow measurements in cgs-based engineering studies

  
  
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  Experimental mechanics where small forces per unit length are measured over extended time

  
  

Conversion to SI units:

This unit is largely of historical or specialized interest but provides a precise cgs-based measure for extremely slow, small-force phenomena.