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.

Kilocalorie (IT) per Hour per Square Meter [kcal(IT)/(h·m²)]

The unit kilocalorie (IT) per hour per square meter, written as kcal(IT)/(h·m²), measures heat flux density or thermal power per unit area using the International Table kilocalorie (1 kcal(IT) = 4186.8 J). It represents the amount of heat energy transferred through 1 square meter of surface in 1 hour.

This unit is often used in building engineering, HVAC, and solar energy studies to quantify energy transfer through walls, roofs, or solar collectors. Typical applications include:

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  Heat gain or loss through building surfaces

  
  
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  Solar energy incident on rooftops or flat surfaces

  
  
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  Design of heating and cooling systems

  
  

Mathematically, heat flux is expressed as:

where q is heat flux in kcal(IT)/(h·m²), Q is total heat in kilocalories, A is area in m², and t is time in hours.

Conversion to SI units:

Although SI units such as W/m² are now standard, kcal(IT)/(h·m²) remains useful in legacy building and thermal engineering literature, providing an intuitive measure of energy transfer over time in kilocalories.