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

The unit calorie (IT) per hour per square centimeter, written as cal(IT)/(h·cm²), measures heat flux density or thermal power per unit area using the International Table calorie (1 cal(IT) = 4.1868 J). It represents the amount of heat energy transferred through 1 cm² of surface in 1 hour.

This unit is commonly used in solar energy studies, building physics, and small-scale thermal experiments where energy transfer over extended periods and small areas is measured. Typical applications include:

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  Solar radiation received on small surfaces

  
  
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  Thermal testing of materials over time

  
  
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  Calorimetry experiments

  
  

Mathematically, the heat flux is expressed as:

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

Conversion to SI units:

Although SI units like W/m² are standard, cal(IT)/(h·cm²) remains useful in small-scale experiments, historical solar radiation studies, and building physics references, providing an intuitive way to quantify energy transfer per hour per unit area.

CHU/Hour/Square Foot

The unit CHU/hour/square foot is used to measure Cooling Heat Units per hour per square foot, commonly applied in air conditioning and refrigeration calculations. It indicates the amount of cooling energy, in CHUs, that passes through or is required for one square foot of a surface area over an hour. This measurement helps engineers and designers assess cooling loads, select appropriate air conditioning systems, and ensure thermal comfort in buildings. A higher CHU/hour/square foot value shows greater heat gain, meaning more cooling is needed, while a lower value indicates better insulation or lower cooling requirements. It is essential in designing energy-efficient HVAC systems and optimizing equipment sizing, helping reduce operational costs and maintain desired indoor temperatures. By using CHU/hour/square foot calculations, building designers can balance comfort, energy efficiency, and sustainability effectively.