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### Radiative Heat Transfer Coefficient of a Human Calculator

Heat Transfer Engineering

Thermodynamics

Physics

Radiative Heat Transfer Coefficient of a Human Calculator

The linearized radiative heat transfer coefficient can be calculated by

Eq. 1

*h _{r} = 4 ε σ ( A_{r} / A_{D} ) ( 459.7 + ( t_{cl} + t_{r} ) / 2 )^{3}*

where

*h _{r}* = radiative heat transfer coefficient, Btu/h·ft

^{2}·°F

*ε*= average emissivity of clothing or body surface, dimensionless

*σ*= Stefan-Boltzmann constant, 0.1712 x 10

^{-8}Btu/h·ft

^{2}·°R

^{4}

*t*= temperature of clothed body or clothing °F

_{cl}*t*= mean radiant temperature °F

_{r}*A*= effective radiation area of body, ft

_{r}^{2}

A

_{D}= Activity metabolic rates Btu/h·ft

^{2}(met), typical metabolic rates for an average adult

( A

_{D}= 19.6 ft

^{2}) for activities performed continuously. see: Metabolic Rate Thermal Energy Created by the Human Body

The ratio *A _{r}*/A

_{D}is 0.70 for a sitting person and 0.73 for a standing person (Fanger 1967). Emissivity

*ε*is close to unity (typically 0.95), unless special reflective materials are used or high-temperature sources are involved. It is not always possible to solve Equation 1 explicitly for

*h*, because

_{r}*t*may also be unknown. Some form of iteration may be necessary if a precise solution is required. Fortunately,

_{cl}*h*is nearly constant for typical indoor temperatures, and a value of 0.83 Btu/h·ft

_{r}^{2}·°F suffices for most calculations. If emissivity is significantly less than unity, adjust the value by

*h _{r}* = 0.83

*ε*

where *ε* represents the area-weighted average emissivity for the clothing/body surface.

Conversions

1 met = 18.4 Btu/h· ft^{2} = 50 kcal/h ·m^{2}.

Related

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- Radiant Heat Exchange Perpendicular Plates Equation and Calculator
- Radiant Heat Parallel Plates Equation and Calculator
- Metabolic Rate Energy Burned Calculator
- Thermal Energy Created Metabolic Rate by the Human Body
- Water Vapor Released by Human Activity and Plants
- Emissivity of Surface Table- Heat Transfer
- Unit Thermal Resistances Well Sealed Air Spaces
- Heat Radiation of a Surface
- Heat Transfer Practical Approach

Source

2016 ASHRAE Handbook - HVAC Systems and Equipment, ASHRAE: 2016.