Heat transfer from body through layers, using h, T, d, A

C. The person's core body temperature is 37C and their surface tissue thickness is 5 mm. They are wearing clothes with a thickness of 2 mm, and the surface heat transfer coefficient is hsurf = 8.1 W m−2 K−1. Chetan also provides the thermal conductivity values for the surface tissue (kst = 0.2 W m−1 K−1) and clothing (kclo = 0.05 W m−1 K−1). Chetan believes that the h values for the surface, tissue, and clothes need to be
  • #1
SunshineCat
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Homework Statement


Consider a person in a room with an air temperature of 21C. The persons core body temperature is 37C and their surface tissue thickness is 5 mm. If the total surface area of their skin is 1.5 m2, and they are wearing clothes of a thickness of 2 mm and the surface heat transfer coefficient (including conduction and radiation) is hsurf = 8.1 W m−2 K−1 then what is the net rate of heat tranfer from this persons body (in W)

thermal conductivity of surface tissue: kst = 0.2 W m−1 K−1
thermal conductivity of clothing: kclo = 0.05 W m−1 K−1

Homework Equations


1/h = 1/h(surf) + 1/h(clothes) + 1/h(tissue)
h=k/d
ΔQ/Δt = hAΔT

The Attempt at a Solution


I think you need to find the h for surface, tissue and clothes, and combine using 1/h = 1/h(surf) + 1/h(clothes) + 1/h(tissue)
We can find h for clothes and tissue using h=k/d ?
Then can use ΔQ/Δt = hAΔT using the new h value, surface area (1.5) and temp difference (37-21=16)
But I keep getting 103 instead of 130 as the answer says
Can someone work it out and explain the working? Thanks in advance!
 
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  • #2
I get 127.

Chet
 

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