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
4
0

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!
 
Physics news on Phys.org
  • #2
I get 127.

Chet
 

1. How does heat transfer occur through different layers of the body?

Heat transfer through different layers of the body occurs through three main mechanisms: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between objects or materials. Convection is the transfer of heat through the movement of fluids, such as blood or air. Radiation is the transfer of heat through electromagnetic waves.

2. What role does h play in heat transfer from the body?

h, or the heat transfer coefficient, represents the efficiency of heat transfer between the body and its surroundings. It takes into account factors such as the material properties, surface area, and temperature difference between the body and its surroundings. A higher h value means that heat transfer will occur more quickly.

3. How does temperature (T) affect heat transfer through layers of the body?

The temperature difference between the body and its surroundings is a driving force for heat transfer. The greater the temperature difference, the faster heat will transfer through the layers of the body. This is why our bodies feel colder in colder environments, as heat is transferred more quickly to the colder surroundings.

4. What is the significance of d in heat transfer through layers of the body?

d, or the thickness of the layer, affects the rate of heat transfer through conduction. Thicker layers of tissue or clothing will slow down the rate of heat transfer, as heat has to travel a longer distance. This is why wearing multiple layers of clothing can help to keep us warm in colder environments.

5. How does surface area (A) impact heat transfer through layers of the body?

The larger the surface area, the more heat can be transferred through convection and radiation. This is why our bodies have a larger surface area in the form of skin and hair, to aid in heat transfer and regulate our body temperature. Additionally, wearing tight-fitting clothing can decrease the surface area and lead to a slower rate of heat transfer.

Similar threads

Heat Transfer: Effect of a Heat Fin
    • Introductory Physics Homework Help
Replies
4
Views
1K
Modeling a kongming lantern (sky lantern)
    • Introductory Physics Homework Help
Replies
6
Views
1K
I Generate heat conduction curves at different time steps
    • Thermodynamics
Replies
7
Views
233
Heat transfer through a cylindrical shell
    • Introductory Physics Homework Help
Replies
3
Views
2K
Two rods are connected one silver and the other gold.
    • Introductory Physics Homework Help
Replies
3
Views
7K
Calculating thickness of insulation, rate of T rise and fall
    • Introductory Physics Homework Help
Replies
6
Views
2K
Rate body temperature increases given rate of heat transfer?
    • Introductory Physics Homework Help
Replies
1
Views
6K
I Warm-up time for a hollow cylinder
    • Thermodynamics
Replies
5
Views
1K
I 1D Heat Transfer Analytical Wall
    • Thermodynamics
Replies
3
Views
1K
Engineering Average heat transfer coefficient (forced convection)
    • Engineering and Comp Sci Homework Help
Replies
6
Views
2K

Hot Threads

Recent Insights

Back
Top