Calculating Rate of Vaporisation: 240 W Body Heat Loss

In summary, the question asks for the rate of vaporisation of sweat based on the amount of heat lost during exercise and the latent heat of sweat. The formula L=Q/m can be used to find the rate, which is equal to 106 mg/s. Another way to solve this is through logic, recognizing that 240 W is equivalent to 240 J/s and that 2255 kJ/kg is equivalent to 2255000 J/kg. Therefore, the rate of vaporisation would be 240 J/s divided by 2255000 J/kg, which also equals 106 mg/s.
  • #1
roam
1,271
12

Homework Statement



During exercise the body loses 240 W of heat due to the evaporation of sweat. Assuming that the latent heat of at body temprature is 2255 kJ/kg, determine the rate of vaporisation of sweat.

answer = 106 mg/s

Homework Equations



L=Q/m

The Attempt at a Solution



What formula do I need to use here? The only formula I can think of is the one with latent heat and heat energy Q=mL. But this formula only gives mass and doesn't give the rate of vaporisation!
 
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  • #2
If 240J is added to the sweat per second and it takes 2255 000 J to vaporize one kg of sweat, how much is vaporized per second? You don't need any formulas, just logic.
 
  • #3
ideasrule said:
If 240J is added to the sweat per second and it takes 2255 000 J to vaporize one kg of sweat, how much is vaporized per second? You don't need any formulas, just logic.

I'm not quite sure if I understand correctly, do you mean sweat+240J/2255000? :confused:
 
  • #4
And it is 240 W not Joules...
 
  • #5
roam said:
And it is 240 W not Joules...

a Watt is just a Joule per second.
 

1. How is the rate of vaporisation calculated?

The rate of vaporisation is calculated by dividing the body's heat loss (in watts) by the specific heat of vaporisation of water (2.26 x 10^6 J/kg).

2. What is the significance of calculating the rate of vaporisation?

Calculating the rate of vaporisation helps determine the efficiency of the body's cooling mechanism and can provide insights into the body's thermoregulatory function.

3. What factors can affect the rate of vaporisation?

The rate of vaporisation can be affected by factors such as ambient temperature, humidity, wind speed, and the surface area of the body exposed to the environment.

4. How does the body regulate the rate of vaporisation?

The body regulates the rate of vaporisation through physiological mechanisms such as sweating, shivering, and changes in blood flow to the skin.

5. Can the rate of vaporisation be used to determine an individual's level of physical exertion?

Yes, the rate of vaporisation can be used as an indicator of physical exertion as the body's heat production and heat loss increase during exercise, leading to a higher rate of vaporisation.

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