Answer: Calculate Time for Heat Loss to Rise to Normal

[Kcoats]

Suppose a man is losing heat at a rate of 300 W. His body temperature is 1.5 deg C below normal, and he begins to shiver. If his mass is 65 kg, how many hours will it take for his temperature to rise to normal?

Correct answer: 0.75 hrs
General feedback: First determine how much energy is required to increase the man's temperature to normal (remember you need the T change for this).
Second, determine the rate at which heat is entering the body, this will depend on the difference between the heat lost and the heat produced by shivering.
Now you can determine the time it takes for the body to gain enough heat to raise the temperature to normal.

Shivering=6.1kcal/min

6.1kcal/min (60 min)= 366kcal/hr=(.83kcal/kg deg C)(65kg)=53.95 Kcal deg C

I don't know what to do after this. Help?

 

[dextercioby]

You need to transform those kcal/hr in W.Can u do that...?


Daniel.

 

[thepatientmental]

After determining the rate of heat loss and the rate of heat production from shivering, you can calculate the net rate of heat loss by subtracting the two values. In this case, it would be 300 W - 53.95 Kcal deg C = 246.05 W. This is the rate at which the man's body is losing heat.

Next, you can calculate the amount of energy needed to raise the man's temperature to normal by using the specific heat capacity of the human body (0.83 kcal/kg deg C) and the temperature difference (1.5 deg C). This would be 0.83 kcal/kg deg C x 65 kg x 1.5 deg C = 81.23 kcal.

Finally, you can use the formula Q = mcΔT to calculate the time it takes for the man's temperature to rise to normal. Q is the energy needed (81.23 kcal), m is the mass (65 kg), and ΔT is the change in temperature (1.5 deg C). This would give you a total time of 0.33 hours or approximately 20 minutes.

Therefore, it would take approximately 20 minutes for the man's temperature to rise to normal. It is important to note that this is just an estimation and may vary depending on other factors such as the man's metabolism and the surrounding temperature.