Calculate the power temperature

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SUMMARY

The discussion centers on calculating the power generated by humans converting a 2000 kcal daily diet into heat and its effect on room temperature. The calculations indicate that the initial power estimate of 2.3 W is incorrect due to misinterpretation of time units and energy conversion. The correct approach involves understanding the relationship between energy, time, and the specific heat capacity of air, which is treated as a diatomic gas with a specific heat capacity of 20.8 kJ/moleK. The volume of the room and the number of occupants are critical for determining the temperature increase over a specified period.

PREREQUISITES
  • Understanding of thermodynamics, specifically the concepts of power and energy conversion.
  • Familiarity with specific heat capacity and its calculation for diatomic gases.
  • Knowledge of basic physics equations related to heat transfer and temperature change.
  • Proficiency in unit conversions, particularly between kcal, kJ, and watts.
NEXT STEPS
  • Research the calculation of temperature change using the formula ΔT = Q/(m*c) where Q is heat energy, m is mass, and c is specific heat capacity.
  • Learn about the properties of diatomic gases and their specific heat capacities in different conditions.
  • Explore the concept of energy balance in closed systems to understand heat generation and dissipation.
  • Investigate the implications of human metabolic rates on environmental temperature in enclosed spaces.
USEFUL FOR

This discussion is beneficial for physics students, environmental scientists, and engineers interested in thermodynamics, heat transfer, and energy efficiency in enclosed environments.

JQ10
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Edit: Topic title should read power and temperature

Homework Statement



Humans convert most of a 2000 kcal typical daily diet into heat. Calculate the power. What is the increase of temperature in a room with a volume of 15000 m^3 filled with 250 people over a 60 minute period?

Note: Power is defined as energy/time.
1kcal = 4.186kJ.
density of air = 1.29kg/m^3
molar mass of air = 29g
Treat air as a diatomic gas


Homework Equations



C = change in internal energy/ number of moles * change in temperature = f/2*R



The Attempt at a Solution



60 * 60 = 3600

2000 * 4.186 = 8372kJ/3600s = 2.3kJ/s = 2.3W

Specific Heat Capacity = 5/2 * R = 5/2 * 8.31 = 20.8 kJ/moleK

I'm really struggling with where to take it from there. I'd guess you would either use change in internal energy/ number of moles * change in temperature or use average kinetic energy = 5/2kT = 1/2mv^2rms but I'm not sure how to calculate the relevant data for either plus that doesn't use all the information given.
 
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JQ10 said:
Humans convert most of a 2000 kcal typical daily diet into heat.
60 * 60 = 3600
2000 * 4.186 = 8372kJ/3600s = 2.3kJ/s = 2.3W

I have not played with attempting the find the specific heat of air before so I'll let someone else help you there. I can tell you that the power involved is not 2.3 W because there are not 3600 seconds in a day. Note that the problem said "daily." And a watt is not equal to kJ/s but J/s. Due to those two errors, your power is small by an order of magnitude.
 
Thank you for the help.
 

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