me320hw2keyUpdated

# Plot of power as a function of time a find the time

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ot of power as a function of time: a. Find the time rate change of system energy at t=0.6 hours in kW. Start with the first law for a closed system: Next, evaluate this equation at t=0.6 hours. To do this, plug in the values for the heat transfer rate and the power output at this time (in hours). b. Determine the change in system energy after 2 hours. To do this, first integrate the energy balance equation. Remember to split up the integral for power, because it is a piecewise function. Also, remember that we are integrating over time in seconds, so a unit conversion from hours to seconds must be made to the first power integral (divide t by 3600). Next, evaluate the integrals: Also, the work output can be calculated by simply measuring the area under the curve for the plot of power as a function of time. 4. Surfaces: Person(1), Surroundings (2) Assume: emissivity, ε=1 Given: Surface area of body, A=1.7 m2 Temperature of person’s body, T1: 98.6 °F=310 K Temperature of surroundings, T2: 20 °C=293 K Boltzmann constant, σ=5.67e-08 W/m2K4 Find: Rate of heat transfer from the body to the surroundings Governing equation: Quantitative solution:...
View Full Document

Ask a homework question - tutors are online