14.4 Heat Transfer Methods

14.4 Heat Transfer Methods

  • The reverse process releases energy, so that dry ice is an effective coolant.
    • The amount of energy required is the same as for other transitions.
  • The material presented in this section and the preceding section can be used to calculate any number of effects related to temperature and phase change.
    • To apply the appropriate equation, it is necessary to identify which temperature and phase changes are taking place.
    • Both temperature and phase changes can be caused by heat transfer and work.
  • Determine if there is a change in the temperature or phase by examining the situation.
    • When the presence or absence of a phase change is not obvious, you may want to look at the temperature change obtained and see if there were no phase changes.
    • If you can take you past a boiling or melting point, then you should do the problem in steps.
  • List all objects that change temperature and phase.
  • Identifying the unknowns will help determine exactly what needs to be determined in the problem.
    • A written list can be useful.
  • Make a list of what is given and what can be inferred from the problem.
  • The unknown is the appropriate equation for the quantity to be determined.
    • If there is a temperature change, the transfer of heat depends on the specific heat and the transfer of heat depends on the latent heat.
  • Get numerical solutions complete with units by substituting the knowns along with their units into the equation.
    • If there is more than one stage to the process, you will need to do this in steps.
  • The temperature change does not cause a phase change that you have not taken into account.
  • Solid phase of water is formed from ice crystals.
    • It takes a certain amount of time for enormous heat to be accumulated from the air, even if the air is above.
    • The warmer the air is, the quicker the snow will melt.
  • The methods by which heat transfer occurs are equally fascinating.
    • heat transfer occurs when there is a temperature difference.
    • The walls of a picnic ice chest can be used to transfer heat.
    • We can control rates of heat transfer by choosing materials, such as thick wool clothing for the winter, controlling air movement, or using a white roof to reflect summer sunlight.
    • It is hard to imagine a situation in which no heat transfer occurs.
    • Every process involving heat transfer takes three methods.
    • The heat from the electric burner of the stove is transferred to the bottom of the pan.
  • In weather systems, this type of transfer takes place in a forced-air furnace.
  • Warming of the Earth by the Sun is an example.
    • There is thermal radiation from the human body.