Chapter 1
BASICS OF HEAT TRANSFER

Thermodynamics and Heat Transfer

1-1C Thermodynamics deals with the amount of heat transfer as a system undergoes a process from one equilibrium state to another. Heat transfer, on the other hand, deals with the rate of heat transfer as well as the temperature distribution within the system at a specified time.

1-2C (a) The driving force for heat transfer is the temperature difference. (b) The driving force for electric current flow is the electric potential difference (voltage). (a) The driving force for fluid flow is the pressure difference.

1-3C The caloric theory is based on the assumption that heat is a fluid-like substance called the "caloric" which is a massless, colorless, odorless …ver más…

1-13E A logic chip in a computer dissipates 3 W of power. The amount heat dissipated in 8 h and the heat flux on the surface of the chip are to be determined.
Assumptions Heat transfer from the surface is uniform.
Analysis (a) The amount of heat the chip dissipates during an 8-hour period is
Logic chip

(b) The heat flux on the surface of the chip is

1-14 The filament of a 150 W incandescent lamp is 5 cm long and has a diameter of 0.5 mm. The heat flux on the surface of the filament, the heat flux on the surface of the glass bulb, and the annual electricity cost of the bulb are to be determined.
Assumptions Heat transfer from the surface of the filament and the bulb of the lamp is uniform .

Lamp
150 W
Analysis (a) The heat transfer surface area and the heat flux on the surface of the filament are

(b) The heat flux on the surface of glass bulb is

(c) The amount and cost of electrical energy consumed during a one-year period is

Iron
1200 W
1-15 A 1200 W iron is left on the ironing board with its base exposed to the air. The amount of heat the iron dissipates in 2 h, the heat flux on the surface of the iron base, and the cost of the electricity are to be determined.
Assumptions Heat transfer from the surface is uniform.
Analysis (a) The amount of heat the iron dissipates during a 2-h period is (b) The heat flux on the surface of the iron base is

(c) The cost of electricity