Modern Engineering Thermodynamics

540 CHAPTER 14: Vapor and Gas Refrigeration Cycles
IS IT CALLED AN ICEBOX OR A REFRIGERATOR?
An icebox was a wooden box that contained both ice and food to be preserved (Figure 14.5). Originally, the ice was put on
the bottom and the food on the top. But eventually it was realized that this was inefficient because the cold air is heavier
than warm air. Thereafter, the ice was put in the top of the icebox and the food was always placed below it, so that the
heavier cold air could circulate around the food. The icebox was invented in 1803 and manufactured in the United States
until 1953. Ice needed to be added every day or two in the original iceboxes. But, by 1923, improved thermal insulation
design required ice to be added only every five to seven days.
Block of ice
Food
storage
area
FIGURE 14.5
Domestic icebox.
Drain pan
The term refrigerator is reserved for a device that does not use ice to produce cold temperatures, even though the device may
be used to preserve food (Figure 14.6). There are vapor-compression refrigerators, gas expansion refrigerators, thermoelectric
refrigerators, and so forth.
Evaporator
Compressor
Condenser
Throttle
valve
Room
temperature
72°F (22°C)
Refrigerator
temperature
35°F (1.5°C)
Refrigerant
storage
High-pressure vapor
Low-pressure vapor
High-pressure liquid
Low-pressure liquid
FIGURE 14.6
Domestic refrigerator.