Refrigerators, Ice Boxes and Heat Transfer

lce and EnergY Transfer
Keepingourhomescomfortableandourfoodfromspoiling
involves the transfer of heat. In some cases we want to encourage
heat transfer, while in other cases we want to prevent it'
Think of the old-fashioned icebox in terms of desirable and
undesirable transfers of heat as you answer the questions
that follow the reading.
It's the hottest day of the summer. Your friend comes to visit, and
the two of you decide to go outside and relax' 0n your way
outside, you decide to stop in the kitchen for some cool drinks.
take
You open the refrigerator and find some ice-cold sodas. You
the sodas outside and alternate between sipping your cool drink
and holding it against your hot forehead. some of the heat from
your body transfers to the cool drink. lt feels great'
Living in the 2oth century has some distinct advantages, including
the availability of modern refrigerators, The refrigerator is
America's most common appliance.
lt is found in more than
99.5%
of all homes in the United States. Refrigeration helps us to enjoy
cool drinks on hot days. More importantly, it helps prevent food
from spoiling.
Activity 52
lce ond Energy Transfer
Food spoilage has always been a health risk. ln the past, food
poisoning resulted in many more cases of illness and death than
today. However, even today, public health officials believe that
millions of people suffer from food poisoning in the United States
each year. While most people recover in a day or two, some
people, especially children, the elderly, or those weakened by
other illnesses, die as a result of lood poisoning. Refrigeration and
freezing are two of the best ways to prevent food from spoiling.
0nly refrigeration maintains the taste of fresh food. Other
methods change the flavor and texture of the food.
Long ago snow and ice, cool streams, springs, caves, and cellars
were used to refrigerate food. The Chinese cut and stored ice in
rooo B.c. About A.D. rJoo, Marco Polo described ices and sherbets
he had eaten in the Far East. The idea of "manufacturing" ice dates
back to Venice in the r6th century, when it was discovered that
adding salt to ice produced a slushy brine that remained below
the freezing temperature. This could then be used to freeze clear
water into solid ice. This is also the old-fashioned way of making
ice cream.
In the United States, using ice to preserve food in homes became
popular in the mid-r8oos. At first, the ice trade provided "natural"
ice from northern lakes and rivers to cities in the south.
Eventually wooden ice boxes lined with tin or zinc and insulated
with various materials including cork, sawdust, and seaweed were
used to hold blocks of ice to "refrigerate" food. A drip pan
collected the meltwater-and had to be emptied daily.
A good icebox prevented transfer of heat from the surrounding
room while allowing for good transfer of heat from the food to the
ice. One problem with iceboxes was that the ice had to be
replaced every few
days.
I
Warm winters in rBBg and r8go resulted in severe shortages o[
natural ice in the United States. This increased the use of
mechanical refrigeration for the dairy and meat packing industries
and for the freezing and storage oi tish. Commercial refrigeration
Activity 52
Ice and EnergY Transfer
used in
techniques were also applied to railroad cars and were
"coolers" in grocery stores as well as in various ways in the
tl
textile, paper, drug, soap, liquid gas, sugar, and'munitions
industries.
on the u.s.
Mechanical refrigerators for the home began to appear
marketbetweentgroandrgr5.Byrg3o,halfofthehomesinthe
united states had refrigerators. Thii'number increased to 85% by
1944. lt's hard to imagine life without one, isn't it?
q
Questions
a
I.
Draw a picture of a room with an icebox containing a block
of ice. Think of the room, the icebox, the ice, and the food
as a system. The icebox is a smaller system within the larger
system of the room. On your diagram, use arrows to show
all of the heat transiers possible between parts of the large
to
system. use a solid line to represent transfers that help
keep the food cold. Keeping in mind.that the purpose of the
icebox was to keep food cold, indicate for each arrow
whether the heat transfer it shows contributed to that
purpose. Explain whY.
In order to make the ice in an icebox last longer, some
peoplewouldwrapablanketornewspapersaroundtheice
to keep it from melting. Keeping in mind that the purpose
oi the icebox is cooling food, explain why this was or was
not a good idea. Use a diagram like the one you used for
0uestion I to explain Your answer'