Refrigeration & Air Conditioning Technology, 8e - 39

Unit 3
RefRigeRation and RefRigeRants
O B J E C T I V E S
After studying this unit, you should be able to
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discuss applications for high-, medium-, and low-temperature
refrigeration.
describe the term ton of refrigeration.
describe the basic refrigeration cycle.
explain the relationship between pressure and the boiling
point of water or other liquids.
describe the function of the evaporator or
cooling coil.
explain the purpose of the compressor.
list the compressors normally used in residential
and light commercial buildings.
discuss the function of the condensing coil.
state the purpose of the metering device.
list four characteristics to consider when choosing
a refrigerant for a system.
list the designated colors for refrigerant cylinders for various
types of refrigerants.
discuss different refrigerants and their applications.
describe how refrigerants can be stored or processed while
refrigeration systems are being serviced.
plot a refrigeration cycle for refrigerants (R-22, R-134a,
and R-502) on a pressure/enthalpy diagram.
plot a refrigeration cycle on a pressure/enthalpy diagram
for refrigerant blends R-404A and R-410A.
plot a refrigeration cycle on a pressure/enthalpy diagram
for a refrigerant blend (R-407C) that has a noticeable
temperature glide.

✔✔Areas in which there is the potential for refrigerant leaks should be
properly ventilated.
✔✔Extra precautions should be taken to ensure that no refrigerant leaks
occur near an open flame.
✔✔Refrigerants are stored in pressurized containers and should be
handled with care. Goggles with side shields and gloves should be
worn when checking pressures and when transferring refrigerants
from the container to a system or from the system to an approved
container.

3.1 INTRODUCTION
TO REFRIGERATION
This unit is an introduction to refrigeration and refrigerants. The term refrigeration is used here to include both the
cooling process for preserving food and comfort cooling
(air-conditioning).
Preserving food is one of the most valuable uses of
refrigeration. The rate of food spoilage gets slower as
molecular motion slows, which retards the growth of bacteria that causes food to spoil. Below the frozen hard point,
which for most foods is considered to be 0°F, food-spoiling
bacteria stop growing. The food temperature range between
35°F and 45°F is known in the industry as medium temperature; below 0°F is considered low temperature. These
ranges are used to describe many types of refrigeration
equipment and applications. Refrigeration systems that
operate to produce warmer temperatures are referred to as
high-temperature refrigeration systems. Comfort cooling
systems, commonly referred to as air-conditioning systems,
are used, for example, to cool our homes and commercial
spaces and are classified as high-temperature refrigeration
systems.
For many years dairy products and other perishables
were stored in the coldest room in the house, the basement,
the well, or a spring. In the South, temperatures as low as
55°F could be maintained in the summer with underground
water, which would extend the time that some foods could
be kept. In the North, and to some extent in the South, ice
was placed in "ice boxes" in kitchens. The ice melted when
it absorbed heat from the food in the box, cooling the food,
Figure 3.1.
In the early 1900s, ice was manufactured by mechanical refrigeration and sold to people with ice boxes, but still
only the wealthy could afford it. Also in the early 1900s,
some companies manufactured a household refrigerator.
Like all new items, it took a while to become popular. Now,
most houses have a refrigerator with a freezing compartment. Modern refrigerators have become state-of-the-art
appliances-and some models even include automatic beverage and ice dispensers, built-in television screens, and connections to the World Wide Web.
Frozen food was just beginning to become popular
about the time World War II began. Because most people



Refrigeration & Air Conditioning Technology, 8e

Table of Contents for the Digital Edition of Refrigeration & Air Conditioning Technology, 8e

Contents
Refrigeration & Air Conditioning Technology, 8e - Cover1
Refrigeration & Air Conditioning Technology, 8e - Cover2
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Refrigeration & Air Conditioning Technology, 8e - Cover4
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