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Series 460: Ammonia Refrigeration
Course 461: Ammonia Refrigeration Basics
Covers all aspects of using ammonia as a
refrigerant. Describes both single-stage and two-stage
ammonia systems. Explains the importance of
accumulators and intercoolers in ammonia
refrigeration. Concludes with coverage of liquid
recirculation system operation.
Available Media: E-Learning, Self-Study
Textbook, Pre- and Post- Tests
Lesson 1, Ammonia Characteristics
Topics: Ammonia sources, uses, and chemical
characteristics; Environmental, hazardous material
concerns; Temperature-pressure relationships;
Materials compatibility; MSDS criteria; Safety
Learning Objectives: After studying this
lesson, you should be able to Name common uses of
ammonia and describe benefits of ammonia refrigerant
in terms of ozone depletion and global warming
potentials (ODP and GWP). Describe the properties of
ammonia and explain how they affect the use of ammonia
as a refrigerant. Discuss the toxicity and
flammability of ammonia and its classification as a
hazardous material. Discuss important features of
ammonia saturation curves, reactions with metals, and
MSDS criteria. Name two standards governing ammonia
refrigeration systems and describe the four main
ammonia safety concerns, steps for their prevention,
and first aid treatment in the event of exposure.
Lesson 2, Single-Stage Ammonia Systems
Topics: Positive-displacement systems;
Refrigeration loads; Primary, secondary refrigeration
system components; Components in parallel; Superheat;
Single-stage pressure-enthalpy diagram
Learning Objectives: After studying this
lesson, you should be able to
- Briefly compare absorption and mechanical
compression systems, compare dynamic and
positive-displacement compressors, and name those
generally used in industrial ammonia refrigeration
systems.
- Explain how a positive-displacement compressor
increases the ammonia vapor pressure.
- Define British thermal unit (Btu), specific
heat, sensible heat, latent heat, and tons of
refrigeration.
- Name four primary components in single-stage
ammonia refrigeration systems and describe their
functions.
- Describe the functions of the oil separator,
high-pressure liquid receiver, king valve, and
suction accumulator in single-stage ammonia
refrigeration systems.
- Define superheat, enthalpy, and entropy and
explain how they are used on the pressure-enthalpy
(P-H) diagram.
Lesson 3, Two-Stage Ammonia Systems
Topics: Compression ratio; Compressor
capacity; Two-stage system division, Booster
desuperheater, intercooler; Two-stage system
components, performance; Complex two-stage systems
Learning Objectives: After studying this
lesson, you should be able to
- Define compression ratio and explain its
importance in single-stage and two-stage
industrial ammonia refrigeration systems.
- Explain why flash gas removal, booster
discharge-vapor desuperheating, and interstage
liquid cooling are desirable in the two-stage
system.
- Plot a two-stage refrigeration system on an
ammonia pressure-enthalpy (P-H) diagram.
- Name the primary and secondary components of a
two-stage refrigeration system and describe
component functions.
- Explain why a two-stage system requires less
overall power than a single-stage system.
Lesson 4, Suction Accumulators and
Intercoolers
Topics: Need for suction accumulators;
Accumulator design features; Liquid/vapor
separation; Intercoolers; Shell-and-coil vs flash
intercoolers; Alternate intercoolers
Learning Objectives: After studying this
lesson, you should be able to
- Explain why suction accumulators are needed and
describe the damage that can result from liquid
entering the compressor.
- Discuss the purposes and reasoning behind the
design features, including the boil-out coil, of
suction accumulators.
- Describe the various ammonia refrigerant
liquid/vapor separation criteria.
- Explain how the intercooler deals with flash gas
and desuperheats the booster discharge.
- Describe basic differences between a flash
intercooler and a shell-and-coil intercooler.
- Describe typical configurations for alternate
intercoolers provided with internally compounded
compressors.
Lesson 5, Liquid Overfeed (Recirculation)
Systems
Topics: Liquid overfeed, recirculation
systems; Recirculation system advantages and
disadvantages; Recirculation vessel design; Pumper
drum system; Controlled pressure receiver system
Learning Objectives: After studying this
lesson, you should be able to
- Describe the various functions performed within
the recirculation vessel.
- Discuss the advantages and disadvantages of
recirculation systems.
- Describe design features of horizontal and
vertical recirculation vessels.
- Discuss the surge-volume requirements of a
recirculation system and reasons for high-level
alarm/cutout controls on the recirculation vessel.
- Describe the features and drawbacks of various
kinds of liquid-refrigerant pumps.
- Describe the operation of pumper drum
(gas-pressure) recirculation systems and
controlled pressure receiver (CPR) recirculation
systems.
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