Lesson 1 - Introduction to Evaporators
Topics:
Evaporator operation; Latent and sensible heat; Evaporator capacity; Temperature differential; Circulation velocity
Learning Objectives:
– Explain the function of the evaporator in a refrigeration system.– List five main factors affecting evaporator capacity, and explain how each can be optimized to gain the greatest possible evaporator capacity.
– Describe the basic evaporator configurations.
– Explain the function of headers and distributors in multiple-circuit evaporators.
– Explain how comfort coolers reduce both air temperature and humidity.
Lesson 2 - Direct Expansion Evap. & Secondary Refrig.
Topics:
Dry and flooded evaporators; Evaporator configurations; Secondary-refrigeration systems; Multiple staging; Cascade systems
Learning Objectives:
– Compare and contrast dry-expansion and flooded evaporators.– List the main types of flooded evaporators.
– Explain the process of secondary refrigeration.
– Define eutectic solution and eutectic temperature.
– Describe three types of multiple-evaporator systems.
– Identify cascade and multiple-staging refrigeration systems.
Lesson 3 - Improving Evaporator Performance
Topics:
Net refrigeration effect; Superheating; Subcooling; Accumulators; Heat exchangers; Headers; Oil separation
Learning Objectives:
– Explain how the laws of thermodynamics apply to refrigeration.– Describe how to increase the net refrigerating effect of an evaporator.
– Demonstrate-using simple arithmetic-the amount of increase in net refrigerating effect caused by subcooling.
– List several advantages of using a heat exchanger in a refrigeration system.
– Describe three ways of keeping oil out of an evaporator.
– Explain why the circulation of air or water through an evaporator coil improves evaporator performance.
Lesson 4 - Defrosting, Maint., & Troubleshooting Evaporators
Topics:
Manual, ambient air, heated air, water, brine, hot-gas, reverse-cycle, and electric defrost methods; Cleaning coils; Frost problems; Troubleshooting
Learning Objectives:
– Explain why periodic defrosting of evaporator coils is necessary.– List and describe at least five different methods of defrosting an evaporator.
– Explain the differences between the hot-gas and reverse-cycle defrost methods.
– Explain how to clean an evaporator coil, drain pan, and drain line.
– Describe how to remove rust, scale, and sludge from shell-and-tube evaporators.
– List two ways evaporator coils can be winterized.
– Tell how low airflow and excessive moisture increase frost buildup on coil surfaces.
– Explain how dirty coils and damaged fins reduce an evaporator's cooling capacity.
Lesson 5 - Metering Device Types, Maint. & Troubleshooting
Topics:
Hand-operated, automatic, thermostatic, and thermal-electric expansion valves; Capillary tubes; Float valves; Maintenance and troubleshooting
Learning Objectives:
– Explain the primary function of a metering device.– Name the five main types of expansion valve, and describe the operation of each.
– Contrast the operation of an internally equalized and an externally equalized TXV.
– Explain how to adjust the superheat on a TXV.
– Describe the structure, operation, and application of high- and low-side float valves.
– Identify three causes of floodback and describe the corrective action for each.
– List the common problems of TXVs along with their solutions.
