Refrigeration – Compressors, Valves and Piping
The compressor is the element that represents the heart of the refrigerant circuit. Its purpose is to create, maintain and control the flow of refrigerant inside the refrigeration circuit, drawing in gas refrigerant at low pressure and low temperature, and delivering it at a higher pressure and temperature.
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Learning Objectives
• How compressors and ice makers operate • Types of compressors and ice makers • Troubleshooting compressors and ice makers • Ice quality • Ice maker sanitization
Specs
| Course Level | Intermediate |
| Languages | English |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
What is a “positive displacement” compressor?
These compressors draw in and discharge a fixed volume of gas on each cycle and produce a constant flow of gas, regardless of the discharge line pressure. There are two types, reciprocating and rotary, and both types are used in refrigeration systems.
What other types of compressors are there?
Dynamic compressors (like centrifugal compressors) accelerate the gas to increase its velocity and then restrict its flow to cause an increase in pressure. With these, the discharge flow changes as the discharge pressure changes.
What are some of the line size considerations in refrigeration system design?
Cost, pressure drop, and refrigerant velocities must all be considered, and the ultimate design usually requires some compromises.
Why is it important to minimize line lengths in refrigeration systems?
This helps reduce costs (of piping and refrigerant) and lowers pressure drops in the system, which improves the capacity and efficiency of the system.
Why aren’t capillary tubes used as expansion valves in every system, since they are low cost and easy to replace?
Capillary tubes are effective at throttling the refrigerant flow, but are not adjustable. So they are best suited to applications where the cooling load is relatively constant.
Sample Video Transcript
Reciprocating compressors (or piston compressors) consist of one or more intake valves (also called the intake manifold), one or more pistons in cylinders, exhaust valves, a crankshaft with connecting rods and bearings, and an oil sump or lubricating system. Compressors with multiple pistons are classified by the letter that resembles the arrangement of their pistons (for example, “V” or “W”). The pistons are driven in a reciprocating action by the crankshaft and connecting rods, and the intake and exhaust valves open and close in response to pressure changes inside the cylinders. The crankshaft is usually driven by an electric motor. In smaller units, the crankshaft and connecting rods are often lubricated by “splashing” oil from an oil sump. Higher capacity units often have a pressurized lube system.
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