Vapour Compression Refrigeration Trainer

The vapour compression cycle is the most examined topic in refrigeration courses and the least touched — students draw the p-h diagram repeatedly but rarely stand in front of a running loop with gauges. Commercial trainers are costly and usually locked in the thermal lab, so the cycle stays theoretical. This project builds a student-scale trainer: a hermetic compressor, a finned-tube condenser, a capillary-tube expansion device and an evaporator coil inside a transparent cold chamber, all piped in copper and mounted on a panel with suction and discharge pressure gauges and thermometers. The student starts the unit, watches the discharge pressure climb and frost form on the evaporator, logs the four key temperatures and two pressures over time, and works out the COP from their own data using the procedure's worksheet.

1. The trainer is switched on and the student traces the refrigerant path on the panel: compressor → condenser → capillary tube → evaporator → back to the compressor.
2. As the unit runs, the discharge gauge climbs, the condenser warms up, and frost begins forming on the evaporator coil inside the cold chamber.
3. The student logs suction and discharge pressures plus the four thermometer readings at fixed time intervals until the chamber temperature stabilises.
4. The cooling curve (chamber temperature vs time) is plotted from the log, showing the pull-down behaviour of the cycle.
5. Using the worksheet, the student computes the refrigerating effect and the coefficient of performance from their own pressure–temperature data.
6. The run is repeated with the chamber door briefly opened (a controlled load change) to show how the cycle responds, and both runs are compared in the report.

Tech stack:

• Hermetic compressor unit
• Finned-tube condenser
• Capillary tube expansion device
• Evaporator in acrylic cold chamber
• Suction and discharge pressure gauges
• Thermometer measurement points
• Brazed copper piping with service valves
• COP experiment manual and worksheet

• [Hermetic compressor] A sealed compressor unit forms the heart of the loop, mounted on anti-vibration pads with its electricals wired to the panel switch.
• [Finned-tube condenser] A finned copper-tube condenser rejects heat to the room air, visibly warm to the touch while running.
• [Capillary tube expansion] A capillary tube meters the refrigerant into the evaporator — the simplest expansion device, ideal for studying the throttling process.
• [Transparent cold chamber] The evaporator coil sits inside a clear acrylic chamber so frost formation and cooling are directly visible during the run.
• [Suction and discharge gauges] Two panel pressure gauges read the low and high sides of the cycle continuously.
• [Thermometer points] Thermometers at the compressor suction/discharge, condenser outlet and inside the cold chamber capture the four key temperatures.
• [Copper piping with valves] The full circuit is brazed copper with service valves, laid out on the panel so the refrigerant path can be traced by hand.
• [COP worksheet] The experiment manual walks through logging, plotting the cooling curve, and computing the coefficient of performance from the student's readings.

• Assembled vapour compression refrigeration trainer (full circuit on panel)
• Hermetic compressor with panel switch and wiring
• Suction and discharge pressure gauges
• Thermometers at four measurement points
• Transparent evaporator cold chamber
• Piping layout drawing and component list
• Experiment manual with logging sheets and COP worksheet
• Project report PDF (background, cycle theory, build, experiment methodology, results format)
• PPT presentation for final review
• Viva Q&A preparation document (vapour compression cycle, COP, capillary vs TXV, subcooling/superheat)

• A teaching trainer, not a commercial refrigeration unit — cooling capacity is sized for the demo chamber, not for practical refrigeration loads.
• The COP is computed by the student from their own readings; no COP figure is claimed for the trainer itself.
• Room temperature and humidity affect pull-down time and frost formation — the manual asks the student to record ambient conditions with each run.
• Refrigerant charging and any service work are builder-side only; the student unit is sealed and needs no handling of refrigerant.
• Pressure gauges are dial instruments with normal reading uncertainty; the worksheet includes an uncertainty note the student completes.