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Vapour-Compression Refrigeration Unit

The vapour-compression refrigeration system is the most common refrigeration system used today. RA1MKII is a computer controlled system, which enables the student to gain a thorough understanding of the refrigeration process.

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RA1MKII

REFRIGERATION & AIR CONDITIONING
RA1MKII Vapour-Compression Refrigeration Unit - Issue 1

The vapour-compression refrigeration system is the most common refrigeration system used today. RA1-MKII is a computer-controlled vapour-compression refrigeration system with automatic recording of all important process variables using an integral USB interface device.

Ordering Specification

  • Complete refrigeration system enabling demonstration of the vapour-compression refrigeration cycle
  • Fully instrumented to enable complete analysis of the processes involved and calculation of the changes in performance with operating conditions
  • Use of water as heat transfer medium in condenser and evaporator enables complete energy balance to be carried out and performance to be measured accurately
  • Computer-controlled system with automatic recording of process variables using an integral USB interface device
  • Compressor driven by three-phase motor with inverter drive, giving variable-speed and output torque measurement
  • Measurement sensors include:
    – 9x thermistor sensors measuring temperatures throughout the system
    – 2x electronic flow meters measuring flow of water through the condenser and evaporator
    – 2x electronic sensors and 2x Bourdon-type refrigerant gauges measuring pressures before and after the compressor
    – 1x variable area flow meter measuring refrigerant flow rate
  • Supplied with large water reservoir to isolate the process from fluctuations in temperature or pressure in the mains water supply
  • Comprehensive instruction manual supplied

Features

  • Complete vapour-compression refrigeration system with remote control, online monitoring and logging of results using a suitable PC
  • Compressor speed can be varied and torque measured via an inverter enabling changes in performance to be evaluated – speed and torque can be logged continuously
  • Condenser and evaporator use plate heat exchangers with water as the heat transfer medium enabling complete energy balance to be carried out and conditions in the condenser and evaporator to be varied accurately and independently using variable-speed pumps
  • Instrumented with electronic sensors measuring temperatures throughout the process, pressure on both sides of the compressor and water flow rate through the condenser and evaporator, enabling all of these parameters to be logged continuously
  • Bourdon-type refrigerant gauges indicate the pressure and corresponding refrigerant temperature on both sides of the compressor independent from the electronic systems
  • Large reservoir supplies water at stable temperature and pressure to the condenser and evaporator eliminating fluctuations
  • Expansion valve setting can be varied to change the operating point (superheat setting)

Demonstration Capabilities

  • Demonstration of the important features and operation of a vapour-compression refrigeration system, involving the combined processes of compression, condensation, expansion and evaporation
  • Analysis of the heat transfer processes in the condenser and evaporator heat exchangers involving phase changes in the refrigerant stream
  • Adjustment of the expansion valve to vary the operating point (superheat setting) to optimise the refrigeration process for different cooling loads
  • Investigation of the effect of the following system changes on the Coefficient of Performance:
    – Cooling water flowrate through the condenser
    – Heating water flowrate through the evaporator (system load)
    – The effect of adjusting the setting of the expansion valve
    – Compressor speed (refrigerant flow rate)
  • Modelling the system thermodynamically by plotting T-s and P-h diagrams using the properties for R134a refrigerant
  • Performing an energy balance across the system
  • The use of water as the heat transfer medium in the condenser and evaporator allows a complete energy balance to be carried out and performance to be measured accurately

RA1-MKII Vapour-compression refrigeration unit details

Description

The compressor is driven by a three-phase electric motor with an inverter drive that allows operation at different operating speeds. The inverter incorporates torque vector control and enables the speed and torque of the motor to be measured and logged by the controlling PC. Temperatures throughout the system and pressure on both sides of the compressor are measured and logged. The refrigerant flow rate is also measured by a variable-area flow meter.

The condenser and evaporator both consist of a brazed plate heat exchanger. The water cooled condenser and water heated evaporator utilise a large reservoir of water to minimise changes in water pressure or temperature during operation.

The use of water as the heat transfer medium in the condenser and evaporator enables a complete energy balance to be carried out and performance to be measured accurately.

The use of a reservoir to recirculate the same water continuously also eliminates the need for a permanent mains water connection or water flowing continuously to drain. The flow of water through each heat exchanger is independently varied by a variable-speed gear pump. The speed of both pumps is set by the operator using the PC.

The unit is totally self-contained, only requiring connection to an electrical supply and a suitable PC (not supplied). The unit is supplied with the necessary software and incorporates a USB computer interface device for connection directly to a PC.

The process components are mounted on a metal support frame that is designed to stand on top of the water reservoir. The water reservoir is designed to stand on the floor. Self-sealing quick-release connectors and flexible tubing connect the reservoir to the refrigeration unit.

Software Details

The software includes a range of functions and capabilities designed to make the operation of the equipment and processing of the results more straightforward, and also to enhance student understanding of the subjects being covered.

It includes:

  • Diagrammatic representation of the equipment, complete with continuous real time display of the various sensor outputs and instantaneous coefficient of performance
  • Automatic data logging of sensor values into spreadsheet format
  • Enables operator control of compressor speed (motor speed), condenser cooling water flow rate (pump speed) and evaporator heating water flowrate (pump speed)
  • Incorporates maximum and minimum temperature limits to protect the equipment against misuse
  • Additional USB driver is included that enables the outputs to be read in other software programs such as Labview™

Technical Details

Refrigeration system: Vapour-compression type using R134a refrigerant
Compressor speed range: 200-1,050rpm
Motor output power: 0.37kW
Condenser & evaporator: Brazed plate heat exchangers using water as heat transfer medium
Water reservoir: Working capacity 400l
Temperature sensors: Thermistor type, range -10 to 60°C
Refrigerant flow meter: Variable-area type, range 9-38 l/hr

Ordering Details

RA1-MKII-A/B/G
Vapour-compression refrigeration unit complete with separate floor-standing water reservoir and connections.

Essential Accessories

The system is designed to be used with a personal computer (not supplied).

The computer must have a USB connection available and run Windows 98 or above.

Complementary Products

RA2 Air Conditioning Unit
RA3 Air Conditioning Unit
TH1 Temperature Measurement and Calibration
TH2 Pressure Measurement and Calibration
TH3 Saturation Pressure
TH4 Recycle Loops
TH5 Expansion Processes of a Perfect Gas

Requirements

Electrical Supply:
RA1-A: 230V 1ph 50Hz 13 amp
RA1-B: 110V 1ph 60Hz 25 amp
RA1-G: 220V 1ph 60Hz 13 amp
Water supply:

Supply of cold water to fill reservoir (working capacity 400l), permanent connection to water supply is not required.

Personal Computer:

The system is designed to be used with a personal computer (not supplied). The computer must have a USB port and run Windows 98 or later.

Shipping Specification

Volume: 1.1m3
Gross weight: 125kg

Overall Dimensions

  Refrigeration unit (process: Water reservoir
Length: 0.52m 1.20m
Width: 0.95m 0.60m
Height: 0.50m 0.84m

Note: Refrigeration unit is located ot top of water reservoir when installed.