RA Series: REFRIGERATION & AIR CONDITIONING
RA1 Vapour-Compression Refrigeration Unit - Issue 1
The vapour-compression refrigeration system is the most common refrigeration
system used today.
RA1 is a computer controlled vapour-compression refrigeration system with automatic
recording of appropriate process variables using an integral USB interface
device. This allows the student to gain a thorough understanding of the refrigeration
process by changing the operation of different parts of the process and recording
the response of the complete system.
ORDERING SPECIFICATION
• Complete refrigeration system allowing demonstration of the vapour-compression refrigeration cycle
• Fully instrumented to allow 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 allows 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 flowmeters 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 flowmeter measuring refrigerant flowrate
• 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, on-line monitoring and logging of results using a suitable PC
> Compressor speed can be varied and torque measured via an inverter allowing 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 allowing 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 flowrate through the condenser and evaporator, allowing 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.
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 allows 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 flowmeter.
The condenser and evaporator both consist of a brazed plate heat exchanger. The water cooled condenser and water heated evaporator utilize a large reservoir of water to minimize changes in water pressure or temperature during operation.
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.
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
– Allows operator control of compressor speed (motor speed), condenser cooling water flowrate (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 allows 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 to 1050 RPM
Motor output power
0.37 kW
Condenser & evaporator
Brazed plate heat exchangers using water as heat transfer medium
Water reservoir
Working capacity 400 litres
Temperature sensors
Thermistor type, range -10 to 60ºC
Refrigerant flowmeter
Variable area type, range 9 -38 l/hr
Ordering details
RA1-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:
Single phase electrical supply:
RA1-A: 230V/ 1ph / 50Hz @ 13 Amps
RA1-G: 220V / 1ph / 60Hz @ 13 Amps
G version has optional 1.5kVA transformer available to accommodate 120V/1Ph/60Hz supply.
Water Supply:
Supply of cold water to fill reservoir (working capacity 400 litres), permanent connection to water supply or drain is not required.
Shipping specification
Volume: 1.1m3
Gross weight: 125kg
Overall dimensions
Refrigeration unit (process)
Length: 0.95m
Width: 0.52m
Height: 0.50m
Water reservoir
Length: 1.2m
Width: 0.6m
Height: 0.84m
note: Refrigeration unit is located ot top of water reservoir when installed.
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