The components of the heat pump and its instrumentation are mounted on a high quality ABS plastic panel.
The heat pump consists of a hermetic compressor, an insulated coiled concentric tube water cooled condenser, a liquid receiver, a thermostatically controlled expansion valve and air heated evaporator.
The components are clearly but compactly arranged in a manner similar to that used for many domestic air-water heat pumps and all are visible from the front of the unit.
The operating cycle is as follows:
Slightly superheated Refrigerant R134a vapour enters the compressor from the evaporator and its pressure is increased. This brings about a rise in temperature and the hot vapour enters the water cooled condenser. Heat is given up to the cooling water and the refrigerant condenses to a liquid before passing to the liquid receiver and then the expansion valve.
On passing through the expansion valve the pressure of the liquid refrigerant is reduced, causing the saturation temperature to fall to below that of the atmosphere. Thus, as it flows through the evaporator, there is a temperature difference between the refrigerant and the air being drawn across the coils. The resulting heat transfer causes the refrigerant to boil, and on leaving the evaporator it has become slightly superheated vapour, ready to return to the compressor. The degree of superheat is automatically controlled by the expansion valve, which may be adjusted.
The temperature at which heat is delivered in the condenser is controlled by the water flow rate and its inlet temperature. Water may be delivered at up to 50ºC.
The evaporating temperature is largely determined by the ambient conditions of temperature and humidity. However, a limited variation is possible, either by restricting the air intake to the evaporator, or by directing warmed air towards the intake. (The air inlet temperature should not be allowed to exceed 35ºC to avoid overloading the compressor.)
Variable area flowmeters on both the refrigerant and cooling water circuits, an electrical energy meter recording power input to the compressor and a digital electronic thermometer recording all relevant temperatures, allow an interesting and comprehensive range of experiments to be conducted.
A fully instrumented bench top air to water heat pump operating on the mechanical vapour compression cycle with Panel: High quality ABS plastic panel on which the following components are mounted.
Refrigerant: R134a (HFC134a)
Compressor: Fully hermetic single cylinder reciprocating type. Displacement 8.85 cm3 rev-1
Condenser: Refrigerant to water. Insulated coiled concentric copper tube type.
Liquid Receiver: With valves. Contains entire refrigerant charge if required.
Evaporator: Air to refrigerant. Serpentine copper tube with aluminium fins and with integral fan.
Digital Thermometer: Resolution 0.1ºC, with switch to select from six thermocouples.
Flow Meters (2): Variable area type – to indicate R134a and H2O flow rates.
Pressure Gauges (2): To indicate R134a pressures in evaporator and condenser.
Electrical Energy Meter: Watt-hour type recording electrical input to the compressor.
Safety Features: Condenser high pressure switch and compressor thermal overload switch. Residual current circuit breaker and a combined double pole main switch and overload cut out. All electrical components connected to common earth conductor.
A: 600W 220-240 Volts, Single Phase 50 Hz (with earth /ground).
Line current up to 3.0A at 230v.
B: 600W 110-120 Volts, Single phase, 60Hz (with earth /ground).
Line current up to 6.0A at 110V.
Cold water, continuous supply. 180 litres/Hour at 15 m head minimum.