The components of the heat pump and its instrumentation are mounted on a gloss finish high quality ABS plastic panel.
The heat pump consists of a hermetic compressor, an efficient plate heat exchanger condenser and evaporator, a liquid receiver, a thermostatically controlled expansion valve.
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 plate 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 water in the evaporator. 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 the water source evaporator. However, a limited variation is possible, by variation of the evaporator water flow rate.
Variable area flowmeters on 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.
Refrigerant: R134a (HFC134a)
Panel: High quality ABS plastic panel on which the following components are mounted.
Compressor: Fully hermetic single cylinder reciprocating type. Displacement 18.5cm3 rev-1
Condenser: Refrigerant to water insulated plate heat exchanger.
Liquid Receiver: With valves. Contains entire refrigerant charge if required.
Evaporator: Water to refrigerant efficient plate heat exchanger.
Digital Thermometer: Resolution 0.1ºC, with switch to select from six thermocouples.
Flow Meters (3): Variable area type – to indicate R134a and H2O flow rates (2).
Pressure Gauges (2): To indicate R134a pressures in evaporator and condenser.
A: 800W 220-240 Volts, Single Phase 50 Hz (with earth /ground). Line current up to 3.0A at 230v.
B: 800W 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.