What types of heat pumps are available?Heat Pumps are normally classified by their heat source and means of delivering the heat:
Air to Air : Heat pump where the collecting medium is air and the destination medium is also air. Generally, most commercial small split and packaged systems are direct air to air it has been used in air conditioning application.
Water to Water: A heat pump where the collecting medium (source) is either ground water or a glycol from solar collectors solution and the destination medium is also water or glycol. These systems are invariably indirect.
Air to Water: Air to water systems are most common used in India single packaged units. An outdoor unit collects heat from ambient air and delivers it to the conditioned space by means of water or glycol circulated through fan coils. This type of system uses a mixture of direct acting outdoor unit coupled with an indirect indoor section. Used in many applications such as in conjunction with fan coil units in commercial buildings, for heating swimming pools, and for providing domestic hot water, hotels, mane more and Space heating for offices.
Water to Air: Water source systems are used where a supply of ground water, ponds or lakes are available. These systems are invariably indirect and need careful filtration to remove particles from the water source before it enters the heat ex-changer. Can use wells or boreholes, but can also be configured as many units connected together on a common closed water loop to enable energy transfer from hot to cold points in a building.
Ground to Water: As above but utilized with under floor heating systems, medium temperature heat ex-changers or fan coil units. In addition to this products Scanair manufacturers many configurations like single package, split package, ductable, rooftop mounted, part of a centralized system, zone system, or stand alone models.
Heating only heat pump: Ground Source heat pump systems are often optimized specially to deliver heating only these units are often capable of delivering greater overall energy efficiencies than reversible units because the system is designed for a constant unvarying load above the freezing point of water at the evaporator section and can dispense with the defrost Cycle.
Compressor: The compressor is often referred to as the heart of the refrigeration or heat pump system. It serves two main purposes. The first is to circulate the refrigerant fluid through the circuit like a pump, the other is to compress and raise the pressure and temperature of the refrigerant vapour so that it can easily be condensed back into a liquid to resume the heat transfer process.
Reverse Cycle Heat Pump: A reverse cycle system is a refrigeration system that can, by means of a valve that reverses the flow of the refrigerant fluid, change the operation of the system from heating to cooling. Or to facilitate defrost.
Heat Ex-changer: A heat ex-changer is a device for the transfer of heat energy from one medium to another. It can take a variety of different forms the common in everyday use is a central heating heat ex-changers where hot water is circulated through pipes or plates and gives its heat up to the surrounding air.
Evaporator: In refrigeration systems the evaporator is the heat ex-changer where refrigerant fluid is evaporated it absorbs heat from the surrounding air or water, thereby reducing its temperature.
Defrost Cycle: Where reversible air source systems operate at low ambient temperatures, the evaporator in the outdoor unit may attract moisture from the air at low ambient temperatures that will freeze forming a coat of ice. This is a function of the natural humidity outdoors and is not abnormal. This coating of ice is removed periodically with an automatic defrost cycle. The frequency of the defrost cycle is controlled automatically by a combination of time and temperature of the external coil.
Condenser: In refrigeration systems the condenser is the heat ex-changer where Hot, compressed refrigerant gas is condensed to a liquid and further cooled to evaporator around the circuit.
Capillary Tubes: Any fluid flowing through an orifice will experience a drop in pressure. A capillary tube is a precisely measured length of a narrow tube with a predetermined internal diameter that produces the desired drop in pressure along its length.
Thermostatic Expansion Valve (TEV): An automatic mechanical valve that is self compensated for the pressure losses in the evaporator and controls the leaving super heat temperature of the refrigerant.
Electronic Expansion Valve (EEV): A valve that is driven by a small dc stepping motor operates in the same way as a TEV although the valve positioning is determined by a microprocessor EEVs are capable of more precise metering and are found mainly in fully automatic systems.
Refrigerant: The heat transfer fluid contained in a heat pump refrigeration circuit. Normally this is a chemical contained in a hermetically sealed circuit that has a low temperature boiling point refrigerants can be one of a number of man-made Fluorocarbons or a Hydrocarbon compound.
Ground Source Heat Pump: Heat pump installation that uses the earth as a heat sink to store heat or as a source of heat in the India temperature below ground at a 4 feets to 20 feet depth is stable within a small tolerance year round. Heat can be stored or obtained from shallow ground, about 50feet depth, or by deeper bore-holes where space is a consideration.
Inverter Drive or Variable Speed Drive (VSD): Refrigeration systems in air to air heat pumps are often subject to wide variations in capacity and demand. A VSD system uses electronic speed control to vary the speed of the compressor motor. The motor speed can be increased to compensate for low ambient temperature conditions when less heat is available to use or decreased during mild weather. VSD systems are capable of high energy efficiencies because they match the unit’s capabilities to demand also known as VRV (Variable Refrigerant Volume) and VRF (Variable Refrigerant Flow).
CoP: (Coefficient of Performance): Used as a ratio, CoP is an expression of the output of a machine in heating mode. The rated capacity divided by the rated total power input. In practice this is expressed as a single figure or sometimes as a percentage. For example, a system that is rated in heating at 6.5kW, with a rated power consumption of 1.8kW will have a CoP of 3.61 or 361%.
CoP = Heating Output (kW) / Total Energy consumed by the system, including fans, pumps and controls (kW)
Energy Efficiency Ratio (EER). The out put of a machine in cooling mode. The rated capacity is divided by the rated total power input. In practice this is expressed as a single figure or sometimes as a percentage.
EER = Cooling Output (kW) / Total Energy consumed by the system, including fans, pumps and controls (kW)
Kilowatt: The SI unit of power. It is used to specify the thermal performance of a Heat Pump as well as the power energy it consumes.
Kilowatt Hour (kWh): The standard unit of sale of electricity, it is the equivalent power consumed by a purely resistive load of 1000 Watts (1kW) for 1in hour. Your electricity supplier will specify the price in your supply contract.