Heat Pump & DX Cycle
Heat Pumps are a major contributor to Net Zero target, as it uses natural energy in the ambient air, ground & water, by using electricity4
• 1 What is a Heat Pump?
(Also known as Reverse (heating or cooling) DX Cycle, or a Vapor Compression Refrigeration System (VCRS).)
A Heat Pump is a highly efficent3 sealed DX (Direct Expansion) Cycle2 that comprises of a Compressor, an Evaporator a Condenser and an Expansion Device. It uses refrigerants5 as a circulating media to transfer energy (heat) from outside to inside (heating) or from inside to outside (cooling).
DX Cycle - Heating
DX Cycle - Cooling
• 2 What is a refrigerant DX (Direct Expansion) Cycle?
The DX cycle utilising refrigerant is used in all types of:
A DX cycle utilising refrigerant can be:
Configeration of Systems:
Did you know? In a DX cycle Heat Pump, Heating Capacity is more tha Cooling Capacity?
• 3 Types of systems
- Air to Air systems (One to One) & (Multi Splt) (most common, efficient & cost effective), Splits, Multi Splits, VRF, Roof Top)
- Air to Water, Domestic Heat Pumps, Air cooled chillers.
- Water to Water, Water cooled chiller/heat pump
- Ground to Air, Splits, VRF (reverse cycle Heating & Cooling)
- Ground to Water. Ground Source Heat Pumps.
• 4 DX cycle Energy Efficency Advantages due to Refrigerants
Efficiency of DX cycle = Energy transferred / Energy used by the process
The efficiency of cooling EER- (Energy Efficiency Ratio) cycle or heating cycle COP - (Coefficient Of Performance) can range anything between 250% or (2.5/1) ratio to 500% or (5/1) ratio (that is for every energy unit, [say1 kW] electricity consumed, up to 5 kW can be absorbed from inside (unwanted heat) to be rejected outside - (cooling), or absorbed from outside (air, water or ground) and transferred to inside (heating) to heat a) occupied spaces or b) domestic hot water. These efficiencies (EER & COP) are based on a fixed ambient conditions (called Nominal Capacities).
There are seasonal efficiencies (SEER & SCOP) which are more accurately relates variable ambient conditions and hours of operation.
For example in the UK (considered as mild weather), the SEER can reach 700% or (7/1) ratio while SCOP can be 800% or (8/1) ratio, compared to 85% or (0.85/1) ratio for a gas or oil boilers. Hence a heat pump is a "major contributor to Net Zero target"
The Indoor units can be a Wall, Floor, Ceiling or Ducted fan coils or a refrigerant to water heat exchanger (to provide domestic hot water) or medium temperature heating water for under floor heating, radiators of water fan coils. The interconnecting refrigeration pipe work would require specialist approved refrigeration engineers and materials.
Advantages of DX cycle Heat Pump heating/hotwater systems over fossile fuel systen (Natural Gas or Oil or Coal):
a) No extra safety systems - Gas detectors, fire/smoke alarm, extra ventilation (provided the refrigerant is A1 class non-flammable),
b) No chimneys,hence no local pollution
c) No Natural Gas supply,
d) No fuel storage (oil),
e) Less builder’s work,
f) Normal electrical supplies (domestic).
g) No network (gas) installation, maintenance, repair or fire safety
h) No supply (oil, gas in rural areas or coal) logistics & costs
i) No import or supply security risks associated with imports of fossil fuels.
Location of outdoor units can be as far as 100 meters away from indoor units in an Air to Air split systems.