Geothermal Refrigerant Flow Controls
Direct GeoExchange is today’s most effective method of harvesting the earth’s renewable energy for the purpose of providing domestic hot water and heating/cooling for buildings. Highly versatile, EarthLinked’s refrigerant flow controls have successfully operated commercial refrigeration systems, air source heat pumps from 3-50kWth capacity, a variety of GeoExchange systems produced by five manufacturers, closed-loop units of three manufacturers, multi-compressor units, and radiant hydronic heating systems. These unique flow controls also make possible the inclusion of de-superheating or integrated water heating on any heat pump system without the need for electronic controls.
Until the development of EarthLinked’s Refrigerant Flow Controls, no simple controls or metering devices existed that could deliver refrigerant in the condition appropriate to each component throughout the entire operating cycle and continually maintain stable refrigerant conditions.
Special refrigerant flow controls were necessary to manage the refrigerant in the long evaporator-condenser which is buried in direct contact with the heat source. Direct Energy’s refrigerant management system serves this need and provides multiple additional advantages.
Geothermal Heating explained
Geothermal Cooling explained
Refrigerant Management Objectives
- Stable refrigerant management in long evaporator/condenser under all loading conditions.
- Continuously return lubricating oil to the compressor without any liquid refrigerant.
- Improved system efficiency, reliability and serviceability.
To operate at optimum efficiency, the three major components of all heat pumps require the refrigerant to be in a particular physical state appropriate to each component (the compressor, condenser and evaporator). The compressor needs a dry refrigerant vapour from the evaporator, containing little or no superheat at the compressor inlet. The condenser needs its refrigerant outlet pressure to be just sufficient to cause the refrigerant vapour to complete its condensing just before it reaches the condenser outlet. This provides high pressure vapour to the entire condenser for maximum condensing with no uncondensed vapour passing through the condenser and no liquid refrigerant “backed up” in the condenser (which produces subcooling).
In contrast, the evaporator needs liquid refrigerant at its inlet. The liquid should then complete its evaporation just as it reaches the evaporator outlet. This is the optimum “flooded” evaporator condition which produces maximum system efficiency when no portion of the evaporator is wasted in producing superheat. Any unevaporated refrigerant which passes through or out of the evaporator should not reach the compressor.
Conventional controls include thermostatic expansion valves (TXVs), electronic expansion valves (EXVs), automatic expansion valves (AXVs), fixed orifices, capillary tubes, and accumulators. No combination of these can assure simple, stable operation of a Direct GeoExchange system or achieve all the following conditions which EarthLinked’s controls maintain in any standard air conditioning system, including:
- A fully condensing condenser (minimal subcooling).
- A continuously flooded evaporator (no superheat).
- Dry vapor with no superheat at the compressor inlet.
- A simple, easy method of determining when the system is properly charged.
The inherent simplicity and adaptability of EarthLinked controls has been proven since 1984. These controls have increased the efficiency of a variety of systems produced by 16 different manufacturers, including air source heat pumps (15% efficiency gain), air conditioners; closed loop GeoExchangers (loop length can be reduced by approximately one-fourth because of system efficiency introduced by the ACC and LFC); hundreds of other Direct GeoExchange systems (including inoperable and inefficient units previously produced by others); Direct GeoExchange water heaters; and radiant hydronic systems which also produce domestic hot water.
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