In geothermal installations, which configuration exchanges heat with the ground using the refrigerant directly, without antifreeze?

In geothermal installations, which configuration exchanges heat with the ground using the refrigerant directly, without antifreeze?

• A. DX system
• B. Closed-loop system
• C. Open-loop system
• D. Brine-loop system

Answer: (A)

Direct Exchange is tested here. In this setup the earth heat exchanger actually carries the refrigerant itself, not a water or antifreeze solution. Because the refrigerant is the medium that moves heat between the ground and the heat pump, there’s no secondary fluid in the loop, so antifreeze isn’t used in the ground loop. This direct contact with the soil can improve heat transfer efficiency and simplify the loop, since you’re only dealing with the refrigerant and the borehole. If you compare it to other configurations, those use a separate heat-transfer fluid in buried pipes and often rely on antifreeze to prevent freezing. A closed-loop system circulates a water or water–glycol mix in pipes, and an open-loop system uses groundwater directly with a separate circuit for the refrigerant. A brine-loop specifically uses an antifreeze solution in the loop. All of these involve a secondary fluid in the ground, which is why they’re different from direct exchange.

Direct Exchange is tested here. In this setup the earth heat exchanger actually carries the refrigerant itself, not a water or antifreeze solution. Because the refrigerant is the medium that moves heat between the ground and the heat pump, there’s no secondary fluid in the loop, so antifreeze isn’t used in the ground loop. This direct contact with the soil can improve heat transfer efficiency and simplify the loop, since you’re only dealing with the refrigerant and the borehole.

If you compare it to other configurations, those use a separate heat-transfer fluid in buried pipes and often rely on antifreeze to prevent freezing. A closed-loop system circulates a water or water–glycol mix in pipes, and an open-loop system uses groundwater directly with a separate circuit for the refrigerant. A brine-loop specifically uses an antifreeze solution in the loop. All of these involve a secondary fluid in the ground, which is why they’re different from direct exchange.