Views: 0 Author: Site Editor Publish Time: 2026-05-22 Origin: Site
CO₂ Side Operating Conditions: Supercritical high-pressure fluid (pressure 7.4–16 MPa, temperature 80–180℃), with no condensation phase change throughout the process; sensible heat is carried away solely through air convection.
Core Function: Cools the high-temperature, high-pressure supercritical CO₂ discharged from the compressor to near ambient temperature (30–45℃), providing sufficient temperature drop for subsequent throttling expansion. High-pressure CO₂ flows through the tube side; finned side cooling is achieved through forced convection by an axial fan.
Heat Exchanger Tube Material and Specifications:
316L stainless steel tubes (conventional transcritical systems);
2205 duplex stainless steel (high humidity/sulfur-containing, coastal corrosive environments);
Tub diameter is typically 12–25 mm, wall thickness 2–4 mm, pressure rating ≥16 MPa, avoiding high-pressure impact and corrosion from supercritical CO₂.
Fin Structure: Utilizes high-efficiency corrugated aluminum fins (hydrophilic aluminum foil optional for improved heat transfer in wet conditions), with a fin spacing of 2.5–4 mm, balancing heat transfer efficiency and dust resistance. Fins are mechanically expanded and then brazed to the heat exchange tubes, preventing fin detachment under high pressure.
Shell and Pressure Bearing Design: The shell is constructed of thickened galvanized steel/stainless steel. The CO₂ side manifold and tube sheet are made of high-pressure forgings. 100% of welds undergo non-destructive testing (UT/RT). A hydrostatic test at 1.5 times the design pressure is performed before shipment (e.g., 16 MPa design pressure, 24 MPa test pressure) to eliminate the risk of high-pressure leakage.
Large-diameter axial flow fans are designed to provide high-volume, low-static-pressure airflow, suitable for the large temperature drop requirements of supercritical CO₂ cooling. These fans typically employ variable frequency drive (VFD) control, automatically adjusting their speed based on the CO₂ inlet and outlet temperatures: operating at full load when ambient temperatures are high and reducing speed to save energy at low temperatures, while also preventing excessive cooling in winter that could cause CO₂ to enter the subcritical region (leading to phase change pressure fluctuations).
Application Scenarios
Commercial Cold Chain Refrigeration: Transcritical CO₂ refrigeration systems for supermarket freezers and cold storage facilities, replacing R404A/R134a systems; environmentally friendly (GWP=1) and highly energy efficient.
High-Temperature Heat Pump Systems: Heating in northern regions and industrial hot water production; supercritical CO₂ coolers can recover heat, achieving high-temperature water output of 65–90℃.
Industrial Waste Heat Recovery: CO₂ transcritical cycles driven by waste heat from generator sets/engine exhaust; high-pressure air coolers are responsible for cooling and releasing heat from the supercritical fluid.
Marine/Vehicle CO₂ Systems: Replacing traditional refrigerants; suitable for high salt spray and bumpy operating conditions; requires higher pressure resistance and vibration resistance from the equipment.
