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When 80°C waste heat enters the adsorption chiller, it typically generates chilled water at 7°C–12°C. This water is then circulated through terminal units—such as Fan Coil Units (FCUs) or Air Handling Units (AHUs)—to deliver cool air at 16°C–20°C.
Temperature transitions across system stages:
• Waste heat source: 80°C hot water (entering the adsorption heat exchanger).
• Chilled water output: 7°C–12°C (chilled water produced via vacuum evaporation within the adsorption unit).
• Final air supply temperature: 16°C–18°C (air temperature discharged from the fan coil unit).
Key performance metrics:
• Coefficient of Performance (COP): Driven by 80°C hot water, the adsorption system’s COP is approximately 0.55–0.65 (meaning every 10 kW of waste heat input yields roughly 5.5–6.5 kW of cooling energy).
• Cooling water requirements: The adsorption process requires a cooling tower for heat rejection; the cooling water inlet temperature generally needs to be maintained at approximately 30°C–32°C for optimal cooling performance.
Coating zeolite powder onto the external fins of a FIN-JET Matrix-X four-row heat exchanger, enclosing it in a transparent casing, and filling it with ethanol as the refrigerant creates a typical zeolite/ethanol adsorption heat pump/cooling module.
Key engineering design and technical points:
• Zeolite coating process:
o Heat conduction optimization: Leveraging the high thermal conductivity of copper fins, the coating layer must be extremely thin and uniform (typically achieved through direct growth via hydrothermal synthesis or application using a highly thermally conductive binder) to minimize thermal resistance caused by the zeolite's inherently poor thermal conductivity. o Maximized specific surface area: Combines a microstructure featuring over 300 copper fins with the porous structure of zeolite to significantly enhance the adsorption and desorption rates of ethanol vapor.
• Advantages of the Ethanol Working Pair
o Low-pressure evaporation capability: Ethanol possesses excellent latent heat of vaporization under vacuum (approx. 846 kJ/kg) and a low freezing point (-114°C), allowing the system to operate in sub-zero environments without the risk of freezing.
o High compatibility: Zeolites (particularly molecular sieves with specific pore sizes like 13X or SAPO types) exhibit a strong affinity for ethanol molecules, making them suitable for systems driven by low-to-medium-grade waste heat (70°C–90°C).
• Functions of the Transparent Shell (Sealed Chamber)
o Airtightness and vacuum maintenance: The adsorption system operates under negative pressure (vacuum); the transparent shell must offer high pressure resistance and resistance to ethanol corrosion (e.g., high-strength polycarbonate or acrylic).
o Flow field and process visualization: Allows for direct observation of ethanol evaporation, condensation, and adsorption dynamics between the fins, offering significant value for experimental testing and demonstration.
Operational Cycle Mechanism
1. Desorption Phase (Thermal Regeneration): Waste hot water (80°C) flows through the copper tubes, heating the zeolite on the external fins; this causes the zeolite to release the adsorbed ethanol vapor, which then rises to the top of the chamber to condense.
2. Adsorption Phase (Cooling Output): After cooling water removes heat, the zeolite cools down and strongly adsorbs the ethanol vapor within the chamber; this drives the rapid evaporation of liquid ethanol (absorbing heat in the process) to produce chilled water output. |
