Immiscible Refrigeration System

This system is a combination of mechanical refrigeration with the supplement of absorption cycle to unload the compression requirement of the conventional mechanical refrigeration system. Two type of refrigerant is utilized in the system. These refrigerant should meet the important characteristic with the least miscibility at the required refrigerant temperature. Propane and ammonia are one of the example to meet the requirement. When there are two immiscible refrigerant coexist in the chiller, the pressure of the chiller is almost equivalent to the summation of the vapor pressure of the individual refrigerant. For example at 32°F, the vapor pressure of propane is 68.72 psia and ammonia is 62.47. There is experimental data published by Noda et al. Indicated that at the present of two immiscible refrigerant the vapor pressure over the mixture is 129 psia which is almost double than the vapor pressure of either pure refrigerant. That means the suction pressure at the refrigerant compressor is almost double than the individual pure refrigerant. If one of the refrigerant can be take out by absorbent at suction then the flow to the compressor can also be greatly reduced. Ammonia is known very soluble in water, thus ammonia can be absorbed by water after it is vaporized in the chiller. Only propane is left for compression. The compression power is greatly reduced by higher suction pressure and reduced refrigerant flow. The ammonia rich water solution can be regenerated at higher pressure with waste heat. Nearly pure ammonia can be reproduced at the top of the regenerator and can recycle with the liquid propane and be used again in the chiller.

• Conventional Approach – higher efficiency by converting waste heat to  inlet-air cooling via absorption refrigeration cycle.
• Limitation - Absorption cycle cannot take advantage of higher temperatures available in exhaust gas (Low COP)
• Combines Absorption cycle with Rankine cycle
• Utilizes two immiscible refrigerants (50% propane and 50% ammonia  @ 32 °F)

PT = x1P1vp + x2P2vp (miscible) = 65.5 psia

PT = P1vp + P2vp (immiscible) = 129 psia

•  INEEL – doing bench scale demonstration plant to validate concept

PERFORMANCE COMPARISON OF CONVENTIONAL VS. IMMISCIBLE REFRIGERATION GE FR 9E TURBINE POWER = 146,500 HP @ 90 °F; = 171,000 HP @ 50 °F