Cold-gas refrigerator

Production of liquid carbon dioxide. The use of this cold gas refrigerator for recovering CO2 from a flue gas mixture as a liquid has been studied for a one ton per day capacity plant. The process is illustrated in Figure 9 and consists of the partial condensation of carbon dioxide gas from a flue gas mixture which has been compressed to a pressure of about 2000 psig. Studies have shown that liquid CO can be produced by this process for about 3 to 4 cents per pound for industrial applications. 

Since the coefficient of performance in Eq. (4.2) was developed for a Carnot refrigerator with two isothermal and two isentropic processes, it is unrealistic to use that expression for comparing cold-gas refrigerators in which the energy is absorbed at a varying temperature instead of at a constant... 

Example 4.1. An ideal cold-gas refrigerator utilizing nitrogen gas as the working fluid operates between an upper temperature of 300 K and a lower temperature that varies from a minimum of 120 K to a maximum of 150 K. If the pressure of the working fluid in the refrigerator is 1.01 MPa, determine the ideal coefficient of performance. 

Solution. The ideal coefficient of performance for a cold-gas refrigerator is given by Eq. (4.3) in which the actual thermodynamic property values for the working fluid are used. The necessary property values are obtained from the temperature-entropy diagram for nitrogen ... 

A cold-gas refrigeration system with helium as the working fluid operates between 0.101 and 1.52 MPa at 300 K. The 1.52-MPa gas is cooled to 20 K whereupon it is expanded to 0.101 MPa to provide the refrigeration effect. The refrigeration system utilizes an isothermal and reversible compressor, ideal heat exchanger, a reversible adiabatic expander, and an... 

If refrigeration is to be accomplishedat a temperature range where no suitable hquid exists to absorb heat by evaporation, then a cold gas must be available to absorb the heat. This is generally accomphshed by using a work-producing e)mansion engine. 

The total emissions from the system are not increased by the large quantities of cold gas, since a closed refrigerating cycle is maintained by vray of an externally ananged gas cooler and condenser (Fig. 2.37). The hot exhaust gas is made to pass through the cooler and is partly returned in the form of cold gas for pre-admission cooling into the pump. The pump... 

The refrigerator in Fig. 4a produces a cold gas, which absorbs heat from 4-5 and provides a method of refrigeration for obtaining temperatures other than those at the boiling points of cryogenic fluids. 

Example a b c d e f g Cold or refrigerated solid Solid Warm hot liquid Cold liquid Liquid Hot liquid Hot or warm compressed gas or vapor over hot liquid Compressed liquefied gas MP > f < MP and f... 

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