Energy requirements refrigeration

The energy required to boil the liquid is supplied by a freon-type heat pump. This unit provides the heat required for evaporation and the refrigeration for condensation. 

Calculations of the energy requirement for the process, if it is carried out in a continuous manner, indicate that the efficiency would only be about one tenth that of the familiar ammonia refrigeration cycle, unless the energy released when the melted ice is decompressed could be efficiently recovered. Achievement of the latter in actual practice requires invention of some practical mechanical arrangements. 

In this paper idealized conversion processes utilizing reversible refrigeration machines are analyzed with respect to energy requirements. First, energy equations are established for a completely reversible process. Several irreversible modifications of this process are then analyzed. 

Figure 2. Refrigeration energy requirements. Influence of driving forces...

In the second plot, the energy required by the primary compressor is shown to be sensitive to the pressure in the evaporator-freezer and condenser-melter. Because both the evaporation and condensation are by direct contact of the refrigerant with water or ice, the opportunity exists for realistic achievement of a low over-all driving force. Experimentally, the evaporation has been found to occur so rapidly that a rate measurement has not been practical. The melting of the ice is more of a problem because the condensate film is a heat transfer barrier. However, the barrier is a fluid and not a stationary wall as in a distillation unit, wherein steam is condensed against water or boiling water. 

Low-temperature fractionation is the preferred method of hydrocarbon separation. Cascade refrigeration is used with propylene and ethylene, the commonly encountered refrigerants. Refrigeration compressors are large and have energy requirements essentially similar to those of the initial product gas compressors. 

Note in Table II that the heat pump alternative represents about a 30% saving on available energy input compared to the refrigerated process, and that both represent a very large reduction in the available energy requirement of the original process. The heat pump process does indeed save the losses at both condensers, but has some compensating losses elsewhere. 

Storage Facilities (NPFS, PFS, FRS, PPFS and PCJS) posses a maximum storage capacity and an associated cost related to the energy required to refrigerate the fruit. There exist significant transportation within the system. Fruit is transported by trucks between the different nodes of the chain. Transportation costs depend on the distances between the facilities and the type of transportation refrigerated or not. 

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