Cascading Plant

Abstract

An integrated refrigeration and air conditioning plant working in a cascade cycle with two different refrigerants for the low and high temperature circuits. The low temperature segment works with an ozone friendly synthetic refrigerant with a minimal amount of refrigerant charge, while the upper stage operates with another ozone friendly refrigerant with much lesser global warming potential than the one in the low stage. The upper and/or medium temperature circuit also services the air conditioning needs of the environment where the refrigerated equipment is located, such as the shop floor of a supermarket or a laboratory housing the cabinets that keep refrigerators.

Description

FIELD OF INVENTION[0001]The invention relates to refrigeration and air conditioning systems, including such systems when used in a supermarket setting. It specifically addresses the lacuna in integrating seemingly different, but intricately related, domains of cooling requirements at various temperature levels. The objectives are sought to be achieved in a manner that is environmentally friendly, energy efficient and operated in an intelligent way that marries the thermodynamic fluid dynamic interface at two different refrigerants.BACKGROUND TO THE PRESENT INVENTION[0002]In this document the numbering of refrigerants is in accordance with the protocol recommended by the learned societies relevant to the profession of refrigeration and air conditioning, such as American Society of Refrigeration, Heating and Air conditioning Engineers (ASHRAE), International Institute of Refrigeration (IIR), Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH), Japan Society of ...

AI Technical Summary

Benefits of technology

[0032]Even more preferably, the fraction of latent heat available at the evaporator is substantially increased compared to current practice because of a reduction in the condensing temperature and pressure. A consequent benefit is a reduction in mass flow rate of the refrigerant in the lower stage of the cascade plant which inherently necessitates a smaller compressor. The net effect is that not only the compressor size is smaller, but also it works more efficiently resulting substantial reduction in indirect greenhouse gas emissions due to electricity consumption.

[0033]According to another preferred aspect, since the condensing temperature may be lowered, the maximum operating pressure in the lower stage of cascade cycle is also reduced. This causes smaller leakages of refrigerant because the leakage is proportional to the square root of the gauge pressure.

Problems solved by technology

The current Australian refrigeration and air conditioning trade practices are unable to reduce the leakages below 10% of initial charge per year.

While this may not appear much, the amount of supermarkets Australia wide is 1500 and therefore the collective damage caused by their leveraging emissions is high.

The current practice is to use a separate set of compressors that provide low temperature refrigeration which operate between evaporating and condensing temperatures of −30 to 45° C., which is a very large thermal boost that is fraught with very poor volumetric and isentropic efficiencies of the compressors, very high discharge temperatures that led to rapid degradation of the lubricating oil.

Further, because of large differential between the suction and discharge pressures, the leakage losses are large.Because of large thermal boosts, the available latent heat at the evaporator reduces to almost 50%.

Further, independent controls do not allow fine tuning of matching interfaces resulting in high energy consumption for refrigeration.

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