non-hcfc refrigerant (Non-HCFC refrigerant )

Non-HCFC refrigerant mixture for an ultra-low temperature refrigeration system

Patent - US6631625B1, US Grant

BACKGROUND OF THE INVENTION

In refrigeration systems, a refrigerant gas is compressed in a compressor unit. Heat generated by the compression is then removed generally by passing the compressed gas through a water or air cooled condenser coil. The cooled, condensed gas is then allowed to rapidly expand into an evaporating coil where the gas becomes much colder, thus cooling the coil and the inside of the refrigeration system box around which the coil is placed.

Ultra-low and cryogenic temperatures ranging from −95° C. to −150° C. have been achieved in refrigeration systems using a single circuit vapor compressor. These systems typically use a single compressor to pump a mixture of four or five chlorofluorocarbon (CFC) containing refrigerants to reach an evaporative temperature of as low as −160° C.

Environmental concern over the depletion of the ozonosphere has increased pressure on refrigerator manufacturers to substantially reduce the level of CFC-containing refrigerants used within their systems. Although non-CFC refrigerant mixtures have been developed, it has been discovered that most of these refrigerant mixtures cannot simply be substituted for CFC-containing refrigerants in currently available refrigeration systems due to the different thermodynamic properties of the refrigerants.

The present inventor has discovered that using non-CFC refrigerants in conventional ultra-low and cryogenic temperature systems cause an imbalanced flow of the refrigerants in the refrigeration circuit, which reduces the cooling capability of the refrigerants to the compressor. Such low levels of compressor cooling can cause a system to fail due to compressor overheating.

Furthermore, given that HCFC refrigerants do contain chlorine, that over time can affect the ozone layer as well as CFC refrigerants, the present inventor has developed a novel autocascade ultra-low and cryogenic temperature refrigeration system which is capable of operating with non-HCFC refrigerant mixtures. These non-HCFC refrigerant mixtures are non-toxic, chemically stable, commercially available and compatible with most of the standard refrigeration oils and compressor materials. Normally, one component of a non-CFC refrigerant mixture, i.e., hydrochlorofluorocarbon (HCFC), is a regulated ozone depleting chemical. However, the present invention uses a non-HCFC refrigerant mixture which has no ozone depleting properties at all, i.e., the mixture is primarily composed of hydrofluorocarbon (HFC) refrigerants and hydrocarbons.

As shown in FIG. 7, an index called the Ozone Depletion Potential (ODP) has been adopted for regulatory purposes. The ODP of a compound is an estimate of the total ozone depletion due to 1 Kg of the compound divided by the total ozone depletion due to 1 Kg of CFC-11 refrigerant. Thus, the ODP shows relative effects of comparable emissions of the various compounds.

Unlike the CFC-containing refrigeration systems which do not cause overheating of the compressor, the present inventor has discovered that the substantially non-HCFC refrigeration systems must provide additional liquid return to the compressor in order to avoid overheating thereof and eventual failure of the system.

As such, the overall performance of the non-HCFC autocascade system is comparable to its counterpart of the CFC autocascade system. This is evidenced by the fact that both systems have similar pull down rates and compressor operating conditions at standard 90° F. ambient.

The present invention also provides many additional advantages which shall become apparent as described below.

SUMMARY OF THE INVENTION

The present invention overcomes the need for using CFC or HCFC refrigerant mixtures in a refrigeration system by utilizing refrigerants R14, R23, R50, R116, R134a, R152a, R170, R236fa, R236ea, R245fa, R245ca, RC318, R290, RR508a, R508b, R600, R600a, R740 and R 1150 in various 5, 6 and 7-component mixtures. To achieve desired properties, these refrigerants may be used in a “cocktail” mixture (e.g., R600a or R600; R290; R170 or R 1150; R50; and R740).

It is therefore a feature of the present invention to provide a non-HCFC ultra-low temperature refrigerant mixture that can safely be applied in the field as needed without the risks associated with CFC or HCFC ultra-low temperature refrigerants.

It is another feature of the present invention to provide a refrigeration heat exchanger section which is capable of circulating a substantially non-HCFC refrigerant mixture which comprises: a compressor means, an auxiliary condenser, a first condenser, a second condenser, a third condenser, a subcooler means and a liquid/gas separator, wherein the improvement is characterized by: a means for distributing a subcooled refrigerant liquid mixture from the liquid/gas separator to a first expansion means and a second expansion means for forming first and second expanded streams, respectively; and a first conduit means for returning the first expanded stream to the auxiliary condenser and the compressor; and a second conduit means for delivering the second expanded stream to the first condenser.

The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purposes of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent construction insofar as they do not depart from the spirit and scope of the present invention

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the single compressor refrigeration system according to the present invention.

FIG. 5 is a graph depicting the pull down rates of CFC refrigerants in a conventional autocascade system at 90° F. ambient.

FIG. 6 is a graph depicting the pull down rates of non-HCFC refrigerants in an autocascade system according to the present invention at 90° F. ambient.

Words

1. Condenser coil – змеевик конденсатора

2. Single circuit vapor compressor - одноконтурный паровой компрессор

3. Ozone depleting properties – озоноразрушающие свойства

4. Emission – излучение

5. Auxiliary – вспомогательный

6. Embodiment - воплощение