Pumps – With muffler acting on pump fluid
Patent
1998-11-25
2000-12-05
Freay, Charles G.
Pumps
With muffler acting on pump fluid
417902, 181403, F04B 3900
Patent
active
061558001
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention refers to a suction arrangement for a reciprocating hermetic compressor of the type having low pressure within its hermetic shell.
BACKGROUND OF THE INVENTION
Reciprocating hermetic compressors are generally provided with suction acoustic dampening systems (acoustic filters), which are disposed inside the shell with the function to attenuate the noise generated during the suction of the refrigerant fluid. Such components, however, cause losses both in the refrigerating capacity and in the efficiency of the compressor, resulting from gas overheating and flow restriction. The manufacture of said filters from plastic materials have meant a significant advance regarding their optimization, although a considerable amount of the compressor losses is still due to this component.
In reciprocating compressors, the movement of the piston and the use of suction and discharge valves, which open only during a fraction of the total cycle, produce a pulsing gas flow both in the suction and in the discharge lines. Such flow is one of the causes of noise, which may be transmitted to the environment in two forms: by the excitement of the ressonance frequencies of the inner cavity of the compressor, or of other component of the mechanical assembly, or by the excitement of the ressonance frequencies of the piping of the refrigerant system, i.e., evaporator, condenser and connecting tubes of these components of the compressor refrigerating system. In the first case, the noise is transmitted to the shell, which irradiates it to the external environment.
In order to attenuate the noise generated by the pulsing flow, acoustic dampening systems (acoustic filters) have been used. These systems may be classified as dissipative and reactive systems. The dissipative dampening systems absorb sound energy, but create an undesirable pressure loss. On the other hand, the reactive mufflers tend to reflect part of the sound energy, thereby reducing pressure loss. The dissipative mufflers are more used in discharge dampening systems, where the pulsation is high. The reactive systems are preferred for the suction, since they present less pressure loss. Said pressure loss in the acoustic filters is one of the causes that reduce the efficiency of the compressors, mainly in the suction case, which is more sensible to the pressure loss effects.
Other cause that reduces the efficiency of the compressors, when usual acoustic mufflers are employed, is the overheating of the suctioned gas. During the time interval between the entrance of the gas into the compressor and its admission to the compressor cylinder, the gas temperature is increased, due to heat transfer from the several hot sources existing inside the compressor. The temperature increase causes an increase in the specific volume and consequently a reduction in the refrigerant mass flow. Since the refrigerating capacity of the compressor is directly proportional to the mass flow, reducing said flow results in efficiency loss.
Reducing these negative effects has been achieved with the evolution in the acoustic filter designs. In prior constructions, the gas coming from the suction line and discharged into the shell passes through the main hot sources inside the compressor, before reaching the filter and being drawn towards the cylinder inside (indirect suction). This gas circulation should promote the cooling of the motor. Because of this and because the filters were usually metallic, the efficiency of the compressor was impaired due to gas overheating.
The requirements for more efficient compressors have led to the development of acoustic dampening systems with more efficient conceptions. The gas, rather than passing through all heated parts inside the compressor, is drawn directly to the inside of the suction filter (U.S. Pat. No. 1,591,239, U.S. Pat. No. 4,242,056). Other technique uses, in the suction piping inside the compressor, nozzles or flared tubes (U.S. Pat. No. 4,486,153), which allow the flow to be directed between the inlet tube
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Patent Abstracts of Japan vol. 013, No. 582 (M-911), Dec. 21, 1989 and JP 01244180, Sep. 28, 1989.
International Preliminary Examination Report received in respect of International Application PCT/BR97/00017 dated Jul. 22, 1998.
Fagotti Fabian
Lilie Dietmar Erich Bernhard
Todescat Marcio Luiz
Empresa Brasileira de Compressores S/A-Embraco
Evora Robert Z.
Freay Charles G.
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