Refrigeration – Refrigeration producer – With lubricant handling means
Reexamination Certificate
2001-03-27
2002-10-22
Doerrler, William C. (Department: 3744)
Refrigeration
Refrigeration producer
With lubricant handling means
C062S503000, C062S513000
Reexamination Certificate
active
06467300
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention is directed toward improved performance of stationary and mobile air conditioning systems and other similar cooling systems by reducing the amount of saturated heat during the gas-to-liquid phase change in the condenser. To accomplish this objective, an intercooler device is placed between the condenser and evaporator, which enables more complete refrigerant condensation by improving the efficiency of the phase change. Such liquid refrigerant delivered to the evaporator, typically after passing through an expansion valve, arrives further below the critical temperature than before, with less saturated heat, and is thereby enabled to absorb more new heat during the evaporation phase than would be possible without the device. The intercooler is suitable for mobile and stationary air conditioning and refrigeration applications because of its ability to capture and recycle the otherwise wasted heat absorption capacity of the cold return gas. The operational improvement that is most immediately noticed by the user of the invention is the faster cool-down time and lower duct temperature achieved on a hot day compared with systems that are not fitted with the disclosed device. The differences are easier to identify when there is a high ambient heat load because systems not equipped with the device are not able to keep up in such hot weather. Systems with the device achieve faster cool-down times and lower temperatures, therefore greater comfort levels. Government, military, public and private sectors of the economy will benefit from the use of this invention.
In high heat and humidity areas, such as along the U.S. Gulf Coast, where the summer is long and intense, air conditioners and refrigeration systems frequently cannot keep up with the demands placed upon them. Hot and humid climates subject an air conditioning or refrigeration system to greater heat loads than such systems found in cooler climates. For example, in cities along the Gulf of Mexico, an air conditioner must perform efficiently during six to eight months of hot weather during the year, often having many weeks when daily temperatures range between 90-103° F.
Aftermarket enhancements are frequently needed to overcome built-in engineering deficiencies in factory systems. Manufacturers frequently do not produce systems, which are able to function well in hot climates, and many condensers do a poor job of giving up heat because of their inefficient designs and/or poor airflow through them. For example, the lack of airflow produced by fan clutches is a common reason for the inability of condensers to give up heat. Automobile engine fan clutches have notoriously poor engineering, and frequently won't do an adequate job in high heat load climates. Technicians are often not taught how to properly test fan clutches, thus high head pressures are ignored and continue to reduce condenser efficiency affecting the entire system like a low grade fever, e.g., the compressor works harder and fails prematurely, the engine consumes more fuel, etc. The problem of condenser fan inefficiency is not as prevalent on commercial heating, ventilation and air conditioning (HVAC) systems because they are electrically driven, and are generally not of the slip type viscous engagement design. However, by lowering the saturated heat levels and higher head pressures, the present invention can provide lower fuel costs, lower temperatures, and faster cool-down on both mobile and stationary applications. The second issue of condenser efficiencies can be summarized by stating that the new generation of high efficiency condensers has become a necessity because of the more problematic R134a, which is now the refrigerant of choice by manufacturers.
To obtain a better understanding of why systems not equipped with the present invention do not perform up to their potential, two basic principles of the a/c-refrigeration system heat transfer process must be understood. Technically, air conditioning and refrigeration systems do not make cold air; they remove heat (evaporation cycle); then they give up heat (condensation cycle). After the evaporator picks up heat from the air inside the compartment to be cooled, the condenser has to return that heat (usually back to the atmosphere). If the condenser cannot effectively give up the heat absorbed by the evaporator, then the heat soaked liquid leaving the condenser reenters the evaporator unable to accept as much new heat as it should. The result is occupant discomfort, longer cool-down time and unacceptably high head pressures. Vehicle a/c systems are not able to remove enough heat from the passenger compartment to provide a sufficient comfort level when driving on short trips, or only provide a marginal level of cooling on longer trips for passengers in the rear of the vehicle. In the case of homes and commercial buildings, the same inefficiencies, high pressures, and creature discomfort problems occur. Systems not equipped with the invention exhibit greater high side pressures, which cause the compressor to work harder, reducing its life and increasing fuel consumption and operating costs. Condensers are unable to fully condense that overheated liquid before feeding it to the evaporator. Condenser manufacturers now have the burden of providing designs that are 25-40% more efficient than were required with the more efficient, but almost depleted supply of, R12 refrigerant. Condensers must now be designed to compensate for the inefficiency of the new R134a, and other refrigerants having similar characteristics such as higher critical temperatures and working pressures than R12. Regardless of which refrigerant is used, because evaporators are rendered less efficient by being fed heat-saturated liquid, they lack the ability to effectively absorb new heat. Systems equipped with a refrigerated intercooler provide better heat dissipation during the condensation cycle so that better heat acceptance can be achieved during the evaporation cycle.
The term critical temperature is defined as the temperature above which a gas cannot be liquefied, regardless of how much pressure is applied. This is important because refrigerants resist staying liquid when acted upon by heat. Heat is absorbed into an a/c or refrigeration system, not just from air passing across the evaporator, but also from the very hot under-hood engine temperatures. One such example is the problem of “heat soak” from the engine radiator to the a/c condenser due to their near proximity. For the expansion valve to do its job effectively, it needs to meter a fully condensed, non heat-saturated liquid refrigerant into the evaporator.
The solution to the problem of excessive saturated heat within the condenser and its downstream liquid line is to reduce that heat load well below the critical temperature of prevailing refrigerants used in modern air conditioning and refrigeration systems. This is achieved by precooling the liquid going to the evaporator, making all refrigerant in the closed system cooler.
The theory of why better performance is achieved when using this invention is confirmed by field testing. After observing improved cool-down time, and lower duct temperatures on systems equipped with the apparatus, it has been concluded that the heat absorption capacity of evaporators, and the heat rejection capacity of condensers are underutilized. By intercooling the liquid stream between condenser outlet and evaporator inlet, the following results occurred: (a) Maximum cooling was achieved prior to reaching the factory specified charge level, and adding more refrigerant resulted in an overcharge with diminished cooling. (b) Faster cool-down time occurred. (c) Lower head pressures resulted because the cooler and lesser volume of refrigerant being compressed by the compressor resulted in more efficient condensation, creating greater expansion space in the condense
Keeling Kenneth A.
Keeling & Hudson LLC
Noble, III John O.
LandOfFree
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