Refrigeration – With means preventing or handling atmospheric condensate... – Means utilizing heat developed by refrigeration producer
Reexamination Certificate
2000-05-09
2001-11-20
Bennett, Henry (Department: 3744)
Refrigeration
With means preventing or handling atmospheric condensate...
Means utilizing heat developed by refrigeration producer
C062S276000, C062S118000
Reexamination Certificate
active
06318107
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to devices and methods for defrosting of the cold sides of the refrigeration units. The present invention relates more specifically to the structure and composition of a device to rapidly and controllably defrost the evaporators and other under freezing sides of the refrigeration or heat pumping units using waste energy rather than added energy.
2. Description of the Related Art
The frost deposit on the evaporators represents a natural and unwanted phenomenon. In refrigeration and deep freezing units during the cooling cycle time the evaporator reaches lower temperatures than the freezing point of water, (0° C.), so, the frost, that is deposed will lower the overall efficiency of the units due to the thermal resistance of the snow-like deposits. It is well known that the frost deposit cannot be avoided because the water vapors are always present in the air infiltrating the unit. Realistically it can be said that most of the time the evaporators are covered with some unwanted frost which directly increases the energy required to keep the temperature of the refrigeration unit within necessary limits.
There have been a number of attempts to create devices and methods for an intermittent defrost cycle. The most commonly used device is based on an electric resistance heater, which is placed nearby the evaporator. The heat produced is used to melt the frost and the resulting water is collected and guided out of the system. The undesirable characteristic of this method is the relatively long time necessary to defrost because of the poor heat transfer (free convection of the air) from the electrical resistor to the evaporator coils. The residual heat in the evaporator space after defrost will increase the input energy necessary to regain the temperature needed inside the refrigeration unit. Usually the signal for defrost cycle is received from a sensor mounted directly on the evaporator which can measure the temperature drop of the evaporator due to the frost deposit. The temperature drop is directly influenced by the thickness of the frost.
Other defrost devices replaced the well-known electrical resistor with an infrared heater. The resistor wire is encased in a quartz glass tube and its operating temperature is set at red-orange color. The infrared radiation is reflected by the walls of the evaporator space and when they reach the evaporator, the thermal effect will melt the frost. This kind of infrared generator is mostly used when the evaporator is placed horizontally and free air connection cannot be used properly. The disadvantage of this approach is due to poor absorption of the infrared radiation by the frost, which is white and therefore reflective. The time necessary for defrost will thus be increased and the residual heat within the evaporator space is increased.
Another method for defrosting is the “reversed cycle” technique. Mostly used for larger units, the idea is based on in reversing the circulation of the refrigerant fluid inside the refrigeration system. In this way the evaporator will become the condenser and will receive hot, pressurized refrigerant from the compressor. The heat dissipated by the pressurized refrigerant is used to melt the frost. The “reversed cycle” or defrost cycle is achieved by solenoid valves that reverse the usual circulation of the refrigerant The valves are activated by the defrost sensor, as it was previously mentioned. The disadvantages of such a system are obvious: more moving parts within pressurized pipes should decrease the reliability, and the thickness of the evaporator walls must be increased to comply with the pressurized side requirements. As a result the thermal resistance of the evaporator will increase and the thermal transfer between the refrigerant and the air will decrease; so, the coefficient of performance (C.O.P) of the system will be lower than that of a classic unit.
The above existing devices and methods for defrost were developed in order to increase the efficiency of the refrigeration units. Energy savings represent a stringent requirement for all fields; global warning and the related aspects represent a global concern. High-energy efficiency appliances are required to be developed as part of the energy saving effort. Refrigeration systems of all kind represent one of the most important energy consumers.
SUMMARY OF THE INVENTION
It is desirable to have devices and methods for refrigeration defrost that consume as little energy as possible, and use as few moving parts as possible. It is desirable that the energy required could be applied directly on the evaporator pipes in order to avoid residual heat inside the evaporator space. It is desirable that the devices can be easily adapted to the existing designs, for any kind of refrigeration unit: all sizes of freezer-refrigerators, food cabinets, fresh food isle, large walk-in warehouses, etc.
One primary element of the devices and methods of the present invention is the preferred use of thermal energy stored in a liquid, which by forced convection will raise the temperature of the evaporator and will melt the frost during defrost cycle. The liquid does not reach the high temperature of a resistance element. For this purpose a designated circuit of liquid should be used.
The second-element of the devices and methods of the present invention refers to the preferred design, materials and construction of the warm liquid circuit in order to optimize the overall efficiency of the refrigeration system equipped with the new proposed defrost device.
In general, the better efficiency of the new concept developed by the present invention is the difference between the quantity of thermal energy generated inside the refrigeration units for defrost on existing designs and the energy needed only to circulate (forced convection) the warm fluid from the outside reservoir, in order to dissipate its thermal energy on the evaporator coil (the intend of the present invention).
The thermal energy of the fluid is acquired the heat dissipated by the condenser. In both cases the thermal energy used for defrosting the evaporator is a “free of charge energy”. The basic intent of the invention is to implement the new devices and methods that can achieve the usage of the “free of charge” thermal energy for defrosting and to diminish the necessary energy for forced convection thermal transfer from the warm fluid to the evaporator coils.
As a conclusion, this invention recaptures part of the waste heat that is normally rejected from the condensing coil and stores it in a high specific heat liquid. When the defrost cycle is required, the liquid is circulated through the evaporator coil chamber and the frost is melted with new energy that would normally be wasted, instead of being melted with new energy that is required from the power supply. The only outside energy used is the tiny amount required to run the circulation pump.
The existing electrical elements require a longer time to defrost because they are at higher temperature, but essentially a point source, so that by time the perimeters of the coil are defrosted, the center area of the evaporator chamber is heated to a very high level and this must be removed by the refrigeration cycle.
This invention, because it uses a lower temperature warming source that is evenly distributed throughout the coil chamber, melts the frost deposits faster without raising any part of the chamber higher than the others, therefore reducing the residual defrost heat that must be removed by the refrigeration cycle.
In summary, this invention reduces the energy consumed by the refrigeration unit in two ways:
1. It uses “free” energy that is rejected by the refrigeration cycle for defrost
2. It reduces the load on the refrigeration cycle caused by the defrost cycle because it causes less heating of the evaporator coil chamber.
It is also anticipated that the same goals can be achieved by a simplified arrangement (see
FIG. 7
) in which the thermal reservoir is warmed only
Pandaru Constantin
Wilson John
Bennett Henry
D. S. Inc. (Defrost Systems Inc.)
Defrost Systems Inc.
Jones Melvin
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