Patent Application
20180340713
This invention relates to improvements in closed vapor compression cycle cooling or refrigerating devices, including most refrigerators and some HVAC equipment.
Most household and industrial refrigerators work by continuously repeating a vapor compression cycle in closed and sealed fluid flow circuit, which comprises a gas compressor, a hot side vapor condenser coil, an expansion valve or a capillary coil or other throttling device and a cold side liquid evaporator coil, using Freon or other coolant or refrigerant liquid, while the compressor is powered by electricity from the grid which supplies 120-460V AC, whereas said hot and cold sides are separated by heat insulation and the cold side is in the space to be cooled and the hot side is out side of it, so the refrigerator transports heat from inside out.
The cold space in a household refrigerator is a heat insulated food storage cabinet, often split to deep freezer and regular freezer compartments, while these two spaces may be separated by doors lids or drawers. The evaporator coil or radiator may also be split accordingly. The throttling device typically receives plus 90-45° C., 8 bar liquid and passes −20° C., 0.6 bar vapor as gas. Depending on the cooled state of the food stored in the cold compartments, the compressor typically receives −20° C. 0.6 bar vapor at low speed and passes plus 90° C., 8 bar vapor as gas at high speed.
The kinetic energy of the compressor's discharge gas is not utilized. Improvement on the state of art is therefore in order.
The objective of the invention is to convert the compressor's discharge gas kinetic energy to electricity to feed it back to the grid, thereby reducing overall electrical power consumption of refrigeration.
It is proposed that a closed and sealed impact turbine be inserted in the pipeline connecting the compressor and the condenser, while the turbine would drive a permanent magnet alternator or generator (PMA/PMG), generating 12-48V low voltage DC, which passing through an inverter would be plugged in to the wall socket, next to the socket used to take AC power to run the compressor. After some heat and electrical losses, the overall efficiency of the refrigeration improves considerably, alas at the expense of a slight lengthening of the refrigeration time. Should rapid initial refrigeration be required for warm food cooling, the turbine may be bypassed temporarily, controlled by thermostat or other electronic controller, which would actuate the bypass valve.
The above problems and others are at least partially solved and the above objects and others realized in a process, which according to the teachings of this invention, uses a power saving apparatus in the vapor compression cycle, inserted in the pipeline connecting the compressor and the condenser in two distinct ways:
In one embodiment, the apparatus comprises
In another embodiment, the apparatus comprises
In both configurations, the AC power may be switched, on-and-off manually or controlled electronically and the servo-valve may be substituted by manual valve.
The micro-turbine reduces flow rate and temperature of the hot vapor. The more resistance it has against the vapor flow, the longer the refrigeration cycle is extended by more time needed to cool the food in the refrigerator. Cooling time however seldom considered. The overall refrigeration efficiency may increase by 32% and the vapor cycle efficiency by 13%.
To compare refrigeration technologies, the industry uses the Coefficient of Performance (CoP) indicator. The energy balance is expressed as PINPUT+QABSORBED=QREJECTED, where PINPUT is the supplied electrical power, QABSORBED is the heat absorbed from the food in the refrigerator via the evaporator, inside the heat insulated space, and QREJECTED is the heat added to the room around the refrigerator via the condenser, outside the heat insulated space.
For the state of art refrigerator, CoP=QABSORBED/PINPUT. For the modified refrigerator as per the teachings of the invention, CoPM=QABSORBED/(PINPUT−POUTPUT), where POUTPUT is the electrical power generated by the PMA. Since POUTPUT is always higher than zero, even at marginal power generation, CoPM>CoP.
Referring to the drawings:
Attention is now turned to
The coolant is selected to suit the application and the environment. For household refrigerator, due to environmental considerations and regulations thereof, the classical Chemorous/DuPont made/owned Freon group of R-12, R-13B1, R-22, R-502 and R-503 (CFC group) is now replaced by the HFC group of R-410A, R-404A, R-406A, R-407A, R-407C, R-408A, R-409A, R-410A, R-438A, R-500 and R-502. For other applications, ammonia, hydro-chlorofluorocarbons (HCFCs), sulfur dioxide, methyl chloride and other liquids or ethylene, propane, nitrogen, helium or other gases are used. It is common to add some synthetic oil to lubricate the compressor, but only the one, which needs lubrication.
The refrigeration capacity is commonly defined in “tons of refrigeration” (TR). 1 TR is the rate of heat removal required to freeze a short ton (2,000-lbs) 32° F. (0° C.) water. Since the rate of fusion for water is 144 Btu/lbs, 1 TR=12,000 Btu/h=3.517 kW. Common household food and beverage refrigerators are in the 1-5 tons (3.5-18 kW) region. Other applications include commercial, industrial, food processing, transport, electronics, medical and cryogenic refrigeration.
The circulating refrigerant transports heat from the heat insulated closed Refrigerated Space to outside of it. The coolant, almost always in liquid-with-vapor phase, is cold after passing the Throttle and before entering the Compressor, which is powered by grid AC from the Grid Plug across the Main Switch, which may interrupt the AC current flowing to the electrical motor of the Compressor. The coolant is hot after passing the Compressor and before entering into the Throttle. The heat rejection in the Condenser is at constant high temperature. The heat absorption in the Evaporator is at constant low temperature. The vapor is saturated before entering and superheated after leaving the Compressor. The vapor enters and leaves the Throttle saturated while undergoing adiabatic sudden expansion, which lowers the vapor temperature. The vapor absorbs heat from the food in the Evaporator and rejects it in Condenser, both as constant low and high temperature correspondingly. Both the Condenser and Evaporator are radiator type flat pipe-snakes, panels or coils.
The cold half loop is at −20° C. temperature at 0.6 bar pressure, while the hot half loop is at 90° C. to 45° C. temperature at 8 bar pressure. At ideal steady state flow Condenser heat transfer rate, the after Compressor temperature is conserved, up to the Throttle entry point. That is achieved with pure convection heat transfer. For instant, by chimney effect, when the air is stagnant around the refrigerator.
Fan may be added however to increase the airflow of the evaporator and water may be used as heat exchanging fluid for the condenser. To reduce cost and complexity, household refrigerators avoid such complications.
The STATE-OF-ART cycle of
Attention is now turned to
Shortly after the Compressor, Micro-turbine-PMA is inserted into the hot vapor half loop. The temperature and pressure drops on the turbine, which drives a permanent magnet alternator (PMA) or power generator (PMG). The generated DC is passed through the Inverter and the generated electrical power is returned as AC to the grid via another Grid Plug. The rest of the process remains intact. Should the Micro-turbine-PMA be needed to he bypassed temporally, further improvement is needed, as that is illustrated next.
Attention is now turned to
In this embodiment, the Selector-Valve directs the vapor either to the Micro-turbine-PMA via the direct line (full line) or to the Condenser via the bypass line (dashed). The generated AC power now is diverted from the Inverter via Isolation Switch 2 to the AC-out Plug. Alternatively, the DC power via Isolation Switch 1 is passed to the Grid Plug as described above. The condenser thus either gets hot (90° C.) or warm (45° C.) vapor. The Selector Valve may be operated manually or preferably electronically by a controlled electrical actuator coil.
To the skilled in the art of refrigerator building, it shall be obvious that the generated AC power may be directed to the compressor, instead to the Grid Plug.
Attention is finally turned to
The state of art cycle works as follows:
The liquid-vapor phase is within the hot shape dashed line boundary. The cycle starts at point 1. Branch 1-2 is the compression phase, which elevates the vapor pressure and temperature from Tc cold to Th hot temperatures in the vapor phase by the addition of Pin input power of the electricity driving the Compressor.
At constant pressure and temperature the vapor first goes to liquid-vapor at point A, then up to point 3, to the boundary of the phase states. This happens in the Condenser at Th temperature, while Qout heat, as heat output, is rejected to the environment (branch 2-3) outside of the heat insulated refrigerated closed space.
In the Throttle, the liquid-vapor suddenly drops temperature, down to Tc cold and loses pressure (phase change 3-4).
In the 4-1 closing Branch, in the Evaporator, the liquid-vapor expands at constant pressure, reaching the vapor phase boundary at point 1. In this Branch, the heat Qin, as heat input, of the food in the insulated refrigerated closed space is absorbed.
The process repeats indefinitely from hereon.
The modified novel cycle works as follows:
Up to point A, the same. At point A, which is at the phase state boundary, the liquid-vapor drops pressure and temperature to Tw warm (branch A-2*) while DC power Pout, as output power is scavenged. The rest of the process (2*-3*-4*-1) is similar to process 2-3-4-1. The process modification is indicated by labels in parenthesis.
From heron, the process repeats indefinitely.
Thermodynamics assures that the input and output heats are the same (Qin=Qout) and the difference between the two process-loop areas is equal the output power (Pout), while the modified process is somewhat slower than the state of art process. To the skilled in refrigeration technology, it shall be obvious that the refrigerated space must be heat insulated and its doors must be closed at all times, except for food and beverage loading-and-unloading, otherwise the refrigerator would consume power indefinitely without significantly cooling the food-and-beverage. Also that the added power-saver must scavenge only a limited portion of the power needed for vapor compression, while the food and beverage to be refrigerated is merely exemplary here.
Refrigerating power may be saved in proportion to V2-A/V2-3, where V2-A and V2-3 correspond to the vapor volumes of state transitions 2-A and 2-3 correspondingly. Observing
To the skilled in the art of refrigeration system design and technology, it shall be obvious that the proposed power saver device improves refrigeration economy without adding much complexity and price and can be added to any refrigeration system as aftermarket device or be integrated into the original refrigerator built for domestic or industrial use. It shall also be obvious that the generated power may be used within the refrigerator, for instance to drive a fan blowing ambient air to the condenser or to power the refrigerator's low voltage controls and door opening-closing actuators to eliminate their inverter.
The present invention is described above with reference to a preferred embodiment. However, those skilled in the art will recognize that changes and modifications may be made in the described embodiment without departing from the nature and scope of the present invention. For instance, adding thermocouples for supplemental DC power generation by bridging the hot and cold side, or using other than turbine kinetic impeller, or using multiple gate valves or servo-valves instead of a selector-valve, or generating AC, or multi-staging is intuitive and hereby instructive over the teachings of the invention and considered being within its scope.
Various further changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof.
Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is:
