KR20010041038A - Heat pump having improved defrost system - Google Patents

Abstract

The heat pump system includes a compressor (10) in an operable relationship for transferring heat between an external atmosphere and an internal atmosphere via a fluid refrigerant; Internal heat exchanger 12; External heat exchanger 14; Accumulator 16; Heating means 18, 18 ′, 18 ″, 18 ′ ″ for heating the accumulator 16 and / or piping lines 25, 26, 27 to defrost the external heat exchanger 14. Include.

Description

Heat pump with improved defrost system {HEAT PUMP HAVING IMPROVED DEFROST SYSTEM}

Heat pumps are well known and are used to heat and / or cool enclosed spaces, such as buildings. Heat pumps generally comprise a heat exchange fluid (commonly called a refrigerant) circulated between an internal heat exchanger inside the closed space and an external heat exchanger outside the closed space.

While the heat pump is operating in the normal heating mode, the external heat exchanger is cooler than the external environment to absorb heat from the external environment, and the internal heat exchanger is warmer than the internal environment to transfer heat to the internal environment. Thus, heat is “pumped” from the cooled external environment to the internal environment.

When the external temperature is near or below the freezing point of the water, ice (frost) is usually formed on the external heat exchanger, which greatly degrades the heat pump performance. Thus, defrost means are generally employed in heat pump systems.

The use of reversing defrost systems of heat pumps in heat pumps is well known. Such defrosting systems are generally designed to melt ice formation and evaporate water from an external heat exchanger to minimize the adverse effects of ice during the heat exchange process. Such defrost systems are generally operated after one cycle of heat pump operating time, and generally until the external heat exchanger reaches a temperature which ensures the removal of all or at least most of the ice and water.

During the defrost cycle, the heat pumps are generally reversed. The external heat exchanger is warmed and the internal heat exchanger is cold. A secondary internal heater (usually an electrical resistance heater or combustion heater) is activated to compensate for the heat absorbed by the internal heat exchanger during the defrost cycle.

If the heat capacity of the heat pump does not meet the building's heating load requirements, conventional heat pumps run auxiliary resistance heating coils to meet the required load. This may cause the variation of the internal temperature to be large, and may lower the operating efficiency.

Under the agreement of DE-AC05-84OR21400 between the United States Department of Resources and Lockheed Martin Energy Systems, and also under the agreement of DE-AC05-96OR22464 between the United States Department of Resources and Lockheed Martin Energy Systems, the United States Government has the right to the invention. have.

FIELD OF THE INVENTION The present invention relates to heat pumps with circulating defrost systems, more particularly employing means for reducing the frequency, duration and energy consumption of defrost cycles, while internally (internal) thermal stability to such heat pumps that increase thermal comfort.

1 is a schematic illustration of a heat pump with separate heating means added to the accumulator in accordance with the invention, showing circulation in the cooling mode / second defrost cycle.

Figure 2 is a schematic diagram of a heat pump with separate heating means added to the accumulator in accordance with the present invention, showing circulation in the heating mode / first defrost cycle.

In addition to other additional objects, advantages and possibilities for the present invention, reference is made to the appended claims and the following disclosure, taken in conjunction with the foregoing drawings, in order to provide a better understanding of the invention.

It is therefore an object of the present invention to provide a heat pump having a novel and improved defrost cycle system.

It is another object of the present invention to provide a heat pump defrost cycle system that significantly reduces the reversal cycle of a heat pump.

It is still another object of the present invention to provide a heat pump defrost cycle system that significantly improves the reliability of the heat pump.

It is a further object of the present invention to provide a heat pump defrost cycle system which significantly reduces the amount of energy during the defrost cycle.

Further objects of the present invention will become apparent from the specification described herein.

According to one aspect of the present invention, another object described above is a compressor in an operating relationship for transferring heat between an external atmosphere and an internal atmosphere via a fluid refrigerant; Internal heat exchanger; External heat exchanger; Accumulators; And individual heating means for heating the fluid refrigerant to defrost an external heat exchanger, wherein the heat pump can be operated in a heating mode for transferring heat from an external atmosphere to an internal atmosphere. have.

According to another aspect of the present invention, a method of heating a closed space comprises: a. In an operating relationship for transferring heat between an external atmosphere and an internal atmosphere via a fluid refrigerant, a compressor; Internal heat exchanger; External heat exchanger; Accumulators; And a separate heating means for heating said fluidic refrigerant to defrost an external heat exchanger, said heat pump being operable in a heating mode for transferring heat from an external atmosphere to an internal atmosphere. Providing such a heat pump system; b. Operating the heat pump in the heating mode; And c. Operating said individual heating means to defrost said external heat exchanger in a defrost cycle.

The present invention usually removes cold air draft (reducing the time required for the defrost cycle) during the defrost cycle of the heat pump by adding separate heating means for heating the fluid refrigerant through the accumulator. Such means may be separate from the heat pump circuit and individually controlled, and may be any structure suitable for applying heat to an electrical resistance heater, any type of combustion heater, or the accumulator.

1 and 2 show the basic heat exchange circuit of the heat pump system according to the invention in cooling and heating mode, respectively. In this figure, the accumulator 16 containing the compressor 10, the internal heat exchanger 12, the external heat exchanger 14, the fluid refrigerant 17, the accumulator 16 and / or the piping lines 25, Separate heating means 18, 18 ′, 18 ″, and / or 18 ′ ″, respectively, for heating 26, and / or 27, first and second expansion devices 20, 22, Shown are first and second check valves 21 and 23, respectively, and a reversing valve 24 of the heat pump. Those skilled in the art will appreciate that complete heat pumps generally further comprise a conventional power source, various control systems, and various other systems and sub-systems.

Heat Pump Operation in Cooling Mode:

Referring now to FIG. 1, the reversing valve 24 of the heat pump is in the cooling mode position, with the result that the internal heat exchanger 12 serves as an evaporator and the external heat exchanger 14 serves as a condenser. The cooling vapor refrigerant flows from the compressor 10 to the external heat exchanger 14 to condense into a high temperature, high pressure liquid. This liquid is evaporated in the internal heat exchanger 12 through the second check valve 23 and then the first expansion device 20. This steam refrigerant passes through the accumulator and returns to the compressor 10 to end the cycle.

Heat pump operation in heating mode:

Referring now to FIG. 2, the reversing valve 24 of the heat pump is in the heating mode position, with the result that the external heat exchanger 14 serves as an evaporator and the internal heat exchanger 12 serves as a condenser. The cooling vapor refrigerant flows from the compressor 10 to the internal heat exchanger 12 to condense into a high temperature, high pressure liquid. This liquid is evaporated in the external heat exchanger 14 through the first check valve 21 and then the second expansion device 22. This vapor refrigerant passes through the accumulator and returns to the compressor 10 to end the cycle.

Heating Mode / First Defrost Cycle (FIG. 2)

The present invention significantly reduces the number of reversals of the heat pump for defrosting. If the external heat exchanger 14 needs to be defrosted and the external environmental temperature is at least about 32 ° to 36 ° F, the desired defrost effect is achieved by the present invention without reversing the heat pump.

The minimum external environmental temperature for the actual operating capacity of such a defrost cycle is at least two factors, i.e. 1) the amount of heat applied by the respective heating means with respect to the capacity of the heat pump, and 2) the heat pump It depends on the climatic state in which it works. A minimum external environmental temperature preselected in the range of about 32 ° F. to 36 ° F. is proposed for residential and commercial heat pumps under normal conditions. The preferred preselected minimum temperature is usually in the range of about 34 ° F. to 35 ° F. under normal temperature climatic conditions. If the external environmental temperature is at or above a preselected minimum external environmental temperature, the means for controlling the heat pump operation, such as the heat pump control system 30, including, for example, the external temperature sensor 35, may be used to heat the first defrost cycle. Cause it to work without reversal. In other words, the heat pump control system keeps the heat pump in heating mode during the first defrost cycle.

Heat is preferably applied to the accumulator 16 by heating means 18. Heat is shown in section 26 of the flue line between accumulator 16 and heat pump reversing valve 24, shown as heating means 18 ′, and / or as heating means 18 ″, It may be selectively or additionally applied to the section 27 of the flue line between the heat pump reversing valve 24 and the external heat exchanger 14. The heating means 18 may be another conventional device or an electrical resistance heater that may be suitable for applying heat to the system as described above.

Upon application of sufficient heat as described above, a pressure drop (suction pressure) of the second expansion device 22 occurs, whereby the temperature of the external heat exchanger 14 generally rises to a temperature above 32 ° F. Defrost the external heat exchanger. Thus, defrost is also achieved when the heat pump is still in heating mode of operation.

Since frost is most likely to form on the external heat exchanger 14 when the external environmental temperature is in the range of about 32 ° F. to 40 ° F., use the invention described above at the minimum preselected temperature as described above. As a result, the overall efficiency of the heat pump system is significantly increased.

Example I

A two-ton capacity air conditioner as described above, charged with R-22 refrigerant, was used to test the present invention as described above. The test results indicated that the suction pressure was increased by 8 psi, indicating that the heat exchanger 14 temperature increased 1200 BTU / Hr for the accumulator 16 by about 6 degrees Fahrenheit.

The application of additional heat through separate heating means further raises the temperature of the external heat exchanger 14. As described above, the applied heat is fully utilized when supplied to the house through the compressor 10. Due to the suction pressure and temperature of the elevated compressor, the heating capacity of the compressor 10 rises. By increasing the heating capacity of the heat pump, elimination of internal cold air drag associated with heat pump reversal, internal thermal stability is improved. Since the number of heat pump reversals in the defrost cycle is reduced, the heat pump reliability is improved.

Reversing mode / second defrost cycle (FIG. 1)

When the external environmental temperature falls below the preselected temperature as described above, the heating capacity of the heating means is no longer sufficient to effectively raise the temperature of the external heat exchanger 14 to above 32 ° F. In this state, the heat pump control system 30 causes a normal heat pump reversal during the defrost cycle. The refrigerant flow valve 24 is temporarily switched to the cooling mode position, as a result of which the heat pump operates in the reverse mode as described above. However, the present invention is distinguished from conventional heat pump reversal defrost cycles as described below.

The heat pump reversal can be simultaneous by the activation of the heating means 18, 18 ′, 18 ″, and / or 18 ′ ″ or delayed for a short time, which in any case is more efficient for a particular application. to be.

The heat required for evaporation of the refrigerant is preferably applied to the accumulator 16 by the heating means 18. Heat is shown in the section 26 of the piping line between the accumulator 16 and the heat pump reversing valve 24, shown as heating means 18 ′, and / or as heating means 18 ′ ″. May be selectively or additionally applied to the section 25 of the piping line between the heat pump reversing valve 24 and the internal heat exchanger 12. The internal blower 40 is preferably not operated (off) during this type of defrost cycle.

Refrigerant boiling in the accumulator 16 (and / or in the piping lines 25, 26) will raise the suction temperature and pressure. Thus, the compressor heating capacity rises immediately. This eliminates the need for the use of an auxiliary heater of a conventional resistance type (not shown) which is ubiquitous except under conditions of very cold external environmental temperatures.

During the first two minutes of defrost cycles, conventional heat pumps generally compress almost all refrigerant into the accumulator due to the reversal of the heat pump, which leads to a "low refrigerant" compressor. This delays the effect of the defrost cycle. In contrast, the present invention boils the liquid refrigerant almost instantaneously in the accumulator (and / or in the piping lines 25, 26), which avoids the "lack of refrigerant" of the compressor, thus accelerating the defrost process.

New liquids that overfeed air conditioning systems have been demonstrated to increase cooling capacity and coefficient of performance. This system is disclosed in U.S. Patent No. 5,245,833, issued Sep. 21, 1993, entitled "Liquid Oversupply to Air Conditioning Systems," the disclosures of which are incorporated herein by reference in their entirety. have. The principle of overfeeding liquids taught in that document can be applied to the preferred embodiment of the heat pump described in the present invention. In this system, the refrigerant must be charged so that the liquid refrigerant is present in the accumulator heat exchanger in order to take advantage of the liquid overfeed principle.

The invention described above can be used in heat pumps with or without the feature of liquid oversupply. In a preferred liquid oversupply heat pump, the accumulator heat exchanger 16 generally contains a liquid refrigerant at all times. When heat is applied to the accumulator heat exchanger 16, the refrigerant therein boils and raises the suction pressure.

In conventional (non-liquid excess supply) heat pumps, when frost begins to form on the outer coil, the refrigerant generally begins to accumulate in the accumulator. During the defrost cycle, the heat input to the accumulator according to the present invention boils the refrigerant in the accumulator, increasing the suction pressure and temperature, leading to substantially the same results as in the case of a liquid oversupply heat pump.

Some of the advantages of the present invention are as follows.

1. Internal thermal stability is improved. In the case of conventional heat pump systems, during the defrost cycle, although the internal electrical resistance heating coil is in operation, the temperature of the air circulating through the internal air treatment system (not shown) is still only about 65-70 ° F. When such an air draft is blown on people, people generally feel cold. In the case of the present invention, there is no reversal of the heat pump while the external environment is at least a preselected temperature. This heat pump continues to operate in the heating mode while the frost on the external heat exchanger 14 coil is melting. At the same time, the heating capacity of the heat pump is increased, and the compressor efficiency is improved.

In the case of a low temperature external environment, the heat pump is reversed as in a conventional system for defrosting. However, the electric blower (not shown) on the internal heat exchanger 12 usually does not work and eliminates internal cold ventilation.

In addition, in the case where the heat capacity of the heat pump is smaller than the required heating load, for example, when the external environmental temperature is very low, a typical heat pump system may use an internal auxiliary resistance heating coil (not shown) to compensate for the required heating capacity. Omit). In general, people feel warm when the electrical resistance coil is in operation, but cold when the resistance coil is not in operation. In the case of the present invention, the heating means 18 supplies sufficient heat to the accumulator 16, as a result of which the compressor 10 efficiency is immediately raised and more heat is supplied into the interior. This eliminates large variations in most internal temperatures, thus improving internal thermal stability.

2. Heat pump reliability is increased. It is known that reversal of the heat pump during the defrost cycle provides a significant mechanical and electrical stress to the heat pump system. Since the number of heat pump reversals in the defrost cycle is drastically reduced, the reliability of the heat pump, in particular the compressor, is improved.

One example is the American Society of Heating, Refrigerating, and Air Conditioning Engineers, chapter 28, 28.11 (North East Atlanta Georgia 30329 197129 Tullie Circle, NE, Atlanta Georgia 30329), based on the 1989 edition of the ASHRAE Handbook Foundation. Can be provided according to data in the company). In the Knoxville area of Tennessee, the average external environment temperature is in the range of 37 ° F. to 42 ° F., averaged 1238 hours per year, and below 32 ° F. on average. In the case of a heat pump that defrosts for 90 minutes at a time, a total of 1388 cycles of hip pump reversal are required for a conventional heat pump. The present invention eliminates 825 heat pump inversions (about 60%). Such a sharp reduction in heat pump reversal improves heat pump reliability.

3. Energy consumption is reduced. A conventional resistance type auxiliary heater (not shown) does not operate during the defrost cycle because its function is not replaced by the heating means 18. Since this heating means 18 is directly attached to the accumulator 16, the heat transfer between the refrigerant and the heating coil is direct and much more efficient than the heat transfer of the internal coil, air and auxiliary heaters of conventional resistance type. In addition, since the internal fan is preferably inactive during the second defrost cycle, the blower 40 power is likewise saved.

4. The time required for the defrost cycle is significantly shortened. During the defrost cycle of a conventional heat pump, the heat pump is reversed and the liquid refrigerant is pushed into the accumulator causing a "lack of refrigerant" as described above. The present invention overcomes this drawback by applying heat directly to the accumulator and immediately boiling the refrigerant in the accumulator 16. Thus, the defrost cycle is shortened.

The present invention can be applied to new hip pumps, including the installation of a heat pump control unit (not shown) and heating means 18, which can be easily applied to a particular application and can be installed by those skilled in the art. And can be retrofitted into existing heat pumps with minimal investment.

The invention may also be used in refrigeration systems employing defrost cycles for faster and more energy efficient defrosting.

The present invention is also useful for electric vehicles. The use of hip pumps to supply heat to compact cars among electric vehicles is desirable, but efficient defrosting has been a major problem. With the present invention, compact cars do not have cold ventilation, and the energy savings provided thereby lead to an extension of the operating area.

While what has been considered and described as presently preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made within the invention without departing from the scope of the invention as defined by the appended claims.

Claims (16)

In an operable relationship for transferring heat between an external atmosphere and an internal atmosphere via a fluid refrigerant, the compressor; Internal heat exchanger; External heat exchanger; Accumulators; Heat pump reversing valve; And heating the accumulator, the section of the piping line between the accumulator and the heat pump reversing valve, and the fluid refrigerant to intake pressure to defrost the external heat exchanger during a defrost cycle in which the heat pump continues to operate in the heating mode. And individual heating means arranged in heat transferable contact with at least one of the sections of the piping line between the external heat exchanger and the heat pump reversing valve to raise the pressure. The method of claim 1, Said individual heating means being in heat transferable contact with said accumulator. The method of claim 1, And control means for controlling a defrost cycle to defrost the external heat exchanger, the control means having movable means for operating the respective heating means. The method of claim 3, wherein And said control means comprises means for maintaining said heat pump in a heating mode during said defrost cycle when an external environmental temperature is at least a preselected temperature. The method of claim 4, wherein The defrost cycle is a first defrost cycle and the individual heating means accumulate the accumulator to defrost the external heat exchanger during a second defrost cycle in which the heat pump operates in an inverted mode when the external environmental temperature is below the preselected temperature. And heat transfer with at least one of a section of piping line between the accumulator and the heat pump reversing valve and a section of piping line between the internal heat exchanger and the heat pump reversing valve for heating the fluid refrigerant to increase suction pressure. Heat pump system, characterized in that arranged in contact. The method of claim 4, wherein And said preselected temperature is set to a temperature in the range of about 32 ° F to 36 ° F. a. In an operating relationship for transferring heat between an external atmosphere and an internal atmosphere via a fluid refrigerant, a compressor; Internal heat exchanger; External heat exchanger; Accumulators; Heat pump reversing valve; And in contact with at least one of the accumulator, a section of a piping line between the accumulator and the heat pump reversing valve, and a section of a piping line between the external heat exchanger and the heat pump reversing valve for heating the fluid refrigerant. Providing a heat pump system having individual heating means disposed thereon; b. Operating the heat pump in the heating mode; And c. Intermittently operating a defrost cycle comprising operating said individual heating means to defrost said external heat exchanger, thereby maintaining said heat pump in heating mode while raising said suction pressure. Closed space heating method. The method of claim 7, wherein And said operating step is performed by transfer of heat from said individual heating means to said accumulator. The method of claim 7, wherein The operating step is a closed space heating method, characterized in that performed by the control means for controlling the defrost cycle. The method of claim 7, wherein And wherein said operating step further comprises maintaining said heat pump in a heating mode during said defrost cycle when an external environmental temperature is at least a preselected temperature. The method of claim 10, And said preselected temperature is set to a temperature in a range from about 32 ° F to 36 ° F. a. In an operating relationship for transferring heat between an external atmosphere and an internal atmosphere via a fluid refrigerant, a compressor; Internal heat exchanger; External heat exchanger; Accumulators; Heat pump reversing valve; And individual heating means arranged in heat transferable contact with at least one of said accumulator, a section of piping line between said accumulator and said heat pump reversing valve, and a section of piping lines between said internal heat exchanger and said heat pump reversing valve. Providing a heat pump system having; b. Operating the heat pump in the heating mode; And c. Intermittently operating a defrost cycle comprising decoupling the reversing valve and deactivating the respective heating means to raise the suction pressure to defrost the external heat exchanger when the external environmental temperature is below a preselected temperature. Closed space heating method comprising the ;. The method of claim 12, The defrost cycle further comprises deactivating a blower on the internal heat exchanger. The method of claim 12, And said operating step is performed by transfer of heat from said individual heating means to said accumulator. The method of claim 12, The operating step is a closed space heating method, characterized in that performed by the control means for controlling the defrost cycle. The method of claim 12, And said preselected temperature is set to a temperature in a range from about 32 ° F to 36 ° F.