GB2148553A - Heat pump system - Google Patents
Heat pump system Download PDFInfo
- Publication number
- GB2148553A GB2148553A GB08328307A GB8328307A GB2148553A GB 2148553 A GB2148553 A GB 2148553A GB 08328307 A GB08328307 A GB 08328307A GB 8328307 A GB8328307 A GB 8328307A GB 2148553 A GB2148553 A GB 2148553A
- Authority
- GB
- United Kingdom
- Prior art keywords
- heat pump
- motor
- circuit
- inverter
- speed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/02—Defrosting cycles
- F25B47/022—Defrosting cycles hot gas defrosting
- F25B47/025—Defrosting cycles hot gas defrosting by reversing the cycle
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/1927—Control of temperature characterised by the use of electric means using a plurality of sensors
- G05D23/193—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces
- G05D23/1931—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces to control the temperature of one space
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
- G05D23/24—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element having a resistance varying with temperature, e.g. a thermistor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B13/00—Compression machines, plants or systems, with reversible cycle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2500/00—Problems to be solved
- F25B2500/26—Problems to be solved characterised by the startup of the refrigeration cycle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/021—Inverters therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Air Conditioning Control Device (AREA)
Abstract
A heat pump system comprises a rectifier 10, a variable frequency inverter 14, an AC motor 17, and a heat pump circuit including a compressor 18, an evaporator 30 and a condensor 26. The condensor 26 forms part of a heat exchanger 35 associated with a central heating system. The system described also includes an air temperature control circuit 40, a circuit 42 for controlling the water temperature of the central heating system, and a defrosting control circuit 41 capable of detecting frosting. The outputs of these circuits are connected to the frequency control terminal of the inverter 14 through a soil start circuit 47. In operation, the frequency of inverter 14 is controlled so as to vary the speed of the compressor to achieve a desired air temperature and the soil start circuit limits the rate at which the frequency increases so as to keep the input current below a set value. When frosting is detected, the direction of refrigerent flow is reversed by a valve 20 and the speed of motor 17 is increased. Motor 17 is stopped if the water temperature exceeds a limit value. <IMAGE>
Description
SPECIFICATION
Heat pump system
This invention relates to a heat pump system and particularly, but not exclusively, to a heat pump system for use with a domestic or commercial central heating system.
A known type of heat pump system which may be used with a commercial or domestic central heating system comprises a fixed speed AC motor which is operated in an on/off mode, and a heat pump circuit including a compressor driven by the motor, an evaporator and a condensor. Because the motor is operated in an on/off mode, there are marked variations in the current demand which in turns causes a problem for the mains power supply. Also, in practice, the motor is usually a three-phase motor and so a separate inverter circuit is needed when the system is used with a single-phase mains supply.
It is an object of this invention to provide a new or improved heat pump system in which the above mentioned problems are overcome or reduced.
According to one aspect of this invention there is provided a heat pump system comprising a rectifier for receiving power from a mains supply, a variable frequency inverter the input of which is connected to the output of the rectifier, an AC motor driven by the output of the inverter, and a heat pump circuit including a compressor driven by the AC motor, an evaporator, and a condensor.
By using a variable frequency inverter to drive the motor, the speed of the motor and in consequence the rate at which heat is pumped may be varied continuously and so marked variations in the current demand can be avoided. Also, the provision of the variable frequency inverter means that the system can be used with a single-phase or three-phase supply without providing a separate inverter circuit.
Preferably, the system includes a circuit for controlling air temperature having an input for connection to an air temperature sensing means and providing an output signal for controlling the inverter so that, in use, the speed of the motor is varied in accordance with the output of the temperature sensing means.
Preferably, the system includes means for restricting the rate at which the speed of the motor increases so that, in use, the input current to the rectifier does not exceed an upper limit value.
Conveniently, the system includes a circuit for controlling water temperature having an input for connection to water sensing means and providing an output signal which, in use, reduces the speed of the motor if the water temperature exceeds an upper limit value.
In heat pump systems, the evaporators are prone to frosting and such frosting causes a reduction in efficiency. In one known type of heat pump system, the direction of coolant flow is reversed at fixed time intervals for a fixed period in order to prevent a build-up of frost on the evaporator. However, as operating conditions vary, this fixed operation will sometimes be insufficient to maintain the evaporator in a defrosted condition and at other times the operation will be excessive with a consequent reduction in efficiency.
It is another object of this invention to provide a new or improved heat pump system in which this problem is overcome or reduced.
According to another aspect of this invention there is provided a heat pump system comprising a heat pump circuit having a compressor driven by a motor, a condensor and an evaporator, means for detecting the presence of frost in the evaporator, and means responsive to the frost detecting means for reversing the direction of refrigerant flow when frost is detected.
The system may also include means for increasing the speed of the motor when the direction of refrigerant flow is reversed.
The frost detecting means may comprise one or more temperature sensing probes positioned on the evaporator.
This invention will now be described in more detail by way of example with reference to the accompanying drawing, which is a block diagram of a combined heat pump and domestic central heating system embodying this invention.
Referring now to the drawing, the combined heat pump and central heating system has a three-phase full wave rectifier 10 which has three input terminals 11, 1 2 and 1 3.
When the system is used with a three-phase mains supply, all three input terminals are used and when the system is used with a single-phase mains supply only terminals 11 and 1 2 are used. The output of the rectifier 10 is connected to the input of a variable frequency three-phase inverter 14. When the system is used with a single phase supply, a capacitor is inserted between the rectifier 10 and inverter 14 to smooth the ripple voltage.
The inverter 14 provides three-phase output power on a set or rails 15, the frequency of which is varied in accordance with the control signal on the rail 16. The rails 15 are connected to the input terminals of a three-phase motor 17. The output voltage of the inverter 14 increases with frequency, the exact relationship between the output voltage and frequency being determined by the characteristics of the motor 17.
The motor 1 7 drives a compressor 1 8 which forms part of a heat pump circuit. The heat pump circuit uses the refrigerant R22 (monochlorodifluormethane) as its refrigerant.
The output of the compressor 1 8 is connected through a tube 1 9 to a port 20 of a reversing valve 21. A port 22 is connected through a tube 23 to the input compressor 1 8. A port 24 of valve 21 is connected through a tube 25, a condensor 26, a tube 27, a throttle valve 28, a tube 29, an evaporator 30, and a tube 31 to a port 32. The heat pump circuit also includes a suction accumulator.
The rectifier 10, inverter 14, motor 1 7 and the heat pump circuit are provided outside the building which it is desired to heat. A fan is provided to drive outside air over a evaporator 30. In normal operation, refrigerant flows from the output of compressor 1 8 through condensor 26, throttle valve 28, and evaporator 30 to the input of compressor 18. In order to defrost the evaporator 30, the reversing valve 21 is driven to its reversing position by a solenoid 33, which will be described below, thereby causing the refrigerant to flow from the evaporator 30 through the throttle valve 28 to the condensor 26.
The condensor 26 is combined with a heating element 34 as a heat exchanger unit 35, the heating element 34 forming part of a domestic central heating system. The central heating system uses water as the heating fluid and water passes from the heating element 34 through a tube 39 to the input of the pump 36. Water passes from the output of pump 36 through radiators which are positioned where heating it required and in the present example three such radiators 37 are shown by way of example. Water passes from the radiators 37 through tube 38 to the input of heating element 34.
The system also includes an air temperature control circuit 40, a defrosting control circuit 41, and a water temperature control circuit 42. The air temperature control circuit 40 comprises a potentiometer R1 connected between a positive supply rail and earth, a tapping on potentiometer R1 being connected through a resistor R2 to the inverting input of an operational amplifier Al. The positive supply rail is also connected through a resistor
R3 to a terminal 43 which is associated with a terminal 44 connected to earth. Terminals 43 and 44 provide an input for circuit 40 and these terminals are connected through a pair of leads to a thermistor 45 positioned in a room, the air temperature of which it is desired to control.Terminals 43 is connected to the non-inverting input of amplifier Al and the output of this amplifier is connected to its non-inverting input through resistor R4. The output of amplifier Al is connected through a pair of resistors R5 and R6 to earth, and the junction of these resistors is connected through a diode D1 to rail 46. In operation, the potentiometer R1 is set to the desired temperature and the output voltage of amplifier Al varies in accordance with the difference between the desired temperature and the sensed temperature.
Rail 46 is connected through a soft start circuit 47 to rail 16 which provides a control signal for inverter 14. The soft start circuit 47 limits the rate at which the voltage on rail 1 6 increases and consequently the rate at which the speed of motor 1 7 increases so that the maximum current demanded by rectifier 10 does not exceed a predetermined value which in the present example is 1.1 5 times the full load current for motor 1 7. Thus, the soft start circuit 47 ensures that high surge currents are avoided.
The resistors R5 and R6 are selected so that when the output of amplifier Al is at its maximum value the control signal on rail 1 6 ensures that the motor is driven at its normal rated speed.
The defrosting control circuit 41 comprises a potentiometer R7 connected between the positive supply rail and earth, the tapping on this potentiometer being connected to the non-inverting input of an operational amplifier
A2. The positive rail is also connected through a pair of thermistors 48 and 49 to a rail 50, the rail 50 being connected through a resistor
R9 to earth and also to the inverting input of the amplifier A2. The resistors 48 and 49 are positioned on the fins of the evaporator 30 and serve to detect when frosting occurs. The output of amplifier A2 is connected through solenoid 33 to earth and also through a pair of resistors R10 and Tri 1 to earth. The junction of these resistors is connected through a diode D2.In operation, when frosting is detected, the output of amplifier A2 goes high thereby driving the valve 21 into its reversing position and also providing a high signal on rail 46. The resistors R10 and R11 are selected so that when the output of amplifier A2 is at its maximum value the motor 1 7 operates at approximately 15% above its normal rates of speed. Thus, defrosting is performed as quickly as possible and when the resistors 48 and 49 detect the absence of frost the output of amplifier A2 goes low and normal operation resumes.
The water temperature control circuit 42 comprises a potentiometer 51 connected between the positive supply rail and earth, a tapping of this potentiometer being connected to the negative input of a comparator A3. The
positive supply rail is also connected to a terminal 52 associated with a terminal 53 which is connected to earth through a resistor R12. The terminal 53 is also connected to the
positive input of amplifier A3. The terminals
52 and 53 provide an input for the water temperature control circuit and these terminals
are connected through a pair of leads to a thermistor 54 which is positioned in tube 35
so as to detect the water temperature. The
output of comparator A3 is connected through
a positive feedback resistor R 13 to the positive input and also to the base of an NPN transistor 55, the emitter of which is con
nected to earth and the collector of which is connected to rail 46. In operation, the potentiometer 51 is set to the upper limit value for the water temperature and, when the temperature exceeds this value, the output of comparator A3 goes high thereby grounding rails 46 and 16 and stopping motor 17. When the water temperature falls sufficiently for the output of comparator A3 to go low, normal operation resumes.
The rectifier 10 may conveniently be connected to the mains supply through a time controlled switch. Where a single phase mains supply is used, the same switch may be used to provide power to the pump 36 and to the fan associated with the evaporator 30. Where a three-phase supply is used, the pump 36 and fan may be connected to a single phase supply through a second switch which is ganged to the first switch.
When the system is energised, the speed of motor 1 7 increases under the control of the soft start circuit 47. If the temperature sensed by thermistor 45 is less than that demanded on potentiometer R1, the speed will increase until it reaches its normal rated speed. When the sensed temperature approaches the demanded temperature, the speed of motor 1 7 is controlled by the circuit 40 so as to maintain the temperature at or near to the desired value. As mentioned above, if frosting is detected, the direction of refrigerant flow is reversed under the control of circuit 41. Normally, the temperature control circuit 40 will prevent the water temperature exceeding the upper limit value but, as mentioned above, the circuit 42 operates as an override circuit if this value is exceeded.
Although the heat pump system has been described with reference to a central heating system, it is to be appreciated that the heat pump system is not limited to this use. For example, it may also be used with a air conditioning system or with a refrigeration system.
Claims (8)
1. A heat pump system comprising a rectifier for receiving power from a mains supply, a variable frequency inverter the input of which is connected to the output of the rectifier, an AC motor driven by the output of the inverter, and a heat pump circuit including a compressor driven by the AC motor, an evaporator, and a condensor.
2. A heat pump circuit as claimed in claim 1 in which the system includes a circuit for controlling air temperature having an input for connection to an air temperature sensing means and providing an output signal for controlling the inverter so that, in use, the speed of the motor is varied in accordance with the output of the temperature sensing means.
3. A heat pump system as claimed in claim 1 or claim 2 in which the system includes means for restricting the rate at which the speed of the motor increases so that, in use, the input current to the rectifier does not exceed an upper limit value.
4. A heat pump as claimed in any one of the preceding claims in which the system includes a circuit for controlling water temperature having an input for connection to a water temperature sensing means and providing an output signal which, in use, reduces the speed of the motor if the water temperature exceeds an upper limit value.
5. A heat pump system comprising a heat pump circuit having a compressor driven by a motor, a condensor and an evaporator, means for detecting the presence of frost in the evaporator, and means responsive to the frost detecting means for reversing the direction of refrigerant flow when frost is detected.
6. A heat pump system as claimed in claim 5 in which the system also includes means for increasing the speed of the motor when the direction of refrigerant flow is reversed.
7. A heat pump system as claimed in claim 4 or claim 6 in which the frost detecting means comprises one or more temperature sensing probes positioned on the evaporator.
8. A heat pump system substantially as hereinbefore described with reference to and as shown in the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08328307A GB2148553A (en) | 1983-10-22 | 1983-10-22 | Heat pump system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08328307A GB2148553A (en) | 1983-10-22 | 1983-10-22 | Heat pump system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8328307D0 GB8328307D0 (en) | 1983-11-23 |
| GB2148553A true GB2148553A (en) | 1985-05-30 |
Family
ID=10550612
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08328307A Withdrawn GB2148553A (en) | 1983-10-22 | 1983-10-22 | Heat pump system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2148553A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0270474A1 (en) * | 1986-12-01 | 1988-06-08 | Carrier Corporation | Electrically commutated, variable speed compressor control system |
| EP0347821A2 (en) * | 1988-06-21 | 1989-12-27 | Daikin Industries, Limited | Temperature controller of liquid cooling system |
| EP2157684A1 (en) * | 2007-06-04 | 2010-02-24 | Panasonic Corporation | Electric power source control device and heat pump device using the electric power source control device |
| CN102401520A (en) * | 2011-10-24 | 2012-04-04 | 江苏春兰空调设备有限公司 | Dehumidifier with intelligent defrosting function |
| CN104266424A (en) * | 2014-09-18 | 2015-01-07 | 广东芬尼克兹节能设备有限公司 | Variable-frequency control system and variable-frequency control method for heat pump |
| EP2360439A4 (en) * | 2009-12-28 | 2016-07-06 | Daikin Ind Ltd | Heat pump system |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2133907A (en) * | 1983-01-17 | 1984-08-01 | Tokyo Shibaura Electric Co | Air conditioning system |
-
1983
- 1983-10-22 GB GB08328307A patent/GB2148553A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2133907A (en) * | 1983-01-17 | 1984-08-01 | Tokyo Shibaura Electric Co | Air conditioning system |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0270474A1 (en) * | 1986-12-01 | 1988-06-08 | Carrier Corporation | Electrically commutated, variable speed compressor control system |
| EP0347821A2 (en) * | 1988-06-21 | 1989-12-27 | Daikin Industries, Limited | Temperature controller of liquid cooling system |
| EP0347821A3 (en) * | 1988-06-21 | 1991-07-10 | Daikin Industries, Limited | Temperature controller of liquid cooling system |
| EP2157684A1 (en) * | 2007-06-04 | 2010-02-24 | Panasonic Corporation | Electric power source control device and heat pump device using the electric power source control device |
| EP2157684A4 (en) * | 2007-06-04 | 2012-08-08 | Panasonic Corp | Electric power source control device and heat pump device using the electric power source control device |
| EP2605394A3 (en) * | 2007-06-04 | 2015-10-21 | Panasonic Corporation | Power-supply control apparatus and heat pump apparatus having the power-supply control apparatus |
| EP2360439A4 (en) * | 2009-12-28 | 2016-07-06 | Daikin Ind Ltd | Heat pump system |
| CN102401520A (en) * | 2011-10-24 | 2012-04-04 | 江苏春兰空调设备有限公司 | Dehumidifier with intelligent defrosting function |
| CN104266424A (en) * | 2014-09-18 | 2015-01-07 | 广东芬尼克兹节能设备有限公司 | Variable-frequency control system and variable-frequency control method for heat pump |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8328307D0 (en) | 1983-11-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |