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
  • F25B40/00—Subcoolers, desuperheaters or superheaters
• • 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
  • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
  • F25B2400/13—Economisers

Definitions

• the invention relates to the method of increasing the coefficient of performance and the output; specifically it deals with obtaining usable thermal energy - heat at a temperature of 50°C and more for heating and hot water from low-potential heat sources having a temperature as low as - 20°C and less using heat pumps.
• the heat pump must or can be equipped with other components, which enable improved operation of the heat pump;their use leads to various modifications.
• the basic function of the heat pump lies in the fact that liquid refrigerant is injected by the expansion device under great pressure to the heat pump evaporator, by which its temperature and pressure rapidly decrease.
• heat is absorbed from the surroundings (from the earth, air, water) as a result of the difference between the evaporating temperature of the refrigerant, e.g. - 10°C, and the ambient source of heat, e.g. -2°C.
• the injected liquid refrigerant becomes a gas in the evaporator, and compared to the evaporating temperature at the beginning of the evaporator, it is overheated by 3 - 5°C and more at the end of the evaporator.
• the overheated gaseous refrigerant has a temperature of - 7°C to -5°C.
• the gaseous refrigerant is compressed in the compressor.
• the increasing of pressure results in a temperature increase.
• the increase of the temperature of the gas of the refrigerant is also contributed to by the heat produced by friction of the moving parts of the compressor, and in the case of a hermetically sealed compressor also by the heat generated by the work of the electric motor.
• the heat energy obtained in this way is transmitted to the heating medium (water, air) in the condenser.
• the gaseous refrigerant is liquefied in this process and is thereby ready to be injected into the evaporator.
• the cycle is thus closed and runs over and over again.
• the heat pump For its operation, the heat pump requires a certain amount of energy, usually electrical. There are also other compressor drives, for example a combustion motor; or an absorption heat pump exists, which is powered by gas. Such heat pumps are not the subject of the invention.
• the energy collected from the nature is usually 1.5 to 4times higher than the energy consumed by the drive of the heat pump compressor.
• the measure of energy efficiency of the heat pump is therefore the ratio of the output energy and the energy for the drive.
• the ratio is called the coefficient of performance (COP). It is a dimensionless number and its size varies depending on the conditions normally within the limits of 2.5 or less, but always more than 1 to 5 and more.
• the sucked-in vapours can be cooled by a direct injection of the corresponding amount of the liquid refrigerant into the compressor suction line.
• a thermostatic expansion valve is used, which - in accordance with the temperature of overheated vapours - injects the liquid refrigerant from the receiver of the liquid refrigerant. Lit. (1)
• the Copeland Company uses the spraying of the liquid refrigerant into the space between the rotors of the compressor.
• a capillary or a special DTC injector valve is used as an injecting body, which is controlled by the temperature of the refrigerant vapours at the discharge part behind the compressor.
• the liquid refrigerant is injected from the receiver of the refrigerant. Lit. (4)
• the gaseous refrigerant can be overheated before entering the compressor as far as in the compressor space of the hermetically sealed compressor. Lit. (2)
• the power field enhances the heat transfer 2.3 times in a situation when the boiling of the refrigerant has not developed, and 20 times when the bubble boiling has developed. Lit. (3)
• the heat pump in the embodiment according to the invention is based on the prior art, where an evaporator, a compressor in a hermetically sealed casing, a condenser and an expansion device are connected to the refrigerant circuit, and on below-described modifications and changes constituting the invention.
• the invention is characterized in that:before entering the hermetic casing of the compressor, the sucked-in refrigerant in the state of aerosol is undercooled by 1 to 3°Cbelow the level of the evaporation temperature of the refrigerant before the evaporator.
• the cooling of gas and the formation of aerosol occurs due to the conversion of the liquid fraction of the refrigerant injected into the overheated gas behind the evaporator into the gaseous fraction, whereit needs heat for its evaporation, which is taken from the gas.
• the gaseous refrigerant Before being sucked into the compressor casing, the gaseous refrigerant thus becomes aerosol, i.e. the gas with a certain proportion of small droplets.
• the heat present here is intensely transferred to the refrigerant. Small droplets gasify and the gas overheats to the required temperature before entering the compressor so that the drops of the refrigerant are removed from it.
• the casing of the compressor thus does not only fulfil the role of the overheater, but also becomes a heat exchanger with direct heat exchange, without dividing walls, where droplets of the refrigerant evaporate and then slightly overheat before being sucked into the compressor.
• the reduction of its volume also occurs, and as a side effect, the evaporating temperature of the refrigerant before the evaporator increases. This allows the increased supply of the refrigerant to the suction tract of the heat pump and drawing ina greater mass quantity of the refrigerant by the compressor.
• a bypass of the evaporator which consists of: a distributor of the flow of the refrigerant behind expansion device I;expansion device II, which is connected to expansion device I in series; a mixing device for the flows of the refrigerant behind the evaporator; and the connecting pipelines.
• the principle of lowering the temperature of the sucked-ingaseous refrigerant before entering the compressor casing is the same in the invention and in the prior art. Different is the method of embodiment.
• the prior art uses parallel (side by side) connection of the expansion device.
• the lowering of the temperature of the refrigerant as late as in the compressor uses parallel (side by side) arrangement of the expansion device.
• the arrangement according to the invention uses the connection of the expansion " devices in series (in a row), where expansion device II is part of the bypass of the evaporator.
• compressors of various designs and constructions can be used. According to the method of compressing the vapours, at least 9 types of compressors exist, which may be open (gland), semi- hermetic and hermetic. For heat pumps according to the invention, it is possible to use any compressor for cooling with an electric drive in a hermetically sealed casing, or in a semi-hermetic - split casing.
• the heat pump modified according to the invention a compressor of the same power is used as with the heat pump without modification.
• the heat pump according to the invention it is necessary that the heat pump according to the invention be equipped with the same device for starting and the device for drawing the refrigerant from the suction lines before the shutdown of the compressor - in the same way as the heat pump without modifications according to the invention.
• a heating cable for preheating the oil filling before the start to prevent foaming of the oil.
• the heating cable it is necessary that its temperature sensor be placed at the bottom of the compressor and on the opposite side of the orifice of the installed suction line into the casing.
• thermal insulation of the compressor casing it is possible to use thermal insulation of the compressor casing. However, this would be unsuitable if the compressor works in a warmer environment than its operating temperature on the surface.
• the invention is also applicable for a heat pump equipped with the EVI scroll compressor, which utilizes residual (specific) heat in the liquid refrigerant. In this case the bypass has to be used for the main evaporator, not for the additional exchanger with internal heat exchange.
• an adjusted piston compressor can be also used for the system using the residual heat in the liquid refrigerant. In this case, however, a perfect device must be used for separating droplets of the refrigerant from gas.
• Evaporator Commonly used for heat pumps, i.e. dry, gradually flooded.
• the adjustment for the heat pump modified according to the invention with a predicted increase ofoutput by about 50% does not require enlarging the heat exchange surface of the evaporator.
• Heat pump without the adjustment 1 kW/2 400 cm 2 .
• the heat pump according to the invention where we predict output increase by about 50%, i.e. to 1.5 kW; the condenser must be also enlarged by 50%, i.e. to 3 600 cm 2 .
• the refrigerant circuit consists of the suction part (from the expansion device to the compressor) and of the discharge part (from the compressor to the expansion device).
• the refrigerant circuit is filled with refrigerant.
• the refrigerant is a substance with very low evaporation temperature (-10 to -50°C), and as a gas it easily liquefies.
• Refrigerants are designated by the letter "R" and a number or a letter, which reflects the chemical composition of the refrigerant.
• the same refrigerant is used for the heat pump according to the invention and the heat pump without applying the invention.
• the heat pump according to the invention requires a greater amount of refrigerant, about 25% more that in the case of a conventional heat pump.
• the distributor on the bypass of the evaporator.
• the distributor is placed directly behind expansion device I, i.e. in front of the evaporator or before the distributor of the refrigerant to individual sections of the evaporator.
• the distributor on the bypass of the evaporator must ensure that liquid refrigerant come to expansion device II from the distributor. It is designed according to the known principle of a separator of droplets from gas, where the liquid is discharged through the bottom, and the top part serves for drawing off the aerosol with a predominance of droplets to the evaporator.
• the distributor can be in different designs. For example with a straight flow of refrigerant, with a rotary flow of refrigerant, as a vortex tube ( anque), etc.
• the refrigerant injected by expansion device I coming to the distributor must have a higher velocity of the flow than it has in the suction line, so that the fluid does not change the direction and settle in the pipeline before expansion device II.
• the inside diameter of the inlet tube must be smaller by 50% than that of the suction line, and the inlet tube must end above the bottom of the distributor.
• the inside diameter of the distributor shell must be 2 - 3times greater than that of the suction lineat the length of the shell 3 times greater than its inside diameter. The said values have a relatively great tolerance.
• the mixer is designed as a small container with an inlet and outlet of the suction line through its top.
• the connecting tube from expansion device II has an inlet to the bottom.
• the mixer may be also designed in another way, e.g. by a simple "T"shaped piece of the same dimension as the suction line. If TEV I is used as expansion device I, the mixer must be placed behind the evaporator and the temperature sensor (sensing bulb) of expansion valve I.
• TEV thermostatic expansion valve
• EEV electronic expansion valve
• AEV automatic expansion valve
• TEV On the bypass, there may by a TEV, an EEV, an AEV, a capillary, a
• TEV manually adjustable throttle valve or a nozzle.
• TEV II is used with internal pressure equalization.
• the TEV II sensing bulb is placed before the compressor.
• expansion device I or rather its dimensions, is the same both for the heat pump modified according to the invention and the unmodified heat pump. It must ensure overheating of the refrigerant above the evaporation temperature of the refrigerant before the evaporator by 3 - 5°C at the end of the evaporator.
• Nozzle sizes of TEV I and TEV II are the same. However, if a capillary is used instead of TEV I, it must be greater for the heat pump according to the invention than the capillary on the heat pump without the adjustments according to the invention.
• the adjustment of expansion device II, or rather its dimensions, must ensure undercooling of the refrigerant before entering the compressor casing by 1 to 3°C compared to the evaporating temperature of the refrigerant at the beginning of the evaporator.
• the temperature of oil in the compressor casing should not fall below +10°C. Lower temperature indicates that too large an amount of the liquid fraction of the refrigerant is sucked into the compressor casing, which decreases the output of the heat pump and COP.
• Fig. 1 shows a basic diagram of the heat pump.
• Fig. 2 shows a diagram of the heat pump with 2 expansion devices connected in series, including the bypass of the evaporator, which is the subject of the invention.
• the heat pump according to Fig. 1 consists of refrigerant circuit 1, to which evaporator 2, compressor 3, condenser 4 and expansion device 5 are connected.
• Number 7 marks the cooled medium, from which heat is removed, and number 8the heated medium, which is heated through the heat pump.
• FIG. 2 represents the known embodiment according to Fig. 1 extended by bypass 6 of evaporator 2 by connecting the suction line of refrigerant circuit 1 before and after evaporator 2.
• Bypass 6 consists of distributor 6 of the flow of the refrigerant behind expansion device I expansion device II 62, mixer 6 ⁇ of the flows of the refrigerant behind evaporator 2 and connecting pipeline6.3; a compressorin a hermetically sealed casing has to be used.
• expansion device II 6 ⁇ 2 that ensures the suction of such an amount of refrigerant that creates aerosol and lowers the temperature of the refrigerant in the suction line of refrigerant circuit I before entering casing 3J_ of hermetically sealed compressor 3 to the level lower than the evaporation temperature of the refrigerant at the beginning of evaporator 2, by which the volume of the sucked-in refrigerant is reduced and at the same time the evaporating temperature of the refrigerant increases before evaporator 2.
• This enables the drawing in of a larger mass quantity of the refrigerant by compressor 3, and as a result, this causes a significant increase of the coefficient of performance and the output of the heat pump at a slight increase of the input of electric power to compressor 3.
• the invention is applicable to all designs of heat pumps using compressor 3 with an electric motor enclosed in hermetic or semi-hermetic split casing 3.1.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Compressor (AREA)
• Heat-Pump Type And Storage Water Heaters (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (3)

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• 2015
  • 2015-09-24 CZ CZ2015-660A patent/CZ306309B6/cs not_active IP Right Cessation
• 2016
  • 2016-08-10 EP EP16757339.3A patent/EP3353477A1/en not_active Ceased

Patent Citations (3)

Non-Patent Citations (1)

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