EP2877792A1 - Appareil comprenant une pompe à chaleur - Google Patents

Appareil comprenant une pompe à chaleur

Info

Publication number
EP2877792A1
EP2877792A1 EP13740225.1A EP13740225A EP2877792A1 EP 2877792 A1 EP2877792 A1 EP 2877792A1 EP 13740225 A EP13740225 A EP 13740225A EP 2877792 A1 EP2877792 A1 EP 2877792A1
Authority
EP
European Patent Office
Prior art keywords
refrigerant
compressor
piping
pressure
narrow
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Withdrawn
Application number
EP13740225.1A
Other languages
German (de)
English (en)
Inventor
Francesco Cavarretta
Maurizio Ugel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Electrolux Home Products Corp NV
Original Assignee
Electrolux Home Products Corp NV
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Electrolux Home Products Corp NV filed Critical Electrolux Home Products Corp NV
Priority to EP13740225.1A priority Critical patent/EP2877792A1/fr
Publication of EP2877792A1 publication Critical patent/EP2877792A1/fr
Withdrawn legal-status Critical Current

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
    • F25B1/00—Compression machines, plants or systems with non-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
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • 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
    • F25B31/00—Compressor arrangements
    • 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
    • F25B31/00—Compressor arrangements
    • F25B31/002—Lubrication
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D21/0001—Recuperative heat exchangers
    • F28D21/0014—Recuperative heat exchangers the heat being recuperated from waste air or from vapors
    • 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
    • F25B2500/16—Lubrication

Definitions

  • Appliance including a heat pump
  • the invention relates to an appliance and in particular to an appliance having a heat pump system.
  • Laundry dryers usually comprise a drying chamber arranged for containing items to be dried, a blower for circulating hot air and feeding hot air into the drying chamber, and a heating system for heating air to be fed into the drying chamber for drying the items contained therein.
  • Heat pump technology has been recently applied to laundry dryers in order to enhance the efficiency in drying clothes. More generally, heat pumps have been applied nowadays to a plurality of different appliances, such as dish washers, washing machines, washer-dryers and tumble dryers, to enhance the efficiency of their functioning .
  • the heating system comprises a refrigerant circuit in which humid hot air coming from the drum is fed so that, by means of a refrigerant fluid, the humidity contained in the hot air is made to condense and is therefore discharged, whilst hot dry air is again fed to the drum. More in detail, the air, moved by a fan, passes through the drum removing water from wet clothes, and then it is cooled down and dehumidified in a heat pump evaporator and heated up in a heat pump condenser to be re-inserted into the drum.
  • the refrigerating fluid is moved and compressed by a compressor.
  • a lubricant usually a lubrication oil, is provided in the compressor of the refrigerant circuit to promote the safe hydrodynamic lubrication inside the same.
  • the lubrication oil creates a thin film within the moving parts of the compressor, such as pistons, shaft, bearings, etc. thus reducing the wear of the moving parts due to the friction.
  • the lubricant oil can also contribute to cool the electric motor of the compressor. This effect is important mainly in semi-hermetic or hermetic compressors in which the heat exchange with the environment is very low.
  • Laundry dryers of the above mentioned type are known for example from EP 1405946.
  • the dryer described in European patent EP 1405946 comprises a drying chamber in which items to be dried are fed, and a rotary compressor that constitutes together with the evaporator, the expansion valve and the gas cooler connected in an annular shape a refrigerant circuit.
  • the rotary compressor is an internal middle pressure multistage compression type which uses C0 2 as a refrigerant.
  • the rotary compressor comprises a cylindrical airtight container, and a rotary compression mechanism section which is constituted of a first rotary compression element (first stage) and a second rotary compression element (second stage) driven by a rotary shaft.
  • the mechanical parts of the compressor are lubricated by oil fed form a reservoir by means of relevant holes to the suitable part of the compressor.
  • the moisture contained in the air coming from the drying chamber is condensed to be discharged by the evaporator.
  • the heat pump of known appliances includes a refrigerant circuit in which a refrigerant can flow and which connects via piping a first heat exchanger or condenser, a second heat exchanger or evaporator, a compressor and a pressure- lowering device.
  • the refrigerant is pressurized and circulated through the system by the compressor.
  • the hot and highly pressurized vapor is cooled in the condenser, until it condenses into a high pressure, moderate temperature liquid .
  • the condensed refrigerant then passes through the pressure-lowering device such as an expansion device, e.g. a choke, a valve or a capillary tube.
  • the low pressure liquid refrigerant then enters the evaporator, in which the fluid absorbs heat and evaporates.
  • the refrigerant then returns to the compressor and the cycle is repeated .
  • some lubricant may flow from the compressor into the refrigerant circuit together with the refrigerant fluid and mix with the latter.
  • the lubricant oil and the refrigerant can be mutually completely miscible so that the liquid phase has only one phase and a homogeneous solution is formed between the two fluids; or the two fluids can be partially miscible so that in some proportion, they do not form a solution, but two separate liquid phases with different composition are formed at defined pressure and temperature levels.
  • the solubility increases with the pressure and decreases with the temperature level and most commonly at the outlet of the compressor they form a solution.
  • the lubricant oil and the refrigerant may be completely immiscible, in this case two different liquid phases are formed at any temperature, pressure and composition.
  • refrigerant and lubricant are partly miscible in most of the cases (i.e. about 90% of the refrigerants and lubricants are partially miscible), and therefore in the following only the second and third possibilities are considered, the first one of complete miscibility being not relevant for the present invention.
  • a consequence of the partial miscibility (or immiscibility) of the lubricant oil and the refrigerant is that along the refrigerant circuit the two fluids may separate and the fluid flowing in the pipes can be a mixture of refrigerant and some amount of lubricant in form of droplets.
  • the lubricant oil and the refrigerant may reciprocally separate in any position of the heating pump circuit, due, for example, to different operative conditions (temperature, pressure) that change the reciprocal miscibility of the two fluids. More in detail, for certain thermodynamic conditions, the refrigerant is not able to transport the separated lubricant back to the compressor, i.e. for example the refrigerant is not flowing fast enough to detach the lubricant from the piping wall and bring it back to the compressor.
  • oil traps may be formed, and in particular the trapping can take place in any position of the refrigerant circuit.
  • the presence of the lubricant oil trapped in the heat exchangers and in the pipes of the refrigerant circuit can affect the efficiency of the system, i.e. it hinders the heat exchange between the process medium and the refrigerant.
  • an object of the invention is to provide an appliance with heat pump that overcome the drawbacks of known appliances with heat pump.
  • a further object of the invention is to provide an appliance with heat pump having a simple structure and in which at the same time good thermal efficiency is assured and maintained over time.
  • a still further object of the invention is to provide an appliance in which the formation of oil traps is diminished or avoided .
  • the appliance of the invention includes a dryer, a washer-dryer, a washing machine, or a dish washer, where a process medium such as air or water is warmed up by the first heat exchanger, i.e. the condenser, and this process medium is then used also in a treating chamber.
  • the treating chamber can be the drum of the dryer or the tub of the washing machine or washer-dryer, for example.
  • the heated process medium is used for example to wash or dry goods such as laundry or dishes.
  • an appliance including :
  • a heat pump having a refrigerant circuit in which a refrigerant can flow, said refrigerant circuit including a first heat exchanger where the refrigerant is cooled off and said process medium is warmed up, a second heat exchanger where the refrigerant is heated up, a compressor to pressurize and circulate the refrigerant through the refrigerant circuit, said compressor including a lubricant, and a pressure-lowering device; said first and second heat exchanger, compressor and pressure-lowering device being operatively connected through refrigerant circuit piping into which said refrigerant is apt to flow;
  • the refrigerant circuit piping comprises at least one narrow piping portion having a narrow hydraulic diameter, and the ratio between the narrow hydraulic diameter and the hydraulic diameter of the remaining piping portions of the refrigerant circuit piping is comprised between 0.4 and 0.95; said at least one narrow piping portion being located :
  • the at least one narrow piping portion may be located alternatively or in combination in the above listed location.
  • the hydraulic diameter D H of the piping is defined as: where A is the cross sectional area of the piping and P is the wetted perimeter of the cross-section of the piping .
  • the hydraulic diameter of the narrow portion D Hn arrow is 40% D H ⁇ D H narrow ⁇ 95% D H , preferably D Hn arrow is 40% D H ⁇ D Hn arrow ⁇ 90% D H a and more preferably D Hn arrow is 55% D H ⁇ D Hn arrow ⁇ 80% D H .
  • the narrow piping portion may have an hydraulic diameter comprised between 4 mm and 10 mm.
  • the shape of the cross section of the piping and its narrow portion(s) is not relevant for the present invention, and it can be squared, rectangular, circular (in this case the hydraulic diameter coincides with the internal diameter of the circle), elliptic, and so on .
  • the piping are made of metal, more preferably aluminum.
  • the velocity of the fluid flowing in the piping is locally increased, i.e. within the narrow portion the velocity of the fluid is higher than in the rest of the refrigerant circuit.
  • the refrigerant fluid By increasing the velocity of the fluid (refrigerant fluid and possible lubricant oil), the refrigerant fluid will more easily drag the lubricant oil . Therefore, at the narrow piping portion, the formation of oil traps is reduced .
  • the narrow piping portion(s) is(are) located in positions of the refrigerant piping in which oil trapping is more probable to occur.
  • the narrow piping portion is placed in one or more of the above locations. More than a single narrow portion may be also provided in the appliance of the invention .
  • fluid in the following a homogeneous solution of refrigerating fluid and lubricant oil, or a biphasic mixture of refrigerating fluid and lubricant oil, depending on the miscibility of the lubricant oil and the refrigerant fluid shall be comprised .
  • the fluid flow rate in the piping of the heat pump system depends on the displacement, the volumetric efficiency and the RPM of the compressor, and the temperature and the pressure level of the refrigerant at the compressor suction .
  • the velocity of the fluid in the piping varies along the piping according to the actual internal section of the piping and the actual density of the fluid :
  • m is the fluid flow rate
  • p is the refrigerant density
  • v is the refrigerant velocity
  • A is the piping section
  • D the hydraulic diameter of the piping, as already stated for a round piping the hydraulic diameter corresponds to the internal diameter of the piping .
  • the fluid velocity decreases in case of high density levels.
  • the density is proportional to the pressure and inversely proportional to the temperature of the fluid .
  • the pressure is relatively rather high and the temperature is relatively rather low. This gives, due to the above explained formula, a rather high density of the refrigerant, and consequently a low velocity of the same. For this reason in this portion of the refrigerant circuit oil trapping is rather probable. In particular this branch of the refrigerant circuit is the one with the highest probability of oil trapping.
  • the compressor is responsible of the circulation of the refrigerant circuit within the circuit itself and includes the inlet for the suction of the refrigerant fluid which is then compressed and exhausted by the output.
  • a portion of the refrigerant circuit i.e. some piping, is located at a vertical level which is lower than or equal to the vertical level defined by the location of the suction inlet of the compressor, the refrigerant cannot flow into the compressor by the simple application of gravity, on the contrary a force against gravity has to be exerted in order to transport the fluid inside the compressor.
  • the refrigerant fluid In these portions of the circuit located below or at the inlet vertical level, the refrigerant fluid has to flow faster than in other circuit's portions to avoid oil trapping, because oil trapping is more likely to occur, the lubricant cannot go back by gravity to the compressor.
  • a vertical level lower than mean the following : in the normal functioning of an apparatus, a vertical axis Z and also a (X,Y) plane perpendicular to the vertical axis which is the "ground" are defined.
  • the suction inlet for suction of the refrigerant in the compressor is located, when mounted in the dryer, at a given height along the Z axis and it is substantially the entrance to the compressor chamber from which the inlet pipe extends.
  • the presence of at least one narrow portion having a smaller hydraulic diameter than the remaining portions of the piping reduces the oil trapping as soon as it is formed and increases the dragging of lubricant oil by the refrigerant fluid.
  • the length of the narrow portion if a single portion is present is meant, otherwise it indicates the total length as a sum of the single lengths of the various narrow portion, in case more than a narrow portion is present in the refrigerant piping of the invention.
  • the hydraulic diameter of the narrow portion is so chosen that a velocity of the fluid > 1 m/s is obtained in the latter.
  • the refrigerant is able to drag the lubricant oil back to the compressor.
  • the hydraul ic d iameter of the piping in the remaining portions of the refrigerant circu it piping is ma intained substantially constant and having a larger diameter than the narrow piping portions, so that the overall pressure drops are limited .
  • the hydrau lic d iameter of the piping in the remaining portions of the refrigerant piping circuit is preferably kept "high" in order to l imit the pressure drops within the refrigerant circu it.
  • the refrigerant circu it can be functional ly divided in two portions, a high pressure portion which is the portion of the refrigerant circu it connecting the compressor to the pressure lowering device via the condenser, and a low pressure portion which is the portion of the circu it connecting the pressure-lowering device back to the compressor via the evaporator.
  • the term "high” and “low” are relative terms and their meaning is that the pressure of the refrigerant in the "high pressure” portion is higher than in the "low pressure” portion .
  • the pressure-lowering device in the appl iance of the invention includes compensating means to compensate the pressure drop due to the narrow piping portions.
  • the pressure-lowering device includes a valve or a capillary wh ich so d imensioned that the pressure drop between low and hig h pressure portions of the refrigerant circuit in the appl iance of the invention is substantially the same as the pressure d rop present in a refrigerant circuit without the narrow piping portion, in particular the pressure d rop calculated is the one between the outlet of the condenser and the in let of the evaporator. Therefore, the pressure- lowering device in the appliance of the invention yields a lower pressure drop than in the case without narrow piping portion.
  • the expansion of the fluid in the pressure-lowering device may be suitably changed in order to obtain at the output a desired pressure level for the refrigerant.
  • the capillary is either shorter or has a wider diameter than in an heat pump without the narrow piping portion.
  • the refrigerant circuit may not include only the components already described, i.e. the compressor, the heat exchangers and the expansion devices, but can also include additional components, such as additional condenser(s) which is preferably located between the condenser and the expansion device, and/or additional evaporator(s), and/or gas liquid separator located downstream the inlet of the compressor in order to avoid the entrance of liquid into the compressor itself.
  • the apparatus of the invention includes an auxiliary first heat exchanger, in other words an auxiliary condenser, located between the outlet of the main condenser and the pressure-lowering device. More preferably, the secondary condenser is located below the suction inlet vertical level defined by the inlet of the compressor.
  • the apparatus of the inventor also includes an auxiliary second heat exchanger, i.e. and auxiliary evaporator, located between the outlet of the main evaporator and the inlet of the compressor. Preferably, this auxiliary evaporator is also located below the suction inlet level defined by the compressor.
  • the heat pump may also include a fan to cool off the compressor to avoid overheating during the functioning of the latter.
  • the heat pump also includes an internal heat exchanger, apt to perform a heat exchange between the high pressure portion and the low pressure portion of the refrigerant circuit.
  • the internal heat exchanger includes a first piping portion of the low pressure portion and a second piping portion of the high pressure portion of the refrigerant circuit, which are brought at a given distance which allows heat exchange between the two piping portions.
  • the first piping portion is located between the outlet of the evaporator and the inlet of the compressor, while the second portion is located between the outlet of the condenser and the inlet of the pressure-lowering device.
  • Figure 1 is a perspective view of a laundry dryer according to the invention, with a portion of the casing removed;
  • FIG. 2 is a perspective view of an internal portion of the laundry dryer of Figure 1 in a disassembled condition
  • Figure 3 is a schematic representation of the process air circuit and of the refrigerant circuit of the dryer of Figures 1 and 2;
  • Figure 4 is a schematic representation of a different embodiment of the process air circuit and of the refrigerant circuit of the dryer of Figures 1 and 2;
  • Figures 5a and 5b a schematic front and lateral view, in section, respectively, of the dryer of Figure 1;
  • Figures 6a and 6b are a schematic front and lateral view, in section, respectively, of the dryer of Figures 1 and 4;
  • Figure 7 is a graph depicting the behaviour of the refrigerant temperature versus time in different portions of the refrigerant circuit
  • Figure 8 is a graph depicting the behaviour of the refrigerant pressure versus time in different portions of the refrigerant circuit
  • Figs. 9a and 9b are two schematic lateral views of a detail of the refrigerant circuit of the dryer of fig. 1 according to two different embodiments of the invention.
  • an appliance realized according to the present invention is globally indicated with 1.
  • a laundry dryer As a possible appliance, a laundry dryer is described herein below, however the invention can be generalized to any appliance including an heat pump in which the first heat exchanger warms up a process medium, such as a dish-washer, washing machine, washer dryers and dryers in general.
  • a treating chamber is included, where the heated process medium, such as air or water, is introduced, for example to wash clothes/dishes or to dry the same.
  • downstream a position with reference to the direction of the flow of a fluid inside a conduit is indicated.
  • Laundry dryer 1 comprises an outer box casing 2, preferably but not necessarily parallelepiped-shaped, and a drying chamber 3 in which items to be dried, usually clothes or other garments are loaded.
  • the drying chamber comprises a drum 3 having the shape of a hollow cylinder that is rotatably fixed to the casing 2 and an electrical motor arranged for operating the drum 3 for rotating the latter about a rotation axis.
  • the drum 3 is rotatable about a horizontal rotation axis, nevertheless in alternative embodiments of the dryer of the invention, not shown in the Figures, the drum may rotate about a vertical axis or an axis tilted in relation to the horizontal axis.
  • a door 3a is provided that is hinged to the casing 2 in order to be opened/closed for accessing the drum 3 the door 3a is so configured to hermetically closing the drum 3 so that safe functioning of the dryer 1 is assured .
  • casing 2 generally includes a front panel 20, a rear wall panel 21 and two sidewall panel all mounted on a basement 24.
  • Panels 20, 21 and basement 24 can be of any suitable material.
  • the basement 24 is realized in plastic material.
  • basement 24 is molded .
  • basement 24 includes an upper and a lower shell 24a, 24b (visible in figure 2) -
  • the laundry dryer 1 further comprises a fan or a blower 4 or a suitable moving device arranged for moving air inside the laundry drier 1 along an air process conduit 5, through which flows air to be used for drying the items contained in the drum 3, as better disclosed in the following.
  • the dryer 1 of the invention additionally comprises a heat pump 6 including a first heat exchanger called also condenser 61 and a second heat exchanger called also evaporator 62.
  • Heat pump 6 also includes a refrigerant closed circuit 60 (schematically depicted in the picture with arrows connecting the first to the second heat exchanger and vice versa, see in detail figs. 3-5) in which a refrigerant fluid flows, when the dryer 1 is in operation, cools off and may condense in correspondence of the condenser 61, releasing heat, and evaporates, potentially even warms up, in correspondence of the second heat exchanger (evaporator) 62, absorbing heat.
  • a refrigerant closed circuit 60 (schematically depicted in the picture with arrows connecting the first to the second heat exchanger and vice versa, see in detail figs. 3-5) in which a refrigerant fluid flows, when the dryer 1 is in operation, cools off and may condense in correspondence of the condenser
  • the refrigerant circuit 60 connects through piping 65 the evaporator 62 via a compressor 63 to the condenser 61.
  • the cooled or condensed refrigerant arrives via a pressure lowering device, such as an expansion device 64, for example a choke, or a valve or a capillary tube, back at the evaporator 62.
  • the compressor 63 preferably a single-stage or multi-stage sealed compressor, preferably including a variable speed motor, includes an inlet 63a, called also suction inlet for the suction of the refrigerant, and an outlet 63b for the exhaustion of the refrigerant.
  • a lubricant reservoir (not shown) is present, in order to provide lubricant for the lubrication of the moving parts of the compressor itself. Such a lubricant may leak within the refrigerant circuit, i.e. it can be present within piping 65.
  • the inlet 63a is located at a "suction inlet level" L (see figs.
  • Compressor 63 includes a container 63e in which a top and a bottom 63c and 63d, respectively, are defined and which encloses a compressor chamber and a lubricant chamber (both not shown in the appended drawings).
  • the suction inlet 63a defines the suction inlet plane L depicted as a dash-dotted line in the drawings and its positioning is independent from the location of the compressor's bottom 63d.
  • the compressor 63 may also include a liquid-vapor separator 37, to avoid entrance of liquid in the compressor chamber of the casing 63e.
  • Compressor 63 and liquid-vapor separator 37 are connected via piping 63f. It is to be understood that the suction inlet 63a defining the suction inlet plane L is always the suction inlet 63a of the compressor 63, and not the inlet 37a of separator 37. In the depicted embodiment, a portion of the piping 63f connecting separator 37 and compressor 63 is located below the suction inlet level L. Moreover, also in the compressor of fig . 9a without separator 37, the inlet pipe 63g connecting the suction inlet 63a to the refrigerant circuit 60 is located below the suction inlet level L.
  • the condenser 61 and the evaporator 62 of the heat pump 6 are located in correspondence of the process air conduit 5.
  • the dryer 1 of the invention can be a condense dryer - as depicted in the figures - where the air process conduit 5 is a closed loop circuit, and the condenser 61 is located downstream of the evaporator 62.
  • the air exiting the drum 3 enters the conduit 5 and reaches the evaporator 62 which cools down and dehumidifies the process air.
  • the dry cool process air continues to flow through the conduit 5 till it enters the condenser 61, where it is warmed up before re-entering the drum 3.
  • the dryer of the invention can also be a vented dryer, not shown, in which the process air conduit 5 includes an exhaust duct connected to the drum 3 via an aperture into which the process air enters after having passed the whole drum 3 to de-humidify the laundry.
  • First and/or second heat exchanger 61, 62 further preferably includes one or more heat exchanger modules 10 (shown only in fig . 2) located along the process air conduit 5, more preferably in correspondence of the basement 24 of dryer 1, as shown in fig 2 where the casing 2 and the drum 3 of the dryer 1 have been removed in order to show the heat exchangers located along the process air conduit 5.
  • one or more heat exchanger modules 10 shown only in fig . 2 located along the process air conduit 5, more preferably in correspondence of the basement 24 of dryer 1, as shown in fig 2 where the casing 2 and the drum 3 of the dryer 1 have been removed in order to show the heat exchangers located along the process air conduit 5.
  • the refrigerant circuit 60 may also include an auxiliary condenser 36 to improve the drying performances (efficiency and/or drying time) for example located downstream the condenser 31 and/or, an auxiliary evaporator (not shown in the drawings) and/or, as already described and shown in figs. 9a, 9b and fig. 2, the liquid-vapor separator 37 upstream the compressor 63.
  • the auxiliary condenser is used to further lower the temperature of the refrigerant, while the auxiliary evaporator to further increase the temperature of the refrigerant.
  • the air process circuit 5 is a closed loop circuit. As previously discussed, the refrigerant fluid flows in the piping 65 together with some lubricant coming from the compressor 63. The lubricant can be mixed to the refrigerant or form droplets in the latter.
  • lubricant and the refrigerant are partially miscible so that, depending on the thermodynamic conditions, they may form a solution or two separate liquid phases.
  • the mutual solubility between lubricant oil and refrigerant fluid changes by changing the pressure and/or temperature conditions.
  • the oil present in the refrigerant fluid may be trapped in the circuit itself affecting the thermal efficiency of the heat pump system 6.
  • Applicants have found that by monitoring - using suitable sensor(s) - the behavior of the temperature and/or the pressure of the refrigerant in preset zones of the refrigerant circuit, the oil trapping becomes visible due to the above mentioned unstable behavior of the pressure and/or temperature curve versus time. Therefore, analyzing the temperature and/or pressure fluctuations during the drying cycle, it is possible to easily detect the presence (or absence) of oil trapping in the circuit.
  • Figure 7 is a graph depicting the behaviour of the refrigerant temperature versus time in different portions of the refrigerant piping 65 during the drying cycle.
  • the upper most curve 80 shows the behavior of the temperature values of the refrigerant in the proximity of the compressor outlet 63b during the drying cycle.
  • the second curve 81 from above shows the behavior of the temperature values of the refrigerant between the condenser 61 outlet and the pressure lowering device 64, during the drying cycle.
  • the third curve 82 from above and the lowest curve 83 show the behavior of the temperature values of the refrigerant in the proximity of the compressor inlet 63a and evaporator inlet, respectively, during the drying cycle.
  • the unstable behavior above analyzed is a sign of oil trapping .
  • Figure 8 is a graph depicting the behaviour of the refrigerant pressure versus time in different portions of the refrigerant circuit, a curve 90 is obtained with the values of the pressure upstream of the expansion device 64, while curve 91 is obtained at the outlet of the expansion device 64; in other words the two measurements are taken in the high and low pressure portions of the refrigerant circuit.
  • Pressure measurements, and not temperature measurements can be made also downstream the outlet of the compressor 63. At the outlet, refrigerant and lubricant are mixed and temperature measurements will not show instability (see curve 80 of figure 7), however the pressure "waves" due to the unstable behavior caused by oil trapping are easily detected in a pressure graph.
  • the refrigerant fluid piping 65 comprises at least one narrow piping portion 70 having a hydraulic diameter D Hn arrow which is, with respect to the hydraulic diameter D H of the remaining portions of the refrigerant fluid piping 65 within the following ranges: 40% D H ⁇ D Hn arrow ⁇ 95% D H , preferably 40% D H ⁇ D H narrow ⁇ 90% D H and more preferably D Hn arrow is 55% D H ⁇ D Hn arrow ⁇ 80% D H .
  • the narrow piping portion 70 is provided in a third branch 68 of the piping 65, arranged upstream the inlet 63a of compressor 63, i.e. between the outlet of evaporator 62 and the inlet of compressor 63, as depicted in fig . 3.
  • the narrow piping portion 70 is provided in a first branch 66 of the piping 65, i.e. between the outlet of the condenser 61 and the expansion device 64, as depicted in fig. 4.
  • the narrow piping portion 70 is provided in a second branch 67 of the piping 65, i.e. between the outlet of the pressure lowering device 64 and the inlet of the evaporator 62.
  • the narrow piping portion 70 may be located in any branch of the piping 65 arranged below the inlet pipe level 63a of the compressor 63, for example in the lower portion 65c shown in Figures 6a and 6b.
  • the portion 65c indeed corresponds to a portion of the piping 65 of the heat pump system 6 which is located below the suction inlet level L.
  • This portion can be present due to the specific construction of the heat pump system 6 which is constrained by the limited space available, or to the presence of the additional condenser 36.
  • more than one narrow piping portion 70 may be provided in the piping 65.
  • the velocity of the fluid flowing in the piping 65 is increased thus it is increased the dragging of the oil by the refrigerant and the formation of the oil traps is minimized .
  • the pressure lowering device is configured in such a way to compensate for the pressure drop caused by the narrow piping .
  • the pressure drop between the high pressure portion of the circuit downstream the condenser, but upstream of the narrow piping portion, and the inlet of the evaporator in the low pressure portion of the circuit is substantially the same that the pressure drop calculated between the same positions in a circuit without the narrow piping portion(s).
  • the laundry to be dried is positioned into the drum 3 and the door 3a is then closed.
  • the laundry dryer 1 is then operated, the motor rotates the drum 3 and the blower 4 feed hot air into the drum 3 for drying the items therein provided .
  • the hot air blown into the drum 3 warms the items to be dried to evaporate moisture.
  • the moisture- containing process air which has dried the items flows first through the drum 3, then through the air process conduit 5 and through the condenser 61, and the evaporator 62.
  • the refrigerating fluid for example, carbon dioxide, flows in the refrigerating fluid piping 65 through the condenser 61 and the evaporator 62 in the opposite directions in relation to the air.
  • the temperature difference between the air and the refrigerating fluid allows an efficient heat exchange between the air and the refrigerating fluid .
  • the refrigerating fluid undergoes a phase transition from the liquid to the vapor phase due to the heat exchange with the warm process air exiting the drying chamber at the evaporator 62.
  • the evaporated refrigerant is then supplied by means of the compressor 63 to the condenser 61, in which the refrigerant condenses again, heating up the process air before the latter is introduced into the drum 3.
  • the condensed refrigerant arrives at the pressure lowering device 64 and thus flows back to the evaporator 62 closing the circuit.
  • the refrigerant fluid is moved by the compressor 63, from which some oil can come out into the refrigerant circuit 60 and droplet of oil may thus be formed in the refrigerating piping 65.
  • the oil can also be trapped into the piping.
  • the presence of one or more narrowing sections 70 in the refrigerating piping 65 allows the detachment of the oil droplets from the piping's walls, removing the oil trapping, and the oil can be dragged to the compressor again.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Detail Structures Of Washing Machines And Dryers (AREA)
  • Compressor (AREA)

Abstract

L'invention porte sur un appareil (1), comprenant une chambre de traitement (3) dans laquelle est introduit un milieu de traitement ; une pompe à chaleur (6) ayant un circuit de fluide frigorigène (68) dans lequel peut s'écouler un fluide frigorigène, le circuit de fluide frigorigène comprenant un premier échangeur de chaleur (61) dans lequel le fluide frigorigène est refroidi et ledit milieu de traitement est chauffé, un second échangeur de chaleur (62) dans lequel le fluide frigorigène est chauffé, un compresseur (63) servant à mettre sous pression et faire circuler le fluide frigorigène dans le circuit de fluide frigorigène, le compresseur comprenant un lubrifiant et un dispositif de réduction de pression (64). Les premier et second échangeurs de chaleur, le compresseur et le dispositif de réduction de la pression sont raccordés de façon fonctionnelle au moyen d'une tuyauterie de circuit de fluide frigorigène (65) dans laquelle peut s'écouler le fluide frigorigène. La tuyauterie de circuit de fluide frigorigène (65) comprend au moins une partie de tuyauterie étroite ayant un diamètre hydraulique étroit (DHnarrow), et le rapport entre le diamètre hydraulique étroit (DHnarrow) et la chambre hydraulique (DH) des parties de tuyauterie restantes de la tuyauterie de circuit de fluide frigorigène (65) est compris entre 0,4 et 0,95. L'au moins une partie de tuyauterie étroite étant placée dans au moins un des emplacements suivants : entre une sortie du second échangeur de chaleur (62) et une entrée du compresseur (63a), entre une sortie du premier échangeur de chaleur (61) et une entrée du dispositif de réduction de pression (64), entre une sortie du dispositif de réduction de pression (64) et une entrée du second échangeur de chaleur (62), ou au-dessous ou au niveau du niveau d'entrée d'aspiration (L) du compresseur (63).
EP13740225.1A 2012-07-26 2013-07-12 Appareil comprenant une pompe à chaleur Withdrawn EP2877792A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP13740225.1A EP2877792A1 (fr) 2012-07-26 2013-07-12 Appareil comprenant une pompe à chaleur

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP12177962.3A EP2690379A1 (fr) 2012-07-26 2012-07-26 Appareil comprenant une pompe à chaleur
PCT/EP2013/064780 WO2014016140A1 (fr) 2012-07-26 2013-07-12 Appareil comprenant une pompe à chaleur
EP13740225.1A EP2877792A1 (fr) 2012-07-26 2013-07-12 Appareil comprenant une pompe à chaleur

Publications (1)

Publication Number Publication Date
EP2877792A1 true EP2877792A1 (fr) 2015-06-03

Family

ID=48874256

Family Applications (2)

Application Number Title Priority Date Filing Date
EP12177962.3A Withdrawn EP2690379A1 (fr) 2012-07-26 2012-07-26 Appareil comprenant une pompe à chaleur
EP13740225.1A Withdrawn EP2877792A1 (fr) 2012-07-26 2013-07-12 Appareil comprenant une pompe à chaleur

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP12177962.3A Withdrawn EP2690379A1 (fr) 2012-07-26 2012-07-26 Appareil comprenant une pompe à chaleur

Country Status (4)

Country Link
EP (2) EP2690379A1 (fr)
CN (1) CN104508398B (fr)
AU (1) AU2013295230A1 (fr)
WO (1) WO2014016140A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK3483529T3 (da) 2017-11-09 2020-12-07 Rivacold S R L Smøremiddelovervågningssystem til en kredsløbskompressor

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2023435A (en) * 1928-07-06 1935-12-10 Servel Inc Refrigeration
US2975613A (en) * 1959-01-23 1961-03-21 Gen Motors Corp Refrigerating apparatus with aspirator in a by-pass
US4800736A (en) * 1988-01-27 1989-01-31 Weber Russell L Heat pump
CN2180949Y (zh) * 1993-02-23 1994-10-26 王奇 多功能热泵干燥机
JP2002195677A (ja) * 2000-10-20 2002-07-10 Denso Corp ヒートポンプサイクル
JP2004141650A (ja) 2002-10-01 2004-05-20 Sanyo Electric Co Ltd 乾燥機
JP3825772B2 (ja) 2003-09-05 2006-09-27 三洋電機株式会社 乾燥機
DE102006062834B4 (de) * 2005-06-30 2016-07-14 Denso Corporation Ejektorkreislaufsystem

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2014016140A1 *

Also Published As

Publication number Publication date
CN104508398B (zh) 2017-11-21
CN104508398A (zh) 2015-04-08
EP2690379A1 (fr) 2014-01-29
AU2013295230A1 (en) 2015-01-29
WO2014016140A1 (fr) 2014-01-30

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