Refrigeration system and retro-fit system for refrigeration system

Abstract

A refrigeration system (1) comprising a compressor (2), a condenser (3), an lamination member (4), an evaporator (5), and a fluid power machine (6) fluidically connected between the lamination member (4) and the evaporator (5), in which a working fluid circulates in a closed circuit. The fluid power machine (6) comprises a motor chamber, a motor member movably housed in the motor chamber, an inlet for the injection of working fluid into the motor chamber to move the motor member, and an outlet for the discharge of working fluid from the motor chamber.

Description

"REFRIGERATION SYSTEM AND RETRO-FIT SYSTEM FOR REFRIGERATIONSYSTEM" DESCRIPTION

[0001] The present invention relates to a system that exploits the refrigeration cycle to achieve heat exchanges , such as for example a refrigeration system or a heat pump system.

[0002] The invention finds application in the field of thermal conditioning of a building , such as for example residential apartment buildings , industrial warehouses , hospitals and supermarkets . Moreover, the invention finds application in the field of refrigeration of a refrigeration cell of a refrigeration or freezer device , for example for food, chemical , textile and pharmaceutical applications .

[0003] The invention finds preferred application in the context of systems typically used to meet the needs of res idential comfort and to feed industrial transformation processes .

[0004] In the present discussion, in general and unless otherwise specified, the term "refrigeration system" indicates generically a system or a machine that absorbs energy to implement a series of reverse thermodynamic transformations , for the purpose of transferring heat from an environment at a lower temperature towards an environment at a higher temperature . The term "refrigeration system" indicates , for example , a refrigeration system properly so called, that is a thermal machine intended to remove heat from an environment ,or a heat pump system, that is a thermal machine intended to release heat to an environment .

[0005] For the purpose of classifying refrigeration systems properly so called, that is a machine for removing heat from an environment , in the field it is known to use criteria such as the evaporation temperature and the condensation mode . In general , with reference to evaporation temperatures , a system operating at temperatures lower than about -25 ° C is defined "low temperature" , for temperatures between -25 ° C and -5 ° C the system is defined "medium temperature" , and finally for temperatures higher than about -5 ° C the system is defined "high temperature" . In general , with reference to the mode and the temperatures of condensation, systems exploiting water condensation operate at temperatures indicatively between 25 ° C and 30 ° C, the systems exploiting evaporative tower condensation operate at temperatures indicatively between 35 ° C and 40 ° C , and, finally, the systems exploiting air condensation operate at temperatures indicatively between 30 ° C and 50 ° C .

[0006] In the prior art innumerable systems are known, specifically designed and made to meet the needs of users .

[0007] Innovation in the field is aimed at optimising the energy efficiency and the performance of the systems , in a context of increasing environmental awareness .

[0008] For these purposes , in the field it is known, forexample , to exploit pre-expansion systems upstream of the lamination and pre-compression member upstream of the compressor . It is also known to implement multistage compression systems comprising several independent compressors .

[0009] Although such developments lead to an increase in efficiency, the known solutions are particularly complex and expensive to implement and, depending on the type and structure of the system, important structural modifications to the system itself and invasive alterations to the thermodynamic cycle are required, with consequent drawbacks in terms of design, management and maintenance . Examples of refrigeration systems of the prior art that suffer from such problems are described in documents EP1830143A2 , US2006 / 266057A1 , US2017 / 174049A1 ( D3 ) , US2009 / 031738A1 and US9222706B2 .

[0010] Purpose of the present invention is to provide a refrigeration system that meets the needs of the field and remedies the problems mentioned with reference to the prior art .

[0011] This purpose is achieved by means of a refrigeration system and a retro-fit kit according to the independent claims . The dependent claims show preferred embodiments that involve further advantageous technical aspects .

[0012] The subj ect of the present invention is described belowin detail , with the aid of the accompanying drawings , in which :- Figures 1 and la respectively show a refrigeration diagram according to the prior art , and an enthalpy-pressure diagram for a refrigeration cycle according to the prior art ;- Figures 2 and 2a respectively show a refrigeration diagram, and an enthalpy-pressure diagram for a refrigeration cycle , in accordance with the present invention, according to a preferred embodiment ;- Figures 3 and 3a respectively show a refrigeration diagram, and an enthalpy-pressure diagram for a refrigeration cycle , in accordance with the present invention, according to a preferred embodiment that provides an economiser circuit ;- Figures 4 and 4a respectively show a refrigeration diagram, and an enthalpy-pressure diagram for a refrigeration cycle , in accordance with the present invention, according to a preferred embodiment chosen by way of example for the calculation of the main parameters of a refrigeration system according to the present invention;Figures 5 and 6 show calculation tables of the characteristic parameters of systems in accordance with the present invention, according to a preferred embodiment , respectively for a refrigeration system and a heat pump system .

[0013] With reference to the accompanying figures , thereference number 1 denotes a refrigeration system as a whole.

[0014] With reference to figures 1 and la, a refrigeration cycle according to the prior art provides for the entry of working fluid into the compressor A in a gaseous state at low temperature and pressure, for example at -35°C and 76 kPa (0.76 bar) (point 1) , and it is compressed to high pressure and temperature, up to a condensation pressure, implementing an irreversible adiabatic transformation, for example at +80°C and 1718 kPa (17.18 bar) (point 2) . The working fluid coming from the compressor A enters the condenser B, in which it releases to an external environment a quantity of heat Qout, bringing the compressed gaseous phase from the superheated gaseous state to the subcooled liquid state at high pressure (point 3) . The working fluid coming from the condenser B enters the lamination member C, for example a thermostatic valve, in which it expands and implements an isoenthalpic transformation, reducing the temperature and the pressure of the working fluid down to the evaporation pressure, for example down to 76 kPa (0.76 bar) and -45°C (point 4) , reaching a two-phase state, that is fluid consisting of a gaseous phase, also known as title of the vapour, at low density and at high speed, and a liquid phase at high density finely dispersed in the gaseous phase. The working fluid coming from the lamination member C enters the evaporator D, in which it absorbs a quantity of heat Qin from an externalenvironment , evaporating the liquid phase at low pressure of the working fluid, passing to the superheated vapour state (point 1 ) , again available at the inlet of the compressor A .

[0015] According to the present invention, the refrigeration system 1 comprises a compressor 2 , a condenser 3 f luidically connected downstream of the compressor 2 , a lamination member 4 fluidically connected downstream of the condenser 3 , and an evaporator 5 fluidically connected between the lamination member 4 and the compressor 2 . A working f luid f lows in a closed loop through said components of the refrigeration system 1 , implementing a refrigeration cycle .

[0016] In a preferred embodiment , the refrigeration system 1 comprises a first branch 21 , in which the working fluid circulates from the compressor 2 to the condenser 3 , a second branch 22 , in which the working fluid circulates from the condenser 3 to the lamination member 4 , a third branch 23 , in which the working fluid circulates from the lamination member4 to the evaporator 5 , and a fourth branch 24 , in which the working fluid circulates from the evaporator 5 to the compressor 2 .

[0017] According to the present invention, the refrigeration system 1 comprises a fluid power machine 6 f luidically connected between the lamination member 4 and the evaporator5 .

[0018] The term "fluid power machine" indicates a drivingmachine that processes the working fluid to transform the kinetic energy of the working fluid into mechanical energy, preferably in the form of rotation and / or translation of a movable member , such as for example the rotation of a drive shaft of the fluid power machine .

[0019] Specifically, the fluid power machine 6 divides the third branch 23 into a first sub-branch, in which the working fluid circulates from the lamination member 4 to the fluid power machine 6 , and a second sub-branch, in which the working fluid circulates from the fluid power machine 6 to the evaporator 5 .

[0020] According to the present invention, the fluid power machine 6 comprises a motor chamber and a motor member movably housed in the motor chamber . The fluid power machine 6 further comprises an inlet mouth for inj ecting working fluid into the motor chamber and moving the motor member , and an outlet mouth for the exit of working fluid from the motor chamber .

[0021] In particular, the working fluid, coming from the lamination member 4 , enters the motor chamber through the inlet mouth, moves the motor member , and leaves the motor chamber through the outlet mouth, towards the evaporator 5 .

[0022] Therefore , in the motor chamber, the kinetic energy of the working fluid decreases , as it slows down, moving the motor member of the fluid power machine 6 , thereby generating mechanical energy .

[0023] In other words , downstream of the fluid power machine 6 , the two-phase working fluid is in a at low pressure and temperature state , with an enthalpy ( point 5 of the graph in figure 2a ) lower as compared with the enthalpy that the working f luid would have in a refrigeration system without the fluid power machine 6 (point 4 of the graph in figure 2a ) , as it has transferred a share of its kinetic energy to the motor member . In particular, the transfer of kinetic energy to the motor member , that is a reduction of the internal energy of the working fluid, entails a reduction of the enthalpy of the working fluid, which results in a reduction of the title of the vapour generated by the lamination member 4 , thus in an increase of the liquid phase available to the evaporator 5 .

[0024] In a preferred embodiment , the fluid power machine 6 is a hydraulic turbine , preferably a Pelton turbine . Specifically, the motor member is the blade assembly of the turbine that rotates , for example , solidly engaged to a drive shaft of the turbine .

[0025] In a preferred embodiment , the fluid power machine 6 is a piston engine . Specifically, the motor member is the piston assembly of the engine that moves , for example , a drive shaft of the engine .

[0026] In a preferred embodiment , the refrigeration system 1 comprises an electric machine 7 operatively connected to the fluid power machine 6 to generate electricity .

[0027] Specifically, the electric machine 7 receives at the input mechanical energy from the fluid power machine 6 and provides electricity at the output .

[0028] Preferably, the movement or the rotation of a drive shaft of the fluid power machine 6 sets in movement or in rotation an input shaft of the electric machine 7 .

[0029] In a preferred embodiment , the refrigeration system 1 comprises an electric energy accumulator , for example a battery pack, in which the electricity generated by the electric machine 7 is stored .

[0030] In a preferred embodiment , the refrigeration system 1 is connected to the network infrastructure for the transmission and distribution of electricity, to feed the electricity generated by the electric machine 7 .

[0031] In a preferred embodiment , the electric machine 7 is operatively connected to the compressor 2 to power it electrically . Preferably, the electricity generated by the electric machine 7 is supplied to the compressor 2 for its operation .

[0032] In a preferred embodiment , the refrigeration system 1 comprises a fluid operating machine 8 operatively connected to the fluid power machine 6 to perform an action on a fluid, for example the action of compres sing a fluid . Preferably, the fluid power machine 6 performs work on a fluid .

[0033] Preferably, the fluid operating machine 8 performs anaction on the working fluid of the refrigeration system 1 , for example moves or compresses the working fluid . Preferably, the fluid power machine 6 performs work on the working fluid .

[0034] Specifically, the mechanical energy generated by the fluid power machine 6 is supplied at the input to the fluid operating machine 8 for its operation . Preferably, a drive shaft of the fluid power machine 6 is operatively connected, for example by means of gears or belts or couplings or other power transmission systems , to a drive shaft of the fluid operating machine 8 .

[0035] In a preferred embodiment , the fluid operating machine 8 is an auxiliary compressor fluidically connected upstream of the compressor 2 to precompress the working fluid circulating from the evaporator 5 towards the compressor 2 .

[0036] In particular, the auxiliary compressor divides the fourth branch 24 into a first sub-branch, in which the working fluid circulates from the evaporator 5 to the auxiliary compressor, and a second sub-branch, in which the working fluid circulates from the auxiliary compressor to the compressor 2 .

[0037] In a preferred embodiment , the electric machine 7 is operatively connected to the auxiliary compressor to power it electrically . Preferably, the electricity generated by the electric machine 7 is supplied at the input to the auxiliary compressor for its operation .

[0038] In a preferred embodiment , the fluid operating machine 8 is an auxiliary blower fluidically connected upstream of the compressor 2 to precompress the working fluid circulating from the evaporator 5 to the compressor 2 .

[0039] Preferably, the auxiliary blower divides the fourth branch 24 into a first sub-branch, in which the working fluid circulates from the evaporator 5 to the auxiliary blower, and a second sub-branch, in which the working fluid circulates from the auxiliary blower to the compressor 2 .

[0040] In a preferred embodiment , the electric machine 7 is operatively connected to the auxiliary blower to power it electrically . Preferably, the electricity generated by the electric machine 7 is supplied at the input to the auxiliary blower for its operation .

[0041] Preferably, the refrigeration system 1 comprises an auxiliary by-pass circuit 26 and an auxiliary valve 26' , for example a check valve , configurable in a closing configuration, in which it prevents the circulation of working fluid towards the fluid operating machine 8 , for example the auxiliary compressor or the auxiliary blower . Preferably, the auxiliary valve 26 ' operates as a function of the pressures in the auxiliary by-pass circuit 26 and in the fourth branch 24 , in particular in the first sub-branch of the fourth branch 24 . Advantageously, the refrigeration system 1 makes it possible to exclude the fluid operating machine in the event ofmalfunctions , maintenance or other specific requirements .

[0042] In a preferred embodiment , the refrigeration system 1 comprises a by-pass valve 9 fluidically connected upstream of the fluid power machine 6 which, in a closing conf iguration, prevents the circulation of the working fluid towards the fluid power machine 6 . In an opening configuration , the bypass valve allows the flow of the working fluid towards the fluid power machine 6 .

[0043] Specifically, the by-pass valve is fluidically connected along the first sub-branch of the third branch 23 , that is between the lamination member 4 and the fluid power machine 6 .

[0044] Preferably, the by-pass valve comprises a by-pass conduit 25 fluidically connected upstream of the fluid power machine 6 , for example with the first sub-branch of the third branch 23 , and downstream of the fluid power machine 6 , for example with the second sub-branch of the third branch 23 . Preferably, in the closing configuration, the working fluid coming from the lamination member 4 circulates in the by-pass conduit 25 and continues towards the evaporator 5 . In other words , preferably, in the closing configuration, the fluid operating machine 8 is excluded from the fluidic path of the working fluid .

[0045] In a preferred embodiment , the by-pass valve 9 , the lamination member 4 and the fluid power machine 6 are made as a whole as an integrated unit . In particular, said integratedunit is fluidically connected between the condenser 3 and the evaporator 5 .

[0046] In a preferred embodiment , the lamination member 4 and the fluid power machine 6 are made as a whole as an integrated unit . In particular, said integrated unit is fluidically connected between the condenser 3 and the evaporator 5 .

[0047] In a preferred embodiment , the refrigeration system 1 comprises a de Laval nozz le operatively connected upstream of the fluid power machine 6 to increase the speed of the fluid up to supersonic speeds , that is greater than the speed of sound .

[0048] In a preferred embodiment , the by-pass valve 9 , the lamination member 4 , the fluid power machine 6 and the de Laval noz zle are made as a whole as an integrated unit fluidically connected between the condenser 3 and the evaporator 5 .

[0049] In a preferred embodiment , the lamination member 4 , the fluid power machine 6 and the de Laval no zzle are made as a whole as an integrated unit fluidically connected between the condenser 3 and the evaporator 5 .

[0050] In a preferred embodiment , the refrigeration system 1 comprises a gas expander device configured to slow down a fraction of the working fluid to subsonic speeds , that is lower than the speed of sound .

[0051] In a preferred embodiment , the by-pass valve 9 , thelamination member 4 , the fluid power machine 6 and the gas expander device are made as a whole as an integrated unit fluidically connected between the condenser 3 and the evaporator 5 .

[0052] In a preferred embodiment , the lamination member 4 , the fluid power machine 6 and the gas expander device are made as a whole as an integrated unit fluidically connected between the condenser 3 and the evaporator 5 .

[0053] In a preferred embodiment , the refrigeration system 1 comprises a sensor 10 operatively connected to the fluid power machine 6 to detect the physical quantities relating to its operation . Preferably, with reference to the f luid power machine 6 , the sensor 10 is configured to detect at least one among : the flow rate of the working fluid, the upstream working f luid pressure , the downstream working fluid pressure , the number of revolutions or the number of cycles of the motor member .

[0054] In a preferred embodiment , the refrigeration system 1 comprises an electronic control unit 11 operatively electrically connected to the sensor 10 and programmed to control the by-pass valve 9 in the closing configuration as a function of the detection of the sensor 10 , for example programmed to receive and process a detection signal generated by the sensor 10 and consequently control the switching of the by-pass valve from the opening configuration to the closingconfiguration .

[0055] Preferably, the electronic control unit 11 controls the by-pass valve in the closing configuration upon detecting a downstream pressure of the working fluid of the fluid power machine 6 lower than a predefined minimum threshold value , for example an absolute value or a differential value of the evaporation and condensation pressures of the working fluid .

[0056] Preferably, the electronic control unit 11 controls the by-pass valve in the closing configuration upon detecting a number of revolutions of the motor member of the fluid power machine 6 lower than a predefined minimum value of number of revolutions .

[0057] In a preferred embodiment , shown by way of example in figure 3 , upstream of the lamination member 4 , the refrigeration system 1 comprises a secondary lamination member12 fluidically connected downstream of the condenser 3 and a secondary heat exchanger 13 fluidically connected between the secondary lamination member 12 and the compressor 2 . The secondary lamination member 12 and the secondary heat exchanger 13 are fluidically connected to supercool the working fluid supplying the lamination member 4 . Preferably, the working fluid evaporated in the secondary heat exchanger13 is conveyed at the inlet of the compressor 2 . In particular, the secondary lamination member 12 draws off a fraction of the liquid phase of the working fluid, whichevaporates in the secondary heat exchanger 13 and is sucked in by the compressor 2 . The remaining fraction of liquid of the working f luid enters the secondary heat exchanger 13 , in which it is supercooled, and continues towards the lamination member 4 .

[0058] Specifically, the secondary lamination member 12 and the secondary heat exchanger 13 as a whole implement an economiser circuit , also known as economizer .

[0059] In a preferred embodiment , the refrigeration system 1 comprises a first conduit 31 , preferably extending from the first sub-branch of the second branch 22 , in which the working fluid coming from the condenser 3 circulates both in the secondary lamination member 12 and in the secondary heat exchanger 13 . Preferably, the refrigeration system 1 comprises a second conduit 32 , in which the working fluid leaving the secondary heat exchanger 13 enters the compressor 2 . Preferably, the refrigeration system 1 comprises a third conduit 33 , in which the working fluid coming from the condenser 3 enters the secondary heat exchanger 13 . In particular, the secondary lamination member 12 is fluidically excluded along the third conduit 33 . Preferably, the refrigeration system 1 comprises a fourth conduit 34 , in which the working fluid leaving the secondary heat exchanger 13 continues towards the lamination member 4 .

[0060] With reference to figures 3 and 3a, only a fraction ofworking fluid circulates in the first conduit 31 and enters the secondary lamination member 12 ( point 6 ) , from which it exits with a lower pressure (point 7 ) , continues into the secondary heat exchanger 13 , in which it absorbs heat and evaporates at constant pressure (point 9 ) . Circulating in the second conduit 32 , the working fluid enters the compressor 2 . Advantageously, the fluid that from the second conduit enters the compressor is at a higher pressure as compared with the evaporation pressure in the evaporator 5 , so the compressor has higher efficiency . The remaining fraction of working fluid circulates in the third conduit 33 in the form of subcooled liquid, enters the secondary heat exchanger 13 , in which it releases heat (point 3 ) , and continues in the fourth conduit 34 towards the lamination member 4 . Advantageous ly, the working fluid at the inlet of the lamination member has a lower temperature , therefore lower enthalpy, increasing the liquid fraction available to the evaporator and improving the efficiency of the refrigeration cycle .

[0061] In a preferred embodiment , the fluid power machine 6 comprises one or more nozzles fluidically connected to the inlet mouth of the fluid power machine 6 to inj ect one or more j ets of two-phase working fluid at high speed into the motor chamber . In particular, the j et of working f luid is directed in a direction such as to move the motor member .

[0062] Preferably, the working fluid enters the motor chamberthrough the noz zle assembly, in the form of a two-phase fluid j et .

[0063] The mass flow rate of the refrigeration system is a function of the volume of working fluid processed by the compressor, of the type of working fluid, of the evaporation pressure , of the superheating value , that is the difference between the temperature of the fluid at the inlet of the compressor 2 and the temperature of the saturated vapour at the evaporation pressure , of the condensation pressure and of the subcooling of the condensed fluid, that is the difference between the temperature of the saturated liquid at the condensation pressure and the temperature of the fluid at the inlet of the primary lamination member ( 4 ) , according to the following function :in which V is the displaced volume , R is the type of refrigerant , px is the evaporation pressure , p2is the condensation pressure , DTx is the superheating value of the evaporated fluid, and DT3is the subcooling value of the condensed liquid .

[0064] The specific volume of the evaporated gas is typically at least one order of magnitude greater as compared with the specific volume of the atomised liquid . This increase in volume of the working fluid determines a significant reduction of the average density, with consequent considerable increaseof the speed, according to the following formula :Cost

[0065] The speed at the outlet of the no zzles is calculated with the following formula :in whichis the volumetric flow rate of the two-phase fluid andis the equivalent area of the nozzle section , which depends on the evaporation pressure , on the subcooling of the working fluid and on the mass flow rate of the compressor, in turn chosen as a function of the thermal load and of the temperatures of the two external environments between which the refrigeration system or heat pump system operates . In particular , the equivalent area of the noz zle section is chosen as a function of the speeds of the working fluid .

[0066] The thrust force of the working fluid is given by the following formula :in which m is the mass flow rate and ilt’ is e the variation of the velocity vector in magnitude and direction due to the fluid power machine .

[0067] The size of the nozzle is calculated according to the following formula :in whichis the volumetric flow rate of the working fluid to be optimised and C is the speed imposed on the working fluid at the inlet of the fluid power machine 6 .

[0068] The mechanical power generated by the motor member is cording to the following formula :is the speed of the motor member, whether linear speed in the case of a translating member , for example a piston, or peripheral speed in the case of a rotating member, for example a blade assembly of the turbine .

[0069] The cooling power of a refrigeration system for cooling an environment without a fluid power machine is calculated according to the following formula :in which m is the mass flow rate of the refrigeration system, is the enthalpy of the working fluid at the outlet of the evaporator 5 , andis the enthalpy of the working fluid at the inlet of the evaporator 5 .

[0070] The cooling power of the refrigeration system provided with the fluid power machine 6 is calculated with the following formula :in which m is the mass flow rate of the system,is the enthalpy of the working fluid at the outlet of the evaporator,is the enthalpy of the working fluid at the outlet of the motor member .

[0071] The enthalpy of the working fluid at the outlet is calculated according to the following formula :is the square of the outlet speed from thechine and rjf is the thermodynamic efficiency of the fluid power machine .

[0072] The percentage increase of the cooling power of the refrigeration system compris ing the fluid power machine as compared with a refrigeration system without a fluid power lculated according to the following formula :is the cooling power exchanged by the evaporator of the system comprising the fluid power machine , andis the cooling power exchanged by the evaporator of the refrigeration system without a fluid power machine .

[0073] The increase in cooling power is approximately equal to the mechanical power generated by the fluid power machine .

[0074] The calculation of the COP of the refrigeration system without a fluid power machine is defined by the formula :in whichis the cooling power exchanged by the evaporator of the refrigeration system without a fluid power machine , andPeis the electric power absorbed by the compressor .

[0075] The calculation of the COP of the refrigeration system with a fluid power machine is in accordance with the following formula :is the cooling power exchanged by the evaporatorm with a fluid power machine , andis the mechanical power generated by the motor member , calculated according to the following formula :in which T|m is the mechanical efficiency of the fluid power machine .

[0076] The percentage increase of the COP is calculated according to the following formula :

[0077] In accordance with the formulas reported above an example of calculation of the characteristic parameters for a medium-temperature refrigeration system with air condensation is reported below . In particular, the refrigeration system is schematised in figure 4 and the refrigeration cycle is represented in figure 4a . The working fluid is an azeotropic mixture of HFC refrigerant , having chemical formula CHF2CFR3 / CH3CFR3 and molecular weight ( grams per molecule ) of 98 . 86 , known as R507A. The flow rate is approximately 0 . 1815kg / s . The working fluid in the superheated vapour state enters the compressor with pressure of about 281 kPa (2.81 bar) , temperature of about -13°C and enthalpy of about 358.6 kJ / kg (point 1) . The working fluid exits the compressor with pressure of about 1959 kPa (19.59 bar) , temperature of about 71.2°C and enthalpy of about 414.6 kJ / kg (point 2) and enters the condenser 3, inside which it releases heat to an external environment. At the outlet of the condenser 3 the working fluid is in a subcooled liquid state, with pressure of about 1959 kPa (19.59 bar) , temperature of about 37°C and enthalpy of about 254.5 kJ / kg (point 3) . The working fluid enters the lamination member 4 and exits in the vapour state with a pressure of about 281 kPa (2.81 bar) , temperature of about - 23°C and the same enthalpy (point 4) . The two-phase working fluid enters the fluid power machine, in which it decreases its kinetic energy, slowing down, and exits with enthalpy of about 249.977 kJ / kg (point 5) . The working fluid enters the evaporator 5, in which it absorbs heat Qin from an external environment and returns to the initial point of the cycle (point 1) . The refrigeration system described above has a cooling power of about 20.4 kW andequal to about 2.0. The same refrigeration system without the fluid power machine has a cooling power of about 19.0 kW and ££>P equal to about 1.8. The percentage increase of the COPis approximately equal to about 10.07%.

[0078] In figure 5 two further examples of calculation of the characteristic parameters are reported, respectively for a low-temperature refrigeration system with air condensation and a high-temperature refrigeration system with evaporative tower condensation .

[0079] The power of a heat pump system, adapted to release heat to an environment , without a f luid power machine is calculated according to the following formula :in which m is the mass flow rate of the system, lt.2is the enthalpy of the working fluid at the inlet of the condenser , and is the enthalpy of the working fluid at the outlet of the condenser .

[0080] The calculation of the COP of the heat pump system comprising the fluid power machine is given by the following formula :wherein out is the power exchanged by the capacitor of the system without fluid power machine , and P* is the electric power absorbed by the compressor .

[0081] The calculation of the COP of the heat pump system comprising the fluid power machine is given by the following formula :

[0082] The percentage increase of the COP is calculated as :

[0083] In accordance with the formulas reported above , Figure 6 shows an example of calculation of the characteristic parameters for a heat pump system .

[0084] In a preferred embodiment , a retrofit system for a refrigeration system comprises a bypass valve 9 fluidically connected downstream of the lamination member 4 and a fluid power machine 6 downstream of the bypass valve 9 , implemented as an integrated unit fluidically connectable between a condenser 3 and an evaporator 5 of the refrigeration system.Preferably, the retrofit system comprises a lamination member4 upstream of the fluid power machine 6 , for example upstream of the bypass valve 9 .

[0085] In one embodiment , a retrofit system for a refrigeration system comprises an lamination member 4 and a fluid power machine 6 f luidically connected downstream of the lamination member 4 , implemented as an integrated unit fluidically connectable between a condenser 3 and an evaporator 5 of the refrigeration system.

[0086] In one embodiment , the fluid power machine 6 has the characteristics as described above , for example comprising one or more noz zles . In particular, the fluid power machine 6 is configured to operate on a two-phase working fluid of arefrigeration system.

[0087] In a preferred embodiment , the retrof it system comprises one of a de Laval noz zle and a gas expansion device , integrated and fluidically connected between the bypass valve 9 and the fluid power machine 6 .

[0088] In one embodiment , a system comprises an evaporator , a compressor downstream of the evaporator , a condenser downstream of the compressor, a lamination member and a retrofit system having the characteristics described above and fluidically connected in a closed circuit between the lamination member and the evaporator .

[0089] In one embodiment , a system comprises an evaporator , a compressor downstream of the evaporator , a condenser downstream of the compressor , and a retrofit system having the characteristics described above , in particular comprising a lamination member upstream of the fluid power machine 6 , for example upstream of the bypass valve 9 , wherein the retrofit system is fluidically connected in a closed circuit between the condenser and the evaporator .

[0090] Innovatively, the refrigeration system and the retrofit kit according to the present invention fully achieve the intended purpose .

[0091] Advantageously, the refrigeration system has high energy efficiency, as it extracts energy from the working fluid, otherwise wasted, to generate electric energy or mechanicalenergy, for example used to perform work on a fluid .

[0092] Advantageously, the refrigeration system reduces the enthalpy of the working fluid by reducing the internal energy of the working fluid, that is , by extracting the kinetic energy of the working fluid .

[0093] Advantageously, the refrigeration system improves the efficiency of the refrigeration cycle , as it extracts energy from the working fluid, otherwise wasted, and powers its components , for example the compressor .

[0094] Advantageously, the refrigeration system for applications of heat removal from an environment improves the efficiency of the refrigeration cycle , as it recovers energy from the reduction of the speed of the working fluid entering the evaporator . Otherwise , such energy would degenerate into heat due to internal friction .

[0095] Advantageously, the heat pump system for applications of heat release to an environment has an improved overall efficiency . Although the driving machine removes the kinetic energy corresponding to the deceleration of the working fluid, and therefore removes such contribution from the energy released by the condenser , the generation of mechanical energy and possibly of electrical energy more than compensates for such effects related to the deceleration of the working fluid, resulting in a clearly positive increase in the overall efficiency of the system.

[0096] Advantageously, in case of malfunctions or maintenance , the refrigeration system allows the fluid power machine to be excluded from the fluid circuit of the working fluid .

[0097] Advantageously, the refrigeration system allows the detection of malfunctions or anomalies of the fluid power machine .

[0098] Advantageously, the refrigeration system allows the operation of the fluid power machine to be excluded, depending on the requirements .

[0099] Advantageously, the refrigeration system can be configured as a traditional system without the fluid power machine .

[0100] Advantageously, the refrigeration system optimises the characteristics of the working fluid at the inlet of the fluid power machine .

[0101] Advantageously, the refrigeration system allows the use of economiser circuits , including traditional or pre-existing types , improving the efficiency of the refrigeration cycle .

[0102] Advantageously, in the context of highly energy- intensive industrial plants requiring power in the order of megawatts , the refrigeration system achieves significant economic savings , even with eff iciency optimisations of only a few percentage points , as in the case of refrigeration systems using ammonia-based working fluids characterised, for the same cooling capacity, by low mass flow rates due to the highevaporation latent heat values that characterise such fluids .

[0103] dvantageously, the refrigeration system is particularly effective for powers exceeding 20 kW .

[0104] Advantageously, the retrofit system makes it possible to improve the efficiency of pre-existing refrigeration systems , overcoming the need to redesign the entire system or to make significant modifications to its components or to the thermodynamic cycle .

[0105] Each variant described as belonging to a possible embodiment can be implemented independently of the other described variants .

[0106] With reference to the embodiments of the invention described above , a person skilled in the art could make variants or replace elements with other functionally equivalent elements , in order to meet contingent needs . Such variants are also included within the scope of protection as defined by the following claims .

Claims

CLAIMS1. A refrigeration system (1) comprising a compressor (2) , a condenser (3) fluidically connected downstream of the compressor (2) , a lamination member (4) fluidically connected downstream of the condenser (3) , and an evaporator (5) fluidically connected between the lamination member (4) and the compressor (2) , in which working fluid circulates in a closed loop; wherein the refrigeration system (1) comprises a fluid power machine (6) fluidically connected between the lamination member (4) and the evaporator (5) , comprising a motor chamber, a motor member movably housed in the motor chamber, an inlet mouth for injecting working fluid into the motor chamber and moving the motor member, and an outlet mouth for releasing working fluid from the motor chamber.

2. A refrigeration system (1) according to claim 1 or claim 2, comprising an electric machine (7) operatively connected to the fluid power machine (6) to generate electricity.

3. A refrigeration system (1) according to claim 2, wherein the electric machine (7) is operatively connected to electrically actuate the compressor (2) .

4. A refrigeration system (1) according to any one of the preceding claims, comprising a fluid operating machine (8) operatively connected to the fluid power machine (6) to perform an action on a fluid, preferably the working fluid of the refrigeration system.

5. A refrigeration system (1) according to claim 4, whereinthe fluid operating machine (8) is an auxiliary compressor or an auxiliary blower, fluidically connected upstream of the compressor ( 2 ) .

6. A refrigeration system (1) according to any one of the preceding claims, wherein the fluid power machine (6) is a hydraulic turbine, preferably a Pelton turbine or a piston engine .

7. A refrigeration system (1) according to any one of the preceding claims, comprising a by-pass valve (9) fluidically connected upstream of the fluid power machine (6) and configurable in a closing configuration, in which it prevents the working fluid from circulating towards the fluid power machine ( 6 ) .

8. A refrigeration system (1) according to claim 7, wherein the by-pass valve (9) , the lamination member (4) and the fluid power machine (6) are made as a whole as an integrated unit fluidically connected between the condenser (3) and the evaporator (5) .

9. A refrigeration system (1) according to any one of the preceding claims, comprising a sensor (10) operatively connected to the fluid power machine (6) for detecting the physical quantities relating to its operation, preferably at least one of: the upstream working fluid pressure, the downstream working fluid pressure, the number of revolutions or number of cycles of the motor member.

10. A refrigeration system (1) according to claim 9 and anyone of claims 7 and 8, comprising an electronic control unit(11) programmed to control the by-pass valve (9) in the closing configuration as a function of the detection of the sensor ( 10 ) .

11. A refrigeration system (1) according to any one of the preceding claims, comprising one of:- a De Laval nozzle operatively connected upstream of the fluid power machine (6) to increase the fluid speed at the inlet;- a gas expander device operatively connected upstream of the fluid power machine (6) to decrease the fluid speed at the inlet .

12. A refrigeration system (1) according to any one of the preceding claims, comprising a secondary lamination member(12) fluidically connected downstream of the condenser (3) , and a secondary heat exchanger (13) fluidically connected between the secondary lamination member (12) for supercooling the working fluid supplied to the lamination member (4) .

13. A retro-fit system for a refrigeration system, comprising a by-pass valve (9) and a fluid power machine (6) downstream of the by-pass valve (9) , made as a whole as an integrated unit fluidically connectable between a condenser (3) and an evaporator (5) of the refrigeration system.

14. A retro-fit system for a refrigeration system, comprising a lamination member (4) and a fluid power machine (6) fluidically connected downstream of the lamination member (4) ,made as a whole as an integrated unit fluidically connectable between a condenser (3) and an evaporator (5) of the refrigeration system.

15. The retro-fit system according to claim 14, wherein the integrated unit comprises a by-pass valve (9) integrated and fluidically connected between the lamination member (4) and the fluid power machine (6) .

16. A refrigeration system comprising an evaporator (5) , a compressor (2) downstream of the evaporator, a condenser (3) downstream of the compressor, and a retro-fit system according to claim 14 or 15, wherein the retro-fit system is fluidically connected in a closed circuit between the condenser (3) and the evaporator (5) .

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