PUMPING SYSTEM FOR ABSORPTION HEAT PUMP CIRCUITS

Abstract

The invention relates to a system for pumping a refrigeration mixture for absorption heat pump generators, comprising a support which integrates a membrane pump and a hydraulic pump for actuating the membrane pump in a single component, and using the driving feedback signals of the actuator motor, determines the existing fluid-dynamic conditions during the operation of the heat pump.

Claims

1. An absorption heat pump plant comprising a generator, a condenser, a first expansion valve, an evaporator, an absorber, a pumping system and a second expansion valve, connected so as to subject a refrigerant mixture to thermodynamic absorption cycles wherein the pumping system comprises a support, in which support a first housing is obtained for a first cylinder in which a first piston, connected to a direct drive motor, slides, and a second housing for a first membrane, wherein the second housing is closed by a plate, the first membrane dividing the second housing into a non-communicating first chamber and second chamber, the first chamber communicating with the head of the first cylinder by means of the support so that the reciprocating motion of the piston causes a pressure/vacuum of a fluid present in the first chamber so that the first membrane may be deformed, thus causing a corresponding pressure/vacuum in the second chamber, the second chamber communicating with a first intake duct and a first delivery duct of the refrigeration mixture, there being provided automatic valves for closing the first delivery duct when a vacuum adapted to draw the refrigeration mixture is created inside the second chamber, and for closing the first intake duct when an overpressure adapted to send the refrigeration mixture into the first pressurized delivery duct is created inside the second chamber.

2. The plant according to claim 1, wherein a third housing for a second membrane is obtained in the support, wherein the third housing is closed by a separate plate or by the same plate which closes the second housing, the second membrane dividing the third housing into a non-communicating third chamber and fourth chamber, the third chamber also communicating with the head of the first cylinder by means of the support so that the reciprocating motion of the first piston which slides in the first cylinder causes a pressure/vacuum of the fluid present in the third chamber so that the second membrane may be deformed, thus causing a corresponding pressure/vacuum in the fourth chamber, the fourth chamber communicating with a second intake duct and a second delivery duct of the refrigeration mixture, there being provided automatic valves for closing the second delivery duct when a vacuum adapted to draw the refrigeration mixture is created inside the fourth chamber, and for closing the second intake duct when an overpressure adapted to send the refrigeration mixture into the second pressurized delivery duct is created inside the fourth chamber.

3. The plant according to claim 2, wherein a fourth housing for a second cylinder inside which a second piston, connected to a direct drive motor, slides, is obtained in the support, the head of the second cylinder communicating with the third chamber, which third chamber does not communicate with the first chamber so that it is the reciprocating motion of the second piston to cause a pressure/vacuum of a fluid present in the third chamber, so that the second membrane may be deformed, thus causing a corresponding pressure/vacuum in the fourth chamber.

4. The plant according to claim 2, wherein the first and second delivery ducts communicate with a same outlet sleeve.

5. The plant according to claim 1, wherein there is present a container of the solution to be pumped at the plate so as to allow the drawing of the contents thereof by means of the intake ducts arranged at openings obtained in the closing plate to form intake gaps.

6. The plant according to claim 1, wherein the piston or the pistons are connected to an electric motor by means of a linkage.

7. The plant according to claim 1, wherein the electric motor has an interface for controlling the electric absorption parameters, said interface being connected or connectable to a control unit adapted to read and process said parameters in order to determine the flow conditions of the operating pumping system.

8. The plant according to claim 1, comprising a control unit for setting the operating parameters of the plant, wherein said control unit is interfaced with the control unit of the pumping system, or replaces said control unit, to detect the fluid-dynamic parameters of the pumping system and correspondingly act on the plant components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further features and advantages of the invention will become apparent from the reading of the following detailed description, given by way of a non-limiting example, with the aid of the figures shown on the accompanying drawings, in which:

[0026] FIG. 1 schematically shows the components of an absorption heat pump.

[0027] FIG. 2 schematically shows the pressures and temperatures in an absorption cycle.

[0028] FIG. 3 schematically shows the operating principle of a membrane pump.

[0029] FIG. 4 shows a pumping system according to an embodiment of the invention.

[0030] The following description of exemplary embodiments relates to the accompanying drawings. The same reference numbers in the various drawings identify the same elements or similar elements. The following detailed description does not limit the invention. The scope of the invention is defined by the appended claims.

DETAILED DESCRIPTION

[0031] With reference to FIG. 1, an absorption heat pump comprises a generator 1, a condenser 2, a first expansion valve 3, an evaporator 4, an absorber 5, a pumping system 6, and a second expansion valve 7.

[0032] The fluid evolving in the machine is a mixture containing a cooling substance, for example ammonia in water. Due to an amount of heat Qin1 which is supplied to generator 1, for example by means of a gas burner, the refrigerant, being the most volatile component of the mixture, separates from the solution. The vapor thus generated is sent to condenser 2, where it condenses by yielding heat Qout1 to an external source. Generator 1 and condenser 2 are both at a pressure Pcond which depends on the condensation temperature Tcond.

[0033] The refrigerant is then brought to a lower pressure Pevap by means of an expansion valve 3 and then sent to evaporator 4 in which it evaporates, removing heat Qin2 from an external source.

[0034] For the cycle to be repeated, the refrigerant needs to be brought back to solution. Such a task is assigned to absorber 5 in which the vapor of the low temperature refrigerant Tevp from evaporator 4 and the solution from generator 1 brought back to low pressure by an expansion valve 7 meet. Heat Qout2 also needs to be removed from absorber 5 to allow the condensation of the refrigerant and the dilution of the solution. The solution thus enriched is brought to high pressure Pcond by the pumping system 6 to be introduced into generator 1 again, where it starts its cycle again. The pumping system 6 absorbs electricity (indicated by Win in the drawing).

[0035] FIG. 2 schematically shows the pressures and temperatures involved in an absorption cycle like that described above indicating the energy exchanged by means of arrows.

[0036] Overall, the energy balance is as follows:

Q.sub.out1+Q.sub.out2=Q.sub.in1+Q.sub.in2+W.sub.in.fwdarw.Q.sub.COND+Q.sub.ASSORB=Q.sub.GEN+Q.sub.EVAP+W.sub.POMPA

[0037] While the heating and cooling efficiencies are given by:

[00001]${\eta }_{\mathrm{COOL}}=\frac{Q_{\mathrm{in}2}}{Q_{\mathrm{in}1}+W_{\mathrm{in}}}=\frac{Q_{\mathrm{EVAP}}}{Q_{\mathrm{GEN}}+W_{\mathrm{POMPA}}}$${\eta }_{\mathrm{HEAT}}=\frac{Q_{\mathrm{out}1}+Q_{\mathrm{out}2}}{Q_{\mathrm{in}1}+W_{\mathrm{in}}}=\frac{Q_{\mathrm{COND}}+Q_{\mathrm{ASSORB}}}{Q_{\mathrm{GEN}}+Q_{\mathrm{POMPA}}}=\frac{Q_{\mathrm{GEN}}+Q_{\mathrm{EVAP}}+W_{\mathrm{POMPA}}}{Q_{\mathrm{GEN}}+W_{\mathrm{POMPA}}}=1+\frac{Q_{\mathrm{EVAP}}}{Q_{\mathrm{GEN}}+W_{\mathrm{POMPA}}}$

[0038] Several variants are possible starting from the base diagram shown in FIG. 1, mostly aiming to optimize the thermal exchanges and therefore increase the efficiencies, for example by using recuperative exchangers.

[0039] As for the pumping system 6, this conventionally comprises a membrane pump actuated by a hydraulic pump by means of a pressurized duct.

[0040] With reference to the exemplary diagram shown in FIG. 3, a membrane pump 60 consists of two chambers 106, 206 separated by a membrane 306. By creating a pressure/vacuum in one of the two chambers 106, 206, the membrane 306 is deformed, thus causing a corresponding pressure/vacuum in the other chamber 206, 106. By connecting an intake duct 406 and a delivery duct 506 to one of the two chambers 106 by means of automatic valves 606, 706, which open in opposite direction when a given pressure is reached, a liquid can be drawn from the low pressure intake duct 406 to send it into the high pressure delivery duct 506, thus utilizing the vacuum and the subsequent pressure caused by the motion of the membrane, as shown by the arrows in the drawing. Oil is used to move the membrane, which oil is alternatively introduced/drawn into/from the other chamber 206 by a hydraulic piston pump (not shown). The actuation of the hydraulic pump occurs by means of an electric bel-reduction motor.

[0041] The invention relates to an improvement of the known pumping systems.

[0042] FIG. 4 shows a pumping system 6 according to an embodiment of the present invention. The system comprises an electric motor 11 connected by a linkage 12, 12′ to a pair of pistons 13, 13′ which move coaxially in opposite directions inside corresponding cylinders 14, 14′. The cylinders are enclosed in a box-shaped body 15 extending transversely to the cylinders to form a support base for the whole pumping system, the cylinders 14, 14′ forming the front part thereof. Two separate housings 16, 16′ communicating with the corresponding cylinders 14, 14′ by means of the box-shaped body 15 are obtained in the rear part of the box-shaped body 15. Thereby, the oil pushed or drawn by the head of each of the two cylinders 14, 14′ is capable of reaching the corresponding housing 16, 16′ without requiring the use of pressurized ducts. The section of the box-shaped body 15 can be advantageously reduced to reduce the amount of oil required to keep the fluid-dynamic connection between head of the cylinders 14, 14′ and corresponding housings 16, 16′.

[0043] Each housing 16, 16′, typically cylindrical in shape, is closed at the top by a flange 17, 17′ by the interposition of a membrane (not shown in the drawing) so as to form a pair of chambers separated by the membrane itself. There can be only one closing flange which advantageously closes both housings.

[0044] The first chamber, adapted to receive the pressurized oil from the corresponding cylinder, is located at the bottom between box-shaped body and membrane, while the second chamber, adapted to draw and send under pressure the mixture containing the refrigerant, is located at the top of the first one, between membrane and closing flange.

[0045] The container 18 of the solution to be pumped is located in median position above the two flanges 17, 17′ so as to allow the intake of the contents thereof by means of an intake duct 19, 19′ arranged at an opening 20, 20′ made on each closing flange 17, 17′ to form an intake gap. There is a valve 21, 21′ between duct and intake gap for automatically closing the fluid-dynamic intake circuit when the solution chamber is pressurized.

[0046] The delivery duct 22, 22′ of the output pressurized solution is placed at another opening 23, 23′ made on the closing flange 17, 17′. Also in this case, there is a valve 24, 24′ between delivery duct 22, 22′ and delivery gap 23, 23′ for automatically closing the fluid-dynamic delivery circuit when the solution chamber is depressurized.

[0047] The two valves 21, 21′ and 24, 24′ operate in an opposite manner, i.e., when one opens, the other one closes, to ensure the pumping effect as described above with reference to FIG. 3.

[0048] The circuit is completed with a pair of filters 25, 25′ located in the intake ducts 19, 19′ and a supplying duct 26 for the solution tank 18. The delivery ducts 22, 22′ can be kept separate or be joined, as shown in the drawing. In this case, a T sleeve 27 collects the pressurized fluid output from each chamber.

[0049] The solution shown with dual cylinder and dual membrane is considered preferable because it allows reaching the pressure gradients required more easily with the low flow rates involved, thus simultaneously ensuring an absence of cavitation. It is obviously possible to provide the use of a pumping system comprising a single cylinder and a single membrane, as well as intermediate combinations, for example having a single cylinder in communication with two chambers each housing one membrane, or two cylinders controlled by two separate motors.

[0050] The motor(s) 11 advantageously are of the direct drive type, i.e., with load directly connected to the rotor. These motors are capable of delivering variable torques, even at a low number of revolutions, without requiring the use of gear trains or gear motors of any type by virtue of their characterizing electronic control.

[0051] A direct drive motor is a type of synchronous permanent magnet motor which directly actuates the load. When this type of motor is used, the use of a reducer is eliminated. Therefore, the number of movable components in the system is significantly reduced. This increases the efficiency and creates a silent and highly dynamic operation, as well as a very high duration of the system.

[0052] Examples of direct drive motors are torque motors, linear motors, and certain types of BLDC motors.

[0053] Direct drive motors are highly suitable for applications with significant torque fluctuations. This is because they just need a low torque to accelerate the motor with respect to gear motors, which have a lower torque/inertia ratio.

[0054] Moreover, they can also be provided as frameless motors. Frameless relates to a motor without a frame, housing, bearings, or feedback system. Accordingly, the plant suppliers are capable of integrating their motor in the application itself, eliminating the need for a further interfacing. This obviously decreases the cost of the integrated system.

[0055] A direct drive motor can be used in an absorption heat pump application due to the high torque at low angular speed, small dimensions, small weight, maximum power, presence of driving electronics providing an optimal speed control and useful information on rotor position and absorbed currents.

[0056] The direct drive motor can provide complete control of the electric absorption parameters precisely due to the presence of the electronic control. By connecting such an interface to a control unit, it is possible to read and process said parameters in order to determine the flow conditions of the operating pumping system.

[0057] Thereby, the same control unit or a plant control interfaced with the control unit or directly with the motor(s) of the pumping system can advantageously set the operating parameters of the plant based on the flow conditions of the pumping system.