ABSORPTION HEAT PUMP FOR IMPROVED PERFORMANCE IN HIGH DELIVERY WATER TEMPERATURE OPERATING CONDITIONS

Abstract

An absorption heat pump apparatus for optimizing performance in low air temperature and/or high delivery water temperature operating conditions which maintains all the functions of the so-called booster systems, preventing the generator from exceeding the maximum temperature limits. Furthermore, the apparatus allows a significant increase in the efficiency of the heat pump when the booster mode is activated for producing high temperature hot water in the case of medium or high outdoor temperatures, i.e., conventionally, for producing domestic hot water which is required throughout the year.

Claims

1. An absorption heat pump comprising a generator adapted to produce steam starting from a first fluid and comprising a first outlet for supplying said steam, by means of a first line, to a condenser in heat exchange contact with a heat-transfer fluid; an evaporator fed by a second line arranged downstream of the condenser and comprising at least one first expansion valve; an absorber provided with a feeding inlet, connected to a third line which leads said steam exiting the evaporator, and with an outlet for an enriched solution of said first fluid absorbed in a second fluid; a heat exchanger, in heat transfer contact with said heat-transfer fluid, provided with an inlet connected to the outlet of the absorber; a pump having a suction side connected to an outlet of the heat exchanger; a circuit, in heat transfer contact with the absorber and having an inlet, connected by means of a fourth line to a delivery side of the pump, and an outlet connected to a rich solution inlet of the generator by means of a fifth line; a bypass line of the absorber connected to said fourth line and provided with a valve adapted to allow said absorber to be at least partially excluded from the circuit; a sampling line adapted to introduce the refrigerant liquid into the rich solution at an introduction point downstream of the pump; wherein said generator comprises a second lean solution outlet connected by a sixth lean solution line to a lean solution inlet of the absorber, said sixth lean solution line comprising first valve means configured to vary the refrigerant flow rate withdrawn downstream of the condenser by means of a line directed to an injector, by virtue of the variation of the rich solution flow rate in the bypass and therefore vary the refrigerant flow rate to the evaporator, so as to increase it when the environmental conditions favor the evaporation thereof, wherein said first valve means comprise at least one variable expansion valve.

2. The absorption heat pump according to claim 1 further comprising second control valve means, arranged on said line leading to said injector and adapted to reduce the withdrawal of refrigerant caused by the injector downstream of the condenser.

3. The absorption heat pump according to claim 1 wherein said first valve means comprise at least one variable expansion valve in parallel with a throttling valve.

4. The absorption heat pump according to claim 1 wherein said first valve means comprise at least one variable expansion valve in series with a throttling valve.

5. The absorption heat pump according to claim 1 wherein said first valve means comprise a first throttling valve in parallel to a variable expansion valve connected in series to a second throttling valve.

6. The absorption heat pump according to claim 1 wherein said first valve means comprise two or more throttling valves of different sizes, which may be selected independently by means of actuated shut-off valves to discreetly vary the lean solution flow rate.

7. The absorption heat pump according to claim 2 wherein said second valve means comprise an actuated valve.

8. The absorption heat pump according to claim 7 wherein said second valve means comprise a further flow rate control member.

9. The absorption heat pump according to claim 1 further comprising a heat exchanger between said fifth line and said sixth lean solution line.

10. The absorption heat pump according to claim 1, further comprising a throttling valve placed in said sixth lean solution line, upstream of the heat exchanger.

11. The absorption heat pump according to claim 1 wherein said first fluid is ammonia and said second fluid is a solution of water and ammonia.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further features and advantages of the invention will become apparent from the reading of the following detailed description, given by way of non-limiting example, with the aid of the figures shown on the accompanying drawings, in which:

[0029] FIG. 1 shows a functional block diagram of a preferred embodiment of the apparatus according to the present invention comprising an actuated control valve located on the liquid refrigerant line and a throttling valve on the lean solution line;

[0030] FIG. 2 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising an actuated valve, in parallel with a further flow rate control member, located on the liquid refrigerant line and a throttling valve on the lean solution line;

[0031] FIG. 3 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising a variable expansion valve on the lean solution line;

[0032] FIG. 4 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising a variable expansion valve in parallel with a throttling valve on the lean solution line;

[0033] FIG. 5 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising a variable expansion valve in series with a throttling valve on the lean solution line;

[0034] FIG. 6 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising, on the lean solution line, two or more throttling valves of different sizes, which may be selected independently by means of actuated shut-off valves;

[0035] FIG. 7 shows a functional block diagram of a preferred embodiment of the apparatus according to the present invention comprising an actuated control valve located on the liquid refrigerant line and a throttling valve on the lean solution line and comprising a further heat exchanger associated with the lean solution line;

[0036] FIG. 8 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising an actuated valve, in parallel with a further flow rate control member, located on the liquid refrigerant line and a throttling valve on the lean solution line, and comprising a further heat exchanger associated with the lean solution line;

[0037] FIG. 9 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising a variable expansion valve on the lean solution line, and comprising a further heat exchanger associated with the lean solution line;

[0038] FIG. 10 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising a variable expansion valve in parallel with a throttling valve on the lean solution line, and comprising a further heat exchanger associated with the lean solution line;

[0039] FIG. 11 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising a variable expansion valve in series with a throttling valve on the lean solution line, and comprising a further heat exchanger associated with the lean solution line; and

[0040] FIG. 12 shows a functional block diagram of another preferred embodiment of the apparatus according to the present invention comprising, on the lean solution line, two or more throttling valves of different sizes, which may be selected independently by means of actuated shut-off valves, and comprising a further heat exchanger associated with the lean solution line.

[0041] 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 OF THE INVENTION

[0042] The heat pump shown in the accompanying FIGS. 1-12 works with a cycle which uses a first fluid (in the specific case, ammonia) as refrigerant, which is absorbed into a second fluid (in this case, a solution of water and ammonia). The solution of the two fluids varies in composition during the thermodynamic cycle it goes through; it is therefore called lean when it contains a low quantity of said first fluid and rich when, instead, it contains a high quantity thereof.

[0043] The direct flame absorption heat pump comprises a conventional generator 2, or desorber, which receives heat from a burner, generally a gas burner, 35b on a preferably finned boiler 35, which feeds a distillation column 36. The distillation column 36, in turn, is connected to a rectifier 33 so that the outlet of the steam of the generator 2 is connected, by means of said rectifier 33 and a first steam line 3, to a condenser 4, located in heat exchange contact with a heat-transfer fluid which feeds the heating system. This fluid is usually water provided to the system by means of a pump, not shown.

[0044] Downstream of the condenser 4 there is a counter-current heat exchanger, 34, connected to said condenser 4 by a second line 6 on which there is a throttling valve 26, adapted to exchange heat with the steam circulating in a third line 8 which connects the outlet 7B of the evaporator 7in turn connected downstream of the heat exchanger 34 by means of the line 6 and the throttling valve 5to an inlet 10B of an absorber 10. Said evaporator 7 may have as a heat source outdoor air, or water from a low enthalpy geothermal source, groundwater, etc.

[0045] The vapor of said first fluid is thus blown into the mixer 9 of the absorber 10, and a rich two-phase solution (comprising ammonia vapor and ammonia absorbed in liquid water) therefore emerges from the outlet 10C of said mixer, which is sent as input to a second absorber 13 in heat exchange contact with the heat-transfer fluid of the heating system.

[0046] An outlet 13B of the heat exchanger 13 is connected to the suction side of a pump 14, the delivery side of which is connected, by means of a fourth line 15, to an inlet 16 of a circuit 16A, 16B in heat exchange contact with the absorber 10. Said fourth line 15 is in heat transfer contact with the rectifier 33 from which the ammonia-rich solution removes heat to facilitate the condensation of the water vapor.

[0047] Said circuit 16A, 16B is adapted to remove heat from the absorber 10 to then transfer it to the rich solution coming from the pump 14 before being introduced into the generator 2. In the first part of said circuit 16A the rich solution rises in temperature, and in the second part 16B the ammonia present in the solution begins to evaporate (under the pressure present in the circuit 16A, 16B) substantially anticipating the work then performed by the generator 2. The ammonia-rich solution and the ammonia vapor which has begun to form is then directed, by means of a fifth line 18, from the heat exchanger 10 to the inlet 2B of the generator 2.

[0048] At the base of the generator 2, close to the boiler 35, an outlet 2C is provided from which an ammonia-lean solution is conveyed, by means of a sixth line 19, to an inlet 10A of the absorber 10, after having released heat to the fluids present in the generator in a central 2D portion thereof. The line 19 is provided with at least one throttling valve 30.

[0049] The first line 3 is connected, downstream of the condenser 4, to a sampling line 20, which extends from a sampling point 24 and leads to the bypass line 80 at an introduction point 22A of an injector (venturi) 22. The bypass line 80 further comprises a solenoid valve 81 adapted to control the exclusion or activation of said bypass line 80 from the circuit.

[0050] The bypass line 80, by means of the dragging effect of the injector 22, acts so as to withdraw part of the liquid refrigerant output from the condenser 4, and mix it in the rich solution line in input to the generator 2. Furthermore, it prevents the rich solution from being heated in the rectifier 33 and in the absorber 10.

[0051] In further detail, the opening of the solenoid valve 81 introduces into the circuit a simultaneous bypass for the rich solution pumped towards the generator 2 and for a part of the liquid refrigerant output from the condenser 4, to re-introduce them directly into the generator 2, above the portion of exchanger 2D.

[0052] In essence, the bypass line 80 obtains two effects: on the one hand, with the sampling line 20, the rich solution is further enriched, thus increasing the thermal input which may be provided to the generator 2; on the other hand, the rich solution is sent to the generator without it being heated by the rectifier 33 and by the absorber 10, thus contributing, also in this case, to increasing the thermal input which may be provided.

[0053] Thereby, the thermal input of the generator 2 (usually, the combustion products of a boiler 35 with power modulation) is increased up to a maximum of +80% of the maximum power at nominal conditions. When the solenoid valve 81 is closed, the refrigerant bypass is inactive since the injector (or venturi) 22A is not crossed by the fluid and the flow in the reverse direction is prevented by the non-return valve 21.

[0054] The range of conditions within which the bypass may be inserted into the circuit may be advantageously programmed in the system controller.

[0055] In a preferred embodiment of the invention, shown in the accompanying FIG. 1, an actuated valve 31, comprising a control valve, is located on the liquid refrigerant line 20 upstream of the introduction point 22A of the injector 22. Such valve allows reducing the withdrawal of liquid refrigerant by the rich solution, and therefore increasing the refrigerant flow rate to the evaporator 7 where, in case of a sufficient temperature of the heat source (for example, the air temperature in summer or in mid-seasons), the thermal input and the overall efficiency of the heat pump are increased.

[0056] In an alternative embodiment of the invention, shown in the accompanying FIG. 2, the actuated valve 31 may be both a control valve as well as a shut-off valve, and is located in parallel with a further flow rate control member 31A, which, in case of a complete closure of the valve 31, determines the minimum flow rate of refrigerant ensured to the injector 22.

[0057] In alternative embodiments of the invention, the control of the refrigerant flow rate withdrawn from the rich solution in the injector 22 is advantageously obtained by directly controlling the lean solution flow rate, which, in turn, determines the rich solution flow rate. In fact, the pump 14 only acts on the flow rate received from the absorber 13, which consists of the lean solution flow rate and the refrigerant flow rate coming from the evaporator 7. The passage of a lower rich solution flow rate inside the injector (venturi) 22 results in the lesser withdrawal of refrigerant downstream of the condenser 4 by means of said sampling line 20.

[0058] The control of the lean solution flow rate may be achieved in a continuous manner by replacing the throttling valve 30 on the lean solution line 19 with a single variable expansion valve 30A, as shown in the accompanying FIG. 3, or by adding the aforesaid variable expansion valve 30A in parallel, as shown in FIG. 4, or in series, as shown in FIG. 5, to the throttling valve 30.

[0059] In a further alternative embodiment of the invention, shown in the accompanying FIG. 6, two or more throttling valves of different sizes (30, 30B) are used, which may be selected independently by means of actuated shut-off valves (30C) to discreetly vary the lean solution flow rate. A further version of the system described, shown in the accompanying FIGS. 7-12, may also comprise a further heat exchange between said fifth line 18 and said sixth line 19. This heat exchange is obtained by means of a heat exchanger 85 preferably of the counter-current type. Advantageously, upstream of the heat exchanger 85, in the sixth line 19 of the lean solution, a first throttling valve 32 is provided; in the sixth line 19, downstream of the heat exchanger 85, and on the withdrawal line 20, any of the combinations previously described, and represented in the accompanying FIGS. 1-6, of the aforesaid valves 30, 30A, 30B, 30C, 31, 31A, are provided.

[0060] Therefore, if the system is in high outdoor air temperature conditions, such that the evaporator may be very efficient (for example, in mid-seasons or in summer) and there is a need to produce very hot water, which requires activating the bypass circuit 80 (for example, for producing DHW), then, by selecting or controlling a suitable member for controlling the flow rate on the liquid refrigerant line 20 or on the lean solution line 19, the refrigerant flow rate to the evaporator 7 is increased, since the withdrawal thereof from the injector 22 is reduced, and the overall efficiency of the heat pump is increased.