ES2905544T3 - heat engine - Google Patents

Abstract

Thermal engine with a heat source (21), an expansion machine (10), a condenser (12), a condensate collection container (13), a working fluid pump (15), an evaporator (40) , a first container (1a) for heat transfer medium, a second container (1b) for heat transfer medium, a first pump for heat transfer medium (17), a second pump (41) for heat transfer medium of heat, a first valve (19), a second valve (20), a third valve (21) and a fourth valve (22), where the thermal engine is arranged in such a way that, during the operation of the thermal engine, the first container (1a), in a first operating mode of the heat engine, is hydraulically connected through the first valve (19) and the first pump (17) to the heat source (21) and, in a second mode of operation of the heat engine, is connected to the evaporator (40) through the second valve (20) and the second pump (41), where, in the first mode of operation of the heat engine, by connecting a first container (1a) to the heat source (21), the hottest heat transfer medium of the heat source (21 ) is filled at the top of the first container (1a) and the cooler heat transfer medium is removed from the lower area of the first container (1a) and returned to the heat source (21) and, in the second mode of operation of the heat engine, when the first container (1a) is connected to the evaporator (40), a hotter heat transfer medium is taken from the upper area of the first container (1a), it is led to the evaporator (40) and from the evaporator (40) it is pumped to the lower zone of the first container (1a) by means of the second pump (41), where the second container (1b), in the second operating mode of the heat engine, is hydraulically connected through the third valve (21) and the first pump (17) to the heat source (21) and, in the first mode of operation of the heat engine, it is connected through the fourth valve (22) and the second pump (41) to the evaporator (40), where, in the second mode of operation of the heat engine, when the second container (1b) is connected to the heat source (21), the hottest heat transfer medium of the heat source (21) is filled to the top of the second container (1b) and the transfer medium of colder heat is removed from the lower zone of the second container (1b) and taken to the heat source (21) and, in the first operating mode of the heat engine, when the second container (1b) is connected to the evaporator (40), the hotter heat transfer medium is withdrawn from the upper area of the second vessel (1b), brought to the evaporator (40) and pumped through the evaporator (40) by means of the second pump (41) to the lower region of the second container (1b), the heat engine being arranged in such a way that one of the first and second container (1a, 1b) is connected to the heat source (21) and the other of the first and second container (1b, 1a) is connected to the evaporator (40), so that the evaporation energy is transferred from one or from the other of the first and second containers to the evaporator (40) and the expansion machine (10) continuously receive steam during the operation of the heat engine and the connection of the container to the heat source (21) and the evaporator (40 ), during the operation of the heat engine, after some time it can be exchanged by means of the valves (19, 20, 21, 22).

Description

DESCRIPTION

heat engine

technical field

The present invention relates to a heat engine.

State of the art

Currently available heat engines (WKM) essentially consist of an evaporator, an expander, a condenser and a liquid pump. Additionally, an ERM includes a heat source, heat sink, valves, piping, and controls.

In the evaporator, the supplied heat is used to evaporate a working fluid, often water, at high pressure. The liquid working fluid is first preheated in one or more heat exchangers, evaporates and, in most cases, becomes superheated.

The steam generated in the heat exchangers is fed to the expansion machine (feed steam) and is expanded in it. The mechanical energy obtained with the expansion machine is converted for the most part into electrical energy and is fed into the electrical networks. The expanded steam is usually fed to a condenser and condensed there. The fully condensed working fluid is brought to a higher pressure by means of the liquid pump and returned to the evaporator. This closes the cycle of the work team. The process is called a cycle process.

Turbines are predominantly used as expansion machines. However, piston machines, screw machines and vane machines (rotary piston machines) are also possible. Continuously operating expansion machines, such as turbines, work particularly efficiently at a certain (expansion) pressure ratio n. If you deviate from this pressure relationship n, the exergetic quality of the relaxation drops rapidly. Batch expansion machines, such as piston machines and screw machines, have high exergetic qualities even with highly variable n pressure ratios. In the case of piston machines and screw machines, this results from the variability of the degree of filling of the cylinder. If the cylinder is only filled to a small extent (for example, 10%) during loading, a high % pressure ratio is achieved (for example, n = 2o with an adiabatic exponent ^k = 1.3). If the cylinder is very full (eg 50%), a low pressure ratio n is obtained (eg n = 2.5 to k = 1.3). This connection will play a role in what follows.

In the case of water as the working fluid, the heat engine process described above is called the Clasusius-Rankine process (CRC). If other tools are used, the process is called the Organic Rankine Process (ORC). Both types of processes roughly describe a rectangle on the T-S diagram. For this reason, CRC and ORC are among the Carnot-like processes. The efficiency of the processes can be increased by multi-stage evaporation, internal heat exchangers and the use of mixed working media (Kalina process).

Heat sources for low temperature sensible heat can be, for example, geothermal systems, solar systems, or waste heat streams from industrial processes. When low-temperature sensible heat is used, an ideal ERM process has the shape of a triangle on the T-s diagram. This type of process is called a triangular process or triangular cycle or trilateral cycle [1] in the literature. If a triangular process can be implemented, the triangular process can, for example, generate 30% more mechanical power from the available heat compared to ORC or CRC, which represent the state of the art [2, 3]. However, it has been possible to implement a triangular process.

Document DE102012007210A1 describes a heat engine with energy storage, which represents the closest state of the art to the present invention. WO2016/124709A1 and EP2703764A2 also describe heat engines with energy storage.

Problems to solve

The object of the invention is to present a structure and operation of a heat engine, the heat engine allows extensive implementation of a triangular process. The essence of the invention is the provision of heat transfer medium from one or more vessels in batch operation. The thermal engine according to the invention is defined by all the characteristics of the appended independent claim 1. Thermal energy for evaporation is transferred to the evaporator 40 from a vessel that is filled with a heat transfer medium (1a or 1b). This resolves the following issues:

1. Continuous operation of the heat engine is achieved through the use of two tanks, which can be alternatively connected via valves 19, 20, 21, 22 to the heat source or to the evaporator.

2. Harmful condensation of vapor in the EM expansion machine, 10 is prevented by superheating the working fluid after evaporation.

3. The working fluid is superheated and preheated by means of heat transfer from the heat source 21 and not from the vessels 1a, 1b. In this way, the working fluid is preheated and always superheated to approximately the maximum temperature of the heat source 21.

4. Heat still present in the working fluid after expansion is removed from the expanded vapor by heat exchanger (desuperheater) 32 and returned to the process in a further batch process with vessels 50a and 50b and preheater 45 with low dissipation.

Description of the invention

The invention is based on carrying out discontinuous processes in the field of thermodynamic cycles. There are essentially two types of cycle processes: heat pumps and heat engines. In the field of heat pumps, batch processes are already being successfully implemented (see eg EP2470850 A2). The technique of batch processes is transferred to heat engines with the present invention, as defined only in the appended independent claim 1.

Thermal engines usually work with a constant evaporation pressure. The heat source essentially provides sensible heat through a heat transfer medium. The heat transfer medium is, for example, water or thermal oil. If the heat source is exhaust gases or thermal water, the heat from the heat source must first be transferred to water or thermal oil (not shown). The heat is used in heat exchangers for preheating, evaporation and superheating of the working fluid. In batch processes, the heat transfer medium is temporarily stored in a container 1a. This container can be connected through valves to the heat source 21 for loading or to the evaporator 40 for unloading. During charging, the hotter working fluid flows from the heat source 21 to the top of the container 1a or 1b and the cooler working fluid leaves the bottom of the container. During unloading, the hotter heat transfer medium leaves the top of the vessel 1a and enters the evaporator 40, and the heat transfer medium that has cooled down a few Kelvin leaves the evaporator 40 at the bottom and at through a pump 41 at the bottom of the container 1a. In this way, the vessel 1a successively cools down, as a result of which the vapor pressure of the working fluid gradually decreases. Cooling continues until a minimum temperature of the heat transfer medium is reached. The time from when the cooling of the container 1a begins until the minimum temperature is reached is called a cycle.

According to EP document EP2470850 A2 for heat pumps, two vessels 1a and 1b are also used in the heat engine, so that the heat engine can be kept running without interruption. The vessels are constructed in such a way that they can be connected to the heat source 21 or to the evaporator 40 and that the hot and cold heat transfer medium mix as little as possible during this process.

If the cooling of one of the vessels 1a or 1b with cold heat transfer medium through the evaporator 40 is completed, the evaporator 40 can be connected to the heat source 21 through a valve 60 in an intermediate cycle. As a result, the warm heat transfer medium flows from the heat source to the evaporator 40 and heats it, then flows through the pumps 41 and 17 and the check valves 27, 18. Thus, the evaporator is preheated before connecting it to the second heated container. This prevents the hot heat transfer medium from the vessel from mixing with the cold heat transfer medium from the evaporator 40. Valves 19, 20, 21 and 22 are closed during the intermediate cycle.

In heat engines it is important that the working fluid in the expansion machine 10 does not condense. To prevent condensation, the working fluid is usually superheated after evaporation. Also, friction in expansion machines (for example, piston friction) and the conversion of eddy energy in the working fluid into heat counteract condensation. In the case of heat engines with batch process, the evaporation temperature of the working fluid drops sharply during the process and increases the risk of the expansion machine 10 cooling down and the working fluid condensing in the expansion machine. expansion. For this reason, the measures according to the invention against condensation in batch processes are of particular importance. On the one hand, the heat transfer medium is fed directly from the heat source to the superheater, thus achieving the highest possible superheat. The heat transfer medium has the same flow capacity (specific heat capacity times mass flow rate) as the gaseous working fluid. After the superheater, the heat transfer medium flows to the preheater. Here the working fluid is liquid and therefore has a higher specific heat capacity and consequently a higher flow capacity, which leads to dissipation in the preheater. To reduce dissipation, as As you will see later, the heat transfer medium is pumped from the desuperheater heat exchanger to the preheater.

To prevent condensation in the expansion machine, the expansion machine is heated and insulated in another embodiment of the invention.

In many implemented continuous processes, the working fluid leaves the ERM in a superheated state. According to the prior art, superheated heat may be removed from the process through a heat exchanger 32, called a desuperheater, and may for example be used to preheat the liquid working fluid. It is easy to explain by means of a T-s diagram that the degree of superheat at the end of the expansion is proportional to the superheat before entering the expansion machine as a first approximation. In the batch process, the superheat of the working fluid in front of the expansion machine is low at the beginning of the cycle and high at the end of the cycle. The same applies to overheating after relaxation. According to the invention, after expansion in the batch process, the overheating heat is decoupled by a heat exchanger at the outlet of the expansion machine and stored in another pair of vessels, called tempering vessels. Each of these two vessels can be intermittently connected to desuperheater 32 or preheater 45. In this way, superheat can be used to reduce unevenness of capacity flows in the preheater.

In accordance with the rise in temperature of the working fluid at the outlet of the expansion machine 10, the respectively connected desuperheater vessel 50a or 50b is filled from above with a heat transfer medium that is constantly heated. At the end of a cycle, the desuperheater tank is hottest at the top and the temperature decreases linearly with tank height to a first approximation. When discharging into the preheater 45, the warm heat transfer medium is withdrawn from the top of the superheater vessel 50a or 50b and fed to the preheater 45 according to the temperature present at the outlet of the heat transfer medium from the superheater. superheater 9. The temperature drop at the top outlet of desuperheater vessel 50a or 50b corresponds to the equally falling temperature at the heat transfer medium outlet of superheater 9 at a suitable mass flow rate of pump 15.

If one of the vessels 50a or 50b has been filled with hot heat transfer medium by the desuperheater 32, the vessel can be connected to the preheater 45 in an intermediate cycle by means of a valve 61. As a result, the heat transfer medium cold flows from preheater 45 through pumps 59 and 51 and check valves 57, 58 to desuperheater 32 and cools it before connecting to the second cold vessel. This prevents the hot heat transfer medium from the desuperheater from mixing with the cold heat transfer medium from the tank. Valves 53, 54, 55 and 56 are closed during the intermediate cycle.

With the heat engines according to the invention with a batch process, the implementation of triangular processes is possible according to claim 1 and the dependent claims. The increase in the electrical efficiency of the heat engine by approximately 30% to 50% and the use of inexpensive and durable components, such as vessels, valves, check valves and pumps, promise a very good marketability of the invention with payback times. Shorts for additional investment.

Figure 1 shows the construction of a prior art heat engine for stationary operation. From a heat source 21, the heated heat transfer medium reaches the superheater 9, from there to the evaporator 40, from there to the preheater 45 and from there via a pump 17 back to the heat source 21. In the superheater 9, evaporator 40 and preheater 45, the heat transfer medium gives up heat to the vaporizable working fluid. The liquid working fluid passes from the working fluid pump 15 to the preheater 45, from there to the evaporator 40 and from there in gaseous state to the superheater 9 and from there to the expansion machine 10, EM in which the working fluid it expands and performs work, which is carried out by the EM 10 to a generator 11, is released and converted into electrical energy and sent to electrical consumers. The vapor 32 expanded in the EM 10 is led to a condenser 12, where it is liquefied and collected in a collection vessel 13, SB. The liquid working fluid is delivered from the collecting tank 13 to the pump 15 as needed, which closes the circuit of the working fluid.

Figure 2 shows batch operation in a heat engine with a single vessel and therefore outside the present invention. The working fluid circuit is shown in this figure as a dashed line to distinguish it from the heat transfer medium circuit. The heat exchanger 40 combines a preheater, an evaporator and a superheater. Compared to Figure 1, a container 1a is inserted between heat source 21 and heat exchanger 40. Depending on the valve opening of valves 19 or 20, the container can be hydraulically connected to heat source 21 or to the heat exchanger 40, so that an exchange of heat transfer medium is then made possible. When the valve 19 is open, the hot heat transfer medium from the heat source 21 passes through the valve 19 at the top to the container 1a. The cooler heat transfer medium flows back from the bottom connection of vessel 1a via pump 17 to heat source 21. With valve 20 open, the heat transfer medium flows from the heat exchanger 40 through the pump 41 to the lower connection of the vessel 1a. From the upper connection of the vessel 1a, the heat transfer medium flows back to the heat exchanger 40 through the valve 20. A control device 44 detects the filling level of the liquid working fluid in the heat exchanger 40. (dashed lines) and uses the fill level setpoint deviation to control the mass flow of the working fluid in pump 15, for example. With this structure, the temperature of the working fluid at the inlet of the expansion machine 10 may drop sharply, which may lead to the EM 10 cooling down and the working fluid in the EM 10 condensing.

Figure 3 shows a structure for implementing batch operation with a separate preheater 45 and superheater 9. Similar to Figure 2, Figure 3 also shows a heat engine with a single canister and is therefore outside the scope of the present invention. A partial flow 33 of the hot heat transfer medium is led from the heat source 21 to the superheater 9, from there to the preheater 45 and via a pump 46 back to the heat source 21. The working fluid is pumped from the pump 15 as in the state of the art through the preheater 45, passed the evaporator 40 and the superheater 9 to the expansion machine EM 10. The working fluid is heated to high temperatures before entering the EM 10, which which reliably prevents the EM 10 from cooling down and condensation from forming in the EM 10.

Figure 4 shows the batch operation of a heat engine with a pair of vessels 1a and 1b. In addition to Figure 3, a second container 1b, two valves 21 and 22 and two non-return valves 18 and 27 have been added. Valves 21 and 22 allow the container 1b to be hydraulically coupled to the heat source 21 or to the evaporator 40 of analogous to the structure of the container 1a. While tank 1a is connected to heat source 21, for example, tank 1b is connected to evaporator 40. That is, valves 19 and 22 are open, valves 20 and 21 are closed. Once container 1a has been filled with a warm heat transfer medium and container 1b has given up its heat to the evaporator, the valves are switched such that container 1a is coupled to evaporator 40 and container 1b to the source. 21. That is, valves 20 and 21 are open, valves 19 and 22 are closed. Check valves 18 and 27 prevent the flows from mixing. The disadvantage of this structure is that the superheat that is still present in the working fluid after expansion in the EM 10 expansion machine is not used.

Figure 5 shows batch operation with a second pair of vessels 50a and 50b, which absorb superheat after expansion of the working fluid in expansion machine 10 and deliver it to preheater 45. Vessels 50a and 50b with the valves 53, 54, 55 and 56 are coupled to desuperheater 32 and preheater 45 in a similar way to vessels 1a and 1b, but here alternatively. Pump 51 provides the required mass flow through the desuperheater, pump 59 provides the required mass flow through preheater 45, and check valves 57 and 58 ensure that the circuits through desuperheater 32 and through preheater 45 are separate. With proper vessel design and mass flows in the preheater, evaporator, superheater, and desuperheater heat exchangers, there is very little dissipation. Assuming an ideal expansion engine, almost all of the exergy contained in the heat source 21 can be converted into mechanical energy with the structure. The triangle process can be achieved to a great extent.

Figure 6 shows an optimization of batch operation with flushing valves 60 and 61. If, for example, vessel 1a has given up its heat to evaporator 40, the evaporator has cooled down. If the second heated vessel 1b is now directly connected to the evaporator 40, the cold heat transfer medium in the evaporator 40 mixes with the hot one in the vessel 1b, which is disadvantageous for the process. To prevent mixing, the cold evaporator 40 is first connected to the heat source through valve 60 and heated. Valves 19 to 22 are closed. When evaporator 40 is heated, valve 60 closes and valves 19 and 22 open. Each time vessel 1a or 1b cools down, a rinse phase is set via valve 60. The same process applies to rinse valve 61. Here, each heating phase of desuperheater 32 is followed ^{by a through valve} 61 ^{, so that the superheated heat of the working fluid} can begin to enter the desuperheater 32 again in the new cycle.

Claims (7)

1. Heat engine with a heat source (21), an expansion machine (10), a condenser (12), a condensate collection vessel (13), a working fluid pump (15), an evaporator ( 40), a first container (1a) for heat transfer medium, a second container (1b) for heat transfer medium, a first pump for heat transfer medium (17), a second pump (41) for medium heat transfer, a first valve (19), a second valve (20), a third valve (21) and a fourth valve (22), wherein the heat engine is arranged in such a way that, during the operation of the heat engine, the first container (1a), in a first mode of operation of the heat engine, is hydraulically connected through the first valve (19) and the first pump (17) to the heat source (21) and, in a second operating mode of the thermal engine, it is connected to the evaporator (40) through the second valve (20) and the second pump (41), in where, in the first mode of operation of the heat engine, by connecting a first container (1a) to the heat source (21), the hottest heat transfer medium of the heat source (21) is filled in the part upper part of the first container (1a) and the cooler heat transfer medium is removed from the lower area of the first container (la) and returned to the heat source (21) and, in the second mode of operation of the heat engine, when the first container (1a) is connected to the evaporator (40), a medium is taken hotter heat transfer from the upper zone of the first container (1a), is led to the evaporator (40) and from the evaporator (40) it is pumped to the lower zone of the first container (1a) by means of the second pump ( 41), where the second container (1b), in the second operating mode of the heat engine, is hydraulically connected through the third valve (21) and the first pump (17) to the heat source (21) and, in the first mode of operation of the heat engine, is connected through the fourth valve (22) and the second pump (41) to the evaporator (40), where, in the second mode of operation of the heat engine, when the second container ( 1b) is connected to the heat source (21), the hotter heat transfer medium of the heat source (21) is filled to the top of the second container (1b) and the colder heat transfer medium it is removed from the lower area of the second container (1b) and taken to the heat source (21) and, in the first mode of operation of the heat engine, when the second container (1b) is connected to the evaporator (40), the hottest heat transfer medium is removed from the upper area of the second container (lb), it is taken to the evaporator (40) and is pumped by the evaporator (40) by means of the second pump (41) to the lower region of the second container (1b), the heat engine being arranged in such a way that one of the first and second containers (1a, 1b) is connected to the heat source (21) and the other of the first and second containers (1b, 1a) is connected to the evaporator (40) , so that the evaporation energy is transferred from one or the other of the first and second containers to the evaporator (40) and the expansion machine (10) continuously receives steam during the operation of the heat engine and the connection of the container to the heat source (21) and the evaporator (40), during the operation of the heat engine, after some time can be exchanged by means of the valves (19, 20, 21, 22). Heat engine according to claim 1, with a preheater (45), a superheater (9) and a further pump (46) for the heat transfer medium, where the working fluid is preheated by the preheater (45) during the operation of the heat engine, then flows to the evaporator (40), then to the superheater (9) and then to the expansion machine (10) and the transfer medium of heat flows through the additional pump (46) to the heat transfer medium directly from the heat source (21) into the superheater (9) and then into the preheater (45) and then through the pump ( 46) is pumped back to the heat source (21). Heat engine according to claim 1 or 2, with a desuperheater (32), a second pair of containers (50a, 50b) for heat transfer medium, valves (53, 54, 55, 56), two pumps (51, 59) for heat transfer medium, wherein the two containers (50a, 50b) with valves can be connected to the desuperheater (32) or to the preheater (45), where a first container (50a, 50b) is alternately connected to the preheater (45) and a second container (50b , 50a) is alternately connected to the desuperheater (32), where during the operation of the heat engine the desuperheater (32) is crossed by the working fluid of the expansion engine (10) and the residual heat of the working fluid in the desuperheater (32) is released to the heat transfer medium heat, the heat transfer medium is then pumped to the top of the first vessel and from the bottom of the first vessel by the pump back to the desuperheater (32), while the heat transfer medium is pumped from the preheater (45) by the second pump to the bottom of the second vessel and from the top of the second vessel back to the preheater (45), and where by means of the valves the hydraulic connection of the first and second containers with the desuperheater (32) and the preheater (45) can be exchanged. Heat engine according to claim 1 to 3, with a valve (60) between the heat source (21) and the evaporator (40), where the valve (60) allows heating the evaporator (40) with heat transfer medium directly from the heat source (21), where, during the operation of the heat engine, heating takes place after that the heat transfer medium of one of the two vessels (1a, 1b) that was connected to the evaporator (40) has finished cooling. Thermal engine according to claims 1 to 4, with a valve (61) between the desuperheater (32) and the preheater (45), where the valve allows to cool the desuperheater (32) with heat transfer medium directly from the preheater (45), where, during the operation of the thermal engine, the cooling takes place after the heating of the medium has been completed heat transfer from one of the two vessels that was connected to the preheater (45). Thermal engine according to claims 1 to 5, in which the expansion machine (10) is heated and insulated. Heat engine according to claims 1 to 6, wherein the first and second vessels (1a, 1b) are tapered at the top and bottom, the tapering allowing a turbulent entry of heat transfer medium into the vessel.