JP2513935B2 - Low boiling medium system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low boiling point medium system such as a heat pump or a binary cycle, and is intended to improve the performance when a binary mixture medium is used as a working fluid.

[0002]

2. Description of the Related Art A binary power generation system shown in FIG. 3 will be described as an example of a low boiling point medium system. An evaporator 2, a turbine 4, a condenser 6 and a medium pump 8 are connected in series to form a closed loop 10. There is. The working fluid circulating in the closed loop 10 first evaporates by removing heat from the heat source fluid in the evaporator 2, and the generated steam is supplied to the turbine 4. This steam expands in the turbine 4 and serves to drive the generator 12. The steam discharged from the turbine 4 is deprived of heat by the cooling water in the condenser 6 and condensed.
The condensate is sent to the evaporator 2 again by the circulation pump 8.

By the way, in such a heat cycle such as a binary cycle or a heat pump, a Lorentz cycle may be constituted by using a non-azeotropic mixed medium as a working fluid in order to improve efficiency. For example, the binary cycle is basically a Rankine cycle, and when the working fluid is a single medium, as shown in FIG.
-Indicates isothermal changes. However, Freon R
When a mixed medium such as a mixture of 123 and R22 is used as the working fluid, the saturation temperature changes, the evaporation temperature rises in the evaporator 2 and the condensation temperature decreases in the condenser 6, as shown in FIG. . This forms a Lorentz cycle and improves system efficiency.

FIG. 6 shows the simplest temperature-composition relationship of a two-component liquid-vapor system with the horizontal axis representing the mole fraction of the low-boiling component. G and L are single phases, respectively, a gas phase and a liquid phase, and a region of L + G is a two-phase region where a liquid and a vapor coexist. If the temperature of a liquid mixture of 60 mol% (mol fraction = 0.60) of the low boilers is increased under constant pressure, the change in this system can be considered along a straight line ab'cd "e.
At low temperatures, only a liquid phase exists, but a vapor phase appears at point b '. The composition of this vapor phase is given by the point b ", and the two conjugate phases are connected by an equilibrium connection line b" b 'in the figure. Increasing the temperature will produce more steam, in which case
Due to the high concentration of low boiling components in the vapor, this component is relatively reduced in the liquid phase, the composition of the liquid changes along b'c'd ', while the composition of the vapor is b "c" It changes along the d ". At the temperature t ° C, the total composition of the system in the two-phase region is represented by the point c, but the vapor composition and the liquid composition are both ends of the equilibrium connecting line passing through the point c," Given by points and c'points. The relative amounts of the two phases are determined from the principle of leverage in physics. That is, the ratio of the number of moles of vapor to liquid is represented by the ratio of the length of cc 'to c "c. As the temperature is further increased, more and more vapor is generated, and d"
At the point, the liquid phase almost disappears, and when the temperature becomes higher than this, the liquid phase disappears and only the vapor phase (d "point) remains. Even if the temperature is further raised (along d" e) Does not happen.

[0005]

In the vapor phase of the working fluid at the outlet of the condenser, the low boiling point component has the highest concentration in the system, and the gas having the low boiling point component stays near the condensation heat transfer surface. Therefore, in FIG.
As shown in (3), the low-boiling component exists in the condenser in the same manner as the non-condensable gas that impedes mass transfer and heat transfer, and reduces the heat transfer performance.

Therefore, the object of the present invention is to:
The purpose is to reduce the concentration of uncondensed low-boiling component gas in the condenser and to achieve the same effect as eliminating non-condensed gas.

[0007]

Means for Solving the Problems The present invention provides an evaporator,
Evaporation in a low-boiling-point medium system in which a thermal cycle is configured by circulating a non-azeotropic mixed medium of a binary system with different boiling points as a working fluid in a closed loop formed by connecting an expansion engine, a condenser and a circulation pump in series. The evaporation residual liquid at the outlet of the condenser is sent to the outlet side of the condenser in the form of gas or liquid.

[0008]

The evaporative residual liquid at the outlet of the evaporator has the lowest concentration of the low boiling component in the system. Therefore, by feeding it to the outlet side of the condenser, the evaporative residual liquid absorbs the uncondensed low boiling component gas. As a result, the concentration of uncondensed low-boiling components in the gas phase is lowered, mass transfer and heat transfer are facilitated, and the heat transfer performance of the condenser is improved.

[0009]

EXAMPLE A case of application to the above-mentioned binary power generation system shown in FIG. 3 will be described as an example. As shown in FIG. 1, a mist separator 14 is connected to the outlet side of the evaporator 2 and its downcomer 16 is connected to the mist separator 14. It is connected to the inlet side of the evaporator 2. An aftercooler 18 for separating low boiling point component gas is installed on the outlet side of the condenser 6, and a lower outlet of the mist separator 14 and the aftercooler 18 are connected by a liquid return pipe 20. Since the liquid return pipe 20 is for sending the evaporation residual liquid to the outlet side of the condenser 6, it is installed at the outlet of the condenser 6 in addition to being connected to the after cooler 18 as in the illustrated embodiment. It may be connected to a drain pot (not shown) or the like.

The working fluid exiting the evaporator 2 is separated by a mist separator 14 into steam and evaporation residual liquid. Steam turbine 4
After being supplied to the above and working, the condenser 6 takes away heat from the cooling water to condense (). The evaporation residual liquid separated from the steam by the mist separator 14 is returned from the downcomer 16 to the liquid return pipe.
It is sent to the aftercooler 18 through 20.

The low-boiling component concentrations of the evaporator 2 and the condenser 6 in this case are as shown in FIG. The circled numbers in the figure correspond to those in FIG. 1, and indicate the following items, respectively.
Condenser outlet liquid, evaporator inlet liquid, evaporator outlet liquid,
Evaporator outlet gas, condenser inlet (or overall average) gas, condenser outlet gas. As can be understood from FIG. 2, the evaporator outlet liquid has the lowest low-boiling component concentration in the system. On the other hand, at the outlet of the condenser 6, the concentration of the low-boiling component gas in the state indicated by is very high. Therefore, aftercooler
The low-boiling component gas is absorbed by the evaporation residual liquid sent into the inside of 18. Although there are gases in various states of ~ in the condenser, the gas in the state where the low boiling point component concentration is the highest is selectively absorbed. In this way, by sending the evaporation residual liquid at the evaporator outlet having the lowest low boiling component concentration to the condenser outlet side, the low boiling component gas is absorbed in this evaporation residual liquid, and as a result, uncondensed low The boiling component gas concentration is reduced, and the heat transfer performance of the condenser is improved.

[0012]

As described above, according to the present invention, in a low-boiling-point medium system that uses a binary mixed medium as a working fluid, the evaporation residual liquid at the evaporator outlet is gas or liquid at the condenser outlet side. Since it is designed to be fed in, the evaporator outlet liquid showing the lowest low boiling point component concentration in the system is sent to the condenser outlet to absorb the low boiling point component gas and reduce the low boiling point component gas concentration The heat transfer performance of the vessel can be improved.

[Brief description of drawings]

FIG. 1 is a flow sheet of a binary power generation system showing an embodiment of the present invention.

FIG. 2 is a vapor-liquid equilibrium diagram of a working fluid in the binary power generation system of FIG.

FIG. 3 is a flow sheet of a binary power generation system showing a conventional example.

FIG. 4 is a TS diagram of Rankine cycle.

FIG. 5 is a TS diagram of the Lorentz cycle.

FIG. 6 is a vapor-liquid equilibrium diagram showing a temperature-composition relationship of a binary mixed medium.

FIG. 7 is a cross-sectional view of a condensation heat transfer surface.

[Explanation of symbols]

 2 Evaporator 4 Turbine 6 Condenser 8 Circulation pump 10 Closed loop 12 Generator 14 Mist separator 16 Downcomer 18 Aftercooler 20 Liquid return pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-67975 (JP, A)

Claims (1)

(57) [Claims] 1. A thermal cycle is constituted by circulating a binary non-azeotropic mixed medium having different boiling points as a working fluid in a closed loop formed by connecting an evaporator, an expansion engine, a condenser and a circulation pump in series. In the low boiling point medium system,
A low-boiling-point medium system characterized in that the evaporation residual liquid at the outlet of the evaporator is sent in a gas or liquid form to the outlet side of the condenser.