JPH0791211A - Evaporator for mixed medium - Google Patents

Abstract

PURPOSE:To reduce the sub-cooling degree of a working medium to improve the performance of the entire system of an evaporator by providing a preheater on the working medium inlet side of the evaporator, and by increasing the temperature of the working medium close to a boiling point by the preheater. CONSTITUTION:A heat source fluid is deprived of heat by a working fluid of liquid phase and the fluid is evaporated by an evaporator 1, and the steam and the liquid are separated from one another by a separator 2. A turbine 3 is rotated by the steam, and a generator 4 is driven by the steam. The exhausted steam is condensed by a condenser 5 and enters a drain pot 6, and then the steam passes through an absorber 7 and becomes a liquid which flows into an after-cooler 8. The liquid returns to the evaporator 1 via a cooler 10 and a preheater 11. The liquid is preheated by the preheater 11 close to a boiling point. The sub-cooling degree of the working fluid on the inlet of the evaporator 1 is thus reduced so as to transmit heat of evaporation on a larger electrothermal surface. The performance of the entire system of the evaporator is thus improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporator used in a thermal cycle using a non-azeotropic mixture as a working medium.

[0002]

2. Description of the Related Art A method for producing mechanical energy from a heat source by a heat cycle using a non-azeotropic mixture as a working medium is described, for example, in Japanese Patent Laid-Open No. 57-28819.

[0003]

It is well known that heat exchanger performance deteriorates in a heat cycle using a non-azeotropic mixture. The evaporator also causes performance degradation, but one of the possible causes is the effect of the inlet subcooling degree.
The degree of subcooling at the inlet is the difference between the actual temperature of the medium at the inlet of the working medium of the evaporator and the boiling point at the same pressure. Naturally, when the degree of subcool is large, a large heat transfer surface is used for heat transfer in the sensible heat section, which has poor heat transfer performance, so evaporation heat transfer with good heat transfer performance is performed with the remaining small area. However, the performance of the entire evaporator will deteriorate.

Therefore, an object of the present invention is to improve the performance of the evaporator by lowering the subcool degree at the working medium inlet of the evaporator in the heat cycle using the non-azeotropic mixture as the working medium.

[0005]

According to the present invention, a preheater is provided on the working medium inlet side of the evaporator to raise the temperature of the working medium to near the boiling point.

[0006]

By increasing the temperature of the working medium to near the boiling point with the preheater, the degree of subcooling of the working medium is lowered.
Therefore, the evaporation heat transfer is performed on the larger heat transfer surface, and the performance of the entire evaporator is improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a binary power generation system in which heat is recovered from a heat source fluid to generate electricity by a heat cycle using a non-azeotropic mixture as a working medium.

In this power generation system, the working medium in the liquid phase takes heat from the heat source fluid to evaporate in the evaporator (1), and the generated vapor proceeds to the separator (2) along with the unvaporized liquid. The separator (2) separates the vapor and the liquid. The steam is supplied to the turbine (3) and rotates the turbine (3) to drive a generator (4) directly connected to the turbine (3). The steam discharged from the turbine (3) proceeds to the condenser (5), where heat is taken by the cooling water to be condensed. The condensate and uncondensed vapor enter the drain pot (6). Drain pot (6)
The vapor and the liquid are separated at, the vapor is guided to the absorber (7),
The liquid flows into the aftercooler (8). Absorber (7)
Is supplied with the liquid at the working medium outlet of the evaporator (1) separated from the vapor by the separator (2) as an absorbing liquid, and the vapor introduced from the drain pot (6) is in the absorber (7). Then, the liquid absorbed by the absorbing liquid and discharged from the absorber (7) flows into the aftercooler (8). This liquid is cooled by the aftercooler (8), and by the pump (9)
It is returned to the evaporator (1) via the cooler (10) and the preheater (11).

The liquid from the aftercooler (8) flows from the separator (2) to the absorber (7) in the cooler (10).
The liquid going to is cooled, and in the preheater (11), it is preheated to near the boiling point by the heat source fluid. As the heat source fluid of the preheater (11), the heat source fluid discharged from the evaporator (1) may be reused depending on conditions such as temperature and flow rate, or
Other heat source fluids can also be used. Anyway,
The preheater (11) preheats the working medium supplied to the evaporator (1) to raise its temperature to near its boiling point.

Although the installation of the preheater (11) naturally increases the equipment cost, the mixed medium has a greater effect of preheating than the single medium, and therefore the heat exchanger performance is improved corresponding to the cost increase. Can be expected. Since the evaporator (1) is sprayed with aluminum on the heat transfer surface, the unit price per unit heat transfer area is high, but aluminum spraying is not necessary for heat exchange in the sensible heat section, and it is transferred to the preheater (11). No aluminum spraying on hot surface. In addition, the single medium is originally good in performance, and the rate of improvement in performance by installing the preheater is small, so performance improvement commensurate with the cost increase cannot be expected, but mixed media is poor in performance, so even a slight improvement can be expected. You can expect a big performance improvement.

[0011]

As described above, according to the present invention, in the heat cycle using a non-azeotropic mixture as the working medium, a preheater is provided on the working medium inlet side of the evaporator to bring the temperature of the working medium to near the boiling point. Since the temperature is raised, the degree of subcooling of the working medium at the inlet of the evaporator is lowered, and the evaporation heat is transferred at a larger heat transfer surface. Therefore, according to the present invention, the performance of the entire evaporator can be improved.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Evaporator 2 Separator 3 Turbine 4 Generator 5 Condenser 6 Drain pot 7 Absorber 8 Aftercooler 9 Pump 10 Cooler 11 Preheater

Claims (1)

[Claims] 1. An evaporator used in a heat cycle using a non-azeotropic mixture as a working medium, wherein a preheater is provided on the working medium inlet side of the evaporator to raise the temperature of the working medium to near the boiling point. An evaporator for mixed media, characterized in that