JPS5939123Y2 - Lubricating oil heating device for Rankine cycle system - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a lubricating oil heating device for expelling liquid refrigerant trapped in a sealed container of a Rankine cycle expander and refrigerant dissolved in lubricating oil.

FIG. 1 is a diagram showing an example of a conventional solar heat-utilizing Rankine cycle.

In the figure, solar heat is collected by a heat collector 1 and stored in a heat storage tank 2.

An evaporator 3 is installed in this heat storage tank 2, and evaporates the working fluid in liquid state (usually Freon R, 114, R11, etc. is used), which is pumped to a high pressure by a pump 9 and sent. to produce relatively high temperature and high pressure steam, which is led to the expander 6 and expanded to a low pressure,
The expanded vapor is condensed and liquefied in a condenser 8, and the liquefied working fluid is sent to the evaporator 3 by a pump 9, thereby forming a Rankine cycle.

In the Rankine cycle, it is possible to extract power from the output shaft and drive any load by expanding relatively high-temperature, high-pressure steam to a low pressure in the expander, but this expander 6 can leak working fluid. It is usually housed in a sealed container 4 that has both the functions of prevention, lubricating oil tank, and oil separation, and lubricating oil 7 is stored in the sealed container.

The operation of the Rankine cycle system that uses solar heat as described above is often limited to a few hours during the day on sunny days from early summer to early autumn when there is a large amount of solar heat input and relatively high temperature heat can be collected. It is well known that the period during which the expander is stopped is relatively long.

The expander is stopped by closing the valves 12 and 13 provided at the inlet and outlet of the evaporator 3, but if left in this condition for a long time, the expander 6, condenser 8, and lubricating oil 7 will be damaged. The temperature decreases to a temperature close to that of the surrounding air.

The fluorocarbon-based refrigerant used as the working fluid in the Rankine cycle has a strong affinity with oil, so it dissolves into the lubricating oil, but this tendency becomes more pronounced as the oil temperature decreases, and the temperature of the lubricating oil becomes higher than that of the fluorocarbon gas. Almost 1 when near the saturation temperature
It is clear from the dissolution curve of fluorocarbon gas R114 shown in FIG. 2 that nearly 00% fluorocarbon gas dissolution can occur.

In this way, if the expander is started with a large amount of fluorocarbon gas dissolved in the lubricating oil in the sealed container while the expander is stopped, the viscosity coefficient will drop significantly due to the dissolution of the fluorocarbon gas, and the fluorocarbon gas will be present at the oil pump suction port. The bearing may seize due to poor lubrication due to a drop in pump function due to rapid evaporation of lubricating oil, leakage of lubricating oil due to oil foaming caused by boiling of lubricating oil in a sealed container, etc.

For this reason, in the conventional Rankine cycle system shown in Fig. 1, a crankcase heater 1o is attached to the outside or inside of the sealed container, and the power supply 11 is turned on at least 12 hours before the start of operation to heat the oil in the sealed container. The fluorocarbon gas dissolved in the oil is expelled.

Therefore, in the conventional Rankine cycle system shown in Fig. 1, even after the expander is stopped, it is necessary to control the crankcase heater in anticipation of the next start of operation, which not only makes the device complicated and expensive, but also Heater 10
It has the disadvantage of consuming excess power due to VC.

This idea uses a portion of the heat deposits stored in the heat storage tank 2 to the lubricating oil in the sealed container and expels the fluorocarbon gas dissolved in the lubricating oil, thereby achieving the same effect as a crankcase heater and using auxiliary power. This is an attempt to improve the above-mentioned drawbacks of the conventional products by obtaining the product without using it.

Fig. 3 shows a Rankine cycle system showing an embodiment of this invention.
The evaporator is installed inside the evaporator, 16.17 is a pipe connecting the condenser 14 and evaporator 15 to form a closed loop, 18 is a valve for controlling the flow rate, and inside the pipe is a condensable fluid such as CFC gas. is included.

What happens when the expander is stopped? While the temperature To of M oil gradually decreases, the temperature T of the heat storage tank
Since w is raised until it reaches the temperature required to operate the Rankine cycle, Tw>T.

It can be considered that the situation is as follows.

Therefore, if the evaporator 15 is installed at a lower position than the condenser 14, as shown in FIG.
The condensed liquid flows through the pipe 17 due to gravity, reaches the evaporator 15, takes heat from the heat storage tank, and evaporates.

The evaporated gas passes through the pipe 16, reaches the condenser 14, and is condensed, repeating a natural circulation process, and the heat in the heat storage tank can be applied to the lubricating oil 7, so that the fluorocarbon gas dissolved in the lubricating oil can be The expelling action can be achieved without external auxiliary input, and the above-mentioned drawbacks of the conventional method can be improved.

Although this invention has been described as an example for a Rankine cycle system using solar heat, it can of course be used for a Rankine cycle system using other heat sources such as exhaust heat, and it can also be used with an expander. It can also be applied to refrigerant compressors driven by.

As explained above, this idea achieves lubrication by naturally circulating a condensable fluid such as fluorocarbon gas between the condenser installed in the lubricating oil of the expander or compressor and the evaporator installed in the heat storage tank. Since the oil can be heated, it is possible to expel the fluorocarbon gas dissolved in the lubricating oil in the expander and compressor when the engine is stopped without using any external auxiliary input.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a conventional solar heat-based Rankine cycle system, Fig. 2 is a characteristic diagram showing the dissolution curve of fluorocarbon gas R114 and lubricating oil, and Fig. 3 is a solar heat-based Rankine cycle system according to an embodiment of this invention. FIG. In the figure, 1 is a solar heat collector, 2 is a heat storage tank, 3 is an evaporator, 4 is a sealed container, 6 is an expander, 7 is lubricating oil, 8 is a condenser, 10 is a crankcase heater, and 14 is a condenser. , 15
16.17 shows the evaporator, and 16.17 shows the piping of the natural circulation circuit.

Claims (1)

[Scope of utility model registration request] The heat medium fluid is evaporated by an evaporator installed on the heat source side, and the gas is expanded by an expansion device to extract power.
and a Rankine cycle system in which the gas is liquefied in a condenser and sent to the evaporator,
A heat exchanger is installed inside the lubricating oil reservoir of the expander or the like in which the heat transfer fluid is mixed, and on the heat source side so that the lubricating oil reservoir side is at a higher position than the other. A Rankine cycle characterized in that heat exchangers are connected to each other to form a closed loop, a condensable heating medium is enclosed in the closed loop, and the lubricating oil can be heated by the heat exchanger. System lubricating oil heating device.