JPH06174194A - Lpg evaporator - Google Patents

Abstract

PURPOSE:To decrease a temperature difference relating to a heat source side of a tube bottom part by interposing an adjusting valve in a discharge flow path of discharging a drain condensed by a heat exchange with LPG from a shell bottom side, and controlling this adjusting valve to accumulate a predetermined amount of drain to stay in a shell internal bottom part. CONSTITUTION:LPG 5 introduced to a lower part header 3 is guided to an upper part header 2 through tubes 1 and evaporated by a heat exchange with steam 6 introduced from an upper side of a shell 4, and this evaporated gas 7 is collected through the upper part header 2. Here by a heat exchange of the LPG 5, steam is condensed and discharged as a drain 8. Here is interposed an adjusting valve 12 in a drain discharge flow path 11, and by controlling an opening of this adjusting valve 12 by a level control 14, a predetermined amount of the drain 8 is accumulated in the shell 4. In this way, the LPG 5 in a lower part of the tube 1 is heat exchanged with the drain 8, and the LPG 5 can be stably evaporated by decreasing a temperature difference relating to a heat source side.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an LPG evaporator.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional LPG evaporator. The tube 1 is surrounded by an upper header 2 and a lower header 3 which are communicated with each other by a plurality of vertically extending tubes 1. As described above, the shell 4 is arranged, and the room temperature and high pressure LPG introduced into the lower header 3 is introduced.
(Liquified Petroleum Gas:
(Liquefied petroleum gas) 5 is guided through the tube 1 to the upper header 2 to evaporate by heat exchange with the steam 6 introduced above the shell 4, and the evaporated gas 7 is recovered via the upper header 2. On the other hand, the drain 8 condensed by heat exchange with the LPG 5 is discharged from the lower side of the shell 4.

[0003]

However, since the temperature of the steam 6 is saturated in the shell 4 as shown in FIG. 4, the temperature of the steam 6 is at the inlet side (upper side of the shell).
Although it is substantially constant from the outlet side to the outlet side (lower side of the shell), the LPG5 is introduced at a temperature close to room temperature at the inlet side (lower side of the tube). There was a problem that the difference from the temperature became extremely large and the evaporation of LPG5 became unstable.

That is, as described above, the L
When the PG5 and the steam 6 are heat-exchanged, the heat transfer amount between the PG5 and the steam 6 does not necessarily follow the increase in the temperature difference, and as is clear from the boiling curve A shown in FIG. If the temperature exceeds the bundling point, the amount of heat transfer will decrease sharply. As shown in FIG. 6, a large bubble 9 called a vapor film is generated due to the rapid vaporization of the LPG 5 at the boundary between the inner peripheral surface of the tube 1 and the LPG 5, as shown in FIG. This is because the contact is blocked and the heat transfer rate is reduced.

Therefore, in the above-mentioned conventional LPG evaporator, the temperature difference between the LPG 5 and the steam 6 at the lower part of the tube 1 exceeds the maximum heat flux point, and unstable transition boiling between the nucleate boiling region and the film boiling region occurs. Since it is in the region, the heat transfer coefficient fluctuates due to the large bubbles 9 generated discontinuously, and the transition of the temperature on the inlet side of the LPG 5 fluctuates between the state shown by the solid line and the state shown by the chain double-dashed line in FIG. Could not be done stably.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an LPG evaporator which can stably evaporate LPG.

[0007]

According to the present invention, a shell is provided between an upper header and a lower header which are communicated with each other by a tube extending in a vertical direction so as to surround the tube,
While guiding the LPG introduced into the lower header to the upper header through the tube, the LPG is vaporized by heat exchange with steam introduced from the upper side of the shell, and the vaporized gas is recovered through the upper header, while the LPG is collected. In an LPG evaporator configured to discharge the drain condensed from heat exchange with the shell from the lower side of the shell, a drain discharge passage for discharging the drain from the lower side of the shell is provided with a regulating valve, and the drain is provided at a lower portion inside the shell. The LPG evaporator is characterized in that a level control for detecting a water level of the drain so that a fixed amount of the drain is retained and outputting a control signal to the adjusting valve is provided below the shell.

[0008]

Therefore, in the present invention, the LP introduced in the lower header
While introducing G through the tube to the upper header, it is evaporated by heat exchange with steam introduced from the upper side of the shell,
When the evaporated gas is recovered via the upper header, and the drain condensed by heat exchange with the LPG is discharged from the lower side of the shell, the adjusting valve provided in the drain discharge flow channel is controlled by the control signal from the level control. The degree of opening is adjusted, whereby the drain is retained in the lower part of the shell by a predetermined amount,
The LPG in the lower part of the tube exchanges heat with the drain. Therefore, the temperature difference between the heat source side (drain side) of the LPG in the lower part of the tube becomes small, and the LPG
The heat exchange between the drain and the drain is stably performed with a good heat transfer coefficient according to the temperature of the drain.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which parts designated by the same reference numerals as those in FIG. 3 represent the same parts.

In the LPG evaporator 10 constructed in substantially the same manner as the LPG evaporator shown in FIG. 3, the regulating valve 1 is provided in the drain discharge passage 11 for discharging the drain 8 from the lower side of the shell 4.
2 is provided, and a level control 14 that detects the water level of the drain 8 and outputs a control signal 13 to the adjusting valve 12 so that a predetermined amount of drain 8 is retained in the lower portion of the shell 4 is provided under the shell 4. Provide on the side.

Here, the set water level of the drain 8 is the tube 1 when the drain 8 is not retained in the shell 4.
The required range below the tube 1 where the temperature difference between the LPG 5 and the steam 6 flowing inside exceeds the maximum heat flux point and becomes the transition boiling region is set so that the water level can be surrounded by the accumulated drain 8.

In the figure, reference numeral 15 is an LPG introduction flow path for introducing LPG 5 into the lower header 3, 16 is an evaporative gas discharge path for exhausting evaporative gas 7 from the upper header 2, and 17 is a steam 6 on the upper side of the shell 4. The steam introduction flow path to introduce is shown.

Then, the LPG 5 introduced into the lower header 3
Is introduced into the upper header 2 through the tube 1 and evaporated by heat exchange with the steam 6 introduced from the upper side of the shell 4, and the vaporized gas 7 is recovered via the upper header 2 while the heat exchange with the LPG 5 is performed. When the condensed drain 8 is discharged from the lower side of the shell 4, the opening of the adjusting valve 12 provided in the drain discharge passage 11 is adjusted by the control signal 13 from the level control 14, and the drain 8 is moved to the shell 4
A predetermined amount is retained in the inner lower part. As a result, the LPG 5 in the lower part of the tube 1 exchanges heat with the drain 8, and the temperature difference between the heat source side (drain 8 side) becomes small as shown in FIG. The exchange is stably performed with a good heat transfer coefficient according to the temperature of the drain 8.

Therefore, according to the above embodiment, the temperature difference between the LPG 5 under the tube 1 and the heat source side can be reduced by retaining a predetermined amount of the drain 8 in the lower part of the shell 4, and thus the tube as in the prior art. Unstable LPG due to excessive temperature difference above the maximum heat flux point at the bottom of 1
It is possible to stably evaporate LPG5 since the evaporation of 5 is not performed.

Further, since the high temperature drain 8 is retained in the lower part of the shell 4 and is used as the heat source, the heat of the drain 8 which has been used as a conventional heat source but is discharged is effective. It is possible to efficiently evaporate LPG5 with a smaller amount of steam than the conventional one.

The LPG evaporator of the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0018]

According to the LPG evaporator of the present invention described above, various excellent effects as described below can be obtained.

(I) Since a predetermined amount of drain is retained in the lower part of the shell, the temperature difference between the LPG at the lower part of the tube and the heat source side can be made small. Unstable evaporation of LPG will not occur due to the excessive temperature difference, and LPG can be stably evaporated.

(II) Since the high-temperature drainage is retained in the lower part of the shell and is used as a heat source, the heat of the drainage, which has been useful as a heat source in the past, is effectively used. It is possible to efficiently vaporize LPG with a smaller amount of steam than before.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a graph showing the temperature change of LPG and the temperature change of steam in FIG.

FIG. 3 is a schematic view showing a conventional example.

FIG. 4 is a graph showing the temperature change of LPG and the temperature change of steam in FIG.

FIG. 5 is a graph showing a relationship of a heat transfer amount with respect to a temperature difference.

6 is a graph showing the boiling state of LPG in the transition boiling region of FIG.

[Explanation of symbols]

 1 Tube 2 Upper Header 3 Lower Header 4 Shell 5 LPG 6 Steam 7 Evaporative Gas 8 Drain 10 LPG Evaporator 11 Drain Discharge Channel 12 Control Valve 13 Control Signal 14 Level Control

Claims (1)

[Claims] 1. A shell is provided between an upper header and a lower header, which are connected by a vertically extending tube so as to surround the tube, and LPG introduced into the lower header is guided to the upper header through the tube. Between,
The shell was vaporized by heat exchange with steam introduced from the upper side of the shell, and the vaporized gas was recovered via the upper header, while the drain condensed by heat exchange with the LPG was discharged from the lower side of the shell. In the LPG evaporator, an adjustment valve is provided in the drain discharge flow path for discharging the drain from the lower side of the shell, and the water level of the drain is detected so that the predetermined amount of the drain is retained in the lower part of the shell to perform the adjustment. An LPG characterized in that a level control for outputting a control signal to a valve is provided below the shell.
Evaporator.