JPH0468298A - Flow-down liquid film type evaporator - Google Patents

Abstract

PURPOSE:To detect the temperature of cold water quickly and detect the quick reduction of water temperature in an evaporator quickly when the flow of cold water is stopped by a method wherein the temperature sensitive unit of a water temperature sensor is inserted into the vicinity of the outlet ports of one or several pieces of a plurality of downstream side heat transfer tubes or upstream side heat transfer tubes. CONSTITUTION:A water temperature sensor 10 is arranged in a water chamber 9, in which water in the end of a downflow liquid film type evaporator is turned, while the temperature sensitive unit 11 of the sensor 10 is inserted into one of a plurality of heat transfer tubes 42 at the downstream side of the water chamber 9. When the flow of cold water is stopped during refrigerantion cycle operation, heat exchange between stagnated water and refrigerant is continued and, therefore, the temperature of the cold water is reduced quickly. The temperature sensitive unit 11 of the water temperature sensor 10 is inserted into the downstream side heat transfer tube 42, in which heat exchange between the water and the refrigerant is being effected, and therefore, the reduction of the cold water temperature is detected sooner than a case wherein the temperature sensitive unit of the water temperature sensor is arranged in the other part in which heat exchange is not being effected whereby a signal can be taken out before the start of the refrigeration of the water due to the reduction of the cold water temperature and the operation of the refrigeration cycle can be stopped.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an apparatus for supplying cold water for cooling to various devices or for supplying cold water to a fan coil unit for air conditioning, etc. This invention relates to the structure of a falling film evaporator that evaporates a liquid film and cools water with the heat of vaporization.

[Prior Art] Fig. 2 shows a conventional falling film evaporator. A liquid or gas-liquid two-phase refrigerant (for example, fluorocarbon) flows into the evaporator shell 1 from a liquid refrigerant port 2 in the upper part thereof.

The liquid refrigerant receiving plate 3 has a large number of heat transfer tubes 4 inside the evaporator shell 1.
There are holes through which □, 4□, and 43 are loosely penetrated, and the liquid refrigerant that entered from the inlet 2 flows down in a thin film form from the holes in the receiving plate 3 over the outer surfaces of these heat exchanger tubes, and flows inside these heat exchanger tubes. The liquid refrigerant evaporates and removes the heat from the cold water 5 flowing through it, thereby cooling the cold water. The refrigerant gasified by heat exchange flows out from the refrigerant gas outlet 8.

A refrigeration cycle (not shown) is constructed to liquefy the gas refrigerant flowing out from the gas outlet 8 and return it to the liquid refrigerant population 2. On the other hand, the cold water 5 enters from the cold water population 6, passes through the heat transfer tube and is cooled as described above, then exits the evaporator from the cold water tank lower, flows to the object to be cooled (load), circulates, and returns to the cold water population. Return to 6.

The flow of cold water in the evaporator is from water chamber 1 immediately after cold water population 6.
6 to a plurality of heat transfer tubes 4□, merges in a water chamber 9, further branches to a plurality of downstream heat transfer tubes 4□, further merges in a water chamber 17, and further branches to a plurality of heat transfer tubes 4. After that, water chamber 18
The cold water flows out from the lower cold water outlet.

The cold water temperature is controlled by the water temperature detected by a water temperature sensor placed upstream of the cold water intake 6 or downstream of the cold water outlet lower in the cold water flow path outside the falling film evaporator. It was common in the past.

Regarding conventional examples of falling film type evaporators, for example, see Japanese Patent Application Laid-open No. 1983
Please refer to No.-21261 and No. 62-266389.

[Problem M to be solved by the invention] In the prior art, the water temperature sensor is placed in the cold water flow path outside the falling film evaporator, which causes a delay in water temperature detection and makes it difficult to control the cold water temperature. Undesirable. In particular, if the flow of cold water stops during refrigeration cycle operation, the temperature of the stagnant water in the falling film evaporator will rapidly drop due to the cooling effect of the refrigerant. Temperature sensors placed outside the evaporator cannot detect the above-mentioned rapid drop in water temperature due to the stoppage of the flow of chilled water, so protective measures such as stopping the operation of the refrigeration cycle cannot be taken promptly. This often led to water freezing inside the falling film evaporator.

An object of the present invention is to eliminate the delay in detecting the temperature of cold water in a falling film evaporator, and to promptly detect a rapid drop in the water temperature in the evaporator when the flow of cold water stops. It's about making it possible.

[Means for Solving the Problems] In order to achieve the above object, a falling film evaporator of the present invention has the configuration described in each claim.

[Function] Since the water temperature sensor is inserted into the heat transfer tube where heat exchange between water and refrigerant takes place, there is no delay in detecting the water temperature, and a drop in water temperature when cold water is stopped can be immediately and directly detected.

In addition, if the water temperature sensor is inserted near the inlet of the heat exchanger tube on the downstream side from the water chamber, during normal operation when cold water is flowing, it will be possible to detect the uniform temperature of the cold water in the water chamber coming from the upstream heat exchanger tube. Therefore, it is not affected by the increase in pipe resistance of the downstream heat exchanger tube due to the insertion of the water temperature sensor and the resulting decrease in flow rate.

Water temperature detection does not produce biased errors.

[Example] Hereinafter, one example of the falling film type evaporator of the present invention will be described. Since its overall configuration and functions are the same as those shown in FIG. 2, redundant explanations will be omitted, and particularly the parts related to this embodiment will be explained with reference to the partially enlarged cross-sectional view shown in FIG. 1.

In FIG. 1, a water temperature sensor 10 is disposed in a water chamber 9 at the end of the falling film evaporator where water turns, and the temperature sensor 11 is connected to a plurality of heat transfer tubes on the downstream side of the water chamber 9. 1 out of 4
It is inserted inside the book and near its entrance. Since the temperature sensing part of the water temperature sensor is located inside the heat transfer tube in this manner, the temperature of the cold water flowing therethrough can be detected without delay while the evaporator is in operation.

During operation of the refrigeration cycle, when the flow of chilled water stops, heat exchange between the stagnant water and the refrigerant continues, resulting in a rapid drop in the temperature of the chilled water. The temperature-sensing part 11 of the water temperature sensor 10 is inserted into the downstream heat exchanger tube 4□ where heat exchange between the water and the refrigerant is taking place. It is possible to detect the temperature earlier than when the temperature-sensing part of the water temperature sensor is placed in a part (for example, inside the water chamber 9), and to take out a signal and stop the operation of the refrigeration cycle before the water begins to freeze due to a drop in the cold water temperature. can.

Of course, when the flow of cold water stops, the inside of the downstream heat exchanger tube 4□ and the inside of the upstream heat exchanger tube 41 are uniformly cooled, so the water temperature sensor temperature sensing part 11 is cooled inside the downstream heat exchanger tube 42. Even if it is not inserted into the upstream heat exchanger tube 4□, the same effect can be obtained regarding water temperature detection when the flow of cold water is stopped.

On the other hand, when cold water is flowing in a normal refrigeration cycle operating state, the flow rate of the cold water is approximately uniform within the plurality of heat transfer tubes 41 on the upstream side, and the water temperature within the water chamber 9 where they join is also approximately uniform. . However, a plurality of heat exchanger tubes 4□ on the downstream side of the water chamber 9
When comparing the heat exchanger tubes with the water temperature sensor inserted and the heat exchanger tubes without the water temperature sensor inserted, the former heat exchanger tube's internal flow area is narrowed by the amount of the water temperature sensor. Therefore, the flow rate of cold water flowing through the former heat exchanger tube is smaller than the flow rate of cold water flowing through the latter heat exchanger tube, so the temperature of the cold water at the outlet of the former heat exchanger tube is lower than that at the outlet of the latter heat exchanger tube. Become. Therefore, when the water temperature sensor is arranged to detect the water temperature near the outlet inside one of the heat exchanger tubes 4□, the average cold water temperature for all of the plurality of heat exchanger tubes 4□ A temperature lower than that will be detected, and an error will occur in the detection.

On the other hand, as in this embodiment, the heat exchanger tube 4 on the downstream side of the water chamber 9
When the water temperature sensor temperature sensing part is placed inside near the inlet of the heat exchanger tube 2, the water temperature sensor is located near the inlet of the upstream heat exchanger tube 4, which is still hardly affected by the inequality in the flow path area of the downstream heat exchanger tube 4. The uniform cold water temperature coming from the water chamber 9 can be detected,
Moreover, there is no delay in detection response. From the perspective of detecting a uniform chilled water temperature, it is better to place the temperature-sensing part of the water temperature sensor inside the water chamber 9, but since heat exchange between the water and the refrigerant takes place within the heat transfer tube, such a water temperature The arrangement of the sensors deteriorates the responsiveness of cold water humidity detection, and in particular, it becomes impossible to promptly detect a drop in the cold water temperature when the flow of cold water is stopped.

Furthermore, in this example, the setting value of the water temperature sensor is adjusted appropriately (for example, if the water temperature sensor's temperature sensing part is located in the center of the water path in the falling film evaporator, the water temperature will drop by half of the water temperature difference between the inlet and the outlet). By adjusting the water temperature to a certain level (adjusted to a certain temperature), it is possible to protect against the risk of freezing due to a decrease in the cold water flow rate or a decrease in the cold water outlet temperature due to a decrease in the cold water inlet temperature.

In the above embodiment, the water temperature sensor provided in the lower water chamber 9 was inserted into the interior near the inlet of the downstream heat transfer tube 42 of the water chamber 9, but instead, The temperature sensitive part of the water temperature sensor provided in the water chamber 17 is connected to the downstream heat exchanger tube 4. Even if it is inserted inside near the entrance of the
effect can be achieved.

Note that even when the water temperature sensor is arranged such that its temperature sensing part is inserted inside one of the plurality of heat transfer tubes 41 on the upstream side of the water chamber 17 and near the outlet, the refrigeration cycle During operation, the purpose of detecting the temperature of flowing cold water without delay and the purpose of early detecting a decrease in the temperature of stagnant cold water when the flow of cold water is stopped can be achieved. However, in this case, for the same reason as mentioned above, there are differences in flow path area and cold water flow rate between the plurality of upstream heat exchanger tubes 41 with and without a water temperature sensor inserted. There will be a difference in the temperature of the cold water at the outlet of the heat transfer tube 41, and the detection by the water temperature sensor will have an error. In order to detect a uniform chilled water temperature with almost no errors, as in the embodiment described above, a water temperature sensor is placed near the population inside the heat exchanger tube on the downstream side of the water chamber where the upstream heat exchanger tubes merge. It is better to insert a warm part.

In short, during refrigeration cycle operation, the temperature of the cold water flowing in the falling film evaporator can be detected without delay, and when the flow of cold water has stopped, the temperature drop of the stagnant water in the evaporator can be immediately detected. In this case, the water temperature sensor may be inserted near the outlet of the upstream heat transfer tube or into the downstream heat transfer tube. In the above detection, if you wish to further detect uniform cold water temperature, it is recommended to insert a water temperature sensor near the inlet in the downstream heat transfer tube of the water chamber where the upstream heat transfer tubes merge. .

It is preferable to provide an appropriate spacer between the insertion portion of the water temperature sensor into the heat transfer tube and the heat transfer tube to prevent contact between the water temperature sensor and the heat transfer tube.

Water temperature sensors may be inserted into not only one of the plurality of heat transfer tubes but also some of them, and the water temperature may be detected based on their detection outputs.

For the purpose of preventing water from freezing, a gas-charged thermostat may be used as a water temperature sensor to detect the lowest water temperature.

As a protection means for preventing damage to the evaporator due to freezing of the cold water, a means may be provided to detect an increase in water chamber pressure due to the growth of ice in the evaporator and stop the operation of the refrigeration cycle.

[Effects of the Invention] According to the present invention, the temperature of cold water flowing through a falling film evaporator can be detected without delay, and when the flow of cold water stops, a drop in water temperature can be detected at an early stage. It can contribute to preventing freezing of cold water in the evaporator.

[Brief explanation of the drawing]

FIG. 1 is a partial longitudinal sectional view of a falling film evaporator according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a falling film evaporator according to the prior art. 2...Liquid refrigerant population 4□, 4□, 4. ...Heat transfer tube 5...Cold water 6...Cold water lower part...
Chilled water outlet 8...Gas refrigerant outlet 9.16, 17
, 18...Water chamber 10...Water temperature sensor 11...Temperature sensing section 1 person Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1 Water that has been divided into a plurality of upstream heat exchanger tubes is combined in a water chamber, and then divided into a plurality of downstream heat exchanger tubes that are connected to the water chamber, and the water is divided into a plurality of downstream heat exchanger tubes that are connected to the water chamber. In a falling film evaporator, water flowing inside a heat transfer tube is cooled by causing a refrigerant liquid to flow down in a thin film on the outer surface to transfer evaporative heat.
A water temperature sensor is installed inside one or some of the plurality of downstream heat exchanger tubes, or inside near the outlet of one or some of the plurality of upstream heat exchanger tubes. A falling film type evaporator characterized by having a part inserted therein. 2. The falling film evaporator according to claim 1, wherein a temperature sensitive part of a water temperature sensor is inserted inside near the inlet of one or some of the plurality of downstream heat transfer tubes. 3. The falling film evaporator according to claim 1 or 2, wherein the water chamber makes a U-turn on the water coming out of the plurality of upstream heat transfer tubes and causes it to flow into the plurality of downstream heat transfer tubes. .