Electric heating device for cooling tower sump and cooling tower

Abstract

The application discloses an electric heating device for a cooling tower water collecting tray and a cooling tower. The electric heating device comprises a heater and a controller. The heater comprises a metal heating rod and a water level monitoring terminal, and is fixedly installed in the cooling tower water collecting tray as a whole. The controller comprises a main control unit, a water temperature control unit connected with the main control unit, a no-water power-off secondary unit and an overheating protection secondary unit connected with the water temperature control unit and in parallel with each other, and a heating operation unit connected with the no-water power-off secondary unit and the overheating protection secondary unit. The electric heating device further comprises an intermediate relay KA5 and a contactor KM1. The above-mentioned no-water stopping heating ensures that the electric heating rod is not exposed to the water level.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of construction, in particular to an electric heating device for a cooling tower sump and a cooling tower. BACKGROUND

[0002] In the cooling system of a water-cooled chiller and a packaged air conditioner, cooling water is needed. From the requirements of water saving and energy saving, the cooling water system must be recycled. The cooling tower is an important part of the circulating cooling water system. Due to the demand for refrigeration in winter in high-end hotels, commercial buildings, hospitals and other places, an electric heater is usually installed in the sump or the water collecting pool to prevent the water in the sump or the water collecting pool below the cooling tower from freezing and affecting the operation.

[0003] The electric heating of the cooling tower sump for construction uses a group of electric heating rods for heating. The control requirements of the electric heating in the electrical design of the building are left to the manufacturer, and the design only provides the power supply for power distribution. The electric heating rod is not required by the non-cooling tower product standard, and is often purchased separately by the cooling tower manufacturer, lacking the necessary electrical control requirements. In this way, the electrical control design of the electric heating is often lacking. In actual engineering, the secondary power distribution circuit design is simple, and the heater device appears dry burning phenomenon, and there is no service wiring to prevent overheating in the circuit control. Even if there are measures to prevent dry burning without water, the water level float is used to control the closing of the heater, and the float ball type water level switch increases the control link, reduces the safety and reliability of the line, at the same time, the up and down fluctuation of the float ball on the water surface of the sump is large, which is easy to form the frequent opening and closing of the heater causing the damage of the electrical control. In the start-up of the heating device, the outdoor air temperature is used for control, which causes the start-up of the electric heating device in the non-cooling tower non-operation state.

[0004] In the power distribution of the electric heating device of the cooling tower sump, the conventional electrical design only provides the power supply, and lacks the necessary design for its control. This unreasonable design lacking in design depth often hides the fire hazard of the cooling tower. SUMMARY

[0005] The technical problem solved by the present application is to provide an electric heating device for a cooling tower sump, which comprises a heater and a controller, the heater comprises a metal heating rod and a water level monitoring terminal, and is fixedly installed in the cooling tower sump as a whole; the controller comprises a main control unit, a water temperature control unit connected with the main control unit, a no-water power-off secondary unit and an overheating protection secondary unit connected with the water temperature control unit and in parallel with each other, and a heating operation unit connected with the no-water power-off secondary unit and the overheating protection secondary unit, and further comprises an intermediate relay KA5 and a contactor KM1; the metal heating rod and the water level monitoring terminal are connected to the no-water power-off secondary unit; the intermediate relay KA5 is connected to the no-water power-off secondary unit and controls the heating operation unit, and the contactor KM1 is connected to the heating operation unit and controls the main control unit; when the water level monitoring terminal is separated from water, the no-water power-off secondary unit is turned off, the intermediate relay KA5 loses power, the heating operation unit loses power, the contactor KM1 loses power, and the main control unit loses power; when the water level monitoring terminal is immersed in water, the no-water power-off secondary unit is turned on, the intermediate relay KA5 obtains power, the heating operation unit KA5 is always open, the contactor KM1 is powered on, and the main control unit works.

[0006] In order to solve the above problems, the present application provides a cooling tower comprising a sump and an electric heating device for heating the sump, the electric heating device comprises a heater and a controller, the heater comprises a metal heating rod and a water level monitoring terminal, and is fixedly installed in the cooling tower sump as a whole; the controller comprises a main control unit, a water temperature control unit connected with the main control unit, a no-water power-off secondary unit and an overheating protection secondary unit connected with the water temperature control unit and in parallel with each other, and a heating operation unit connected with the no-water power-off secondary unit and the overheating protection secondary unit, and further comprises an intermediate relay KA5 and a contactor KM1; the metal heating rod and the water level monitoring terminal are connected to the no-water power-off secondary unit; the intermediate relay KA5 is connected to the no-water power-off secondary unit and controls the heating operation unit, and the contactor KM1 is connected to the heating operation unit and controls the main control unit; when the water level monitoring terminal is separated from water, the no-water power-off secondary unit is turned off, the intermediate relay KA5 loses power, the heating operation unit loses power, the contactor KM1 loses power, and the main control unit loses power; when the water level monitoring terminal is immersed in water, the no-water power-off secondary unit is turned on, the intermediate relay KA5 obtains power, the heating operation unit KA5 is always open, the contactor KM1 is powered on, and the main control unit works.

[0007] The above structure sets a water level linkage function, which is a protection measure to prevent the heater from dry burning, ensures that the electric heating rod can only operate when it is installed in water, and needs to be cut off power supply once it leaves water, i.e. stops heating without water, and ensures that the electric heating rod will not be exposed outside the water level. The control mode of the electric heating device is not to control through the installation of an independent water level switch, but to focus on whether there is water when the electric heating rod is powered on.

[0008] Further, the temperature overheat protection function is also an optimization function of the device. The overheat protection of the electric heating rod body can prevent the electric heating rod from dry burning. When the electric heating rod is not immersed in water, the temperature of the electric heating rod rises quickly. The temperature is one of the three elements of fire combustion, and the overheat problem of the electric heating rod needs to be determined in time, and the power supply is automatically turned off. BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 is a structural diagram of a heater in an electric heating device for a cooling tower water collecting tray according to an embodiment of the present application. Figure 1 FIG. 2 is an electrical control structural diagram of a controller in the electric heating device for the cooling tower water collecting tray according to the embodiment of the present application.

[0010] FIG. 3 is a circuit structure of an embodiment of the controller in the electric heating device for the cooling tower water collecting tray according to the embodiment of the present application. Figure 2 FIG. 4 is a control principle diagram of the controller in the electric heating device for the cooling tower water collecting tray according to the embodiment of the present application.

[0011] FIG. 5 is a structural diagram of a heater in an electric heating device for a cooling tower water collecting tray according to another embodiment of the present application. Figure 3A FIG. 6 is an electrical control structural diagram of a controller in the electric heating device for the cooling tower water collecting tray according to the embodiment of the present application. Figure 3B FIG. 7 is a circuit structure of an embodiment of the controller in the electric heating device for the cooling tower water collecting tray according to the embodiment of the present application. Figure 3A is a power supply main loop of the electric heater, and Figure 3B is a control principle diagram. DETAILED DESCRIPTION

[0012] The electric heating device for the cooling tower water collecting tray and the cooling tower according to the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0013] The electric heating device for the cooling tower water collecting tray according to the embodiments of the present application includes a heater and a controller. Figure 1The diagram shows the structure of the heater 10 in the aforementioned electric heating device, including a base 18, a metal heating rod 11, and a water level monitoring terminal 12. In this specific embodiment, the heater 10 is horizontally installed in the water collection tray 19 of the cooling tower. The base 18 is used to install the metal heating rod 11. The controller of the electric heating device can be located inside the base or externally. In this specific embodiment, the water level monitoring terminal 12 is a conductive ring installed on the base 18. In other specific embodiments, as an alternative, the water level monitoring terminal 12 can also be a metal shell on the base, or a conductive device separately installed on the side wall of the water collection tray 19, and can also be installed vertically. The advantage of the water level monitoring terminal 12 being a conductive ring installed on the base 18 is that it can accurately monitor the water level in the water collection tray 19. This structure detects not the absolute water level, but the relative position of the water level with respect to the heater 10. Therefore, the aforementioned electric heating device and the cooling tower using it do not require on-site calibration of the alarm water level in the water collection pan 19 by workers during construction. As long as the heater 10 is correctly installed, a signal change can occur even when the water level is below the base 18 and there is still a certain distance between the heater and the metal heating rod 11, thus preventing the metal heating rod 11 from being exposed to the air and posing a fire hazard. Furthermore, even if the heater falls off or is damaged, it will not affect the normal operation of the aforementioned structure.

[0014] In one embodiment of the present invention, the heater 10 of the electric heater device is a resistance type, requiring consideration of three-phase balance and the use of a waterproof thermistor. The insulation resistance should be above 5MΩ at DC 500V (when cold). The heating rod has a withstand voltage of AC 1500V / min (when cold).

[0015] Appendix Figure 2 The diagram shows the electrical control structure of the controller 20 of the present invention. The controller 20 includes a main control unit 201, a water temperature control unit 206 connected to the main control unit 201, a water-out power-off secondary unit 203 and an overheat protection secondary unit 204 connected in parallel with the water temperature control unit, and a heating operation unit 202 connected to the water-out power-off secondary unit 203 and the overheat protection secondary unit 204. A manual control unit 207 can optionally be connected in series among the water temperature control units 206 connected to the main control unit 201.

[0016] Appendix Figure 3A With appendix Figure 3B The diagram shows a circuit structure of one embodiment of the controller 20 of the present invention, wherein... Figure 3A This is the main power supply circuit for the electric heater, with... Figure 3B It is a control principle diagram.

[0017] Continue to refer to the appendix Figure 3A With appendix Figure 3BThe water temperature control unit 206 is connected to the heater 10 and is used to automatically turn on or off the heater according to the water temperature. The waterless power-off secondary unit 203 and the overheat protection secondary unit 204, which are connected in parallel, are connected to the water temperature control unit 206 and the heating operation unit 202. The heating operation unit 202 will only start the heater 10 when the waterless power-off secondary unit 203 and the overheat protection secondary unit 204 are turned on, and otherwise the heater 10 will be turned off to prevent dry burning.

[0018] Continue to refer to the appendix Figure 3A With appendix Figure 3B The water temperature control unit 206 is used to limit the operating temperature range of the heater. In one embodiment of the invention, it includes intermediate relays KA1, KA3, and KA4. Intermediate relays KA3 and KA4 are connected to the water temperature control unit 206 and control intermediate relay KA1. Intermediate relay KA1 further controls the parallel-connected waterless power-off secondary unit 203 and overheat protection secondary unit 204. For example, when the temperature is below 3°C, intermediate relay KA3 is energized and conducts, while intermediate relay KA4 is de-energized; when the temperature is above or equal to 3°C but not above 15°C, intermediate relays KA3 and KA4 are de-energized; when the temperature is above 15°C, intermediate relay KA3 is de-energized, while intermediate relay KA4 is energized and conducts. When the temperature is below 3°C, the normally open contact of intermediate relay KA3 closes, the normally closed contact of intermediate relay KA4 closes, and intermediate relay KA1 becomes energized, controlling the closure of the normally open contacts of the parallel-connected waterless power-off secondary unit 203 and overheat protection secondary unit 204.

[0019] Continue to refer to the appendix Figure 3A With appendix Figure 3B The waterless power-off secondary unit 203 includes an intermediate relay KA5. When intermediate relay KA5 is conductive and its normally open contact is closed, the heating equipment operates. Similarly, when intermediate relay KA5 in the waterless power-off control unit is conductive and its normally open contact is closed, the heating equipment operates. When the temperature exceeds 15℃, the normally open contact of intermediate relay KA3 opens, the normally closed contact of intermediate relay KA4 opens, and intermediate relay KA1 is de-energized. This causes the normally open contact of KA1 in the parallel-connected waterless power-off secondary unit 203 and overheat protection secondary unit 204 to open, forcibly stopping the heating equipment. Through the coordinated operation of intermediate relays KA1, KA3, and KA4, the goal of automatic control based on temperature changes is achieved.

[0020] Continue to refer to the appendix Figure 3A With appendix Figure 3BThe waterless power-off secondary unit 203 includes an intermediate relay KA5 and a contactor KM1. The intermediate relay KA5 is connected to the waterless power-off secondary unit 203. When the positive and negative electrodes of the insulated metal of the device are separated from water, i.e. the water level monitoring terminal 12 is separated from water, the waterless power-off secondary unit 203 is turned off, the intermediate relay KA5 loses power, the heating operation unit 202 is powered off, the contactor KM1 loses power, and the main control unit 201 loses power. When the positive and negative electrodes of the insulated metal of the device are immersed in water, i.e. the water level monitoring terminal 12 is immersed in water, the waterless power-off secondary unit 203 is turned on, the intermediate relay KA5 is powered, the heating operation unit KA5 is turned on, the KM1 contactor unit is powered on, and is in a controllable operating state. The above-mentioned water level linkage function is a protective measure to prevent the heater 10 from being dry-burned, ensuring that the electric heating rod can only operate when it is installed in water. If it is separated from water, the power supply needs to be cut off, i.e. the waterless heating is stopped, to ensure that the electric heating rod will not be exposed outside the water level. This control mode of the electric heating device does not control by installing an independent water level switch, but focuses on whether there is water when the electric heating rod is powered on.

[0021] The over-temperature protection secondary unit 204 includes a waterproof thermistor (not shown) arranged on the heater 10, and the insulation resistance thereof is preferably above 5MΩ when DC500V (cold). The heating is stopped when the temperature exceeds a set temperature (e.g. 100°C), to prevent dry burning.

[0022] The above-mentioned temperature over-temperature protection function and low-temperature start function are also an optimized function of the device. The over-temperature protection of the electric heating rod itself can also prevent the electric heating rod from being dry-burned. When the electric heating rod is not immersed in water, its temperature rises quickly, and temperature is one of the three elements of fire combustion, so it is necessary to determine whether the electric heating rod is overheated in time and forcibly turn off the power supply. In circuit control, the service wiring for preventing overheating should not work alone to prevent causing new problems. This function should also be the highest priority. The low-temperature start function is to control the design to determine whether the water temperature is below 3°C before starting the power supply of the electric heating rod. The temperature sensor should not use the collection method of the ambient air temperature. The heating medium is water, not air environment, and the water temperature in the water needs to be used for judgment, which is more real and reliable. It does not need to be automatically linked to start, but can be manually judged and confirmed again. This is because the heating of the cooling tower sump is only to prevent the water in the sump from freezing, which will affect the function. Once the circulating cooling water system is running, the water temperature will naturally rise. Only at the initial stage of the operation of the cooling tower, the freezing of the water in the sump needs to be prevented.

[0023] With reference to the accompanying drawings Figure 3A With reference to the accompanying drawings Figure 3B Figure 3A Figure 3BThe controller 20 further comprises a manual control unit 207 between the main control unit 201 and the heating operation unit 202 for manual closing. The manual control unit 207 comprises a manual switch and an intermediate relay KA2. When the manual switch is in the automatic operation position, the temperature controller controls the energized conduction of the intermediate relays KA3 and KA4 according to the current cooling tower internal water temperature and the voltage comparison unit respectively. When the manual switch is in the manual control position, press the start button SB2, the intermediate relay KA2 is energized, and the heating circuit is turned on through the KA2 normally open contact latching, and the heating equipment operates. Press the stop button again, the intermediate relay KA2 is de-energized, the KA2 latching node is disconnected, and the heating equipment stops operating.

[0024] The above description is only preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, can make several improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. An electric heating device for cooling tower sump, comprising a heater and a controller, characterized in that: the heater comprises a metal heating rod and a water level monitoring terminal, and is fixedly installed in the cooling tower sump, and the heater is horizontally arranged in the cooling tower sump; the controller comprises a main control unit, a water temperature control unit connected with the main control unit, a no-water power-off secondary unit and an overheating protection secondary unit connected with the water temperature control unit and in parallel with each other, and a heating operation unit connected with the no-water power-off secondary unit and the overheating protection secondary unit, and further comprises an intermediate relay KA5 and a contactor KM1; the water temperature control unit further comprises an intermediate relay KA1, an intermediate relay KA3 and an intermediate relay KA4, the intermediate relay KA3 and the intermediate relay KA4 are connected to the temperature control unit and control the intermediate relay KA1, and the intermediate relay KA1 further controls the no-water power-off secondary unit and the overheating protection secondary unit in parallel with each other; when the temperature is lower than a low temperature threshold, the normally open contact of the intermediate relay KA3 is closed, the normally closed contact of the intermediate relay KA4 is closed, the intermediate relay KA1 is powered, the normally open contact of the intermediate relay KA1 is latched, and the normally open contact of the intermediate relay KA1 is closed; when the temperature is not lower than the low temperature threshold and not higher than a high temperature threshold, the normally open contact of the intermediate relay KA3 is opened, the normally closed contact of the intermediate relay KA4 is closed, the intermediate relay KA1 is still powered due to latching, and the normally open contact of the intermediate relay KA1 remains unchanged; when the temperature is higher than the high temperature threshold, the normally open contact of the intermediate relay KA3 is opened, the normally closed contact of the intermediate relay KA4 is opened, the intermediate relay KA1 loses power, the normally open contact of the intermediate relay KA1 is opened, and the heater is forced to stop running; the metal heating rod and the water level monitoring terminal are connected to the no-water power-off secondary unit; the intermediate relay KA5 is connected to the no-water power-off secondary unit and controls the heating operation unit, the contactor KM1 is connected to the heating operation unit and controls the main unit, when the water level monitoring terminal is in a state of being separated from water, the no-water power-off secondary unit is opened, the intermediate relay KA5 loses power, the heating operation unit loses power, the contactor KM1 loses power, and the main control unit loses power; when the water level monitoring terminal is in a state of being immersed in water, the no-water power-off secondary unit is turned on, the intermediate relay KA5 is powered, the heating operation unit KA5 is closed, the contactor KM1 is powered, and the main control unit works.

2. The apparatus of claim 1, wherein, The low temperature threshold is 3℃, and the high temperature threshold is 15℃.

3. The apparatus of claim 1, wherein, The controller further comprises a manual control unit connected in series between the main control unit and the water temperature control unit.

4. The apparatus of claim 3, wherein, The manual control unit comprises a manual switch and an intermediate relay KA2, when the manual switch is in a manual control position, a start button SB2 is pressed, the intermediate relay KA2 is powered, the heating circuit is turned on through the latching of the normally open contact of the intermediate relay KA2, and the heating device runs; a stop button SB1 is pressed, the intermediate relay KA2 loses power, the latching node of the KA2 is disconnected, and the heating circuit is turned off.

5. The apparatus of claim 1, wherein, The heater comprises a metal heating rod and a base for mounting the metal heating rod, and the water level monitoring terminal is a conductive ring or a metal shell arranged on the base.

6. A cooling tower comprising a sump and an electric heating device for heating the sump, the electric heating device comprising a heater and a controller, characterized in that: The heater comprises a metal heating rod and a water level monitoring terminal, and is fixedly installed in the sump of the cooling tower, and the heater is horizontally arranged in the sump of the cooling tower; The controller comprises a main control unit, a water temperature control unit connected to the main control unit, a no-water power-off secondary unit and an overheating protection secondary unit connected to the water temperature control unit and in parallel with each other, and a heating operation unit connected to the no-water power-off secondary unit and the overheating protection secondary unit, and further comprises an intermediate relay KA5 and a contactor KM1; The water temperature control unit further comprises an intermediate relay KA1, an intermediate relay KA3 and an intermediate relay KA4, the intermediate relay KA3 and the intermediate relay KA4 are connected to the temperature control unit and control the intermediate relay KA1, and the intermediate relay KA1 further controls the no-water power-off secondary unit and the overheating protection secondary unit in parallel with each other; When the temperature is lower than the low temperature threshold, the normally open contact of the intermediate relay KA3 is closed, the normally closed contact of the intermediate relay KA4 is closed, the intermediate relay KA1 is powered, the normally open contact of the intermediate relay KA1 is latched, and the normally open contact of the intermediate relay KA1 is closed; When the temperature is not lower than the low temperature threshold and not higher than the high temperature threshold, the normally open contact of the intermediate relay KA3 is opened, the normally closed contact of the intermediate relay KA4 is closed, the intermediate relay KA1 is still powered due to latching, and the normally open contact of the intermediate relay KA1 remains unchanged; When the temperature is higher than the high temperature threshold, the normally open contact of the intermediate relay KA3 is opened, the normally closed contact of the intermediate relay KA4 is opened, the intermediate relay KA1 loses power, the normally open contact of the intermediate relay KA1 is opened, and the heater is forced to stop running; The metal heating rod and the water level monitoring terminal are connected to the no-water power-off secondary unit; The intermediate relay KA5 is connected to the no-water power-off secondary unit and controls the heating operation unit, the contactor KM1 is connected to the heating operation unit and controls the main unit, when the water level monitoring terminal is in a state of being separated from water, the no-water power-off secondary unit is opened, the intermediate relay KA5 loses power, the heating operation unit loses power, the contactor KM1 loses power, and the main control unit loses power; when the water level monitoring terminal is in a state of being immersed in water, the no-water power-off secondary unit is turned on, the intermediate relay KA5 obtains power, the heating operation unit KA5 is closed, the contactor KM1 is powered, and the main control unit works.

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