JP2011122742A - Water supply preheater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase heat absorbing amount in a heat exchanger which preheats supplied water and improves the efficiency of a boiler. <P>SOLUTION: The water supply preheater includes: two water supply tanks constituted of a room temperature water supply tank 10 and a hot water supply tank 7; and a preheating route 5 interconnecting the room temperature water supply tank 10 and the hot water supply tank 7 and having a water pump 9 and a heat exchanger 3 installed in the middle. A water level control device 12 maintaining a water level at predetermined height is provided in the room temperature water supply tank 10. Connection piping 6 interconnecting the lower part of the room temperature water supply tank 10 and the lower part of the hot water supply tank 7 and having a check valve 11 installed in the middle and enabling only a flow from the room temperature water supply tank side to the hot water supply tank side and a water return pipe 8 having one end connected to the lower part of the hot water supply tank 7 and the other end opened on the upper side of the water level position controlled by the water level control device 12 within the room temperature water supply tank 10 are provided between the room temperature water supply tank 10 and the hot water supply tank 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water supply preheating device that preheats water in the middle of a water supply path to a boiler.

  Japanese Patent Laid-Open No. 2006-68687 describes a device that preheats water supplied to a boiler. Here, a configuration is described in which water in a water supply tank for room temperature water supply is heated with a heat exchanger, and the heated hot water is injected into the tank to be flushed and then supplied to the boiler. ing. In the configuration where the water in the hot water supply tank is supplied to the boiler, if the water in the hot water supply tank runs out and water cannot be supplied to the boiler, the water level in the boiler drops abnormally, causing the water pipe in the boiler to overheat. Being dangerous. Therefore, it is necessary to always store a predetermined amount or more of water in the hot water supply tank.

  In the invention described in Japanese Patent Laid-Open No. 2006-68687, the hot water supply tank and the room temperature water supply tank are connected by a communication pipe, and excess water in the hot water supply water tank is returned to the normal temperature water supply tank through the communication pipe. The flow rate of the water pump sent from the water supply tank to the hot water supply tank is made larger than the amount of water used by the boiler. If the amount of water sent from the normal temperature water supply tank to the hot water supply tank is larger than the amount of water used by the boiler, the water level in the hot water supply tank can always be kept high, and excess water can be returned to the normal temperature water supply tank through the communication pipe. It is possible to prevent the water level in the hot water supply tank from becoming too high. And the communication pipe that connects the hot water supply tank and the room temperature water supply tank makes the water level in the hot water supply tank higher than that in the room temperature water supply tank by keeping the hot water supply tank side higher. It is possible to prevent water from flowing into the hot water supply tank through the communication pipe.

The heat exchanger that preheats the feed water is installed in the exhaust gas passage for passing the exhaust gas discharged from the boiler, and heat is effectively recovered by recovering the heat from the exhaust gas after the boiler absorbs the heat. Since it can be utilized, the efficiency of the boiler is improved. The exhaust gas temperature in the heat exchanger section installed downstream of the boiler is lower than the temperature in the boiler section, but the temperature of the feed water is even lower, so heat is exchanged with low-temperature feed water. It can be recovered.
In this case, when the feed water temperature supplied to the heat exchanger increases, the amount of heat that can be recovered by the heat exchanger decreases. Therefore, the feed water temperature sent from the room temperature feed tank to the heat exchanger should be low. However, when the amount of water sent to the hot water supply tank through the heat exchanger is increased as described in JP 2006-68687 A and the excess water in the hot water supply tank is returned to the normal temperature water supply tank, A large amount of hot water will circulate from the tank to the room temperature water supply tank, and the warm water in the hottest water supply tank will circulate, so that the water temperature of the room temperature water supply tank will increase. Then, the amount of heat that can be absorbed by the heat exchanger is reduced, and the hot water temperature of the hot water supply tank is lowered, so that the efficiency of the boiler is lowered. In addition, when the water flow rate of the water pump sent to the heat exchanger is increased, the power consumption by the water pump increases.

JP 2006-68687 A

  The problem to be solved by the present invention is to provide a feed water preheating device capable of increasing the amount of heat absorption in a heat exchanger for preheating feed water and improving the efficiency of the boiler.

  Two water tanks, consisting of a normal temperature water supply tank and a hot water supply tank, are connected between the normal temperature water supply tank and the hot water supply tank, and has a preheating path with a water pump and a heat exchanger installed on the way. The exchanger exchanges heat between the exhaust gas whose temperature has decreased and the water whose temperature is lower than that of the exhaust gas, and heats the room temperature water stored in the room temperature water supply tank with the heat exchanger to make warm water, In the water supply preheating device in which the heated hot water is temporarily stored in the hot water supply tank and the hot water is supplied from the hot water supply tank to the boiler, the normal temperature water supply tank has a water level adjusting device for maintaining the water level at a predetermined height, Between the water supply tank and the hot water supply tank, the lower part of the normal temperature water supply tank and the lower part of the hot water supply tank are connected, and only the flow from the normal temperature water supply tank side to the hot water supply water tank side is possible on the way. A connecting pipe with a stop valve, one end connected to the lower part of the hot water supply tank, and the other end opened above the water level position adjusted by the water level adjusting device in the room temperature water supply tank Install a water pipe. The hot water pump for supplying hot water in the hot water supply tank to the boiler controls the water supply based on the water level in the boiler, and the water pumping capacity of the water pump is equal to or slightly the same as that of the hot water pump. Try to increase.

  Even when the water level in the hot water supply tank becomes low, the water in the room temperature water supply tank is sent to the hot water supply tank through the connecting pipe, so that there is no problem in water supply to the boiler. Therefore, it is not necessary to greatly increase the amount of water sent to the hot water supply tank through the heat exchanger, and to reduce the amount of hot water returned from the hot water supply tank to the normal temperature water supply tank by reducing the amount of water supplied to the hot water supply tank. Can do. When the amount of circulating water from the hot water supply tank to the normal temperature water supply tank decreases, the rise in the water temperature in the normal temperature water supply tank can be suppressed. In addition, since the connecting pipe and the return water pipe are connected to the bottom of the hot water supply tank, the hot water that returns to the normal temperature water supply tank through the return water pipe is the one with the lowest temperature in the hot water supply tank. Water temperature rise in the tank can be suppressed. Since the amount of heat absorbed by the heat exchanger can be increased by keeping the temperature of the water sent from the room temperature water supply tank to the heat exchanger low, the efficiency of the boiler increases. Furthermore, by reducing the amount of water flow through the water pump, the power consumption of the water pump can be reduced.

Flow diagram of a feed water preheating device implementing the present invention

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow diagram of a feed water preheating device for preheating water supplied to the boiler 1. A normal temperature water supply tank 10 provided with a water level adjusting device 12 and a hot water supply tank 7 for accumulating hot water heated by the heat exchanger 3 are provided in the water supply path to the boiler. The water level adjusting device 12 of the room temperature water supply tank 10 supplies water to the room temperature water supply tank 10 when the water level in the room temperature water supply tank 10 becomes lower than the set water level, and when the water level in the room temperature water supply tank 10 becomes higher than the set water level, Water supply to the tank 10 is stopped, and a float valve is widely used as a water level adjusting device because it is inexpensive.

  A preheating path 5 for preheating water before supply to the boiler 1 is connected to the lower part of the room temperature water supply tank 10, and the preheating path 5 is provided with a water pump 9 and a heat exchanger 3 in the middle. The other end of 5 is connected to a hot water supply tank 7 for storing hot water heated by the heat exchanger 3. The heat exchanger 3 is installed in the exhaust gas passage 2 and further recovers heat from the exhaust gas whose temperature has been lowered by the boiler 1 absorbing heat. The preheating path 5 operates the water pump 9 to send the water stored in the room temperature water supply tank 10 to the heat exchanger 3, and heat water heated by exchanging heat with the exhaust gas in the heat exchanger is used in the hot water supply tank. Accumulate on 7. A boiler water supply pipe 13 for supplying water to the boiler 1 is connected to the lower part of the hot water supply tank 7, and a hot water pump 4 is provided in the middle of the boiler water supply pipe 13. It is assumed that the water pump 9 and the hot water pump 4 have the same water passing capacity or the water pump 9 having a slightly higher water passing capacity (warm water pump capacity ≦ water pump capacity <warm water pump capacity × 1.1).

  The hot water pump 4 supplies water when the water level in the boiler decreases, stops the water supply when the water level in the boiler rises, maintains the water level in the boiler at a predetermined value, and repeats a short operation and a short stop. ing. In the case of the water pump 9, warm water is stored in the hot water supply tank 7, and even if the water level in the hot water supply tank 7 fluctuates slightly, there is no significant effect. And since the water flow capacity of the water pump 9 is equal to the water flow capacity of the hot water pump 4 or slightly higher than the water flow capacity of the hot water pump 4, it enters the hot water supply tank 7 through the preheating path 5 within a certain time. The amount of warm water is equal to or greater than the amount of warm water sent from the warm water supply tank 7 to the boiler 1. During normal operation, the water level in the warm water supply tank 7 does not drop significantly, and surplus warm water is generated.

  In addition, a connecting pipe 6 that connects the lower part of the room temperature water supply tank 10 and the lower part of the hot water supply tank 7 is provided, and a check valve 11 that flows only from the normal temperature water supply tank 10 to the hot water supply tank 7 is provided in the middle of the connection pipe 6. Provide. Then, one end is connected to the lower part of the hot water supply tank 7, and the other end is provided in the room temperature water supply tank 10 and provided with a return water pipe 8 opened at a position higher than the set water level of the water level adjusting device 12. Since the connecting pipe 6 and the return water pipe 8 are both connected to the lower part of the hot water supply tank 7, the connecting pipe 6 and the return water pipe 8 are joined and then connected to the hot water supply tank 7. Alternatively, the normal temperature water supply tank 10 and the hot water supply tank 7 may be configured as an integral type partitioned by a partition wall, and the return water pipe 8 may be configured to penetrate the partition walls of the normal temperature water supply tank 10 and the hot water supply tank 7.

  Since the connection pipe 6 is provided with the check valve 11, the hot water does not flow from the hot water supply tank 7 to the room temperature water supply tank 10 through the connection pipe 6, and the temperature in the hot water supply tank 7 is higher than the water level in the room temperature water supply tank 10. Only when the water level is low, the water in the room temperature water supply tank 10 flows to the hot water supply tank 7 through the connecting pipe 6. Since the return water pipe 8 has an opening in the room temperature water supply tank 10 higher than the set water level of the water level adjustment device 12, the water level in the warm water supply tank is higher than the opening of the return water pipe in the room temperature water supply tank 10. The water in the hot water supply tank 7 flows to the room temperature water supply tank 10 through the return water pipe 8. The water level in the room temperature water supply tank 10 stops when the water level becomes higher than the set water level of the water level adjusting device 12, so that the water level in the room temperature water supply tank 10 does not rise to the opening of the return water pipe 8. Ten water does not flow to the hot water supply tank 7 through the return water pipe 8.

  Since the water level in the room temperature water supply tank 10 is adjusted by the water level adjusting device 12, the water level is almost constant. The water level in the hot water supply tank 7 is determined by the balance between the amount of water that the water pump 9 sends to the hot water supply tank 7 and the amount of water that the hot water pump 4 sends to the boiler 1. The water pump 9 has a water flow capacity equivalent to or slightly larger than that of the hot water supply tank 7, and the hot water supply tank 7 starts and stops, whereas the water pump 9 operates continuously. It is. Therefore, in the normal case, the amount of water sent from the preheating path 5 to the hot water supply tank 7 is larger than the amount of water sent from the hot water supply tank 7 to the boiler 1. Then, when the water level becomes high in the hot water supply tank 7 and the water level in the hot water supply tank 7 becomes higher than the opening of the return water pipe 8 provided in the room temperature water supply tank 10, the hot water is supplied through the return water pipe 8. The water in the water supply tank 7 is sent to the room temperature water supply tank 10.

  In the case of a system that supplies water from the hot water supply tank 7 to the boiler 1 in order to supply the preheated hot water to the hot water supply tank 7, when the excess hot water in the hot water supply tank 7 is returned to the normal temperature supply water tank 10, the water temperature in the normal temperature supply water tank is Will rise. Since the heat exchanger 3 recovers heat from the exhaust gas whose temperature has been lowered by the boiler 1, when the water temperature in the room temperature water supply tank 10 rises, the temperature difference from the exhaust gas is reduced and recovered by the heat exchanger 3. The amount of heat that can be reduced. When the amount of recovered heat in the heat exchanger 3 decreases, the temperature of the hot water in the hot water supply tank 7 decreases and the efficiency of the boiler decreases. Therefore, the amount of hot water that circulates from the hot water supply tank 7 to the room temperature water supply tank 10 should be smaller. Good. However, when the water level in the hot water supply tank 7 is lowered and water supply to the boiler 1 cannot be performed, a large effect is caused such that many devices related to the boiler cannot be operated. The one with excessive capacity was used for the required water supply amount, and the amount of excess hot water was increased.

  However, according to the configuration of the present invention, when the water level in the hot water supply tank 7 is lowered, the water in the room temperature water supply tank 10 is sent to the hot water supply tank 7 through the connecting pipe 6. For this reason, an abnormality occurs in which the capacity of the water pump 9 is reduced, and even if the amount of water flowed by the hot water pump 4 is larger than the amount of water flowed by the water pump 9, there is a problem that water supply to the boiler 1 is hindered Must not. Therefore, it is not necessary to increase the water flow rate of the water pump 9 unnecessarily, and the water flow rate of the water pump 9 can be reduced. If the amount of water flow through the water pump 9 is reduced as compared with the prior art, the amount of hot water circulating from the hot water supply tank 7 to the room temperature water supply tank 10 is reduced, and an increase in water temperature due to the circulation of hot water to the room temperature water supply tank 10 can be suppressed. If the water temperature of the room temperature water supply tank 10 is low, the amount of heat absorbed by the heat exchanger 3 increases, so that the efficiency of the boiler can be improved.

  The return water pipe 8 is connected to the lower part of the hot water supply tank 7 so that the hot water is taken out from the portion having the lowest temperature in the hot water supply tank 7. By doing in this way, the amount of heat transfer from the hot water supply tank 7 to the normal temperature water supply tank 10 can be suppressed to a minimum, and a reduction in boiler efficiency can be prevented. Furthermore, since the amount of power consumed by the water pump 9 can be reduced by reducing the amount of water flow through the water pump 9, energy can be saved.

1 boiler
2 Exhaust gas passage
3 heat exchanger
4 Hot water pump
5 Preheating route
6 Connection piping
7 Warm water supply tank
8 Return pipe
9 Water pump
10 Room temperature water supply tank
11 Check valve 12 Water level adjusting device 13 Boiler feed pipe

Claims (2)

Two water tanks, consisting of a normal temperature water supply tank and a hot water supply tank, are connected between the normal temperature water supply tank and the hot water supply tank, and has a preheating path with a water pump and a heat exchanger installed on the way. The exchanger exchanges heat between the exhaust gas whose temperature has decreased and the water whose temperature is lower than that of the exhaust gas, and heats the room temperature water stored in the room temperature water supply tank with the heat exchanger to make warm water, In the water supply preheating device in which the heated hot water is temporarily stored in the hot water supply tank and the hot water is supplied from the hot water supply tank to the boiler, the normal temperature water supply tank has a water level adjusting device for maintaining the water level at a predetermined height, Between the water supply tank and the hot water supply tank, the lower part of the normal temperature water supply tank and the lower part of the hot water supply tank are connected, and only the flow from the normal temperature water supply tank side to the hot water supply water tank side is possible on the way. A connecting pipe with a stop valve, one end connected to the lower part of the hot water supply tank, and the other end opened above the water level position adjusted by the water level adjusting device in the room temperature water supply tank A water supply preheating device characterized in that a water pipe is provided.   2. The water supply preheating apparatus according to claim 1, wherein the water pump installed in the preheating path basically operates continuously during boiler operation, and the hot water pump for supplying hot water in the hot water supply tank to the boiler is a boiler. The water supply preheating device is characterized in that the water supply is controlled based on the internal water level, and the water flow capacity of the water pump is set to be equal to or slightly larger than the water flow capacity of the hot water pump. .

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