Heat exchange system of boiler

Abstract

The heat exchange system comprises a heat source main path, a cold source main path, a heat source branch path and a cold source branch path, a main path valve is arranged on the heat source main path, and an inlet and an outlet of the heat source branch path are connected with the upstream and the downstream of the main path valve of the heat source main path respectively; the heat source branch comprises an inlet heat source branch, a heat exchanger, a middle heat source branch and an outlet heat source branch which are communicated in sequence; the inlet heat source branch is provided with an inlet valve to control communication with the upstream of the heat source main path, and the outlet heat source branch is provided with an outlet valve to control communication with the downstream of the heat source main path. The heat source in the heat exchanger can be kept in a flowing state all the time, the sterilization and disinfection effect is guaranteed, and meanwhile it can be guaranteed that a user uses the heat source after heat exchange at any time.

Description

Technical Field

[0001] The invention relates to the field of heat exchange, and in particular to a heat exchange system of a boiler. Background Art

[0002] Energy is the material basis for the survival and development of modern society, and it is also a strong guarantee for the rapid and sustainable development of the national economy. In recent years, with the development of industry and the improvement of people's living standards, my country's energy consumption has also increased day by day. However, my country is a country with energy shortages. In order to meet the energy needs of the rapid development of the national economy, the safe and efficient use of multi-level energy is urgent.

[0003] Energy-saving and emission-reduction technologies are gaining more and more attention in energy-intensive fields such as thermal engineering, refrigeration, and the power industry, and are especially widely used in heat exchangers, refrigerators, power station boilers and other equipment. The utilization of waste heat resources in my country's industrial field, especially high-temperature and medium-temperature waste heat resources, has achieved remarkable results. However, compared with developed countries, there is still a certain gap in the utilization of low-temperature waste heat resources in the industrial field. With the continuous deepening of energy-saving work, the utilization of low-temperature waste heat resources has become a hot spot and difficulty in energy-saving work. Therefore, the recovery and utilization of various low-grade waste heat in the industrial production process is of great significance, which can not only help solve my country's energy problems, but also effectively reduce environmental pollution. Compared with ORC cycle power generation, direct contact heat exchangers have advantages that other heat exchange methods cannot match, such as simple structure, not easy to scale, and high heat transfer efficiency. Moreover, due to the disturbance of gas-liquid two-phase flow, its heat transfer coefficient can be 20-100 times larger than that of single-phase flow. Therefore, direct contact heat exchangers are one of the most effective waste heat recovery and utilization. With the continuous development of direct contact heat transfer theory, direct contact heat exchangers have been widely used in actual production such as air conditioning cold storage, medium and low temperature recovery systems, seawater desalination, energy process conversion, salt solution evaporation and crystallization, and wastewater treatment.

[0004] In the heat exchange system, shell and tube heat exchangers are widely used in industries such as chemical industry, petroleum, refrigeration, nuclear energy and power. Due to the global energy crisis, in order to reduce energy consumption, the demand for heat exchangers in industrial production is increasing, and the quality requirements for heat exchangers are also getting higher and higher. In recent decades, although compact heat exchangers (plate, plate-fin, press-welded plate heat exchangers, etc.), heat pipe heat exchangers, direct contact heat exchangers, etc. have developed rapidly, shell and tube heat exchangers still dominate production and usage due to their high reliability and wide adaptability. According to relevant statistics, the use of shell and tube heat exchangers in industrial devices still accounts for about 70% of all heat exchangers.

[0005] At present, the water output by the heat exchanger of the heat exchange system is usually kept warm and circulated at a certain temperature to reduce the risk of microbial growth. However, for a specific user, there is also a requirement for low-temperature water according to the special needs of process equipment and cleaning. Therefore, it is necessary to set up a heat exchange system to provide users with water at a certain temperature and ensure the sterilization function of a heat exchanger during use. Summary of the invention

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A heat exchange system for exchanging heat between cold and hot sources comprises a heat source main circuit, a cold source main circuit, a heat source branch circuit and a cold source branch circuit, wherein a main circuit valve is arranged on the heat source main circuit, and an inlet and an outlet of the heat source branch circuit are respectively connected to the upstream and downstream of the main circuit valve of the heat source main circuit; the heat source branch circuit comprises an inlet heat source branch circuit, a heat exchanger, an intermediate heat source branch circuit and an outlet heat source branch circuit which are connected in sequence; the inlet heat source branch circuit is provided with an inlet valve to control communication with the upstream of the heat source main circuit, and the outlet heat source branch circuit is provided with an outlet valve to control communication with the downstream of the heat source main circuit.

[0007] As an improvement, the cold source branch is connected to the cold source main circuit, and the cold source branch is connected to the heat exchanger inlet pipe to exchange heat with the heat source entering the heat exchanger.

[0008] As an improvement, a flow regulating valve is provided on the inlet pipe of the heat exchanger.

[0009] As an improvement, a temperature sensor is provided on the intermediate heat source branch.

[0010] As an improvement, the temperature sensor is data-connected to the flow regulating valve and the controller.

[0011] As an improvement, the outlet heat source branch is connected to a user pipeline, and a user valve is provided on the user pipeline.

[0012] As an improvement, the heat exchanger is a shell and tube heat exchanger, with the heat source passing through the tube side and the cold source passing through the shell side.

[0013] As an improvement, the heat source is hot water and the cold source is gas.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention can keep the heat source in the heat exchanger in a flowing state, inhibit the growth of bacteria, ensure the sterilization and disinfection effect, and also ensure that the user can use the heat source at a certain temperature after heat exchange at any time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the heat exchange system of the present invention. DETAILED DESCRIPTION

[0016] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0017] Figure 1 The heat exchange system of the present invention is disclosed. Figure 1 As shown, a heat exchange system for heat exchange between cold and hot sources includes a heat source main circuit 1, a cold source main circuit 2, a heat source branch circuit and a cold source branch circuit 4. A main circuit valve 5 is arranged on the heat source main circuit, and an inlet 6 and an outlet 7 of the heat source branch circuit are respectively connected to the upstream and downstream of the main circuit valve of the heat source main circuit; the heat source branch circuit includes an inlet heat source branch circuit 31, a heat exchanger 8, an intermediate heat source branch circuit 32 and an outlet heat source branch circuit 33 which are connected in sequence; the inlet heat source branch circuit is provided with an inlet valve 9 to control the connection with the upstream of the heat source main circuit, and the outlet heat source branch circuit is provided with an outlet valve 10 to control the connection with the downstream of the heat source main circuit.

[0018] The present invention can keep the heat source in the heat exchanger in a flowing state, inhibit the growth of bacteria, ensure the sterilization and disinfection effect, and also ensure that the user can use the heat source at a certain temperature after heat exchange at any time.

[0019] As an improvement, the cold source branch 4 is connected to the cold source main path 2, and the cold source branch 4 is connected to the heat exchanger inlet pipe to exchange heat with the heat source entering the heat exchanger.

[0020] As an improvement, the heat source comes from a boiler.

[0021] As an improvement, a flow regulating valve 12 is provided on the cold source branch 4 to regulate the cold source flow entering the heat exchanger 8 .

[0022] As an improvement, a temperature sensor is provided on the intermediate heat source branch for detecting the temperature of the heat source output by the heat exchanger 5 .

[0023] As an improvement, the temperature sensor and the flow regulating valve are data-connected with a controller, and the controller controls the opening of the flow regulating valve according to the detected temperature.

[0024] As an improvement, when the detected temperature exceeds the set data, the controller controls the flow control valve opening to increase, thereby increasing the cold source flow. As an improvement, when the detected temperature is lower than the set data, the controller controls the flow control valve opening to decrease, thereby reducing the cold source flow.

[0025] As an improvement, the outlet heat source branch is connected to a user pipeline 13, and a user valve 11 is provided on the user pipeline.

[0026] As an improvement, the heat exchanger is a shell and tube heat exchanger, with the heat source passing through the tube side and the cold source passing through the shell side.

[0027] As an improvement, the heat source is hot water, preferably from a boiler, and the cold source is gas. The hot air after the air is heated directly enters the user's home.

[0028] As an improvement, the output temperature range of the heat source of the heat exchanger 5 is preferably 65°C-75°C.

[0029] like Figure 1 As shown, the shell and tube heat exchanger is arranged vertically, and a plurality of baffles are arranged inside the shell and tube.

[0030] As an improvement, the shell side and the tube side are countercurrent flows. Along the flow direction of the fluid in the tube side, the spacing of the baffles increases continuously from the tube side inlet to the middle of the tube side. Then from the middle of the tube side to the tube side outlet, the spacing of the baffles decreases continuously. Because in the countercurrent process, the heat exchange of the shell side and the tube side per unit length along the flow process of the fluid is relatively uniform, so that the overall heat exchange effect is the best. However, it was found in experiments and simulations that the heat exchange in the middle is significantly greater than the heat exchange at the tube side inlet and outlet. Therefore, by changing the spacing of the baffles, the heat exchange area between the tube side fluid and the shell side fluid in the baffles also changes. Therefore, the uneven heat exchange is compensated by the change in area, thereby further improving the heat exchange efficiency.

[0031] As an improvement, along the flow direction of the fluid in the tube, from the tube entrance to the middle of the tube, the distance between the baffles increases. Then, from the middle of the tube to the tube exit, the distance between the baffles decreases. The above changes in the range can make the heat transfer per unit length of the entire fluid movement more uniform, further improving the heat transfer efficiency.

[0032] A plurality of horizontal baffles are arranged in the shell of the shell and tube heat exchanger 5, and the baffles include a circular baffle located in the center of the shell and annular baffles located around the shell; the circular baffles and the annular baffles are arranged adjacent to each other, and along the upward flow direction of the gas, the area of ​​the annular baffles first gradually increases and then gradually decreases, and the area of ​​the circular baffles first gradually decreases and then gradually increases.

[0033] During the research process, it was found that the heat transfer of the baffles of the traditional heat exchanger is uneven in the cross-section in the direction of gas upward flow, and the heat transfer effect is better in the parts around the bottom inlet and outlet, and the heat transfer effect is better in the middle center than in the surrounding edges. In the present invention, along the upward flow direction of the gas, the area of ​​the circular baffles and the area of ​​the annular baffles in the baffle group change. The fluid in the shell side gradually moves closer to the center in the middle, so that the heat exchange tubes around the shell at the center of the fluid strengthen the heat exchange, and then the heat exchange tubes at the center of the shell at the upper and lower ends strengthen the heat exchange, strengthening the heat exchange at the bottom inlet center and the top outlet. This changes the previous single heat exchange method from top to bottom, strengthens the heat exchange efficiency at different positions, makes the heat exchange uniform on the whole, and further achieves the purpose of strengthening heat transfer.

[0034] The above-mentioned area is the area projected onto the cross section of the shell, or the area projected onto a horizontal plane.

[0035] A manual stop valve is provided on the water outlet pipe of the cold fluid heat exchanger 5 for use during maintenance.

[0036] When the user does not need water, the flow regulating valve 12 and the user valve 11 are closed, and the outlet valve 10 is opened. The heat source flows along the main line; at the same time, it flows into the main line along the heat source branch line 31, the heat exchanger 8, the intermediate heat source branch line 32 and the outlet heat source branch line 33. In other words, the main line and the branch line can provide the same heat source.

[0037] When the user needs to use water, open the flow regulating valve 12, close the outlet valve 10, and open the user valve 11. As the heat exchange process between the heat exchanger 5 and the cold fluid proceeds, the water temperature in the middle branch decreases, and the water temperature displayed by the temperature sensor 8 is recorded in real time. When the temperature drops to the required temperature value. Take water from the user pipeline. When the user stops using water, close the flow regulating valve 12, so that the user valve 11 remains open to continuously discharge cold water. When the water temperature returns to 70°C, close the user valve 11 and open the outlet valve 10 at the same time to realize the normal water use function of the heat source system.

[0038] The heat exchange system provided by the present invention is particularly suitable for situations where users use hot water intermittently. When the user is not using it, the heat source in the heat exchanger 5 always remains in a flowing state, which can better meet the verification requirements and can provide different user water temperatures and flow rates, which can meet the needs of users with large flow rates.

[0039] The heat source comes from an electric heating boiler. The electric heating boiler includes a water tank, which is provided with an electric heating device. The water outlet of the water tank is connected to the inlet of the heat source main road, and the water return port of the water tank is connected to the outlet of the heat source main road. A pumping device is provided on the water tank inlet pipeline for conveying water.

[0040] A water level sensor is arranged in the water tank, and the water level sensor, the electric heating device, the pumping device and the controller are connected in data connection, and the controller automatically controls the power of the pumping device according to the measured water level in the tank 1. If the water level drops, the controller increases the flow of water entering the tank by controlling to increase the power of the pumping device. If the water level is too high, the controller reduces the power of the pumping device or shuts down the pumping device to reduce the flow of water entering the tank or stops supplying water to the tank.

[0041] Through the above-mentioned setting, on the one hand, it avoids the dry burning of the electric heating device caused by low water level, causing damage to the electric heating device and safety accidents. On the other hand, it avoids excessive water volume caused by excessive water level, and realizes intelligent control of water level.

[0042] When the measured water level is lower than the first water level, the controller controls the pumping device to supply water at a first power; when the measured water level is lower than a second water level lower than the first water level, the controller controls the pumping device to supply water at a second power higher than the first power; when the measured water level is lower than a third water level lower than the second water level, the controller controls the pumping device to supply water at a third power higher than the second power; when the measured water level is lower than a fourth water level lower than the third water level, the controller controls the pumping device to supply water at a fourth power higher than the third power; when the measured water level is lower than a fifth water level lower than the fourth water level, the controller controls the pumping device to supply water at a fifth power higher than the fourth power.

[0043] The first water level is 1.1-1.3 times the second water level, the second water level is 1.1-1.3 times the third water level, the third water level is 1.1-1.3 times the fourth water level, and the fourth water level is 1.1-1.3 times the fifth water level.

[0044] The fifth power is 1.7-1.9 times the fourth power, the fourth power is 1.6-1.8 times the third power, the third power is 1.5-1.7 times the second power, and the second power is 1.3-1.5 times the first power.

[0045] By optimizing the water level and the power of the pumping device, especially by setting the water level and the power of the pumping device differently, the water level can be kept constant quickly, the hot water output can be increased, and time can be saved.

[0046] Although the present invention has been disclosed as above with preferred embodiments, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A heat exchange system for a boiler, comprising a heat source main circuit, a cold source main circuit, a heat source branch circuit and a cold source branch circuit, wherein a main circuit valve is arranged on the heat source main circuit, and an inlet and an outlet of the heat source branch circuit are respectively connected to the upstream and downstream of the main circuit valve of the heat source main circuit; the heat source branch circuit comprises an inlet heat source branch circuit, a heat exchanger, an intermediate heat source branch circuit and an outlet heat source branch circuit which are connected in sequence; the inlet heat source branch circuit is provided with an inlet valve to control the connection with the upstream of the heat source main circuit, and the outlet heat source branch circuit is provided with an outlet valve to control the connection with the downstream of the heat source main circuit.

2. The heat exchange system of a boiler according to claim 1, characterized in that: The cold source branch is connected to the cold source main path, and the cold source branch is connected to the heat exchanger inlet pipe to exchange heat with the heat source entering the heat exchanger.

3. The heat exchange system of a boiler according to claim 2, characterized in that: A flow regulating valve is arranged on the cold source branch.

4. The heat exchange system of a boiler according to claim 3, characterized in that: A temperature sensor is provided on the intermediate heat source branch.

5. The heat exchange system of a boiler according to claim 4, characterized in that: The temperature sensor is data-connected to the flow regulating valve and the controller.

6. The heat exchange system of a boiler according to claim 1, characterized in that: The outlet heat source branch is connected to a user pipeline, and a user valve is arranged on the user pipeline.

7. The heat exchange system of a boiler according to claim 1, characterized in that: The heat exchanger is a shell and tube heat exchanger, with the heat source going through the tube side and the cold source going through the shell side.

8. The heat exchange system of a boiler according to claim 1, characterized in that: The heat source is hot water and the cold source is gas.

Images