Method for eliminating low-temperature-difference large-flow operation mode of heating system

Abstract

The invention provides a method for eliminating a low-temperature-difference large-flow operation mode of a heating system, belongs to the technical field of indoor heating systems of civil buildings, solves the problem of hydraulic imbalance of the heating system, and comprises the following steps: calculating circulating pressure and imbalance rate of a loop corresponding to each radiator; the gravity circulation of the radiator naturally adds pressure; selecting spare pipelines with different pipe diameters, wherein the pipe diameters of the spare pipelines are smaller than those of the original water inlet pipeline and water return pipeline; determining a target unbalance rate, and for the radiator with the unbalance rate absolute value exceeding the target unbalance rate, replacing the original water inlet pipeline and the original water return pipeline of the loop corresponding to the radiator with standby pipelines with proper pipe diameters, so that the unbalance rate absolute value is not greater than the target unbalance rate; and the pipelines of the loops corresponding to the radiators in the heating system are replaced in sequence. The heat supply system tail end hydraulic balance design serves as an opportunity, and the problems of indoor temperature imbalance and low-temperature-difference large-flow operation in the heat supply system operation are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of indoor heating systems for civil buildings, and in particular relates to a method for eliminating a low temperature difference and a large flow rate operation mode of a heating system. Background Art

[0002] The design methods of the double-pipe system with upper supply and lower return, double-pipe system with lower supply and lower return, and single-pipe system with upper supply and lower return in the current indoor heating systems of civil buildings were more commonly used in the 1960s and 1970s. At that time, the hydraulic balance was manually debugged using a stop valve. The debugging of each system required multiple adjustments, and the results of this adjustment would be destroyed due to the residents' opening and closing of the valve. Later, the thermostatic automatic control valve was invented, which has high installation costs and short service life, making it difficult to promote and use it universally. Later, there were self-operated flow control valves and self-operated pressure control valves. Due to their complex structure and high cost, these products are generally used at the entrance of each heat exchange station to balance the flow of the primary network. They are installed at the entrance of the building in the secondary network to adjust the level between buildings, but are difficult to use in the flow regulation of each group of radiators.

[0003] Since the 1990s, the country has increased its efforts to save energy and reduce consumption in buildings. The insulation effect of the exterior walls of buildings has become better and better, and the energy consumption of buildings has gradually decreased. However, the indoor temperature imbalance during winter heating has become more and more serious. The room temperature of the middle room is overheated, while the temperature of the rooms on the sides, top and bottom floors is too low. In order to solve this problem, the heating units generally adopt a low temperature difference and large flow operation mode. Although this operation mode alleviates the phenomenon of room temperature imbalance, it fails to eradicate the indoor temperature imbalance of the building. Based on this situation, in order to ensure that the room temperature of the rooms on the sides, top and bottom floors reaches the national standard of 16°C or above, the room temperature of the middle room is as high as 25°C or above, and the middle room generally has the situation of opening windows for heat dissipation. I think the reason for the low temperature difference and large flow operation mode is mainly caused by the hydraulic imbalance of the indoor heating system of the building.

[0004] The national standard stipulates that the unbalance rate difference between parallel loops in a two-pipe same-program system is 15%; the unbalance rate difference between parallel loops in a two-pipe different-program system is 25%; the unbalance rate difference between parallel loops in a single-pipe same-program system is 10%; the unbalance rate difference between parallel loops in a single-pipe different-program system is 15%; however, in actual engineering design, the unbalance rate between parallel loops far exceeds the national standard. In some systems, the unbalance rate between parallel loops of the above heating systems reaches 30%-50%. Due to the existence of the natural additional pressure of gravity circulation generated by the temperature drop of hot water, the unbalance rate between parallel loops in a two-pipe system is constantly increasing as the floor increases.

[0005] The main factor causing hydraulic imbalance in the system is that the heat consumption of each room is getting smaller and smaller in the design of the current heating system, and the smallest pipe diameter used in the design is DN15. In the hydraulic balance calculation of the double-pipe system, the specific friction resistance of the DN15 branch pipe connecting the radiator is very small, usually below 5Pa / m, and some have a specific friction resistance as small as below 1Pa / m, making it difficult to meet the hydraulic balance requirements. This is the fundamental reason for the indoor temperature imbalance in the building.

[0006] The serious hydraulic imbalance in the design of the indoor heating system of the building is the inevitable result of the long-term existence of the low temperature difference and large flow operation mode. Only by solving the above-mentioned hydraulic imbalance problems in the heating system can the low temperature difference and large flow operation mode in the heating operation be fundamentally eliminated. Summary of the invention

[0007] The object of the present invention is to provide a method for eliminating the low temperature difference and large flow rate operation mode of a heating system, so as to solve the problem of hydraulic imbalance of the heating system.

[0008] The technical solution of the present invention is: a method for eliminating the low temperature difference and large flow rate operation mode of a heating system, comprising the following steps:

[0009] Step 1: Determine the heat load Q, water flow rate G, pipe length L, pipe diameter D, water flow rate v, along-the-line loss R per meter of pipe length, along-the-line loss △Py of the pipe section, the sum of local friction resistance coefficients ∑ζ, dynamic pressure △pd, local loss △pj of the pipe section, and pressure loss △P of each pipe section in the loop corresponding to each radiator in the entire heating system, and calculate the circulation pressure and imbalance rate of the loop corresponding to each radiator, as well as the gravity circulation natural additional pressure of the floor corresponding to the radiator; The loss along the pipe section is △Py=R×L; The local loss of the pipe section △pj=△pd×∑ζ; The pressure loss of the pipe section △P=△Py+△pj; The natural additional pressure of gravity circulation on the floor corresponding to the radiator = the influencing parameter of the natural additional pressure of gravity circulation × (system circulation return water density - system circulation supply water density) × water gravity acceleration × the floor height of the floor corresponding to the radiator; The circulation pressure of the corresponding loop of the radiator = the sum of the pressure loss △P of each pipe section of the corresponding loop - the natural additional pressure of the gravity circulation of the corresponding floor of the radiator; Unbalance rate = (maximum circulation pressure of the radiator in the system - circulation pressure of the corresponding loop of the radiator) / maximum circulation pressure of the radiator in the system × 100%;

[0010] Step 2: Select spare pipes with different diameters, where the diameter of the spare pipes is smaller than the original water inlet pipes and return pipes;

[0011] Step 3: Determine the target unbalance rate. For the radiator whose calculated absolute value of unbalance rate exceeds the target unbalance rate, replace the original water inlet pipe and the original water return pipe of the corresponding loop with spare pipes of appropriate pipe diameters so that the absolute value of the unbalance rate is not greater than the target unbalance rate. Then, the pipe replacement of the corresponding loop of the radiator is completed.

[0012] Step 4: Follow the above steps to replace the pipes of each radiator corresponding loop in the heating system in turn.

[0013] As a further improvement of the present invention, in step 3, the water inlet pipe and the water return pipe are replaced by gradually reducing the pipe diameter, as follows:

[0014] A. Sort the spare pipes in descending order according to their diameters;

[0015] B. Start replacing from the original water inlet branch pipe, and replace the original water inlet branch pipe in the corresponding loop of the radiator with the first-level spare pipe; then calculate the imbalance rate, if the absolute value of the calculation result is still greater than the target imbalance rate and the calculation result is positive, continue to replace the original return water branch pipe with the first-level spare pipe; calculate the imbalance rate again, if the absolute value of the calculation result is still greater than the target imbalance rate and the calculation result is positive, continue to replace the replaced water inlet branch pipe with the next-level spare pipe; calculate the imbalance rate again, if the absolute value of the calculation result is still greater than the target imbalance rate and the calculation result is positive, continue to replace the replaced return water branch pipe with the next-level spare pipe; thus, replace the water inlet branch pipe and the return water branch pipe alternately from large to small, and recalculate the imbalance rate after each replacement until the absolute value of the calculation result is not greater than the target imbalance rate, and then complete the pipe replacement of the corresponding loop of the radiator;

[0016] You can also start from the original return branch pipe; the replacement method is the same as above, replace the inlet branch pipe and the return branch pipe alternately from large to small.

[0017] In the above replacement process, if the absolute value of a certain calculation result is still greater than the target imbalance rate and the calculation result is a negative value, the spare pipeline replaced last time is segmented and reduced in diameter, that is, a part of the spare pipeline replaced last time is called back to the previous level spare pipeline so that the absolute value of its imbalance rate is not greater than the target imbalance rate.

[0018] As a further improvement of the present invention, in step 1, the gravity circulation natural additional pressure influence parameter is 2 / 3.

[0019] As a further improvement of the present invention, in step 2, spare pipes of different diameters are selected, and the spare pipes of the following diameters are selected, namely DN12, DN10, DN8, DN6, DN5, and DN4.

[0020] As a further improvement of the present invention, the calculation formula for the loss along the spare pipeline of DN12, DN10, DN8, DN6, DN5, and DN4 diameters is: Where: R is the loss along the pipeline per meter, in units of Pa / m; G is the water flow rate of the pipe section, in units of kg / h; d is the inner diameter of the pipe, in units of m; ρ is the density of the heat medium, in units of kg / m 3 ;

[0021] The pipeline loss R of DN10 diameter is the existing value. The calculation steps of pipeline loss R of DN12, DN8, DN6, DN5 and DN4 diameter are as follows:

[0022] A. Substitute the existing values ​​of the existing along-the-line loss R, the water flow rate G of the pipe section, the inner diameter d of the pipe and the density ρ of the heat medium of the existing pipelines with different diameters into the pipeline along-the-line loss calculation formula (1), and inversely derive the friction resistance coefficient λ of the pipelines with different diameters;

[0023] B. According to the friction coefficient λ values ​​of the above pipes with different diameters, the friction coefficient λ values ​​of five small diameter pipes of DN12, DN8, DN6, DN5 and DN4 are obtained by linear insertion method at the same flow rate;

[0024] C. Substitute the friction coefficient λ of the five small-diameter pipes DN4, DN5, DN6, DN8 and DN12 obtained by the linear insertion method into the pipeline loss calculation formula (1) to calculate the pipeline loss R per meter of the five small-diameter pipes DN4, DN5, DN6, DN8 and DN12.

[0025] As a further improvement of the present invention, in step three, the target imbalance rate is ±5%.

[0026] As a further improvement of the present invention, in step three, replacement starts from the corresponding loop of the radiator at the bottom layer of each riser.

[0027] The beneficial effects of the present invention are as follows:

[0028] The present invention relates to a design method for hydraulic balance of indoor heating system of a building. Taking the hydraulic balance design of the terminal of the heating system as an opportunity, the problem of indoor temperature imbalance and low temperature difference and large flow operation in the operation of the heating system is solved. Specifically, a new method for hydraulic balance design of the heating system of a building is proposed.

[0029] The purpose of the present invention is to provide a new hydraulic balance design concept, so that the hydraulic target imbalance rate between each parallel loop in the heating system design can be controlled within ±5%. The most ideal effect is to control the hydraulic target imbalance rate between each parallel loop within ±1%. In this way, the problem of uneven indoor heating temperature in the building can be solved, thereby fundamentally eliminating the low temperature difference and large flow operation mode in the heating operation.

[0030] The method of the present invention is that in the design, in order to achieve hydraulic balance between the parallel loops, the pipeline with suitable relative friction resistance is replaced in the design to reasonably distribute the circulation flow. In the hydraulic balance design of the system, in order to control the hydraulic balance within ±1%, when selecting the diameter of each section of spare pipeline, spare pipelines of DN12, DN10, DN8, DN6, DN5 and DN4 are used in the design to meet the needs of innovative design. At the same time, the stop valve originally used for regulating the flow in the system is replaced with a gate valve with only a shut-off function. The new design method only needs to replace the pipeline with suitable relative friction resistance to regulate the flow.

[0031] In the hydraulic balance design of the present invention, in order to control the hydraulic imbalance rate between parallel loops within ±1%, when there is no pipe with a suitable diameter available for the branch pipe connecting the radiator in the design, the pipe section can be divided into two pipe sections with different pipe diameters, and the lengths of the two pipe sections can be adjusted to meet the design requirements. Through multiple regular diameter adjustment, the imbalance rate calculated after each replacement can be closer to the target imbalance rate. In this process, the calculated imbalance rate will not fluctuate, but can be adjusted to the target imbalance rate more quickly and accurately.

[0032] Through many, extensive and long-term studies, it is found that the use of DN12, DN10, DN8, DN6, DN5, and DN4 pipes in hydraulic balance design can make the system hydraulic balance design reach an ideal state, and the target imbalance rate can be controlled within ±5% or less to ±1%, which can then solve the temperature imbalance phenomenon in the building, reduce the temperature difference of the indoor imbalance in the building, and change the low temperature difference and large flow operation. The application of this method can control the indoor temperature difference within the 18±2℃ specified by the national standard; the operating temperature difference of the upper supply and lower return double-pipe system, the lower supply and lower return double-pipe system, and the upper supply and lower return single-pipe system can be controlled to about 25℃ or more specified in the specification. In this way, the circulation flow of the system can be reduced, and a circulating water pump with a small flow and low head can be used instead, reducing the electricity expenditure of the circulating water pump, eliminating the current low temperature difference and large flow operation mode, and achieving significant social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1The friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.05m / s;

[0034] Figure 2 This is the friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.10m / s;

[0035] Figure 3 This is the calculation diagram of the friction resistance coefficient of pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.15m / s by insertion method;

[0036] Figure 4 This is the friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.20m / s;

[0037] Figure 5 This is the calculation diagram of the friction resistance coefficient of pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.25m / s by insertion method;

[0038] Figure 6 The friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.30m / s;

[0039] Figure 7 The friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.35m / s;

[0040] Figure 8 This is the friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.40m / s;

[0041] Fig. 9 The friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.45m / s;

[0042] Fig.10 This is the friction coefficient insertion method calculation diagram for pipes with diameters of DN12, DN8, DN6, DN5, and DN4 at a flow rate of 0.50m / s;

[0043] Fig.11 Diagram of an innovative double-pipe system with upper supply and lower return for mechanical circulation hot water heating in a six-story building. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0045] There are mature calculation tables for the specific friction resistance of pipes with a diameter of DN15 and above that can be used. After searching in the "HVAC Common Data Manual", it was found that only the specific friction resistance calculation data for DN10 pipes was available for the newly added DN12, DN10, DN8, DN6, DN5, and DN4 pipes in this method. The specific friction resistance calculation data for other newly added DN12, DN8, DN6, DN5, and DN4 pipes in this method are based on the existing specific friction resistance calculation data for DN25, DN20, DN15, and DN10 pipes, and are derived according to the calculation formula for pipeline losses.

[0046] According to the needs of central heating project construction, the smallest diameter of steel pipes currently used in indoor heating system design is DN15, which can no longer meet the hydraulic balance design needs under current building energy-saving conditions. Smaller diameter pipes must be used, but only DN10 pipes have loss calculation data available.

[0047] After searching the data, it is found that steel pipes with nominal diameters of DN12, DN10, DN8, DN6, DN5, DN4, and DN3 are available. The outer diameter of DN12 pipe is 19mm, the wall thickness is 3.5mm, and the inner diameter is 12mm; the outer diameter of DN10 pipe is 17.2mm, the wall thickness is 3.85mm, and the inner diameter is 9.5mm; the outer diameter of DN8 pipe is 13.5mm, the wall thickness is 2.75mm, and the inner diameter is 8mm; the outer diameter of DN6 pipe is 10.2mm, the wall thickness is 2.0mm, and the inner diameter is 6.2mm; no relevant data on the outer diameter and wall thickness of DN5, DN4, and DN3 were found.

[0048] According to multiple studies, the pipes that can be used are DN12, DN10, DN8, DN6, DN5, and DN4. In order to prevent pipe bending and deformation during construction, thick-walled seamless steel pipes are used for DN8, DN6, DN5, and DN4 pipes. DN8 pipes use seamless steel pipes with an outer diameter of 16mm, a wall thickness of 4.25mm, and an inner diameter of 7.5mm; DN6 pipes use seamless steel pipes with an outer diameter of 15mm, a wall thickness of 4.5mm, and an inner diameter of 6mm; DN5 pipes use seamless steel pipes with an outer diameter of 14mm, a wall thickness of 4.5mm, and an inner diameter of 5mm; DN4 pipes use seamless steel pipes with an outer diameter of 13mm, a wall thickness of 4.5mm, and an inner diameter of 4mm.

[0049] The above six newly selected pipes were found to have along-the-line loss calculation data for DN10 pipes in the "HVAC Common Data Manual", but no available along-the-line loss calculation data for pipes of other diameters was found. In order to meet the needs of hydraulic balance design of heating systems, this method uses the linear interpolation method to derive the along-the-line loss calculation data for the newly added five small-diameter pipes of DN12, DN8, DN6, DN5, and DN4 based on the along-the-line loss data of the existing four existing pipes of DN10, DN15, DN20, and DN25.

[0050] The specific method is as follows: The first step is to calculate the loss along the pipeline according to the formula: R is the loss along the pipeline per meter, in Pa / m; G is the water flow rate of the pipe section, in kg / h; d is the inner diameter of the pipe, in m; ρ is the density of the heat medium, in kg / m 3 , choose 983.248kg / m 3 .

[0051] Substitute the existing values ​​of the existing along-the-line loss data R of the four existing DN10, DN15, DN20 and DN25 pipelines, the water flow rate G of the pipe section, the inner diameter d of the pipe and the density ρ of the heat medium into formula (1), and inversely deduce the friction resistance coefficient λ of the four existing DN10, DN15, DN20 and DN25 pipelines.

[0052] In the second step, based on the derived friction resistance coefficient λ value, calculate the friction resistance coefficient λ of the four pipes DN10, DN15, DN20 and DN25 at flow rates of 0.05m / s, 0.10m / s, 0.15m / s, 0.20m / s, 0.25m / s, 0.30m / s, 0.35m / s, 0.40m / s, 0.45m / s and 0.50m / s respectively. The friction resistance coefficients of the four pipes DN10, DN15, DN20 and DN25 at the above ten flow rates are shown in Table 1-10. Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10

[0053] The third step is to use the linear insertion method to obtain the friction resistance coefficient λ values ​​of the newly added DN12, DN8, DN6, DN5, and DN4 small-diameter pipes at the above ten flow rates based on the friction resistance coefficient λ values ​​of the selected DN10, DN15, DN20, and DN25 pipes at the same flow rate, as shown in Tables 11-20. The specific insertion methods are as follows: Figure 1-10 shown. Table 11 Table 12 Table 13 Table 14 Table 15 Table 16 Table 1 7 Table 18 Table 19 Table 20

[0054] The fourth step is to substitute the friction coefficient λ values ​​of the newly added DN4, DN5, DN6, DN8, and DN12 small-diameter pipes obtained by the linear insertion method into the pipeline loss calculation formula (1), and finally calculate the loss R of each meter of the newly added DN4, DN5, DN6, DN8, and DN12 pipes. Finally, the results of the loss of each meter of the DN4, DN5, DN6, DN8, and DN12 pipes are summarized into a book for easy use, as shown in Table 21. Hydraulic calculation table for newly added hot water indoor heating pipes (indoor pipes k = 0.2mm, ρ = 958kg / m 3 ) as shown.

[0055] When calculating the along-the-line loss ΔPy of a pipe section, the corresponding friction resistance coefficient λ value is selected according to the pipes of different diameters at the corresponding water flow rate v, the λ value is substituted into the calculation formula for the along-the-line loss of the pipe, the corresponding along-the-line loss R of the pipe is calculated, and then the along-the-line loss ΔPy of the pipe section is calculated.

[0056] Embodiment 1,

[0057] The method of the present invention is to select a small-diameter spare pipe to perform reasonable flow distribution in the hydraulic balance design of the upper supply and lower return double-pipe system, the lower supply and lower return double-pipe system and the upper supply and lower return single-pipe system, so that the hydraulic imbalance rate between the parallel loops in the heating system design is controlled within the target imbalance rate ±1%. Other design conditions and data in this method remain unchanged, and it is also necessary to replace the stop valve originally used for regulating the flow in the system with a gate valve that only has a shut-off function. The following is a detailed description taking the existing upper supply and lower return double-pipe system design as an example. Fig.11 Diagram of an innovative double-pipe system with upper supply and lower return for mechanical circulation hot water heating in a six-story building.

[0058] like Fig.11 The diagram of the innovative double-pipe system for mechanical circulation hot water heating in a six-story building is shown. The building has a floor height of 2.9 meters and a basement floor height of 2.2 meters. There are six groups of risers in the heating system, namely riser A, riser B, riser C, riser D, riser E and riser F, with a total of 48 groups of radiators, and riser B and riser E each have two groups of radiators on the left and right. Fig.11 The number under the horizontal line in each radiator is the room number, the number on the horizontal line is the heat load Q of the room, the number in the circle next to the pipeline is the pipe section number, the number on the horizontal line next to the circle is the heat load Q of the pipe section, and the number under the horizontal line is the length L of the pipe section. Each group of radiators in the innovative upper supply and lower return double-pipe system of mechanical circulation hot water heating is a parallel loop, and the loop where each group of radiators is located consists of 16 pipe sections.

[0059] By calculating the maximum value of the circulating pressure in the corresponding loop of each radiator of the system, it occurs in room 103 of riser B, and the value is 5135.33Pa;

[0060] The natural additional pressure of gravity circulation generated by the temperature drop of hot water in this system is relative to the first floor. The natural additional pressure of gravity circulation generated by the second, third, fourth, fifth and sixth floors relative to the first floor. The building has a floor height of 2.9 meters. The circulating water supply of this system is 95℃ and the return water is 70℃, with densities of 961.92kg and 977.81kg respectively. In actual operation, considering the influence of mass regulation, the influence parameter of the natural additional pressure of gravity circulation can be considered as 2 / 3 of the maximum value of the design working condition. Since the natural additional pressure of gravity circulation is generated by the temperature drop of water, it is beneficial to the circulation of hot water and should be subtracted from the circulation pressure of the loop. The natural additional pressure of gravity circulation generated by each layer is as follows: The natural additional pressure of gravity circulation in one layer is 0; The gravity circulation of the second floor naturally adds pressure =2 / 3x(977.81-961.92)x9.8x2.9=301.06Pa; Three layers of gravity circulation naturally add pressure =2 / 3x(977.81-961.92)x9.8x5.8=602.13Pa; Four layers of gravity circulation naturally add pressure =2 / 3x(977.81-961.92)x9.8x8.7=903.19Pa; Five layers of gravity circulation naturally add pressure =2 / 3x(977.81-961.92)x9.8x11.6=1204.25Pa; Six layers of gravity circulation naturally add pressure =2 / 3x(977.81-961.92)x9.8x14.5=1505.31Pa.

[0061] As shown in Table 22, the hydraulic calculation table of the mechanical circulation hot water heating upper supply and lower return double-pipe system (riser B), it is calculated that the maximum circulation pressure in each loop of the system occurs in room 103 of riser B, with a value of 5135.33 Pa. The radiator circulation pressure calculation tables in other rooms are not displayed due to the simplicity of the document.

[0062] The circulation pressure of this loop, 5135.33Pa, is used as the base to compare with the circulation pressure of each loop in the system to obtain the circulation pressure imbalance rate of each loop. After preliminary calculation, the maximum imbalance rate of the system occurs in room 608 of riser F, reaching 35.82%, as shown in Table 23, Primary Hydraulic Calculation Table of Mechanical Circulation Hot Water Heating Innovation Up-supply and Down-return Double-pipe System (Rise-pipe F), which far exceeds the 15% stipulated in the specification.

[0063] According to the idea of ​​innovative design and invention, it is necessary to make further adjustments to the loops whose imbalance rate does not reach the target imbalance rate within ±1% based on the primary hydraulic calculation table. Table 22 Table 23

[0064] The specific adjustment steps are as follows;

[0065] The first step is to start from the radiator loop in room 101 of riser A. The circulation pressure of this loop is 5057.13Pa, and the imbalance rate is 1.52%. The adjustment of this loop is to adjust the water inlet branch pipe connected to the radiator (pipe section number is 179) in sections and adjust the pressure. After adjusting the position of the section diameter change several times, the pipe is reduced in diameter after the bend of the water inlet branch pipe. The front section is 1.01 meters with a nominal diameter of 10mm, and the rear section is 0.09 meters with a nominal diameter of 8mm. The local resistance coefficient of the part before the diameter change is 8, and the local resistance coefficient of the part after the diameter change is 2.5. The adjusted circulation pressure is 5135.00Pa, and the imbalance rate is 0.01%. The adjustment effect is relatively ideal, as shown in Table 24 Mechanical circulation hot water heating upper supply and lower return double-pipe system hydraulic calculation table (riser A).

[0066] The second step is to adjust the radiator in room 201 of riser A. The circulation pressure of the loop is 4688.54Pa, and the imbalance rate is 8.70%. The adjustment of the loop is to first change the entire section of the return branch pipe (section number 177) from a nominal diameter of 10mm to a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulation pressure is 4931.62Pa, and the imbalance rate is 3.97%. The adjustment effect is not ideal;

[0067] Continue to adjust the water inlet branch pipe (section number 176) by segmented diameter reduction and pressure regulation. After adjusting the position of the segmented diameter reduction several times, the pipe is reduced in diameter from the bend of the water inlet branch pipe to before the gate valve. The front section is 0.45 meters with a nominal diameter of 10mm, and the rear section is 0.75 meters with a nominal diameter of 8mm. The local resistance coefficient of the part before the diameter reduction is 4.5, and the local resistance coefficient of the part after the diameter reduction is 6.5. The adjusted circulating pressure is 5135.00Pa, and the imbalance rate is 0.01%. The adjustment effect is relatively ideal, as shown in Table 25.

[0068] The third step is to adjust the radiator loop of room 301 of riser A. The circulation pressure of the loop is 4337.31Pa, and the imbalance rate is 15.54%. The adjustment of the loop is to first change the entire section of the return branch pipe (section number 174) from a nominal diameter of 10mm to a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulation pressure is 4580.39Pa, and the imbalance rate is 10.81%. The adjustment effect is not ideal;

[0069] Continue to change the entire section of the water inlet branch pipe (section number 173) from a pipe with a nominal diameter of 10mm to a pipe with a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulation pressure is 4907.61Pa, and the imbalance rate is 4.43%. The adjustment effect is not ideal; continue to reduce the diameter and adjust the pressure of the water inlet branch pipe (section number 173) in sections. After adjusting the position of the section diameter change for many times, the pipe is reduced in diameter before the bend of the water inlet branch pipe. The front section is 1.01 meters with a nominal diameter of 8mm, and the rear section is 0.19 meters with a nominal diameter of 6mm. The local resistance coefficient of the part before the diameter change is 2.0, and the local resistance coefficient of the part after the diameter change is 2.5. The adjusted circulation pressure is 5134.31Pa, and the imbalance rate is 0.02%. The adjustment effect is relatively ideal, as shown in Table 26.

[0070] The fourth step is to adjust the radiator loop of room 401 of riser A. The circulation pressure of the loop is 4034.31Pa, and the imbalance rate is 21.44%. The adjustment of the loop is to first change the nominal diameter of the return riser (section number 161) pipe of 15mm to a nominal diameter of 12mm, and modify the local resistance coefficient of the riser after the diameter change accordingly. The adjusted circulation pressure is 4436.65Pa, and the imbalance rate is 13.61%. The adjustment effect is not in place;

[0071] Continue to change the entire section of the return branch pipe (section number 171) from a pipe with a nominal diameter of 10mm to a pipe with a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulation pressure is 4679.73Pa, and the imbalance rate is 8.87%. The adjustment result is not in place; continue to change the entire section of the inlet branch pipe (section number 170) from a pipe with a nominal diameter of 10mm to a pipe with a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulation pressure is 5006.94Pa, ​​and the imbalance rate is 2.50%. The adjustment result is not in place.

[0072] Continue to reduce the diameter and adjust the pressure of the water inlet branch pipe (section number 170) in sections. After adjusting the position of the section reduction several times, the branch pipe is reduced in diameter after the bend. The front section 1.1 meters has a nominal diameter of 8mm, and the rear section 0.1 meters has a nominal diameter of 6mm. The local resistance coefficient of the part before the diameter reduction is 9, and the local resistance coefficient of the part after the diameter reduction is 2.5. The adjusted circulating pressure is 5136.24Pa, and the imbalance rate is -0.02%. The adjustment effect is relatively ideal.

[0073] Before entering the next step of adjustment, adjust the radiator loop of room 401 of riser A by changing the nominal diameter of 15mm pipe of the return riser (pipe section number 161) to a nominal diameter of 12mm pipe. Because the risers are shared, the pipe sections of the radiator loops of room 501 and room 601 served by the riser section must be changed in diameter at the same time. The changes in the diameter of the shared riser pipes are also adjusted in this way, as shown in Table 27.

[0074] The fifth step is to adjust the radiator loop of room 501 of riser A. The circulation pressure of the loop is 4185.08Pa, and the imbalance rate is 18.50%. The adjustment of the loop is to first change the nominal diameter of the return riser (section number 160) pipe with a nominal diameter of 12mm to a pipe with a nominal diameter of 10mm, and modify the local resistance coefficient of the riser after the diameter change accordingly. The adjusted circulation pressure is 4749.61Pa, and the imbalance rate is 7.51%. The adjustment effect is not in place;

[0075] Continue to change the entire section of the return branch pipe (section number 168) from a pipe with a nominal diameter of 10mm to a pipe with a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulation pressure is 4992.69Pa, and the imbalance rate is 2.78%. The adjustment result is not in place;

[0076] Continue to adjust the water inlet branch pipe (section number 167) in sections with reduced diameter and pressure. After adjusting the position of the sectioned reduced diameter for several times, the branch pipe is reduced in diameter from after the bend to before the gate valve. The front section is 0.66 meters with a nominal diameter of 10mm, and the rear section is 0.54 meters with a nominal diameter of 8mm. The local resistance coefficient of the part before the section is reduced is 6.0, and the local resistance coefficient of the part after the section is reduced is 4.5. The adjusted circulating pressure is 5135.67Pa, and the imbalance rate is -0.01%. The adjustment effect is relatively ideal, as shown in Table 28.

[0077] Step 6: Adjust the radiator loop of room 601 of riser A. The circulation pressure of the loop is 4418.96Pa, and the unbalance rate is 13.95%. The adjustment of the loop is to first change the entire section of the return branch pipe (section number 158) from a nominal diameter of 10mm to a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulation pressure is 4740.17Pa, and the unbalance rate is 7.69%. The adjustment result is not in place;

[0078] Continue to change the entire section of the water inlet branch pipe (section number 157) from a pipe with a nominal diameter of 10mm to a pipe with a nominal diameter of 8mm, and modify the local resistance coefficient of the branch pipe after the diameter change accordingly. The adjusted circulating pressure is 5102.28Pa, and the imbalance rate is 0.64%. The adjustment effect is not ideal; after extending the inlet and outlet water branches connecting the radiator by 0.03 meters, the circulating pressure is 5134.21Pa, and the imbalance rate is 0.02%. The adjustment effect is relatively ideal, as shown in Table 29.

[0079] The circulation pressure adjustment methods for the corresponding loops of the radiators in other rooms follow the above steps, and adjust the imbalance rate from the bottom layer to the top layer by layer with each riser as a group, so that the imbalance rate of each loop is controlled within ±1%.

[0080] This method further replaces the diameter of the pipe section with smaller specific friction resistance of the system main pipe with a pipe with a specific friction resistance greater than 20Pa; replaces the diameter of the pipe section with smaller specific friction resistance of the system riser and branch pipe with a pipe with a specific friction resistance greater than 30Pa; replaces the stop valve originally used to adjust the flow in the system with a gate valve with only a shut-off function. The design idea is to increase the resistance of the terminal pipe of the system and only use the thickness of the pipe to adjust the flow, which is beneficial to the hydraulic balance of the system.

[0081] When this method is used for hydraulic balance design, when the heat load is small, the inlet and outlet water branches are short, and it is not conducive to the adjustment of hydraulic balance, in order to control the hydraulic imbalance rate between parallel loops within ±1%, when the length of the branch pipe connected to the radiator is short in the design, it is not suitable to perform segmented pressure regulation on the branch pipe. The outlet of the water inlet branch pipe connected to the radiator can be moved upward by 1.2 meters so that the length of the water inlet branch pipe reaches about 1.5 meters and can be used as a pressure regulating pipe.

[0082] In the hydraulic balance design of this method, if the heat consumption of the radiator carried by some risers is relatively small, when the branch pipes cannot be in hydraulic balance, in order to control the hydraulic imbalance rate of the circulation loop of each group of radiators within ±1%, the diameter of the riser can also be adjusted. The adjustment method is the same as that of the branch pipe, that is, when there is no pipe with a suitable diameter to choose from, the section of the riser can be divided into two sections of pipes with different diameters, and the lengths of the two sections of pipes can be adjusted to meet the design needs.

[0083] For example, if there is a 2.90-meter return water riser, the friction resistance of the pipe with a diameter of DN10 is a little smaller, and the friction resistance of the pipe with a diameter of DN8 is a little larger, then the pipe section is divided into two sections, the upper section is a pipe with a diameter of DN8, and the lower section is a pipe with a diameter of DN10. The length of the upper and lower sections of the pipe is determined according to the requirement of controlling the imbalance rate within ±1%, and the local resistance coefficient of each section is adjusted at the same time. When the diameter of the riser is adjusted, the diameter of the riser in the loop related to the riser must also be changed at the same time.

[0084] When the method is used for hydraulic balance design, in order to control the hydraulic imbalance rate between parallel loops within ±1%, a smaller diameter pipe has been selected for the branch pipe connecting the radiator in the design. When the imbalance rate still does not reach the requirement of ±1% but the gap is not large, the target imbalance rate will be exceeded when the pipe diameter is changed. The imbalance rate can also be adjusted by extending (or shortening) the length of the branch pipe, or by extending the return branch pipe to discharge water from the opposite side to increase the length of the return branch pipe and the local resistance coefficient to achieve hydraulic balance.

Claims

1. A method for eliminating low temperature difference and high flow rate operation mode of a heating system, characterized in that: The following steps are involved: Step 1: Determine the heat load Q, water flow rate G, pipe length L, pipe diameter D, water flow rate v, along-the-line loss R per meter of pipe length, along-the-line loss △Py of the pipe section, the sum of local friction resistance coefficients ∑ζ, dynamic pressure △pd, local loss △pj of the pipe section, and pressure loss △P of each pipe section in the loop corresponding to each radiator in the entire heating system, and calculate the circulation pressure and imbalance rate of the loop corresponding to each radiator, as well as the gravity circulation natural additional pressure of the floor corresponding to the radiator; The loss along the pipe section is △Py=R×L; The local loss of the pipe section △pj=△pd×∑ζ; The pressure loss of the pipe section △P=△Py+△pj; The natural additional pressure of gravity circulation on the floor corresponding to the radiator = the influencing parameter of the natural additional pressure of gravity circulation × (system circulation return water density - system circulation supply water density) × water gravity acceleration × the floor height of the floor corresponding to the radiator; The circulation pressure of the corresponding loop of the radiator = the sum of the pressure loss △P of each pipe section of the corresponding loop - the natural additional pressure of the gravity circulation of the corresponding floor of the radiator; Unbalance rate = (maximum circulation pressure of the radiator in the system - circulation pressure of the corresponding loop of the radiator) / maximum circulation pressure of the radiator in the system × 100%; Step 2: Select spare pipes with different diameters, where the diameter of the spare pipes is smaller than the original water inlet pipes and return pipes; Step 3: Determine the target unbalance rate. For the radiator whose calculated absolute value of unbalance rate exceeds the target unbalance rate, replace the original water inlet pipe and the original water return pipe of the corresponding loop with spare pipes of appropriate pipe diameters so that the absolute value of the unbalance rate is not greater than the target unbalance rate. Then, the pipe replacement of the corresponding loop of the radiator is completed. Step 4: Follow the above steps to replace the pipes of each radiator corresponding loop in the heating system in turn.

2. A method for eliminating low temperature difference and large flow rate operation mode of a heating system according to claim 1, characterized in that: In step 3, the water inlet pipe and the water return pipe are replaced by gradually reducing the pipe diameter, as follows: A. Sort the spare pipes in descending order according to their diameters; B. Start replacing from the original water inlet branch pipe, and replace the original water inlet branch pipe in the corresponding loop of the radiator with the first-level spare pipe; then calculate the imbalance rate, if the absolute value of the calculation result is still greater than the target imbalance rate and the calculation result is positive, continue to replace the original return water branch pipe with the first-level spare pipe; calculate the imbalance rate again, if the absolute value of the calculation result is still greater than the target imbalance rate and the calculation result is positive, continue to replace the replaced water inlet branch pipe with the next-level spare pipe; calculate the imbalance rate again, if the absolute value of the calculation result is still greater than the target imbalance rate and the calculation result is positive, continue to replace the replaced return water branch pipe with the next-level spare pipe; thus, replace the water inlet branch pipe and the return water branch pipe alternately from large to small, and recalculate the imbalance rate after each replacement until the absolute value of the calculation result is not greater than the target imbalance rate, and then complete the pipe replacement of the corresponding loop of the radiator; You can also start the replacement from the original return branch pipe; In the above replacement process, if the absolute value of a certain calculation result is still greater than the target imbalance rate and the calculation result is a negative value, the spare pipeline replaced last time is segmented and reduced in diameter, that is, a part of the spare pipeline replaced last time is called back to the previous level spare pipeline so that the absolute value of its imbalance rate is not greater than the target imbalance rate.

3. A method for eliminating low temperature difference and large flow rate operation mode of a heating system according to claim 1, characterized in that: In step 1, the gravity cycle natural additional pressure influence parameter is 2 / 3.

4. A method for eliminating low temperature difference and large flow rate operation mode of a heating system according to claim 1, characterized in that: In step 2, select spare pipes of different diameters, and select spare pipes of the following diameters, namely DN12, DN10, DN8, DN6, DN5, and DN4.

5. A method for eliminating low temperature difference and large flow rate operation mode of a heating system according to claim 4, characterized in that: The calculation formula for the loss along the spare pipeline of the DN12, DN10, DN8, DN6, DN5 and DN4 diameters is: Where: R is the loss along the pipeline per meter, in units of Pa / m; G is the water flow rate of the pipe section, in units of kg / h; d is the inner diameter of the pipe, in units of m; ρ is the density of the heat medium, in units of kg / m 3 ; The pipeline loss R of DN10 diameter is the existing value. The calculation steps of pipeline loss R of DN12, DN8, DN6, DN5 and DN4 diameter are as follows: A. Substitute the existing values ​​of the existing along-the-line loss R, the water flow rate G of the pipe section, the inner diameter d of the pipe and the density ρ of the heat medium of the existing pipelines with different diameters into the pipeline along-the-line loss calculation formula (1), and inversely derive the friction resistance coefficient λ of the pipelines with different diameters; B. According to the friction coefficient λ values ​​of the above pipes with different diameters, the friction coefficient λ values ​​of five small diameter pipes of DN12, DN8, DN6, DN5 and DN4 are obtained by linear insertion method at the same flow rate; C. Substitute the friction coefficient λ of the five small-diameter pipes DN4, DN5, DN6, DN8 and DN12 obtained by the linear insertion method into the pipeline loss calculation formula (1) to calculate the pipeline loss R per meter of the five small-diameter pipes DN4, DN5, DN6, DN8 and DN12.

6. A method for eliminating low temperature difference and high flow rate operation mode of a heating system according to claim 1, characterized in that: In step three, the target imbalance rate is ±5%.

7. A method for eliminating low temperature difference and large flow rate operation mode of a heating system according to claim 1, characterized in that: In step three, start replacing the corresponding loop of the radiator at the bottom layer of each riser.

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