Method for calculating condensed water amount of steam overhead pipeline
By calculating the length of the non-condensing and condensing sections and the heat dissipation of the steam overhead pipeline in segments, the problem of the inability to detect the flow rate of steam condensate hot water in the heating network was solved, achieving high-precision calculation of condensate volume and reducing losses for heating companies.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DANYANG ZHONGXIN HUAHAI CLEAN ENERGY CO LTD
- Filing Date
- 2026-01-16
- Publication Date
- 2026-05-08
AI Technical Summary
Existing technology cannot accurately detect the hot water flow rate of steam condensation in heating networks, leading to discrepancies between heating companies and heat users when settling heat bills. This is especially true when there are many end-users, as it is difficult to determine the hot water content in the steam used by each user, resulting in losses for heating companies.
A method is used to calculate the condensate volume of an overhead steam pipe. By dividing the pipe into a non-condensing section and a condensing section, considering flow resistance and heat transfer loss, the length and heat dissipation of the non-condensing section and the condensing section are calculated using the principle of energy conservation and heat transfer formulas. The flow resistance loss is then corrected, and finally the condensate volume is calculated.
It enables accurate calculation of condensate volume in overhead steam pipelines with an error of less than 5%, providing a basis for heat settlement between heating companies and heat users and reducing losses for heating companies.
Smart Images
Figure CN121996871A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of heating engineering technology, specifically relating to a method for calculating the condensate volume of overhead steam pipelines. Background Technology
[0002] Heating steam is typically transported over long distances via overhead pipelines, some of which can stretch for tens of kilometers. Due to the high temperature of the heating steam, heat loss is inevitable in these pipelines. Therefore, as the steam flows through the pipeline, its enthalpy gradually decreases with continuous heat dissipation. When the enthalpy falls below the dry saturated steam enthalpy corresponding to the steam pressure, the steam condenses, transitioning from a superheated state to a wet saturated state. The condensed saturated water mixes with the steam in the form of tiny droplets. Currently, the flow meters installed on heating pipelines are usually gas flow meters. However, once the steam condenses into saturated water, gas flow meters cannot detect it, and liquid flow meters also cannot detect the tiny droplets mixed in with the steam. Therefore, a common problem in heating networks is the mismatch between the steam flow rate input by heating companies at the inlet of the network and the steam flow rate detected by users at the end of the network (the difference between the two is the flow rate of hot water condensed during the steam transportation process). This leads to significant discrepancies between heating companies and users regarding heat settlement (steam and hot water). Especially when there are many end-users, it is difficult to determine the hot water content in the steam used by each user. As a result, heating companies and users often settle accounts based on steam flow, while the hot water is essentially lost, causing high losses for the heating companies.
[0003] Therefore, it is meaningful to study the calculation method of steam condensate in overhead pipelines. It will provide a new way to deal with the problem of not being able to detect the flow rate of tiny droplets in steam, and thus resolve the settlement disputes between heating companies and heat users. Summary of the Invention
[0004] To address the problem of inaccurate detection of condensate flow rate in overhead steam pipelines, this invention provides a method for calculating condensate volume in overhead steam pipelines. This method has the advantages of advanced principle and simple calculation, and can calculate the condensate flow rate in pipelines under various conditions such as different pipeline lengths, pipe diameters, insulation layer thicknesses, and initial steam parameters, providing a basis for heat settlement between heating companies and heat users.
[0005] To achieve the above objectives, the present invention employs the following technical solution:
[0006] This invention provides a method for calculating the condensate volume in an overhead steam pipeline, comprising the following steps:
[0007] Calculate the theoretical non-condensable section length L1 of the steam overhead pipeline without considering resistance losses;
[0008] The flow resistance loss is calculated based on the theoretical non-condensing section length L1, and the actual non-condensing section pipe length L2 is obtained by correction.
[0009] Calculate the length L3 of the condensation section of the overhead steam pipeline;
[0010] The flow resistance loss is calculated based on the condensation section length L3, and the corrected condensation section pipe length L4 is obtained.
[0011] Calculate the heat loss φ1 per unit length of the modified condensation section pipe;
[0012] Based on the above calculation results, the actual condensate volume Q in the condensate section of the pipeline is calculated.
[0013] The principle behind the above scheme is as follows: to calculate the amount of condensate in a pipeline, the key is to determine the length of the condensate section and the heat dissipation per unit length. To achieve this, the heating pipeline can be divided into two parts: a non-condensing section and a condensate section. The total length of the pipeline is usually fixed (a known value), so to calculate the length of the condensate section, the length of the non-condensate section must first be calculated. The length of the non-condensate section is mainly determined by the initial superheated enthalpy of the steam and the heat dissipation rate of the pipeline. Simultaneously, it must be considered that flow resistance will cause a drop in steam pressure, resulting in a change in the superheated enthalpy of the steam, which in turn affects the length of the non-condensate section. Therefore, this method first calculates the theoretical non-condensate section length L1 of the overhead steam pipeline without considering resistance losses (i.e., calculated based on the initial superheated enthalpy of the steam and the heat dissipation rate of the pipeline), then calculates the flow resistance loss based on the L1 value, and corrects it to obtain the actual non-condensate section pipeline length L2. Then, subtracting the length of the non-condensing section from the total pipe length gives the condensing section length L3. Similarly, the flow resistance correction must be applied to the condensing section length L3 to finally obtain the pipe length L4 used to calculate the condensate volume. Then, the heat loss φ1 per unit length of the condensing section is calculated using the classical heat transfer formula. Multiplying L4 and φ1 gives the total heat loss of the condensing section. Finally, dividing the total heat loss of the condensing section by the latent heat of vaporization under the corresponding conditions gives the total condensate volume of the condensing section.
[0014] Furthermore, the theoretical non-condensing section length L1 of the steam overhead pipeline, without considering resistance losses, is specifically as follows:
[0015] Calculate the total thermal resistance R of the steam overhead pipe;
[0016] Calculate the heat loss φ3 of steam in the non-condensing section of the steam overhead pipeline;
[0017] Based on the total thermal resistance R of the steam overhead pipe, calculate the heat loss φ2 per unit length of the steam overhead pipe in the non-condensing section.
[0018] Calculate the theoretical non-condensing pipe length L1 = φ3 / φ2.
[0019] The principle and advantages of the above scheme are: (1) The critical state point for steam to condense is the dry saturation state, that is, if the steam enthalpy is higher than the dry saturation enthalpy, the steam will not condense; if the steam enthalpy is lower than the dry saturation enthalpy, the steam will begin to condense; (2) Based on the above principle, this method proposes to use the energy conservation method to calculate the length of the non-condensing section of the pipe, that is, first calculate the heat loss φ3 when the steam cools from the initial superheated state to the dry saturation state; then calculate the heat loss φ2 of the non-condensing section per unit length; therefore, the theoretical non-condensing pipe length L1=φ3 / φ2; (3) This method has the advantages of simple and reliable principle and small calculation workload.
[0020] Furthermore, the calculation of the total thermal resistance R of the steam overhead pipeline is specifically as follows:
[0021] Calculate the forced convection heat transfer resistance Rn of steam to the inner wall of the pipe;
[0022] Calculate the thermal resistance Rg from the inner wall of the tube to the outer wall of the tube;
[0023] Calculate the thermal resistance Rb from the inner surface of the insulation layer to the outer surface of the insulation layer;
[0024] Calculate the thermal resistance Rw of natural convection heat transfer from the outer surface of the insulation layer to the atmosphere;
[0025] The total thermal resistance of the steam overhead pipeline is R = Rn + Rg + Rb + Rw.
[0026] The principle and advantages of the above scheme are: it adopts the principle of superimposed series thermal resistance, which is widely used in the field of heat transfer and has the advantages of maturity and reliability.
[0027] Furthermore, the calculation of the steam heat loss φ3 in the non-condensing section of the steam overhead pipeline is specifically as follows:
[0028] Determine the initial enthalpy h1 of the steam at the pipe inlet;
[0029] Determine the theoretical dry saturated steam enthalpy h2 at the end of the non-condensing pipe without considering resistance loss;
[0030] Determine the initial steam flow rate Q1 at the pipeline inlet;
[0031] Based on the above data, the heat loss in the non-condensing section of the steam overhead pipeline is calculated to be φ3=Q1(h1-h2).
[0032] The advantages of the above scheme are: (1) h1 can be determined based on the initial steam pressure and temperature; (2) the corresponding dry saturated steam enthalpy h2 can be obtained by looking up the steam performance table based on the initial steam pressure; (3) the initial steam flow rate Q1 at the pipeline inlet is known. Therefore, this method has the advantage of simple calculation.
[0033] Furthermore, the calculation of the heat loss φ2 per unit length of the steam overhead pipe in the non-condensing section is specifically as follows:
[0034] The average heat transfer temperature difference Δt1 of the steam overhead pipeline is determined based on the average temperature of the superheated steam inside the pipeline and the ambient temperature.
[0035] Determine the heat loss coefficient β of the pipe fittings based on the number and size of the pipe supports and hangers;
[0036] The heat loss per unit length of the non-condensing section of the steam overhead pipe is φ2=Δt1(1+β) / R.
[0037] The advantages of the above scheme are: (1) The heat loss φ2 is calculated using the classic Newton cooling formula of heat transfer, which has high accuracy; (2) At the same time, this method takes into account the heat loss caused by pipe supports and hangers, so the heat loss coefficient β is used to correct the heat loss φ2, which further improves the calculation accuracy.
[0038] Furthermore, the calculation of flow resistance loss based on the theoretical non-condensing section length L1, and the correction to obtain the actual non-condensing section pipe length L2, are specifically as follows:
[0039] Calculate the flow resistance loss ΔP1 in the non-condensable pipe;
[0040] Determine the initial steam pressure P1 at the pipeline inlet;
[0041] Calculate the actual pressure at the end of the non-condensing pipe: P2 = P1 - ΔP1;
[0042] Determine the enthalpy of dry saturated steam h3 corresponding to the actual pressure P2 at the end of the non-condensable pipe;
[0043] Calculate the change in enthalpy of dry saturated steam caused by flow resistance at the outlet pressure of the non-condensable pipe, Δh1 = h2 - h3.
[0044] Calculate the elongation of the non-condensable pipe caused by the flow resistance, ΔL1 = Δh1 / φ2;
[0045] The actual length of the non-condensing pipe is calculated as L2 = L1 + ΔL1.
[0046] The principle and advantages of the above scheme are: (1) The dry saturated enthalpy h3 of steam is related to the pressure of steam. The lower the pressure, the smaller the dry saturated enthalpy h3 of steam; (2) Steam pressure is related to the steam flow resistance loss. That is to say, as the steam flows, the pressure gradually decreases and its enthalpy h3 becomes smaller; (3) The decrease of h3 will lead to the increase of Δh1 (Δh1=h2-h3), which will eventually lead to the length of the non-condensable pipe being extended by ΔL1 (ΔL1=Δh1 / φ2); (4) This method comprehensively corrects the influence of the resistance loss on the length of the non-condensable section of the pipe during the steam flow process, and further improves the calculation accuracy.
[0047] Furthermore, the calculation of the condensation section length L3 of the steam overhead pipeline specifically involves:
[0048] Determine the total length L of the overhead steam duct;
[0049] The length of the condensation section is L3 = L - L2.
[0050] The principle and advantages of the above scheme are: the theoretical condensation section length L3 can be calculated simply and reliably.
[0051] Furthermore, the calculation of flow resistance loss based on the condensation section length L3 to obtain the corrected condensation section pipe length L4 specifically involves:
[0052] Calculate the flow resistance loss ΔP2 within the length L3 of the condensate pipe;
[0053] Calculate the actual pressure at the end of the condensate pipe: P3 = P2 - ΔP2;
[0054] Determine the dry saturated steam enthalpy h4 corresponding to the actual pressure P3 at the end of the condensate pipe;
[0055] Calculate the change in enthalpy of dry saturated steam caused by flow resistance at the end of the condensation pipe, Δh2 = h3 - h4;
[0056] Calculate the elongation of the non-condensable pipe caused by the flow resistance: ΔL2 = Δh2 / φ2;
[0057] The actual length of the corrected condensate pipe is calculated as L4 = L3 - ΔL2.
[0058] The principle and advantages of the above scheme are: the flow resistance loss of steam in the condensation section will cause the length of the condensation section to change (for the same reason as above). Therefore, this method uses a similar method to make corrections, which improves the calculation accuracy of the actual length of the condensation pipeline.
[0059] Furthermore, the calculation of the heat loss φ1 per unit length of the actual condensation section of the pipe is specifically as follows:
[0060] The average heat transfer temperature difference Δt2 of the steam overhead pipeline is determined based on the average temperature of the wet saturated steam inside the pipeline and the ambient temperature.
[0061] The heat loss of the condensation section of the steam overhead pipeline per unit time and per unit length is φ1=Δt2(1+β) / R.
[0062] The advantages of the above scheme are: (1) The heat loss φ1 is calculated using the classic Newton cooling formula of heat transfer, which has high accuracy; (2) At the same time, this patent takes into account the heat loss caused by pipe supports and hangers, and therefore uses the heat loss coefficient β to correct the heat loss φ1, which further improves the calculation accuracy.
[0063] Furthermore, the calculation of the actual condensate volume Q in the condensation section of the pipeline is specifically as follows:
[0064] Determine the latent heat of vaporization q of steam;
[0065] The actual condensate volume in the condensate pipe is calculated as Q = L4×φ1 / q.
[0066] The principle and advantages of the above scheme are: (1) L4 represents the actual length of the condensation pipe, φ1 represents the heat loss of the condensation section pipe per unit length, so L4×φ1 is the total heat loss of the condensation pipe, and the latent heat of vaporization q represents the heat released when a unit mass of steam undergoes a phase change (i.e., changes from gaseous to liquid state); since the heat loss of the pipe is all from the latent heat of vaporization released when the steam condenses, the actual condensation volume of the condensation pipe Q = L4×φ1 / q; (2) This method has the advantages of being simple and reliable.
[0067] Compared with the prior art, the present invention has the following advantages:
[0068] This method first calculates the theoretical non-condensing section length L1 of the steam overhead pipeline without considering resistance losses. Then, it calculates the flow resistance loss based on L1 and corrects it to obtain the actual non-condensing section length L2. Subtracting the non-condensing section length from the total pipeline length yields the condensing section length L3. Similarly, flow resistance corrections are applied to L3 to obtain the final pipeline length L4 used for calculating condensate flow. Next, the heat loss φ1 per unit length of the condensing section is calculated using classical heat transfer formulas. Multiplying L4 and φ1 gives the total heat loss of the condensing section. Finally, dividing the total heat loss by the latent heat of vaporization under the corresponding conditions yields the total condensate flow. The error between the calculated condensate flow rate of the steam overhead pipeline and the actual value using this method is less than 5%. Attached Figure Description
[0069] Figure 1 This is a flowchart of a method for calculating the condensate volume of an overhead steam pipeline according to the present invention. Detailed Implementation
[0070] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.
[0071] like Figure 1 As shown in this embodiment, a method for calculating the condensate volume of an overhead steam pipeline includes the following steps:
[0072] 101: Calculate the theoretical non-condensing section length L1 of the steam overhead pipeline without considering resistance losses.
[0073] (1) Calculate the total thermal resistance R of the steam overhead pipeline. For the specific calculation method, see 101-1.
[0074] (2) Calculate the heat loss φ3 of steam in the non-condensing section of the steam overhead pipeline. For the specific calculation method, see 101-2.
[0075] (3) Based on the total thermal resistance R of the steam overhead pipe, calculate the heat loss φ2 per unit length of the steam overhead pipe in the non-condensing section. The specific calculation method is shown in 101-3.
[0076] (4) Based on the above calculation results, the theoretical non-condensing pipe length L1 = φ3 / φ2 is calculated;
[0077] 101-1: The total thermal resistance R of the steam overhead pipe is calculated, including:
[0078] (1) Calculate the forced convection heat transfer resistance Rn of steam to the inner wall of the pipe. Specifically, the heat transfer between steam and the inner wall of the pipe belongs to the forced convection heat transfer of turbulent flow in the tube channel. Therefore, the Nusselt number is first calculated using the Dittus–Boelter formula. Then, according to the definition of the Nusselt number formula... Calculate the convective heat transfer coefficient h. n Finally, we obtain Rn = 1 / h n .
[0079] (2) Calculate the thermal resistance Rg from the inner wall of the pipe to the outer wall of the pipe. Specifically, according to the material of the pipe wall, find the thermal conductivity λg of the pipe wall and calculate Rg=1 / λg.
[0080] (3) Calculate the thermal resistance Rb from the inner surface of the insulation layer to the outer surface of the insulation layer. Specifically, according to the material of the insulation material, find the thermal conductivity λb of the insulation material and calculate Rb=1 / λb.
[0081] (4) Calculate the natural convection heat transfer resistance Rw from the outer surface of the insulation layer to the atmosphere. Specifically, the heat transfer between the outer surface of the insulation layer and the atmosphere is a natural convection heat transfer of the fluid flowing across the single tube. Therefore, the Nusselt number is calculated using the Churchill-Bernslein formula. Then, according to the definition of the Nusselt number formula... The convective heat transfer coefficient hw is calculated; finally, Rw = 1 / hw is obtained.
[0082] (5) The total thermal resistance of the steam overhead pipeline is R = Rn + Rg + R b +Rw.
[0083] 101-2: The calculation of the steam heat loss φ3 in the non-condensing section of the steam overhead pipeline includes:
[0084] (1) Determine the initial enthalpy h1 of the steam at the inlet of the pipeline. Specifically, the initial enthalpy h1 of the steam can be obtained by referring to the steam performance table based on the pressure and temperature of the steam at the inlet of the pipeline.
[0085] (2) Determine the theoretical dry saturated steam enthalpy h2 at the end of the non-condensable pipe without considering resistance loss. Specifically, the theoretical dry saturated steam enthalpy h2 at the end of the non-condensable pipe can be obtained by referring to the steam performance table based on the steam pressure at the pipe inlet.
[0086] (3) Determine the initial steam flow rate Q1 at the pipeline inlet. Specifically, the initial steam flow rate Q1 at the pipeline inlet can usually be read from the steam flow meter at the pipeline inlet (or specified by the user).
[0087] (4) Based on the above data, the heat loss of the steam overhead pipeline in the non-condensing section is calculated as φ3=Q1(h1-h2).
[0088] 101-3: Based on the total thermal resistance R of the steam overhead pipeline, calculate the heat loss φ2 per unit length of the non-condensing section of the steam overhead pipeline.
[0089] (1) Based on the average temperature of the superheated steam in the pipeline and the ambient temperature, determine the average heat transfer temperature difference Δt1 of the steam overhead pipeline. Specifically: (a) The initial steam temperature t2 at the pipeline inlet is a known value (usually measured by a thermocouple at the pipeline inlet or provided by the user), the end temperature t3 of the non-condensable pipeline is the saturation temperature corresponding to the pressure of the steam at the pipeline inlet, and the ambient temperature t4 is determined according to the actual ambient temperature of the user's local area; (b) The average temperature of the superheated steam in the pipeline t5 = (t2 + t3) / 2; (c) Finally, calculate the average heat transfer temperature difference Δt1 = t5 - t4.
[0090] (2) Determine the heat loss coefficient β of the pipe fittings based on the number and size of the pipe supports and hangers. Specifically, first, set the benchmark heat loss coefficient β based on experience, and then correct the heat loss coefficient β based on the measured values of the inlet steam flow and outlet steam flow of the pipe when a single user is running the heating pipe. Finally, make the error between the calculated value and the measured value less than 5%.
[0091] (3) The heat loss per unit length of the non-condensing section of the steam overhead pipeline is φ2 = Δt1(1+β) / R.
[0092] 102: Calculate the flow resistance loss based on the theoretical non-condensing section length L1, and then correct it to obtain the actual non-condensing section pipe length L2.
[0093] (1) Calculate the flow resistance loss ΔP1 of the non-condensable pipeline. Specifically, to calculate the flow resistance loss of the steam pipeline, first, find the density, viscosity and other physical properties by referring to the steam performance table based on the steam state parameters (temperature, pressure); then, combine the known steam flow rate and pipe diameter to calculate the Reynolds number of the steam in the pipeline and determine the flow state (laminar or turbulent); then, select the corresponding friction coefficient formula according to the flow state (such as the Moody diagram method commonly used for turbulent flow), and calculate the friction loss by combining the pipe length, pipe diameter and steam velocity; finally, find the local resistance coefficient of each elbow and valve according to the type (such as 90° elbow, gate valve), and calculate the local resistance loss by superimposing them. The final total resistance loss is the sum of the friction loss and the local loss.
[0094] (2) Determine the initial steam pressure P1 at the pipeline inlet. Specifically, the initial steam pressure P1 is obtained by measuring the pressure at the pipeline inlet.
[0095] (3) Calculate the actual pressure at the end of the non-condensing pipe: P2 = P1 - ΔP1;
[0096] (4) Determine the dry saturated steam enthalpy h3 corresponding to the actual pressure P2 at the end of the non-condensing pipe. Specifically, the dry saturated steam enthalpy h3 corresponding to each steam pressure is unique. By looking up the steam performance table, the dry saturated steam enthalpy h3 corresponding to the actual pressure P2 at the end of the non-condensing pipe can be determined.
[0097] (5) Calculate the change in enthalpy of dry saturated steam caused by the flow resistance at the outlet pressure of the non-condensable pipe, Δh1=h2-h3;
[0098] (6) Calculate the elongation of the non-condensable pipe caused by the flow resistance, ΔL1=Δh1 / φ2;
[0099] (7) Calculate the actual length of the non-condensing pipe L2=L1+ΔL1.
[0100] 103: Calculate the length L3 of the condensation section in the overhead steam pipeline.
[0101] (1) Determine the total length L of the steam overhead pipeline. Specifically, the total length L of the steam overhead pipeline can be determined according to the construction drawings of the steam overhead pipeline or provided by the user.
[0102] (2) The length of the condensation section L3 = L - L2.
[0103] 104: Calculate the flow resistance loss based on the condensation section length L3 to obtain the corrected condensation section pipe length L4.
[0104] (1) Calculate the flow resistance loss ΔP2 within the length L3 of the condensing pipe. Specifically, the method for determining ΔP2 is the same as the method for determining the flow resistance loss ΔP1 of the non-condensing pipe, and will not be repeated here.
[0105] (2) Calculate the actual pressure at the end of the condensate pipe: P3 = P2 - ΔP2;
[0106] (3) Determine the dry saturated steam enthalpy h4 corresponding to the actual pressure P3 at the end of the condensing pipe. Specifically, the dry saturated steam enthalpy h4 corresponding to each steam pressure is unique. By looking up the steam performance table, the dry saturated steam enthalpy h4 corresponding to the actual pressure P3 at the end of the condensing pipe can be determined.
[0107] (4) Calculate the change in enthalpy of dry saturated steam corresponding to the pressure at the end of the condensation pipe caused by the flow resistance, Δh2 = h3 - h4;
[0108] (5) Calculate the elongation of the non-condensable pipe caused by the flow resistance, ΔL2=Δh2 / φ2;
[0109] (6) Calculate the actual length of the modified condensate pipe L4 = L3 - ΔL2.
[0110] 105: Calculate the heat loss φ1 per unit length of the modified condensation section pipe.
[0111] (1) Based on the wet saturated steam temperature in the pipeline and the ambient temperature, the average heat transfer temperature difference Δt2 of the steam overhead pipeline is determined as follows: (a) The actual pressure P2 at the end of the non-condensing pipeline is the inlet pressure of the condensing pipeline. Therefore, the saturated temperature t6 obtained from the steam performance table based on P2 is the inlet temperature of the condensing pipeline. The saturated temperature t7 obtained from the steam performance table based on the actual pressure P3 at the end of the condensing pipeline is the outlet temperature of the condensing pipeline. The ambient temperature t4 is determined based on the actual ambient temperature of the user's local area; (b) The average steam temperature in the condensing pipeline t8 = (t6 + t7) / 2; (c) The average heat transfer temperature difference Δt2 is finally calculated as t8 - t4.
[0112] (2) The heat loss of the condensation section of the steam overhead pipeline per unit time and per unit length is φ1=Δt2(1+β) / R.
[0113] 106: Calculate the actual condensate volume Q in the condensate section of the pipe.
[0114] (1) Determine the latent heat of vaporization q of the steam. Specifically, it can be obtained by referring to the steam performance table based on the average pressure of the condensation section pipeline P4=(P2+P3) / 2.
[0115] (2) Calculate the actual condensate volume in the condensate pipe Q = L4×φ1 / q.
[0116] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
[0117] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A method for calculating the condensate volume of an overhead steam pipeline, characterized in that, Includes the following steps: Calculate the theoretical non-condensable section length L1 of the steam overhead pipeline without considering resistance losses; The flow resistance loss is calculated based on the theoretical non-condensing section length L1, and the actual non-condensing section pipe length L2 is obtained by correction. Calculate the length L3 of the condensation section of the overhead steam pipeline; The flow resistance loss is calculated based on the condensation section length L3, and the corrected condensation section pipe length L4 is obtained. Calculate the heat loss φ1 per unit length of the modified condensation section pipe; Based on the above calculation results, the actual condensate volume Q in the condensate section of the pipeline is calculated.
2. The method for calculating the condensate volume of an overhead steam pipeline according to claim 1, characterized in that, The theoretical non-condensing section length L1 of the steam overhead pipeline, without considering resistance losses, is specifically as follows: Calculate the total thermal resistance R of the steam overhead pipe; Calculate the heat loss φ3 of steam in the non-condensing section of the steam overhead pipeline; Based on the total thermal resistance R of the steam overhead pipe, calculate the heat loss φ2 per unit length of the steam overhead pipe in the non-condensing section. Calculate the theoretical non-condensing pipe length L1 = φ3 / φ2.
3. The method for calculating the condensate volume of an overhead steam pipeline according to claim 2, characterized in that, The calculation of the total thermal resistance R of the steam overhead pipeline is specifically as follows: Calculate the forced convection heat transfer resistance Rn of steam to the inner wall of the pipe; Calculate the thermal resistance Rg from the inner wall of the tube to the outer wall of the tube; Calculate the thermal resistance Rb from the inner surface of the insulation layer to the outer surface of the insulation layer; Calculate the thermal resistance Rw of natural convection heat transfer from the outer surface of the insulation layer to the atmosphere; The total thermal resistance of the steam overhead pipeline is R = Rn + Rg + Rb + Rw.
4. A method for calculating the condensate volume of an overhead steam pipeline according to claim 2, characterized in that, The calculation of the steam loss heat φ3 in the non-condensing section of the steam overhead pipeline is specifically as follows: Determine the initial enthalpy h1 of the steam at the pipe inlet; Determine the theoretical dry saturated steam enthalpy h2 at the end of the non-condensing pipe without considering resistance loss; Determine the initial steam flow rate Q1 at the pipeline inlet; Based on the above data, the heat loss φ3 = Q1(h1 - h2) in the non-condensing section of the steam overhead pipeline is calculated.
5. A method for calculating the condensate volume of an overhead steam pipeline according to claim 2, characterized in that, The calculation of the heat loss φ2 per unit length of the steam overhead pipeline in the non-condensing section is specifically as follows: The average heat transfer temperature difference Δt1 of the steam overhead pipeline is determined based on the average temperature of the superheated steam inside the pipeline and the ambient temperature. Determine the heat loss coefficient β of the pipe fittings based on the number and size of the pipe supports and hangers; The heat loss per unit length of the non-condensing section of the steam overhead pipe is φ2=Δt1(1+β) / R.
6. A method for calculating the condensate volume of an overhead steam pipeline according to claim 1, characterized in that, The calculation of flow resistance loss based on the theoretical non-condensing section length L1, and the correction to obtain the actual non-condensing section pipe length L2, are as follows: Calculate the flow resistance loss ΔP1 in the non-condensable pipe; Determine the initial steam pressure P1 at the pipeline inlet; Calculate the actual pressure at the end of the non-condensing pipe: P2 = P1 - ΔP1; Determine the enthalpy of dry saturated steam h3 corresponding to the actual pressure P2 at the end of the non-condensable pipe; Calculate the change in enthalpy of dry saturated steam caused by flow resistance at the outlet pressure of the non-condensable pipe, Δh1 = h2 - h3. Calculate the elongation of the non-condensable pipe caused by the flow resistance: ΔL1 = Δh1 / φ2; The actual length of the non-condensing pipe is calculated as L2 = L1 + ΔL1.
7. A method for calculating the condensate volume of an overhead steam pipeline according to claim 1, characterized in that, The calculation of the condensation section length L3 of the steam overhead pipeline is specifically as follows: Determine the total length L of the overhead steam duct; The length of the condensation section is L3 = L - L2.
8. A method for calculating the condensate volume of an overhead steam pipeline according to claim 1, characterized in that, The calculation of flow resistance loss based on the condensation section length L3, resulting in the corrected condensation section pipe length L4, is as follows: Calculate the flow resistance loss ΔP2 within the length L3 of the condensate pipe; Calculate the actual pressure at the end of the condensate pipe: P3 = P2 - ΔP2; Determine the dry saturated steam enthalpy h4 corresponding to the actual pressure P3 at the end of the condensate pipe; Calculate the change in enthalpy of dry saturated steam caused by flow resistance at the end of the condensation pipe, Δh2 = h3 - h4; Calculate the elongation of the non-condensable pipe caused by the flow resistance: ΔL2 = Δh2 / φ2; The actual length of the corrected condensate pipe is calculated as L4 = L3 - ΔL2.
9. A method for calculating the condensate volume of an overhead steam pipeline according to claim 1, characterized in that, The calculation of the heat loss φ1 per unit length of the actual condensation section of the pipe is specifically as follows: The average heat transfer temperature difference Δt2 of the steam overhead pipeline is determined based on the average temperature of the wet saturated steam inside the pipeline and the ambient temperature. The heat loss per unit time and per unit length of the condensation section of the steam overhead pipeline is φ1=Δt2(1+β) / R.
10. A method for calculating the condensate volume of an overhead steam pipeline according to claim 1, characterized in that, The calculated condensate volume Q in the actual condensation section of the pipe is specifically as follows: Determine the latent heat of vaporization q of steam; The actual condensate volume in the condensate pipe is calculated as Q = L4×φ1 / q.