CN106640004B - Method and device for calculating steam thermodynamic parameter of steam injection boiler outlet - Google Patents

Abstract

The application discloses a method and a device for calculating steam thermodynamic parameters of an outlet of a ground gas pipeline boiler, wherein the method comprises the following steps: obtaining calculation parameters, wherein the calculation parameters comprise: steam temperature and dryness at a steam injection well head, parameters of a ground pipeline and environmental parameters outside the ground pipeline; according to the calculation parameters, iteratively calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead; and (3) establishing an energy control equation according to an energy balance law under the conditions of neglecting the pressure in the ground pipeline and gravity change, and determining the dryness of the steam at the outlet of the steam injection boiler.

Description

Method and device for calculating steam thermodynamic parameter of steam injection boiler outlet

Technical Field

The invention relates to the field of heavy oil thermal recovery in the field of oil exploitation, in particular to a method and a device for calculating a steam thermodynamic parameter of an outlet of a steam injection boiler of a ground gas transmission pipeline.

Background

Heavy oil refers to high viscosity heavy crude oil having a viscosity of greater than 50mp · s (millipascal · s) under formation conditions, or a viscosity of the degassed crude oil at reservoir temperature of 1000 to 10000mp · s. Because the thick oil has high viscosity, the thick oil has poor flowing property and even can not flow under certain oil layer conditions, and the thick oil is difficult to recover. In the oil exploitation of oil fields, because thick oil has the characteristics of special high viscosity and high freezing point, the thick oil has poor mobility in reservoirs and mineshafts, and the conventional exploitation recovery ratio is low, namely normal economic yield cannot be ensured. To ensure reasonable recovery, oil is often recovered by reducing the viscosity of the crude oil.

The technology for exploiting the thick oil by steam injection thermal power can reduce the viscosity of the thick oil, improve the fluidity ratio, reduce the saturation of residual oil and improve the oil displacement efficiency. The high-temperature high-pressure steam used in the steam-injection thermal heavy oil recovery technology is generated in a steam injection station, then is conveyed to a wellhead through a ground pipeline, and is injected into a stratum through a shaft from the wellhead. The steam inevitably has heat loss in the migration process, and in order to ensure that the steam reaching the bottom of the well keeps higher dryness and achieve better steam injection effect, the design of the steam thermal parameters at the outlet of the steam injection boiler is crucial.

The invention provides a method for calculating well head steam parameters by taking a steam injection boiler outlet as a starting point, and further calculating thermodynamic parameters when steam reaches a well bottom.

Disclosure of Invention

The invention aims to provide a method and a device for calculating steam thermodynamic parameters of an outlet of a steam injection boiler of a ground gas transmission pipeline, so that the steam thermodynamic parameters of the outlet of the steam injection boiler can be determined, and a reliable basis is provided for boiler steam injection parameter design.

In order to achieve the above object, the present invention provides a method for calculating a steam thermodynamic parameter at an outlet of a steam injection boiler, comprising:

obtaining calculation parameters, wherein the calculation parameters comprise: steam pressure, temperature and dryness of a steam injection wellhead, parameters of a ground pipeline and environmental parameters outside the ground pipeline;

according to the calculation parameters, iteratively calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead;

and (3) establishing an energy control equation according to an energy balance law under the conditions of neglecting the pressure in the ground pipeline and gravity change, and determining the dryness of the steam at the outlet of the ground pipeline steam injection boiler.

As a preferred embodiment, the calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead comprises:

setting the outer surface temperature of a preset heat insulation layer on the pipeline;

calculating the total thermal resistance of the pipeline according to the temperature of the outer surface of the preset heat insulation layer, and calculating the heat loss of the pipeline gas transmission along the way according to the total thermal resistance of the pipeline; calculating the temperature of the outer surface of the heat insulation layer according to the heat loss of the pipeline gas transmission along the way;

and repeating iteration, and when the calculated value of the external surface temperature of the heat-insulating layer and the set value meet the first preset precision, determining the external surface temperature of the heat-insulating layer of the pipeline to obtain the heat loss of steam from the outlet of the steam injection boiler to the steam injection well head.

As a preferred embodiment, the heat loss per unit length of surface pipeline is calculated using the following calculation:

in the above formula, q is the heat loss in the ground pipeline of unit length in unit time, and the unit is kilocalorie/(hour meter); t is_sIs the steam temperature in degrees celsius; t is_aIs ambient temperature, in degrees celsius; r is the total thermal resistance value in unit length of ground pipeline, and the unit is (meter.h.degree centigrade)/kilocalorie.

As a preferred embodiment, the calculating the total thermal resistance of the surface pipeline comprises:

the total thermal resistance R of the surface pipeline is calculated according to the following formula:

in the above formula, R is the total thermal resistance of the ground pipeline, R₁Thermal resistance value, R, for convective heat transfer of steam and liquid film layer in ground pipeline₂Thermal resistance, R, for convective heat transfer of steam and dirt layer in ground pipeline₃Thermal resistance, R, for heat conduction of pipe wall₄Thermal resistance, R, for heat conduction of the insulating layer₅The thermal resistance value of the ground pipeline to the forced convection heat transfer of air is expressed in the unit of (meter, hour, centigrade)/kilocalorie; h is_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient of the fouling layer, h_fcThe forced convection heat coefficient on the outer surface of the heat insulation layer is kilocalorie/(square meter, hour and centigrade degrees); lambda [ alpha ]_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter;

the forced convection heat exchange of the ground pipeline to the air comprises convection heat exchange from the outer surface of the heat insulating layer to the atmosphere and radiation heat exchange from the outer wall of the pipeline to the atmosphere;

the heat convection coefficient h from the outer surface of the heat insulating layer to the atmosphere_fc', its calculation formula is as follows:

in the above formula, λ_aThe thermal conductivity coefficient of air is expressed in kilocalories/(meter.h.degree centigrade); re is Reynolds number and is calculated by the following formula:

Re＝ν_aD_s/υ_a

in the above formula, v_aWind speed, unit meter/second; upsilon is_aIs the kinematic viscosity of air in square meters per second; d_sThe outer diameter of the heat insulation layer is unit meter; wherein C, n are carried out according to a predetermined rule based on ReSelecting;

radiant heat transfer coefficient h from the outer wall of the tube to the atmosphere_fc", its calculation formula is as follows:

in the above formula, epsilon is the blackness outside the tube wall, and has no dimension; t is_aIs the average temperature of air in degrees centigrade; t is_wThe temperature of the outer wall of the heat insulation layer is in units of centigrade.

As a preferred embodiment, the heat insulating layer outer surface temperature is calculated using the following calculation formula:

in the above formula, h_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient, lambda, of the fouling layer_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter; q is the heat loss in the ground pipeline per unit length in unit time, in kilocalories/(h.m); t is_sIs the steam temperature in degrees celsius; t is_wThe temperature of the outer wall of the heat insulation layer is in units of centigrade.

As a preferred embodiment, the step of calculating the dryness fraction according to the law of energy balance comprises:

the following energy control equation is established:

steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a steam dryness calculation expression of the outlet of the steam injection boiler

Thus, the steam quality at the outlet of the boiler is calculated by the formula:

in the above formula, q is the heat loss of steam in the ground pipeline per unit length of unit time, and the unit is kilocalories/(hour meter); z is the distance between the calculated position and the boiler outlet in meters; g is saturated steam mass flow, unit kilogram/hour; l is_vPotential heat of vaporization, kcal/kg; x is the number of_uThe steam dryness is the steam dryness of a steam injection wellhead (the tail end of a ground pipeline) and is dimensionless;

the above latent heat of vaporization L_vThe difference between the enthalpy of the dry saturated steam and the enthalpy of the saturated water is calculated by the following formula:

L_v＝273×(374.15-T)^0.38＝h_g-h_l；

h_lthe enthalpy of saturated water is calculated by the following formula in kcal/kg:

h_lthe enthalpy of saturated water is expressed in kilocalories/kilogram; the calculation formula is as follows:

h_g＝12500+1.88T-3.7×10^-6T^3.2

in the above formula, T is the steam temperature in degrees celsius.

In order to achieve the above object, the present invention further provides a method for calculating a steam thermodynamic parameter at an outlet of a steam injection boiler, comprising:

obtaining calculation parameters, wherein the calculation parameters comprise: calculating the step length according to the steam pressure, the temperature, the dryness, the steam injection rate, the parameters of the ground pipeline and the environmental parameters outside the ground pipeline of the steam injection wellhead;

calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

according to the calculation parameters, establishing a control equation of the steam pressure drop gradient in the ground pipeline through a momentum conservation law, and determining the temperature and the pressure of the steam at any position of the ground pipeline;

and dividing the pipeline infinitesimal section on the length of the ground pipeline according to the calculation step length, establishing an energy control equation, and determining the dryness of the steam at the outlet of the steam-injection boiler by iterative calculation of mutually coupled heat loss, pressure and dryness by taking the dryness of the steam-injection well as an initial condition.

Taking the outlet of the boiler as the origin of coordinates and the flow direction of the steam along the pipeline as the Z-axis direction, a control equation of the steam pressure drop gradient in the ground pipeline is established according to the momentum conservation principle:

according to the control equation, dividing the whole ground pipeline into a plurality of calculation step lengths by using a numerical method, wherein the length of each calculation step length is △ z, and integrating the above formula in each section;

order to

v_m＝(v_out+v_in)/2

Obtaining a calculation formula for determining the steam pressure at any position of the surface pipeline:

in the above formula, p_inCalculating the steam pressure at the inlet in megapascals for each step of the surface pipeline; p is a radical of_outCalculating the steam pressure at the outlet for each step of the surface pipeline in megapascals; f. of_mIs the coefficient of friction resistance of the wet steam fluid, dimensionless; rho_mDensity of wet steam fluid in kilograms per cubic meter; v is_mIs the average velocity of the wet vapor stream in meters per second; v. of_inCalculating the steam velocity at the inlet of each step of the ground pipeline in meters per second; v. of_outCalculating the steam velocity at the outlet of the step size for each of the surface pipelinesDegree, in meters per second; g is gravity acceleration in meters per square second; r is_iIs the inner diameter of the gas transmission pipeline in meters; a is the flow cross-sectional area in square meters; g is the mass flow of the wet steam fluid, and the unit is kilogram/second;

the rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

in the above formula f_mIs the coefficient of friction resistance of the wet steam, which is determined from the reynolds number Re of the saturated wet steam at the average pressure and the average temperature;

H_gthe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter.

In a preferred embodiment, the steam in the surface pipeline is saturated wet steam, and the formula for calculating the steam temperature at any position of the surface pipeline is as follows:

T_in＝195.94p_in ^0.225-17.8

in the above formula, T_inCalculating step size entry for each step of surface pipelineThe steam temperature of (a), in degrees centigrade; p is a radical of_inSteam pressure at the inlet in mpa is calculated for each step of the surface pipeline.

As a preferred embodiment, the determining the dryness of the steam at the outlet of the steam injection boiler comprises the following steps:

setting a preset dryness drop on the micro section of the pipeline;

calculating the dryness according to an energy balance law, repeatedly iterating, and determining the dryness drop of the micro element section of the pipeline when the dryness drop calculation value of the micro element section of the pipeline meets a second preset precision with a set value;

and circularly calculating to the whole ground pipeline, and determining the dryness of the steam at the outlet of the steam injection boiler.

As a preferred embodiment, the step of calculating the dryness fraction according to the law of energy balance comprises:

the following energy control equation is established:

steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a calculation expression of the steam dryness at any position of the ground pipeline

Wherein:

C₁＝G(h_g-h_l)

thus, the boiler outlet steam dryness calculation formula is:

in the above formula, h_gEnthalpy of saturated steam, in kcal/kg; h is_lIs the enthalpy of saturated water, in kcal/kg; x is steam dryness without dimension; g is gravity acceleration in meters per square second; g is steam discharge capacity of a steam injection wellhead, and unit kilogram/hour; q is heat loss per unit length of pipeline in unit time, and unit kilocalorie/(hour meter); rho_mSaturated wet steam density in kilograms per cubic meter; a is the cross-sectional area of the pipeline in square meters; theta is the inclination angle of the pipeline and unit degree;

the rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

H_gthe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter.

In order to achieve the above object, the present invention further provides a device for calculating thermal parameters of steam in a ground steam injection pipeline, comprising:

a parameter obtaining module, configured to obtain calculation parameters, where the calculation parameters include: steam pressure, temperature and dryness of a steam injection wellhead, parameters of a ground pipeline and environmental parameters outside the ground pipeline;

the heat loss determining module is used for iteratively calculating the heat loss amount of steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

and the dryness determining module is used for establishing an energy control equation according to the energy balance law under the condition of neglecting the pressure and gravity change in the ground pipeline and determining the dryness of the steam at the outlet of the steam injection boiler.

In order to achieve the above object, the present invention further provides a device for calculating thermal parameters of steam in a ground steam injection pipeline, comprising:

a parameter obtaining module, configured to obtain calculation parameters, where the calculation parameters include: calculating the step length according to the steam pressure, the temperature, the dryness, the steam injection rate, the parameters of the ground pipeline and the environmental parameters outside the ground pipeline of the steam injection wellhead;

the heat loss determining module is used for iteratively calculating the heat loss amount of steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

the pressure and temperature determination module is used for establishing a control equation of the steam pressure drop gradient in the ground pipeline according to the calculation parameters and the momentum conservation law, and determining the temperature and the pressure of the steam at any position of the ground pipeline;

and the dryness determining module is used for dividing the pipeline infinitesimal section on the length of the ground pipeline according to the calculation step length, establishing an energy control equation, and determining the dryness of the steam at the outlet of the steam injection boiler by using the dryness of the steam injection well as an initial condition and through the iterative calculation of the heat loss, the pressure and the dryness which are coupled with each other.

The invention has the characteristics and advantages that: according to the method for calculating the steam thermodynamic parameter of the steam injection boiler outlet, steam pressure, temperature and dryness at the steam injection well head are obtained, the steam pressure in the ground pipeline is subjected to numerical analysis, a pressure equation of the steam along the ground pipeline is established, and the pressure of the steam at any point along the ground pipeline is determined, so that the steam thermodynamic parameter of the steam injection boiler outlet is determined, and a reliable basis is provided for the design of the steam injection parameter of the boiler.

Furthermore, because the calculation of the heat loss and the dryness fraction is based on a function of temperature, an energy control equation is established in the steam thermal parameters at the outlet of the steam injection boiler based on the obtained accurate temperature according to the energy balance law, and the heat loss and the dryness fraction of the steam at the outlet of the steam injection boiler on the ground pipeline are solved through circulating calculation, so that the heat loss and the dryness fraction of the steam at the outlet of the steam injection boiler obtained by the method are high in precision.

Specific embodiments of the present invention are disclosed in detail with reference to the following description and drawings, indicating the manner in which the principles of the invention may be employed. It should be understood that the embodiments of the invention are not so limited in scope. The embodiments of the invention include many variations, modifications and equivalents within the spirit and scope of the appended claims.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

FIG. 1 is a flowchart illustrating a method for calculating a steam thermodynamic parameter at an outlet of a steam injection boiler according to an embodiment of the present invention;

FIG. 2 is a flowchart illustrating a method for calculating a steam thermodynamic parameter at an outlet of a steam injection boiler according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a ground steam injection pipeline according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a calculation device for the steam thermal parameters at the outlet of the steam injection boiler according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a device for calculating the steam thermodynamic parameter at the outlet of the steam injection boiler according to an embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Fig. 1 is a step diagram of a method for calculating a steam thermodynamic parameter in a ground steam injection pipeline according to an embodiment of the present invention. The invention discloses a method for calculating steam thermodynamic parameters of an outlet of a steam injection boiler, which comprises the following steps of:

s10, obtaining calculation parameters, wherein the calculation parameters comprise: steam pressure, temperature and dryness of a steam injection wellhead, parameters of a ground pipeline and environmental parameters outside the ground pipeline;

s12, iteratively calculating the heat loss amount of steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

s14, establishing an energy control equation according to the energy balance law under the condition of neglecting the pressure and gravity change in the ground pipeline, and determining the dryness of the steam at the outlet of the steam injection boiler.

Specifically, the iteratively calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead (step S12) according to the calculation parameters includes:

firstly, setting the outer surface temperature of a preset heat insulation layer on the pipeline; in this embodiment, when setting for predetermine heat insulating layer surface temperature on the pipeline, can set for according to the temperature value of the steam that steam injection well head measured, for example steam injection well head steam's temperature is 300 degrees centigrade, then can set for heat insulating layer surface temperature and be for being less than a certain numerical value of steam injection well head steam temperature, for example can be 200 degrees centigrade to do benefit to and reduce iterative number of times.

Then, the total thermal resistance of the pipeline is calculated according to the temperature of the outer surface of the preset heat insulation layer, referring to fig. 3, the ground pipeline can be an air film layer, a heat insulation layer, a pipe wall, a dirt layer and a liquid film layer from the outside to the inside respectively; wherein the total thermal resistance R of the ground pipeline is calculated according to the following formula:

in the above formula, R is the total thermal resistance of the ground pipeline, R₁Thermal resistance value, R, for convective heat transfer of steam and liquid film layer in ground pipeline₂Thermal resistance, R, for convective heat transfer of steam and dirt layer in ground pipeline₃Is a pipe wallThermal resistance of heat conduction, R₄Thermal resistance, R, for heat conduction of the insulating layer₅The thermal resistance value of the ground pipeline to the forced convection heat transfer of air is expressed in the unit of (meter, hour, centigrade)/kilocalorie; h is_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient of the fouling layer, h_fcThe forced convection heat coefficient on the outer surface of the heat insulation layer is kilocalorie/(square meter, hour and centigrade degrees); lambda [ alpha ]_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter.

Of course, when the ground pipelines have different structures, the corresponding ground pipeline total thermal resistance value R may also be adaptively changed, which is not described herein again.

In the present embodiment, the forced convection heat transfer of the ground pipeline to the air includes convection heat transfer from the outer surface of the heat insulating layer to the atmosphere and radiation heat transfer from the outer wall of the pipe to the atmosphere; specifically, the method comprises the following steps:

the heat convection coefficient h from the outer surface of the heat insulating layer to the atmosphere_fc', its calculation formula is as follows:

in the above formula, λ_aThe thermal conductivity coefficient of air is expressed in kilocalories/(meter.h.degree centigrade); re is Reynolds number and is calculated by the following formula:

Re＝ν_aD_s/υ_a

in the above formula, v_aWind speed, unit meter/second; upsilon is_aIs the kinematic viscosity of air in square meters per second; d_sThe outer diameter of the heat insulation layer is unit meter; wherein C and n are selected according to Re according to a preset rule.

In the present embodiment, the parameter C, n can be selected according to Re in table 1.

TABLE 1

Re	5-80	80-5×103	5×103-5×104	>5×104
					C	0.81	0.625	0.197	0.023
n	0.40	0.46	0.6	0.8

In this embodiment, the radiant heat transfer coefficient h from the outer wall of the tube to the atmosphere_fc", its calculation formula is as follows:

in the above formula, epsilon is the blackness outside the tube wall, and has no dimension; t is_aIs the average temperature of air in degrees centigrade; t is_wThe temperature of the outer wall of the heat insulation layer is in units of centigrade.

In this embodiment, the radiation from the outer wall of the pipe to the atmosphere can be calculated by presetting the outer surface temperature of the heat insulating layer according to the formulaHeat transfer coefficient h_fc", and then the radiation heat transfer coefficient h is from the outer wall of the tube to the atmosphere_fc"calculate the total thermal resistance R of the surface pipeline.

Then, calculating the heat loss q of the pipeline gas transmission along the way through the total thermal resistance R of the pipeline; wherein the heat loss q per unit length of the ground pipeline can be calculated by the following calculation formula:

in the above formula, q is the heat loss in the ground pipeline of unit length in unit time, and the unit is kilocalorie/(hour meter); t is_sIs the steam temperature in degrees celsius; t is_aIs ambient temperature, in degrees celsius; r is the total thermal resistance value in unit length of ground pipeline, and the unit is (meter.h.degree centigrade)/kilocalorie.

In the present embodiment, the calculated value of the outer surface temperature of the heat insulating layer is calculated based on the calculated heat loss q along the gas transport path of the pipeline by using the following calculation formula:

in the above formula, h_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient, lambda, of the fouling layer_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter; q is the heat loss in the ground pipeline per unit length in unit time, in kilocalories/(h.m); t is_sIs the steam temperature in degrees celsius; t is_wThe temperature of the outer wall of the heat insulation layer is in units of centigrade.

And finally, repeatedly iterating, and when the calculated value of the outer surface temperature of the heat-insulating layer and the set value meet the first preset precision, determining the outer surface temperature of the heat-insulating layer of the pipeline to obtain the heat loss of steam from the outlet of the steam injection boiler to the steam injection wellhead.

In the present embodiment, the first predetermined accuracy may be set according to actual accuracy requirements, and the smaller the value set by the first predetermined accuracy, the more accurate the obtained heat insulation layer outer surface temperature is, relatively speaking, and accordingly, the higher the accuracy of the obtained heat loss of the pipe line is.

In summary, the process of iterative iteration specifically includes: and obtaining corresponding total thermal resistance by setting the temperature of the outer surface of the heat insulating layer, obtaining corresponding heat loss through the total thermal resistance, and obtaining a calculated value of the temperature of the outer surface of the heat insulating layer through the obtained heat loss.

In this embodiment, the establishing an energy control equation according to the energy balance law under the condition of neglecting the pressure and gravity changes in the ground pipeline and the determining the dryness of the steam at the outlet of the steam injection boiler (step S13) includes:

because the change of the pressure and the gravity of the ground pipeline is not considered, the change of the kinetic energy and the potential energy of the saturated steam can be ignored. The following energy control equation is thus established according to the law of energy balance:

due to the fact that

h＝h_gx+h_l(1-x)＝L_vx+h_l

Therefore, it is not only easy to use

qz＝{[x(z)h_g+(1-x(z))h_l]-[x_uh_g+(1-x_u)h_l]}

＝GL_v[x(z)-x_u]

Steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a steam dryness calculation expression of the outlet of the steam injection boiler

In the above formula, q is the heat loss of steam in the ground pipeline per unit length of unit time, and the unit is kilocalories/(hour meter);z is the distance between the calculated position and the boiler outlet in meters; g is saturated steam mass flow, unit kilogram/hour; l is_vPotential heat of vaporization, kcal/kg; x is the number of_uThe dryness of steam at a steam injection wellhead (the tail end of a ground pipeline) is dimensionless.

Wherein, when z is 0, the calculation formula of the dryness of the steam at the outlet of the boiler is as follows:

the above latent heat of vaporization L_vThe difference between the enthalpy of the dry saturated steam and the enthalpy of the saturated water is expressed in kilocalories/kilogram; in the present embodiment, the latent heat of vaporization L_vThe calculation formula of (2) is as follows:

L_v＝273×(374.15-T)^0.38＝h_g-h_l；

h_lthe enthalpy of saturated water is expressed in kilocalories/kilogram, and the calculation formula is as follows:

h_lthe enthalpy of saturated water is expressed in kilocalories/kilogram; the calculation formula is as follows:

h_g＝12500+1.88T-3.7×10^-6T^3.2

in the above formula, T is the steam temperature in degrees celsius.

Referring to fig. 2, which is a step diagram of a method for calculating steam thermodynamic parameters at an outlet of a steam injection boiler according to an embodiment of the present invention, the method for calculating steam thermodynamic parameters in a ground steam injection pipeline according to the present invention includes the following steps:

step S20, obtaining calculation parameters, where the calculation parameters include: and calculating the step length according to the steam pressure, the temperature, the dryness, the steam injection rate, the parameters of the ground pipeline and the environmental parameters outside the ground pipeline of the steam injection wellhead.

In this step, the surface pipeline parameters include: the outer diameter, the inner diameter, the length, the blackness of the outer wall, the heat conductivity coefficient, the thickness of the heat insulation layer and the heat conductivity coefficient of the heat insulation material of the ground pipeline. The environmental parameters outside the surface pipeline comprise: air thermal conductivity, wind speed, air kinematic viscosity, ambient temperature. In addition, the calculating the parameters may further include: and (4) steam discharge of a steam injection wellhead.

Step S22, according to the calculation parameters, the heat loss amount of steam from the outlet of the steam injection boiler to the steam injection wellhead is calculated in an iterative mode;

in the step, firstly, the external surface temperature of a preset heat insulation layer on the pipeline is set; in this embodiment, when setting for predetermine heat insulating layer surface temperature on the pipeline, can set for according to the temperature value of the steam that steam injection well head measured, for example steam injection well head steam's temperature is 300 degrees centigrade, then can set for heat insulating layer surface temperature and be for being less than a certain numerical value of steam injection well head steam temperature, for example can be 200 degrees centigrade to do benefit to and reduce iterative number of times.

Then, the total thermal resistance of the pipeline is calculated according to the temperature of the outer surface of the preset heat insulation layer, referring to fig. 3, the ground pipeline can be an air film layer, a heat insulation layer, a pipe wall, a dirt layer and a liquid film layer from the outside to the inside respectively; wherein the total thermal resistance R of the ground pipeline is calculated according to the following formula:

in the above formula, R is the total thermal resistance of the ground pipeline, R₁Thermal resistance value, R, for convective heat transfer of steam and liquid film layer in ground pipeline₂Thermal resistance, R, for convective heat transfer of steam and dirt layer in ground pipeline₃Thermal resistance, R, for heat conduction of pipe wall₄Thermal resistance, R, for heat conduction of the insulating layer₅The thermal resistance value of the ground pipeline to the forced convection heat transfer of air is expressed in the unit of (meter, hour, centigrade)/kilocalorie; h is_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient of the fouling layer, h_fcThe forced convection heat coefficient on the outer surface of the heat insulation layer is kilocalorie/(square meter, hour and centigrade degrees); lambda [ alpha ]_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iFor ground pipelinesInner radius r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter.

Of course, when the ground pipelines have different structures, the corresponding ground pipeline total thermal resistance value R may also be adaptively changed, which is not described herein again.

In the present embodiment, the forced convection heat transfer of the ground pipeline to the air includes convection heat transfer from the outer surface of the heat insulating layer to the atmosphere and radiation heat transfer from the outer wall of the pipe to the atmosphere; specifically, the method comprises the following steps:

the heat convection coefficient h from the outer surface of the heat insulating layer to the atmosphere_fc', its calculation formula is as follows:

in the above formula, λ_aThe thermal conductivity coefficient of air is expressed in kilocalories/(meter.h.degree centigrade); re is Reynolds number and is calculated by the following formula:

Re＝ν_aD_s/υ_a

in the above formula, v_aWind speed, unit meter/second; upsilon is_aIs the kinematic viscosity of air in square meters per second; d_sThe outer diameter of the heat insulation layer is unit meter; wherein C and n are selected according to Re according to a preset rule.

In the present embodiment, the parameter C, n can be selected according to Re in table 1.

TABLE 1

Re	5-80	80-5×103	5×103-5×104	>5×104
					C	0.81	0.625	0.197	0.023
n	0.40	0.46	0.6	0.8

In this embodiment, the radiant heat transfer coefficient h from the outer wall of the tube to the atmosphere_fc", its calculation formula is as follows:

in the above formula, epsilon is the blackness outside the tube wall, and has no dimension; t is_aIs the average temperature of air in degrees centigrade; t is_wThe temperature of the outer wall of the heat insulation layer is in units of centigrade.

In this embodiment, the radiant heat transfer coefficient h from the outer wall of the tube to the atmosphere can be calculated by presetting the outer surface temperature of the heat insulating layer and using the formula_fc", and then the radiation heat transfer coefficient h is from the outer wall of the tube to the atmosphere_fc"calculate the total thermal resistance R of the surface pipeline.

Then, calculating the on-way heat loss q of the pipeline through the total thermal resistance R of the pipeline; wherein the heat loss q per unit length of the ground pipeline can be calculated by the following calculation formula:

in the above formula, q is the heat loss in the ground pipeline per unit length in unit time, and is expressed in kilocalories/(hr · m); t is_sIs the steam temperature in degrees celsius; t is_aIs ambient temperature, in degrees celsius; r is the total thermal resistance value in unit length of ground pipeline, and the unit is (meter.h.degree centigrade)/kilocalorie.

In the present embodiment, the calculated value of the outer surface temperature of the heat insulating layer is calculated from the calculated on-way heat loss q of the pipe line by using the following calculation formula:

in the above formula, h_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient, lambda, of the fouling layer_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter; q is the heat loss in the ground pipeline per unit length in unit time, in kilocalories/(h.m); t is_sIs the steam temperature in degrees celsius; t is_wThe temperature of the outer wall of the heat insulation layer is in units of centigrade.

And finally, repeatedly iterating, and when the calculated value of the external surface temperature of the heat-insulating layer and the set value meet the first preset precision, determining the external surface temperature of the heat-insulating layer of the pipeline to obtain the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead.

In the present embodiment, the first predetermined accuracy may be set according to actual accuracy requirements, and the smaller the value set by the first predetermined accuracy, the more accurate the obtained heat insulation layer outer surface temperature is, relatively speaking, and accordingly, the higher the accuracy of the obtained heat loss of the pipe line is.

In summary, the process of iterative iteration specifically includes: and obtaining corresponding total thermal resistance by setting the temperature of the outer surface of the heat insulating layer, obtaining corresponding heat loss through the total thermal resistance, and obtaining a calculated value of the temperature of the outer surface of the heat insulating layer through the obtained heat loss.

Step S24, according to the calculation parameters, establishing a control equation of the steam pressure drop gradient in the ground pipeline through a momentum conservation law, and determining the temperature and the pressure of the steam at any position of the ground pipeline;

in this step, to establish a mathematical model of the flow of steam in the surface pipeline, the following assumptions are made:

①, steam parameters (steam injection rate, pressure, temperature and dryness) of the steam injection wellhead are kept unchanged;

②, the flow of the steam in the ground pipeline is a stable flow, under the ideal condition, the steam and the water are uniformly mixed, the flow rate is the same, and the steam-water mixture can be regarded as a uniform fluid.

Based on the assumption that the outlet of the boiler is taken as the origin of coordinates, the flow direction of steam along the pipeline is the Z-axis direction, and a control equation of the steam pressure drop gradient in the ground pipeline is established according to the momentum conservation principle:

according to the control equation, dividing the whole ground pipeline into a plurality of calculation step lengths by using a numerical method, wherein the length of each calculation step length is △ z, and integrating the above formula in each section;

in predicting the pressure distribution along the entire surface pipeline, the entire surface pipeline is numerically divided into segments, each segment being △ z in length, and the above equation is integrated within each segment.

Due to the fact that

Therefore, it is not only easy to use

Order to

v_m＝(v_out+v_in)/2

Then there is

Thus, a calculation formula is obtained for determining the steam pressure at any location of the surface pipeline:

in the above formula, p_inCalculating the steam pressure at the inlet in megapascals for each step of the surface pipeline; p is a radical of_outCalculating the steam pressure at the outlet for each step of the surface pipeline in megapascals; f. of_mIs the coefficient of friction resistance of the wet steam fluid, dimensionless; rho_mDensity of wet steam fluid in kilograms per cubic meter; v is_mIs the average velocity of the wet vapor stream in meters per second; v. of_inCalculating the steam velocity at the inlet of each step of the ground pipeline in meters per second; v. of_outCalculating the steam velocity at the outlet of the step length for each of the ground pipelines in meters per second; g is gravity acceleration in meters per square second; r is_iIs the inner diameter of the gas transmission pipeline in meters; a is the flow cross-sectional area in square meters; g is the mass flow of wet steam fluid in kilograms per second.

The rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

in the above formula f_mIs the coefficient of friction resistance of wet steam, which is determined from the reynolds number Re of saturated wet steam at average pressure and average temperature.

Wherein the coefficient of friction resistance f_mThere are various calculation methods of (1), and the present embodiment is not particularly limited. Specifically, coefficient of frictional resistance f_mThe calculation of (A) can be carried out by the method of Orkiszewski, and the mist flow friction coefficient can be determined by the gas Reynolds number (Re)_gThe relative roughness of the liquid film is calculated by the following specific formula

In the above formula, D is the diameter of the gas transmission pipeline in meters; v. of_sgIs the apparent flow velocity of gas, v_sg＝Q_gA, in meters per second.

Experiments show that the relative roughness of a liquid film in fog flow is 0.001-0.5, and the specific numerical value needs to be according to N_wCalculated using the following formula:

in the above formula, σ is the surface tension of the liquid film at the average temperature and the average pressure, and the unit is newton/m.

When N is present_wWhen the content is less than or equal to 0.005, the following components are adopted:

when N is present_w>At 0.005, there are:

μ_g＝(0.36T+88.37)×10^-4

in the above formula,. mu._gSaturated steam viscosity, mpascal.sec; mu.s_lSaturated distilled water viscosity, mpa · s; t is the steam temperature in degrees Celsius.

In the present embodiment, H_gThe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter.

In this embodiment, the steam in the ground pipeline is saturated wet steam, and the formula for calculating the steam temperature at any position of the ground pipeline is as follows:

T_in＝195.94p_in ^0.225-17.8

in the above formula, T_inCalculating the steam temperature at the inlet of each step of the ground pipeline in units of centigrade; p is a radical of_inFor each meter of surface pipelineThe steam pressure at the inlet of the step is calculated in mpa.

And S26, dividing the pipeline infinitesimal sections on the length of the ground pipeline according to the calculation step length, establishing an energy control equation, and determining the dryness of the steam at the outlet of the steam-injection boiler by iterative calculation of the heat loss, the pressure and the dryness which are coupled with each other by taking the dryness of the steam-injection well as an initial condition.

The loss of heat from the surface pipeline results in a reduction in the saturated steam energy (including potential and internal energy) and thus a reduction in the steam quality, as well as a change in the saturated steam kinetic energy due to changes in the pressure in the pipeline. Thus, according to the law of energy balance, the following energy control equation is established:

steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a calculation expression of the steam dryness at any position of the ground pipeline

Wherein:

C₁＝G(h_g-h_l)

in the above formula, h_gEnthalpy of saturated steam, in kcal/kg; h is_lIs the enthalpy of saturated water, in kcal/kg; x is steam dryness without dimension; g is gravity acceleration in meters per square second; g is steam discharge capacity of a steam injection wellhead, and unit kilogram/hour; q is heat loss per unit length of pipeline in unit time, and unit kilocalorie/(hour meter); rho_mSaturated wet steam density in kilograms per cubic meter; a is the cross-sectional area of the pipeline in square meters; theta is the line inclination angle in degrees.

Wherein, when z is 0, the calculation formula of the dryness of the steam at the outlet of the boiler is as follows:

the rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

H_gthe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter.

Specifically, in step S26, the determining dryness of the steam at the outlet of the steam injection boiler includes the following steps:

s260, setting a preset dryness drop on the micro-element section of the pipeline;

when the dryness drop on the micro element section of the pipeline is set, the dryness drop can be set according to an empirical value, so that the number of iterations is reduced. For example, a range in which the dryness fraction decreases within a predetermined step is obtained statistically, and the dryness fraction decrease may be selected to be a value within the statistically obtained range. Specifically, for example, the dryness drop may be set to 0.015 through a statistical reduction of 0.014 to 0.18 within hundred meters of dryness.

S262, calculating the dryness according to an energy balance law, repeatedly iterating, and determining the dryness drop of the micro element section of the pipeline when the dryness drop calculation value of the micro element section of the pipeline meets a second preset precision with a set value;

the second predetermined precision can be set according to the actual precision requirement, and the smaller the value set by the second predetermined precision is, the more accurately the dryness reduction of the micro element section of the pipeline is obtained relatively.

And S263, circularly calculating to the whole ground pipeline, and determining the dryness of the steam at the outlet of the steam injection boiler.

In the embodiment, the circulation calculation is performed on the whole ground pipeline, specifically, the first pipeline micro-element section at the outlet of the boiler can be sequentially selected towards the wellhead direction, and the circulation calculation is performed until reaching the wellhead.

In summary, the steam thermodynamic parameter at the boiler outlet is calculated as follows:

(1) taking the steam parameter of the wellhead as a calculation starting point (p)_i，x_i，G)；

(2) Taking a length of △ z of the ground line, assuming a drop of △ x dryness in steam over a length of △ z_iAnd pressure drop △ p_iThen the average dryness x of the segment_avi＝x_i-△x _i2 and mean pressure p_avi＝p_i-△p _i2 according to p_aviExamining the corresponding average saturation temperature T_avi(T_avi＝195.94P_avi ^0.225-17.8) and other physical parameters ρ_l、ρ_g、μ_l、μ_g、H_g、H_lCalculating the mean density rho of the saturated wet steam for the following_mAnd coefficient of frictional resistance f_mProvides for the calculation of the pressure drop △ P over the length of △ z from the law of conservation of momentum and the ideal gas law_i'. will calculate △ P_i' AND assumed value △ p_iComparing, and iterating until | △ P_i-△P_i’∣/△P_i<Epsilon to obtain the inlet pressure p of the section_i+1And corresponding saturation temperature T_i+1As an initial value of the next △ z, the saturation temperature T is calculated at the same time_i+1Saturation pressure p_i+1Lower enthalpy value h_li+1、h_gi+1And preparing for calculating the steam dryness of the section.

(3) Assuming surface pipeline outside surface temperature T_wiCalculating h by using a formula_r、h_cThereby calculating the total thermal resistance and heat loss q_iThen heat loss q is added_iSubstituting the heat transfer calculation formula from the inside of the pipeline to the outer wall of the heat insulation layer to obtain the temperature T of the outer surface of the pipeline_wi', iterating until | T_wi-T_wi’∣/T_wi<Until epsilon, finally finding the heat loss q_i。

(4) Calculating dryness x of steam from energy balance equation_iAnd iterating until | x_i+1-(x_i-△x_i)∣/(x_i-△x_i)<E, otherwise, repeating the calculation steps of (2) to (4) and calculating the dryness x_i+1As the initial dryness value for the next △ z.

(5) Taking off a next △ z, repeating the calculation steps (2) to (5) until the whole ground pipeline is calculated, and obtaining the arbitrary position p of the pipeline_i、T_i、x_i、q_i(i-0, 1, …, N), including the steam parameters at the boiler outlet.

According to the technical scheme, the steam thermodynamic parameter calculation method for the steam injection boiler outlet in the embodiment includes the steps of obtaining steam pressure, temperature and dryness of the steam injection wellhead, carrying out numerical analysis on the steam pressure in the ground pipeline, establishing a pressure equation of the steam along the ground pipeline, and determining the pressure of the steam at any point along the ground pipeline, so that the steam thermodynamic parameter of the steam injection boiler outlet is determined, and a reliable basis is provided for boiler steam injection parameter design.

Furthermore, because the calculation of the heat loss and the dryness fraction is based on a function of temperature, the calculation device of the steam thermal parameters at the outlet of the steam injection boiler relies on the obtained accurate temperature, an energy control equation is established according to an energy balance law, and the heat loss and the dryness fraction of the steam at the outlet of the steam injection boiler on a ground pipeline are solved through circulating calculation, so that the heat loss and the dryness fraction of the steam at the outlet of the steam injection boiler obtained by the method are high in precision.

Referring to fig. 4, a device for calculating a steam thermodynamic parameter in a ground steam injection pipeline includes:

a parameter obtaining module 20, configured to obtain calculation parameters, where the calculation parameters include: steam pressure, temperature and dryness of a steam injection wellhead, parameters of a ground pipeline and environmental parameters outside the ground pipeline;

the heat loss determining module 22 is used for iteratively calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

and the dryness determining module 24 is used for establishing an energy control equation according to the energy balance law under the condition of neglecting the pressure and gravity change in the ground pipeline and determining the dryness of the steam at the outlet of the steam injection boiler.

Referring to fig. 5, a device for calculating a steam thermodynamic parameter in a ground steam injection pipeline includes:

a parameter obtaining module 20, configured to obtain calculation parameters, where the calculation parameters include: calculating the step length according to the steam pressure, the temperature, the dryness, the steam injection rate, the parameters of the ground pipeline and the environmental parameters outside the ground pipeline of the steam injection wellhead;

the heat loss determining module 22 is used for iteratively calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

the pressure and temperature determining module 24 is used for establishing a control equation of the steam pressure drop gradient in the ground pipeline according to the calculation parameters and the momentum conservation law, and determining the temperature and the pressure of the steam at any position of the ground pipeline;

and the dryness determining module 26 is used for dividing the pipeline infinitesimal section on the length of the ground pipeline according to the calculation step length, establishing an energy control equation, and determining the dryness of the steam at the outlet of the steam injection boiler by using the dryness of the steam injection well as an initial condition and through the iterative calculation of the heat loss, the pressure and the dryness which are coupled with each other.

According to the technical scheme, the device for calculating the steam thermodynamic parameter at the outlet of the steam injection boiler in the embodiment carries out numerical analysis on the steam pressure in the ground pipeline by acquiring the steam pressure, the temperature and the dryness of the steam injection wellhead, establishes a pressure equation of the steam along the ground pipeline, and determines the pressure of the steam at any point along the ground pipeline, so that the steam thermodynamic parameter at the outlet of the steam injection boiler is determined, and a reliable basis is provided for the design of the steam injection parameter of the boiler.

Furthermore, because the calculation of the heat loss and the dryness fraction is based on a function of temperature, the calculation device of the steam thermal parameters at the outlet of the steam injection boiler relies on the obtained accurate temperature, an energy control equation is established according to an energy balance law, and the heat loss and the dryness fraction of the steam at the outlet of the steam injection boiler on a ground pipeline are solved through circulating calculation, so that the heat loss and the dryness fraction of the steam at the outlet of the steam injection boiler obtained by the method are high in precision.

Any numerical value recited herein includes all values from the lower value to the upper value that are incremented by one unit, provided that there is a separation of at least two units between any lower value and any higher value. For example, if it is stated that the number of a component or a value of a process variable (e.g., temperature, pressure, time, etc.) is from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, it is intended that equivalents such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also expressly enumerated in this specification. For values less than 1, one unit is suitably considered to be 0.0001, 0.001, 0.01, 0.1. These are only examples of what is intended to be explicitly recited, and all possible combinations of numerical values between the lowest value and the highest value that are explicitly recited in the specification in a similar manner are to be considered.

Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. The use of "about" or "approximately" with a range applies to both endpoints of the range. Thus, "about 20 to about 30" is intended to cover "about 20 to about 30", including at least the endpoints specified.

All articles and references disclosed, including patent applications and publications, are hereby incorporated by reference for all purposes. The term "consisting essentially of …" describing a combination shall include the identified element, ingredient, component or step as well as other elements, ingredients, components or steps that do not materially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, or steps herein also contemplates embodiments that consist essentially of such elements, components, or steps. By using the term "may" herein, it is intended to indicate that any of the described attributes that "may" include are optional.

A plurality of elements, components, parts or steps can be provided by a single integrated element, component, part or step. Alternatively, a single integrated element, component, part or step may be divided into separate plural elements, components, parts or steps. The disclosure of "a" or "an" to describe an element, ingredient, component or step is not intended to foreclose other elements, ingredients, components or steps.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and many applications other than the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the present teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are hereby incorporated by reference for all purposes. The omission in the foregoing claims of any aspect of subject matter that is disclosed herein is not intended to forego such subject matter, nor should the inventors be construed as having contemplated such subject matter as being part of the disclosed subject matter.

Claims (4)

1. A method for calculating steam thermodynamic parameters of an outlet of a steam injection boiler is characterized by comprising the following steps:

obtaining calculation parameters, wherein the calculation parameters comprise: steam pressure, temperature and dryness of a steam injection wellhead, parameters of a ground pipeline and environmental parameters outside the ground pipeline;

according to the calculation parameters, iteratively calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead;

establishing an energy control equation according to an energy balance law under the conditions of neglecting the pressure and gravity change in the ground pipeline, and determining the dryness of steam at the outlet of the ground pipeline steam injection boiler;

the calculating of the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead comprises the following steps:

setting the outer surface temperature of a preset heat insulation layer on the pipeline;

calculating the total thermal resistance of the pipeline according to the temperature of the outer surface of the preset heat insulation layer, and calculating the heat loss of the pipeline gas transmission along the way according to the total thermal resistance of the pipeline; calculating the temperature of the outer surface of the heat insulation layer according to the heat loss of the pipeline gas transmission along the way;

repeatedly iterating, and when the calculated value of the external surface temperature of the heat-insulating layer and the set value meet first preset precision, determining the external surface temperature of the heat-insulating layer of the pipeline to obtain the heat loss of steam from the outlet of the steam injection boiler to the steam injection well head;

calculating the heat loss per unit length of the ground pipeline by using the following calculation formula:

in the above formula, q is the heat loss in the ground pipeline of unit length in unit time, and the unit is kilocalorie/(hour meter); t is_sIs the steam temperature in degrees celsius; t is_aIs ambient temperature, in degrees celsius; r is the total thermal resistance value in the ground pipeline with unit length, and the unit is (meter.h.centigrade)/kilocalorie;

the calculating the total thermal resistance of the surface pipeline comprises the following steps:

the total thermal resistance R of the surface pipeline is calculated according to the following formula:

in the above formula, R is the total thermal resistance of the ground pipeline, R₁Thermal resistance value, R, for convective heat transfer of steam and liquid film layer in ground pipeline₂Thermal resistance, R, for convective heat transfer of steam and dirt layer in ground pipeline₃Thermal resistance, R, for heat conduction of pipe wall₄Thermal resistance, R, for heat conduction of the insulating layer₅The thermal resistance value of the ground pipeline to the forced convection heat transfer of air is expressed in the unit of (meter, hour, centigrade)/kilocalorie; h is_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient of the fouling layer, h_fcThe forced convection heat coefficient on the outer surface of the heat insulation layer is kilocalorie/(square meter, hour and centigrade degrees); lambda [ alpha ]_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter;

the forced convection heat exchange of the ground pipeline to the air comprises convection heat exchange from the outer surface of the heat insulating layer to the atmosphere and radiation heat exchange from the outer wall of the pipeline to the atmosphere;

the heat convection coefficient h from the outer surface of the heat insulating layer to the atmosphere_fc', its calculation formula is as follows:

in the above formula, λ_aThe thermal conductivity coefficient of air is expressed in kilocalories/(meter.h.degree centigrade); re is Reynolds number and is calculated by the following formula:

Re＝ν_aD_s/υ_a

in the above formula, v_aWind speed, unit meter/second; upsilon is_aIs the kinematic viscosity of air in square meters per second; d_sThe outer diameter of the heat insulation layer is unit meter; wherein C, n are selected according to Re according to a predetermined ruleTaking;

radiant heat transfer coefficient h from the outer wall of the tube to the atmosphere_fc", its calculation formula is as follows:

in the above formula, epsilon is the blackness outside the tube wall, and has no dimension; t is_aIs the average temperature of air in degrees centigrade; t is_wThe temperature of the outer wall of the heat insulation layer is measured in centigrade degrees;

calculating the temperature of the outer surface of the heat insulating layer by adopting the following calculation formula:

in the above formula, h_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient, lambda, of the fouling layer_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter; q is the heat loss in the ground pipeline per unit length in unit time, in kilocalories/(h.m); t is_sIs the steam temperature in degrees celsius; t is_wThe temperature of the outer wall of the heat insulation layer is measured in centigrade degrees;

the step of calculating the dryness fraction according to the law of energy balance comprises the following steps:

the following energy control equation is established:

steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a steam dryness calculation expression of the outlet of the steam injection boiler

Thus, the steam quality at the outlet of the boiler is calculated by the formula:

in the above formula, q is the heat loss of steam in the ground pipeline per unit length of unit time, and the unit is kilocalories/(hour meter); z is the distance between the calculated position and the boiler outlet in meters; g is saturated steam mass flow, unit kilogram/hour; l is_vPotential heat of vaporization, kcal/kg; x is the number of_uThe steam dryness is the steam dryness of a steam injection wellhead (the tail end of a ground pipeline) and is dimensionless;

the above latent heat of vaporization L_vThe difference between the enthalpy of the dry saturated steam and the enthalpy of the saturated water is calculated by the following formula:

L_v＝273×(374.15-T)^0.38＝h_g-h_l；

h_lthe enthalpy of saturated water is calculated by the following formula in kcal/kg:

h_lthe enthalpy of saturated water is expressed in kilocalories/kilogram; the calculation formula is as follows:

h_g＝12500+1.88T-3.7×10^-6T^3.2

in the above formula, T is the steam temperature in degrees celsius.

2. A method for calculating steam thermodynamic parameters of an outlet of a steam injection boiler is characterized by comprising the following steps:

obtaining calculation parameters, wherein the calculation parameters comprise: calculating the step length according to the steam pressure, the temperature, the dryness, the steam injection rate, the parameters of the ground pipeline and the environmental parameters outside the ground pipeline of the steam injection wellhead;

calculating the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

according to the calculation parameters, establishing a control equation of the steam pressure drop gradient in the ground pipeline through a momentum conservation law, and determining the temperature and the pressure of the steam at any position of the ground pipeline;

dividing a pipeline infinitesimal section on the length of the ground pipeline according to the calculation step length, establishing an energy control equation, and determining the dryness of steam at the outlet of the steam-injection boiler by iterative calculation of mutually coupled heat loss, pressure and dryness by taking the dryness of the steam-injection well as an initial condition;

taking a boiler outlet as a coordinate origin, taking the steam flowing direction along a pipeline as a Z-axis direction, and establishing a control equation of steam pressure drop gradient in the ground pipeline according to a momentum conservation principle:

according to the control equation, dividing the whole ground pipeline into a plurality of calculation step lengths by using a numerical method, wherein the length of each calculation step length is △ z, and integrating the above formula in each section;

order to

v_m＝(v_out+v_in)/2

Obtaining a calculation formula for determining the steam pressure at any position of the surface pipeline:

in the above formula, p_inCalculating the steam pressure at the inlet in megapascals for each step of the surface pipeline; p is a radical of_outCalculating the steam pressure at the outlet for each step of the surface pipeline in megapascals; f. of_mIs the coefficient of friction resistance of the wet steam fluid, dimensionless; rho_mDensity of wet steam fluid in kilograms per cubic meter; v is_mIs the average velocity of the wet vapor stream in meters per second; v. of_inCalculating the steam velocity at the inlet of each step of the ground pipeline in meters per second; v. of_outCalculating the steam velocity at the outlet of the step length for each of the ground pipelines in meters per second; g is the acceleration of gravity in unitsMeters per square second; r is_iIs the inner diameter of the gas transmission pipeline in meters; a is the flow cross-sectional area in square meters; g is the mass flow of the wet steam fluid, and the unit is kilogram/second;

the rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

in the above formula f_mIs the coefficient of friction resistance of the wet steam, which is determined from the reynolds number Re of the saturated wet steam at the average pressure and the average temperature;

H_gthe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter;

the steam in the ground pipeline is saturated wet steam, and the formula for calculating the steam temperature at any position of the ground pipeline is as follows:

T_in＝195.94p_in ^0.225-17.8

in the above formula, T_inCalculating the steam temperature at the inlet of each step of the ground pipeline in units of centigrade; p is a radical of_inAt the inlet of each calculation step for the surface pipelineSteam pressure, in mpa;

the method for determining the dryness of the steam at the outlet of the steam injection boiler comprises the following steps:

setting a preset dryness drop on the micro section of the pipeline;

calculating the dryness according to an energy balance law, repeatedly iterating, and determining the dryness drop of the micro element section of the pipeline when the dryness drop calculation value of the micro element section of the pipeline meets a second preset precision with a set value;

circularly calculating to the whole ground pipeline, and determining the dryness of the steam at the outlet of the steam injection boiler;

the step of calculating the dryness fraction according to the law of energy balance comprises the following steps:

the following energy control equation is established:

steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a calculation expression of the steam dryness at any position of the ground pipeline

Wherein:

C₁＝G(h_g-h_l)

thus, the boiler outlet steam dryness calculation formula is:

in the above formula，h_gEnthalpy of saturated steam, in kcal/kg; h is_lIs the enthalpy of saturated water, in kcal/kg; x is steam dryness without dimension; g is gravity acceleration in meters per square second; g is steam discharge capacity of a steam injection wellhead, and unit kilogram/hour; q is heat loss per unit length of pipeline in unit time, and unit kilocalorie/(hour meter); rho_mSaturated wet steam density in kilograms per cubic meter; a is the cross-sectional area of the pipeline in square meters; theta is the inclination angle of the pipeline and unit degree;

the rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

H_gthe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter.

3. A steam thermodynamic parameter calculation device in a ground steam injection pipeline is characterized by comprising:

a parameter obtaining module, configured to obtain calculation parameters, where the calculation parameters include: steam pressure, temperature and dryness of a steam injection wellhead, parameters of a ground pipeline and environmental parameters outside the ground pipeline;

the heat loss determining module is used for iteratively calculating the heat loss amount of steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

the dryness determining module is used for establishing an energy control equation according to an energy balance law under the condition of neglecting pressure and gravity change in a ground pipeline and determining the dryness of steam at the outlet of the steam injection boiler;

the calculating of the heat loss amount of the steam from the outlet of the steam injection boiler to the steam injection wellhead comprises the following steps:

setting the outer surface temperature of a preset heat insulation layer on the pipeline;

calculating the total thermal resistance of the pipeline according to the temperature of the outer surface of the preset heat insulation layer, and calculating the heat loss of the pipeline gas transmission along the way according to the total thermal resistance of the pipeline; calculating the temperature of the outer surface of the heat insulation layer according to the heat loss of the pipeline gas transmission along the way;

repeatedly iterating, and when the calculated value of the external surface temperature of the heat-insulating layer and the set value meet first preset precision, determining the external surface temperature of the heat-insulating layer of the pipeline to obtain the heat loss of steam from the outlet of the steam injection boiler to the steam injection well head;

calculating the heat loss per unit length of the ground pipeline by using the following calculation formula:

in the above formula, q is the heat loss in the ground pipeline per unit length in unit time, and is expressed in kilocalories/(hr · m); t is_sIs the steam temperature in degrees celsius; t is_aIs ambient temperature, in degrees celsius; r is the total thermal resistance value in the ground pipeline with unit length, and the unit is (meter.h.centigrade)/kilocalorie;

the calculating the total thermal resistance of the surface pipeline comprises the following steps:

the total thermal resistance R of the surface pipeline is calculated according to the following formula:

in the above formula, R is the total thermal resistance of the ground pipeline, R₁Thermal resistance value, R, for convective heat transfer of steam and liquid film layer in ground pipeline₂Thermal resistance, R, for convective heat transfer of steam and dirt layer in ground pipeline₃Thermal resistance, R, for heat conduction of pipe wall₄Thermal resistance, R, for heat conduction of the insulating layer₅The thermal resistance value of the ground pipeline to the forced convection heat transfer of air is expressed in the unit of (meter, hour, centigrade)/kilocalorie; h is_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient of the fouling layer, h_fcThe forced convection heat coefficient on the outer surface of the heat insulation layer is kilocalorie/(square meter, hour and centigrade degrees); lambda [ alpha ]_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter;

the forced convection heat exchange of the ground pipeline to the air comprises convection heat exchange from the outer surface of the heat insulating layer to the atmosphere and radiation heat exchange from the outer wall of the pipeline to the atmosphere;

the heat convection coefficient h from the outer surface of the heat insulating layer to the atmosphere_fc', its calculation formula is as follows:

in the above formula, λ_aThe thermal conductivity coefficient of air is expressed in kilocalories/(meter.h.degree centigrade); re is Reynolds number and is calculated by the following formula:

Re＝ν_aD_s/υ_a

in the above formula, v_aWind speed, unit meter/second; upsilon is_aIs the kinematic viscosity of air in square meters per second; d_sThe outer diameter of the heat insulation layer is unit meter; wherein C and n are selected according to Re according to a preset rule;

radiant heat transfer coefficient h from the outer wall of the tube to the atmosphere_fc", its calculation formula is as follows:

in the above formula, epsilon is the blackness outside the tube wall, and has no dimension; t is_aIs the average temperature of air in degrees centigrade; t is_wThe temperature of the outer wall of the heat insulation layer is measured in centigrade degrees;

calculating the temperature of the outer surface of the heat insulating layer by adopting the following calculation formula:

in the above formula, h_fIs the convective heat transfer coefficient of the liquid film layer, h_pIs the convective heat transfer coefficient, lambda, of the fouling layer_pThe coefficient of thermal conductivity of the ground pipeline is kilocalorie/(meter.h.degree centigrade); r is_iIs the inner radius of the ground pipeline, r_oIs the outer radius of the surface pipeline, r_insThe outer radius of the heat insulation layer is meter; q is the heat loss in the ground pipeline per unit length in unit time, in kilocalories/(h.m); t is_sIs the steam temperature in degrees celsius; t is_wThe temperature of the outer wall of the heat insulation layer is measured in centigrade degrees;

the step of calculating the dryness fraction according to the law of energy balance comprises the following steps:

the following energy control equation is established:

steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a steam dryness calculation expression of the outlet of the steam injection boiler

Thus, the steam quality at the outlet of the boiler is calculated by the formula:

in the above formula, q is the heat loss of steam in the ground pipeline per unit length of unit time, and the unit is kilocalories/(hour meter); z is the distance between the calculated position and the boiler outlet in meters; g is saturated steam mass flow, unit kilogram/hour; l is_vPotential heat of vaporization, kcal/kg; x is the number of_uThe steam dryness is the steam dryness of a steam injection wellhead (the tail end of a ground pipeline) and is dimensionless;

the above latent heat of vaporization L_vThe difference between the enthalpy of the dry saturated steam and the enthalpy of the saturated water is calculated by the following formula:

L_v＝273×(374.15-T)^0.38＝h_g-h_l；

h_lthe enthalpy of saturated water is calculated by the following formula in kcal/kg:

h_lthe enthalpy of saturated water is expressed in kilocalories/kilogram; the calculation formula is as follows:

h_g＝12500+1.88T-3.7×10^-6T^3.2

in the above formula, T is the steam temperature in degrees celsius.

4. A steam thermodynamic parameter calculation device in a ground steam injection pipeline is characterized by comprising:

a parameter obtaining module, configured to obtain calculation parameters, where the calculation parameters include: calculating the step length according to the steam pressure, the temperature, the dryness, the steam injection rate, the parameters of the ground pipeline and the environmental parameters outside the ground pipeline of the steam injection wellhead;

the heat loss determining module is used for iteratively calculating the heat loss amount of steam from the outlet of the steam injection boiler to the steam injection wellhead according to the calculation parameters;

the pressure and temperature determination module is used for establishing a control equation of the steam pressure drop gradient in the ground pipeline according to the calculation parameters and the momentum conservation law, and determining the temperature and the pressure of the steam at any position of the ground pipeline;

the dryness determining module is used for dividing a pipeline infinitesimal section on the length of the ground pipeline according to the calculation step length, establishing an energy control equation, and determining the dryness of the steam at the outlet of the steam injection boiler by using the dryness of the steam injection well as an initial condition and through the iterative calculation of the heat loss, the pressure and the dryness which are coupled with each other;

taking a boiler outlet as a coordinate origin, taking the steam flowing direction along a pipeline as a Z-axis direction, and establishing a control equation of steam pressure drop gradient in the ground pipeline according to a momentum conservation principle:

according to the control equation, dividing the whole ground pipeline into a plurality of calculation step lengths by using a numerical method, wherein the length of each calculation step length is △ z, and integrating the above formula in each section;

order to

v_m＝(v_out+v_in)/2

Obtaining a calculation formula for determining the steam pressure at any position of the surface pipeline:

in the above formula, p_inCalculating the steam pressure at the inlet in megapascals for each step of the surface pipeline; p is a radical of_outCalculating the steam pressure at the outlet for each step of the surface pipeline in megapascals; f. of_mIs the coefficient of friction resistance of the wet steam fluid, dimensionless; rho_mDensity of wet steam fluid in kilograms per cubic meter; v is_mIs the average velocity of the wet vapor stream in meters per second; v. of_inCalculating the steam velocity at the inlet of each step of the ground pipeline in meters per second; v. of_outCalculating the steam velocity at the outlet of the step length for each of the ground pipelines in meters per second; g is gravity acceleration in meters per square second; r is_iIs the inner diameter of the gas transmission pipeline in meters; a is the flow cross-sectional area in square meters; g is the mass flow of the wet steam fluid, and the unit is kilogram/second;

the rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

in the above formula f_mIs the coefficient of friction resistance of the wet steam, which is determined from the reynolds number Re of the saturated wet steam at the average pressure and the average temperature;

H_gthe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter;

the steam in the ground pipeline is saturated wet steam, and the formula for calculating the steam temperature at any position of the ground pipeline is as follows:

T_in＝195.94p_in ^0.225-17.8

in the above formula, T_inCalculating the steam temperature at the inlet of each step of the ground pipeline in units of centigrade; p is a radical of_inCalculating steam pressure at inlet of step size for each of surface pipelinesA bit megapascals;

the method for determining the dryness of the steam at the outlet of the steam injection boiler comprises the following steps:

setting a preset dryness drop on the micro section of the pipeline;

calculating the dryness according to an energy balance law, repeatedly iterating, and determining the dryness drop of the micro element section of the pipeline when the dryness drop calculation value of the micro element section of the pipeline meets a second preset precision with a set value;

circularly calculating to the whole ground pipeline, and determining the dryness of the steam at the outlet of the steam injection boiler;

the step of calculating the dryness fraction according to the law of energy balance comprises the following steps:

the following energy control equation is established:

steam dryness x of steam injection well_z＝L＝x_uAs an initial condition, solving the equation to obtain a calculation expression of the steam dryness at any position of the ground pipeline

Wherein:

C₁＝G(h_g-h_l)

thus, the boiler outlet steam dryness calculation formula is:

in the above formula, h_gEnthalpy of saturated steam, in kcal/kg; h is_lIs the enthalpy of saturated water, in kcal/kg; x is steam dryness without dimension; g is gravity acceleration in meters per square second; g is steam discharge capacity of a steam injection wellhead, and unit kilogram/hour; q is heat loss per unit length of pipeline in unit time, and unit kilocalorie/(hour meter); rho_mSaturated wet steam density in kilograms per cubic meter; a is the cross-sectional area of the pipeline in square meters; theta is the inclination angle of the pipeline and unit degree;

the rho_mThe average density of saturated wet steam is calculated as follows:

ρ_m＝H_gρ_g+(1-H_g)ρ_l

in the above formula rho_lThe density of saturated water is related to the steam temperature T as follows:

ρ_l＝0.9967-4.615×10^-5T-3.063×10^-6T²

in the above formula rho_gThe calculation formula for the density of saturated steam is as follows:

ρ_g＝5.9×10^-4+3.2×10^-4(T/100)^4.5

in the above formula, T is the steam temperature in centigrade; p is steam pressure in mpa;

H_gthe volume vapor content of the saturated vapor is calculated according to the following formula:

in the above formula, x is steam dryness without dimensional quantity; rho_gIs the density of saturated steam, in kilograms per cubic meter; rho_lIs the density of saturated water in kilograms per cubic meter.

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