CN107274473A - Three-dimensional numerical model for heat transfer of vertical buried pipe of ground source heat pump and establishment method thereof - Google Patents
Three-dimensional numerical model for heat transfer of vertical buried pipe of ground source heat pump and establishment method thereof Download PDFInfo
- Publication number
- CN107274473A CN107274473A CN201710598336.6A CN201710598336A CN107274473A CN 107274473 A CN107274473 A CN 107274473A CN 201710598336 A CN201710598336 A CN 201710598336A CN 107274473 A CN107274473 A CN 107274473A
- Authority
- CN
- China
- Prior art keywords
- heat
- temperature
- computing unit
- unit
- heat transfer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T15/00—3D [Three Dimensional] image rendering
- G06T15/005—General purpose rendering architectures
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Evolutionary Computation (AREA)
- Geometry (AREA)
- General Engineering & Computer Science (AREA)
- Computer Graphics (AREA)
- Road Paving Structures (AREA)
Abstract
The invention relates to a heat transfer numerical model of a vertical buried pipe of a ground source heat pump and an establishment method thereof, wherein the heat transfer numerical model is a three-dimensional numerical heat transfer model and is divided into two structural levels: horizontal structures and vertical structures. The invention can carry out numerical simulation on the field thermal response test under the constant heat flow working condition and the constant temperature working condition, calculate the thermal physical property parameter of the rock-soil body and the heat exchange capability of the vertical buried pipe, and is convenient for design and application; the properly simplified heat transfer model can keep higher calculation precision, simultaneously occupies relatively less calculation hardware resources, can accelerate the calculation speed and is suitable for the group hole long-term heat transfer calculation; the invention can input the heat exchange fluid with variable flow rate parameters when simulating long-term load loading, obtains the heat exchange capacity corresponding to different flow rates, and is suitable for the optimization value research of the parameters of the frequency modulation water pump in engineering design.
Description
Technical field
The present invention relates to technical field of ground source heat pump, and in particular to a kind of vertical ground heat exchanger heat transfer number of earth source heat pump
Be worth method for establishing model, it is adaptable to the Rock And Soil thermal physical property parameter of the live geo-thermal response tests of various different operating modes calculate with it is vertical
Ground heat exchanger is designed.
Background technology
Geothermal heat pump air-conditioning system is changed using flowing of the circulation fluid in underground pipe to realize with underground ground heat storage
Heat.Underground Rock And Soil relative atmospheric temperature is more stablized, and heat accumulation is stronger with heat-transfer capability, earth-source hot-pump system is had efficient section
Can, it is economic and environment-friendly the characteristics of.Ground source perpendicularly buried pipe mode obtains wider due to taking the characteristics of surface area is less with relative
General application.In earth-source hot-pump system engineering-built, the design of vertical ground heat exchanger is key component, and is rationally designed
The premise of ground heat exchanger is the exchange capability of heat of accurate measurement underground Rock And Soil.China《Earth-source hot-pump system engineering technology is advised
Model《GB50366-2005》(version in 2009) has increased ground thermal response test portion content newly, specify that the rock of earth-source hot-pump system
Related request is tested in native thermal response, recommends " constant heat flow method " as experiment implementation.
The method for the on-the-spot test commonly used in current engineering has two kinds：Constant heat flux method and constant inflow temperature method.It is constant
Heat flux measurement method enters return water temperature by apply each moment underground pipe during constant power, collecting test to Rock And Soil.
Utilize the line source model or the synthesis thermal physical property parameter of post heat source model Inversion Calculation Rock And Soil of constant heat flow.Ask for parametric procedure
Simplicity, but constant heat flux method is slightly not enough in terms of heat exchanging capability of buried tube test, it is difficult to obtain unit linear meter(lin.m.) heat exchange amount；In perseverance
Determine during heat flux measurement, the loading power of constant heat flux is set at random, it is impossible to reflect practically source operation of heat pump completely
State；When asking for thermal physical property parameter in addition, due to no use flow parameter and pipe diameter parameter, to the mass flow of fluid
The exchange capability of heat change produced with change in flow can not reflect accurate.Constant inflow temperature geo-thermal response test method is by control
The inflow temperature and water flow of underground pipe are constant, and the load for cooling down or heating is applied to Rock And Soil.In test process locality
Pipe laying Outlet Temperatures, can intuitively obtain close stable heat exchange amount during certain time.Because test process loads heat
Stream is non-constant, and acquisition ground thermal property parameter is more complicated, and various method for solving still disunity at present, it is difficult to according in specification
Computational methods design underground pipe total amount.
Constant heat flux method and constant inflow temperature method emphasize particularly on different fields feature, have wide application with grinding in engineering
Study carefully.The patent No. CN200810201626, CN200810238160, CN201110223663 carry out model to constant heat flow method of testing
Amendment, improves the precision for asking for thermal physical property parameter, but still undefined loading power and influence of the rate-of flow to test result.
Patent No. CN201110224680 is by the carry out test of many times to different loading loads, velocity of medium, to obtain Different Results,
Multiplicity is carried out, the exchange capability of heat of test underground pipe heat exchanging holes is fully understanded.But the testing time is longer, test is equal every time
Rock And Soil temperature change when being tested by last time is influenceed.Patent No. CN201120152222 is directed to the heat transfer of ground heat exchanger
Complexity solves a kind of non-linear, hole group's entire thermal resistance method of testing of Design-Oriented parameter application of proposition with heat transfer, simplifies rock
The linking step that native thermal physical property parameter is applied to design, but this method still uses substantially linear heat source model, it is impossible to recognize in hole
The difference of the transient of heat transfer and vertical different depth heat compensator conducting property.Patent No. CN201210026702,
CN201210207869, CN201210414520, CN201410479673 are by setting up monitoring holes and the layering of instrument connection side
The method of test processes, using the temperature sensor at diverse location, obtains the temperature change of different depth, can recognize difference
The Rock And Soil heat compensator conducting property difference of depth.Weak point is difficult to control for the hole deviation angle of monitoring holes and instrument connection, with depth
Increase the range error increase of the two, influence data precision；In the case of the loading power invariability of whole instrument connection, different depth
The loading power of each layer is constant not on the testing time.The loading power of each layer is considered as perseverance in the testing time in these models
It is fixed, error is further increased.Patent No. CN201510181300 sets up a kind of single hole and the Numerical Heat Transfer computation model in group hole,
Single instrument connection can be not only calculated, the biography of ground-coupled heat exchanger hole group by simulant building load change with time, can also be calculated
Thermal response.This method is considered as stable state using backwater mean temperature concept is entered to the heat transfer in drilling, ignores vertical conversion and week
To temperature change, simplified group hole boundary condition can also produce certain error.
The instability that load is loaded due to it in the test and engineer applied of ground heat exchanger and heat transfer unstable state
Change, by when numerical simulation be closest to actual Heat Transfer Calculation.As theoretical research, some business softwares can accomplish ground
The numerical value hourly simulation of lower heat exchanger, calculating can be also simulated to pipeline enclosure away from key element in, the hole such as backfilling material, velocity of medium.But
As engineer applied, then excessively complicated, cost is higher, it is long to calculate the time, lacks certain applications parameter, such as geothermal gradient, layering ginseng
Number, heat exchange pipeline form etc..
The content of the invention
In order to integrate the data processing method of two kinds of measurement conditions, rock can be asked for after any working condition measurement is chosen
Native thermal physical property parameter and exchange capability of heat, using same computational methods, are easy to two kinds of operating modes to be compared；Underground pipe heat exchange is provided
Long-term hourly simulation, obtain accurate temperature-responsive data.The present invention provides a kind of appropriate simplification but the complete numerical value of parameter
Model, the numerical model as ground buried pipe of ground source heat pump heat exchanger special unsteady-state heat transfer calculating instrument, it is desirable to calculation process
Clearly, various working is inputted, and single hole, group hole are applicable.
The technical scheme that the present invention is used by solution its technical problem for：Earth source heat pump three dimensions of vertical underground pipe heat transfer
It is worth model, discrete equation is set up to the computing unit applied energy conservation principle in model, each computing unit has fixed heat
Hold, connected between computing unit with corresponding thermal resistance.Model is divided to two layer of structure：Horizontal structure and vertical stratification；Horizontal junction
Structure partial simulation calculates the heat transfer of the unit radial and circumferencial direction centered on underground pipe, and vertical stratification partial simulation calculates ground
The axial temperature change of pipe laying internal flow；
Level calculation unit is the Circle Structure that decomposes, and 2 or 4 heat exchanger tubes keep constant spacings, every pipe periphery
Computing unit radially, Level Expand；
On horizontal structure, basic calculating formula is as follows：
The heat that each computing unit unit temperature change needs：
QV=V0*ρc*K
QV--- the volumetric heat capacity amount of computing unit；
V0--- the volume of computing unit；
The volumetric heat capacity of ρ c --- computing unit；
K --- border coefficient, in the approximate simulation poroid state of group, exchanges heat pitch of holes as reference, horizontal model using underground pipe
The relative ratio with original equivalent volume reduction of outside ring layer, span：0 ＜ K≤1；
Thermal resistance of each computing unit in different directions：
(radial direction)
(approximate processing of circumferencial direction and irregular unit)
λS=λ0+a*T
Ri--- the thermal resistance of the unit adjacent with calculating grid cell；
R0--- the thermal resistance of computing unit；
M --- radial number of partitions, when ring layer unit is beyond heat exchanger tube 1-1.5m, M=1；
λS--- the thermal conductivity of Rock And Soil stratum or pipeline at a certain temperature；
d0--- the external diameter of the circle where computing unit segmental arc；
di--- the internal diameter of the circle where computing unit segmental arc；
L --- computing unit length or segmental arc length；
S --- computing unit sectional area；
λ0--- the thermal conductivity of Rock And Soil stratum or pipeline under fiducial temperature；
The thermal conductivity variation coefficient of a --- Rock And Soil stratum or pipeline at different temperatures；
The grid cell temperature at T --- certain moment；
R0Computational methods and RiIt is identical；
Pipeline heat convection thermal resistance RfControlled by internal diameter of the pipeline, flow velocity, fluid temperature (F.T.) and fluid parameter, use empirical equation
Fitting is obtained, and calculates the R that is added to when needingiAmong；
In a time step, the temperature-responsive of all grid cells is calculated one by one, is then transferred to next time step
Long assignment again is calculated：
T ＇ --- the grid cell temperature that need to be calculated during next step-length；
Ti--- temperature of the unit adjacent with calculating grid cell at certain moment；
JS--- the time of each material calculation；
N --- the quantity of the unit adjacent with calculating grid cell；
On vertical stratification, basic calculation is as follows：
Vertical stratification part, is divided into multigroup superimposed structure by horizontal grid structure, to representing different depth Rock And Soil
Layer, heat exchange tube fluid is continuously moved in practice, and using Differential Principle, fluid is cut into a series of long column shape bodies,
Continuous flowing is considered as stroboscopic motion, in each material calculation, by the interrupted passage of each step, temperature is passed in simulation pipe
Pass state, the pushing distance of each step of tube fluid is related to flow velocity, caliber, with hierarchical mode vertical length it is inconsistent, it is necessary to
The fluid tubing string of each step-length is cut again, interlude, approach section is divided into, draws section., will in each material calculation
After extraction section temperature computation is obtained a result, increase certain temperature difference (constant heat flow pattern) or reset temperature (stationary temperature pattern),
Assignment gives approach section, into the calculating of next step-length.
Conversion coefficient K is asked for firstj i：
As (Xi-Yj)*(Yj+1-Xi+1) ＜ 0 when
As (Xi-Yj)*(Yj+1-Xi+1During) >=0
It will obtainNumerical Discrimination whether be more than 1, number value more than 1 is 1, and now below equation is set up：
With TiEach section of temperature of last moment is represented, with TjEach section of temperature of subsequent time is represented, then
Set stratum to be layered as N layers in above formula, the length of current cylinder under certain flow, top are represented using subscript variable
X1—X2For approach section, X2—X3For first layer, X3—X4For the second layer, sort successively, extremely level number successively decreases after heat exchange bottom of the tube,
X2N+1—X2N+2For first layer.Bottom Y1—Y2For first layer, Y2—Y3For the second layer, sort successively, extremely layer after heat exchange bottom of the tube
Number successively decrease, Y2N—Y2N+1For first layer, Y2N+1—Y2N+2To draw section.
T is obtained successivelyjCalculated respectively into horizontal cell afterwards, calculating obtains TiNumerical result enter subsequent cycle.
The present invention realizes constant heat flux method and constant inflow temperature method applicability by multiple input modes, and simulates idle
The hot physical property ginseng of backfilling material and Rock And Soil in the influence that fluid driving power consumption is tested Rock And Soil original temperature during test, device to hole
Number accurate simulation, exchanges the key elements such as heat pipe arrangement and is simulated, and introduce geothermal gradient change and rock mass horizontal slice parameter, choosing
Computing unit volume, the time of each step-length are selected, group hole border is simulated with volume method, group hole heat transfer situation is carried out long-term
Simulation.
The present invention is on the horizontal structure of model, and the heat transfer unit close to heat-transfer pipe is set to 1cm2Size, increases with distance
Greatly, thermograde when periphery conducts heat is tapered into, and computing unit thickness suitably increases, to reduce computing unit quantity,
By the appropriate deformation process of the unit of local irregularities, test data proves to influence minimum to computational accuracy, apart from heat exchanger tube 1-
At 1.5m, radial stratification line is cancelled, computing unit is changed into approximate circle Circle Structure, further reduce computing unit number
Amount, is also allowed in the ring layer providing holes swarm parameter closer to outside, is calculated time step and is set to 10-30s.
The beneficial effects of the invention are as follows：
Three-dimension Numerical Model of the present invention can enter line number to the live geo-thermal response test of constant heat flow operating mode and stationary temperature operating mode
Value simulation, calculates the exchange capability of heat of Rock And Soil thermal physical property parameter and underground pipe, and same process can be used to calculate two kinds of parameters,
Convenient design application.
The present invention utilizes mathematical calculation model, can also export temperature curve from stationary temperature pattern, with actual test number
According to fitting, Rock And Soil comprehensive parameters are calculated, this method is more accurate due to introducing fluid flow data, solving result.
The present invention, can be to the operating condition of Practical Project by the setting for the major parameter that conducted heat to influence underground pipe heat exchanging holes
Simulated, the hole depth that such as exchanges heat, geothermal gradient change, the temperature change feature of ground bulk thermal conductivities, heat exchange tube pitch, heat exchange are tubular
Formula, backfilling material heat transfer property, discontinuous load etc., and calculate backwater or averagely enter return water temperature response, the temperature in Rock And Soil space
Degree response.Reasonably ignore part assumed condition, make the calculation process of complex Three-dimension Numerical Model relatively succinct, protecting
Higher computational accuracy is held while less computing hardware resource can be taken, accelerates arithmetic speed, it is adaptable to group hole long term heat transfer meter
Calculate.
The present invention can become heat exchanging fluid flow parameters input when simulating long-term load loading, obtain phase different in flow rate
Corresponding exchange capability of heat, it is adaptable to the optimization value research of frequency modulation parameters of pump in engineering design.
Brief description of the drawings
Fig. 1 is single U-shaped mathematical calculation model horizontal cell grid Local map.
Fig. 2 is double-U-shaped mathematical calculation model horizontal cell grid Local map.
Fig. 3 is heat exchange tube fluid passage computation model schematic diagram.
Fig. 4 is Rock And Soil vertical section temperature-responsive figure.
Fig. 5 is heat exchanger tube internal flow temperature-responsive figure.
Fig. 6 is the unit linear meter(lin.m.) heat exchange load variations figure of Rock And Soil Depth Stratification.
Fig. 7 is the error schematic diagram that ground bulk thermal conductivities are asked for using conventional line heat source method.
Depth-heat-energy transducer when Fig. 8 is 3 kinds of flows is tried hard to.
Fig. 9 is that single heat exchanging holes are tried hard to fully dense group hole heat-energy transducer.
Embodiment
The present invention sets up the Three-dimension Numerical Model of underground pipe heat exchange, and constant heat flux method and perseverance are realized by multiple input modes
Determine the thermal physical property parameter accurate simulation of backfilling material and Rock And Soil in inflow temperature method applicability, device to hole, exchange heat pipe arrangement etc.
Key element is simulated, and introduces geothermal gradient change and rock mass body horizontal slice parameter, in the case of computational accuracy is ensured, is ignored
Part secondary cause.Group hole border is simulated with the volume method of Rock And Soil, Long-Term Simulations are carried out to group hole heat transfer situation.
Three-dimension Numerical Model of the present invention calculates basic parameter：Flow in pipe；Inflow temperature；Flow media is at different temperatures
Thermal conductivity, dynamic viscosity, Prandtl number change；Pipeline thermal conductivity；Outer diameter tube, internal diameter；Tube shaped；Pipeline enclosure away from；Bore
Bore dia；Drilling depth；Constant temperature layer depth；Geothermal gradient；The comprehensive thermal conductivity of Rock And Soil layering, the comprehensive thermal conductivity of Rock And Soil layering
Rate of change at different temperatures；Backfilling material thermal conductivity, volumetric heat capacity；The change of backfilling material thermal conductivity at different temperatures
Rate.
The present invention is simplified model, and the parameter ignored has：Density, the specific heat capacity of flow media at different temperatures change；
Pipeline thermal capacitance is considered as identical with backfilling material；The thermal contact resistance of pipeline and backfilling material, backfilling material and hole wall；To simplify numerical value
Calculate the error come to the appropriate Zona transformans that elementary volume, volume element is set；Temperature inequality when flow media is turbulent in pipeline；Hole
Bottom u shaped connector influence；Earth's surface temperature Change influences；By the factors such as geothermal gradient temperature in vertical direction when threedimensional model is layered
Small heat transfer caused by difference.
It is larger that numerical computations of the present invention take computer resource, it is necessary to coordinate computing unit fine degree and calculating time it
Between contradiction, selection reasonable computation unit volume, the time of each step-length.In general, the grid of mathematical calculation model
It is finer, computational accuracy can be more improved, reflects actual heat transfer conditions.But excessively fine calculating is wanted to computer hardware
Ask also higher, make the calculating time elongated, program operation debugging error correction is difficult.
The model of foundation is numerical discretization type, is divided to two levels：Horizontal structure and vertical stratification.
Accompanying drawing 1, accompanying drawing 2 are the computation model horizontal cell grid partial structurtes on horizontal cross-section.Accompanying drawing 1 is single U-shaped 2
Heat exchange pipeline, accompanying drawing 2 is double-U-shaped 4 heat exchange pipelines.On the horizontal structure of model, between 2 or 4 heat exchanger tubes holding fixations
Computing unit away from, every pipe periphery radially, Level Expand, the heat transfer unit close to heat-transfer pipe is set to 1cm2Size,
With distance increase, thermograde when periphery conducts heat is tapered into, and computing unit thickness suitably increases, and calculates single to reduce
First quantity.By the appropriate deformation process of the unit of local irregularities, test data proves to influence minimum to computational accuracy.Changed in distance
At heat pipe 1-1.5m, radial stratification line is cancelled, computing unit is changed into approximate circle Circle Structure, further reduce and calculate single
First quantity, is also allowed in the ring layer providing holes swarm parameter closer to outside.Calculate time step and be set to 10-30s.The model feature
For the computing unit volume increase in control error zone of reasonableness, computing unit quantity is reduced, and is adapted to (the several months-number for a long time
Year) Calculation of Heat Transfer.
Numerical Heat Transfer model basic calculating formula is as follows：
The heat that each computing unit unit temperature change needs：
QV=V0*ρc*K
QV--- the volumetric heat capacity amount of computing unit；
V0--- the volume of computing unit；
The volumetric heat capacity of ρ c --- computing unit；
K --- border coefficient, in the approximate simulation poroid state of group, exchanges heat pitch of holes as reference, horizontal model using underground pipe
The relative ratio with original equivalent volume reduction of outside ring layer, span：0 ＜ K≤1；
Thermal resistance of each computing unit in different directions：
(radial direction)
(circumferencial direction deformation process approximate with irregular unit)
λS=λ0+a*T
Ri--- the thermal resistance of the unit adjacent with calculating grid cell；
R0--- the thermal resistance of computing unit；
M --- radial number of partitions, when ring layer unit is beyond heat exchanger tube 1-1.5m, M=1；
λS--- the thermal conductivity of Rock And Soil stratum or pipeline at a certain temperature；
d0--- the external diameter of the circle where computing unit segmental arc；
di--- the internal diameter of the circle where computing unit segmental arc；
L --- computing unit length or segmental arc length；
S --- computing unit sectional area；
λ0--- the thermal conductivity of Rock And Soil stratum or pipeline under fiducial temperature；
The thermal conductivity variation coefficient of a --- Rock And Soil stratum or pipeline at different temperatures；
The grid cell temperature at T --- certain moment.
R0Computational methods and RiIt is identical.
Pipeline heat convection thermal resistance is controlled by internal diameter of the pipeline, flow velocity, fluid temperature (F.T.) and fluid parameter, is intended using empirical equation
Conjunction is obtained, and is calculated when needing and RiSuperposition.Heat convection thermal resistance R when heat transferring medium fluid is pure waterfIt is as follows：
λW=-1.78*10-5*TW 2+2.84*10-3*TW+0.55
μ=5.91*10-4*TW 2-5.1*10-2*TW+1.79
Pr=5.4*10-3*TW 2-4.4*10-1*TW+13.67
λW--- the thermal conductivity of water；
TW--- the temperature of water；
The mobilization dynamic viscosity of μ --- water；
The Prandtl number of Pr --- water.
Nμ=0.027*Re0.8*Pr0.33
Re--- the Reynolds number of water；
The density of ρ --- water；
The flow velocity of V --- water.
D --- internal diameter of the pipeline；
Nμ--- the nusselt number of water；
The convection transfer rate of η --- water；
Rf--- the heat convection thermal resistance of water.
In a time step, the temperature-responsive of all units is calculated one by one, is then transferred to next time step weight
New assignment is calculated：
T ＇ --- the grid cell temperature that need to be calculated during next step-length；
Ti--- temperature of the unit adjacent with calculating grid cell at certain moment；
JS--- the time of each material calculation；
N --- the quantity of the unit adjacent with calculating grid cell.
In the vertical length of heat exchanger tube, the temperature of diverse location tube fluid has bigger difference, simply calculates past
Toward this difference is equalized, such as《Ground source heat pump project technical specification》Annex content.In order to be stated in Numerical Heat Transfer model
This difference and influence, are divided into multigroup superimposed structure, to represent different depth ground by network shown in accompanying drawing 1, accompanying drawing 2
Body stratum.
In the vertical direction of model, each computing unit is set according to about 5-10m, when the flow velocity of water in heat exchanger tube is set to
0.4-0.6m/s, in time step 10-30s, media flow distance also vertically calculates element length or so at one, vertically
The heat transfer that model can use less layering number to reflect different depth changes.To simplify calculating, by actual geothermal gradient
Heat transfer between caused vertical computing unit is not considered, on larger axial length, the influence to result of calculation compared with
Small, its error can be ignored.
Heat exchange tube fluid is continuously moved in practice, and using Differential Principle, fluid is cut into a series of long columns
Shape body, stroboscopic motion is considered as by continuous flowing.In each material calculation, by the interrupted passage of each step, simulation pipe is interior
Temperature transmission state.The pushing distance of each step of tube fluid is related to flow velocity, caliber, differs with the vertical length of hierarchical mode
Cause, it is necessary to be cut again to the fluid tubing string of each step-length.Computational methods are shown in accompanying drawing 3.
The top of accompanying drawing 3 represents a certain moment current wise temperature situation, and bottom represents subsequent time temperature computation result.
X1、X2、Y1、Y2Deng one-dimensional coordinate numerical variable is represented, set stratum to be layered as N layers, current under certain flow are represented using variable
The length of cylinder, top X1—X2For approach section, X2—X3For first layer, X3—X4For the second layer, sort successively, to heat exchanger tube bottom
Level number successively decreases behind portion, X2N+1—X2N+2For first layer.Bottom Y1—Y2For first layer, Y2—Y3For the second layer, sort successively, to changing
Level number successively decreases behind heat pipe bottom, Y2N—Y2N+1For first layer, Y2N+1—Y2N+2To draw section.Section temperature computation will be drawn and draw knot
After fruit, increase certain temperature difference (constant heat flow pattern) or reset temperature (stationary temperature pattern), assignment and approach section, into next
The calculating of step-length.
Conversion coefficient K is asked for firstj i：
As (Xi-Yj)*(Yj+1-Xi+1) ＜ 0 when
As (Xi-Yj)*(Yj+1-Xi+1During) >=0
K will be obtainedj iNumerical Discrimination whether be more than 1, number value more than 1 is 1.Now below equation is set up：
With TiEach section of temperature of last moment is represented, with TjEach section of temperature of subsequent time is represented, then
T is obtained successivelyjCalculated respectively into horizontal cell shown in accompanying drawing 1 afterwards, calculating obtains TiNumerical result enter it is next
Circulation.
Embodiment
Accompanying drawing 4 is the Rock And Soil vertical section temperature-responsive in the individually imbedded pipe heat-exchanging hole after the different load times, left figure table
Show when the load time is shorter, the vertical Lamellar character of display geothermal gradient in the outside at heat exchanging holes center is obvious；Right figure is loading
When time is longer, the original temperature gradient on stratum is with loading load joint effect Rock And Soil temperature change.
Accompanying drawing 5 is heat exchanger tube internal flow temperature distribution state, left figure is constant heat flow operating mode, from bottom to top 4 curves
Time be respectively at 24h, 48h, 72h, 96h, abscissa depth 0m be heat exchanger tube current out temperature, temperature difference is at 4 at this
All it is identical on time point；Right figure is stationary temperature operating mode, and the time of 4 curves is identical with left figure, in heat exchanger tube inlet temperature
In the case of constant, curve bottom is gradually moved up, and heat exchanger tube outlet temperature becomes larger, as the stationary temperature load on time prolongs
Long, outlet temperature amplitude of variation diminishes.
Accompanying drawing 6 is the average linear meter(lin.m.) heat exchange power situation of change of the Rock And Soil different depth under constant heat flow pattern.In three-dimensional
In numerical model, heat exchange hole depth 100m is set, there is the larger abnormal stratum of thermal conductivity at 40-50m, other depth are phase
To less numerical value.It can be seen that, when applying constant load completely to whole ground heat exchanger, underground pipe different depth position
Unit heat exchange power has changed over time large change, not consistent with entering the constant data that is obtained measured by water return outlet, wherein
The changed power of about 45m depths is more obvious.This heat exchange power changes with time only when the testing time is longer
(after 40-50h) can be reduced, so can directly be produced come the mode of layered method ground thermal conductivity using constant heat flow line source model
Raw certain error, it is necessary to corrected using the comprehensive threedimensional model of parameter.
Accompanying drawing 7 is the calculation error that conventional line source model is corrected using threedimensional model, and conventional line source model is in permanent heat
During the ground bulk thermal conductivities parameter asked under stream operating mode, changed larger with heat exchanging holes effect of depth by media fluid flow.Work as stream
Amount gets over hour, because liquid mass flow change and the wall coefficient of heat transfer change, the Rock And Soil asked for using usual manner it is comprehensive
Close thermal conductivity deviation bigger, and increased with heat exchange well depth, error increase is different with the load mode of test, summer condition
The ground bulk thermal conductivities numerical bias asked for winter condition is reverse.
Accompanying drawing 8 is that under stationary temperature pattern, heat exchanging holes are calculated under different fluid flow parameter by depth using threedimensional model
Degree change effect, when the hole depth that exchanges heat is increased, it is necessary to improve fluid flow, the heat-energy transducer just accordingly increased
Power.Influenceed by geothermal gradient, exchange capability of heat of the summer condition with winter condition when depth is increased changes difference, summer work
As depth is increased during condition, the increased amplitude of its exchange capability of heat is relatively small.
Accompanying drawing 9 illustrate to the exchange capability of heat in individually imbedded pipe heat-exchanging hole and the fully dense group hole of equivalent volume method it is long when
Between simulate.It can be seen that, under the fully dense poroid state of group, the exchange capability of heat of various different parameters heat exchanging holes gradually subtracts after 10-20d
Small, its amplitude reduced exceedes single heat exchanging holes；After the long period, exchange capability of heat curve declines state in approximately linear,
The form declined with single heat exchanging holes approximate log curve is gradually disengaged.In Practical Project, the heat exchange in a number of group hole
Therebetween, its temperature-responsive can use Three-dimension Numerical Model equivalent volume method simulation meter to power curve with heat exchange power
Calculate.
Claims (3)
1. the vertical underground pipe heat transfer Three-dimension Numerical Model of earth source heat pump, it is characterised in that：To the computing unit application energy in model
Amount conservation principle sets up discrete equation, and each computing unit has between fixed thermal capacitance, computing unit with the connection of corresponding thermal resistance,
Model is divided to two layer of structure：Horizontal structure and vertical stratification；Horizontal structure partial simulation calculates the list centered on underground pipe
First heat transfer radially with circumferencial direction, vertical stratification partial simulation calculates the axial temperature change of underground pipe internal flow,
Level calculation unit is the Circle Structure decomposed, 2 or 4 heat exchanger tubes holding constant spacings, the calculating on every pipe periphery
Unit radially, Level Expand；
The heat that each computing unit unit temperature change needs：
QV=V0*ρc*K
QV--- the volumetric heat capacity amount of computing unit；
V0--- the volume of computing unit；
The volumetric heat capacity of ρ c --- computing unit；
K --- border coefficient, in the approximate simulation poroid state of group, exchanges heat pitch of holes as reference, outside horizontal model using underground pipe
The relative ratio with original equivalent volume reduction of portion's ring layer, span：0 ＜ K≤1；
Thermal resistance of each computing unit in different directions：
Radially：
The approximate processing of circumferencial direction and irregular unit
λS=λ0+a*T
Ri--- the thermal resistance of the unit adjacent with calculating grid cell；
R0--- the thermal resistance of computing unit；
M --- radial number of partitions, when ring layer unit is beyond heat exchanger tube 1-1.5m, M=1；
λS--- the thermal conductivity of Rock And Soil stratum or pipeline at a certain temperature；
d0--- the external diameter of the circle where computing unit segmental arc；
di--- the internal diameter of the circle where computing unit segmental arc；
L --- computing unit length or segmental arc length；
S --- computing unit sectional area；
λ0--- the thermal conductivity of Rock And Soil stratum or pipeline under fiducial temperature；
The thermal conductivity variation coefficient of a --- Rock And Soil stratum or pipeline at different temperatures；
The grid cell temperature at T --- certain moment；
R0Computational methods and RiIt is identical；
Pipeline heat convection thermal resistance RfControlled, be fitted using empirical equation by internal diameter of the pipeline, flow velocity, fluid temperature (F.T.) and fluid parameter
Obtain, calculate the R that is added to when needingiAmong；
In a time step, the temperature-responsive of all grid cells is calculated one by one, is then transferred to next time step weight
New assignment is calculated：
T ＇ --- the grid cell temperature that need to be calculated during next step-length；
Ti--- temperature of the unit adjacent with calculating grid cell at certain moment；
JS--- the time of each material calculation；
N --- the quantity of the unit adjacent with calculating grid cell；
Vertical stratification part, is divided into multigroup superimposed structure by horizontal grid structure, to represent different depth Rock And Soil stratum, changes
Hot tube fluid is continuously moved in practice, and using Differential Principle, fluid is cut into a series of long column shape bodies, will be continuous
Flowing is considered as stroboscopic motion, in each material calculation, by the interrupted passage of each step, and temperature transmits shape in simulation pipe
State, the pushing distance of each step of tube fluid is related to flow velocity, caliber, inconsistent, it is necessary to every with hierarchical mode vertical length
The fluid tubing string of one step-length is cut again, is divided into interlude, approach section, is drawn section.In each material calculation, it will draw
After section temperature computation is obtained a result, increase certain temperature difference (constant heat flow pattern) or reset temperature (stationary temperature pattern), assignment
Approach section is given, into the calculating of next step-length；
Conversion coefficient is asked for first
As (Xi-Yj)*(Yj+1-Xi+1) ＜ 0 when
As (Xi-Yj)*(Yj+1-Xi+1During) >=0
It will obtainNumerical Discrimination whether be more than 1, number value more than 1 is 1, and now below equation is set up：
With TiEach section of temperature of last moment is represented, with TjEach section of temperature of subsequent time is represented, then
Set stratum to be layered as N layers in above formula, the length of current cylinder under certain flow, top X are represented using subscript variable1—
X2For approach section, X2—X3For first layer, X3—X4For the second layer, sort successively, extremely level number successively decreases after heat exchange bottom of the tube, X2N+1—
X2N+2For first layer.Bottom Y1—Y2For first layer, Y2—Y3For the second layer, sort successively, extremely level number successively decreases after heat exchange bottom of the tube,
Y2N—Y2N+1For first layer, Y2N+1—Y2N+2To draw section；
T is obtained successivelyjCalculated respectively into horizontal cell afterwards, calculating obtains TiNumerical result enter subsequent cycle.
The method for building up of Three-dimension Numerical Model 2. a kind of vertical underground pipe of earth source heat pump as claimed in claim 1 conducts heat, it is special
Levy and be：Constant heat flux method and constant inflow temperature method applicability are realized by multiple input modes, and when simulating idle test
The thermal physical property parameter of backfilling material and Rock And Soil is accurate in the influence that fluid driving power consumption is tested Rock And Soil original temperature, device to hole
Simulation, exchanges the key elements such as heat pipe arrangement and is simulated, and introduces geothermal gradient change and rock mass horizontal slice parameter, selection calculating
The time of unit volume, each step-length, group hole border is simulated with volume method, Long-Term Simulations are carried out to group hole heat transfer situation.
The method for building up of Three-dimension Numerical Model, its feature 3. the vertical underground pipe of earth source heat pump according to claim 2 conducts heat
It is：On the horizontal structure of model, the heat transfer unit close to heat-transfer pipe is set to 1cm2Size, increases, outer part with distance
Divide thermograde during heat transfer to taper into, computing unit thickness suitably increases, to reduce computing unit quantity, do not advised local
The appropriate deformation process of unit then, at heat exchanger tube 1-1.5m, radial stratification line is cancelled, computing unit is changed into approximate
Circular Circle Structure, further reduces computing unit quantity, also allows in the ring layer providing holes swarm parameter closer to outside, calculates
Time step is set to 10-30s.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710598336.6A CN107274473A (en) | 2017-07-21 | 2017-07-21 | Three-dimensional numerical model for heat transfer of vertical buried pipe of ground source heat pump and establishment method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710598336.6A CN107274473A (en) | 2017-07-21 | 2017-07-21 | Three-dimensional numerical model for heat transfer of vertical buried pipe of ground source heat pump and establishment method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN107274473A true CN107274473A (en) | 2017-10-20 |
Family
ID=60078367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710598336.6A Pending CN107274473A (en) | 2017-07-21 | 2017-07-21 | Three-dimensional numerical model for heat transfer of vertical buried pipe of ground source heat pump and establishment method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN107274473A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109948182A (en) * | 2019-01-30 | 2019-06-28 | 西安交通大学 | A kind of calculation method for mid-deep strata geothermal well well spacing |
| CN110489912A (en) * | 2019-08-27 | 2019-11-22 | 北京石油化工学院 | A kind of method of solar cross-season soil thermal storage hierarchy slicing numerical simulation |
| CN111551288A (en) * | 2020-05-13 | 2020-08-18 | 山东建筑大学 | Prediction method for circulating liquid temperature of middle-deep layer U-shaped heat exchange well |
| CN111639378A (en) * | 2020-05-27 | 2020-09-08 | 西华大学 | Method for simulating hourly numerical value of heat exchange performance of underground air pipe |
| CN112489160A (en) * | 2019-09-11 | 2021-03-12 | 核工业二一六大队 | Uranium ore pumping test duration curve drawing method |
| CN112632788A (en) * | 2020-12-28 | 2021-04-09 | 中国科学技术大学 | Thermal response test method for rock-soil thermal conductivity distribution |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103034768A (en) * | 2012-12-25 | 2013-04-10 | 华汇工程设计集团股份有限公司 | Design method of buried heat exchange system |
| CN104317991A (en) * | 2014-10-11 | 2015-01-28 | 中建三局第三建设工程有限责任公司 | Reliability design method and device of buried pipe of ground source heat pump |
| CN104318124A (en) * | 2014-11-11 | 2015-01-28 | 合肥天地源节能技术开发有限公司 | Heat exchange capability computing method of ground source heat pump underground heat exchanger |
-
2017
- 2017-07-21 CN CN201710598336.6A patent/CN107274473A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103034768A (en) * | 2012-12-25 | 2013-04-10 | 华汇工程设计集团股份有限公司 | Design method of buried heat exchange system |
| CN104317991A (en) * | 2014-10-11 | 2015-01-28 | 中建三局第三建设工程有限责任公司 | Reliability design method and device of buried pipe of ground source heat pump |
| CN104318124A (en) * | 2014-11-11 | 2015-01-28 | 合肥天地源节能技术开发有限公司 | Heat exchange capability computing method of ground source heat pump underground heat exchanger |
Non-Patent Citations (4)
| Title |
|---|
| 张晓伟 等: "地源热泵单U型地埋管换热器的传热模拟分析", 《制冷》 * |
| 战国会: "地源热泵U型竖直埋管钻孔外传热模型研究", 《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》 * |
| 王泽生 等: "地源热泵U型埋管换热器动态传热特性的数值分析", 《河北工业大学学报》 * |
| 赵卓新 等: "影响竖直地埋管深度的因素分析", 《河北工程大学学报(自然科学版)》 * |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109948182A (en) * | 2019-01-30 | 2019-06-28 | 西安交通大学 | A kind of calculation method for mid-deep strata geothermal well well spacing |
| CN109948182B (en) * | 2019-01-30 | 2020-10-27 | 西安交通大学 | Calculation method for well spacing of middle-deep geothermal well |
| CN110489912A (en) * | 2019-08-27 | 2019-11-22 | 北京石油化工学院 | A kind of method of solar cross-season soil thermal storage hierarchy slicing numerical simulation |
| CN110489912B (en) * | 2019-08-27 | 2022-12-13 | 北京石油化工学院 | Method for simulating numerical value of solar cross-season soil heat storage layered slice |
| CN112489160A (en) * | 2019-09-11 | 2021-03-12 | 核工业二一六大队 | Uranium ore pumping test duration curve drawing method |
| CN111551288A (en) * | 2020-05-13 | 2020-08-18 | 山东建筑大学 | Prediction method for circulating liquid temperature of middle-deep layer U-shaped heat exchange well |
| CN111639378A (en) * | 2020-05-27 | 2020-09-08 | 西华大学 | Method for simulating hourly numerical value of heat exchange performance of underground air pipe |
| CN112632788A (en) * | 2020-12-28 | 2021-04-09 | 中国科学技术大学 | Thermal response test method for rock-soil thermal conductivity distribution |
| CN112632788B (en) * | 2020-12-28 | 2022-09-06 | 中国科学技术大学 | Thermal response test method for rock-soil thermal conductivity distribution |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107274473A (en) | Three-dimensional numerical model for heat transfer of vertical buried pipe of ground source heat pump and establishment method thereof | |
| Fadejev et al. | A review on energy piles design, sizing and modelling | |
| Hu | An improved analytical model for vertical borehole ground heat exchanger with multiple-layer substrates and groundwater flow | |
| Li et al. | Experimental and numerical studies on heat transfer characteristics of vertical deep-buried U-bend pipe to supply heat in buildings with geothermal energy | |
| Kurevija et al. | Effect of borehole array geometry and thermal interferences on geothermal heat pump system | |
| Yang et al. | Experimental and numerical investigations on the thermal performance of a horizontal spiral-coil ground heat exchanger | |
| Zhang et al. | Experimental study on the thermal performance of tunnel lining GHE under groundwater flow | |
| Li et al. | Experimental and numerical studies on heat transfer characteristics of vertical deep-buried U-bend pipe in intermittent heating mode | |
| Li et al. | The influence of soil thermal properties on the operation performance on ground source heat pump system | |
| Zhang et al. | Heat transfer analysis of U-type deep borehole heat exchangers of geothermal energy | |
| CN110968967B (en) | Heat transfer coupling simulation order reduction method for underground pipe heat exchanger | |
| CN110826225B (en) | Vertical single-U-shaped buried pipe heat exchanger temperature field analysis method | |
| Zhang et al. | Comparison of test methods for shallow layered rock thermal conductivity between in situ distributed thermal response tests and laboratory test based on drilling in northeast China | |
| Cui et al. | Advances in ground heat exchangers for space heating and cooling: Review and perspectives | |
| CN109086560A (en) | The vertical single U-shaped underground pipe fluid temperature (F.T.) distribution forecasting method of earth source heat pump under variable working condition | |
| CN112597639B (en) | Heat transfer dimension reduction analysis method and system for porous buried pipe heat exchanger | |
| Mingzhi et al. | A novel model and heat extraction capacity of mid-deep buried U-bend pipe ground heat exchangers | |
| CN112016214B (en) | Heat transfer calculation method and system for buried pipe heat exchanger based on resistance-capacitance model | |
| Wang et al. | Numerical simulation of ground heat exchangers based on dynamic thermal boundary conditions in solid zone | |
| Wang et al. | Experimental and numerical investigations on the thermal behavior of ground heat exchanger in stratified soils across unsaturated and saturated layers | |
| Wang et al. | Thermal performance analysis of ground source heat pump system for low-temperature waste heat recovery storage | |
| CN106354984B (en) | Temperature response calculation method of pile foundation spiral buried pipe under underground water seepage condition | |
| Abbas et al. | Performance analysis of seasonal soil heat storage system based on numerical simulation and experimental investigation | |
| Li et al. | An inversion method to estimate the thermal properties of heterogeneous soil for a large-scale borehole thermal energy storage system | |
| Zhao et al. | Dynamic numerical investigation of the long-term performance of a GSHP system considering groundwater seepage and layered subsurface coupling conditions |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20171020 |