CN110826221A - Method for decoupling indoor temperature field of building - Google Patents
Method for decoupling indoor temperature field of building Download PDFInfo
- Publication number
- CN110826221A CN110826221A CN201911065325.7A CN201911065325A CN110826221A CN 110826221 A CN110826221 A CN 110826221A CN 201911065325 A CN201911065325 A CN 201911065325A CN 110826221 A CN110826221 A CN 110826221A
- Authority
- CN
- China
- Prior art keywords
- temperature
- heat
- indoor
- field
- air
- 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
Images
Landscapes
- Air Conditioning Control Device (AREA)
Abstract
The invention provides a method for decoupling a building indoor temperature field, which comprises the following steps of firstly determining all thermal factors in a building; determining the type of an indoor flow field, and respectively setting a plurality of representative flow fields according to the different types of the flow fields; then, calculating a representative flow field by using convection-radiation coupling simulation; fixing a representative flow field, setting a single thermal factor, and calculating the temperature distribution of each thermal factor; calculating the CRI value of a single thermal factor; calculating to obtain each sub-temperature field by utilizing the calorific value or the heat absorption capacity of the thermal factor according to the CRI definition formula; determining whether all representative flow fields have been decoupled; each total temperature field is a linear composite of all its corresponding sub-temperature fields. The invention quantitatively evaluates the force range of each thermal factor in the space, independently analyzes the influence of different thermal factors on the space temperature field, more effectively and more quickly predicts the indoor temperature distribution, and can efficiently and accurately regulate and control the indoor local temperature environment by independently regulating and controlling the intensity of the indoor heat source or heat sink.
Description
Technical Field
The invention relates to the technical field of building indoor temperature distribution simulation calculation, in particular to a method for decoupling a building indoor temperature field.
Background
With the continuous development of social economy, more and more diversified indoor buildings are gradually increased. With the continuous improvement of living standard, the requirement of people on the comfort level of living environment or working environment is higher and higher, and the requirement on the thermal design of indoor buildings is higher and higher.
At present, when an indoor building is subjected to thermal design, Computational Fluid Dynamics (CFD) is used as a numerical analysis tool, and boundary conditions and initial conditions are obtained according to load and design standards. When building energy consumption simulation is carried out, the indoor air is generally uniformly mixed and the indoor temperature at any point is equal. However, the temperature and speed of indoor air exist in three dimensions, and especially in recent years, the large number of applications of work environment air conditioning systems, personal air conditioning systems, displacement ventilation, and floor heating systems, rather than assuming uniform and equal temperatures throughout the space, actively and effectively use airflow distribution and temperature distribution to control the temperature of the necessary indoor space. The effective utilization of the uneven indoor environment improves the energy efficiency while satisfying thermal comfort.
Computational Fluid Dynamics (CFD) can compute the distribution of air flow and temperature in detail, thus serving as a tool for predicting indoor thermal comfort and evaluating indoor air quality. However, since the indoor temperature field is affected by many thermal factors, when any thermal factor changes, re-simulation and calculation are required, and thus the computational load of CFD is large.
Disclosure of Invention
In view of this, in order to predict the indoor temperature distribution more efficiently and more quickly, it is necessary to analyze the influence of different thermal factors on the spatial temperature field independently and quantitatively evaluate the potential force range of each thermal factor in the space. The invention provides a method for decoupling a building Indoor temperature field, which obtains a new parameter capable of representing a CFD simulation result, namely CRI (probability of index simulation) based on a CFD data result. The CRI is defined as the ratio of the temperature rise of a certain point caused by any heat source to the absolute value of the temperature rise of the certain point under the condition of completely and uniformly mixing the heat generated by the heat source, or the ratio of the temperature drop of the certain point caused by any heat sink to the absolute value of the temperature drop of the certain point under the condition of completely and uniformly mixing the heat generated by the heat sink. The CRI can independently evaluate the influence of influencing factors (hereinafter referred to as thermal factors) of any indoor temperature field on the temperature of any point in the room, reflects the structure of the indoor temperature field, and can make the CFD result more effectively applied to analysis and design.
The technical scheme of the invention is as follows:
a method of decoupling a building indoor temperature field, comprising the steps of:
step S1, determining all heat factors in the building room;
step S2, determining the type of the indoor flow field, and if the type is the forced convection main flow field, entering step S3; if the natural convection main flow field is present, the step S4 is executed;
step S3, setting at least one representative forced convection field according to the air supply volume or the air speed and the direction according to different air speeds or air volume requirements in the building, wherein the indoor flow field is a forced convection leading flow field;
step S4, setting a plurality of representative natural convection fields if the indoor flow field is changed due to the change of the heat productivity of the indoor heat source, wherein the indoor flow field is a natural convection leading flow field;
step S5, calculating a representative flow field by using convection-radiation coupling simulation;
step S6, fixing the representative flow field, setting a single thermal factor, and calculating the temperature distribution of each thermal factor by using CFD;
step S7, calculating the CRI value of the single thermal factor;
step S8, whether the CRI values of all thermal factors are calculated completely, if not, the step S6 is returned, and if yes, the step S9 is reached;
step S9, calculating each sub-temperature field by utilizing the calorific value or the heat absorption capacity of the thermal factor according to the CRI definition formula;
step S10, whether the temperature fields under all the representative flow fields are decoupled is finished, if yes, the step S11 is carried out, and if not, the step S6 is returned;
and step S11, decoupling the temperature fields, wherein the total temperature field is the linear synthesis of all the sub temperature fields.
Further, the thermal factor includes a heat source term and a heat sink term.
Further, the heat source term transfers heat to the air in the building room, and the heat sink term absorbs heat from the air in the building room.
Further, the representative flow field is defined as: all thermal factor effects are included and the temperature is maintained at a neutral temperature.
Further, the neutral temperature is the design temperature of the building interior.
Further, the representative flow field is calculated as follows: and inputting the boundary conditions in the building room and the influence of all thermal factors in the building room into a Computational Fluid Dynamics (CFD) analysis tool, and calculating by using the CFD analysis tool.
Furthermore, the enclosure structure is heat-insulated, and a heat source with the same calorific value is arranged in the nearest surface layer of the enclosure structure to transfer heat to air; the air supply item is processed in such a way that neutral temperature air is heated or cooled by a corresponding heat source or heat sink at an air supply port and then is sent into a room; setting the temperature of the exhaust item higher than the neutral temperature as a heat sink and lower than the neutral temperature as a heat source; and boundary conditions corresponding to the enclosure structure, the air supply item and the air exhaust item are processed to be adiabatic or the heating temperature is neutral.
Further, the way to calculate the temperature distribution of the single thermal factor is: and inputting the influence of the single thermal factor into a computational fluid dynamics analysis tool CFD, and setting the rest thermal factors as adiabatic or exothermic temperature as neutral temperature.
Further, in the forced convection field, the thermal factor m is at xiThe CRI value of a point is calculated by the formula:
wherein:
xispatial coordinates;
θn: indoor neutral temperature;
θm,o: thermal factor m heat dissipation QmIndoor temperature during uniform diffusion;
Δθm,o＝θm,o-θn: the temperature difference between the uniform diffusion temperature and the neutral temperature;
θm(xi): thermal factor m is in xiTemperature rise due to point;
Δθm(xi)＝θm(xi)-θn: the temperature difference between the heat dissipation temperature rise and the neutral temperature is obtained by the thermal factor m;
Cp: indoor air specific heat capacity;
ρ: the density of the air;
f: the amount of air supplied.
Further, in natural convection fields, the thermal factor m is at xiThe CRI value of a point is calculated by the formula:
wherein:
uθm(xi): calculating x by CFD when heat source and heat sink are set simultaneouslyiPoint temperature;
u: heat sinks are uniformly arranged;
θn: indoor neutral temperature;
The invention has the beneficial effects that:
the CRI can evaluate the independent influence of any indoor thermal factor on the temperature of any point, and effectively analyze the temperature composition of any point, so that the intensity of a heat source or a heat sink in a room can be independently adjusted and controlled according to the requirement to efficiently and accurately regulate and control the indoor local temperature environment.
The CRI is a parameter which is obtained based on the CFD calculation result and can represent the simulation result thereof, and since any thermal influence factor condition is changed in the CFD calculation, the CFD simulation calculation is performed again, the calculation load is large, and the calculation time is long. Therefore, within the range of acceptable error, the CRI model can replace CFD simulation, so that the calculation speed is greatly improved.
In the energy consumption simulation considering the temperature distribution, the CRI can be used for quickly obtaining the indoor temperature distribution according to the change of the heat influence factor, so that the temperature condition is provided for the energy consumption simulation, the dynamic simulation is realized, and the accuracy of the simulation result is greatly improved. Meanwhile, the CRI can be well applied in the initial stage of building design. The designer can independently adjust the position of the air inlet, the air supply quantity, the air supply temperature and the like according to the requirement of the indoor thermal environment under the condition of not changing other conditions until the indoor thermal environment achieves the expected effect. In the combined type and distributed terminal system, each terminal system can be regulated and controlled according to the CRI value of each terminal system, so that the indoor thermal environment is controlled, and the design of the combined type and distributed terminal system is optimized.
Drawings
FIG. 1 is a flow chart of a method of analyzing the indoor temperature distribution of a building according to the present invention;
FIG. 2 is a diagram of a building model according to a first embodiment of the present invention;
FIG. 3 is a block diagram of a simulation model of a flow field and a temperature field according to an embodiment of the present invention;
FIG. 3(a) is a velocity profile of a simulated flow field and temperature field according to an embodiment of the present invention;
FIG. 3(b) is a temperature profile of a simulated flow field and temperature field in accordance with an embodiment of the present invention;
FIG. 3(c) is a surface temperature distribution diagram of the exterior wall and the exterior window of a simulated flow field and temperature field according to an embodiment of the present invention;
FIG. 3(d) is a diagram showing the surface temperature distribution of a partition wall simulating a flow field and a temperature field according to an embodiment of the present invention;
FIG. 3(e) is a ceiling surface temperature profile of a simulated flow and temperature field according to an embodiment of the present invention;
FIG. 3(f) is a graph of a floor surface temperature profile for a simulated flow and temperature field in accordance with an embodiment of the present invention;
FIG. 4 is a schematic diagram of all thermal factor compositions of an indoor building simulating the distribution of CRI according to a first embodiment of the present invention;
fig. 4(a) is a schematic diagram illustrating the distribution of CRI of an outer window according to a first embodiment of the present invention;
fig. 4(b) is a schematic diagram illustrating the distribution of CRI of an exterior wall according to a first embodiment of the present invention;
FIG. 4(c) is a schematic diagram illustrating the CRI distribution of the internal thermal load according to the first embodiment of the present invention;
fig. 4(d) is a schematic diagram of the distribution of CRI of the partition wall and the floor according to the first embodiment of the present invention;
fig. 4(e) is a schematic view showing the distribution of CRI of the cooling ceiling according to the first embodiment of the present invention.
Detailed Description
The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
The embodiments of the present disclosure are described below with specific examples, and other advantages and effects of the present disclosure will be readily apparent to those skilled in the art from the disclosure in the specification. It is to be understood that the described embodiments are merely illustrative of some, and not restrictive, of the embodiments of the disclosure. The disclosure may be embodied or carried out in various other specific embodiments, and various modifications and changes may be made in the details within the description without departing from the spirit of the disclosure. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
Example one
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
The invention discloses a method for decoupling a building indoor temperature field, which comprises the following specific steps:
in step S1, all thermal factors in the building are first determined.
The thermal factor includes a heat source term and a heat sink term. CRI is the study of the effect of individual thermal factors on a temperature field, and first determines the thermal factor of a particular heat source or sink within the temperature field. The indoor heat environment can be influenced by a plurality of heat factors from indoor and outdoor, and mainly comprises building envelope heat transfer, air conditioning system cold and hot air supply, radiation cold or heat supply, ventilation, infiltration and light, equipment and human body heat production, the heat factors have respective heat transfer characteristics, and the indoor temperature is increased or decreased through convection, namely, the heat factors are expressed as heat transfer to indoor air or heat absorption from air, therefore, the heat factors are set as heat source items or heat sink items, the heat source items are expressed as heat production to air, and the heat sink items are expressed as heat absorption from air whether the heat factors are controllable or not.
Step S2, determining the type of the indoor flow field, and if the type is the forced convection main flow field, entering step S3; if the flow field is dominant by natural convection, the process proceeds to step S4
The indoor flow field is mainly divided into a forced convection main flow field and a natural convection main flow field, when a mechanical ventilation system is arranged indoors and has relatively large air supply quantity, the mechanical ventilation system plays a leading role in the formation of the indoor flow field, and the flow field is the forced convection main flow field; when no mechanical ventilation system is arranged in the room, a heat source exists in the room and temperature difference is formed, and at the moment, the indoor flow field is mainly formed due to the buoyancy effect of air, namely the natural convection leading flow field.
Step S3, setting a plurality of representative forced convection fields according to the air supply volume or the size and direction of the air speed according to the requirement of different indoor air speeds or air volumes of the building
The wind speed or wind volume required by different times in a building room is not constant, and after the wind speed or wind volume is adjusted, an indoor flow field is changed definitely, namely a representative flow field for calculating the CRI is changed, and at the moment, the CRI is also changed. Therefore, a plurality of representative flow fields can be arranged according to the requirement of adjusting air quantity or wind speed, and any representative flow field has corresponding CRI distribution.
S4, 4, the indoor flow field is a natural convection leading flow field, if the heat quantity change of the indoor heat source is large, a plurality of representative natural convection fields can be arranged
In a natural convection main flow field, the CRI is calculated as the ratio of the temperature rise (or temperature drop) of any indoor heat source (or heat sink) to the heat productivity of the heat source at a certain point. When the heat value of the indoor heat source is greatly changed, the degree of the so-called large change is as follows: the designer and other related personnel think that the large change will cause the change of the indoor flow field, that is, the change of the representative flow field for calculating the CRI will cause the change of the CRI. Therefore, a plurality of representative flow fields can be arranged according to the great change of the heat productivity of the indoor heat source, and any representative flow field has the corresponding CRI distribution.
The beneficial effects of setting a plurality of representative flow fields in step S3 and step S4 are:
in practical situations, the indoor flow field is mainly divided into two cases: a forced convection dominant flow field and a natural convection dominant flow field. However, the two flow fields are not constantly kept, and both have their respective influence factors, such as the magnitude and direction of the air volume or the air speed in the forced convection current leading flow field can be correspondingly adjusted according to the needs, and the flow field influenced by the buoyancy effect can be changed after the heat productivity of the heat source in the natural convection current field leading flow field is greatly changed. Based on the situation, the invention provides that a plurality of representative flow fields are arranged according to different indoor conditions, so that a plurality of groups of CRI distributions are obtained through calculation. Meanwhile, the multi-group CRI distribution also provides a good judgment basis for the designer in the design stage.
In step S5, a representative flow field is calculated using convection-radiation coupling simulation.
In order to better explain the present invention, the concept of standard condition flow field will be introduced. The purpose of an air conditioning system is to maintain the indoor temperature within a certain range. When the indoor temperature is in a satisfactory state (namely the design temperature of the building interior), no load exists, and cold and hot air does not need to be fed, the indoor flow field is completely isothermal, the condition is defined as a first standard condition, the temperature is called as neutral temperature, and the neutral temperature is the design temperature of the building interior. When a heat (cold) load exists in a room and the air conditioning system is used as a corresponding heat sink (heat source), the flow field is influenced by buoyancy generated by space temperature distribution and air supply of the air conditioner, and at the moment, the flow field is different from a first standard condition. The velocity field used for measuring the temperature field is not the flow field under the first standard condition, but includes the influence of the heat source or the heat sink on the flow field, and the flow field is defined as a second standard flow field, namely a representative flow field, and the temperature of the second standard flow field is kept at a neutral temperature.
The method of calculating the representative flow field, i.e., the second standard flow field, is: and inputting the boundary conditions and the influence of all thermal factors in the chamber into a Computational Fluid Dynamics (CFD) analysis tool, and calculating a representative flow field by using the CFD.
In general, in the energy control equation, the heat transfer term and the air supply term of the enclosure are set as boundary conditions, namely, the convection heat transfer rate and the temperature value at the boundary are used as known boundary conditions. In the invention, the heat transfer item of the enclosure structure is processed in such a way that the enclosure structure is set to be heat-insulating, and a heat source with the same calorific value is arranged in the nearest surface layer of the enclosure structure to transfer heat to air; the air supply item is processed in such a way that neutral temperature air is heated or cooled by a corresponding heat source or heat sink at an air supply port and then is sent into a room; meanwhile, the temperature of the exhaust air is higher than the neutral temperature and is set as a heat sink, and the temperature of the exhaust air is lower than the neutral temperature and is set as a heat source. And boundary conditions corresponding to the enclosure structure, the air supply item and the air exhaust item are processed to be adiabatic or the heating temperature is neutral. It should be noted that there may be more than one indoor heat source term or heat sink term, and the number of the two terms is not necessarily equal, but under certain conditions, the heat gain and the heat loss absolute value are necessarily equal, i.e. the heat balance is achieved.
And step S6, fixing the flow field, setting a single heat source or heat sink, and calculating the temperature distribution by using CFD.
In the CFD simulation, the velocity field and the temperature field are calculated in a coupled manner, but in the present invention, the influence of the heat source changing on the flow field is ignored, that is, it is considered that the buoyancy generated by the density change caused by the temperature change has almost no influence on the air flow, that is, the flow field is fixed to the second standard condition flow field, and the temperature is maintained at a neutral temperature. In a forced convection field, such as a mechanical ventilation or air conditioning system, the flow field can be considered fixed with only small changes in temperature and velocity at the air inlet.
After the flow field is fixed, the indoor temperature field can be assumed to be a linear system. Based on this necessary assumption, the indoor temperature field can be decomposed into a plurality of sub-temperature fields, each of which has only one heat source or sink. When the temperature field of one heat source or heat sink is calculated, the other heat sources or heat sinks are set to have no influence on the temperature distribution in the whole room, for example, when the temperature field of a human body is calculated, the neutral temperature is set to be sent by the air supply outlet. The influence of the thermal factor, such as calorific value and temperature, is input to the computational fluid dynamics analysis tool CFD to obtain a temperature distribution of the thermal factor.
The arithmetic expression of the linear behavior of the temperature field is derived mathematically as follows:
wherein:
l is differential operator of convection and diffusion;
t (x, y, z): time average temperature of point (x, y, z);
u, V, W: a time-averaged velocity component;
Kt: a turbulent diffusion coefficient of temperature;
H.S.i: an ith heat source or sink;
omega: a temperature field region.
The differential operator L in the formula (1) is composed of a velocity average convection term and a turbulent motion diffusion term, and if the velocity component and the turbulent diffusion coefficient can be assumed to be not influenced by temperature change, L is linear. Even if it is not reasonable to assume that L is linear, this non-linear effect is negligible compared to the convection of the average flow field.
The boundary conditions are expressed as follows:
wherein:
f: the boundary of region Ω;
Tneutralneutral temperature, i.e., the temperature of the air without a heat source or sink.
Formula (2) shows that there is no diffusion heat transfer at the boundary, i.e. the solid boundary is an adiabatic condition, neutral temperature air without heat source or heat sink influence is supplied at the air supply port, and there is no temperature gradient at the air exhaust port.
If the expression for the sub-temperature field corresponding to one heat source or heat sink is defined as equation (3), the boundary condition is equation (2), and L is assumed to be linear, equation (1) can be expressed as equation (4).
L(Ti(x,y,z))＝H.S.i(3)
L(Ts(x,y,z))＝H.S.1+H.S.2+H.S.3+...
＝L(T1(x,y,z))+L(T2(x,y,z))+L(T3(x,y,z))+...
＝L(T1(x,y,z)+T2(x,y,z)+T3(x,y,z)+...) (4)
Equation (4) shows that the temperature field can be decomposed into several sub-temperature fields with only one heat source or heat sink.
Ts＝T1(x,y,z)+T2(x,y,z)+T3(x,y,z)+...
＝∑Ti(x,y,z) (5)
By equations (3) and (5), the temperature field analysis can be divided into two steps:
analyzing the sub-temperature fields for which only one heat source or sink is present;
the total temperature field is the composite of all the sub-temperature fields.
Step S7, obtaining the CRI distribution of the single heat source or heat sink according to the CRI definition and formula.
In a forced convection field and a natural convection field, the ratio of the temperature distribution of a single heat source or heat sink to the temperature distribution of the heat source or heat sink under the condition of completely and uniformly mixing the temperature distribution of the single heat source or heat sink is used for obtaining an index CRI, the CRI is used for analyzing the temperature distribution influence range and size of the heat source or heat sink, the heat source or heat sink can be adjusted according to the temperature distribution influence range and size, after the flow field is fixed, the CRI is a fixed value, the adjusted temperature distribution can be directly calculated by using a CR I definition formula, and CFD simulation does not need to be applied again.
Definition of CRI as described above, the CRI value shows the influence range and influence degree of a single heat source or heat sink. Thermal factor m is at x in case of forced convection fieldiThe CRI value of a point is calculated as follows:
wherein:
xispatial coordinates;
θn: indoor neutral temperature, no physical significance, only used in calculating CRI;
θm,o: thermal factor m heat dissipation QmIndoor temperature during uniform diffusion;
Δθm,o＝θm,o-θn: the temperature difference between the uniform diffusion temperature and the neutral temperature;
θm(xi): calculated CFD with thermal factor m at xiTemperature rise due to point;
Δθm(xi)＝θm(xi)-θn: the temperature difference between the heat dissipation temperature rise and the neutral temperature is obtained by the thermal factor m;
Cp: indoor air specific heat capacity;
ρ: the density of the air;
f: the amount of air supplied.
The CRI distribution is calculated in the case of natural convection, which is a situation where there is no external driving force but there is still motion of the fluid, and the intrinsic force causing this motion of the fluid is the temperature difference.
Because only one heat source is arranged in a representative flow field, and no heat sink is arranged to meet the heat balance, the invention establishes a uniformly distributed virtual heat sink to offset the heat generation of the heat source, and the heat source or the heat sink m is at xiThe CRI of a point is defined as follows:
wherein:
uθm(xi): calculating x by CFD when heat source and heat sink are set simultaneouslyiPoint temperature;
u: the heat sinks are uniformly arranged.
Step S8, whether all heat sources or heat sinks are calculated, if not, the step S6 is returned, and if yes, the step S9 is reached;
step S9, calculating all CRI values, and calculating each sub-temperature field by utilizing the calorific value (or the heat absorption capacity) of the heat source (or the heat sink) according to the CRI definition formula;
and step S10, whether the temperature fields under all the representative flow fields are decoupled is finished, if so, the step S11 is carried out, and if not, the step S6 is returned.
And step S11, completing temperature distribution analysis, wherein the total temperature field is the linear synthesis of all the sub-temperature fields.
When calculating the CRI, first all heat sources or sinks in the space, such as heat transfer of the building envelope, air supply of an air conditioning system, heat generation of human body and equipment, etc., are determined. After determining the heat source or the heat sink, calculating a representative flow field containing the influence of the heat source or the heat sink by using CFD (notably, because the convective heat transfer rate of the wall surface is related to the radiant heat transfer between the wall surfaces and the heat conduction height of the wall, the invention performs convective and radiative coupling simulation), fixing the flow field, setting a single heat source, calculating the temperature distribution under the influence of the heat source by using CFD again, and then calculating the CRI distribution of the heat source by using the definition of CRI.
In this embodiment, a specific room model is used for explanation. As shown in fig. 2, assuming a room model of 3.6m long, 2.2 m wide and 2.7 m high, the air outlet is provided above the window and the air supply outlet is provided on the opposite wall. The room heat load comes mainly from windows, exterior walls and internal heat generators. The supply air is cooled by the air conditioning system, and the ceiling is also cooled to absorb heat, so that the outside of the wall has good heat insulation performance.
The reference numerals and associated parameters in fig. 2 are illustrated as follows:
1: cooling ceiling (3.6m by 1.8m) with a cooling load of 232.6W;
2: the air supply outlet (0.2m by 0.08m), the wind speed is 1.44m/s, and the temperature difference with the exhaust air is-10 ℃;
3: a partition wall;
4: an internal heat source with a heat load of 116.3W;
5: a symmetry plane, which is set at a symmetric position of the room (the CRI distribution on the symmetry plane is taken as an example in this example);
6: outer wall, heat load 34.89W;
7: outer window (1.2m by 1.4m), heat load 360.53W;
8: the air outlet (2.0m 0.05m) and the air exhaust speed is 0.26 m/s.
The flow field and the temperature field were numerically simulated by coupled simulation of the convection heat exchange and the radiant heat exchange, as shown in fig. 3(a) to 3 (f). For the temperature boundary condition of the wall surface, the heat balance problem among convection heat exchange, radiation heat exchange and wall surface heat conduction is considered. And estimating the convective heat transfer rate by using a given convective heat transfer coefficient according to the temperature difference between the wall surface and the first grid point. All heat loads and air conditioning factors were included in the analysis of the flow field. The results of the numerical simulation are very consistent with the experimental results of the full-scale room model.
The surface temperature and the convective heat transfer rate of each solid surface were obtained from coupled simulations of convective heat transfer and radiative heat transfer, all values are listed in table 1. The temperature difference from the neutral condition, i.e., the temperature difference from the discharge air temperature, is shown in fig. 3. The air supply enters horizontally, descends to the floor due to the negative buoyancy of the cool air, and the air stream rising along the opposite wall and window is heated. The hot air around the window is partly discharged through the exhaust opening and partly cooled by the ceiling surface. Air near the indoor thermal load is heated significantly and the ambient temperature is higher. The surface of the partition wall is heated by radiation from the window and the exterior wall, and there is some convective heat transfer.
TABLE 1
The sub-temperature fields of each heat source or heat sink with a fixed flow field were calculated according to equation (3) and equation (2) for the boundary conditions, and each heat source or heat sink is shown in table 1. In the room model used here, there is only one supply port and one exhaust port, and since the room air is supplied only by one supply port, the sub-temperature fields corresponding to the heat sinks of the supply ports are uniform.
The resulting sub-temperature fields are normalized by the representative temperature difference according to the CRI definition, and then the CRI value is obtained.
Fig. 4(a) to 4(e) show the CRI distribution of each heat source or sink, as specified below:
(a) CRI of outer window
As shown in FIG. 4(a), the contribution ratio of the window is between 0.5 and 0.7, and a region CRI just above the window is larger than 1. However, in most spaces its value is low, which means that the air outlet above the window can efficiently discharge heat from the window. Near the supply air outlet, the CRI is very low with little effect.
(b) CRI of exterior wall
As shown in FIG. 4(b), the contribution rate of the outer wall is between 0.8 and 1.0. Compared with a window, the heat from the outer wall is better diffused and is not discharged with high efficiency. There is an area directly above the window with a CRI greater than 1, however, this trend is weak compared to the case of windows. Near the supply air opening, the CRI value is very low, similar to the window case.
(c) CRI of internal thermal load
As shown in FIG. 4(c), the contribution rate of the internal heat load is 0.8 to 1.2. In contrast to the first two cases, the heat generated by the indoor heat load is not efficiently rejected, and there is a region just above the internal heat load having a CRI greater than 1.
(d) CRI for partition walls and floors
The partition wall and the floor are both heat-insulated, however, the radiant heat exchange from the heated wall causes convection heat exchange of the walls, and as shown in fig. 4(d), the contribution rate of the partition wall and the floor is between 0.8 and 1.0. Near the supply air opening, the CRI value becomes as low as in the first three cases.
(e) CRI for cooling ceiling
As shown in FIG. 4(e), the contribution ratio of the cooling ceiling is between-0.8 and-1.2. The cooling ceiling has a large influence on the whole space and can effectively absorb heat from indoor air.
(f) CRI of air supply outlet
The air supply is uniformly distributed in the whole space, and the CRI value of the air supply is constant to 1.
The above description is for the purpose of illustrating embodiments of the invention and is not intended to limit the invention, and it will be apparent to those skilled in the art that any modification, equivalent replacement, or improvement made without departing from the spirit and principle of the invention shall fall within the protection scope of the invention.
Claims (10)
1. A method for decoupling a building indoor temperature field is characterized in that: the method comprises the following steps:
step S1, determining all heat factors in the building room;
step S2, determining the type of the indoor flow field, and if the type is the forced convection main flow field, entering step S3; if the natural convection main flow field is present, the step S4 is executed;
step S3, setting at least one representative forced convection field according to the air supply volume or the air speed and the direction according to different air speeds or air volume requirements in the building, wherein the indoor flow field is a forced convection leading flow field;
step S4, setting at least one representative natural convection field if the indoor flow field is changed due to the change of the heat productivity of the indoor heat source, wherein the indoor flow field is a natural convection leading flow field;
step S5, calculating a representative flow field by using convection-radiation coupling simulation;
step S6, fixing the representative flow field, setting a single thermal factor, and calculating the temperature distribution of each thermal factor by using CFD;
step S7, calculating the CRI value of the single thermal factor;
step S8, whether the CRI values of all thermal factors are calculated completely, if not, the step S6 is returned, and if yes, the step S9 is reached;
step S9, calculating each sub-temperature field by utilizing the calorific value or the heat absorption capacity of the thermal factor according to the CRI definition formula;
step S10, whether the temperature fields under all the representative flow fields are decoupled is finished, if yes, the step S11 is carried out, and if not, the step S6 is returned;
and step S11, decoupling the temperature fields, wherein the total temperature field is the linear synthesis of all the sub temperature fields.
2. A method of decoupling a building indoor temperature field according to claim 1, characterized by: the thermal factors include a heat source term and a heat sink term.
3. A method of decoupling a building indoor temperature field according to claim 2, characterized by: the heat source term transfers heat to the air in the building room, and the heat sink term absorbs heat from the air in the building room.
4. A method of decoupling a building indoor temperature field according to claim 1, characterized by: the representative flow field is defined as: all thermal factor effects are included and the temperature is maintained at a neutral temperature.
5. A method of decoupling a building indoor temperature field according to claim 4, characterized by: the neutral temperature is the design temperature of the building indoor.
6. The method of decoupling a building indoor temperature field of claim 5, wherein: a representative flow field is calculated as: and inputting the boundary conditions in the building room and the influence of all thermal factors in the building room into a Computational Fluid Dynamics (CFD) analysis tool, and calculating by using the CFD analysis tool.
7. The method of decoupling a building indoor temperature field of claim 6, wherein: the enclosure structure is heat-insulated, and a heat source with the same calorific value is arranged in the nearest surface layer of the enclosure structure to transfer heat to air; the air supply item is processed in such a way that neutral temperature air is heated or cooled by a corresponding heat source or heat sink at an air supply port and then is sent into a room; setting the temperature of the exhaust item higher than the neutral temperature as a heat sink and lower than the neutral temperature as a heat source; and boundary conditions corresponding to the enclosure structure, the air supply item and the air exhaust item are processed to be adiabatic or the heating temperature is neutral.
8. A method of decoupling a building indoor temperature field according to claim 1, characterized by: the way to calculate the temperature distribution of a single thermal factor is: and inputting the influence of the single thermal factor into a computational fluid dynamics analysis tool CFD, and setting the rest thermal factors as adiabatic or exothermic temperature as neutral temperature.
9. A method of decoupling a building indoor temperature field according to claim 1, characterized by: in forced convection fields, the thermal factor m is at xiThe CRI value of a point is calculated by the formula:
wherein:
xispatial coordinates;
θn: indoor neutral temperature;
θm,o: thermal factor m heat dissipation QmIndoor temperature during uniform diffusion;
Δθm,o＝θm,o-θn: the temperature difference between the uniform diffusion temperature and the neutral temperature;
θm(xi): thermal factor m is in xiTemperature rise due to point;
Δθm(xi)＝θm(xi)-θn: the temperature difference between the heat dissipation temperature rise and the neutral temperature is obtained by the thermal factor m;
Cp: indoor air specific heat capacity;
ρ: the density of the air;
f: the amount of air supplied.
10. A method of decoupling a building indoor temperature field according to claim 1, characterized by: in natural convection fields, the thermal factor m is at xiThe CRI value of a point is calculated by the formula:
wherein:
uθm(xi): calculating x by CFD when heat source and heat sink are set simultaneouslyiPoint temperature;
u: heat sinks are uniformly arranged;
θn: indoor neutral temperature;
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911065325.7A CN110826221A (en) | 2019-11-04 | 2019-11-04 | Method for decoupling indoor temperature field of building |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911065325.7A CN110826221A (en) | 2019-11-04 | 2019-11-04 | Method for decoupling indoor temperature field of building |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN110826221A true CN110826221A (en) | 2020-02-21 |
Family
ID=69552296
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201911065325.7A Pending CN110826221A (en) | 2019-11-04 | 2019-11-04 | Method for decoupling indoor temperature field of building |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110826221A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111709199A (en) * | 2020-06-28 | 2020-09-25 | 北京工业大学 | Method for measuring heat productivity of equipment |
| CN112464408A (en) * | 2020-11-27 | 2021-03-09 | 四川长虹空调有限公司 | Simulation evaluation method for uniformity of air volume and room temperature field of through-flow air duct air conditioner on-hook |
| CN112666213A (en) * | 2020-12-21 | 2021-04-16 | 昆明理工大学 | Method for detecting temperature field uniformity in gas-liquid two-phase mixing process |
| CN113344286A (en) * | 2021-06-28 | 2021-09-03 | 北京工业大学 | Method and device for predicting indoor temperature distribution |
| CN113344287A (en) * | 2021-06-28 | 2021-09-03 | 北京工业大学 | Indoor temperature distribution prediction system |
| CN116305476A (en) * | 2023-03-24 | 2023-06-23 | 天津大学 | Rapid prediction method for space-time dynamic distribution of indoor temperature field |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106354977A (en) * | 2016-09-29 | 2017-01-25 | 南京工业大学 | Method for analyzing indoor thermal environment by using CFD (computational fluid dynamics) model |
-
2019
- 2019-11-04 CN CN201911065325.7A patent/CN110826221A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106354977A (en) * | 2016-09-29 | 2017-01-25 | 南京工业大学 | Method for analyzing indoor thermal environment by using CFD (computational fluid dynamics) model |
Non-Patent Citations (1)
| Title |
|---|
| WEIRONG ZHANG等: "Building energy simulation considering spatial temperature distribution for nonuniform indoor environment", 《BUILDING AND ENVIRONMENT》, pages 89 - 96 * |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111709199A (en) * | 2020-06-28 | 2020-09-25 | 北京工业大学 | Method for measuring heat productivity of equipment |
| CN111709199B (en) * | 2020-06-28 | 2024-01-26 | 北京工业大学 | Method for measuring heating value of equipment |
| CN112464408A (en) * | 2020-11-27 | 2021-03-09 | 四川长虹空调有限公司 | Simulation evaluation method for uniformity of air volume and room temperature field of through-flow air duct air conditioner on-hook |
| CN112666213A (en) * | 2020-12-21 | 2021-04-16 | 昆明理工大学 | Method for detecting temperature field uniformity in gas-liquid two-phase mixing process |
| CN112666213B (en) * | 2020-12-21 | 2023-04-11 | 昆明理工大学 | Method for detecting temperature field uniformity in gas-liquid two-phase mixing process |
| CN113344286A (en) * | 2021-06-28 | 2021-09-03 | 北京工业大学 | Method and device for predicting indoor temperature distribution |
| CN113344287A (en) * | 2021-06-28 | 2021-09-03 | 北京工业大学 | Indoor temperature distribution prediction system |
| CN116305476A (en) * | 2023-03-24 | 2023-06-23 | 天津大学 | Rapid prediction method for space-time dynamic distribution of indoor temperature field |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110826221A (en) | Method for decoupling indoor temperature field of building | |
| CN103049612B (en) | Building indoor environment optimization method based on model order reduction technology | |
| Zhai et al. | Inverse design methods for indoor ventilation systems using CFD-based multi-objective genetic algorithm | |
| Vangilder et al. | Real-Time Prediction of Rack-Cooling Performance. | |
| CN104633856A (en) | Method for controlling artificial environment by combining CFD numerical simulation and BP neural network | |
| CN111985026B (en) | High-efficiency natural ventilation design method for building based on thermal stratification height | |
| CN114877502B (en) | Distributed model-based temperature and humidity control method and system for multi-zone air conditioning system | |
| Vidhyashankar et al. | Modelling spatial variations in thermal comfort in indoor open-plan spaces using a whole-building simulation tool | |
| Yan et al. | Comparison of space cooling/heating load under non-uniform indoor environment with convective heat gain/loss from envelope | |
| Yang et al. | Control strategy optimization for energy efficiency and comfort management in HVAC systems | |
| Yang et al. | Hybrid artificial neural network− genetic algorithm technique for condensing temperature control of air-cooled chillers | |
| Goyal et al. | Modeling thermal dynamics in multi-zone buildings | |
| JP7345686B2 (en) | Systems and methods for controlling the operation of HVAC (heating, ventilation, air conditioning) systems | |
| CN111444646B (en) | Method for researching influence of building space size on air temperature vertical distribution mode | |
| Salom et al. | Dynamic modelling of data centre whitespaces, validation with collected measurements | |
| Kim et al. | Model-based predictive control for buildings with decoupling and reduced-order modeling | |
| Shah et al. | Dynamic modelling and multivariable control of buildings climate by using sliding mode control | |
| Lastovets et al. | Multi-nodal model for predicting vertical temperature profile in the stratum-ventilated large retail facility | |
| Rastegar-Moghadam et al. | Thermal modeling of an office environment with variable volume air condition system using zonal method for control system applications | |
| Phan et al. | Improving cooling efficiency by using mixed tiles to control airflow uniformity of perforated tiles in a data center model | |
| Macabutas et al. | Air Temperature Analysis of a Residential House Using Soliworks Flow Simulation | |
| Zhao et al. | Optimal Design Of An Indoor Environment Using An RNG K-Ε Adjoint Turbulence Model | |
| Chowdhury et al. | Analysis of building systems performance through integrated computation fluid dynamics technique | |
| JPH10281533A (en) | Prediction method of room temperature in floor blowing air conditioning method | |
| US5899080A (en) | Air conditioning method and system |
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 |