CN107301276A - Calculation method of convective heat transfer load of air-supply layered air conditioner with nozzles in large space - Google Patents

Abstract

The invention relates to a method for calculating convection heat transfer load of a large-space-nozzle air supply layered air conditioner, which comprises the steps of establishing a Block-Gebhart model to calculate the convection heat transfer load of the large-space-nozzle air supply layered air conditioner, verifying the convection heat transfer load by using a reduced scale model experiment result, analyzing and discussing key factors influencing the convection heat transfer load, and making a line calculation chart. The invention can optimize the jet flow model, and the obtained optimized Block-Gebhart extended model can deeply analyze the change condition of the indoor thermal environment of the large-space layered air conditioner, and on the basis, the coupling calculation of the vertical air temperature and the wall surface temperature of the large space can be carried out, so that the calculation method of the convection heat transfer load of the layered air conditioner which is primarily suitable for air supply at the nozzle side is obtained by exploration.

Description

Calculation method of convective heat transfer load of air-supply layered air conditioner with nozzles in large space

technical field

The invention relates to an air-conditioning load calculation technology, in particular to a method for calculating the convective heat transfer load of a large-space nozzle air-supply layered air conditioner.

Background technique

The thermal environment of large-space buildings under stratified air-conditioning, indoor air vertical temperature stratification, obvious gradient, large temperature difference between top and bottom, and roof wall temperature distribution lead to different calculation methods for large-space stratified air-conditioning loads and ordinary rooms. That is, the complex airflow organization in a large space, outdoor environment changes, and indoor heat source distribution will all lead to changes in indoor thermal environment state parameters and changes in convective heat transfer. Therefore, the calculation of convective heat transfer load has always been a difficult problem for designers.

At present, the calculation method of stratified air-conditioning load in large-space buildings adopts the method mentioned in the "Practical Heating and Air-Conditioning Design Manual" edited by Professor Lu Yaoqing. , indoor heat source load, fresh air or infiltration wind load, etc.) and the load formed by the radiation transfer heat and convective transfer heat transferred from the non-air-conditioned area to the air-conditioned area, and through model experiments and field measurements, the factors that affect the heat transfer load and Calculation method. The specific calculation method is as follows: (1) The load of the conventional air-conditioning area is calculated by the traditional whole room air-conditioning load calculation method; (2) The radiation transfer heat load is calculated by the cooling load coefficient method: firstly, by calculating the radiation transfer heat from the non-air-conditioning area to the floor of the air-conditioning area, Then multiply by the heat gain coefficient C ₁ (generally 1.3) to obtain the radiation transfer heat from the non-air-conditioned area to the air-conditioned area. Then the radiation transfer heat from the non-air-conditioned area to the air-conditioning area is multiplied by the cooling load coefficient C ₂ (the value range is 0.45-0.72, generally 0.5) to obtain the radiation transfer load; (3) The convective heat transfer load is calculated through the Multiple tests and on-site measurements, regression fitting of the results into calculation curves and popularization and application to large-space buildings will form the key factors of convective heat transfer load—propelled by the three functions of nozzle air supply, internal heat source, and exhaust air. The airflow movement in the air-conditioned area and the non-air-conditioned area and the energy transfer it carries are simplified as the comparison relationship between the heat intensity of the air-conditioned area, the heat intensity of the non-air-conditioned area, and the heat dissipation. The convective heat transfer load can be obtained by looking up the map.

From the above, it can be seen that the convective heat transfer load is an important part of the cooling load of the stratified air conditioner. Since the degree of research on the calculation method of the above-mentioned convective heat transfer load was limited by the thermal environment of large-space buildings at that time, many empirical values and steam turbines were used. The actual measurement data of the tall factory building, and the experimental and actual measurement conditions are single. Based on the current research on the indoor thermal environment of large-space buildings, the calculation methods at that time had certain defects and deficiencies.

Contents of the invention

The present invention is aimed at the problem that the current calculation method of stratified air-conditioning load in large-space buildings is limited by the current data, and proposes a method for calculating the convective heat transfer load of air-supply stratified air-conditioning in large-space nozzles. On the basis of experiments, it is proposed and established The Block-Gebhart model is used to calculate the theoretical calculation model of convective heat transfer load under steady heat transfer. In the invention, the results of scaled-scale model experiments are used to verify the correctness and reliability of the theoretical model, and then the mathematical model is used to analyze the main factors affecting the convective heat transfer load. The line diagram for calculating the convective heat transfer load was obtained and verified by experiments and supplemented by on-site measurements. Later, combined with the theoretical calculation model of the radiation transfer load, the radiation transfer load of the stratified air conditioner under the air supply from the nozzle was studied, and the system was initially applicable to the nozzle side. Stratified air conditioning calculation method for supply air.

The technical solution of the present invention is: a method for calculating the convective heat transfer load of air-supply stratified air conditioners in large spaces, which specifically includes the following steps:

1) Analyze the convective heat transfer load and establish the Block-Gebhart model: under the large-space indoor nozzle air supply system, the installation height of the nozzle is the layered height, which is the interface between the non-air-conditioned area and the air-conditioned area, and the upper part is the non-air-conditioned area. The bottom is the air-conditioning area. The convective heat transfer load includes the heat from the non-air-conditioning area to the air-conditioning area and the temperature difference heat transfer on the interface. The Block model divides the indoor environment into several control areas in the vertical direction, and the prediction calculation is large. Indoor vertical temperature distribution of space buildings, using the Gebhart absorption coefficient method, comprehensively considering the heat conduction, convection and radiation coupled heat transfer jointly affected by the outdoor environment heat transfer, indoor surface radiation heat transfer and indoor heat source radiation, to solve the indoor wall surface temperature distribution, And use this as the boundary condition for the calculation of the Block model, and use the Block-Gebhart model to solve the convective heat transfer load synchronously;

2) Experimental verification of the Block-Gebhart model to solve the convective heat transfer load: Under the gaseous scale model test bench nozzle air supply system, conduct experiments on the temperature field and convective transfer heat load in a large space, verify the model, and analyze the impact of convective heat For the key factors of transfer load, use the relationship between heat intensity ratio, heat removal ratio, and dimensionless convective heat transfer load between non-air-conditioned area and air-conditioned area to draw a line calculation diagram, simplify the calculation of convective heat transfer load, and use it for practical use.

The Block model in the step 1) adopts a Block model based on multi-zone heat and mass balance, which is used to predict the indoor vertical temperature distribution of large space buildings;

Assuming that the indoor environment is uniformly distributed in the horizontal direction except for the area affected by the air-conditioning jet, the concept of the lumped parameter method is used to analyze the mass flow and energy transfer for each control mainstream area, and the mass and energy balance equations are established respectively, and then Initially set the air temperature in the mainstream area of each control area and its wall temperature, after a series of iterative calculations, finally calculate the temperature of each control area within the allowable error, so as to obtain the indoor vertical temperature distribution (T ₁ , T ₂ , T ₃ ... T _n ), n is the total number of control areas divided in the vertical direction; the installation height of the spout is taken as the layered height, which is the interface between the non-air-conditioned area and the air-conditioned area, that is, the 1-F layer is the air-conditioned area, The area above the F floor is a non-air-conditioned area, and the calculation formula for the convective heat transfer load is as follows:

q _d ＝C _p M _cF (T _F+1 -T _F )+C _BF A _BF (T _F+1 -T _F )

In the formula: q _d is the convective heat transfer load from the non-air-conditioned area to the air-conditioned area, in W; C _P is the specific heat of air at constant pressure, in kJ/(kg °C), and the value for air is 1.01; M _CF is non-air-conditioned The air quality net flow rate from the air-conditioned area to the air-conditioned area, in kg/s; T _F+1 , T _F are the air temperatures in the lowest layer of the non-air-conditioned area and the highest layer of the air-conditioned area, respectively, in °C; C _BF is the air-conditioning area from the non-air-conditioned area Temperature difference heat transfer coefficient, unit W/(m ² ·℃); A _BF is the layered interface area between non-air-conditioned area and air-conditioned area, unit m ² .

The step 1) using the Block-Gebhart model to synchronously solve the convective heat transfer load specifically includes the following steps:

A: Optimize the multi-jet calculation model of the nozzle, establish the wall flow model and the heat and mass exchange model between multiple regions;

B: Use the Block boundary condition - wall temperature to solve the convection-radiation coupling heat transfer: according to the geometric conditions of the building, divide it into walls, and solve the angle coefficient and Gebhart absorption coefficient between the walls. By assuming the initial temperature distribution of the wall, according to the indoor air The temperature distribution, outdoor environmental parameters, thermal parameters of the enclosure structure and indoor heat sources are used as boundary conditions to calculate the heat conduction and radiation. Finally, according to the coupled heat balance equation, the temperature distribution of the wall surface can be obtained by simultaneous solution;

C: Establish the air volume and energy balance equations according to the Block-Gebhart model; after completing the calculation of each regional sub-model, establish the mass balance and energy balance equations of each Block region, and then iteratively calculate and solve the indoor air vertical temperature by the simultaneous equations Distribution, wall temperature distribution and convective heat transfer load, for any block mainstream area, establish an equation;

D: Block-Gebhart model synchronous solution:

(1) Assuming the initial temperature, assuming the initial air vertical temperature distribution and wall temperature distribution, the initial wall temperature distribution is input into the Gebhart model wall heat conduction, convection, and radiation coupling heat transfer equation, and the air vertical temperature result calculated by the Block model is used as the boundary condition. The initial air vertical temperature distribution is input into the Block heat and mass balance equation. The model uses the wall temperature result calculated by the Gebhart model as the boundary condition for calculation, and the two model parameters are mutually input;

(2) Iterative calculation: compare the indoor air temperature and wall temperature distribution obtained in the second step with the initial value of the first step, and when the error between the two does not satisfy <10 ^-6 , assign it to the initial value and return The first step starts to repeat the calculation;

(3) Solve the temperature distribution of the wall surface and the vertical temperature distribution of the room in such a loop iteratively. When the relative error of the two calculation results of the previous and subsequent calculations is both <10 ^-6 , the calculation results of the last two calculations of the indoor air temperature distribution and the wall temperature distribution are considered is the solution of the problem, and take the net flow on the stratified interface calculated by the balance equations at this time to calculate the convective heat transfer load from the non-air-conditioned area to the air-conditioned area; according to the obtained inner wall temperature, indoor vertical temperature and non-air-conditioned area The net flow of air on the layer interface with the air-conditioning zone, and then according to the calculation formula of the convective heat transfer load, the convective heat transfer load of the layered air conditioner is obtained.

The beneficial effect of the present invention is that: the method for calculating the convective heat transfer load of the air-supply layered air conditioner in a large space in the present invention can optimize the jet flow model, and the optimized Block-Gebhart extended model can deeply analyze the indoor heat of the large space layered air conditioner. According to the environmental changes, on this basis, the coupled calculation of the vertical air temperature and the wall temperature of the large space can be carried out, and the calculation method of the convective heat transfer load of the layered air conditioner suitable for the air supply at the nozzle side can be explored and preliminarily obtained.

Description of drawings

Fig. 1 is a technical roadmap of the method for calculating the convective heat transfer load of the air-supply layered air conditioner with large space nozzles of the present invention;

Fig. 2 is a wall flow model figure of the present invention;

Fig. 3 is a schematic diagram of the indoor Block model of the present invention;

Fig. 4 is the relationship diagram between the thermal intensity ratio and the convective heat transfer load of the non-air-conditioned area and the air-conditioned area of the present invention;

Fig. 5 is a verification diagram of the scale model line calculation diagram of the present invention.

detailed description

As shown in Figure 1, the technical roadmap for calculating the convective heat transfer load of air-supply layered air conditioners with large space nozzles, the method specifically includes the following steps:

Step 1: Analyze the cause of the convective heat transfer load;

In the large-space indoor nozzle air supply system, the installation height of the nozzle is the layered height, which is the interface between the non-air-conditioned area and the air-conditioned area, and the upper part is the non-air-conditioned area. Part of the heat in the area is transferred to the air-conditioned area, and all of it immediately becomes the cooling load of the air-conditioned area. The root cause of convective heat transfer is mainly attributed to the following two points in the non-air-conditioned area and the air-conditioned area: one is the temperature difference between the two areas, and the other is the air flow between the two areas, both of which are indispensable. According to the above analysis, the convective heat transfer load includes the heat brought by the flow from the non-air-conditioned area to the air-conditioned area and the temperature difference heat transfer on the interface. Therefore, the flow and temperature difference of indoor airflow determine the occurrence of convective heat transfer and the amount of heat transferred by convection heat. The factors that usually affect the flow of airflow and temperature difference are mainly as follows: air supply and return air volume in air conditioning area, air supply in air conditioning area Temperature, exhaust air volume of non-air-conditioned area, heat gain ratio of non-air-conditioned area to air-conditioned area. In addition, in some architectural forms, air inlets in non-air-conditioned areas and air outlets in other areas will also affect the indoor airflow. This invention only analyzes the four main factors listed above.

Step 2: Use the Block model based on multi-zone heat and mass balance to predict the indoor vertical temperature distribution of large-space buildings;

When using the Block model to determine the indoor air temperature distribution, the wall temperature distribution will affect the air temperature distribution, so the determination method of the wall temperature is very important. In this paper, the heat conduction, convection, and radiation coupled heat transfer method, which considers the joint effects of outdoor environment heat transfer, indoor surface radiation heat transfer, and indoor heat source radiation, namely the Gebhart absorption coefficient method, is used to solve the indoor wall temperature distribution, and use it as The boundary conditions calculated by the Block model, using the Block-Gebhart model synchronous solution method to study the indoor thermal environment of large space buildings. Since the internal surface temperature and the indoor air temperature are coupled to each other, iterative calculations are required separately, and the following parameters are calculated by synchronous solution to calculate the convective heat transfer load:

(1) The temperature of the inner wall surface of each area in the room;

(2) Air temperature distribution in each area of the room;

(3) Mass flow between the regions.

When the Block-Gebhart model analyzes the indoor thermal environment under the large-space nozzle air supply, it is assumed that the indoor environment is uniformly distributed in the horizontal direction except for the area affected by the air-conditioning jet flow. Using the concept of the lumped parameter method, for each control mainstream area Analyze mass flow and energy transfer, and establish mass and energy balance equations, respectively. Then, the air temperature in the mainstream area and the wall surface temperature of each control area are initially set, and after a series of iterative calculations, the temperature of each control area within the allowable error is finally calculated, so as to obtain the indoor vertical temperature distribution (T ₁ , T ₂ , T ₃ · · · T _n ).

According to the above analysis, the convective heat transfer load includes the heat brought by the flow from the non-air-conditioned area to the air-conditioned area and the heat transfer of the temperature difference on the interface. The interface with the air-conditioned area, that is, floors 1-4 are air-conditioned areas, and floors 5 and above are non-air-conditioned areas. Therefore, the convective heat transfer load calculation formula is as follows:

q _d ＝C _p M _c5-4 (T ₅ -T ₄ )+C _B5-4 A _B5-4 (T ₅ -T ₄ ) (1)

In the formula: q _d ——convective heat transfer load from non-air-conditioned area to air-conditioned area, unit W;

C _P - Specific heat of air at constant pressure, unit kJ/(kg °C), the value for air is 1.01;

M _{C5-4 ——The} net flow rate of air quality from the non-air-conditioned area to the air-conditioned area, unit kg/s;

T ₅ , T ₄ ——The air temperature of the lowest layer in the non-air-conditioned area and the highest layer in the air-conditioned area, in °C;

C _B5-4 - heat transfer coefficient of temperature difference between non-air-conditioned area and air-conditioned area, unit W/(m ² °C);

A _{B5-4 ——The} layered interface area between non-air-conditioned area and air-conditioned area, unit m ² .

In order to calculate the indoor vertical temperature distribution of large-space buildings, the Block model divides the indoor environment into several control areas in the vertical direction. If the influence of natural ventilation and indoor heat sources is not considered, the indoor airflow organization can be summarized into three airflows: wall flow, air-conditioning jet flow, and indoor main airflow formed by the temperature difference in the vertical direction. It is assumed that the indoor thermal environment is one of these three jets. The heat and mass exchange between them is the result of the joint action. Corresponding to these three airflows, three sub-models are included in the Block model to describe the heat and mass movement: wall flow model, air-conditioning jet model, and interregional heat and mass exchange model. According to the regional heat and mass balance analysis method, the Block model divides the indoor vertical direction into several areas, as shown in Figure 2. By describing the air heat and mass transfer process between each block area, the mass balance and energy balance equations are established, and the temperature of each block area is solved to obtain the indoor vertical temperature distribution.

Step 3: Optimizing the calculation model of multiple jets at the nozzle; including single jet trajectory, non-isothermal jet axial velocity, temperature attenuation formula, superposition of multiple jets, entrainment characteristics, etc.

Step 4: Establish a wall flow model and a multi-region heat and mass exchange model; the inner wall of the enclosure structure is affected by the outdoor ambient temperature and the indoor environment, and the area near the inner surface will generate an upward or downward air flow along the wall. When the wall surface is hot relative to the indoor air temperature, the flow direction of the airflow is upward, and the calculation of the wall air flow must start from the bottom block in the room; when the wall surface is cold relative to the indoor air temperature, the airflow The flow direction is downward, and the calculation must start from the topmost Block and calculate downward layer by layer. According to the different thermal parameters such as the orientation and material of the walls around the enclosure structure, the temperature of the inner wall surface will be different. Therefore, the wall surface is divided into K different wall surfaces from the bottom to the top according to the corresponding Block for processing. Figure 3 shows the wall flow model diagram, taking summer as an example. The wall is a hot wall, and the temperature of the wall is higher than that of the surrounding air. The convective heat transfer between the wall and the indoor air causes the outflow M _OUT (I,K) of each layer (Block I) to merge into an airflow along the wall, and the air flows along the wall. In the upward direction, the wall flow starts from the lowest Block 1 and starts to calculate layer by layer. The mass outflow air (flow rate M _OUT (I,K) and temperature T(I)) produced by any Block I in the middle layer and the mixed air flow from the lower Block (I-1) (flow rate is M _MD (I-1,K), the temperature is T _M (I-1,K-1)) meet and synthesize, and the mass flow rate is M _M (I,K), and the temperature is T _M (I,K). The ascending synthetic flow continues to flow upwards along the hot wall surface, and then according to the relationship between the temperature of the synthetic flow T _M (I, K) and the air temperature of Block I and Block (I+1), it is judged that part or all of it flows back to Block I, The rest of the traffic flows into the upper Block (I+1) until it all flows into the topmost BlockN.

The air temperature near the wall can be analyzed according to the boundary layer theory, and the air temperature of the boundary layer along the K wall of Block I is calculated by the following formula.

T _D (I,K)＝0.75T(I)+0.25T _W (I,K) (2)

In the formula, K is the serial number of the wall, T _D (I, K) is the average air temperature in the boundary layer of Block I along the K wall, T (I) is the air temperature of Block I in °C, T _W (I, K) is the wall The temperature of K°C.

The equilibrium equation of mass flow heat transfer and natural convection heat transfer near the wall is established as follows:

C _P M _OUT (I,K)[T _D (I,K)-T(I)]＝α _C (I,K)A _W (I,K)[T _W (I,K)-T(I )] (3)

In the formula, M _OUT (I,K) is the mass outflow of Block I along the K wall, kg/s, α _C (I,K) is the convective heat release coefficient of the wall K, W/(m ² °C), A _W (I, K) is the area of the wall K of Block I, m ² , and C _P is the specific heat of air at constant pressure, W/(m ² ·℃).

The amount of natural convective heat transfer between the wall and the air is equal to the energy carried by the flow handled by the boundary layer.

When the airflow is synthesized, the air volume and heat balance equation of the combined upflow between the wall surface and the air are as follows:

M _OUT (I,K)T(I)+M _MD (I-1,K-1)T _M (I-1,K-1)＝M _M (I,K)T _M (I,K) ( 5)

M _M (I,K)＝M _OUT (I,K)+M _MD (I-1,K-1) (6)

Temperature T _M (I,K) of the mixed gas flow:

And the air flow M _MD (N, K) of the mixed air flow from the uppermost Block (N) in the upflow of the hot wall surface = 0, and the air flow M _MD (0, K) of the mixed air flow from the bottom Block (0) K) = 0. (When I=1, there is no flow from the previous layer I-1 to the I layer, so M _MD (0,K)=0; when I=N, there is no flow from the I layer to the next layer I+1 amount, so M _MD (N,K)=0)

When the synthetic upwelling flow of each layer is specifically distributed to the next layer, the distribution process of the mixed air flow:

M _M (I,K)＝M _IN (I,K)+M _MD (I,K) (8)

When the mixed air flow is distributed, the specific flow direction and flow amount are determined by the average temperature T _M (I, K) of the mixed air flow, the temperature T (I) of the Block I air layer of this layer, and the temperature T ( I+1) is judged by comparing the three, all or part of the inflow into Block I and Block (I+1) in proportion, that is, the flow amount M _IN (I,K) flowing to this layer and the flow amount M flowing to the next layer The ratio and criterion of _MD (I, K) are shown in Table 3.

table 3

The large space is divided into several areas in the vertical direction. Assuming that the temperature distribution in the mainstream area of each Block is uniform, due to the temperature difference in the adjacent mainstream areas, the air flow between areas will be caused. Heat exchange also occurs at the interface. When the temperature of the upper area is higher than that of the lower area, the air temperature distribution is stable at this time, and the heat will be transferred from the upper area to the lower area; Flow under the action of lift until the temperature of the upper and lower air is uniform, at this time, the heat transfer of the upper and lower temperature difference can be ignored.

When Block (I+1) is higher than the air temperature in the mainstream area of Block I, the heat transfer between the two is shown in the following equation (9).

Q _B (I+1,I)＝C _P M _C (I+1,I)[T(I+1)-T(I)]+C _B (I)A _B (I)[T(I+ 1)-T(I)] (9)

In the formula, A _B (I) is the area m ² of the adjacent interface between Block I and Block (I+1), C _B is the temperature difference heat transfer coefficient W/(m ² °C), T (I) is the area of Block I Air temperature ℃, M _C (I+1, I) is the air flow between Block I and Block (I+1) in kg/s, and the temperature difference heat transfer coefficient C _B value indicates that Block (I+1) to Block I The degree of heat transfer varies with factors such as the number of spatial layers. According to the experiment, when T(I+1)>T(I), C _B =2.3W/(m ² ·℃); when T(I+1)<T(I), it is caused by density difference The intensity of the heat transfer flow increases, C _B =116W/(m ² ·°C).

Step 5: Use the Block boundary condition - wall temperature to solve the convection-radiation coupling heat transfer; according to the geometric conditions of the building, divide it into walls, and solve the angle coefficient and Gebhart absorption coefficient between the walls. By assuming the initial temperature distribution of the wall, according to the indoor air temperature distribution, outdoor environmental parameters, thermal parameters of the enclosure structure, and indoor heat sources as boundary conditions, the heat conduction and radiation are calculated. Finally, according to the coupled heat balance equation, the simultaneous solution can obtain the distribution of wall temperature.

Step 6: Establish the air volume and energy balance equations according to the Block-Gebhart model; after completing the calculation of the above-mentioned sub-models, the mass balance and energy balance equations of each Block area can be established, and then the simultaneous equations are iteratively calculated and solved to obtain the indoor air Vertical temperature distribution, wall temperature distribution, and convective heat transfer load. For any block mainstream area, establish the equation.

Step 7: Block-Gebhart model is solved synchronously; the calculation steps of this model are as follows:

The calculation steps include: (1) Assume the initial temperature. Assuming the initial air vertical temperature distribution and wall temperature distribution, the initial wall temperature distribution is input into the wall heat conduction, convection, and radiation coupled heat transfer equations of the Gebhart model, and the air vertical temperature results calculated by the Block model are used as boundary conditions, and the initial air vertical temperature distribution is input into the Block In the heat-mass balance equation, the model uses the wall temperature results calculated by the Gebhart model as the boundary conditions for calculation, and the parameters of the two models are mutually input; (2) Iterative calculation. Compare the indoor air temperature and wall temperature distribution obtained in the second step with the initial set value in the first step. When the error between the two does not satisfy <10 ^-6 , assign it to the initial set value, and return to the first step to start repeated calculations . (3) Solve the temperature distribution of the wall surface and the vertical temperature distribution of the room in such a loop iteratively. When the relative error of the two calculation results of the previous and subsequent calculations is both <10 ^-6 , the calculation results of the last two calculations of the indoor air temperature distribution and the wall temperature distribution are considered is the solution of the problem, and take the net flow on the stratified interface calculated by the balance equations at this time to calculate the convective heat transfer load from the non-air-conditioned area to the air-conditioned area. According to the obtained inner wall surface temperature, indoor vertical temperature and the net air flow rate on the layered interface between the non-air-conditioned area and the air-conditioned area, according to q _d = C _p M _c5-4 (T ₅ -T ₄ )+C _B5-4 A _B5-4 (T ₅ -T ₄ ) calculation method to obtain the convective heat transfer load of stratified air-conditioning, where q _d the convective heat transfer load from the non-air-conditioned area to the air-conditioned area, C _P the specific heat of air at constant pressure, M _C5-4 Net air mass flow rate from non-air-conditioned area to air-conditioned area, T ₅ , T ₄ air temperature between non-air-conditioned area and air-conditioned area, C _B5-4 temperature difference heat transfer coefficient, A _B5-4 layered interface area between non-air-conditioned area and air-conditioned area .

Step 8: Experimental verification of the Block-Gebhart model to solve the convective heat transfer load; under the gaseous scale model test bench nozzle air supply system, conduct experimental research on the temperature field and convective transfer heat load in the large space room, according to the height of the laboratory and the nozzle At the location, the scale model is divided into 4 areas in the vertical direction, and the mass and energy balance equations are established for these 4 Block areas. Comparing the calculation results of the Block-Gebhart model with the experimental data results, it can be found that the maximum error between the experimental value and the theoretical value of the convective heat transfer load is 11.50%, and the average error of the six working conditions is 6.60%, which shows that Feasibility of calculating convective heat transfer loads using the Block-Gebhart model.

Step 9: Transform the relationship between the convective heat transfer load and its key influencing factors into dimensionless convective heat transfer load (convective heat transfer load under the relative heat gain of non-air-conditioned area), heat transfer between non-air-conditioned area and air-conditioned area The relationship between the intensity ratio and the heat exhaust ratio (relative to the heat gain in the non-air-conditioned area) is drawn into a line diagram for practical application.

The specific ideas for constructing the pre-calculation diagram are as follows: (1) Determine the heat intensity ratios of the study to be 0.32, 0.4, 0.45, 0.52, and 0.58; The heat intensity of the non-air-conditioned area is redistributed to the internal heat source of the non-air-conditioned area according to this ratio: 0, 100W, 200W, 300W, 400W; (3) Convective transfer heat calculated according to the model under different heat intensity ratios Load, respectively calculate the non-dimensional convective heat transfer load; (4) change the heat removal ratio to 0%, 10%, and 20%, respectively, and calculate according to the above method to obtain the final line calculation curve, as shown in Figure 4. It can be seen from the figure that under the same heat rejection ratio, as the heat intensity ratio increases, the amount of convective heat transfer from the non-air-conditioned area to the air-conditioned area gradually increases. This is because the heat gain directly acts on the non-air-conditioned area, causing the temperature of the non-air-conditioned area to rise, which will cause heat diffusion from the non-air-conditioned area to the air-conditioned area. In this way, the amount of heat transfer from the non-air-conditioned area to the air-conditioned area is increased. As the heat rejection ratio increases, the heat in the non-air-conditioned area is gradually eliminated, reducing the temperature difference between the non-air-conditioned area and the air-conditioned area, and weakening the heat diffusion from the non-air-conditioned area to the air-conditioned area, thereby reducing the heat dissipation from the non-air-conditioned area to the air-conditioned area. of heat transfer.

Step 10: Scale-scale model verification of the line calculation diagram. According to Figure 5, it can be seen that the experimental data of 0% heat removal ratio and 10% heat removal ratio are quite different from the calculation curve values of the original manual, which is consistent with the convection flow rate of this study. The heat transfer load line calculation diagram basically matches, which can basically explain the accuracy and applicability of the line calculation diagram application.

Finally, the line calculation diagram prepared by the present invention starts with the air flow, and obtains a simple method for calculating the convective heat transfer load by combining theory and experiment and supplemented by on-site measurement. The present invention is based on the Block-Gebhart theoretical model to analyze the indoor thermal environment such as temperature distribution and air flow of large-space buildings, and calculates the convective heat transfer load according to the temperature difference and flow volume between the non-air-conditioned area and the air-conditioned area interface area, and then analyzes the impact The key factors of the convective heat transfer load are the air supply parameters of the nozzle, the heat distribution from the outdoor to the indoor, and heat discharge, etc., using the relationship between the heat intensity ratio between the non-air-conditioned area and the air-conditioned area, the heat exhaust ratio, and the dimensionless convective heat transfer load Make a line calculation diagram for easy calculation of convective heat transfer load.

Claims (3)

1. A method for calculating the convective heat transfer load of air-supply layered air conditioner with large space nozzle, is characterized in that, specifically comprises the following steps: 1) Analyze the convective heat transfer load and establish the Block-Gebhart model: under the large-space indoor nozzle air supply system, the installation height of the nozzle is the layered height, which is the interface between the non-air-conditioned area and the air-conditioned area, and the upper part is the non-air-conditioned area. The bottom is the air-conditioning area. The convective heat transfer load includes the heat from the non-air-conditioning area to the air-conditioning area and the temperature difference heat transfer on the interface. The Block model divides the indoor environment into several control areas in the vertical direction, and the prediction calculation is large. Indoor vertical temperature distribution of space buildings, using the Gebhart absorption coefficient method, comprehensively considering the heat conduction, convection and radiation coupled heat transfer jointly affected by the outdoor environment heat transfer, indoor surface radiation heat transfer and indoor heat source radiation, to solve the indoor wall surface temperature distribution, And use this as the boundary condition for the calculation of the Block model, and use the Block-Gebhart model to solve the convective heat transfer load synchronously; 2) Experimental verification of the Block-Gebhart model to solve the convective heat transfer load: Under the gaseous scale model test bench nozzle air supply system, conduct experiments on the temperature field and convective transfer heat load in a large space, verify the model, and analyze the impact of convective heat For the key factors of transfer load, use the relationship between heat intensity ratio, heat removal ratio, and dimensionless convective heat transfer load between non-air-conditioned area and air-conditioned area to draw a line calculation diagram, simplify the calculation of convective heat transfer load, and use it for practical use. 2. According to claim 1, the method for calculating the convective heat transfer load of air-supply stratified air conditioners in large spaces is characterized in that the Block model in the step 1) adopts a Block model based on multi-zone heat and mass balance, which is used to predict large spaces Vertical temperature distribution inside the building; Assuming that the indoor environment is uniformly distributed in the horizontal direction except for the area affected by the air-conditioning jet, the concept of the lumped parameter method is used to analyze the mass flow and energy transfer for each control mainstream area, and the mass and energy balance equations are established respectively, and then Initially set the air temperature in the mainstream area and the wall surface temperature of each control area, and after a series of iterative calculations, finally calculate the temperature of each control area within the allowable error, so as to obtain the indoor vertical temperature distribution (T ₁ , T ₂ , T ₃ ...T _n ), n is the total number of control areas divided in the vertical direction; the installation height of the spout is taken as the layer height, which is the interface between the non-air-conditioned area and the air-conditioned area, that is, the 1-F layer is the air-conditioned area, and the F layer The above is a non-air-conditioned area, and the calculation formula for convective heat transfer load is as follows: q _d ＝C _p M _cF (T _F+1 -T _F )+C _BF A _BF (T _F+1 -T _F ) In the formula: q _d is the convective heat transfer load from the non-air-conditioned area to the air-conditioned area, in W; C _P is the specific heat of air at constant pressure, in kJ/(kg °C), and the value for air is 1.01; M _CF is non-air-conditioned The air quality net flow rate from the air-conditioned area to the air-conditioned area, in kg/s; T _F+1 , T _F are the air temperatures in the lowest layer of the non-air-conditioned area and the highest layer of the air-conditioned area, respectively, in °C; C _BF is the air-conditioning area from the non-air-conditioned area Temperature difference heat transfer coefficient, unit W/(m ² ·℃); A _BF is the layered interface area between non-air-conditioned area and air-conditioned area, unit m ² . 3. According to the method for calculating the convective heat transfer load of the air-supply layered air conditioner with large space nozzles according to claim 2, it is characterized in that the step 1) using the Block-Gebhart model to synchronously solve the convective heat transfer load specifically includes the following steps: A: Optimize the multi-jet calculation model of the nozzle, establish the wall flow model and the heat and mass exchange model between multiple regions; B: Use the Block boundary condition - wall temperature to solve the convection-radiation coupling heat transfer: according to the geometric conditions of the building, divide it into walls, and solve the angle coefficient and Gebhart absorption coefficient between the walls. By assuming the initial temperature distribution of the wall, according to the indoor air The temperature distribution, outdoor environmental parameters, thermal parameters of the enclosure structure and indoor heat sources are used as boundary conditions to calculate the heat conduction and radiation. Finally, according to the coupled heat balance equation, the temperature distribution of the wall surface can be obtained by simultaneous solution; C: Establish the air volume and energy balance equations according to the Block-Gebhart model; after completing the calculation of each regional sub-model, establish the mass balance and energy balance equations of each Block region, and then iteratively calculate and solve the indoor air vertical temperature by the simultaneous equations Distribution, wall temperature distribution and convective heat transfer load, for any block mainstream area, establish an equation; D: Block-Gebhart model synchronous solution: (1) Assuming the initial temperature, assuming the initial air vertical temperature distribution and wall temperature distribution, the initial wall temperature distribution is input into the Gebhart model wall heat conduction, convection, and radiation coupling heat transfer equation, and the air vertical temperature result calculated by the Block model is used as the boundary condition. The initial air vertical temperature distribution is input into the Block heat and mass balance equation. The model uses the wall temperature result calculated by the Gebhart model as the boundary condition for calculation, and the two model parameters are mutually input; (2) Iterative calculation: compare the indoor air temperature and wall temperature distribution obtained in the second step with the initial value of the first step, and when the error between the two does not satisfy <10 ^-6 , assign it to the initial value and return The first step starts to repeat the calculation; (3) Solve the temperature distribution of the wall surface and the vertical temperature distribution of the room in such a loop iteratively. When the relative error of the two calculation results of the previous and subsequent calculations is both <10 ^-6 , the calculation results of the last two calculations of the indoor air temperature distribution and the wall temperature distribution are considered is the solution of the problem, and take the net flow on the stratified interface calculated by the balance equations at this time to calculate the convective heat transfer load from the non-air-conditioned area to the air-conditioned area; according to the obtained inner wall temperature, indoor vertical temperature and non-air-conditioned area The net flow of air on the layer interface with the air-conditioning zone, and then according to the calculation formula of the convective heat transfer load, the convective heat transfer load of the layered air conditioner is obtained.