Calculation method of hourly stratified air conditioning cooling load for large-space buildings

Abstract

The present invention provides a method for calculating the hourly stratified air conditioning cooling load for large-space buildings. Based on the principle of thermal balance, a calculation scheme for the hourly stratified air conditioning cooling load for large-space buildings suitable for engineering applications is proposed. This method only requires dividing the large space into air-conditioned and non-air-conditioned areas based on the stratified air conditioning height. The cooling loads of the air-conditioned and initial non-air-conditioned areas are then calculated based on the design temperature of the air-conditioned areas. The characteristic temperature of the non-air-conditioned areas is then calculated using a proposed empirical formula to determine the actual cooling load of the non-air-conditioned areas, thereby obtaining the hourly stratified air conditioning cooling load. Furthermore, when calculating the cooling loads of the air-conditioned and initial non-air-conditioned areas, the hourly solar radiation heat transfer load generated by the excessively large transparent roof area of ​​large-area glass buildings is also taken into account. This makes the hourly stratified air conditioning cooling load calculation results more accurate and improves applicability. The present invention is easy for designers to use and meets the requirements for hourly cooling load calculation in summer.

Description

Technical Field

[0001] The present invention belongs to the technical field of large-space building air-conditioning load calculation, and in particular relates to a method for calculating hourly and layered air-conditioning cooling load of a large-space building. Background Art

[0002] Generally speaking, a building with a high height or a large volume is called a large space. In engineering, it is often defined as a building with a height greater than 10m and a building volume greater than 10,000m 3 For large spaces. To reduce building energy consumption and improve indoor air quality, large-space buildings often use layered air conditioning. Layered air conditioning refers to an air conditioning method that only air conditioners the lower area of ​​the building and maintains a certain temperature and humidity, while not requiring air conditioning in the upper area. However, the upper non-air-conditioned area can use natural ventilation or mechanical ventilation to promptly remove heat from the non-air-conditioned area. Layered air conditioning cooling load refers to the air conditioning cooling load required to maintain a certain temperature and humidity environment in the lower air-conditioned area of ​​a large space. It is the basis for determining the amount of cooling provided by the layered air conditioning system to the room, and is also the key to evaluating the energy consumption of layered air conditioning.

[0003] The indoor thermal environment of large-scale stratified air conditioning is characterized by pronounced vertical stratification and large air temperature gradients. This stratified indoor thermal environment significantly impacts the room's cooling load. Complex airflow patterns within large buildings, temporal variations in outdoor meteorological parameters, and indoor heat source distribution all contribute to variations in indoor thermal environment parameters and, consequently, in the stratified air conditioning cooling load. Therefore, calculating the hourly stratified air conditioning cooling load has always been a challenge for designers.

[0004] At present, the stratified air conditioning load of large-space buildings adopts the steady-state calculation method mentioned in the "Practical Heating and Air Conditioning Design Manual" edited by Professor Lu Yaoqing, which is called the "traditional stratified air conditioning cooling load calculation method". This method takes the air-conditioned area as the control body and uses the heat transfer load from the non-air-conditioned area to the air-conditioned area to represent the impact of the non-air-conditioned area on the air-conditioned area. Therefore, the stratified air conditioning load includes the conventional load of the air-conditioned area (heat transfer of the envelope structure, indoor heat source, outdoor fresh air or infiltration air, etc.), radiation heat transfer load and convection heat transfer load. The specific calculation method is as follows:

[0005] 1) The conventional load of the air-conditioned area is calculated using the traditional whole-room air-conditioning load calculation method.

[0006] 2) The calculation of the radiation heat transfer load is divided into two steps: the first step is to calculate the radiation heat transfer amount based on the wall radiation heat transfer from the non-air-conditioned area to the air-conditioned area and the solar radiation heat absorbed by the floor through the windows of the non-air-conditioned area, multiplied by the heat gain correction coefficient of the air-conditioned area (recommended to be 1.3) to obtain the radiation heat transfer amount from the non-air-conditioned area to the air-conditioned area. The wall radiation heat transfer is calculated using the direct radiation model; the second step is to determine the radiation transfer load formed by the radiation heat transfer amount by multiplying the radiation heat transfer amount by the cooling load coefficient (ranged from 0.45 to 0.72, generally 0.5).

[0007] 3) The convective heat transfer load is caused by the airflow from the non-air-conditioned area to the air-conditioned area. It was obtained through field experiments and theoretical analysis and calculation on the nozzle-supplied stratified air-conditioning in a tall steam turbine plant. According to the experimental results, the key factors affecting the convective heat transfer load are the heat intensity of the air-conditioned area, the heat intensity of the non-air-conditioned area, and the heat output of the non-air-conditioned area. Based on the experimental results, the relationship between the convective heat transfer load and these three factors is made into a line calculation diagram. After obtaining the heat intensity of the air-conditioned area, the heat intensity of the non-air-conditioned area, and the heat output of the non-air-conditioned area, the convective heat transfer load can be calculated by checking the line calculation diagram.

[0008] The above-mentioned calculation method for stratified air conditioning cooling load was developed by researchers in the 1980s through experimental research, theoretical analysis, and field testing of nozzle-assisted stratified air conditioning in a large steam turbine plant. This calculation method was limited in depth by the existing research on the thermal environment of large-space buildings. Many empirical values ​​derived from field data were used, and the experimental and field testing conditions were limited. Given the current depth of research on the indoor thermal environment of large-space buildings, this calculation method has the following drawbacks:

[0009] (1) When calculating the radiation heat transfer load and the convection heat transfer load, the temperature of the non-air-conditioned area must be obtained first. This method assumes that the temperature of the non-air-conditioned area is only related to the outdoor temperature and the temperature of the air-conditioned area. In fact, the temperature of the non-air-conditioned area is closely related to the indoor heat gain distribution. The current calculation method may cause a large deviation;

[0010] (2) Determine the radiant heat transfer load using the heat gain correction coefficient and cooling load coefficient for the air-conditioned area. The recommended value for the heat gain correction coefficient for the air-conditioned area is 1.3, and the recommended value range for the cooling load coefficient is 0.45 to 0.72, with 0.5 being the general value. The heat gain correction coefficient should be related to parameters such as the layer height. Currently, there is only one recommended value for this coefficient, which is not universal. The cooling load coefficient does not provide a specific application range for different values.

[0011] (3) The method of using the cooling load coefficient as a constant to determine the steady-state value of the cooling load does not meet the modern requirements for hourly air-conditioning load calculation. Summary of the Invention

[0012] In the aforementioned traditional stratified air conditioning cooling load calculation method, the radiation heat transfer load calculation method introduces two coefficients: the heat gain correction coefficient for the air-conditioning zone and the cooling load coefficient. The convective heat transfer load is calculated by consulting a line diagram. These two coefficients and the convective heat transfer load line diagram were derived from field data measured under nozzle-fed stratified air conditioning conditions in a steam turbine plant at the time. Limited by the experimental conditions at the time, the widespread application of modern large-space buildings across various industries, the increasing number of large spaces in public buildings, the proliferation of new airflow organization forms, and the increasing non-steady-state characteristics of large-space indoor environments, these empirical data derived from a single experimental environment have greatly reduced their applicability. This has resulted in the current calculation method for stratified air conditioning loads in large-space buildings being difficult to apply in many situations and presenting certain drawbacks.

[0013] To solve the above problems, a method for calculating the cooling load of large-space stratified air conditioning, which is suitable for engineering applications, is proposed based on the principle of heat balance and is designed for two commonly used stratified air conditioning modes: central air supply and lower air supply. The present invention adopts the following technical solutions:

[0014] The present invention provides a method for calculating the hourly stratified air-conditioning cooling load of a large-space building, which is applied to calculating the hourly stratified air-conditioning cooling load of a large-space building adopting stratified air-conditioning. The method is characterized by comprising the following steps: step S1, based on the design temperature of the air-conditioning zone of the large space and relevant indoor and outdoor design parameters, respectively calculating the hourly cooling load of the air-conditioned zone and the initial hourly cooling load of the non-air-conditioned zone according to the whole-room air-conditioning cooling load calculation method, and respectively calculating the corresponding design cooling load intensities; step S2, calculating the indoor air temperature gradient in the vertical direction of the large space based on the design cooling load intensities of the air-conditioned zone and the non-air-conditioned zone; step S3, calculating the characteristic temperature of the non-air-conditioned zone according to the indoor air temperature gradient; step S4, calculating the actual hourly cooling load of the non-air-conditioned zone based on the characteristic temperature of the non-air-conditioned zone; step S5, subtracting the hourly heat rejection from the sum of the hourly cooling load of the air-conditioned zone and the actual hourly cooling load of the non-air-conditioned zone, to obtain the hourly stratified air-conditioning cooling load of the large-space building.

[0015] Furthermore, in step S1, when the large-space building is a large-area glass building, the transparent portion area ratio of the roof of the large-space building needs to be considered, that is, the ratio of the glass area to the entire roof area. When the transparent portion area ratio of the roof is less than 30%, the solar radiation transmitted through the transparent portion of the vertical wall in the non-air-conditioned area has little effect on the heat transfer in the air-conditioned area. Therefore, there is no restriction on the transparent portion area ratio of the vertical wall in the non-air-conditioned area. The calculation formula for the hourly cooling load in the air-conditioned area is as follows:

[0016] Q 1,τ =Q 1w,τ +Q 1n,τ +Q 1x,τ

[0017] The calculation formula for the initial hourly cooling load of the non-air-conditioned area is as follows:

[0018] Q 02,τ =Q 02w,τ +Q 02n,τ +Q 02x,τ

[0019] Where Q 1,τ , Q 02,τ They are the hourly cooling load of the air-conditioned area and the initial hourly cooling load of the non-air-conditioned area, in W; Q 1w,τ , Q 1n,τ , Q 1x,τ The hourly cooling loads generated by the air-conditioning area enclosure structure, internal heat source, and outdoor fresh air or infiltration wind are respectively, in W; Q 02w,τ , Q 02n,τ , Q 02x,τ are the initial hourly cooling loads generated by the envelope structure, internal heat source, and outdoor fresh air or infiltration air in the non-air-conditioned area, respectively, in W. The hourly cooling load of the air-conditioned area generated by the envelope structure, internal heat source, fresh air or infiltration air and the initial hourly cooling load of the non-air-conditioned area are calculated according to relevant air-conditioning design manuals or air-conditioning load calculation software.

[0020] Furthermore, in step S1, when the transparent portion of the roof of a large building is greater than 30%, the hourly solar radiation heat transfer load must also be considered. In this case, since the solar radiation transmitted through the transparent portion of the vertical wall in the non-air-conditioned area has a smaller impact on the heat transfer in the air-conditioned area, there is no restriction on the transparent portion of the vertical wall in the non-air-conditioned area. The process of obtaining the hourly solar radiation heat transfer load is as follows:

[0021] For non-transparent enclosure structure, the load is only the temperature difference heat transfer load, while the transparent enclosure structure load is composed of two parts: the temperature difference heat transfer load and the solar radiation load. Therefore, the hourly cooling load Q of the enclosure structure in the air-conditioned area is 1w,τ The initial hourly cooling load Q of the enclosure structure in the non-air-conditioned area 02w,τ The calculation formula is as follows:

[0022] Q 1w，τ =Q 1c，τ +Q 1R，τ

[0023] Q 02w，τ =Q 02c，τ +Q 2R，τ

[0024] Where Q 1w,τ , Q 02w,τ The hourly cooling load of the air-conditioned area enclosure structure and the initial hourly cooling load of the non-air-conditioned area enclosure structure are respectively, in W; Q 1c,τ , Q 02c,τThe hourly cooling load of the heat transfer of the temperature difference of the air-conditioned area enclosure and the initial hourly cooling load of the heat transfer of the temperature difference of the non-air-conditioned area enclosure are respectively, in W; Q 1R,τ , Q 2R,τ The solar radiation hourly cooling load of the air-conditioned area enclosure structure and the solar radiation hourly cooling load of the non-air-conditioned area enclosure structure are respectively, in W, where Q 1R,τ Still calculated according to traditional methods.

[0025] Since the solar radiation load is basically not affected by the air temperature, the temperature difference in the non-air-conditioned area will only affect the hourly cooling load of the temperature difference heat transfer of the enclosure structure. Therefore, the initial solar radiation hourly cooling load Q 02R,τ and the actual hourly cooling load Q of the solar radiation in the non-air-conditioned area 2R,τ are consistent, so the calculation formula for the hourly solar radiation heat transfer load in the non-air-conditioned area is as follows:

[0026]

[0027] Where Q SR,τ is the hourly solar radiation heat transfer load of the non-air-conditioned area, unit is W; N is the number of transparent enclosure structures in the non-air-conditioned area; i is the i-th transparent enclosure structure in the non-air-conditioned area; Q 2R,i,τ is the hourly cooling load of the transparent enclosure structure of the i-th non-air-conditioned area by solar radiation, unit W; X i,空调区 is the angular coefficient of the transparent enclosure structure of the i-th non-air-conditioned area to the entire air-conditioned area.

[0028] Based on the hourly solar radiation heat transfer load calculated above, the hourly cooling load Q of the air-conditioning area is calculated respectively. 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ , see the following formula:

[0029] Q 1，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ +Q SR，τ

[0030] Q 02，τ =Q 02w，τ +Q 02n，τ +Q 02x，τ -Q SR，τ .

[0031] Furthermore, in step S1, the design cooling load intensity q1 of the air-conditioned area and the initial design cooling load intensity q 02 The calculation formulas are as follows:

[0032]

[0033]

[0034] Where q1 is the design cooling load intensity of the air-conditioning area, unit is W / m 3 ;q 02 Initial design cooling load intensity for non-air-conditioned areas, unit: W / m 3 ; Q1 is the design cooling load of the air-conditioned area, which is the hourly cooling load Q of the air-conditioned area 1,τ Peak load in W; Q 02 is the initial design cooling load of the non-air-conditioned area, and is the initial hourly cooling load Q of the non-air-conditioned area. 02,τ The peak load in the unit is W; V1 and V2 are the volumes of the air-conditioned area and the non-air-conditioned area, respectively, in m 3 .

[0035] Furthermore, in step S2, the indoor air temperature gradient ▽t is calculated according to the following empirical formula:

[0036] Central nozzle air supply stratified air conditioning:

[0037]

[0038] Downward air supply stratified air conditioning:

[0039]

[0040] Where, is the indoor air temperature gradient in the vertical direction, unit is ℃ / m; n p is the number of exhaust times in the non-air-conditioned area, unit: times / h; H is the building height, unit: m.

[0041] Furthermore, in step S3, the calculation formula of the characteristic temperature t2 of the non-air-conditioned area is:

[0042]

[0043] Where t1 and t2 are the design temperature of the air-conditioned area and the characteristic temperature of the non-air-conditioned area, respectively, in °C; h1 and h2 are the heights of the air-conditioned area and the non-air-conditioned area, respectively, in m.

[0044] Furthermore, in step S4, various hourly cooling loads of the actual non-air-conditioned area are calculated again based on the characteristic temperature t2 of the non-air-conditioned area. The calculation can be performed according to relevant air-conditioning design manuals or air-conditioning load calculation software.

[0045] Furthermore, in step S5, the heat Q is discharged hourly. p,τ and the exhaust temperature of non-air-conditioned area t p Related, exhaust temperature t p Determined by the characteristic temperature t2 of the non-air-conditioned area, the hourly heat dissipation is approximately a steady-state value, and the exhaust temperature t p and heat rejection Q p The calculation formulas are as follows:

[0046]

[0047] Where, t p is the exhaust temperature, unit is ℃; Δh p The height difference between the exhaust center plane and the non-air-conditioned area center plane, unit is m; h p is the exhaust height, in meters; if the exhaust is located at the top of the building, it is equal to the building height H;

[0048] Q p =C p ρV2n p (t p -t1) / 3600

[0049] Where Q p Heat dissipated from non-air-conditioned areas, unit: W; C p is the specific heat capacity of air at constant pressure, in J / (kg·℃); ρ is the air density, in kg / m 3 .

[0050] Furthermore, the hourly stratified air conditioning cooling load Q of large space buildings τ The solution formula is as follows:

[0051] Q τ =Q 1，τ +Q 2，τ -Q p，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ +Q 2w，τ +Q 2n，τ +Q 2x，τ -Q p，τ

[0052] Where Q τ is the hourly stratified air conditioning cooling load, unit is W; Q 1,τ is the hourly cooling load of the air-conditioned area, unit is W; Q 2,τ is the actual hourly cooling load of the non-air-conditioned area, unit: W; Q p,τ The heat dissipated hourly, unit is W; Q 2w,τ , Q 2n,τ , Q 2x,τ They are the hourly cooling loads generated by the actual non-air-conditioned area enclosure structure, internal heat source, and outdoor fresh air or infiltration air, in W.

[0053] Functions and effects of the invention

[0054] The present invention addresses the lack of a mature and comprehensive method for calculating the cooling load of large-space hourly stratified air conditioning in buildings. Based on the principle of thermal balance, this method, suitable for engineering applications, is proposed for two commonly used stratified air conditioning systems: central and lower nozzle air supply. The calculation conditions required by this method are consistent with those for whole-room air conditioning cooling load calculations. The method simply divides the large space into air-conditioned and non-air-conditioned zones based on the stratified air conditioning height. The cooling loads for the air-conditioned and initial non-air-conditioned zones are then calculated based on the design temperatures of the air-conditioned zones. The empirical formula proposed in this invention is then used to determine the characteristic temperature of the non-air-conditioned zones, and then the actual non-air-conditioned zone cooling load is calculated, resulting in the hourly stratified air conditioning cooling load.

[0055] Considering that large-area glass buildings can generate solar radiation heat transfer loads by transmitting solar radiation through non-air-conditioned glass into air-conditioned areas, this invention also proposes a method for calculating the hourly, stratified air-conditioning cooling load for large spaces with large glass areas. This method, when the ratio of the transparent roof area is greater than 30%, also considers the solar radiation heat transfer load when calculating the cooling load for the air-conditioned area and the initial cooling load for the non-air-conditioned area, thus improving its applicability and expanding its scope. Furthermore, since the characteristic temperature of the non-air-conditioned area takes into account more influencing factors, it is more realistic.

[0056] Furthermore, compared to traditional methods, the present invention's hourly cooling load calculation method for stratified air conditioning in large-space buildings solves the problem of only being able to calculate stratified air conditioning cooling loads in a steady-state manner, resulting in calculated cooling loads that do not conform to actual, unsteady-state conditions. This provides air conditioning designers with a more robust numerical basis for design, ultimately ensuring that the cooling capacity calculated for stratified air conditioning systems is closer to actual conditions. In summary, this method is also easier for designers to use and meets the requirements for hourly cooling load calculations in summer. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a schematic diagram of the composition of stratified air conditioning loads for large-space buildings in the present invention;

[0058] Figure 2 This is a flow chart of a method for calculating the cooling load of large-space stratified air conditioning by hour in the first embodiment of the present invention;

[0059] Figure 3 This is an interior view of the large-space thermal environment experimental base in Example 1 of the present invention;

[0060] Figure 4 This is a diagram showing the arrangement of fixed indoor temperature measurement lines in Example 1 of the present invention;

[0061] Figure 5A comparison chart of the calculated cooling load value of the stratified air conditioning system and the experimental cooling capacity in Example 1 of the present invention;

[0062] Figure 6 This is a flow chart of a method for calculating hourly stratified air conditioning loads applicable to large glass areas and large spaces in the second embodiment of the present invention;

[0063] Figure 7 This is a view of the interior of the large space on the top floor of the Shanghai Stock Exchange in Example 2 of the present invention;

[0064] Figure 8 This is a plan view of the indoor temperature measurement line in the second embodiment of the present invention;

[0065] Figure 9 This is an elevation view of the indoor temperature measurement line in the second embodiment of the present invention;

[0066] Figure 10 This is a comparison chart of the calculated cooling load value of the stratified air conditioning and the experimental cooling capacity in Example 2 of the present invention. DETAILED DESCRIPTION

[0067] The traditional calculation principle of stratified air conditioning cooling load is to take the air-conditioned area as the control body, including the conventional load of the air-conditioned area (enclosing structure, indoor heat source, outdoor fresh air or infiltration air load, etc.), convective heat transfer load and radiant heat transfer load. Figure 1 This is a schematic diagram of the composition of stratified air-conditioning loads in large-space buildings. The calculation method is shown in formula (1).

[0068] Q=Q 1w +Q 1n +Q 1x +Q f +Q d (1)

[0069] Where: Q is the cooling load of the stratified air conditioning, unit is W; Q 1w is the cooling load of the enclosure structure in the air-conditioning area, unit is W; Q 1n is the cooling load of heat source in the air-conditioning area, unit is W; Q 1x It is the cooling load generated by outdoor fresh air or infiltration air in the air-conditioning area, unit is W; Q f It is the cooling load caused by the radiant heat transfer from the non-air-conditioned area to the air-conditioned area, in W; Q d It is the cooling load caused by convective heat transfer from non-air-conditioned area to air-conditioned area, unit is W.

[0070] Now, taking the non-air-conditioned area as the control body, a heat balance equation is established for the air in the non-air-conditioned area based on the heat balance principle, as shown in Equation (2). The left side of the equation represents the heat entering the non-air-conditioned area, and the right side of the equation represents the heat leaving the non-air-conditioned area.

[0071] Q 2w +Q 2n +Q2x =Q f +Q d +Q p (2)

[0072] Where: Q 2w is the cooling load of the enclosure structure in the non-air-conditioned area, unit: W; Q 2n is the cooling load of heat source in non-air-conditioned area, unit is W; Q 2x It is the cooling load generated by outdoor fresh air or infiltration air in non-air-conditioned areas, unit is W; Q p It is the heat rejection in non-air-conditioned area, unit is W.

[0073] The combined equations (1) and (2) can be used to calculate the stratified air conditioning cooling load Q, as shown in equation (3):

[0074] Q=Q 1w +Q 1n +Q 1x +Q 2w +Q 2n +Q 2x -Q p (3)

[0075] The principle of energy conservation proves that the cooling load transferred from non-conditioned areas to conditioned areas in traditional stratified air conditioning cooling load calculation methods is the cooling load generated in the non-conditioned areas (i.e., the cooling load of the enclosure structure, the cooling load from heat sources, and the cooling load from outdoor fresh air or infiltration). It can be seen that the key to energy saving in stratified air conditioning is that the air temperature in the non-conditioned areas is higher than that in the conditioned areas, which reduces the cooling load of the enclosure structure in the non-conditioned areas.

[0076] This invention defines the characteristic temperature t2 of the non-air-conditioned zone as the air temperature at which the load generated, assuming the entire non-air-conditioned zone is in a uniform and equal characteristic temperature space, is equal to the load generated when the non-air-conditioned zone is temperature-stratified. Because the air-conditioned zone temperature is typically the design temperature, the air-conditioned zone cooling load is calculated using the design temperature, while the non-air-conditioned zone cooling load can be calculated using its characteristic temperature. The sum of the two, minus the heat rejection, yields the large-space stratified air-conditioning cooling load.

[0077] According to this principle, the method first calculates the hourly cooling load Q of the air-conditioning zone based on the design temperature t1 of the air-conditioning zone using relevant input parameters according to the whole room air-conditioning cooling load calculation method. 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ Then define the indoor air temperature gradient in the vertical direction of the large space As shown in formula (4), It can be calculated according to the two empirical formulas proposed in the present invention.

[0078]

[0079] Where, is the indoor air temperature gradient in the vertical direction of the large space, in °C / m; t1 and t2 are the design temperature of the air-conditioned area and the characteristic temperature of the non-air-conditioned area, in °C; h1 and h2 are the heights of the air-conditioned area and the non-air-conditioned area, in m.

[0080] According to the above temperature gradient The characteristic temperature t2 of the non-air-conditioned area can be obtained. The actual hourly cooling load Q of the non-air-conditioned area can be calculated again using the obtained t2 according to the whole room air-conditioning cooling load calculation method. 2,τ The final hourly cooling load Q of the air-conditioned area 1,τ and the actual hourly cooling load Q of the non-air-conditioned area 2,τ The sum of the heat dissipated hourly Q p,τ It is the large space hourly stratified air conditioning cooling load Q τ .

[0081] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the following is a detailed description of the method for calculating the hourly stratified air-conditioning cooling load of a large-space building of the present invention in conjunction with embodiments and drawings.

[0082] <Example 1>

[0083] This embodiment 1 provides a method for calculating the hourly stratified air conditioning cooling load in an actual large-space building under two airflow arrangements: central nozzle air supply and downward air supply, experimental verification, and an hourly air conditioning load calculation case.

[0084] Figure 2 This is a flow chart of a method for calculating hourly stratified air conditioning cooling load in a large space in the first embodiment of the present invention.

[0085] like Figure 2 As shown in the figure, the specific calculation process of large space hourly stratified air conditioning cooling load is as follows:

[0086] Step S1, calculate the hourly cooling load Q of the air-conditioning zone 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ .

[0087] First, based on the design temperature t1 of the air-conditioning zone, the hourly cooling load Q of the air-conditioning zone is calculated using the following equations (5) and (6): 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ ,

[0088] Q 1，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ (5)

[0089] Q 02，τ =Q02w，τ +Q 02n，τ +Q 02x，τ (6)

[0090] Where Q 1,τ , Q 02,τ They are the hourly cooling load of the air-conditioned area and the initial hourly cooling load of the non-air-conditioned area, in W; Q 1w,τ , Q 1n,τ , Q 1x,τ The hourly cooling loads generated by the air-conditioning area enclosure structure, internal heat source, and outdoor fresh air or infiltration wind are respectively, in W; Q 02w,τ , Q 02n,τ , Q 02x,τ They are the initial hourly cooling loads formed by the enclosure structure of the non-air-conditioned area, the internal heat source and the outdoor fresh air or infiltration wind, respectively, in W.

[0091] In the above formula, the hourly cooling load of enclosing structures such as exterior walls and windows, the cooling load of personnel, the cooling load of lighting, the hourly cooling load of internal heat sources such as equipment, and the hourly cooling load of outdoor fresh air or infiltration air can be calculated according to relevant air-conditioning design manuals or air-conditioning load calculation software.

[0092] Then, the design cooling load intensity q1 of the air-conditioned area and the initial design cooling load intensity q of the non-air-conditioned area are calculated according to equations (7) and (8). 02 .

[0093]

[0094]

[0095] Where q1 is the design cooling load intensity of the air-conditioning area, unit is W / m 3 ;q 02 Initial design cooling load intensity for non-air-conditioned areas, unit: W / m 3 ; Q1 is the design cooling load of the air-conditioned area, which is the hourly cooling load Q of the air-conditioned area 1,τ Peak load in W; Q 02 is the initial design cooling load of the non-air-conditioned area, and is the initial hourly cooling load Q of the non-air-conditioned area. 02,τ The peak load in the unit is W; V1 and V2 are the volumes of the air-conditioned area and the non-air-conditioned area, respectively, in m 3 .

[0096] Step S2: Calculate the vertical indoor air temperature gradient ▽t.

[0097] The vertical indoor air temperature gradient ▽t is related to many factors, including the cooling load intensity of the air-conditioned area and the non-air-conditioned area, the number of exhaust times in the non-air-conditioned area, and the building height. It can be calculated using empirical formulas (9) and (10).

[0098] For central nozzle air supply stratified air conditioner:

[0099]

[0100] For downflow stratified air conditioners:

[0101]

[0102] Where, is the indoor air temperature gradient in the vertical direction, unit is ℃ / m; n p is the number of exhaust times in the non-air-conditioned area, unit: times / h; H is the building height, unit: m.

[0103] The applicable range of the above empirical formula is: q1<150W / m 3 ,q 02 <80W / m 3 , n p <4 times / h, H < 55m, applicable only to rectangular or nearly rectangular buildings. If the building roof is pitched with a slope angle less than 30°, it can be approximated as a flat roof based on the principle of constant building volume. Substitute the equivalent building height into the above formula to calculate the air temperature gradient.

[0104] Step S3, calculating the characteristic temperature t2 of the non-air-conditioned area.

[0105] The temperature gradient calculated in step S2 Substituting into equation (11) we can obtain the characteristic temperature t2 of the non-air-conditioned area.

[0106]

[0107] Where t1 and t2 are the design temperature of the air-conditioned area and the characteristic temperature of the non-air-conditioned area, respectively, in °C; h1 and h2 are the heights of the air-conditioned area and the non-air-conditioned area, respectively, in m.

[0108] Step S4, calculate the actual hourly cooling load Q of the non-air-conditioned area 2,τ .

[0109] Based on the characteristic temperature t2 of the non-air-conditioned area, the actual hourly cooling load of the non-air-conditioned area is calculated again according to the whole-room air-conditioning cooling load calculation method. It can be calculated according to the relevant air-conditioning design manual or air-conditioning load calculation software.

[0110] Step S5, calculate the hourly stratified air conditioning cooling load Q τ .

[0111] The hourly heat rejection is related to the exhaust temperature of the non-air-conditioned area. The exhaust temperature can be determined by the characteristic temperature t2 of the non-air-conditioned area (t2 is equivalent to the design temperature when the entire non-air-conditioned area is uniform). Therefore, the hourly heat rejection is approximately a steady-state value. The calculation of the exhaust temperature and heat rejection is shown in Equations (12) and (13).

[0112]

[0113] Where, t p is the exhaust temperature, unit is ℃; Δh p The height difference between the exhaust center plane and the non-air-conditioned area center plane, unit is m; h p is the exhaust height, in meters; if the exhaust is located at the top of the building, it is equal to the building height H;

[0114] Q p =c p ρV2n p (t p -t1) / 3600 (13)

[0115] Where Q p Heat dissipated from non-air-conditioned areas, unit: W; C p is the specific heat capacity of air at constant pressure, in J / (kg·℃); ρ is the air density, in kg / m 3 .

[0116] Then add the hourly cooling loads of the air-conditioned area obtained in step S1 to the actual hourly cooling loads of the non-air-conditioned area obtained in step S4, and then subtract the hourly heat rejection to obtain the hourly stratified air-conditioned cooling loads.

[0117] Q τ =Q 1，τ +Q 2，τ -Q p，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ +Q 2w，τ +Q 2n，τ +Q 2x，τ -Q p，τ (14)

[0118] Where Q τ is the hourly stratified air conditioning cooling load, unit is W; Q 1,τ is the hourly cooling load of the air-conditioned area, unit is W; Q 2,τ is the actual hourly cooling load of the non-air-conditioned area, unit: W; Q p,τ The heat dissipated hourly, unit is W; Q 2w,τ , Q 2n,τ , Q 2x,τ They are the hourly cooling loads generated by the actual non-air-conditioned area enclosure structure, internal heat source, and outdoor fresh air or infiltration air, in W.

[0119] Experimental verification:

[0120] In the first embodiment, the feasibility of the present invention is experimentally verified based on the following experimental environment using two airflow organizations: central nozzle air supply and downward air supply.

[0121] Experimental environment: The experiment was conducted in a large space thermal environment experimental base in Shanghai, the interior of which is as follows Figure 3 As shown, the total area of ​​the building is 500m 2 The north-south span is 18m, and the east-west span is 27.7m. The highest and lowest points of the sloping roof are 12m and 9.6m above the ground, respectively. The maximum height of the east wall skylight is 13.8m, and the roof pitch is 14°. The north and west walls are exterior walls, while the east and south walls are interior walls. The north exterior wall has six windows measuring 1.5m x 2m, and the west exterior wall has 24 windows measuring 1.48m x 1.48m, all single-glazed. Sixteen CNC machine tools are located on the ground floor, ten of which have a power of 3.7kW and the remaining six have a power of 7.5kW. Eight chandeliers are located approximately 5.5m above the ground, with a total power of 1.8kW. The basic structure of the enclosure from the outside to the inside and its thermal parameters are shown in Table 1 below.

[0122] Table 1 Basic structure of enclosure structure and its thermal parameters

[0123]

[0124] The building has two air flow organization forms. One is the central nozzle air supply stratified air conditioning form, with 8 nozzles installed at a height of 5.5m on the east wall. The aperture of each nozzle is 373mm and the spacing is 1.5m. The other is the bottom air supply stratified air conditioning form, with 4 semi-cylindrical air supply devices installed on the south and north walls. The total height of each air supply device is 1.5m and the diameter is 1.0m. The rated air supply volume of the unit is 30,000m 3 / h. A centralized return air vent is set against the east wall of the machine room to form a single-side downward return air. The return air vent is 3m×2m in size and is embedded in the east wall 0.5m above the ground. An exhaust device is installed on the top of the building.

[0125] Considering the influence of airflow organization on thermal environment, the arrangement of 9 vertical temperature fixed measuring lines in the experimental base is shown in Figure 4Fixed temperature measurement points were placed at least 3 meters above the ground, with vertical temperature measurement points spaced evenly at 1 meter intervals. Mobile measurement lines (A, C, E, I, and K) were installed within the personnel activity area, 3 meters or less above the ground. The measurement points were 0.2m, 1m, and 2m above the ground when the nozzles were blown from the center, and 0.1m, 0.3m, 1.1m, and 1.7m above the ground when the nozzles were blown from the bottom. Fixed temperature measurement points were directly collected using PT1000 sensors with an accuracy of ±0.2°C. Mobile temperature measurement points used a Testo 174T temperature sensor with an accuracy of ±0.5°C and a glass thermometer with an accuracy of ±0.1°C. Outdoor air temperature and humidity were measured by an outdoor weather station with an accuracy of ±0.2°C and ±2.5% RH. Solar radiation was measured using a solar radiometer with an accuracy of ±2% of reading. Air volume parameters were calculated by averaging multiple measurements taken at the air outlet using a hot-wire anemometer with an accuracy of ±3% of reading. All instruments were calibrated and adjusted in the laboratory before the experiment.

[0126] The experimental procedures for the central nozzle air supply and columnar downward air supply were essentially similar, with one operating condition tested daily. Each operating condition was started between 8:00 and 9:00 AM, and data recording began after one hour, with measured data recorded every 30 minutes. As the experiment progressed, each operating condition gradually stabilized. Between 1:00 PM and 3:00 PM, the indoor thermal environment and air conditioning system supply and return air parameters remained essentially stable. The calculations in this paper were based on experimental data from this period. Table 2 shows the experimental conditions, with A1–A3 representing the central nozzle air supply conditions and B1–B3 representing the downward air supply conditions. All parameters in this table are experimentally measured values. Indoor heat sources include personnel in the air-conditioned area, CNC machine tools, and lighting fixtures in the non-air-conditioned area.

[0127] Table 2 Experimental conditions

[0128]

[0129] In order to quantitatively analyze the errors between the calculated and experimental values ​​of temperature and load, the mean absolute error (MAE) and mean absolute percentage error (MAPE) were used for evaluation, as shown in Equations (15) and (16).

[0130]

[0131]

[0132] Where n is the number of working conditions for different airflow organizations; x th,i is the theoretical calculated value of operating temperature or load; x ex,i It is the experimental measurement value of the operating temperature or load.

[0133] Based on the experimentally measured temperature of the air-conditioned area in Table 2, the cooling load and intensity of the air-conditioned area and the initial cooling load and intensity of the non-air-conditioned area can be calculated. The calculation results are shown in Table 3 below.

[0134] Table 3 Calculation results of cooling load and intensity in air-conditioned and non-air-conditioned areas

[0135]

[0136] Then, the empirical formulas (9) and (10) proposed in the present invention can be used to calculate the characteristic temperatures of the non-air-conditioned area under the six experimental conditions. The calculated values ​​of the characteristic temperatures of the non-air-conditioned area are compared with the experimental values ​​in Table 4, where the experimental value is the average value of the measured temperatures of all measuring points in the non-air-conditioned area.

[0137] Table 4 Comparison of calculated and experimental characteristic temperatures in non-air-conditioned areas

[0138] Working conditions Calculated value / ℃ Experimental value / ℃ Absolute error / ℃ Relative error A1 31.0 29.2 1.8 6.1％ A2 31.8 30.0 1.8 6.0％ A3 33.6 33.1 0.5 1.5％ B1 34.0 33.1 0.9 2.6％ B2 33.9 34.8 -0.9 -2.6％ B3 34.3 33.0 1.3 3.8％

[0139] The data in Table 4 show that for the three operating conditions (conditions A1-A3) with central airflow, the average absolute error (MAE) between the calculated and experimental values ​​of the characteristic temperature in the non-air-conditioned area is 1.4°C, and the average absolute relative error (MAPE) is 4.5%. For the three operating conditions (conditions B1-B3) with lower airflow, the average absolute error (MAE) is 1.0°C, and the average absolute relative error (MAPE) is 3.0%. This demonstrates that the empirical formulas proposed in the present invention for the two stratified air conditioning modes are highly reliable for predicting the vertical air temperature gradient and the characteristic temperature in the non-air-conditioned area of ​​actual large-space buildings.

[0140] Since the calculation is based on the experimental data of the stable time period, only the steady-state stratified air conditioning cooling load is verified here. After obtaining the characteristic temperature of the non-air-conditioned area, the calculated value of the stratified air conditioning cooling load is obtained according to formula (14), and it is compared with the experimental cooling capacity. The experimental cooling capacity can be calculated by the experimentally measured supply air volume and supply and return air temperatures. The comparison results are shown in Figure 5 The comparison results show that for the three operating conditions with central airflow (conditions A1 to A3), the average absolute error (MAE) between the calculated stratified air conditioning cooling load and the experimental cooling capacity is 3.1 kW, and the average absolute relative error (MAPE) is 6.6%. For the three operating conditions with lower airflow (conditions B1 to B3), the average absolute error (MAE) is 2.2 kW, and the average absolute relative error (MAPE) is 4.6%. This shows that the calculation method proposed in this invention can quickly and accurately solve the stratified air conditioning cooling load of actual large-space buildings.

[0141] Calculation example:

[0142] After verifying the feasibility of this method through the above experiments, this first embodiment also provides a large-space hourly stratified air conditioning cooling load calculation case for two airflow organizations: central nozzle air supply and downward air supply. The case object is still the large-space thermal environment experimental base used in the experimental verification. The calculation conditions are as follows: there are 10 people working in the experimental base, the activity intensity is moderate, 5 machine tools with a power of 3.7kW are turned on, and the usage factor is 1.0, the installation factor is 0.8, the load factor is 0.5, the ventilation and insulation factor is 1, and the lighting power density is 11W / m 2 , personnel and equipment are located in the air-conditioned area, and lighting is located in the non-air-conditioned area. The working hours are from 10:00 to 18:00.

[0143] The middle nozzle air supply layer height is 5.5m, the lower air supply layer height is 2.6m, the building top is equipped with an exhaust device, the middle nozzle air supply non-air-conditioned area exhaust times n p Take 1 time / h. In order to keep the exhaust volume consistent, remove the exhaust frequency n in the non-air-conditioned area. p The average temperature of the air conditioning zone is 0.65 times / h. The outdoor meteorological parameters adopt the Shanghai summer design parameters, with an outdoor dry-bulb temperature of 34.4°C and an outdoor daily average temperature of 30.8°C. The design temperature t1 of the air-conditioned zone is 26°C. The adjacent room is a large, unconditioned space, resulting in a temperature difference of 3°C between the air-conditioned zones. The comprehensive shading coefficient of the exterior windows is 0.8. The relevant calculation conditions in this article are based on the "Practical Heating and Air Conditioning Design Manual" (Second Edition) and the "Design Code for Heating, Ventilation and Air Conditioning of Civil Buildings" (GB 50736-2012). The goal is to calculate the hourly stratified air conditioning cooling load for two airflow configurations, central nozzle air supply and downflow air supply, from 10:00 to 18:00 during working hours.

[0144] (1) Calculate the hourly stratified air conditioning cooling load of the central nozzle air supply:

[0145] Step 1: Set the design temperature t1 of the air-conditioning zone to 26℃ and the layer height to 5.5m, and calculate the hourly cooling load Q of the air-conditioning zone. 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ (W), the calculation results are shown in Table 5 and Table 6 below respectively.

[0146] Table 5 Hourly cooling load of each air-conditioning zone (W)

[0147]

[0148] Table 6 Initial hourly cooling loads of non-air-conditioned areas (W)

[0149]

[0150]

[0151] Then calculate the design cooling load intensity of the air-conditioned area and the initial design cooling load intensity of the non-air-conditioned area (W / m 3 ):

[0152] Design cooling load intensity of air-conditioning area:

[0153] Initial design cooling load intensity of non-air-conditioned area:

[0154] Step 2: Calculate the vertical indoor air temperature gradient (℃ / m).

[0155] Number of air changes in non-air-conditioned areas: n p =1 time / h.

[0156] The maximum height of the roof of this building is 12m at the top of the double slope, and the minimum height is 9.6m at the bottom of the double slope. The slope angle is 14°, which is less than 30°. According to the principle of constant volume, the sloping roof is approximated as a flat roof. At this time, the equivalent height of the building is 10.8m.

[0157] According to formula (9), the vertical temperature gradient of air is calculated

[0158]

[0159] Therefore, the vertical temperature gradient of the air is obtained It is 1.05℃ / m.

[0160] Step 3: Calculate the characteristic temperature t2 (°C) of the non-air-conditioned area:

[0161]

[0162] Step 4: Calculate the actual hourly cooling load Q of the non-air-conditioned area 2,τ (W).

[0163] According to the characteristic temperature t2 of the non-air-conditioned area of ​​31.7℃, calculate the actual hourly cooling load Q of the non-air-conditioned area 2,τ The results are shown in Table 7. Since the adjacent room is a large, unconditioned space, the temperature in the non-conditioned area will also be higher, so the temperature difference between the adjacent room and the non-conditioned area will be smaller. Therefore, the hourly load on the interior wall of the non-conditioned area is ignored. If the design temperature value of the adjacent room is available, the calculation can also be based on the temperature difference with the design temperature of the adjacent room.

[0164] Table 7 Actual hourly cooling load of non-air-conditioned area (W)

[0165]

[0166]

[0167] Step 5: Calculate the hourly stratified air conditioning cooling load Q τ (W):

[0168] First calculate the exhaust air temperature:

[0169]

[0170] Then calculate the heat rejection:

[0171] Q p =C p ρV2n p (t p -t1) / 3600=1010×1.2×2631×1×(34.4-26) / 3600

[0172] =7499W

[0173] Finally, the hourly stratified air conditioning cooling load (W) is calculated and shown in Table 8 below.

[0174] Table 8 Hourly stratified air conditioning cooling load (W)

[0175] time 10 11 12 13 14 15 16 17 18 <![CDATA[Cooling load Q of the air-conditioned area 1,τ > 17982 19151 19669 21014 23553 26354 28466 29183 28263 <![CDATA[Cooling load Q2 in the non-air-conditioned area,]]> 8282 11351 13228 17728 22783 27437 30777 32194 31414 <![CDATA[Heat rejection Q p / W]]> 7499 7499 7499 7499 7499 7499 7499 7499 7499 <![CDATA[Stratified air-conditioning cooling load Q τ > 18765 23003 25398 31242 38837 46292 51744 53878 52178

[0176] The maximum cooling load of the central nozzle air supply is at 17:00, the cooling load of the stratified air conditioning is 53878W, and the cooling load index is 108W / m 2 .

[0177] (2) Calculate the hourly stratified air conditioning cooling load for downflow:

[0178] Step 1: Set the design temperature t1 of the air-conditioning zone to 26℃ and the layer height to 2.6m, and calculate the hourly cooling load Q of the air-conditioning zone. 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ (W), the results are shown in Tables 9 and 10 below:

[0179] Table 9 Hourly cooling load of each item in air-conditioning zone (W)

[0180]

[0181]

[0182] Table 10 Initial hourly cooling loads of non-air-conditioned areas (W)

[0183]

[0184] Then calculate the design cooling load intensity of the air-conditioned area and the initial design cooling load intensity of the non-air-conditioned area (W / m 3 ).

[0185] Design cooling load intensity of air-conditioning area:

[0186] Initial design cooling load intensity of non-air-conditioned area:

[0187] Step 2: Calculate the vertical indoor air temperature gradient (℃ / m).

[0188] Number of air changes in non-air-conditioned areas: n p =0.65 times / h; building height: H=10.8m.

[0189] According to formula (10), the vertical temperature gradient of air is calculated

[0190]

[0191] Therefore, the vertical temperature gradient of the air is obtained It is 1.61℃ / m.

[0192] Step 3: Calculate the characteristic temperature t2 (°C) of the non-air-conditioned area:

[0193]

[0194] Step 4: Calculate the actual hourly cooling load Q of the non-air-conditioned area based on the characteristic temperature t2 of the non-air-conditioned area of ​​34.7°C. 2,τ (W), the results are shown in Table 11 below.

[0195] Table 11 Actual hourly cooling load of non-air-conditioned areas (W)

[0196] time 10 11 12 13 14 15 16 17 18 Lighting load 695 1244 1381 1463 1520 1563 1599 1628 1652 North exterior wall load -925 -934 -903 -836 -736 -607 -456 -294 -131 West exterior wall load 64 -13 -61 -79 -70 -32 50 191 391 North exterior window load 624 795 928 1028 1074 1067 1031 1039 1105 West exterior window load 1366 1740 2033 3198 5556 8158 10041 10500 9294 East skylight load 3194 2570 727 805 841 836 772 677 542 West skylight load 488 622 727 1143 1986 2915 3588 3753 3321 Internal wall load 0 0 0 0 0 0 0 0 0 Roof load -1358 1395 4631 8016 11219 13929 15880 16843 16708 <![CDATA[Cooling load Q in non-air-conditioned area 2,τ > 4147 7418 9462 14738 21390 27830 32505 34337 32883

[0197] Step 5: Calculate the hourly stratified air conditioning cooling load Q τ (W).

[0198] Exhaust air temperature:

[0199] Heat dissipation: Q p =C p ρV2n p (t p -t1) / 3600=1010×1.2×4071×0.65×(41.3-26) / 3600=13547W.

[0200] The final calculated hourly stratified air conditioning cooling load (W) is shown in Table 12 below.

[0201] Table 12 Hourly stratified air conditioning cooling load (W)

[0202] time 10 11 12 13 14 15 16 17 18 <![CDATA[Cooling load Q of the air-conditioned area 1,τ > 12313 13231 13558 14104 15030 16035 16811 17122 16892 <![CDATA[Cooling load Q of non-air-conditioned area 2,τ > 4147 7418 9462 14738 21390 27830 32505 34337 32883 <![CDATA[Heat rejection Q p > 13547 13547 13547 13547 13547 13547 13547 13547 13547 <![CDATA[Stratified air-conditioning cooling load Q τ > 2913 7102 9473 15294 22872 30317 35769 37911 36227

[0203] The maximum cooling load of downflow air is at 17:00, the cooling load of stratified air conditioning is 37911W, and the cooling load index is 76W / m 2 .

[0204] <Example 2>

[0205] This second embodiment provides a large-space hourly stratified air-conditioning cooling load calculation method, experimental verification, and hourly air-conditioning load calculation case applicable to large-area glass.

[0206] Large-area glass buildings differ from typical large-space buildings in that solar radiation can penetrate the glass in non-air-conditioned areas and enter the air-conditioned areas, creating a solar radiation heat transfer load. This is addressed by factoring in the solar radiation heat transfer load when calculating the cooling load in the air-conditioned area and the initial cooling load in the non-air-conditioned area. The remaining steps are consistent with the calculation method in Example 1. Calculations in this invention show that when the transparent roof area ratio (the ratio of the transparent roof area, i.e., the glass area to the total roof area) is less than 30%, the relative error in the stratified air-conditioning load caused by considering the solar radiation heat transfer load is less than 5%. Solar radiation transmitted through the transparent vertical walls in the non-air-conditioned area has a smaller impact on heat transfer in the air-conditioned area. Calculations show that when the transparent roof area ratio is less than 30%, the relative error in the stratified air-conditioning load caused by considering the solar radiation heat transfer load remains within 5% for variations in the transparent vertical wall area ratio from 0% to 100% in the non-air-conditioned area. Therefore, no restriction is imposed on the transparent vertical wall area ratio in the non-air-conditioned area. When the transparent roof area ratio is greater than 30%, the error in the stratified air-conditioning load caused by considering the transparent vertical wall area is even smaller.

[0207] In summary, the present invention stipulates that when the transparent portion of the roof area is greater than 30%, the solar radiation heat transfer load must be considered. When the area ratio is less than 30%, the calculation method in Example 1 is directly used.

[0208] Figure 6 This is a flow chart of the method for calculating the hourly stratified air conditioning load in a large space with large glass areas in Example 2 of the present invention. The specific calculation steps are as follows:

[0209] Step T1: When the transparent area ratio of the roof is greater than 30%, calculate the hourly solar radiation heat transfer load Q SR,τ , hourly cooling load Q of air-conditioned area 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ .

[0210] For non-transparent envelope structures, the load is only the temperature difference heat transfer load, while the load of transparent envelope structures is composed of two parts: the temperature difference heat transfer load and the solar radiation load, as shown in Equations (17) and (18).

[0211] Q1w，τ =Q 1c，τ +Q 1R，τ (17)

[0212] Q 02w，τ =Q 02c，τ +Q 2R，τ (18)

[0213] Where Q 1w,τ , Q 02w,τ The hourly cooling load of the air-conditioned area enclosure structure and the initial hourly cooling load of the non-air-conditioned area enclosure structure are respectively, in W; Q 1c,τ , Q 02c,τ The hourly cooling load of the heat transfer of the temperature difference of the air-conditioned area enclosure and the initial hourly cooling load of the heat transfer of the temperature difference of the non-air-conditioned area enclosure are respectively, in W; Q 1R,τ , Q 2R,τ The hourly cooling load of solar radiation on the enclosure structures of the air-conditioned area and the non-air-conditioned area, respectively, in W.

[0214] Since the solar radiation load is basically not affected by the air temperature, the temperature difference in the non-air-conditioned area will only affect the hourly cooling load of the temperature difference heat transfer of the enclosure structure. Therefore, the initial solar radiation hourly cooling load Q 02R,τ and the actual hourly cooling load Q of the solar radiation in the non-air-conditioned area 2R,τ are consistent.

[0215] Calculate the hourly solar radiation heat transfer load Q according to formula (19): SR,τ :

[0216]

[0217] Where Q SR,τ is the hourly solar radiation heat transfer load of the non-air-conditioned area, unit is W; N is the number of transparent enclosure structures in the non-air-conditioned area; i is the i-th transparent enclosure structure in the non-air-conditioned area; Q 2R,i,τ is the hourly cooling load of the transparent enclosure structure of the i-th non-air-conditioned area by solar radiation, unit W; X i,空调区 is the angular coefficient of the transparent enclosure structure of the i-th non-air-conditioned area to the entire air-conditioned area.

[0218] After obtaining the hourly solar radiation heat transfer load, calculate the hourly cooling load Q of the air-conditioning area 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ , see equations (20) and (21).

[0219] Q 1，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ +Q SR，τ (20)

[0220] Q02，τ =Q 02w，τ +Q 02n，τ +Q 02x，τ -Q SR，τ (twenty one)

[0221] The parameters in the formula are consistent with the meanings of calculation formulas (5) and (6) in this embodiment.

[0222] According to the calculated hourly cooling load Q of the air-conditioned area 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ Calculate the design cooling load intensity q1 of the air-conditioned area and the initial design cooling load intensity q of the non-air-conditioned area 02 The cooling load intensity is calculated in accordance with the formulas (7) and (8) in step S1 of Example 1.

[0223] Step T2: Calculate the vertical indoor air temperature gradient ▽t.

[0224] Step T3, calculating the characteristic temperature t2 of the non-air-conditioned area.

[0225] Step T4, calculate the actual hourly cooling load Q of the non-air-conditioned area 2,τ .

[0226] Step T5: Calculate the hourly stratified air conditioning cooling load Q τ .

[0227] In the second embodiment, the above steps T2, T3, T4 and T5 are the same as the steps S2, S3, S4 and S5 of the calculation method in the first embodiment, and are not repeated here.

[0228] Experimental verification:

[0229] The feasibility of the present invention is experimentally verified in the following experimental environment.

[0230] Experimental environment: The experiment was conducted in the large space on the top floor of the Shanghai Stock Exchange (SSE). The large space is located from the 31st floor to the top 34th floor. The 31st floor is 177.5 meters high, and the 34th floor glass roof is 200 meters high. Therefore, the large space is 22.5 meters high, 69.8 meters long, and 24.3 meters wide, with an area of ​​approximately 1700 square meters. 2 . Figure 7This is an interior view of the large space on the top floor of the Shanghai Stock Exchange. The air flow organization is in the form of lower floor air supply, middle return air, and top exhaust. The air supply outlets include circular floor diffusers and slit-type air supply outlets. Floor convection radiators (i.e. window fans) are installed along the glass curtain wall floor to eliminate the heat and cold loads of the enclosing structure. The entire roof of this large space is a skylight, the south and north walls are exterior walls and are both glass curtain walls, and the east and west walls are interior walls. The specifications of the glass curtain wall and skylight are all insulated aluminum alloy windows with a thickness of 12mm 5Low-e+15Ar+5 (lower light transmittance) and a heat transfer coefficient of 2.00W / (m 2 ·K), the shading coefficient of the facade glass curtain wall is 0.38, the shading coefficient of the skylight is 0.30, and the window frame ratio (the ratio of the window frame area to the entire window area) is 20%.

[0231] Table 13 Basic structure and thermal performance parameters of indoor related enclosure structures

[0232]

[0233]

[0234] Considering the influence of airflow organization and solar radiation from different directions on the thermal environment, three vertical air temperature and humidity measurement lines are arranged (see Figure 8 and Figure 9 Each line has 8 measuring points in the vertical direction, each of which is tied to two balloon suspension ropes. The specific arrangement is shown in Figure 8 and Figure 9 The instruments used to measure the main parameters are shown in Table 14 below.

[0235] Table 14 Experimental instruments and their performance parameters

[0236]

[0237] All instruments were calibrated and calibrated in the laboratory before the experiment. This experiment was conducted over four days under summer operating conditions. Based on the variability of indoor thermal environment parameters during the summer, it was found that the indoor thermal environment generally stabilized after 2:00 PM each day. Therefore, 2:00 PM was designated as the steady-state time for the experiment. The experimental operating condition parameters were the steady-state parameters at the time each condition reached stability (i.e., 2:00 PM). They were directly measured or calculated at the experimental site and are shown in Table 15. During these four days, the only indoor heat sources were the experimenters and approximately ten staff members; no other indoor heat sources were present.

[0238] Table 15 Experimental conditions

[0239]

[0240]

[0241] Based on the experimentally measured air-conditioned zone temperatures in Table 15, the solar radiation heat transfer load, the cooling load and intensity of the air-conditioned zone, and the initial cooling load and intensity of the non-air-conditioned zone can be calculated. The calculation results are shown in Table 16. Then, based on the downward air supply empirical formula (10), the characteristic temperature of the non-air-conditioned zone for these four experimental working conditions can be calculated. The calculated values ​​of the characteristic temperature of the non-air-conditioned zone are compared with the experimental values ​​in Table 17, where the experimental value is the average value of the measured temperature of all measuring points in the non-air-conditioned zone. From the data in Table 17, it can be seen that for the four working conditions (working conditions C1 to C4), the mean absolute error (MAE) between the calculated values ​​and the experimental values ​​of the characteristic temperature of the non-air-conditioned zone is 0.9°C, and the mean absolute relative error (MAPE) is 2.7%. This shows that the calculation method of Example 2 of the present invention has a high reliability in predicting the characteristic temperature of the non-air-conditioned zone in an actual large-area glass and large space.

[0242] Table 16 Calculation results of cooling load and intensity in air-conditioned and non-air-conditioned areas

[0243]

[0244] Table 17 Comparison of calculated and experimental characteristic temperatures in non-air-conditioned areas

[0245] Working conditions Calculated value / ℃ Experimental value / ℃ Absolute error / ℃ Relative error C1 33.5 32.4 1.1 3.4％ C2 33.8 33.4 0.4 1.2％ C3 34.9 34.2 0.7 2.2％ C4 34.4 33.1 1.3 3.9％

[0246] Since the calculation is based on the experimental data of the stable time period, only the steady-state stratified air conditioning cooling load is verified here. After obtaining the characteristic temperature of the non-air-conditioned area, the calculated value of the stratified air conditioning cooling load is obtained according to formula (14), and it is compared with the experimental cooling capacity. The experimental cooling capacity can be calculated by the experimentally measured supply air volume and supply and return air temperatures. The comparison results are shown in Figure 10 The comparison results show that the average absolute error (MAE) between the calculated stratified air conditioning cooling load and the experimental cooling capacity for the four experimental conditions is 7.8 kW, and the average absolute relative error (MAPE) is 2.4%. This shows that the calculation method proposed in this paper can quickly and accurately solve the actual stratified air conditioning cooling load for large spaces with large glass areas.

[0247] Calculation example:

[0248] After verifying the feasibility of this method through the above experiments, this second embodiment provides a calculation case for the stratified air conditioning load in a large space with large glass areas. The case object is still the large space on the top floor of the Shanghai Stock Exchange used in the experimental verification. The calculation conditions are as follows: there are 50 people inside the building, the activity intensity is very light, and the lighting power density is 5W / m 2, while the use coefficient = 1.0, no equipment is in operation, personnel are in the air-conditioned area, lighting is in the non-air-conditioned area, and working hours are from 10:00 to 18:00. The outdoor meteorological parameters adopt the Shanghai summer design parameters, the outdoor dry bulb temperature is 34.4℃, and the outdoor daily average temperature is 30.8℃. The design temperature t1 of the air-conditioned area is 26℃, and the design temperature of the adjacent room is also 26℃. The number of exhaust times in the non-air-conditioned area is n p =1 time / hour. The calculation conditions in this article refer to the "Practical Heating and Air Conditioning Design Manual" (Second Edition) and the "Code for Design of Heating, Ventilation, and Air Conditioning for Civil Buildings" (GB 50736-2012). The goal is to calculate the hourly, stratified air conditioning cooling load during the working hours of 10:00 AM to 6:00 PM.

[0249] Step 1: When the transparent area ratio of the roof is greater than 30%, calculate the hourly solar radiation heat transfer load Q SR,τ , hourly cooling load Q of air-conditioned area 1,τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ (W).

[0250] Since the entire roof of the large space on the top floor of the Shanghai Stock Exchange is a skylight, the window frame ratio (the ratio of the window frame area to the entire window area) is 20%, so the transparent area ratio of the roof is 80%. This value is greater than 30%, so it is necessary to calculate the hourly solar radiation heat transfer load Q using formula (19): SR,τ , where the angular coefficients of the transparent enclosure structures in the non-air-conditioned area to the entire air-conditioned area are shown in Table 18 below. Based on the design temperature t1 of the air-conditioned area being 26°C and the stratification height being 15m, the hourly cooling loads for the air-conditioned and non-air-conditioned areas are calculated using Equations (20) and (21), respectively. The calculation results are shown in Tables 19 and 20 below.

[0251] Table 18 Angle coefficient of transparent enclosure structure in non-air-conditioned area to air-conditioned area

[0252] Skylight angle coefficient to air-conditioning area Angle coefficient of north curtain wall to air-conditioning area Angle coefficient of south curtain wall to air-conditioning area 0.68 0.37 0.37

[0253] Table 19 Hourly cooling load of each air-conditioning zone (W)

[0254]

[0255]

[0256] Table 20 Initial hourly cooling loads of non-air-conditioned areas (W)

[0257]

[0258] Then calculate the design cooling load intensity of the air-conditioned area and the initial design cooling load intensity of the non-air-conditioned area (W / m 3 ).

[0259] Design cooling load intensity of air-conditioning area:

[0260] Initial design cooling load intensity of non-air-conditioned area:

[0261] Step 2: Calculate the vertical indoor air temperature gradient (℃ / m)

[0262] Number of air changes in non-air-conditioned areas: n p =1 time / h; building height: H=22.5m.

[0263] According to formula (10), the vertical temperature gradient of air is obtained 0.57℃ / m:

[0264]

[0265]

[0266] Step 3: Calculate the characteristic temperature t2 (°C) of the non-air-conditioned area:

[0267]

[0268] Step 4: Calculate the actual hourly cooling load Q of the non-air-conditioned area based on the characteristic temperature t2 of the non-air-conditioned area of ​​32.4°C. 2,τ (W), the results are shown in Table 21. In this embodiment, the adjacent room is an office with a design temperature of 26°C, so the temperature difference between the adjacent rooms in the non-air-conditioned area is -6.4°C.

[0269] Table 21 Actual hourly cooling load of non-air-conditioned areas (W)

[0270]

[0271] Step 5: Calculate the hourly stratified air conditioning cooling load Q τ (W):

[0272] Exhaust air temperature:

[0273] Heat dissipation: Q p =C p ρV2n p (t p -t1) / 3600=1010×1.2×12721×1×(34.5-26) / 3600=36612W.

[0274] The final calculated hourly stratified air conditioning cooling load (W) is shown in Table 22 below:

[0275] time 10 11 12 13 14 15 16 17 18 <![CDATA[Cooling load Q of the air-conditioned area 1,τ > 237882 266643 276322 268649 242117 203215 151375 101774 56698 <![CDATA[Cooling load Q of non-air-conditioned area 2,τ > 89276 105521 112019 110670 100731 84511 61167 38112 17087 <![CDATA[Heat rejection Q p > 36612 36612 36612 36612 36612 36612 36612 36612 36612 <![CDATA[Hierarchical air-conditioning cooling load Q τ > 290546 335552 351729 342707 306236 251114 175930 103274 37173

[0276] The maximum cooling load of the large space on the top floor of the Shanghai Stock Exchange is at 12:00, the cooling load of the stratified air conditioning is 351729W, and the cooling load index is 207W / m 2 .

[0277] Example Function and Effect

[0278] The method for calculating the hourly stratified air conditioning cooling load for large-space buildings provided in this embodiment addresses the current lack of a mature and complete method for calculating the hourly stratified air conditioning cooling load for large spaces, both domestically and internationally. Based on the principle of thermal balance, this method, suitable for engineering applications, addresses the two commonly used stratified air conditioning methods: center- and bottom-of-nozzle air supply. The calculation conditions required by this method are consistent with those for calculating the cooling load for whole-room air conditioning. It simply divides the large space into air-conditioned and non-air-conditioned areas based on the stratified air conditioning height. The cooling loads for the air-conditioned and initial non-air-conditioned areas are then calculated based on the air-conditioned area design temperature. The empirical formula proposed in this invention is then used to calculate the characteristic temperature of the non-air-conditioned area and the actual non-air-conditioned area cooling load, thereby determining the hourly stratified air conditioning cooling load.

[0279] Considering that large-area glass buildings can generate solar radiation heat transfer loads by transmitting solar radiation through non-air-conditioned glass into air-conditioned areas, this embodiment also proposes a method for calculating the hourly, stratified air-conditioning cooling load for large spaces with large glass areas. This method also considers solar radiation heat transfer loads when calculating the cooling load for the air-conditioned area and the initial cooling load for the non-air-conditioned area, especially when the transparent roof area ratio of a large space with large glass areas is greater than 30%. This improves applicability and expands its scope. Furthermore, since the characteristic temperature of the non-air-conditioned area takes into account more influencing factors, it is more realistic.

[0280] In summary, compared to traditional methods, the hourly cooling load calculation method for stratified air conditioning in large-space buildings in this embodiment solves the problem of only being able to perform steady-state calculations for stratified air conditioning, resulting in loads that are inconsistent with reality. This provides air conditioning designers with a more robust numerical basis for design, ultimately ensuring that the cooling capacity provided by the stratified air conditioning system design is more realistic. Furthermore, this method is easier for designers to use and meets the requirements for hourly cooling load calculations in summer.

[0281] The above embodiments are only used to illustrate specific implementations of the present invention, and the present invention is not limited to the description scope of the above embodiments.

Claims

1. A method for calculating the hourly stratified air conditioning cooling load of a large-space building, which is applied to calculate the hourly stratified air conditioning cooling load of a large-space building using stratified air conditioning, and is characterized by: The following steps are involved: Step S1, based on the design temperature of the large space air-conditioned area and relevant indoor and outdoor design parameters, calculate the hourly cooling load of the air-conditioned area and the initial hourly cooling load of the non-air-conditioned area according to the whole-room air-conditioning cooling load calculation method, and calculate the corresponding design cooling load intensity respectively; Step S2, calculating the indoor air temperature gradient in the vertical direction of the large space based on the design cooling load intensity of the air-conditioned area and the non-air-conditioned area; Step S3, calculating the characteristic temperature of the non-air-conditioned area according to the indoor air temperature gradient; Step S4, calculating the actual hourly cooling load of the non-air-conditioned area based on the characteristic temperature of the non-air-conditioned area; Step S5: subtract the hourly heat rejection from the sum of the hourly cooling load of the air-conditioned area and the actual hourly cooling load of the non-air-conditioned area, thereby solving the hourly stratified air-conditioning cooling load of the large space building.

2. The method for calculating the hourly and stratified air conditioning cooling load of a large-space building according to claim 1 is characterized in that: in, In step S1, when the large-space building is a large-area glass building, the transparent portion area ratio of the roof of the large-space building, that is, the ratio of the glass area to the entire roof area, needs to be calculated. When the transparent portion area ratio of the roof is less than 30%, the calculation formula for the hourly cooling load of the air-conditioned zone is as follows: Q 1，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ The calculation formula for the initial hourly cooling load of the non-air-conditioned area is as follows: Q 02,τ =Q 02w,τ +Q 02n,τ +Q 02x,τ Where Q 1,τ , Q 02,τ They are the hourly cooling load of the air-conditioned area and the initial hourly cooling load of the non-air-conditioned area, in W; Q 1w,τ , Q 1n,τ , Q 1x,τ The hourly cooling loads generated by the air-conditioning area enclosure structure, internal heat source, and outdoor fresh air or infiltration wind are respectively, in W; Q 02w,τ , Q 02n,τ , Q 02x,τ are the initial hourly cooling loads generated by the envelope structure, internal heat source, and outdoor fresh air or infiltration air in the non-air-conditioned area, respectively, in W. The hourly cooling load of the air-conditioned area generated by the envelope structure, internal heat source, fresh air or infiltration air and the initial hourly cooling load of the non-air-conditioned area are calculated according to relevant air-conditioning design manuals or air-conditioning load calculation software.

3. A method for calculating the hourly and layered air conditioning cooling load of a large-space building according to claim 2, Its characteristics are: Wherein, in the step S1, when the transparent portion area ratio of the roof of the large-space building is greater than 30%, the hourly solar radiation heat transfer load needs to be considered. The process of obtaining the hourly solar radiation heat transfer load is as follows: For non-transparent enclosure structures, the load only includes the temperature difference heat transfer load, while the load for transparent enclosure structures is composed of the temperature difference heat transfer load and the solar radiation load. Therefore, the calculation formulas for the hourly cooling load of the air-conditioned area enclosure structure and the initial hourly cooling load of the non-air-conditioned area enclosure structure are as follows: Q 1w，τ =Q 1c，τ +Q 1R，τ Q 02w，τ =Q 02c，τ +Q 2R，τ Where Q 1w,τ , Q 02w,τ The hourly cooling load of the air-conditioned area enclosure structure and the initial hourly cooling load of the non-air-conditioned area enclosure structure are respectively, in W; Q 1c,τ , Q 02c,τ The hourly cooling load of the heat transfer of the temperature difference of the air-conditioned area enclosure and the initial hourly cooling load of the heat transfer of the temperature difference of the non-air-conditioned area enclosure are respectively, in W; Q 1R,τ , Q 2R,τ They are respectively the hourly cooling load of solar radiation of the enclosure structure of the air-conditioned area and the hourly cooling load of solar radiation of the enclosure structure of the non-air-conditioned area, unit is W; Since the solar radiation load is basically not affected by the air temperature, the temperature difference in the non-air-conditioned area will only affect the hourly cooling load of the temperature difference heat transfer of the enclosure structure. Therefore, the initial solar radiation hourly cooling load Q 02R,τ and the actual hourly cooling load Q of the solar radiation in the non-air-conditioned area 2R,τ are consistent, so the calculation formula for the hourly solar radiation heat transfer load in the non-air-conditioned area is as follows: Where Q SR,τ is the hourly solar radiation heat transfer load of the non-air-conditioned area, unit is W; N is the number of transparent enclosure structures in the non-air-conditioned area; i is the i-th transparent enclosure structure in the non-air-conditioned area; Q 2R,i,τ is the hourly cooling load of the transparent enclosure structure of the i-th non-air-conditioned area by solar radiation, unit W; X i,空调区 is the angular coefficient of the transparent enclosure structure of the i-th non-air-conditioned area to the entire air-conditioned area; Based on the hourly solar radiation heat transfer load calculated above, the hourly cooling load Q1 of the air-conditioning area is calculated respectively. τ and the initial hourly cooling load Q of the non-air-conditioned area 02,τ , see the following formula: Q 1，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ +Q SR，τ Q 02，τ =Q 02w，τ +Q 02n，τ +Q 02x，τ -Q SR，τ 。 4. A method for calculating the hourly and layered air conditioning cooling load of a large-space building according to claim 3, Its characteristics are: In step S1, the calculation formulas for the design cooling load intensity of the air-conditioned area and the initial design cooling load intensity of the non-air-conditioned area are as follows: Where q1 is the design cooling load intensity of the air-conditioning area, W / m 3 ;q 02 Initial design cooling load intensity for non-air-conditioned areas, unit: W / m 3 ; Q1 is the design cooling load of the air-conditioning area, which is the hourly cooling load Q of the air-conditioning area 1,τ Peak load in W; Q 02 is the initial design cooling load of the non-air-conditioned area, and is the initial hourly cooling load Q of the non-air-conditioned area. 02,τ The peak load in the unit is W; V1 and V2 are the volumes of the air-conditioned area and the non-air-conditioned area, respectively, in m 3 .

5. The method for calculating the hourly and stratified air conditioning cooling load of a large-space building according to claim 4 is characterized in that: in, In step S2, the indoor air temperature gradient is calculated according to the following empirical formula: Central nozzle air supply stratified air conditioning: Downward air supply stratified air conditioning: Where, is the indoor air temperature gradient in the vertical direction, unit is ℃ / m; n p is the number of exhaust times in the non-air-conditioned area, unit: times / h; H is the building height, unit: m.

6. The method for calculating the hourly and stratified air conditioning cooling load of a large-space building according to claim 5 is characterized in that: in, In step S3, the calculation formula of the characteristic temperature of the non-air-conditioned area is: Where t1 and t2 are the design temperature of the air-conditioned area and the characteristic temperature of the non-air-conditioned area, respectively, in °C; h1 and h2 are the heights of the air-conditioned area and the non-air-conditioned area, respectively, in m.

7. The method for calculating the hourly and stratified air conditioning cooling load of a large-space building according to claim 6 is characterized in that: in, In step S5, the hourly heat dissipation is related to the exhaust temperature of the non-air-conditioned area. The exhaust temperature is determined by the characteristic temperature t2 of the non-air-conditioned area. Therefore, the hourly heat dissipation is approximately a steady-state value. The calculation formulas for the exhaust temperature and the heat dissipation are as follows: Where, t p is the exhaust temperature, unit is ℃; Δh p The height difference between the exhaust center plane and the non-air-conditioned area center plane, unit is m; h p is the exhaust height, in meters; if the exhaust is located at the top of the building, it is equal to the building height H; Q p =C p ρV2n p (t p -t1) / 3600 Where Q p Heat dissipated from non-air-conditioned areas, unit: W; C p is the specific heat capacity of air at constant pressure, in J / (kg·℃); ρ is the air density, in kg / m 3 ; The solution formula for the hourly stratified air conditioning cooling load of the large space building is as follows: Q τ =Q 1，τ +Q 2，τ -Q p，τ =Q 1w，τ +Q 1n，τ +Q 1x，τ +Q 2w，τ +Q 2n，t +Q 2x，τ -Q p，τ Where Q τ is the hourly stratified air conditioning cooling load, unit is W; Q 1,τ is the hourly cooling load of the air-conditioning zone, unit is W; Q2, τ is the actual hourly cooling load of the non-air-conditioned area, unit: W; Q p , τ The heat dissipated hourly, unit is W; Q 2w,τ , Q 2n,τ , Q 2x,τ They are the hourly cooling loads generated by the actual non-air-conditioned area enclosure structure, internal heat source, and outdoor fresh air or infiltration air, in W.

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