| Unlike common buildings,the height of area where personnel activities in large space buildings are much lower than its height.Therefore,compared with full-room airconditioning,the stratified air-conditioning is more suitable for large space buildings.The most commonly used stratified air-conditioning are the form of nozzle air supply and lowsidewall air supply systems.The accurate calculation of stratified air-conditioning load is the basis of design and optimization for large space buildings,and its value is also the key to measure the energy saving of stratified air-conditioning.Many studies found that stratified air-conditioning load for large space buildings are affected by the indoor thermal and humidity environment,while the indoor environment is affected by the supply air volume of air-conditioning.The supply air volume of stratified air-conditioning is given as a known parameter in the existing indoor thermal and humidity environment prediction model,and the stratified air-conditioning load calculated based the form of nozzle air supply or low-sidewall air supply is sensible heat load,while it without considering the latent heat load.Compared with actual project,the above method does not consider the influence of indoor moisture dissipation,and the supply air volume of comfortable air conditioning is calculated by air-conditioning load,which makes the model calculation derailed from the actual engineering design.In order to solve the above problems,the temperature prediction model was modified to air enthalpy prediction model which considering the moisture dissipation in a scale model laboratory.This scale model laboratory operates under the low-sidewall air supply organization.The moisture transfer equilibrium equation in large space building was established in this paper.Based on this,a four-area Block-Gebhart model which considering the effects of internal heat source,exhaust air ratio and indoor moisture dissipation was established.The model that established in this paper made the supply air volume synchronously calculated with the indoor thermal and humidity environment and stratified air-conditioning load.This synchronization calculation method allows the above three values to be calculated simultaneously,and it makes the supply air volume that assumed in the calculation of indoor thermal environment coincide with the air supply volume calculated by the stratified air-conditioning load.Based on the research purpose of this paper,the research contents and results are as follows.1.This paper took a scale model laboratory which operations the low-sidewall air supply as research object.A four-area Block-Gebhart model that considered the effects of internal heat source,exhaust air and indoor moisture dissipation was established.Based on this,the calculation method that the supply air volume synchronously calculated with the indoor thermal and humidity environment and stratified air-conditioning load was proposed.2.The theoretical results that calculated by B-G modified model are compared with the experiment parameters under different experimental conditions.The results show that the theoretical values are in good agreement with experimental values.The ranges of relative errors between experimental and theoretical values of supply air volume,indoor vertical air temperatures and inner wall temperatures are respectively from 2.03% to 11.37%,-2.75% to 2.90% and-5.27% to 2.24%.The ranges of relative errors between experimental and theoretical values of indoor air enthalpy under the eight experimental conditions from-3.02 % to 4.73 %.3.The stratified air-conditioning load which calculated based on the results of indoor thermal environment parameters that calculated by B-G modified model and compared with experimental values.The relative errors between the experimental and theoretical values of radiative and convective heat transfer loads,and stratified air-conditioning load are respectively ranging from-7.20% to 9.16%,-6.92% to 5.60% and-1.48 %to 6.34 %.The results clearly indicate that the four-area B-G modified model established in this paper has good correctness and reliability in the calculation of indoor thermal and humidity environment and stratified air-conditioning load.4.Using the theoretical model that established in the paper,the indoor thermal environment parameters and stratified air-conditioning load under the low-sidewall air supply of large space building were calculated with different influencing factors,such as exhaust ratio,indoor heat source power,indoor heat source height and temperature of air-conditioning area.The calculation results are as follows.a)The air supply air volume,indoor air temperature,inner wall temperature,the radiative and convective heat transfer loads,and stratified air-conditioning load all decreased correspondingly with the increases of exhaust air ratio.Among the air-conditioning load,the radiative heat transfer load decreases least with the increase of exhaust air ratio,while the proportion of convective heat transfer load is reduced from 23.31 % to 17.05 %.b)The supply air volume,indoor air temperature,inner wall temperature,indoor air enthalpy,radiative and convective heat transfer loads,and stratified airconditioning load all increased correspondingly with the increases of internal heat source power.The proportion of radiative and convective heat transfer load are respectively increased from 26.60 % to 28.37 % and 16.29 % to 21.44 %.c)With the increases of internal heat source height,the supply air volume and the indoor air enthalpy all remained basically unchanged.The radiative heat transfer load increased,while there are no regular changes of convective heat transfer load.d)With the increase of temperature of air-conditioning area,the supply air volume gradually decreased.The indoor air temperature,inner wall temperature and indoor air enthalpy all decreased correspondingly with the increase of temperature of air-conditioning area.With the increase of air-conditioning temperature,the stratified air-conditioning load is almost unchanged,the radiative heat transfer load tends to increase,while the convective heat transfer load is gradually decreased.The proportion of radiative heat transfer load is increased from 29.84% to 33.42%,while the proportion of convective heat transfer load is reduced from 18.94 % to 15.75 %.As we can see from above,the four-area Block-Gebhart modified model established in this paper has good correctness and reliability in the calculation of indoor thermal and humidity environment and stratified air-conditioning load.Although there are still many aspects to be improved in the research content of this paper,the research contents also make up for the shortcomings of the previous research group.The results of this research will provide references for the application of stratified air-conditioning load calculation with low-sidewall air supply for large space building. |
PDF Full Text Request