The wide application of evaporative cooling techniques in which the optimization criteria form the theoretical basis for improving evaporative cooling performance is essential for energy conservation and emission redu...The wide application of evaporative cooling techniques in which the optimization criteria form the theoretical basis for improving evaporative cooling performance is essential for energy conservation and emission reduction.Based on exergy analysis and the entransy dissipation-based thermal resistance method,this contribution aims to investigate the effects of flow and area distributions in the optimization of the performance of indirect evaporative cooling systems.We first establish the relationships of exergy efficiency,entransy dissipation-based thermal resistance and cooling capacity of a typical indirect cooling system.Using the prescribed inlet parameters,the heat and mass transfer coefficients and the circulating water mass flow rate,we then numerically validate that when the cooling capacity reaches a maximum,the entransy dissipation-based thermal resistance falls to a minimum while the exergy efficiency is not at an extreme value.The result shows that the entransy dissipation-based thermal resistance,not the exergy efficiency,characterizes the heat transfer performance of an evaporative cooling system,which provides a more suitable method for evaluating and analyzing the indirect cooling system.展开更多
A new evaporative cooling system based on the action of centrifugal forces is proposed.Such systems are suitable for cooling large air volumes in tropical climates.Effects of geometrical and operational parameters on ...A new evaporative cooling system based on the action of centrifugal forces is proposed.Such systems are suitable for cooling large air volumes in tropical climates.Effects of geometrical and operational parameters on system performance are optimized using Taguchi method.It is observed that disc speed,air flow rate and water flow rate are found to have major influence on system performance and other parameter,viz.,disc diameter,pin geometry,evaporation chamber length and orientation of pin have less influence.展开更多
Cooling is very important for the safe operation of an electron cyclotron resonance ion source(ECRIS),especially when the window current density is very high(up to 11 A/mm2).We proposed an innovative cooling method us...Cooling is very important for the safe operation of an electron cyclotron resonance ion source(ECRIS),especially when the window current density is very high(up to 11 A/mm2).We proposed an innovative cooling method using evaporative cooling technology.A demonstration prototype was designed,built and tested.The on-site test results showed that the temperature of the solenoids and permanent magnets maintains well in the normal operational range of 14–18 GHz.A simple computational model was developed to predict the characteristics of the two-phase flow.The predicted temperatures agreed well with the on-site test data within 2 K.We also proposed useful design criteria.The successful operation of the system indicates the potential for broad application of evaporative cooling technology in situations in which the power intensity is very high.展开更多
The transpiration cooling control system of the thermal protective shield with surface ablation is a nonlinear control system of distributed parameter with moving boundary.As far as the boundary conditions the third k...The transpiration cooling control system of the thermal protective shield with surface ablation is a nonlinear control system of distributed parameter with moving boundary.As far as the boundary conditions the third kind and a one-dimensional incompressible coolant flow under constant transpiration mass flux are concerned,this paper transforms the definite solution problem into the second-type Volterra integral equations,and applies them directly to compute the shield ablation law.Investigation of the system's control by transpiration mass flux,ablation amount and ablation velocity varying with time,time of the ablation's beginning and ending,etc.,are presented.展开更多
Passive strategies for acclimatization of buildings have been studied by several authors in many countries, especially the evaporative and radiant cooling techniques. Fiber cement tiles are very common in popular cons...Passive strategies for acclimatization of buildings have been studied by several authors in many countries, especially the evaporative and radiant cooling techniques. Fiber cement tiles are very common in popular constructions due to their low cost. However, they have over twice of the value thermal transmittance indicated to this bioclimatic zone according to Brazilian guidelines. The objective is to present an alternative to reduce high temperatures on fiber cement tiles. In this paper, the monitoring of passive cooling of roofing during the spring season in a city with subtropical climate is described. Single and combined reflective and evaporative cooling systems were studied in different environmental conditions. Internal surface temperatures of tiles were monitored together with weather variables. Results show a decrease of about 6 ℃, 9 ℃, 10 ℃ and 11 ℃ as compared to the original tiles according to environment conditions and the combined passive cooling techniques. These results allow for the conclusion that the use of passive cooling techniques opens up new possibilities to attenuate the internal surface temperatures of tiles and to consequently decrease the roofing solar heat gain into buildings, thus, providing less air cooling energy consumption.展开更多
基金supported by the National Natural Science Foundation of China (51006060)
文摘The wide application of evaporative cooling techniques in which the optimization criteria form the theoretical basis for improving evaporative cooling performance is essential for energy conservation and emission reduction.Based on exergy analysis and the entransy dissipation-based thermal resistance method,this contribution aims to investigate the effects of flow and area distributions in the optimization of the performance of indirect evaporative cooling systems.We first establish the relationships of exergy efficiency,entransy dissipation-based thermal resistance and cooling capacity of a typical indirect cooling system.Using the prescribed inlet parameters,the heat and mass transfer coefficients and the circulating water mass flow rate,we then numerically validate that when the cooling capacity reaches a maximum,the entransy dissipation-based thermal resistance falls to a minimum while the exergy efficiency is not at an extreme value.The result shows that the entransy dissipation-based thermal resistance,not the exergy efficiency,characterizes the heat transfer performance of an evaporative cooling system,which provides a more suitable method for evaluating and analyzing the indirect cooling system.
文摘A new evaporative cooling system based on the action of centrifugal forces is proposed.Such systems are suitable for cooling large air volumes in tropical climates.Effects of geometrical and operational parameters on system performance are optimized using Taguchi method.It is observed that disc speed,air flow rate and water flow rate are found to have major influence on system performance and other parameter,viz.,disc diameter,pin geometry,evaporation chamber length and orientation of pin have less influence.
基金supported by the Open Research Project of the Major Science and Technology Infrastructure in the Chinese Academy of Sciences-Application of Evaporative Cooling Technology in the Field of Accelerator
文摘Cooling is very important for the safe operation of an electron cyclotron resonance ion source(ECRIS),especially when the window current density is very high(up to 11 A/mm2).We proposed an innovative cooling method using evaporative cooling technology.A demonstration prototype was designed,built and tested.The on-site test results showed that the temperature of the solenoids and permanent magnets maintains well in the normal operational range of 14–18 GHz.A simple computational model was developed to predict the characteristics of the two-phase flow.The predicted temperatures agreed well with the on-site test data within 2 K.We also proposed useful design criteria.The successful operation of the system indicates the potential for broad application of evaporative cooling technology in situations in which the power intensity is very high.
文摘The transpiration cooling control system of the thermal protective shield with surface ablation is a nonlinear control system of distributed parameter with moving boundary.As far as the boundary conditions the third kind and a one-dimensional incompressible coolant flow under constant transpiration mass flux are concerned,this paper transforms the definite solution problem into the second-type Volterra integral equations,and applies them directly to compute the shield ablation law.Investigation of the system's control by transpiration mass flux,ablation amount and ablation velocity varying with time,time of the ablation's beginning and ending,etc.,are presented.
文摘Passive strategies for acclimatization of buildings have been studied by several authors in many countries, especially the evaporative and radiant cooling techniques. Fiber cement tiles are very common in popular constructions due to their low cost. However, they have over twice of the value thermal transmittance indicated to this bioclimatic zone according to Brazilian guidelines. The objective is to present an alternative to reduce high temperatures on fiber cement tiles. In this paper, the monitoring of passive cooling of roofing during the spring season in a city with subtropical climate is described. Single and combined reflective and evaporative cooling systems were studied in different environmental conditions. Internal surface temperatures of tiles were monitored together with weather variables. Results show a decrease of about 6 ℃, 9 ℃, 10 ℃ and 11 ℃ as compared to the original tiles according to environment conditions and the combined passive cooling techniques. These results allow for the conclusion that the use of passive cooling techniques opens up new possibilities to attenuate the internal surface temperatures of tiles and to consequently decrease the roofing solar heat gain into buildings, thus, providing less air cooling energy consumption.
