Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5188778
R. Gomri
Water lithium bromide vapour absorption cooling systems, both single and double effect, are being used extensively for air conditioning. However, relatively few works are available on triple effect absorption cooling system and the published literatures are silent on the exergetic analysis of this system. This paper deals with the exergy analysis of the triple-effect LiBr-water absorption refrigerating system. The exergy analysis is carried out for each component of the system. All exergy losses that exist in triple effect lithium bromide/water absorption system are calculated. In addition to the coefficient of performance and the exergetic efficiency of the system, the number of exergy of each component of the system is also estimated. The effect of HPG temperature was analysed for a commonly used chilled water temperature (12° C/7°C). The maximum coefficient of performance (COP) and exergy efficiency (?exergy), are obtained for a maximum value of LPG and MPG temperatures. For a given MPG temperature there is an interval of LPG temperature for which the triple effect absorption cooling system can operate. Out from this interval of temperature the system does not function any more. For commonly used condenser and absorber cooling water temperature (25°C/30°C) and chilled water temperature (12°C/7°C) the maximum exergetic efficiency value of the triple effect refrigeration system is about 35.1 % Triple-effect chillers can achieve even higher efficiencies than the double-effect chillers. These chillers require still higher elevated operating temperatures that can limit choices in materials and refrigerant/absorbent pairs. The second law analysis used in this study facilitates the identification of the system components with high exergy loss. The results of the exergy analysis presented in this paper can be used in thermo-economic optimization of triple effect absorption cooling system.
{"title":"Thermodynamic evaluation of triple effect absorption chiller","authors":"R. Gomri","doi":"10.1109/THETA.2008.5188778","DOIUrl":"https://doi.org/10.1109/THETA.2008.5188778","url":null,"abstract":"Water lithium bromide vapour absorption cooling systems, both single and double effect, are being used extensively for air conditioning. However, relatively few works are available on triple effect absorption cooling system and the published literatures are silent on the exergetic analysis of this system. This paper deals with the exergy analysis of the triple-effect LiBr-water absorption refrigerating system. The exergy analysis is carried out for each component of the system. All exergy losses that exist in triple effect lithium bromide/water absorption system are calculated. In addition to the coefficient of performance and the exergetic efficiency of the system, the number of exergy of each component of the system is also estimated. The effect of HPG temperature was analysed for a commonly used chilled water temperature (12° C/7°C). The maximum coefficient of performance (COP) and exergy efficiency (?exergy), are obtained for a maximum value of LPG and MPG temperatures. For a given MPG temperature there is an interval of LPG temperature for which the triple effect absorption cooling system can operate. Out from this interval of temperature the system does not function any more. For commonly used condenser and absorber cooling water temperature (25°C/30°C) and chilled water temperature (12°C/7°C) the maximum exergetic efficiency value of the triple effect refrigeration system is about 35.1 % Triple-effect chillers can achieve even higher efficiencies than the double-effect chillers. These chillers require still higher elevated operating temperatures that can limit choices in materials and refrigerant/absorbent pairs. The second law analysis used in this study facilitates the identification of the system components with high exergy loss. The results of the exergy analysis presented in this paper can be used in thermo-economic optimization of triple effect absorption cooling system.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125668556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167198
M. Serag-Eldin
The paper is concerned with the ventilation and cooling of a typical gym environment, and compares the results obtained when supply-air is introduced from a bottom side-vent against those obtained when supply-air is introduced through the ceiling. The results are predicted employing a mathematical model comprising three-dimensional governing partial differential equations expressing balance of momentum in three Cartesian-coordinate directions, conservation of mixture and species mass, conservation of energy, and transport equations for the kinetic energy of turbulence and its rate of dissipation. The turbulence model employed is the ldquorenormalization grouprdquo derived ldquok-epsivrdquo model. Special attention is paid to the simulation of heat and pollutant releases from persons and exercise machines in order to make the predictions realistic. It is revealed that for the same energy expenditure, the bottom-side entry of the supply-air produces substantially superior air-quality to that of the conventional ceiling-entry.
{"title":"Comparison between near-floor and ceiling supply-air entry for GYM ventilation","authors":"M. Serag-Eldin","doi":"10.1109/THETA.2008.5167198","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167198","url":null,"abstract":"The paper is concerned with the ventilation and cooling of a typical gym environment, and compares the results obtained when supply-air is introduced from a bottom side-vent against those obtained when supply-air is introduced through the ceiling. The results are predicted employing a mathematical model comprising three-dimensional governing partial differential equations expressing balance of momentum in three Cartesian-coordinate directions, conservation of mixture and species mass, conservation of energy, and transport equations for the kinetic energy of turbulence and its rate of dissipation. The turbulence model employed is the ldquorenormalization grouprdquo derived ldquok-epsivrdquo model. Special attention is paid to the simulation of heat and pollutant releases from persons and exercise machines in order to make the predictions realistic. It is revealed that for the same energy expenditure, the bottom-side entry of the supply-air produces substantially superior air-quality to that of the conventional ceiling-entry.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128055779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167185
M. Speetjens
Further development in cutting-edge technologies becomes increasingly reliant upon the ability for massive heat removal. Boiling heat transfer offers the cooling capacity required by such emerging technologies. However, phase-change cooling schemes based on boiling heat transfer typically have two important limitations. First, high uncertainty in predicting the so-called ldquocritical heat fluxrdquo (CHF) that determines the maximum heat-removal capacity. Second, the inability to actively respond to fluctuating cooling demands due to the passive working principle. The present study seek to contribute to the advancement of phase-change cooling schemes by model-based development of control strategies that safely facilitate efficient boiling heat transfer close to CHF under dynamic operating conditions. These control strategies can be developed by means of a compact 3D model that describes the system-level dynamics of pool-boiling processes entirely in terms of the heat distribution within the heat-generating device. The compact 3D model and how to utilise it for the development of control strategies are the topics of this paper.
{"title":"Controlled pool boiling: A way for high-performance cooling schemes?","authors":"M. Speetjens","doi":"10.1109/THETA.2008.5167185","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167185","url":null,"abstract":"Further development in cutting-edge technologies becomes increasingly reliant upon the ability for massive heat removal. Boiling heat transfer offers the cooling capacity required by such emerging technologies. However, phase-change cooling schemes based on boiling heat transfer typically have two important limitations. First, high uncertainty in predicting the so-called ldquocritical heat fluxrdquo (CHF) that determines the maximum heat-removal capacity. Second, the inability to actively respond to fluctuating cooling demands due to the passive working principle. The present study seek to contribute to the advancement of phase-change cooling schemes by model-based development of control strategies that safely facilitate efficient boiling heat transfer close to CHF under dynamic operating conditions. These control strategies can be developed by means of a compact 3D model that describes the system-level dynamics of pool-boiling processes entirely in terms of the heat distribution within the heat-generating device. The compact 3D model and how to utilise it for the development of control strategies are the topics of this paper.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"70 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116386265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167158
T. Kunugi, Y. Ueki, T. Naritomi, H. Son, Z. Kawara, S. Muko, S. Wakamori
A convective heat transfer enhancement using nano- and micro-scale porous layer surface was discovered by Kunugi et al. The heat transfer experiments, analytical considerations, flow visualization near the porous layer, and the porous layer surface observation were performed to grasp the heat transfer characteristics and the heat transfer enhancement mechanism. The heat transfer experiments revealed the porous layers were capable to enhance heat transfer by 20-25% in net energy compared to the bare plate, independently of substrate materials. The heat transfer experiment changing the Reynolds number showed the Reynolds number dependency of heat transfer performance. One-dimensional unsteady heat conduction analysis showed the temperature recovery of the porous layer was incapable to catch up with the very fast temperature fluctuation, so that the porous layer might be a thermal-resistance when the main flow was strongly turbulent. The vestige visualized by the tracer-particles of around 0.85 mum in diameter showed a fluid behavior like "squirt" from the porous layer. From observation of the porous-layer surface, the porous layer has some micron-scale bubbles inside its own pore-connecting structure in spite of the good wetting feature. The expansion and contraction of the bubble-foam in the layer was observed and these behaviors may be considered as the main contribution to the mechanism of the heat transport.
{"title":"Consideration of heat transfer enhancement mechanism using nano- and micro-scale porous layer","authors":"T. Kunugi, Y. Ueki, T. Naritomi, H. Son, Z. Kawara, S. Muko, S. Wakamori","doi":"10.1109/THETA.2008.5167158","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167158","url":null,"abstract":"A convective heat transfer enhancement using nano- and micro-scale porous layer surface was discovered by Kunugi et al. The heat transfer experiments, analytical considerations, flow visualization near the porous layer, and the porous layer surface observation were performed to grasp the heat transfer characteristics and the heat transfer enhancement mechanism. The heat transfer experiments revealed the porous layers were capable to enhance heat transfer by 20-25% in net energy compared to the bare plate, independently of substrate materials. The heat transfer experiment changing the Reynolds number showed the Reynolds number dependency of heat transfer performance. One-dimensional unsteady heat conduction analysis showed the temperature recovery of the porous layer was incapable to catch up with the very fast temperature fluctuation, so that the porous layer might be a thermal-resistance when the main flow was strongly turbulent. The vestige visualized by the tracer-particles of around 0.85 mum in diameter showed a fluid behavior like \"squirt\" from the porous layer. From observation of the porous-layer surface, the porous layer has some micron-scale bubbles inside its own pore-connecting structure in spite of the good wetting feature. The expansion and contraction of the bubble-foam in the layer was observed and these behaviors may be considered as the main contribution to the mechanism of the heat transport.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"255 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128345166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167193
E. Thomas, Kunal Karan
An improved steady state method, combining experiment and mathematical modeling, has been developed to characterize the convective heat transfer coefficient of coated and uncoated metallic foam. A developed two-dimensional thermo-fluid model allows for analysis on a wide range of geometrically diverse monolithic foam shapes. The volumetric heat transfer coefficient of 10, 20 and 40 pore-per-inch uncoated aluminium foams was determined to range between 7,000 and 9,000 plusmn 2,000 Wldrm-3ldrK-1 at a Reynolds number of 400. The presence of a 76 micron-thick anodized layer on the identical foams effected a small but significant reduction in the volumetric convection coefficient.. Coating also reduced the permeabilities of the monoliths by 4-20%.
{"title":"Methodology for determining volumetric convection coefficients in metallic foam monoliths coated with ceramic catalyst support","authors":"E. Thomas, Kunal Karan","doi":"10.1109/THETA.2008.5167193","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167193","url":null,"abstract":"An improved steady state method, combining experiment and mathematical modeling, has been developed to characterize the convective heat transfer coefficient of coated and uncoated metallic foam. A developed two-dimensional thermo-fluid model allows for analysis on a wide range of geometrically diverse monolithic foam shapes. The volumetric heat transfer coefficient of 10, 20 and 40 pore-per-inch uncoated aluminium foams was determined to range between 7,000 and 9,000 plusmn 2,000 Wldrm-3ldrK-1 at a Reynolds number of 400. The presence of a 76 micron-thick anodized layer on the identical foams effected a small but significant reduction in the volumetric convection coefficient.. Coating also reduced the permeabilities of the monoliths by 4-20%.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131120314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167165
Y. Jaluria
This paper discusses microscale transport processes that arise in the fabrication of advanced materials. In many cases, the dimensions of the device being fabricated is in the microscale range and, in others, underlying transformations that determine product quality and characteristics are at micro or nanoscale levels. The basic considerations in these transport phenomena are outlined. Three important materials processing circumstances are considered in detail. These include the fabrication of multilayer and hollow optical fibers, as well as those where microscale dopants are added to achieve desired optical characteristics, thin film fabrication by chemical vapor deposition and microscale coating of fibers and devices. It is shown that major challenges are posed by the simulation as well as experimentation over microscale dimensions. These include accurate simulation to capture large gradients and variations over relatively small dimensions, simulating high pressures and viscious dissipation effects in microchannels, modeling effects such as surface tension that become dominant at microscale dimensions, and coupling micro and nanoscale mechanisms with boundary conditions imposed at the macroscale. Similarly, measurements over microscale dimensions are much more involved that those over macro or industrial scales because of access to the regions of interest, small tension effects and other mechanisms that are difficult to measure and that can make the process infeasible, and difficulty in achieving desired accuracy for validating the mathematical and numerical models. The paper presents some of the approaches that may be adopted to overcome these difficulties. Comparisons between experimental and numerical results are included to show fairly good agreement, indicating the validity of the modeling of transport.
{"title":"Microscale transprot in the thermal processing of new and emerging advanced materials","authors":"Y. Jaluria","doi":"10.1109/THETA.2008.5167165","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167165","url":null,"abstract":"This paper discusses microscale transport processes that arise in the fabrication of advanced materials. In many cases, the dimensions of the device being fabricated is in the microscale range and, in others, underlying transformations that determine product quality and characteristics are at micro or nanoscale levels. The basic considerations in these transport phenomena are outlined. Three important materials processing circumstances are considered in detail. These include the fabrication of multilayer and hollow optical fibers, as well as those where microscale dopants are added to achieve desired optical characteristics, thin film fabrication by chemical vapor deposition and microscale coating of fibers and devices. It is shown that major challenges are posed by the simulation as well as experimentation over microscale dimensions. These include accurate simulation to capture large gradients and variations over relatively small dimensions, simulating high pressures and viscious dissipation effects in microchannels, modeling effects such as surface tension that become dominant at microscale dimensions, and coupling micro and nanoscale mechanisms with boundary conditions imposed at the macroscale. Similarly, measurements over microscale dimensions are much more involved that those over macro or industrial scales because of access to the regions of interest, small tension effects and other mechanisms that are difficult to measure and that can make the process infeasible, and difficulty in achieving desired accuracy for validating the mathematical and numerical models. The paper presents some of the approaches that may be adopted to overcome these difficulties. Comparisons between experimental and numerical results are included to show fairly good agreement, indicating the validity of the modeling of transport.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114332494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167179
M. Ashjaee, M. Goharkhah, K. Madanipour, S. Amiri
Calculation of the temperature distribution around axisymmetric geometries such as cylinders and cones and the local heat transfer coefficient on such geometries is often encountered. This problem occurs for example in studies of flow performance in cylindrical channel, temperature distribution around a burner flame and heat transfer from cylindrical tanks. Using a Mach-Zehnder interferometer, interferograms around an isothermal vertical cylinder at three different surface temperatures have been obtained. In this paper, in order to calculate the temperature distributions and the local heat transfer coefficients from interferograms, four methods of interferogram analysis including three classical methods and one transform method have been presented. In order to investigate the accuracy of the methods, results have been compared with the results of the analytical solution and relative accuracy of each method has been obtained. Results show that the transform method, while being less time consuming, is the most accurate method.
{"title":"Calculation of local heat transfer coefficient on axisymmetric geometries using different methods of fringe analysis","authors":"M. Ashjaee, M. Goharkhah, K. Madanipour, S. Amiri","doi":"10.1109/THETA.2008.5167179","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167179","url":null,"abstract":"Calculation of the temperature distribution around axisymmetric geometries such as cylinders and cones and the local heat transfer coefficient on such geometries is often encountered. This problem occurs for example in studies of flow performance in cylindrical channel, temperature distribution around a burner flame and heat transfer from cylindrical tanks. Using a Mach-Zehnder interferometer, interferograms around an isothermal vertical cylinder at three different surface temperatures have been obtained. In this paper, in order to calculate the temperature distributions and the local heat transfer coefficients from interferograms, four methods of interferogram analysis including three classical methods and one transform method have been presented. In order to investigate the accuracy of the methods, results have been compared with the results of the analytical solution and relative accuracy of each method has been obtained. Results show that the transform method, while being less time consuming, is the most accurate method.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114403059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167172
S. Kumar, O. Singh
The key to the successful and strong gas turbine technology bases significantly upon the introduction of new materials and/or the usage of efficient means & methods of turbine blades cooling. Present paper deals with the comparative evaluation of the cooling effectiveness for different methods of turbine blade cooling. Different cooling techniques such as internal cooing, film cooling and transpiration cooling have been considered for the study with compressed air as cooling medium. The performance results of the gas turbine have been expressed in terms of overall efficiency and specific power of the gas turbine cycle, which significantly depend on the type of blade cooling employed. The independent variables considered are the TIT, compressor pressure ratio and the inlet coolant temperature. Cooled gas turbine model, modeling of all components of gas turbine cycle and gas properties model have been used for parametric analysis. A computer code ldquoGTANALYSrdquo has been developed to perform all the calculations.
{"title":"Thermodynamic evaluation of different gas turbine blade cooling techniques","authors":"S. Kumar, O. Singh","doi":"10.1109/THETA.2008.5167172","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167172","url":null,"abstract":"The key to the successful and strong gas turbine technology bases significantly upon the introduction of new materials and/or the usage of efficient means & methods of turbine blades cooling. Present paper deals with the comparative evaluation of the cooling effectiveness for different methods of turbine blade cooling. Different cooling techniques such as internal cooing, film cooling and transpiration cooling have been considered for the study with compressed air as cooling medium. The performance results of the gas turbine have been expressed in terms of overall efficiency and specific power of the gas turbine cycle, which significantly depend on the type of blade cooling employed. The independent variables considered are the TIT, compressor pressure ratio and the inlet coolant temperature. Cooled gas turbine model, modeling of all components of gas turbine cycle and gas properties model have been used for parametric analysis. A computer code ldquoGTANALYSrdquo has been developed to perform all the calculations.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126544403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167196
M. Sabry, M. Shatla
This work studies heat transfer in a cryogenic tank, in order to estimate the heat infiltration rate as well as the required thermal insulation thickness needed to fulfill the boil off ratio. It addresses some general recommendation about thermal insulation thickness. Design calculations to actually get thermal insulation thickness are presented in another paper. The present research work establishes analytically temperature distributions in outer tank walls due to varying outside conditions. A simple formula that can be used by designers has been obtained that closely approximates the detailed analytical solution developed in the present work. Comparison shows that this approximate estimate is a very close and slightly more conservative than the detailed analytical solution. Moreover, it proves that uniform heat flux density gives the best distribution of insulation over different tank part.
{"title":"An enhanced thermal model for cryogenic tanks","authors":"M. Sabry, M. Shatla","doi":"10.1109/THETA.2008.5167196","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167196","url":null,"abstract":"This work studies heat transfer in a cryogenic tank, in order to estimate the heat infiltration rate as well as the required thermal insulation thickness needed to fulfill the boil off ratio. It addresses some general recommendation about thermal insulation thickness. Design calculations to actually get thermal insulation thickness are presented in another paper. The present research work establishes analytically temperature distributions in outer tank walls due to varying outside conditions. A simple formula that can be used by designers has been obtained that closely approximates the detailed analytical solution developed in the present work. Comparison shows that this approximate estimate is a very close and slightly more conservative than the detailed analytical solution. Moreover, it proves that uniform heat flux density gives the best distribution of insulation over different tank part.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"32 125","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132973302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-07-11DOI: 10.1109/THETA.2008.5167163
K. Anubhav, J. Yogendra
Full-scale model of a representative data center was developed, with the arrangement of bringing outside air under suitable conditions. Four different world cities were considered to evaluate the energy savings over the entire year. Results show a significant saving in chiller energy (up to 70%), and even the possibility of switching off chillers for certain months of the year. The details of relative humidity and temperature variation inside the data center space and humidification/dehumidification requirements were investigated. The rack exit air temperature was found to be lower when economizer was used, as compared to the exit air temperature without the economizer. The lower exit air temperature results from reduced hot air recirculation, as the hot air is exhausted from the hot air outlet and fresh air is brought from the outside into the data center space. The saving in energy is significant and justifies the infrastructure improvements, such as improved filters and control mechanism for the outside air influx. Fan power to bring outside air into the data center space has also been investigated.
{"title":"Use of airside economizer for data center thermal management","authors":"K. Anubhav, J. Yogendra","doi":"10.1109/THETA.2008.5167163","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167163","url":null,"abstract":"Full-scale model of a representative data center was developed, with the arrangement of bringing outside air under suitable conditions. Four different world cities were considered to evaluate the energy savings over the entire year. Results show a significant saving in chiller energy (up to 70%), and even the possibility of switching off chillers for certain months of the year. The details of relative humidity and temperature variation inside the data center space and humidification/dehumidification requirements were investigated. The rack exit air temperature was found to be lower when economizer was used, as compared to the exit air temperature without the economizer. The lower exit air temperature results from reduced hot air recirculation, as the hot air is exhausted from the hot air outlet and fresh air is brought from the outside into the data center space. The saving in energy is significant and justifies the infrastructure improvements, such as improved filters and control mechanism for the outside air influx. Fan power to bring outside air into the data center space has also been investigated.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128386697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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