<p>Desiccant cooling is a technology that, based on a open psychrometric cycle, is able to provide cooling using heat as the main energy carrier. This technology uses a considerably smaller amount of electricity than refrigerators based on the vapor-compression cycle, which is an electricity driven cycle. Electricity is often more expensive than other types of energy and has CO₂ emissions associated with its generation , so desiccant cooling has the potential of achieving both economic and environmental benefits.</p><p>In addition to this, the heat the desiccant cooling cycle needs to work can be supplied at relative low temperatures, so it can use heat coming from the district heating grid, from a solar collector or even waste heat coming from industries.</p><p>The system which will be studied in this report is a desiccant cooling system based on the model designed by the company Munters AB. The systems relies on several components: a desiccant rotor, a rotary heat exchanger two evaporative humidifiers and two heating coils. It is a flexible system that is able to provide cooling in summer and heat during winter.</p><p>This study performs a deep economic and environmental analysis of the desiccant cooling systems, comparing it with traditional vapor compression based systems:</p><p>In order to achieve this objective a user-friendly software was created, called the DCSS – Desiccant Cooling Simulation Software – that simulates the operation of the system during a year and performs automatically all the necessary calculations.</p><p>This study demonstrates that economic savings up to 54% percent can be achieved in the running costs of desiccant cooling systems when compared to traditional compressor cooling systems, and  reductions up to39% in the CO₂ emissions. It also demonstrates that desiccant cooling is more appropriate in dry climate zones with low latent heat generation gains.</p><p>In addition to that, the DSCC software created will help further studies about the physical, economic and environmental feasibility of installing desiccant cooling systems in different locations.</p>

Originally presented as a thesis (M.S.), M.I.T., Dept. of Civil Engineering, 1978, by Kenneth F. Najjar. / "COO-4114-8". Statement of responsibility on title page reads: Kenneth F. Najjar, John J. Shaw, E. Eric Adams, Gerhard H. Jirka and Donald R.F. Harleman. "January 1979." Bibliography: p. 182-187.

Following an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied.

This thesis deals with some challenges related to the mitigation of climate change and the overall aim is to present and assess different possibilities for the mitigation of climate change by: • Suggesting some measures with a potential to abate net greenhouse gas (GHG) emissions, • Discussing ideas for how decision-makers could tackle some of the encountered obstacles linked to these measures, and • Pointing at some problems with the current Kyoto framework and suggesting modifications of it. The quantification of the net CO2 effect from a specific project, frequently referred to as emissions accounting, is an important tool to evaluate projects and strategies for mitigating climate change. This thesis discusses different emissions accounting methods. It is concluded that no single method ought to be used for generalisation purposes, as many factors may affect the real outcome for different projects. The estimated outcome is extremely dependent on the method chosen and, thus, the suggested approach is to apply a broader perspective than the use of a particular method for strategic decisions. The risk of losing the integrity of the Kyoto Protocol when over-simplified emissions accounting methods are applied for the quantification of emission credits that can be obtained by a country with binding emissions targets for projects executed in a country without binding emission targets is also discussed. Driving forces and obstacles with regard to energy-related co-operations between industries and district heating companies have been studied since they may potentially reduce net GHG emissions. The main conclusion is that favourable techno-economic circumstances are not sufficient for the implementation of a co-operation; other factors like people with the true ambition to co-operate are also necessary. How oxy-fuel combustion for CO2 capture and storage (CCS) purposes may be much more efficiently utilised together with some industrial processes than with power production processes is also discussed. As cost efficiency is relevant for the Kyoto framework, this thesis suggests that CCS performed on CO2 from biomass should be allowed to play on a level playing field with CCS from fossil sources, as the outcome for the atmosphere is independent of the origin of the CO2. / QC 20101015

Performance of two different waste heat recovery systems (one based on Rankine cycle and the other one using thermoelectricity) combined with non-hybrid, mild-hybrid and full hybrid systems are investigated. The vehicle under investigation was a 440hp Scania truck, loaded by 40 tons. Input data included logged data from a long haulage drive test in Sweden.All systems (waste heat recovery as well as hybrid) are implemented and simulated in Matlab/Simulink. Almost all systems are modeled using measured data or performance curves provided by one manufacturer. For Rankine system results from another investigation were used.Regardless of practical issues in implementing systems, reduction in fuel consumption for six different combination of waste heat recovery systems and hybrid systems with different degrees of hybridization are calculated. In general Rankine cycle shows a better performance. However, due to improvements achieved in laboratories, thermoelectricity could also be an option in future.This study focuses on “system” point of view and therefore high precision calculations is not included. However it can be useful in making decisions for further investigations.

Refrigeration systems employing the NH3-H2O absorption cycle provide cooling using a thermal energy input. This cycle relies on the zeotropic nature of the refrigerant - absorbent pair: because of the difference in boiling temperatures between NH3 and H2O, they can be separated through selective boiling in the desorber. Desorbers with counter-current flow of the solution and generated vapor enable efficient heat and mass transfer between the two phases, reducing the absorbent content in the generated vapor. Flow visualization experiments at temperatures, concentrations and pressures representative of operating conditions are necessary to understand the heat and mass transfer processes and flow regime characteristics within the component. In this study, a Flooded Column desorber, which accomplishes desorption of the refrigerant vapor through a combination of falling-film and pool boiling, was fabricated and tested. Refrigerant-rich solution enters the top of the component and fills a column, which is heated by an adjacent heated microchannel array. The vapor generated within the component is removed from the top of the component, while the dilute solution drains from the bottom. Flow visualization experiments showed that the Flooded Column desorber operated most stably in a partially flooded condition, with a pool-boiling region below a falling-film region. It was found that the liquid column level was dependent on operating conditions, and that the pool-boiling region exhibits aggressive mixing between the vapor and solution phases. Heat transfer coefficients were calculated from the data for the pool-boiling region, and were compared with the predictions of several mixture pool-boiling correlations from the literature. The correlations from the literature were in general unable to predict the data from this study adequately. It was found that the Flooded Column desorber yielded higher heat transfer coefficients within the pool-boiling region than those predicted by these correlations. Therefore, modifications to existing mixture boiling correlations are suggested based on the findings of this study. The resulting modified correlation predicts 33 of the 35 data points from this study within ±40%, with an average absolute error of 19%.

Desiccant cooling is a technology that, based on a open psychrometric cycle, is able to provide cooling using heat as the main energy carrier. This technology uses a considerably smaller amount of electricity than refrigerators based on the vapor-compression cycle, which is an electricity driven cycle. Electricity is often more expensive than other types of energy and has CO2 emissions associated with its generation , so desiccant cooling has the potential of achieving both economic and environmental benefits. In addition to this, the heat the desiccant cooling cycle needs to work can be supplied at relative low temperatures, so it can use heat coming from the district heating grid, from a solar collector or even waste heat coming from industries. The system which will be studied in this report is a desiccant cooling system based on the model designed by the company Munters AB. The systems relies on several components: a desiccant rotor, a rotary heat exchanger two evaporative humidifiers and two heating coils. It is a flexible system that is able to provide cooling in summer and heat during winter. This study performs a deep economic and environmental analysis of the desiccant cooling systems, comparing it with traditional vapor compression based systems: In order to achieve this objective a user-friendly software was created, called the DCSS – Desiccant Cooling Simulation Software – that simulates the operation of the system during a year and performs automatically all the necessary calculations. This study demonstrates that economic savings up to 54% percent can be achieved in the running costs of desiccant cooling systems when compared to traditional compressor cooling systems, and  reductions up to39% in the CO2 emissions. It also demonstrates that desiccant cooling is more appropriate in dry climate zones with low latent heat generation gains. In addition to that, the DSCC software created will help further studies about the physical, economic and environmental feasibility of installing desiccant cooling systems in different locations.

Following an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied.

Limited worldwide energy supplies demand the improved utilization of thermal energy, which is the dominant form of all primary energy sources used today. Large quantities of waste heat are routinely exhausted wherever thermo-mechanical energy conversion occurs, providing an opportunity to improve utilization. Two waste-heat-driven cycles are analyzed: an absorption/compression cascade cooling cycle and a coupled Rankine/compression cycle. The absorption/compression cascade provides an environmentally-sound option for a common approach to thermal energy recovery: the use of absorption cycles for cooling applications. To achieve cooling at temperatures below 0ºC, ammonia-water is the overwhelming choice for the working fluid. However, concerns about the toxicity and flammability of ammonia sometimes limit its application in sensitive arenas. In this study, a lithium bromide-water absorption cycle is coupled with a carbon dioxide vapor compression cycle to realize the benefits of high-lift cooling without the concerns associated with ammonia. This cycle utilizes a waste heat stream at temperatures as low as 150°C to provide cooling at -40°C. The topping absorption cycle achieves a coefficient of performance (COP) of about 0.77, while the bottoming cycle achieves a COP of about 2.2. The coupled Rankine/compression cycle provides a mechanical expansion and compression approach to achieve thermally activated cooling, again driven by waste heat. The power produced in the turbine of the Rankine cycle is directly coupled to the compressor of a vapor-compression cooling cycle to generate cooling to be utilized for space-conditioning. The refrigerant R245fa is used throughout the cycle. Even with low grade waste heat sources, a Rankine cycle efficiency of about 11-12 percent can be achieved. When coupled to the bottoming compression cycle with a COP of about 2.7, this yields an overall waste heat to cooling conversion efficiency of about 32 percent at nominal conditions.

Sustaining high performance demand has led to the development of manycore processors. These manycore processors have thermal properties which are different from conventional processors. In order to understand the thermal characteristics of such manycore processors, we have developed a modeling environment with a rich set of features which can be used to used to model different scenarios in manycore processors. Using this modeling framework, we have developed a thermal management policy called 'Weight based management policy'. We have also developed a GUI based modeling tool which can be integrated into the computer architecture curriculum so as to enable students to understand the importance of thermal limitations right during the design phase.