In recent years, the electronic chip is continuously developing in turning high performance. This trend urges the heat sink of electronic chip to become gradually important, and then that will develop many type of heat sink, which is water-cooling system. Therefore, the purpose of this paper is designing a high efficiency water-cooling element (WCE). The present study mainly aims at three points to bring up: (1) The different type chamber make use of the CFD package software FLUENT to study the pressure drop, velocity field and turbulent intensity deposition. (2) The different plank thickness, thermal conductivity and convection heat transfer coefficient use finite difference method to solve heat diffusion equation, and to confer thermal resistance value. (3) Then, machined this designed WCE and then measured its thermal resistance value. The results show: (1) The pressure drop main effect parameter is inlet velocity. (2) The thermal resistance value main effect parameter is convection heat transfer coefficient. (3) The plank thickness is inverse proportion relation with thermal resistance value. (4) The surface temperature range and mean surface temperature should become reference index in heat sink developmental process. (5) The cooling performance of Type D WCE is optimum in this paper. (6) The design is cross groove on convection surface, which should reduce thermal resistance value.

Experimental measurements and numerical simulations have been performed on copper and aluminum microchannel heatsinks of 300, 420, 500, and 900 &amp / #956 / m channel widths. The heatsinks have been designed specifically for use with T/R (transmit/receive) module cooling applications of military phased array radars. An analytical calculation was also performed to aid in the design methodology. Distilled water was used as the coolant with flow rates ranging from 0.50 lpm (liters per minute) to 1.00 lpm. Local heat fluxes as high as 100 W/cm2 were tested. Upon completion of the experiments, the thermally best performing specimen, the 300 &amp / #956 / m copper specimen, yielded a maximum temperature rise of 26.1 &deg / C between the heat load and coolant inlet, at a coolant flow rate of 1.00 lpm and local heat flux of 100 W/cm2, leading to a thermal resistance of 0.63 &deg / C/W. The pressure drop measured across the heatsink under these conditions was 0.030 bar. Numerical simulations were carried out using the commercial Computational Fluid Dynamics (CFD) software FLUENT&reg / . Effects of thermal interface layers and heat spreading due to the localized heat load were investigated. Simulation results for temperature were seen to agree fairly well with experimental data as long as thermal interface layers were accounted for. The study showed that the T/R modules of military phased array radars, dissipating as high as 100 W/cm2 locally, could be cooled within the limits of the harsh environmental conditions required of military applications with moderate pressure drops.

A novel complementary metal oxide semiconductor (CMOS) compatible microchannel heat sink is designed, fabricated, and tested for electronic cooling applications. The proposed microchannel heat sink requires no design change of the electronic circuitry underneath. Therefore, microchannels can be fabricated on top of the finished CMOS wafers by just adding a few more steps to the fabrication flow. Combining polymer (parylene C) and metal (copper) structures, a high performance microchannel heat sink can be easily manufactured on top of the electronic circuits, forming a monolithic cooling system. In the design stage, computer simulations of the microchannels with several different dimensions have been performed. Microchannels made of only parylene showed poor heat transfer performance as expected since the thermal conductivity of parylene C is very low. Therefore an alternative design comprising structural parylene layer and embedded metal layers has been modeled. Copper is selected as the metal due to its simple fabrication and very good thermal properties. The results showed that the higher the copper surface area the better the thermal performance of the heat sinks. Based on the modeling results, the final test structures are designed with full copper sidewalls with a parylene top wall. Several different microchannel test chips have been fabricated in METU-MEMS Research &amp / Application Center cleanroom facilities. The devices are tested with different flow rates and heat loads. During the tests, it was shown that the test devices can remove about 126 W/cm2 heat flux from the chip surface while keeping the chip temperature at around 90&deg / C with a coolant flow rate of 500 &mu / l/min per channel.

Experimental measurements are conducted on uninterrupted and interrupted aluminum microchannel heat sinks of 300, 500, 600 and 900 &mu / m channel widths. Two different versions of interrupted channels are tested / with single interruption and with 7 interruptions. Distilled water is used as the working fluid and tests are conducted at volumetric flow rates in a range of 0.5-1.1 lpm. Thermoelectric foils are used to supply uniformly distributed heat load to the heat sinks such that for all the tests the heat removed by water is kept constant at 40 W. Pressure drop and temperature increase are measured along the channels of different configurations for a number of different flow rates. For the interrupted channels thermal boundary layers re-initialize at the leading edge of each interrupted fin, which decreases the overall boundary layer thickness. Also the flow has been kept as developing, which results in better heat transfer performance. Due to the separation of the flow into branches, secondary flows appear which improves the mixing of the stream. Advanced mixing of the flow also enhances the thermal performance. In the experiments, it is observed that interruption of channels improved the thermal performance over the uninterrupted counterparts up to 20% in average Nusselt number, for 600 micron-wide channels. The improvement of average Nusselt number between the single interrupted and multi interrupted channels reached a maximum value of 56% for 500 micron-wide channels. This improvement did not cause a high pressure drop deviation between the uninterrupted and interrupted microchannels even for the maximum volumetric flow rate of 1.1 lpm. Highest pressure drop through the channels was measured as 0.07 bar, which did not require to change the pump. In the tests, maximum temperature difference between the inlet of the fluid and the base of the channel is observed as 32.8&deg / C, which is an acceptable value for electronic cooling applications.

An investigation of the sympathetic cooling method for the studies of large ultra-cold molecular ions in a quadrupole ion trap has been conducted.Molecular dynamics simulations are performed to study the rf heating mechanisms in the ion trap. The dependence of rf heating rates on the ion temperature, trapping parameters, and the number of ions is obtained. New rf heating mechanism affecting ultra-cold ion clouds exposed to laser radiation is described.The saturation spectroscopy setup of the hyperfine spectra of the molecular iodine has been built to provide an accurate frequency reference for the laser wavelength. This reference is used to obtain the fluorescence lineshapes of the laser cooled Mg$^+$ ions under different trapping conditions.The ion temperatures are deduced from the measurements, and the influence of the rf heating rates on the fluorescence lineshapes is also discussed. Cooling of the heavy ($m=720$a.u.) fullerene ions to under 10K by the means of the sympathetic cooling by the Mg$^+$ ions($m=24$a.u.) is demonstrated. The single-photon imaging system has been developed and used to obtain the images of the Mg$^+$ ion crystal structures at mK temperatures.

<p>The energy consumption is continuous to increase around the world and with that follows the demand for sustainable solutions for future energy systems. With growing energy consumption from fossil based fuels the threat of global warming through release of CO₂ to the atmosphere increases. The demand for cooling is also growing which would result in an increased consumption of electricity if the cooling demand was to be fulfilled by electrically driven cooling technology. A more sustainable solution can be to use heat-driven absorption cooling where waste heat may be used as driving energy instead of electricity.</p><p>This thesis focuses on the role and potential of absorption cooling in future energy systems. Two types of energy systems are investigated: a district energy system based on waste incineration and a distributed energy system with natural gas as fuel. In both cases, low temperature waste heat is used as driving energy for the absorption cooling. The main focus is to evaluate the absorption technology in an environmental perspective, in terms of reduced CO₂ emissions. Economic evaluations are also performed. The reduced electricity when using absorption cooling instead of compression cooling is quantified and expressed as an increased net electrical yield.</p><p>The results show that absorption cooling is an environmentally friendly way to produce cooling as it reduces the use of electrically driven cooling in the energy system and therefore also reduces global CO₂ emissions. In the small-scale trigeneration system the electricity use is lowered with 84 % as compared to cooling production with compression chillers only. The CO₂ emissions can be lowered to 45 CO₂/MWhc by using recoverable waste heat as driving heat for absorption chillers. However, the most cost effective cooling solution in a district energy system is a combination between absorption and compression cooling technologies according to the study.</p><p>Absorption chillers have the potential to be suitable bottoming cycles for power production in distributed systems. Net electrical yields over 55 % may be reached in some cases with gas motors and absorption chillers. This small-scale system for cogeneration of power and cooling shows electrical efficiencies comparable to large-scale power plants and may contribute to reducing peak electricity demand associated with the cooling demand.</p>

This thesis is to study the feasibility of using river water from Gavleån in the cooling system of University of Gävle. The project is proposed by the campus service manager Akademiska Hus AB which intended to replace the current cooling production system with the water cooling system to reduce the electricity cost in cooling production. The river by direct distance is 600 meters from the university, the river water is to be extracted from the river via a pump house, flow through pipeline buried underground and delivered to the equipment house of Akademiska Hus.   Most water source cooling prefer water body with decent depth which contain low temperature water to use as free cooling source, but the issue that limits the practice is, the decent depth is not a very common feature of most water body near or within urban area. Like Gavleån which has an average depth of not over five meters while the sufficient depth is over 50 meters for the least or 70 meters to 100 meters often. So study the potential of using rather high temperature water from shallow water body can be of high interest for most cooling consumers.   The thesis progressed through the work in five parts. To introduce cooling in general starting with literature review, the concept, the mechanism, the device for end use and production, the demand of cooling and the reason behind it. Followed by case studies of water source cooling projects worldwide, which is mostly deep water source cooling, and another case of the local hospital cooling system that extract water from Gavleån, demonstrate the use of shallow water body in assisting cooling production, it gives some insights how the potential if similar system is to be implemented in the campus, which is mounted on the same river. Several tours to the hospital were taken to acquire data and understanding of the system.   Then the water temperature measurement from Gavleån in 2014 summer is presented. The measurement was carried out at a small dock by the river side during July to September of 2014. The measurements show the temperature of river water has been increasing which limits free cooling throughout the year, additional refrigerator is required to produce chilled water. The river water, in the hot seasons is used as cooler for the refrigerator and in cold season can be used for free cooling directly. Simulation of IDA-ICE gives the cooling demand of modelled building blocks, the output of cooling production season (consistent with the hot seasons) matches the cooling consumption data from Akademiska Hus by an error of 1% (414743 kWh of simulated result to 415270 kWh in documentation of Akademiska Hus).   To meet the demand of cooling and select more cost-effective refrigerator type, consumption and COP (COP: Coefficient of Performance) are calculated for compressor chiller and absorption chiller with basic cooling cycle for both. The results shown compressor chiller has much better performance but also higher consumption in electricity, while absorption chiller has rather low COP value in comparison but the need of energy input is much less given by its major consumption of energy is heat from hot water, already a purchased item by the university from district heating network. Cost-effectiveness wise speaking absorption chiller is a more optional choice. Reasonable values of assumption are largely employed in the calculation to select the better candidate and bring certain errors, which is then exam in sensitivity analysis to weigh the alternative parameter and the outcome from it.   The last part is to estimate the cost of chillers and pipeline, for the concern of minimizing errors due to uncertainty the operation cost, labor cost and future energy price are not included. As the calculation turns out the payback year of the new system can range from 7 to 12 years by different refrigerator setup and pipeline routine design, which is considered within the life time of the chiller and pipeline, also lower than the current cooling cost of the university and therefore concluded as promising investment.   Discussion and conclusion exam and finalize the whole thesis work. For the uncertainties of the calculation, the lack of information and data, which are improvements, can be done in future work. Also the improvements in other perspectives noted in terms of better load management for the cooling production units so the cost of equipment can be reduced, changes in building attachment and cooling device to reduce the demand of cooling, etc. But mostly draw the conclusion that with proper system configuration shallow water body can be helpful in reducing cooling consumption, and be a promising option for cities that have access to such water body.

Excessive exposure to heat stress can cause a host of heat-related illnesses. For laborers, job specific work demands and protective garments greatly increase the risk of succumbing to the effects of heat stress. Microclimate cooling has been used to control heat stress exposure where administrative or engineering controls are not adequate. This study tested the performance of four personal cooling vests for use with insulated protective clothing (gas extraction coveralls) in warm-humid (35 ° C, 50% relative humidity) and hot-dry (40°C, 30% relative humidity) conditions. On 10 separate occasions, 5 male volunteers walked on a treadmill to elicit a target metabolic rate of 300 watts, for 120 minutes, while wearing a (a) water cooled vest, (b) air cooled vest, (c) frozen polymer vest (FP) (d) liquid CO2 cooling (LCO2) vest, or (e) no cooling (NC). A three-way mixed effects ANOVA was used to assess the results and a Tukey's Honestly Significant Difference multiple comparison test was used to identify where significant differences occurred ( < 0.05). The air, water, and FP systems produced significantly lower heat storage rates compared to NC. To the extent that the gas extraction coverall is worn in an environment between 30°C and 45°C and the rate of work is moderate, the FP, air and water vest were shown to manage heat storage well, reducing storage rate by about 48%, 56% and 65% respectively.

Deposition of contaminant particles on gas turbine surfaces reduces the aerodynamic and cooling efficiency of the turbine and degrades its materials. Gas turbine designers seek a better understanding of this complicated phenomenon and how to mitigate its effects on engine efficiency and durability. The present study developed an experimental method in wind tunnel facilities to simulate the important physical aspects of the interaction between deposition and turbine cooling, particularly film cooling. This technique consisted of spraying molten wax droplets into the mainstream flow that would deposit and solidify on large scale, cooled, turbine airfoil models in a manner consistent with inertial deposition on turbine surfaces. The wax particles were sized to properly simulate the travel of particles in the flow path, and their adhesion to the surface was modeled by ensuring they remained at least partially molten upon impact. Initial development of this wax spray technique was performed with a turbine blade leading edge model with three rows of showerhead film cooling. It was then applied to turbine vane models with showerhead holes and row on pressure side consisting of either standard cylindrical holes or similar holes situated in a spanwise, recessed trench. Vane models were either approximately adiabatic or had a thermal conductivity selected to simulate the conjugate heat transfer of turbine airfoils at engine conditions. These models were also used to measure the adiabatic film effectiveness and overall cooling effectiveness in order to better assess how the cooling design interacted with deposition. Deposit growth was found to be sensitive to the mainstream air and the model surface temperatures and the solidification temperature of the wax. Deposits typically grew to an equilibrium thickness caused by a balance between erosion and adhesion. The existence of film cooling substantially redistributed deposit growth, but changes in blowing ratio had a minor effect. A hypothesis was proposed and substantiated for the physical mechanisms governing wax deposit growth, and its applicability to engine situations was discussed. / text

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