Dissertations / Theses on the topic 'Heat exchangers – Design and construction – Testing'

Finned-tube heat exchangers are predominantly used in space conditioning systems, as well as other applications requiring heat exchange between two fluids. One important widespread use is in residential air conditioning systems. These residential cooling systems influence the peak demand on the U.S. national electrical system, which occurs on the hot summer afternoons, and thereby sets the requirement for the expensive infrastructure requirement of the nations power plant and electrical distribution system. In addition to this peak demand, these residential air conditioners are major energy users that dominate residential electrical costs and environmental impact. The design of finned-tube heat exchangers requires the selection of over a dozen design parameters by the designer. The refrigerant side flow and heat transfer characteristics inside the tubes have been thoroughly studied. However, the air side flow around the tube bundle and through the fin gaps is much more complex and depends on over a dozen design parameters. Therefore, experimental measurement of the air side performance is needed. First this study built an experimental system and developed methodology for measuring the air side heat transfer and pressure drop characteristics of fin tube heat exchangers. This capability was then used to continue the goal of expanding and clarifying the present knowledge and understanding of air side performance to enable the air conditioner system designer in verifying an optimum fin tube condenser design. In this study eight fin tube heat exchangers were tested over an air flow face velocity range of 5 ?? ft/s (675-1600cfm). The raw data were reduced to the desired heat transfer and friction data, j and f factors. This reduced heat transfer and friction data was plotted versus Reynolds number and compared. The effect of fin spacing, the number of rows and fin enhancement were all investigated. The heat transfer and friction data were also plotted and compared with various correlations available from open literature. The overall accuracy of each correlation to predict experimental data was calculated. Correlations by C.C. Wang (1998b, 1999) showed the best agreement with the data. Wangs correlations (1998b, 1999) were modified to fit the current studys data.

Continual development of internal combustion engines requires greater performance from liquid coolants and heat exchangers to maintain optimal temperature. For the purpose of experimental testing of traditional, compact, and microchannel heat exchangers, a test facility has been designed, constructed, and utilized. The facility includes equipment and instrumentation necessary to create operating conditions and record data primarily for testing plate-fin brazed aluminum heat exchanger where heat is being transferred from liquid to air. Other arrangements of heat exchangers could be tested as well with some modifications. Initial tests were performed at several specified operating conditions for three liquids: water, a traditional glycol based Extended Life Coolant (ELC), and a new Glycol Free Coolant (GFC) in an attempt to characterize their heat transfer ability. Results of the tests found that the product of overall heat transfer coefficient and heat exchanger area (UA) was very similar for GFC and water, and it was less for ELC by a narrow margin of 1.3% difference on average. Uncertainty due to instrumentation accuracy was calculated to be 1.8% on average making the results overall UA unverifiable. Measured pressure drop across the heat exchanger which is proportional to required pumping power was found to be 13.5% higher for GFC than ELC at nominal conditions. The GFC offers similar heat transfer performance and marginally increased pumping power requirements compared to the traditional ELC. Due to similar heat transfer performance and the small effect of pressure drop, GFC would be good alternative to ELC due to its less toxic composition.

In 2010, the Ground Source Heat Pumps (GSHPs) market in the European Union went up over one million (1 014 436 units at the end of 2010 according to EUROBSERV’ER 2011). In 2011, it was estimated around 1.25 million according to Bayer et al. (2012). With more than 378 000 units installed in 2010, according to the Swedish heat pump association (SVEP), the Swedish GSHPs market was the first in the EU. As for the French GSHPs market, it was estimated to 151 938 units in service in 2010, which propelled France at the third rank in the EU. However, despite a relatively important number of GSHPs installed in the whole EU, since 2008 GSHP sales have shrank. Even Sweden which has been the most competitive country sees its GSHP sales decline in the first quarter of 2012 (EUROBSERV’ER 2011). This report is the achievement of my Master of Science Thesis project. It also represents the end of my studies at INSA Lyon in France and concludes my degree in Energetic and Environment Engineering. This report deals with the improvement of a heat injection apparatus which is available at KTH (Royal Institute of Technology). This equipment is better known as Thermal Response Test (TRT) apparatus. This kind of equipment improves Borehole Heat Exchangers (BHE) design in terms of size and cost benefits. This technology is generally used to design GSHP installations in both domestic and industrial purposes. It allows to determine really important thermal BHE parameters: the thermal conductivity of the ground and the borehole thermal resistance. The report covers a theoretical description of TRT experiments, the reasons and objectives of such a project, the apparatus design and its construction. The last part is dedicated to a first experimental laboratory results and some problems met during the project course.

Determination of the heat transfer coefficients for natural and mixed convection in horizontal annuli is important for designing double pipe heat exchangers and for energy storage systems. In part one and two of this study, the 2D numerical solution of the laminar natural convection of water in six internally finned horizontal annuli has been obtained. The fins are attached to the external surface of the inner cylinder. Only the symmetrical half of the horizontal annulus with three equally spaced longitudinal divergent solid and porous fins are considered. The parameters of the problem are Rayleigh number, fin height, permeability and porosity of the porous fin, etc. The above parameters are suitably varied to ascertain their effects on fluid flow and heat transfer. The results show that traditional solid fins provide much higher heat transfer rates compared to the porous fins. Part three of this work deals with mixed convective heat transfer (laminar natural and forced convections) of water in a vented annulus. The forced flow conditions are imposed by providing an inlet at the top and an outlet at the bottom. For various parameters of the problem, the average and local Nusselt numbers along the inner cylinder are calculated for water for both aiding and opposing flows. The fourth part of this study deals with numerical modeling of natural convection of nanofluids in a horizontal cylindrical annulus. Simulations are carried out for Cu-water nanofluids. The results, in general, show that nanoparticles systematically decrease the natural convective heat transfer coefficient on the inner cylinder. Practical and useful correlations are provided for calculating average heat transfer rates from the inner cylinder in the form of average equivalent thermal conductivity and average Nusselt number for all of the four cases discussed above. These correlations are new and will be helpful in designing heat exchangers.

Thermoacoustic engines convert heat into acoustic pressure waves with no moving parts; this inherently results in high reliability, low maintenance and low manufacturing costs. Significant increases in the performance of these devices have enabled rivalry with more mature energy conversion methods in both efficiency and power output. This optimal production of acoustic power can be ultimately used to achieve cryogenic temperatures in thermoacoustic refrigerators, or can be interfaced with reciprocating electro-acoustic power transducers to generate electricity. This thesis describes the design, fabrication and testing of a Thermoacoustic Power Converter. The system interfaces a thermoacoustic-Stirling heat engine with a pair of linear alternators to produce 100 watts of electricity from a heat input. It operates with helium at 450 psig internal pressure and a hot side temperature of 1200F. Through thermoacoustic phenomena, these conditions sustain a powerful pressure wave at a system specific 100 Hz. This pressure wave is used to drive the two opposed linear alternators in equal and opposite directions to produce a single phase AC electrical output at that same system frequency. The opposing motion of the two alternators enables a vibration-balanced system. The engine has created 110 watts of acoustic power and the complete Thermoacoustic Power Converter system has produced 70 watts of AC electricity. Compensating for some heat leaks, the converter reaches 26.3% heat to acoustic power efficiency and 16.8% heat to electric efficiency when those maximum values are achieved. This conversion of heat to acoustic power is 40% of the Carnot thermodynamic efficiency limit.

Thesis (MEng)--University of Stellenbosch, 2000.
ENGLISH ABSTRACT: This report describes the Experimental and Numerical Investigations conducted, during the determination of the structural mechanics of elliptical tubes, viz. the F- and the Atubes. This report is requested in an endeavour to assist Sasol, who is currently busy developing and updating specifications on Air Cooled Heat Exchangers. The objectives of this report therefore are to : (1) determine the strength and the effectiveness of the tube-to-tube-sheet joints. (2) determine the allowable pressure limits on the tubes and (3) investigate the effects of thermal load and vibration on the tube bundle. A series of experiments were conducted to meet these objectives. From a Shear Load experiment it was found that the maximum allowable axial load on the Fand the A-tube is 14.55 kN and 20. 86 kN respectively. Fin Plates were found to have little effect on the bending strength of the tube, w~ilst they have significant effect on the resistance to volumetric expansion of the tube. In fact the more fins per unit length the greater the resistance to volumetric expansion of the tube. These conclusions were drawn from Bending and Pressure Load experiments respectively and supported by FEM analysis of the tube using NASTRAN. When the design pressure limit given by the manufacturer (GEA Air Cooled Systems), were tested using FEM analysis, it was found that they cause no significant deformation and failure of the tubes. Thermal stresses on the tube bundle greatly affect the first tube in the first row (row closest to the flanges) of the tube bundle and it is recommended that provision for thermal expansion be made to reduce these stresses. To reduce vibrations induced by the fan, it is recommended that the natural frequency of the tube bundle must not equal the number of blades (N) times the angular frequency (co) of the fan, or multiples thereof, of each mode of vibration.
AFRIKAANSE OPSOMMING: Hierdie tesis beskrywe die Numeriese en Eksperimentele ondersoeke na die sterkte van elliptiese verkoelingsbuise, naamlik die F- en A- tipes. Hierdie werk sal Sasol, wat huidiglik besig is met die opgradering, van spesifikasies vir lugverkoelde hitteuitruilers van nut wees. Die doelwitte van hierdie tesis is om: (1) die sterkte en effektiwiteit van die buis laste was die buis and die buisplaat verdind, te ondersoek, (2) die toelaatbare druklimiete, sowel as (3) die effek wat hitte en vibrasie op 'n buisbundel het, te ondersoek. 'n Reeks eksperimente is uitgevoer om hierdie doelwitte te bevredig. 'n Skuifbelastingseksperiment het aangedui dat die toelaatbare krag wat op 'n F- en A-buis respektiewelik aangewend kan word 14.55 kN en 20.86 kN is. Die ondersoek het aangetoon dat vinne geen noemenswaardige effek op die buigsterkte van die buise gehad het nie, maar dat dit 'n aansienlike verstywingseffek teen volumetriese verandering as gevolg van interne druk, gehad het. Hierdie gevolgtrekkings is bereik deur die Druk- en Buigtoetse wat numeries bevestig is met die NASTRAN eindige element analise (EEA) pakket. EEA het aangetoon dat die druklimiete voorgeskryf deur die buisvervaardiger (GEA Air Cooled Systems) nie noemenswaardige vervorming van die buise tot gevolg gehad het nie. Termiese belastings het 'n groot invloed op die eerste buise (die rye naaste aan die flense) van 'n buisbundel. Die invoeging van uitsettingslaste word aanbeveel om die spannings hier te verminder. Om vibrasie van die buisbundel te verhoed word aanbeveel dat die resonansfrekwensie van die buisbundel nie gelyk is aan die aantal lemme (N) vermenigvuldig met die rotasie frekwensie (co)van die waaier vir elke vibrasiemode.

This work reports on the design, fabrication and testing of a thermal switch wherein the open and closed states are actuated by shape memory alloy elements while heat is transferred by a heat-pipe. The motivation for such a switch comes from NASA's need for thermal management in advanced spaceport applications associated with future lunar and Mars missions. For example, as the temperature can approximately vary between 40 K to 400 K during lunar day/night cycles, such a switch can reject heat from a cryogen tank in to space during the night cycle while providing thermal isolation during the day cycle. By utilizing shape memory alloy elements in the thermal switch, the need for complicated sensors and active control systems are eliminated while offering superior thermal isolation in the open state. Nickel-Titanium-Iron (Ni-Ti-Fe) shape memory springs are used as the sensing and actuating elements. Iron (Fe) lowers the phase transformation temperatures to cryogenic regimes of operation while introducing an intermediate, low hysteretic, trigonal R-phase in addition to the usual cubic and monoclinic phases typically observed in binary NiTi. The R-phase to cubic phase transformation is used in this application. The methodology of shape memory spring design and fabrication from wire including shape setting is described. Heat transfer is accomplished via heat acquisition, transport and rejection in a variable length heat pipe with pentane and R-134a as working fluids. The approach used to design the shape memory elements, quantify the heat transfer at both ends of the heat pipe and the pressures and stresses associated with the actuation are outlined. Testing of the switch is accomplished in a vacuum bell jar with instrumentation feedthroughs using valves to control the flow of liquid nitrogen and heaters to simulate the temperature changes. Various performance parameters are measured and eported under both transient and steady-state conditions. Funding from NASA Kennedy Space Center for this work is gratefully acknowledged.
M.S.
Masters
Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science

Thesis (MDiploma (Mechanical Engineering))--Cape Technikon, 1992.
An investigation into the use of thermoelectric cooling energised by photovoltaic (PV) panels for removing sensible heat from electronic telecommunications equipment. The thermoelectric cooler consists of a solid-state heat pump which operates on the principle of the Peltier effect. The thermoelectric device transfers heat through a cold sink to ambient outside air via a hot sink. A major prerequisite was that the system should be selfsufficient in terms of power because the sites for the microwave transmitters are often remote. Solar power was the only alternative source of energy and the cooler was designed to accept direct current from PV panels which are usually used to power transmitters on distant locations. The cooling device had to be reliable, virtually maintenance-free and simple to repair.

In a worldwide pursuit for more Accident Tolerant nuclear Fuel (ATF), the quest to obtain and certify alternative nuclear fuel cladding tubes for light-water nuclear power reactors is still a key challenge. One of the facets in this program to develop more ATF is the heat transfer evaluation between the various proposed clad tubes manufactured from suitable replacement materials and the current problematic zirconium-alloy based clad tubes used in nuclear power reactors. For the heat transfer analysis, the accurate measurement of the temperature on the heat transfer surface of heated tubes to be tested was one of the important objectives for the effective analysis of the heat transfer characteristics to the water coolant. After extensive investigations, a suitable technique was developed and validated against recognised forced-convection heat transfer correlations. The results showed that this technique was well suited for external forced convection heat transfer studies from heated surfaces exposed to forced convection water coolants.
Dissertation (MSc)--University of Pretoria, 2019.
Mechanical and Aeronautical Engineering
MSc (Applied Science - Mechanics)
Unrestricted

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The potential benefits from saving energy have driven most industrial processing facilities to pay more attention to reducing energy wastage. Because the industrial sector is the largest user of electricity in South Africa (37.7% of the generated electricity capacity), the application of waste heat recovery and utilisation (WHR&U) systems in this sector could lead to significant energy savings, a reduction in production costs and an increase in the efficiency of industrial processes. Turbines are critical components of WHR&U systems, and the choice of an efficient and low cost turbine is crucial for their successful implementation. The aim of this thesis project is therefore to validate the use of a turbine for application in a low grade energy WHR&U system. An experimental turbine kit (Infinity Turbine ITmini) was acquired, assembled and tested in a specially designed and built air test bench. The test data was used to characterise the turbine for low temperature (less than 120 Celsius) and pressure (less than 10 bar) conditions. A radial inflow turbine rotor was designed, manufactured and then tested with the same test bench, and its performance characteristics determined. In comparison with the ITmini rotor, the as-designed and manufactured rotor achieved a marginally better performance for the same test pressure ratio range. The as-designed turbine rotor performance characteristics for air were then used to scale the turbine for a refrigerant-123 application. Future work should entail integrating the turbine with a WHR&U system, and experimentally determining the system’s performance characteristics.
AFRIKAANSE OPSOMMING: Die potensiële voordele wat gepaard gaan met energiebesparing het die fokus van industrie laat val op die bekamping van energievermorsing. Die industriële sektor is die grootse verbruiker van elektrisiteit in Suid-Afrika (37.7% van die totale gegenereerde kapasiteit). Energiebesparing in die sektor deur die toepassing van afval-energie-herwinning en benutting (AEH&B) sisteme kan lei tot drastiese vermindering van energievermorsing, ‘n afname in produksie koste en ‘n toename in die doeltreffendheid van industriële prosesse. Turbines is kritiese komponente in AEH&B sisteme en die keuse van ‘n doeltreffende lae koste turbine is noodsaaklik in die suksesvolle implementering van dié sisteme. Die doelwit van hierdie tesisprojek is dus om die toepassing van ‘n turbine in ‘n lae graad energie AEH&B sisteem op die proef te stel. ‘n Eksperimentele turbine stel (“Infinity Turbine ITmini”) is aangeskaf, aanmekaargesit en getoets op ‘n pasgemaakte lugtoetsbank. Die toetsdata is gebruik om die turbine te karakteriseer by lae temperatuur (minder as 120 Celsius) en druk (minder as 10 bar) kondisies. ‘n Radiaalinvloeiturbinerotor is ook ontwerp, vervaardig en getoets op die lugtoetsbank om die rotor se karakteristieke te bepaal. In vergelyking met die ITmini-rotor het die radiaalinvloeiturbinerotor effens beter werkverrigting gelewer by diselfde toetsdruk verhoudings. Die werksverrigtingkarakteristieke met lug as vloeimedium van die radiaalinvloeiturbinerotor is gebruik om die rotor te skaleer vir ‘n R123 verkoelmiddel toepassing. Toekomstige werk sluit in om die turbine met ‘n AEH&B sisteem te integreer en die sisteem se werksverrigtingkarakteristieke te bepaal.

Rising energy demands and the continual push to find more energy efficient technologies have been the impetus for the investigation of waste heat recovery techniques. Diesel engine exhaust heat utilization has the potential to significantly reduce the consumption of fossil fuels and reduce the release of greenhouse gases, because diesel engines are ubiquitous in industry and transportation. The exhaust energy can used to provide refrigeration by implementing an organic Rankine cycle coupled with a vapor-compression cycle. A critical component in this system, and in any waste heat recovery system, is the heat exchanger that extracts the heat from the exhaust. In this study, a cross-flow microchannel heat exchanger was geometrically examined and thermally tested under laboratory conditions. The heat exchanger, referred to as the Heat Recovery Unit (HRU), was designed to transfer diesel exhaust energy to a heat transfer oil. Two methods were developed to measure the geometry of the microchannels. The first was based on image processing of microscope photographs, and the second involved an analysis of profilometer measurements. Both methods revealed that the exhaust channels (air channels) were, on average, smaller in cross-sectional area by 11% when compared to the design. The cross-sectional area of the oil channels were 8% smaller than their design. The hydraulic diameters for both channel geometries were close to their design. Hot air was used to simulate diesel engine exhaust. Thermal testing of the heat exchanger included measurements of heat transfer, effectiveness, air pressure drop, and oil pressure drop. The experimental results for the heat transfer and effectiveness agreed well with the model predictions. However, the measured air pressure drop and oil pressure drop were significantly higher than the model. The discrepancy was attributed to the model's ideal representation of the channel areas. Additionally, since the model did not account for the complex flow path of the oil stream, the measured oil pressure drop was much higher than the predicted pressure drop. The highest duty of the Heat Recovery Unit observed during the experimental tests was 12.3 kW and the highest effectiveness was 97.8%. To examine the flow distribution through the air channels, velocity measurements were collected at the outlet of the Heat Recovery Unit using a hot film anemometer. For unheated air flow, the profile measurements indicated that there was flow maldistribution. A temperature profile was measured and analyzed for a thermally loaded condition.
Graduation date: 2012

Last leaf includes a list of publications co-authored by the author during the preparation of this thesis.
Includes bibliographical references (leaves 179-187).
xiv, 188 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
A novel and reliable method for heat exchanger network synthesis is proposed.The prime objective has been the elimination or reduction of drawbacks inherent in both evolutionary methods and mathematical programming methods while retaining the adevantages of both methods.
Thesis (Ph.D.)--Adelaide University, Dept. of Chemical Engineering, 2001

Bibliography: leaves 273-287.
xviii, 289 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
The aim of this thesis is to develop a new method for the conceptual design of heat exchanger networks. The initial designs can be optimized using conventional non-linear optimization techniques in the subset of the problem's initial dimensionality.
Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1994

A new adhesive bonding method is introduced for microlamination architectures, for producing low-temperature microchannel arrays in a wide variety of metals. Sheet metal embossing and chemical etching processes have been used to produce sealing bosses and flow features, resulting in approximately 50% fewer laminae over traditional methods. These lamina designs are enabled by reduced bonding pressures required for the new method. An assembly process using adhesive dispense and cure is outlined to produce leak-free devices. Feasible fill ratios were determined to be 1.1 in general and 1.25 around fluid headers, largely due to gaps between faying surfaces caused by surface roughness. Bond strength investigation reveals robustness to surface conditions and a bond strength of 5.5-8.5 MPa using a 3X safety factor. Dimensional characterization reveals a two sigma (95%) post-bonded channel height tolerance under 10% (9.6%) after bonding. Patterning tolerance and surface roughness of the faying laminae were found to have a significant influence on the final postbonded channel height. Leakage and burst pressure testing on several samples has established confidence that adhesive bonding can produce leak-free joints. Operating pressures up to 413 kPa have been satisfied, equating to tensile pressure on bond joints of 1.9 MPa. Higher operating pressures can be accommodated by increasing the bond area of devices. A two-fluid counterflow microchannel heat exchanger has been redesigned, fabricated and tested to demonstrate feasibility of the new method. Results show greater effectiveness and higher heat transfer rates, suggesting a smaller device than the original heat exchanger. A maximum effectiveness of 82.5% was achieved with good agreement between theoretical and experimental values. Although thermal performance was improved, higher pressure drops were noted. Pressure drops were predicted with a maximum error of 16% between theoretical and experimental values. Much of the pressure drop was found to be in the device manifolds, which can be improved in subsequent designs. Fluid flow simulation results show a 45-65X reduction in fluid leakage velocity past sealing bosses, thereby mitigating adhesive erosion concerns. Theoretical models indicate that the worst-case adhesive erosion rate is 1/12th the rate of aluminum and 1/7th the rate of stainless steel, implying satisfactory reliability in high fluid velocity applications. Economic comparison indicates an 83% reduction in material cost and 71% reduction in assembly cost with the new adhesive bonding process, when compared to diffusion bonding for the recuperator investigated in this study. Adhesive compatibility with common refrigerants is reviewed through literature references, with no adverse compatibility issues noted. The findings of this research suggest a fairly quick path to commercialization for the new bonding method. Future studies required to pursue commercialization are liquid and gas permeability evaluations, and long term strength and performance testing of adhesives in targeted applications.
Graduation date: 2012
Access restricted to the OSU Community at author's request from Mar. 26, 2012 - Mar. 26, 2013

M. Tech. Engineering Technology .
Demonstrates through design and experiments the heat transfer effectiveness of energy recovery from waste gases by using a heat exchanger. To use the heat exchanger to intercept the waste gases before they leave the process, extract some of the heat in the gases and use the same for preheating/heating the process water. The experiment is also intended to demonstrate whether or not waste heat unit has an effect on the emissions released to the environment. Diesel engines have been widely used in heavy-duty vehicles for their better fuel efficiency and higher power output than gasoline engines. However, the emissions of gas (CO, HC and NOx) and particulate matter (PM) pollutants from the diesel engine receive much concern from the general public and environmental researchers because of the epidemiological and toxicological investigations suggesting a relationship between exhaust pollutants exposure and adverse health effects.

Vortex tube (VT) is a mechanical device with no moving parts. The fundamental principle of Vortex Tube is that it can split an incoming fluid flow of a constant pressure and constant temperature gas stream into two separate low pressure streams, one having higher enthalpy and the other having lower enthalpy than the inlet flow. So this device essentially works as a temperature separator. On separation from the device, a warmer flow exits through a terminal which is called the “hot end” and a low temperature stream comes out from another terminal known as the “cold end”. Just with a few bar pressure of compressed air at room temperature can produce a hot stream temperature of about 150°C and a cold stream temperature of about - 40°C. This temperature separation scheme allows us to get cooling and heating effect simultaneously using the same device which makes the Vortex tube one of the popular mechanical equipment and is used in many fields of engineering. The cooling or heating effect produced by this device is largely dependent on geometric parameters of the device itself. Since no exact theoretical correlation is there between the geometric parameters and the cooling (or heating) effect produced, VT design is solely based on empirical relations. There are quite a few geometric parameters which affect the cooling effect of this device and all the empirical correlation are needed to design the optimum VT for maximum cooling/heating effect. These relations can be derived in two ways, either by numerical methods or by experimental investigations. The first part of the thesis important geometric parameter of the VT namely the ratio of the “cold end” diameter (to the “tube diameter” , which has been numerically optimized in this work to achieve maximum temperature separation. In our efforts to design a VT based refrigeration system, optimization of the VT itself is not enough. A suitable heat exchanger (HX) which can extract the cold enthalpy from the VT also needs to be designed and cascaded with the VT to get the complete refrigeration system. The second part of the thesis is solely dedicated to the design of a suitable HX that can be used alongside a VT to produce refrigeration. The HXs design can be approached from two directions, dimensional aspect and material aspect. Rather than focusing on the dimensional aspect in this work we have concentrated of the material aspect of HX design. It is fairly obvious that the thermal conductivity (TC) of the HX material will play a crucial role on the cooling effect of the refrigeration system. Conventional metals with high TC can be used to design HXs but the downsides of using pure metals such as Copper, Iron are that they are heavy, quite expensive and highly reactive to corrosive fluids. Because of this, high TC ceramic material such as Aluminium Nitride (AlN) is quite often used to fabricate HXs and they are used for spot cooling in electronic systems. AlN has TC of 160 W/m-K which is high but not as high as of Copper or Iron. TC of AlN can be increased by mixing the right volume fraction of metal powder (such as pure Aluminium) with it to a great extent. So in a nutshell, instead of using pure AlN, if we use the particle reinforced binary composite [AlN + Al (powder)] to design a HX, we would achieve the benefits of having high TC as well as properties such as anti-corrosiveness, cost effectiveness and weight reduction. In the above context, prediction of TC of particle reinforced composite materials containing a base material of low TC and a filler material of high TC is of utmost importance. Till now a very few analytical heat transfer models are available in the literature that can accurately predict the TC value of such composites especially when high volume fraction of filler particles is added to the base material or if more than one type of filler particles are added. So in this thesis, three analytical heat transfer models have been developed that can predict the TC of binary as well as tertiary particle reinforced composites. The third and the final segment of the thesis deals with the performance study of a refrigeration system comprised of the optimized VT cascaded with a suitable HX made out of a particle reinforced composite material. The numerical results show how the HX effectiveness improves as the volume fraction of the filler particles in the composite increases. The key results of the works described in the thesis are as follows: • Through extensive numerical simulations it is shown that for = 0.5, the temperature separation in a VT is maximum. • The heat transfer models developed to predict the thermal conductivity of binary composites, shows the trend of how thermal conductivity varies with increasing volume fraction of filler. It has been shown that initially the thermal conductivity increases linearly with a small slope, then after a critical volume fraction an abrupt increment of slope is observed due to the formation of continuous heat conduction paths within the composite. Further increase in volume fraction shows linear increment of thermal conductivity with lesser slope as before. • The heat transfer model developed to predict the thermal conductivity of tertiary composites is suitable for low volume fraction (< 20 %). The model shows the addition of one component into the base matrix affects the distribution of the other component which is observed through the covariance. • The last part of the thesis shows that compared to a pure AlN heat exchanger, a heat exchanger made of AlN + 30 % volume fraction of pure Aluminium powder, has increased heat exchanger effectiveness by more than 50 %. Thesis outline is as follows: • Chapter 1 is a brief introduction to Vortex Tube. • Chapter 2 deals with the necessary literature review related to Vortex Tube as well as presently available heat transfer models that are equipped to handle composite materials to predict their TC. • Chapter 3 elaborates numerical modeling and optimization of a critical parameter ( to achieve maximum temperature separation in a VT. • Chapter 4 presents a stochastic heat transfer model to estimate the TC of Binary particle reinforced composites containing low volume fraction of filler particles. • Chapter 5 describes the development of a computational heat transfer model to predict the TC of Particle Reinforced Binary Composite materials containing high volume fraction of filler element. • Chapter 6 deals with a stochastic heat transfer model to calculate TC of Particle Reinforced Tertiary Composite materials containing low volume fractions of filler elements. • Chapter 7 consolidates all the necessary concepts and data from previous chapters to design the final cascaded VT based refrigeration system and presents a performance study. • The last chapter summarizes the entire work along with scope for future work.

The need for clean and renewable fuel such as hydrogen is driven by a growing worldwide population and increasing air pollution from fossil fuels. One of the major barriers for the use of hydrogen in automotive industry is the storage of hydrogen. Physisorption is the most promising storage technique due to its high storage density, reversibility and rapid sorption kinetics besides being safe and volume-efficient. A major challenge for physisorption is the need to manage the heat of adsorption at cryogenic temperatures. In this thesis, a 6061 aluminum microchannel cooling plate is designed to remove the equivalent heat flux required by the adsorption of hydrogen within an adsorption bed. Therefore, the objective of this thesis is to determine whether laser welding and heat treating strategies can be developed for a 6061 aluminum microchannel cooling plate as part of a larger hydrogen storage thermal management system. Key manufacturing process requirements include controlling the hermeticity, strength and dimensional stability of the heat-treated weld joint. A hermetic microchannel cooling plate was successfully laser welded and heat treated using free convection in air to quench the solution heat treatment. The weld strength and warpage obtained were within acceptable limits. Experimental testing of the fabricated microchannel cooling plate showed acceptable percent error with an experimental heat removal rate within 13.4% of computational fluid dynamics (CFD) analyses and an average pressure drop error of 25%. Calculations show that the cooling plate developed could support a hydrogen storage thermal management system taking up 5.0% and 10.3% of the system displacement volume and mass, respectively.
Graduation date: 2013