The successful industrial applications of pinch analysis techniques in energy optimisation and wastewater minimisation have resulted in the recent studies of combined mass and heat integration. Kim and Smith (2001) have demonstrated that operation of cooling water networks in series, rather than the conventional parallel arrangement improve cooling tower and cooling water network performance in new and retrofit design. In this work, utilising a superstructure to determine the mathematical formulation that characterises a cooling water network supplied by multiple cooling water sources, which often occurs in practice, extends this methodology. It is further demonstrated that the optimum cooling water supply to a network of cooling-water-using operations supplied by multiple sources is determined by considering the entire framework of sources and cooling-water-using operations, that is, unified targeting. This optimum is better than that obtained from considering individual subsets of cooling-water-using operations and its respective source, that is, single source targeting. Relevant practical constraints were included in the formulations to enhance robustness and applicability to real life situations. Practical constraints consisted of maximum return temperatures to cooling water sources, as wells as dedicated water sources and sinks of cooling-water-using operations. This concept was applied to an illustrative example and a case study of the Sasol Synfuels (Pty) Limited cooling water system that consisted of individual networks supplied by separate water sources. For the case with maximum water reuse the single source targeting method yielded an improvement of 11.6% over the parallel target for the illustrative example. In comparison, superior results were obtained with the developed unified targeting method, which yielded an improvement of 18.4%. Likewise, for the case with the aforementioned practical constraints 6.8% and 7.6% improvements were forecasted for the single source and unified targeting methods respectively. For the maximum reuse scenario of the case study, improvements of 37.9% and 41.0% over the parallel target were obtained using the single source and unified targeting methods, respectively. Similarly, considering practical constraints improvements of 20.3% and 31.1% were obtained. In both the illustrative example and case study the unified targeting method resulted in superior results than the single source targeting methods. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2008. / Chemical Engineering / unrestricted

Cooling water systems are generally designed with a set of heat exchangers arranged in parallel. This arrangement results in higher cooling water flowrate and low cooling water return temperature thus reducing cooling tower efficiency. Previous research on cooling water systems has focused mainly on heat exchanger network thus excluding the interaction between heat exchanger network and the cooling towers. The studies completed on cooling water system in which the interaction between the cooling tower and the heat exchanger network was taken into consideration were limited to systems with single cooling tower. The main aim of this study was to develop a design methodology for synthesis and optimization of cooling water systems with multiple cooling towers. The design intends to debottleneck the cooling towers by reducing the circulating water flowrate. The study focuses mainly on cooling systems consisting of multiple cooling towers that supply a common set of heat exchangers. In this work the mathematical optimization technique was developed for optimization and synthesis of cooling water system. The heat exchanger network was synthesized using the mathematical optimization technique. This technique is based on superstructure in which all opportunities for cooling water reuse are explored. The cooling tower model was used to predict the thermal performance of the cooling towers while taking the thermal conditions of the associated heat exchanger network into account. The propose technique debotlleneck the cooling towers by decreasing the circulating water flowrate. This implies that a given set of cooling towers can manage an increased heat load. From the case studies, 22% decrease in circulating water flowrate was realized. The blowdown and makeup were also decreased by 7%. Furthermore, the cooling tower effectiveness was also improved by 4%. A decrease in the overall circulation water has an added benefit of decreasing the overall power consumption of the circulating pumps. There is also a potential for the reduction of makeup and blowdown water flowrate. / Dissertation (MEng)--University of Pretoria, 2011. / Chemical Engineering / unrestricted

The simulation of vehicle engine cooling validation in a Climatic chamber will benefit all vehicle manufacturers that are responsible for the design or the localization of parts used in a vehicle's engine cooling system. The ability to test the vehicle in-house allows testing at any time of the year; it provides repeatable and comparative data, and accelerates component level approval, which in itself reduces program timing and cost. For this dissertation road level testing was conducted in Upington using a TD1200 Superflow towing dynamometer, while the in-house testing was performed on a ROTOTEST chassis dynamometer in a Climatic chamber. All tests were conducted according to GENERAL MOTORS SOUTH AFRICA global testing standards. Statistical analyses of the test data were used to determine the relationship between parameters measured and results obtained. The major contributors to the simulation process was identified and implemented to improve measurement quality and test results. The result was an accurate simulation between road and chamber testing, hence the possibility of moving away from road testing and conduct simulated chamber testing. The presented dissertation is useful for the understanding of basic vehicle cooling testing and the methodology of simulated testing in an environmentally controlled chamber.

The spray cooling system of an operating billet caster has been redesigned with the aim of reducing the formation of mid-way cracks. These cracks are caused by tensile strain which is generated at the solidification front when the surface temperature of the strand rebounds owing to a sharp reduction in surface heat extraction. The objective of the design, therefore, was to achieve a cooling system that would minimize surface temperature rebound of the strand as it passes from one cooling zone to the next. A computer program based on the explicit finite difference method has been used for the design work. The spray design was implemented on one strand of an operating continuous casting machine which produced 10.8 cm square billets. Transverse sections were cut from the test strand and sulfur printed, then compared to sulfur prints of sections taken from an adjacent strand of the same heat but with unmodified sprays. It was shown that with empirical adjustment, the redesigned spray system reduced the severity of mid-way cracks in over 80% of the heats. It was also found that the carbon content and cast structure have a profound effect on the cracking tendency, whereas, the Mn/S ratio (up to 30%) is less effective. Finally, a new design method for sprays has been proposed which may result in a better temperature distribution and may be easier to adjust to suit specific operating conditions. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The use of seawater in cooling towers for industrial applications has much merit in the Gulf Cooperation Council countries due to the scarcity and availability of fresh water. Seawater make-up in cooling towers is deemed the most feasible because of its unlimited supply in coastal areas. Such latent-heat removal with seawater in cooling towers is several folds more efficient than sensible heat extraction via heat exchangers. Operational challenges such as scaling, corrosion, and biofouling are a major challenge in conventional cooling towers, where the latter is also a major issue in seawater cooling towers. Biofouling can significantly hamper the efficiency of cooling towers. The most popular methods used in cooling treatment to control biofouling are disinfection by chlorination. However, the disadvantages of chlorination are formation of harmful disinfection byproducts in the presence of high organic loading and safety concerns in the storage of chlorine gas. In this study, the research focuses on biofouling control in seawater cooling towers by investigating two different approaches. The first strategy addresses the use of alternative oxidants (i.e. ozone micro-bubbles and chlorine dioxide) in treatment of cooling towers. The second strategy investigates removing nutrients in seawater using granular activated carbon filter column and ultrafiltration to prevent the growth of microorganisms. Laboratory bench-scale tests in terms of temperature, cycle of concentration, dosage, etc. indicated that, at lower oxidant dosages (total residual oxidant (TRO) equivalent = 0.1 mg/l Cl2), chlorine dioxide had a better disinfection effect than chlorine and ozone. The performance of oxidizing biocides at pilot scale, operating at assorted conditions, showed that for the disinfectants tested, ozone could remove 95 % bioactivity of total number of bacteria and algae followed by chlorine dioxide at 85%, while conventional chlorine dosing only gave 60% reduction in bioactivities. Test results of GAC bio-filter showed that around 70 % removal of total organic carbon in the seawater feed was achieved and was effective in keeping the microbial growth to a minimum. The measured results from this study enable designers of seawater cooling towers to manage the biofouling problems when such cooling towers are extrapolated to a pilot scale.

<p>Radiative cooling is an approach that utilizes the material reflectance in solar spectrum to reflect solar irradiation and emit the energy to deep space (2.7K) through the transparent portion in atmosphere (8-13μm). Therefore, radiative cooling is a passive cooling method that can generate a large reduction in energy consumption in the cooling sector. Scientists have been researching on the best solution for passive radiative cooling, including the utilization of multi-layer techniques with a metallic base layer. However, the current solutions are usually not cost effective and thus limited in the commercial applications. We initially started with the experiment on single-layer cooling paints embedded with TiO₂nanoparticles, and we were able to achieve a partial daytime radiative cooling effect of 60Wm^-2 Built upon our lab’s success of full-daytime sub-ambient cooling based on BaSO₄-acrylic paints, we experiment with colored cooling paints based on BaSO₄ nanoparticles instead of TiO₂ nanoparticles. Our results show much enhanced solar reflectance while matching the color, indicating the potential for colored cooling paints, although outdoor tests have not shown significant temperature drop compared to commercial colored paints yet. At the same time, we also explore creatures with shells in nature for possible solutions. Seashells are collected and the microstructures and radiative properties are characterized. The results provide insights into bio-inspired radiative cooling solutions.</p>

Diploma work is bent on technology production cold with usage absorbing circulations powered heat energy. Work it is possible divide by to the of several part. First volume of work is introduction tenet absorbing circulations, their elements, division, applicable working couple, basic operation parameters and possibilities realized solar refrigerating systems. Alternative part smoothing - out practical page. Elaboration project proposal wiring solar refrigerating system with absorbing period, about refrigerating achievement 6 kW and processing constructional proposal personal refrigerating troop. In fine will basic technical economic juxtaposition solar refrigerating troop with compressor refrigerating period

Kyla produceras med ett antal helt skilda metoder. Denna rapport och fallstudie tar hänsyn till fyra metoder för kylning, kompressordriven-, absorptions-, fri-, och fjärrkyla. En del i problematiken är att systemen har mycket olika tekniska utformningar och krav på fastigheten, så som geografi och närhet till stora tekniska system som fjärrvärme och fjärrkyla. Kylsystemen jämfördes för att finna vilket kylsystem som var lämpligast samt vilket som hade den mest gynnsamma taxeringen för fastigheten. Kylsystemens lämplighet bedömdes framförallt efter underhållsbehov, men även storlek och ljudnivå. Fastigheten som utgör examensarbetets studieobjekt har ett kylbehov på 150 kW, vilket attribueras ett bageri, restaurang, kontor samt kylbänkar m.fl. Dessa har ett kylbehov under framförallt fyra sommarmånader, där kylbänkar m.fl även har ett kylbehov under resterande året. Flera studier har gjorts och pekar på att kylbehovet i framtiden kommer att öka, även om en exakt prognos inte kan ges. Det är även tydligt att alla de ovan nämnda kylsystemslösningarna har en roll att spela framöver. Examensarbetet har framförallt använt sig av en litteraturstudie för att besvara frågeställningarna. För litteraturstudien användes hemsidor som Discovery och ScienceDirect. För att beräkna energiförbrukning, drifttider och total kostnad så har Microsoft Excel använts. Framförallt för kylproduktion med kompressor, där det givna referensaggregatet har fyra olika driftfall beroende på kylbehov, varav ett är kylproduktion med frikyla. För att vikta frikylans andel har klimatdata från SMHI (2020) använts. Programmet har även använts för att sammanställa de tabeller och figurer som presenteras i resultatet. Prisförslag har givits efter personliga kommunikation per e-mail och telefonintervjuer med energiproducenter och tillverkare av kylaggregat. Resultatet visade att fjärrkyla var det för studieobjektet mest lönsamma alternativet, det står även för det system som är lämpligast då det är helt underhållsfritt för kunden. Anledningen till dess lönsamhet tillskrevs framförallt dess låga investeringskostnad. Att använda Gavleån för ren frikyla visade sig inte vara möjligt då temperaturen i ån är för hög sommartid. Även absorptionskyla visade sig vara olämpligt för studieobjektet då temperaturen i det lokala fjärrvärmenätet är för låg samtidigt som investeringskostnaden blivit hög. För absorptionskyla hade ett extra system behövts installeras, vilket rapporten inte kunnat prissätta. Rapporten visar däremot att metoden att producera kyla med absorptionsaggregat har potential att under rätt förutsättningar ersätta kompressorkyla. Detta för att minska dels belastningen på elnätet samt som ett sätt att minska CO2-utsläpp globalt, genom export av elektricitet till Europa. Detta arbete visar att dagens teknik är begränsad men att framtida teknik visar sig ha potential. Rapporten fann även att vidare arbete med vinning kunnat utföras för att identifiera absorptionskylas expansionspotential. / Cooling is produced with several completely differentiated methods. This report and case study considers four different methods of cooling, vapor-compression-, absorption-, free- and district cooling. A part of the problem is that the systems have vastly different technical configuration and requirement of a facility, such as geography and vicinity to other big technical system such as district cooling and district heating. The cooling systems are compared to find the method that is most suitable and has the most beneficial assessment. The different methods suitablitiy was graded based on, noise level, size and required maintenance. The facility that constitutes this thesis study has a cooling demand of 150kW, which is attributed to a bakery, a restaurant, an office and cooling benches etc. These have a cooling demand during four summer months, where cooling benches etc also have a demand during the rest of the year. Multiple studies showcase and point out that the cooling demand will grow in the future, even if a precise prognosis is not made. It is also clear that these above-mentioned cooling systems have a continuing role to play going forward. This thesis has foremostly used a literature review to answer the research questions. For the review webpages such as Discovery and ScienceDirect was used. To calculate the energy consumption, running hours and total yearly cost Microsoft Excel was used. Especially when cool produced with the compressor unit. The reference unit has four different operating modes depending on the cooling demand, one of the modes is production with free cooling. To value the share and impact that free cooling has, Microsoft Excel is used in combination with statistical data from SMHI (2020). Microsoft Excel is also used to compile the tables and figures in the “results” section. The pricing published in this report is based on personal communications per e-mail and phone interviews with energy producers and manufacturers of different cooling units. The result of the thesis show that district cooling is the most beneficial solution for cooling the facility. As well as the most suitable system since it is completely maintenance free for a customer. The reason for its profitability is attributed to its low investment cost. Using the nearby river for free cooling was deemed impossible because of its high temperature during the summers. Using absorption cooling was also considered unsuitable for the case object because of the low temperature in the local district heating network during summer times, as well as the high investment cost required because of it. To make absorption cooling suitable an additional system for cooling the processes would have to be installed, which this report has not been able to price.

The Long-term changes in the climate conditions have increased the need foradequate thermal comfort systems. These alternations influence extremeevents, which their intensity and frequency have increased over the past years.Moreover, this study focuses on space cooling and parameters that the systemshould have to be considered as resilient. Literature study was done to presentthe concept of resilience as well as the different methods used to provide spacecooling. In addition, the cooling systems suggested in this study, which aredistrict cooling and absorption cooling, were presented and explained.Furthermore, the study focuses on cooling demand in a group of residentialbuildings based on different thermal characteristics, which were implementedbased on building regulations from late 1960s to early 1980s. The buildingthermal properties were used as input to obtain their cooling demand by usingbuilding energy simulation tool. Based on the acquired results, an evaluationhas been made for the cooling demand of those buildings. Further analysispresented a correlation between the cooling demand and thermal properties ofthe buildings and aided in the determination of the required cooling capacity.The selection of the capacities was based on the resilience criterion as the systemhas to be able to provide adequate performance and safety for the occupantsduring extreme events. Furthermore, an assessment was done to compare thesuggested system based on their capacities and the primary energy use.

The work presented in this master thesis deal with the issue of quenching, investigation regarding different cooling rates and its effect on the material properties of aluminum alloy in the 6xxx series used for crash purposes in cars, such as crash boxes, beams and other crash relevant parts. Precipitation of Mg2Si due to different cooling rates affects the material properties such as crash performance, thus the aluminum alloy used is sensitive to different cooling rates. In order to perform tests with different cooling rates a cooling rig was constructed. In order to evaluate the different cooling rates both mechanical testing such as tensile test and 3-point bending test and compression test were performed. Also analyses with scanning electron microscope/energy-dispersive x-ray spectroscopy were performed to estimate grain boundary decoration of Mg2Si due to the different cooling rates. Furthermore LOM analyses were performed to evaluate if the experimental setup had any effect on material properties such as grain size. The constructed cooling rig produced different cooling rates with reliable repeatability as intended. Cooling rates between 130 ̊C/s and 20 ̊C/s were accomplished. Mg2Si occurred in all investigated test samples with various amounts. Higher cooling rates decreases the precipitation of Mg2Si to the grain boundaries, higher cooling rates also increased the bending angle achieved from the 3-point bending test. Furthermore, extensive solution heat treatment at elevated temperatures leads to grain growth.