A study of ammonia-water desorption in compact counter-flow geometries was conducted. Two novel vapor generation units, comprising integrated desorber, analyzer, and rectifier segments that use microchannel geometries, were conceptualized. The branched-tray concept features a desorber segment that uses predominantly pool-boiling mechanisms for desorption, while the vertical column desorber relies on falling-film evaporation and boiling mechanisms. Both concepts rely on falling-film heat and mass transfer mechanisms in the analyzer and rectifier sections. Segmented heat and mass transfer models, based on available correlations and modeling methodologies, were developed and used for the design of branched tray and vertical column test sections. An experimental facility was designed and constructed to evaluate desorption and rectification heat and mass transfer processes within these components, under realistic operating conditions. Data were analyzed to determine the boiling/evaporation (desorber) and condensation (rectifier) heat transfer coefficients, and to determine values of the desorber liquid and vapor mass transfer coefficients. Additionally, high-speed video and images were used to gain insights into the hydrodynamic phenomena and heat transfer mechanisms in these vapor generation units. Results of the heat and mass transfer analysis were compared with the predictions of correlations and modeling methods in the literature. The vapor generation unit (VGU) test sections were evaluated across a range of concentrated solution mass fractions (0.400 – 0.550), desorber coupling-fluid inlet temperatures (170 – 190ᵒC), and concentrated solution flow rates (0.70 – 1.3 g s-1). Flow rates in this range correspond to desorber liquid Reynolds numbers of approximately 175 to 410 for the branched tray design, and desorber film Reynolds numbers of approximately 90 to 215 for the vertical column. Pressures observed within the VGU test sections ranged from approximately 1620 to 2840 kPa during testing. The novel VGUs were shown to achieve ideal cooling capacities as high as 432 and 323 W for the branched tray and vertical column, respectively. This parameter indicates the cooling capacity that would be achieved by an idealized cooling system using the refrigerant stream produced by the experimental VGU. Ideal COPs of 0.561 and 0.496 were demonstrated for the branched tray and vertical column, respectively. Experimental heat transfer coefficients were found to range from approximately 1860 to 11690 W m-2 K-1 for the pool-boiling desorption of the branched tray VGU. A new correlation was proposed and shown to provide good agreement with the data, achieving average and average absolute deviation of -5.2 and 16.1%, respectively, across the range of conditions tested. Falling-film evaporation/boiling heat transfer coefficients, determined for the desorption process in the vertical column VGU, were found to range from approximately 1290 to 4310 W m-2 K-1. Rectifier condensation heat transfer coefficients ranging from approximately 160 to 250 W m-2 K-1 were observed. Mass transfer coefficients for the desorbers of both concepts were also quantified. These results were used to develop revised heat and mass transfer models of the VGU concepts. The revised models were demonstrated to predict component-level performance with reasonable accuracy, and may be used in the design of future compact VGUs with similar geometries and operating conditions.

An experimental investigation of heat and mass transfer in a horizontal tube falling-film ammonia-water absorber was conducted. A tube bank consisting of four columns of six 9.5 mm (3/8 ) nominal OD, 0.292 m (11.5 ) long tubes was installed in an absorber shell that allowed heat and mass transfer measurements and optical access. A test facility consisting of all the components of a functional absorption chiller was fabricated specifically for this investigation. Several variations of the basic system set up were fabricated to enable testing over the wide range of conditions (nominally, desorber solution outlet concentrations of 5 - 40% for three nominal absorber pressures of 150, 345 and 500 kPa, over solution flow rates of 0.019 0.034 kg/s.) Measurements at the absorber were used to determine heat transfer rates, overall thermal conductances, solution-side heat and vapor-side mass transfer coefficients for each test condition. For the range of experiments conducted, the solution heat transfer coefficient varied from 923 to 2857 W/m2-K while the vapor mass transfer coefficient varied from 0.0026 to 0.25 m/s and the liquid mass transfer coefficient varied from 5.51×10-6 to 3.31×10-5 m/s depending on the test condition. The solution heat transfer coefficient increased with increasing solution flow rate; however, the vapor and liquid mass transfer coefficients seem to remain unaffected with the variations in solution flow rate and were found to be primarily determined by the vapor and solution properties. The experimental heat and mass transfer coefficients were compared with the relevant studies from the literature. Based on the observed trends, heat transfer correlations and mass transfer correlations in the vapor and liquid phases were developed to predict heat and mass transfer coefficients for the range of experimental conditions tested. These correlations can be used to design horizontal tube falling-film absorbers for ammonia-water absorption systems.

Optimization of the performance of absorption systems during transient operations such as start-up and shut-down is particularly important for small-capacity chillers and heat pumps to minimize lifecycle costs. Dynamic models in the literature have been used to study responses to step changes in a single parameter, but more complex processes such as system start-up have not been studied in detail. A robust system-level model for simulating the transient behavior of an absorption chiller is developed here. Individual heat and mass exchangers are modeled using detailed segmental models. The UA-values and thermal masses of heat exchangers used in the model are representative of a practical operational chiller. Thermal masses of the heat exchangers and energy storage in the heat exchanging fluids are accounted for to achieve realistic transient simulation of the heat transfer processes in the chiller. The pressure drop due to fluid flow across the heat exchangers is considered negligible in comparison to the pressure difference between the high- and low-side components (~ 1.5 MPa). In components with significant mass transfer effects, reduced-order models are employed to decrease computational costs while also maintaining accurate system response. Mass and species storage in the cycle are modeled using storage devices. The storage devices account for expansion and contraction of the refrigerant and solution in the cycle as the system goes through start-up, shut-down, and other transient events. A counterflow falling film desorber model is employed to account for the heat and mass transfer interactions between the liquid and vapor phases, inside the desorber. The liquid film flows down counter to the rising vapor, thereby exchanging heat with the counterflowing heated coupling fluid. A segmented model is used to account for these processes, and a solver is developed for performing rapid iteration and quick estimation of unknown vapor and liquid states at the outlet of each segment of the desorber. Other components such as the rectifier, expansion valves and solution pump are modeled as quasi-steady devices. System start-up is simulated from ambient conditions, and the coupling fluid temperatures are assumed to start up to their steady-state values within the first 90 s of simulation. It is observed that the system attains steady-state in approximately 550 s. The evaporator cooling duty and COP of the chiller during steady-state are observed to be 3.41 kW and 0.60, respectively. Steady-state parameters such as flow rates, heat transfer rates and concentrations are found to match closely with results from simulations using corresponding steady-state models. Several control responses are investigated using this dynamic simulation model. System responses to step changes in the desorber coupling fluid temperature and flow rate, solution pumping rate, and valve setting are used to study the effects of several control strategies on system behavior. Results from this analysis can be used to optimize start-up and steady state performances. The model can also be used for devising and testing control strategies in commercial applications.

Energy shortages around the world necessitated research into alternative energy sources especially for domestic applications to reduce the load on conventional energy sources. This resulted in research done on the possibility of integrating solar energy with an aqua-ammonia diffusion absorption cycle specifically for domestic applications. The bubble pump can be seen as the heart of the diffusion absorption cycle, since it is responsible, in the absence of a mechanical pump, to circulate the fluid and to desorb the refrigerant (ammonia) from the mixture. It is thus of paramount importance to ensure that the bubble pump is designed efficiently. Various bubble pump simulation models have been developed over the years, but it was found that none of the existing models served as a good basis for application-specific design. Most of the models constrained too many parameters from the outset which made the investigation of the effects of certain parameters on the bubble pump’s performance impossible. According to the research, no bubble pump model investigated the effect of such a wide variety of factors including tube diameter, heat flux, mass flux, generator heat input and system pressure on the bubble pump’s lift height. A simulation model for a bubble pump for integration with a solar-driven aqua-ammonia diffusion absorption cycle was developed. It serves as a versatile design model to optimise the bubble pump for a large variety of conditions as well as changes in parameters. It was achieved by constraining the bubble pump dimensions and parameters as little as possible. A unique feature of this model was the fact that the bubble pump tube was divided into segments of known quality which made the length of the pipe completely dependent on the flow inside the pipe. It also made the demarcation of the flow development inside the tube easier. The model attempted to incorporate the most appropriate correlations for pressurised two-phase aqua-ammonia flow. The most appropriate void fraction correlation was found to be Abstract The design and optimisation of a bubble pump for an aqua-ammonia diffusion absorption heat pump the Rouhani-Axelsson (Rouhani I) correlation. It was mainly due to its exclusive use of thermophysical properties and the vapour quality. The most appropriate heat transfer coefficient that predicted the most realistic wall temperature, was the correlation from Riviera and Best (1999) which was the only correlation found in the literature developed with aqua-ammonia in mind. It was found that the published correlation could not reproduce their experimental results, and a modification of their correlation was made after which the simulation model’s results correlated well with the experimental values of Riviera and Best (1999). The main goal of the simulation model was to determine the height that the bubble pump was capable of lifting at the slug to churn flow transition under various conditions. The effect of varying a variety of parameters on the bubble pump lift height was also investigated. The results from Shelton & White Stewart (2002) were compared to the outputs of the simulation model, and it was found that their constraining of the submergence ratio limited their outputs, and that their heat inputs under different conditions was a bit optimistic. The simulation model’s outputs correlated well at higher tube diameters with the results from Shelton & White Stewart (2002), but at the lower diameters which was used in their study it was impossible to compare data, since their diameters was already in mini flow and micro flow regions. The temperatures also correlated well, all within 2% of the results from Shelton & White Stewart (2002). It was found that there couldn’t be just one set of optimised conditions and values for the bubble pump, but that each cycle with differing specifications and operating conditions would yield a unique set of optimised parameters. It was for that reason very important not to constrain parameters beforehand without investigating its effect on the bubble pump first. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.

Energy shortages around the world necessitated research into alternative energy sources especially for domestic applications to reduce the load on conventional energy sources. This resulted in research done on the possibility of integrating solar energy with an aqua-ammonia diffusion absorption cycle specifically for domestic applications. The bubble pump can be seen as the heart of the diffusion absorption cycle, since it is responsible, in the absence of a mechanical pump, to circulate the fluid and to desorb the refrigerant (ammonia) from the mixture. It is thus of paramount importance to ensure that the bubble pump is designed efficiently. Various bubble pump simulation models have been developed over the years, but it was found that none of the existing models served as a good basis for application-specific design. Most of the models constrained too many parameters from the outset which made the investigation of the effects of certain parameters on the bubble pump’s performance impossible. According to the research, no bubble pump model investigated the effect of such a wide variety of factors including tube diameter, heat flux, mass flux, generator heat input and system pressure on the bubble pump’s lift height. A simulation model for a bubble pump for integration with a solar-driven aqua-ammonia diffusion absorption cycle was developed. It serves as a versatile design model to optimise the bubble pump for a large variety of conditions as well as changes in parameters. It was achieved by constraining the bubble pump dimensions and parameters as little as possible. A unique feature of this model was the fact that the bubble pump tube was divided into segments of known quality which made the length of the pipe completely dependent on the flow inside the pipe. It also made the demarcation of the flow development inside the tube easier. The model attempted to incorporate the most appropriate correlations for pressurised two-phase aqua-ammonia flow. The most appropriate void fraction correlation was found to be Abstract The design and optimisation of a bubble pump for an aqua-ammonia diffusion absorption heat pump the Rouhani-Axelsson (Rouhani I) correlation. It was mainly due to its exclusive use of thermophysical properties and the vapour quality. The most appropriate heat transfer coefficient that predicted the most realistic wall temperature, was the correlation from Riviera and Best (1999) which was the only correlation found in the literature developed with aqua-ammonia in mind. It was found that the published correlation could not reproduce their experimental results, and a modification of their correlation was made after which the simulation model’s results correlated well with the experimental values of Riviera and Best (1999). The main goal of the simulation model was to determine the height that the bubble pump was capable of lifting at the slug to churn flow transition under various conditions. The effect of varying a variety of parameters on the bubble pump lift height was also investigated. The results from Shelton & White Stewart (2002) were compared to the outputs of the simulation model, and it was found that their constraining of the submergence ratio limited their outputs, and that their heat inputs under different conditions was a bit optimistic. The simulation model’s outputs correlated well at higher tube diameters with the results from Shelton & White Stewart (2002), but at the lower diameters which was used in their study it was impossible to compare data, since their diameters was already in mini flow and micro flow regions. The temperatures also correlated well, all within 2% of the results from Shelton & White Stewart (2002). It was found that there couldn’t be just one set of optimised conditions and values for the bubble pump, but that each cycle with differing specifications and operating conditions would yield a unique set of optimised parameters. It was for that reason very important not to constrain parameters beforehand without investigating its effect on the bubble pump first. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.

Orientador: Jose Ricardo Figueiredo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T16:34:55Z (GMT). No. of bitstreams: 1 Makiyama_PatriciaAkemi_D.pdf: 909858 bytes, checksum: 44f3dcd6439a819df8a8d16fa7f5d458 (MD5) Previous issue date: 2008 / Resumo: Este estudo apresenta o desenvolvimento de um programa pré-existente de simulação de um sistema de refrigeração por absorção água-amônia que utiliza como fonte de energia os gases de exaustão de um motor diesel de um grupo diesel-gerador. O projeto foi executado em quatro etapas. Um dimensionamento inicial dos diversos componentes envolveu relações puramente termodinâmicas, e baseou-se no arbítrio de diferenças de temperatura nos diversos trocadores de calor e algumas condições operacionais e ambientais, como capacidade de refrigeração e temperatura de entrada da água de resfriamento nos condensadores e absorvedor. Obteve-se, assim, o porte de cada equipamento do sistema de refrigeração em termos de parâmetros, tais como os coeficientes globais de transferência de calor multiplicado pelas áreas de cada componente ou a efetividade multiplicada pela mínima capacidade térmica horária. Na segunda etapa, foi feito o detalhamento construtivo de cada componente do sistema com o intuito de se chegar o mais próximo possível aos resultados do projeto inicial. Foram introduzidas as relações para o cálculo de transferência de calor de cada componente do sistema, o cálculo dos respectivos coeficientes de transferência de calor e as perdas de cargas relevantes ao cálculo da potência elétrica auxiliar demandada pelo sistema. Uma vez definida a configuração inicial de um sistema de refrigeração por absorção específico, buscou-se a maximização da potência térmica do evaporador e a minimização da potência elétrica auxiliar total requerida pelo sistema, variando-se parâmetros construtivos (comprimento, diâmetro e número de tubos) de cada trocador de calor. Os comprimentos, número e diâmetro dos tubos foram, então, fixados em função dos resultados obtidos nesta etapa do projeto. Definida a configuração final do sistema, calculou-se a capacidade de produção de gelo em barras pelo sistema de refrigeração por absorção proposto em função da demanda de energia elétrica ao longo do dia para a Região Norte Amazônica. Na quarta etapa do projeto, o absorvedor foi estudado isoladamente. O sistema de refrigeração por absorção proposto, que utiliza os gases de escape de um motor diesel de 123 kW de potência máxima de um grupo diesel-gerador de pequeno porte, possui uma capacidade de produção de 372 barras de gelo de 10 kg por dia, operando o dia inteiro, ou de 150 barras, considerando-se horário comercial (8h às 18h horas). / Abstract: This work shows the development of an ammonia-water absorption refrigeration system pre-existing simulation program, which uses diesel engine exhaust gases from a diesel-generator group as energy source. The project was implemented in four stages. An initial design of its components involved solely thermodynamic relations, and was based on the arbitration of temperature differences in the different heat exchangers and some environmental and operational conditions, such as cooling water inlet temperature in condensers and absorber and refrigeration capacity. The size of each refrigeration system equipment was obtained in terms of parameters such as overall heat transfer coefficients multiplied by the areas of each component or the effectiveness multiplied by the hourly minimum thermal capacity. In the second stage, the detailed construction of each component of the system was made with the aim of reaching as close to the original design parameters. The heat transfer equations for each system component, the heat transfer coefficient calculation, and the relevant pressure drops related to the calculation of required electric power were introduced. After the initial configuration had been defined of a specific absorption refrigeration system, an additional adjustment took place, aiming at the maximization of the thermal power of the evaporator and the minimization of the total electric power required by the system. This fine tunning was carried out by varying the construction parameters (length, diameter and number of tubes) of each heat exchanger. The length, number and diameter of the tubes were then set according to the results obtained in this part of the project. After settling the system configuration, the production capacity of ice bars of the proposed absorption refrigeration system was estimated according to the demand for electricity along the day for the northern Amazon region. In the fourth stage of the project, the absorber has been studied in separate, as a standalone module. The proposed absorption refrigeration system in this work, which uses the exhaust gases from a diesel engine of a small diesel-generator group, showed to have a production capacity of ice, measured in bars of 10 kg, equals to 372 bars a day (3720 kg), working all day, or 150 bars a day (1500 kg), if considering only the period of 8 working hours (business hours, from 8 am to 6 pm). / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

This master’s thesis analyses Kalina cycle, a power cycle where ammonia – water solution is used as a working fluid. The first part of this study introduces us to the Kalina cycle, presents its advantages and disadvantages, characteristics of the working fluid and its applications. Second section concerns with the method of cycle design and describes the calculation model made in this thesis. The calculation model is attached in a separate .XLSM file. The third part shows calculation of the cycle for given parameters, determination of cycle efficiency and main proportions of the thermal turbine. In the conclusion are the interpretations of the calculations results.

For ammonia-water absorption refrigeration technology it is suggested to use bubble type absorbers because the higher contact surface area provides a higher mass transfer rate. Furthermore, dispersion of bubbles in the bulk of liquid phase also exhibits better heat transfer characteristics that facilitate the recovery of dissipated heat of the exothermic absorption.In this context, plate heat exchangers are believed to be an option to be employed as absorber in some applications. Commercial plate heat exchangers have only one inlet and outlet for a working fluid and as a result, gas and liquid should be mixed before supplied to a gap between the two adjacent plates. The consequence is the high risk of bubble mergence to form a bigger bubble and to follow the shortest flow paths in vertical direction so that not all the heat transfer surface can be effectively used. Furthermore this feature makes plate heat exchangers sensitive to the angle of plate relative to the vertical which would be worst when it is laid to its side on a horizontal plane.Austrian Institute of Technology (AIT) develops an efficient Bubble Plate Absorber for applications in high-pressure absorption systems and this work tries to investigate design possibility of this Bubble Plate Absorber based on a plate heat exchanger equipped with microchannels between plates.Two sets of seven parallel microchannels same in shape and dimension were tested. The first set had a continuous wall which means fluids could flow independently along the microchannels; whereas, the other set was benefiting from some linkages between channels that fluids could cross from one microchannel to another one. Ammonia vapour was injected via one and two-holed distributors.It was found that microchannels with continuous wall deliver higher concentration and less unabsorbed bubbles at the microchannels outlet. In visual analysis by high-speed camera, changing the vapour distributors from single-hole to double-hole had no significant effect on the bubble distribution quality in lower flowrates; however, double-hole vapour distributor showed better performance in higher vapours flowrates.

Development of innovative thermodynamic cycles is important for the efficient utilization of low-temperature heat sources such as solar, geothermal, and waste heat sources. Binary mixtures exhibit variable boiling temperatures during the boiling process, which leads to a good thermal match between the heating fluid and working fluid for efficient heat source utilization. This study presents a theoretical and an experimental analysis of a combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia-water mixture as the working fluid and produces power and refrigeration, while power is the primary goal. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low to mid-temperature sources such as geothermal and solar energy. A thermodynamic analysis of power and cooling cogeneration was presented. The performance of the cycle for a range of boiler pressures, ammonia concentrations, and isentropic turbine efficiencies were studied to find out the sensitivities of net work, amount of cooling and effective efficiencies. The thermodynamic analysis covered a broad range of boiler temperatures, from 85 °C to 350 °C. The first law efficiencies of 25-31% are achievable with the boiler temperatures of 250-350 °C. The cycle can operate at an effective exergy efficiency of 60-68% with the boiler temperature range of 200-350 °C. An experimental study was conducted to verify the predicted trends and to test the performance of a scroll type expander. The experimental results of vapor production were verified by the expected trends to some degree, due to heat transfer losses in the separator vessel. The scroll expander isentropic efficiency was between 30-50%, the expander performed better when the vapor was superheated. The small scale of the experimental cycle affected the testing conditions and cycle outputs. This cycle can be designed and scaled from a kilowatt to megawatt systems. Utilization of low temperature sources and heat recovery is definitely an active step in improving the overall energy conversion efficiency and decreasing the capital cost of energy per unit.

Refrigerant management is crucial in the attempts to slow climate change. Emissions from the refrigeration sector are primarily due to poor management and unsafe destruction of refrigerants currently in circulation. Safe refrigerant management and improving system operating efficiency can result in a reduction of emissions. Ice rinks are some of the most energy-intensive public buildings, providing both heating and cooling. The major share of energy in an ice rink is the refrigeration system, which consumes about 43%. There are more than 360 ice rinks in Sweden as of 2018 and the most common type of refrigeration system is an indirect system. With the push for natural fluids, aqua ammonia is becoming a more appealing option as a secondary fluid in ice rinks because of its minimal negative impact on the environment and favorable thermophysical properties. The main drawbacks of the fluid are its toxic characteristics and material compatibility. However, since the first use in 2007, there has been an increase to 34 of the total ice rinks in Sweden that have aqua ammonia as a secondary fluid.  Thermophysical properties are used to calculate refrigeration design parameters, including secondary fluid concentration and pumping power required. The properties of aqua ammonia have not been experimentally tested within this century to the extent presented in this thesis. Existing data is either derived from measured values taken several decades ago or has been calculated. The novelty of this thesis project stems from the unique and more accurate results measured through laboratory work and from the ability to determine the impact of the newly measured values in ice rink refrigeration design. A total of 11 varying concentrations of aqua ammonia were tested for density, dynamic viscosity, specific heat capacity, thermal conductivity, and corrosion of 7 metal specimens. The solutions tested ranged from 2 wt-% to 30 wt-%, correlating to freezing points from -2C to -84C. The measurements for density resulted in values similar to reference values, ranging in a difference of only 0.3% to 1.7%. Dynamic viscosity results followed nearly the same trend as references with changing temperature and solution concentration, with values varying from 0.8% to 17% different than references. Specific heat capacity measurements proved significantly different than reference values. The trend is opposite of the reference, leading to drastically different values, especially at lower temperatures and higher solution concentrations. The difference in values ranges from 0.1% to 28%. Thermal conductivity results show similar trends, but higher values than expected. The difference between measured values and reference values range from 0.1% to 13%. Corrosion results show that copper and brass have the highest corrosion rates of 16.2 mm/yr and 1.84 mm/yr, respectively. The most compatible specimen was stainless steel, followed by carbon steel, with maximum corrosion rates of 0.041 mm/yr and 0.11 mm/yr, respectively. Brass connections commonly used in industry were also tested and resulted in corrosion rates ranging from 69.6 g/yr to 112 g/yr, which accounts for about 1% and 1.5% of the connections’ total weight lost per year. Compiling the laboratory measurements taken during the completion of this thesis project results in a more complete and accurate list of thermophysical properties for aqua ammonia that has never existed before.  These updated thermophysical properties for aqua ammonia, along with measured properties for other secondary fluids, were used to calculate operational parameters in a hypothetical ice rink refrigeration system. The results show that aqua ammonia is favorable with high COP and low pumping power, and therefore low pressure drop. Ammonia is most comparable to CaCl2 and K-formate for most results. The changes in calculated COP between old reference data and new measured data were less than a 1% decrease when plotting versus the temperature of the ice surface and with a set pump control (T) for cooling capacities of 200kW and 300kW. The change in heat transfer coefficients was more significant, with a range of about a 9% to 27% decrease in either the U-pipe under the rink floor or in a plate of the heat exchanger. Even though these heat transfer coefficient values are lower than previously calculated, the required pumping power is also lower using updated properties: 40% lower at a secondary fluid temperature of -10C. Even though the change in heat transfer coefficients is larger with experimental values, the impact on COP is minimal.  The takeaway from this project is that aqua ammonia is a favorable secondary fluid compared to calcium chloride and ethylene glycol, the two most commonly used secondary fluids in ice rink refrigeration. A system using aqua ammonia would have a 45% and 47% lower pumping power requirement compared to calcium chloride and ethylene glycol, respectively. The system would also have a 4.7% and 11.6% higher COP when compared to systems with calcium chloride and ethylene glycol, respectively. The significantly lower pumping power will lower total energy demand of the ice rink, thus decreasing operation costs. / Köldmediehantering är avgörande i försöken att sakta ner klimatförändringen. Utsläppen från kylsektorn beror främst på dålig hantering och osäker destruktion av köldmedier som för närvarande är i omlopp. Säkrare hantering av köldmedium och förbättrad systemdriftseffektivitet kan leda till ett minskat utsläpp. Ishallar är några av de mest energiintensiva offentliga byggnaderna som ger både uppvärmning och kylning. Den största andelen energi i en ishall är kylsystemet som förbrukar cirka 43%. Det finns mer än 360 isbanor i Sverige från och med 2018 och den vanligaste typen av kylsystem är ett indirekt system. Med trycket på naturliga vätskor blir ammoniakvatten ett mer tilltalande alternativ som en köldbärare i ishallar på grund av dess minimala negativa påverkan på miljön och gynnsamma termofysikaliska egenskaper. Köldbärares främsta nackdelar är dess toxiska karaktär och materialkompatibilitet. Sedan den första användningen 2007 har det dock skett en ökning till 34 av de totala ishallar i Sverige som har ammoniakvatten som köldbärare.  Termofysikaliska egenskaper används för att beräkna parametrar för kyldesign, inklusive köldbärares koncentration och pumpeffekten som krävs. Ammoniakvattens egenskaper har inte testats experimentellt under detta sekel i den utsträckning som presenteras i detta exjobb. Befintliga data härleds antingen från uppmätta värden som tagits för flera decennier sedan eller har beräknats. Nyheten härrör i detta exjobbsprojekt från de unika och mer exakta resultat som mätts genom laboratoriearbetet och från förmågan att bestämma effekten av de nyligen uppmätta värdena i kylskåpsdesign. Totalt 11 olika koncentrationer av ammoniakvatten testades med avseende på densitet, dynamisk viskositet, specifik värmekapacitet, värmeledningsförmåga och korrosion av 7 metallprover. De testade lösningarna varierade från 2 vikt-% till 30 vikt-%, korrelerade med fryspunkter från -2 ° C till -84 ° C. Mätningarna för densitet resulterade i värden som liknar referensvärdena, med en skillnad på endast 0,3% till 1,7%. Dynamiska viskositetsresultat följde nästan samma trend som referenser med förändrad temperatur och lösningskoncentration, med värden som varierade från 0,8% till 17% annorlunda än referenser. Specifika värmekapacitetsmätningar visade sig vara väsentligt annorlunda än referensvärden. Trenden är motsatt referensen, vilket leder till drastiskt olika värden, särskilt vid lägre temperaturer och högre koncentrationer. Skillnaden i värden varierar från 0,1% till 28%. Värmeledningsförmåga visar liknande trender, men högre värden än förväntat. Skillnaden mellan uppmätta värden och referensvärden sträcker sig från 0,1% till 13%. Korrosionsresultat visar att koppar och mässing har de högsta korrosionshastigheterna på 16,2 mm / år respektive 1,84 mm / år. Det mest kompatibla exemplet var rostfritt stål, följt av kolstål, med maximala korrosionshastigheter på 0,041 mm / år respektive 0,11 mm / år. Mässinganslutningar som vanligen används i industrin testades också och resulterade i korrosionshastigheter från 69,6 g / år till 112 g / år, vilket motsvarar för cirka 1% och 1,5% av anslutningarnas totala viktförlust per år. Att sammanställa laboratoriemätningarna som gjorts under slutförandet av detta projekt resulterar i en mer fullständig och noggrann lista över termofysikaliska egenskaper för ammoniakvatten som aldrig funnits tidigare.  Dessa uppdaterade termofysikaliska egenskaper för ammoniakvatten, tillsammans med uppmätta egenskaper för andra köldbärare, användes för att beräkna driftsparametrar i ett hypotetiskt kylsystem. Resultaten visar att ammoniakvatten är gynnsam med hög COP och en låg pumpeffekt och därmed ett lågt tryckfall. Ammoniakvatten är mest jämförbart med CaCl2 och K-formiat för de flesta resultat. Förändringarna i beräknad COP mellan gamla referensdata och nya uppmätta data var mindre än 1% minskning vid planering jämfört med isytans temperatur och med en inställd pumpkontroll (T ) för kylkapacitet på 200 kW och 300 kW. Förändringen i värmeövergångstal var mer signifikant, med ett intervall på cirka 9% till 27% minskning i antingen U-röret under golvet eller i en platta på värmeväxlaren. Även om dessa värmeövergångstal är lägre än tidigare beräknat, är den erforderliga pumpeffekten också lägre med hjälp av uppdaterade egenskaper: 40% lägre vid en köldbärarestemperatur på -10 ° C. Även om förändringen i värmeövergångstal är större med experimentella värden, är påverkan på COP minimal.  Slutsatser från detta projekt är att ammoniakvatten är en lämplig köldbärare jämfört med kalciumklorid och etylenglykol, de två vanligaste köldbärare i ishallskylning. Ett system som använder ammoniakvatten skulle ha ett pumpeffektbehov på 45% respektive 47% jämfört med kalciumklorid respektive etylenglykol. Systemet skulle också ha en 4,7% och 11,6% högre COP jämfört med system med kalciumklorid respektive etylenglykol. Den betydligt lägre pumpeffekten kommer att sänka det totala energibehovet för ishallar, vilket minskar driftskostnaderna.