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The transition from fluorinated gases to natural refrigerants could be key to reducing the impacts of climate change. Ice rinks are energy-intensive buildings, with large heating and cooling demands. The pumping power required to move the secondary refrigerant typically accounts for a sizable amount of the energy use of the refrigeration system. The use of aqua ammonia as a secondary fluid shows promising results, with pumping power use of about half that required of ethylene glycol, environmental friendliness, and low corrosivity to steel components. Aqua ammonia is still novel but is currently in use in 34 Swedish ice rinks. This thesis addresses questions regarding evaporation rates, performance, material compatibility, safety, and regulations of aqua ammonia in ice rink systems. Laboratory tests were performed to assess aqua ammonia evaporation rates during storage and operations. Long-duration concentration change, in well-sealed and well-stored containers, indicated low levels of evaporation for all tested concentrations samples. Short-term concentration in open-air conditions, indicated rapid rates of evaporation, with nearly full evaporation of all ammonia concentration occurring within only 90 seconds of open-air exposure. Testing of sample-mixtures containing contamination by substances aqua ammonia was likely to encounter during retrofit replacement situations determined that aqua ammonia and calcium chloride produce flakey sedimentation. Additionally, lower concentrations of aqua ammonia are slightly more prone to becoming basic when mixed with the tested substances, such as calcium chloride. Historical data of systems operating with aqua ammonia were analyzed for energy performance. While pumping requirements typically account for 10-20% of the energy for refrigeration, the pumps of the rinks studied with aqua ammonia accounted for only 1.2 to 4.2%. However, data availability and system configuration anomalies suggest additional analyses are required. F, Övergången från fluorerade gaser till naturliga köldmedier kan vara nyckeln till att minska effekterna av klimatförändringen. Isbanor är energikrävande byggnader med stora värme- och kylbehov. Den pumpeffekt som krävs för att pumpa köldbärare står vanligtvis för en stor mängd energianvändning i kylsystemet. Användningen av ammoniakvatten som köldbärare visar lovande resultat, med användning av pumpeffekt på ungefär hälften som krävs av etylenglykol, miljövänlighet och låg korrosion för stålkomponenter. Ammoniakvatten är fortfarande ny men används för närvarande i 34 svenska isbanor. Detta exjobb behandlar frågor om avdunstningshastigheter, energiprestanda, materialkompatibilitet, säkerhet och föreskrifter för ammoniakvatten i isbanasystem. Laboratorietester utfördes för att bedöma avdunstningshastigheter för ammoniakvatten under lagring och drift. Långvarig koncentrationsförändring, i väl tillslutna och välförvarade behållare, indikerade låga nivåer av avdunstning för alla testade koncentrationsprover. En kortvarig koncentration under friluftsförhållanden indikerade snabba avdunstningshastigheter, med nästan full avdunstning av all ammoniak koncentration inom endast 90 sekunder efter exponering. Testning av olika ammoniakvatten lösningar som innehåller föroreningar skulle sannolikt påträffas vid byte av köldbärare. Dessutom är lägre koncentrationer av ammoniakvatten lite mer benägna att bli basiska när de blandas med de testade ämnena. Historiska data för system som arbetar med ammoniakvatten analyserades med avseende på energiprestanda. Medan pumpeffekten vanligtvis står för 10-20% av kylenergin, pumparna för de studerade isbanorna med ammoniakvatten behövde bara för 1,2 till 4,2% av kylenergi. Datatillgänglighet och systemkonfigurationsavvikelser föreslår dock att ytterligare analyser krävs. Dessutom analyserades bästa metoder för drift, underhållning och säkerhet och globala regleringsbegränsningar. Kartläggning av tillverkarens materialkompatibilitetsinformation

Reliable knowledge of phase change materials (PCM) thermo-physical properties is essential to model and design latent thermal energy storage (LTES) systems. This study aims to conduct a methodological measurement of thermo-physical properties, including latent enthalpy, isobaric specific heat, thermal conductivity and dynamic viscosity, of two n-alkanes, n-octadecane and n-eicosane. The enthalpy and isobaric specific heat of the materials are measured via differential scanning calorimetry (DSC) technique, using a pDSC evo7 from Setaram Instrumentation with a sample mass of 628.4 mg. The influence of the scanning rates, varying from 0.5 K/min to 0.025 K/min, in dynamic continuous mode within temperature range of 10-65 degrees C is investigated. The thermal conductivity and the dynamic viscosity are measured via Hot Disk TPS-2500S instrument and Brookfield rotational viscometer, respectively, up to 70 degrees C. The thermal analysis results via the pDSC show that the isothermal condition can be approached at a very low scanning rate, however at the cost of a higher noise level. A trade-off is observed for n-octadecane, achieving the lowest deviation of 0.7% in latent heat measurement at 0.05 K/min, as compared to the American Petroleum Table values. For n-eicosane, the lowest deviation of 1.2% is seen at the lowest scanning rate of 0.025 K/min. The thermal conductivity measured values show good agreements with a number of documented literature studies in the solid phase, within deviations of 2%. Larger deviations of 5-16% are found for the measurement in the liquid phase. The viscosity values also show a good agreement with the literature values with maximum deviations of 2.9% and 6.3%, with respect to the values of American Petroleum Tables, for n-octadecane and n-eicosane, respectively. The good agreements achieved in measurements establish the reliable thermo-physical properties contributing to the future simulations and designs., QC 20201126

Three-dimensional (3D) printing, known as additive manufacturing, provides new opportunities for the design and fabrication of highly efficient industrial components. Given the widespread use of this technique by industries, 3D printing is no longer limited to building prototypes. Instead, small-to-medium scale production units focus on reducing the cost associated with each part. Among the various industrial components that can be developed with this manufacturing technology are heat transfer components such as heat exchangers. To this end, this study investigated the heat transfer characteristics of minichannel-based heat exchangers embedded with longitudinal vortex generators, both experimentally and numerically. Three enhanced prototypes with different vortex generator design parameters and a smooth channel as a reference case were printed with an aluminum alloy (AlSi10Mg) using direct metal laser sintering (DMLS). The rectangular minichannel had a hydraulic diameter of 2.86 mm. Distilled water was used as the test fluid, and the Reynolds number varied from 170 to 1380 (i.e., laminar flow). Prototypes were tested under two different constant heat fluxes of 15 kW m(-2) and 30 k m(-2). The experimental results were verified with a commercial simulation tool, Comsol Multiphysics (R), using the 3D conjugate heat transfer model. In the case of the smooth channel, the experimental results were also compared with well-known correlations in the field. The results showed that 95% and 79% of the experimental data were within 10% of the numerical simulation results and the values from the existing correlations, respectively. For the channel enhanced with the vortex generators, the numerical predictions agreed well with the experimental results. It was determined that the vortex generators can enhance the convective heat transfer up to three times with the designed parameter. The findings from this research underline the potential of additive manufacturing in the developmen, QC 20201126

Potassium formate and potassium acetate, as well as their blends are known as environmentally friendly secondary fluids with good thermophysical properties. The aim of this work was to investigate properties of cesium formate, cesium acetate and ammonium acetate solutions. Results showed that various alkali metal ions such as potassium, sodium, cesium or ammonium are affecting the freezing point, thermal conductivity, viscosity and specific heat capacity in different ways. Among examined salts, ammonium formate showed the best performance by giving the highest specific heat capacity and highest thermal conductivity and the lowest dynamic viscosity compared to potassium formate and other salts. Cesium formate solutions had the lowest viscosity among all tested salts. This study shows that both cesium formate and sodium formate could be used as different additives to enhance different properties of potassium formate and potassium acetate secondary based fluids., QC 20200611

This work presents and discusses a detailed thermal conductivity assessment of erythritol, xylitol, and their blends: 25 mol% erythritol and 80 mol% erythritol using the transient plane source (TPS) method with a Hot Disk Thermal Constants Analyzer TPS‐2500S. Thereby, the thermal conductivities of xylitol, 25 mol% erythritol, 80 mol% erythritol, and erythritol were here found for respectively in the solid state to be 0.373, 0.394, 0.535, and 0.589 W m−1 K−1 and in the liquid state to be 0.433, 0.402, 0.363, and 0.321 W m−1 K−1. These obtained results are comprehensively and critically analyzed as compared to available literature data on the same materials, in the phase change materials (PCMs) design context. This study clearly indicates that these thermal conductivity data in literature have considerable discrepancies between the literature sources and as compared to the data obtained in the present investigation. Primary reasons for these disparities are identified here as the lack of sufficiently transparent and repeatable data and procedure reporting, and relevant standards in this context. To exemplify the significance of such transparent and repeatable data reporting in thermal conductivity evaluations in the PCM design context, here focused on the TPS method, a comprehensive measurement validation is discussed along various residual plots obtained for varying input parameters (ie, the heating power and time). Clearly, the variations in the input parameters give rise to various thermal conductivity results, where choosing the most coherent result requires a sequence of efforts per material, because there are no universally valid conditions. Transparent and repeatable data and procedure reporting are the key to achieve comparable thermal conductivity results, which are essential for the correct design of thermal energy storage systems using PCMs., QC 20190228, Energimyndigheten project 34948‐1

This study investigates the thermal performance of laminar single-phase flow in an additively manufactured minichannel heat exchanger both experimentally and numerically. Distilled water was employed as the working fluid, and the minichannel heat exchanger was made from aluminum alloy (AlSi 1 0Mg) through direct metal laser sintering (DMLS). The minichannel was designed with a hydraulic diameter of 2.86 mm. The Reynolds number ranged from 175 to 1360, and the heat exchanger was tested under two different heat fluxes of 1.5 kWm(-2) and 3 kWm(-2). A detailed experiment was conducted to obtain the thermal properties of AlSi10Mg. Furthermore, the heat transfer characteristics of the minichannel heat exchanger was analyzed numerically by solving a three-dimensional conjugate heat transfer using the COMSOL Multiphysics to verify the experimental results. The experimental results were also compared to widely accepted correlations in literature. It is found that 95% and 79% of the experimental data are within 10% range of both the simulation results and the values from the existing correlations, respectively. Hence, the good agreement found between the experimental and simulation results highlights the possibility of the DMLS technique as a promising method for manufacturing future multiport minichannel heat exchangers., QC 20210914

This work presents and discusses a detailed thermal conductivity assessment of erythritol, xylitol and their blends: 25 mol% erythritol and 80 mol% erythritol using the Transient Plane Source (TPS) method with a Hot Disk Thermal Constants Analyzer TPS-2500S. Their thermal conductivities were here found to be respectively: 0.59; 0.37; 0.39 and 0.54 W/(m·K) in the solid state, and to be 0.32; 0.43; 0.40 and 0.36 W/(m·K) in the liquid state. These obtained results are comprehensively and critically analyzed as compared to available literature data on the same materials, in the phase change materials (PCMs) design context. This study clearly indicates that the literature has considerable discrepancies among their presented thermal conductivities, and also as compared to the values found through the present investigation. Primary reason for these disparities are identified here as the lack of sufficiently transparent and repeatable data and procedure reporting, and relevant standards in this context. To exemplify the significance of such transparent and repeatable data reporting in thermal conductivity evaluations in the PCM design context, here focused on the TPS method, a comprehensive measurement validation is discussed along various residual plots obtained for varying input parameters (i.e., the heating power and time). Clearly, the variations in the input parameters give rise to various thermal conductivity results, where choosing the most coherent result requires a sequence of efforts per material, but there are no universally valid conditions. Transparent and repeatable data and procedure reporting is the key to achieve comparable thermal conductivity results, which are essential for the correct design of thermal energy storage systems using PCMs., QC 20180813

The most common secondary fluid used for the borehole heat exchangers in Sweden is aqueous solution of ethyl alcohol (EA). Commercially available ethyl alcohol based fluids in Sweden and other European countries contain various denaturing agents. Ethyl alcohol based secondary fluids in Sweden are distributed as ethyl alcohol concentrate, including up to 12 wt-% denaturing agents in form of propyl alcohol (PA) and n-butyl alcohol (BA). In other European countries, like Switzerland and Finland, the commercial products containing a mixture of methyl ethyl ketone and methyl isobutyl ketone (up to 4.5 vol-%) are used for GSHP application. The chemical character of these denaturing agents can in different ways affect the thermophysical properties. Therefore, the aim of this paper was to investigate the performance of commercially available alcohol blends in Europe in terms of pressure drop and heat transfer in the BHE. The results show that the most commonly used product in Sweden (EA18+PA1.6+BA0.4) presents the best characteristics in terms of higher heat transfer (up to 10 %) and lower pressure drop (up to 2.7 %) among different commercial products found in Europe. Another commercial product used in Switzerland showed second best performance in terms of higher heat transfer (up to 5 %) and lower pressure drop (up to 2 %). Moreover, other products containing higher concentrations of denaturing agents presented the worst performance in terms of lower heat transfer (up to 8 %) and higher pressure drop (up to 1 %) than EA20., QC 20171024

Ethylene and propylene glycol water based secondary solutions are very popular due to their low corrosivity character, low freezing point, high boiling point and low fire hazards. The main drawback of ethylene glycol solutions is its potential toxicity both to the environment, animals and food products. Therefore, propylene glycol is the most common substitute for ethylene glycol. The biggest disadvantage of propylene glycol solutions is its very high viscosity at low temperatures, which results in higher pumping power and lower system performance. For very low temperatures, it is common to use non-aqueous synthetic fluids, which have lower viscosities at these temperatures. Thus, the aim of this paper is to propose a new generation of synthetic iso-paraffins having better thermophysical properties compared to existing synthetic products used for very low temperature applications. The first results showed that the new generation of iso-paraffins having the freezing temperature of 50 degrees C or lower had significantly lower viscosity (between 75 % and 98 %) at very low temperatures compared to 60 wt-% propylene glycol (PG 60 %) and 60 wt-% ethylene glycol solution (EG 60 %). Iso-paraffin 1 showed better performance than iso-paraffin 2 by giving the lowest freezing point, the lowest dynamic viscosity and kinematic viscosity as well as the highest thermal conductivity. Instead, iso-paraffin 2 had higher specific heat capacity. As seen, the different composition of iso-paraffin mixture can result in different properties and operating temperature ranges. Thus, iso-paraffins could become an interesting alternative for very low temperature cooling applications., QC 20211019

Potassium organic salts like formates and acetates are known as environmentally friendly secondary fluids. The most important advantages of salts compared to aqueous solutions of alcohols and glycols are good thermophysical properties, low toxicity and non-flammability. The purpose of this work is to investigate properties of different formate salt based secondary fluids like: lithium formate, ammonium formate and sodium formate at low temperatures in order to propose new blends of formate salts that could be used as secondary fluids for low temperature applications. Studies showed that different alkali metal ions like sodium, lithium or ammonium are affecting the solubility level, freezing point, thermal conductivity, dynamic viscosity and specific heat capacity in different way. Among examined formate salts, ammonium formate showed the best performance by giving the lowest freezing point as well as the highest specific heat capacity and highest thermal conductivity and similar dynamic viscosity. Lithium formate salts had the highest dynamic viscosity among all samples and despite high specific heat capacity and thermal conductivity values these salts cannot be recommended for low temperature applications. 30 wt-% sodium formate and 36 wt-% lithium formate were recrystallizing at lower temperatures than 0 degrees C when fast cooling rate was applied. Thus, the possible application for these salts is rather limited to higher temperatures only. As seen, different type of cation group in the formate salt can result in different properties, thus, further studies to investigate ammonium formate as well as different acetate salts are recommended., Part of proceedings: ISBN 978-2-36215-020-3QC 20211019

Seawater is the most common fluid on earth and ice generating machines are increasingly used on fishing vessels to produce ice slurry from the seawater with up to 60 % ice to be poured over the catch. In this study, new measurements of thermophysical properties of standard seawater have been carried out to complement a recent literature search made to establish thermophysical property data of seawater as function of salinity and temperature. These single-phase measurements have been made for salinity 20, 30 and 35 g kg(-1) (2.0, 3.0 and 3.5 % total salt content) and include measurements of freezing point, density, dynamic viscosity, thermal conductivity, specific heat capacity and specific enthalpy. The obtained experimental results generally confirm recent literature search and experimental results only call for minor adjustments of viscosity values. Hence, experimental results confirm the following published ice slurry properties: enthalpy, ice fraction and ice slurry density., QC 20160816

The most common secondary fluid used for the borehole heat exchangers in Sweden is an aqueous solution of ethyl alcohol (EA) due to its relatively good thermophysical properties and low toxicity. Commercially available ethyl alcohol based fluids in Sweden contain up to 10 wt-% denaturing agents in form of propyl alcohol (PA) and n-butyl alcohol (BA). The aim of this paper was to investigate the performance of the existing ethyl alcohol blend containing two denaturing agents and alternative alcohol blends in terms of the pressure drop and heat transfer in the BHE and comparison with ethyl alcohol based secondary fluid. Experimental results showed that the presence of these denaturing agents improves thermophysical properties such as specific heat capacity, thermal conductivity and dynamic viscosity when added in small concentration. EA18 + PA1.6 + BA0.4 and EA18.4 + PA1.6 present the best characteristics in terms of the heat transfer and pressure drop. Both blends are giving higher heat transfer coefficient by 9.4 % (EA18 + PA1.6 + BA0.4) and 8.11 % (EA18.4 + PA1.6) than pure EA20. Both blends are giving as well lower pressure drop than EA20 by up to 2.7 % (EA18 + PA1.6 + BA0.4) and 3 % (EA18.4 + PA1.6). EA18 + PA1.6 + BA0.4 gives 1.4 % higher heat transfer coefficient and EA18.4 + PA1.6 gives lower pressure drop by up to 0.4 % when these two blends are compared., Conference code: 126956; Export Date: 22 May 2017; Conference Paper; Funding details: Energimyndigheten; Funding text: The Swedish Energy Agency, Effsys Expand project and all industrial partners are greatly acknowledged for financing this project. QC 20170531

Ice generating machines are more and more used on fishing vessels to produce ice slurry from seawater. Because slurry with up to 60% ice can be handled and poured over the catch, there is excellent potential for long preservation of the catch on board and during transport, improving seafood quality for the end user. A literature search has been made to establish physical property data of seawater as a function of salinity and temperature. Ice slurry properties of seawater have been generated and are presented by means of an enthalpy phase diagram and related diagrams giving ice concentration, enthalpy change, density and viscosity of fine crystalline ice slurry. These studies also confirm that an initial salt content of 2-3% will give optimal performance. Seawater is known to be corrosive and a brief discussion of corrosion factors and problems, use of corrosion inhibitors and choice of materials is included in the paper., QC 20200910

Seawater is the most common fluid on earth and ice generating machines are increasingly used on fishing vessels to produce ice slurry from seawater with up to 60% ice to be poured over the catch. In this study, a literature search has been made to establish physical property data of seawater as function of salinity and temperature. Ice slurry properties of seawater have been generated and are presented by means of an enthalpy-phase diagram and related tables with ice concentration, enthalpy change and density. This material confirms that an initial salt content of 2-3 % is optimal and it can help determine the potential for long preservation of catch on board and during transport, improving seafood quality. As seawater is known to be corrosive, a brief discussion on corrosion factors and problems, the use of corrosion inhibitors and choice of materials is included in this paper., QC 20150526

Methyl and ethyl alcohol based secondary fluids are commonly used in different indirect refrigeration systems due to relatively good thermophysical properties. Methyl alcohol is considered toxic and not permitted for use as secondary fluid in most of Europe. Ethyl alcohol based secondary fluids are commonly used in Sweden due to their low toxicity and good properties. Commercially available ethyl alcohol based fluids contain up to 10 wt-% denaturing agents in form of propyl alcohol (2-propanol, isopropanol) and nbutyl alcohol (n-butanol). Results show that presence of propyl alcohol in the ethyl alcohol based secondary fluid improves its thermophysical properties such as specific heat capacity, thermal conductivity and dynamic viscosity when added in small concentration. The aim of this paper is to investigate the thermophysical properties of various ethyl and isopropyl alcohol blends in order to find the most optimal blend as well as to evaluate if this blend could become a competitive alternative secondary fluid., QC 20170628

Seawater is the most common fluid on earth and ice generating machines are increasingly used on fishing vessels to produce ice slurry from seawater with up to 60% ice to be poured over the catch. An experiment using this method has recently shown that sensitive fish immersed in ice slurry, when flown from Japan to Taiwan, arrived in better condition than fish chilled by ordinary procedure. In this study, a literature search has been made to establish physical property data of seawater as function of salinity and temperature. Ice slurry properties of seawater have been generated and are presented by means of an enthalpy-phase diagram and related tables with ice concentration, enthalpy change and density. This material confirms that an initial salt content of 2-3 % is optimal and it can help determine the potential for long preservation of catch on board and during transport. As seawater is known to be corrosive, a brief discussion on corrosion factors and problems, the use of corrosion inhibitors and choice of machine and transport materials is included in this paper., QC 20150807

Ethyl alcohol (ethanol) based secondary fluids are commonly used in different types of indirect refrigeration systems in Scandinavia due to low toxicity, relatively good thermophysical properties and environmental regulations regarding leakage. Ethyl alcohol based commercial products available in Scandinavia contain different types of denaturing agents but no corrosion inhibitors. The most common denaturing agents are isopropyl alcohol (isopropanol), n-butyl alcohol (n-butanol), methyl ethyl ketone and methyl isobutyl ketone. Property measurements recently performed at KTH showed that presence of these additives in ethyl alcohol based secondary fluid improved thermophysical properties especially in terms of specific heat, thermal conductivity, and dynamic viscosity. Additionally, it was found that the specific heat capacity tendency is different than previously reported., QC 20150807

Secondary refrigerants are aqueous solutions of organic or inorganic salts used in indirect refrigeration systems to transfer heat. Water is known for its corrosive character and secondary refrigerants based on aqueous solutions have the same tendency. The most important corrosion factors are: type of secondary refrigerant, fluid velocity, pH, concentration, temperature, dissolved oxygen and scaling behaviour. Nevertheless, it is possible to minimize corrosion problems. There are several aspects which need to be taken into the consideration while working with the secondary refrigerants e.g. design of system, selection of secondary refrigerant, corrosion inhibitors and compatible materials used in the installation. The methods of system cleaning, refrigerant charging and deaeration procedures are also extremely important. The purpose of this paper is to present corrosion problems and provide a list important aspects related to designing, preparing and maintaining of indirect systems. Moreover, it introduces the traditional and alternative methods of corrosion protection of indirect systems with secondary refrigerants., QC 20120425, Influence of adsorption corrosion inhibitors and other additives on heat transfer and thermophysical

Experimental and Numerical Investigation of a Latent Heat Thermal Energy Storage Unit with Ellipsoidal Macro-encapsulationTianhao Xu, Emma Nyholm Humire, Silvia Trevisan, Monika Ignatowicz, Samer Sawalha, Justin NW Chiu*Department of Energy Technology, KTH Royal Institute of Technology, 100 44, Stockholm, SwedenAbstractIn this paper, a novel type of macro-encapsulated phase change material (PCM)shaped in ellipsoidis investigated on a component scale.The encapsulated PCM is a paraffin-based commercial material (ATP60); differential scanning calorimetry and transient plane source method are used to measure the thermo-physical properties of the PCM. A numerical model and a 0.382 m3latent heat thermal energy storage (LHTES) prototype have been built and experimentally characterized. The temperature measurements indicate that thermocline is retainedin the packed bed region. The charge/discharge can be accelerated by65% with20 K increase intemperature difference between the phase-change temperature and heat transfer fluid (HTF)inlet temperature. Increasing HTF inlet flowrate from 0.15 m3/h (Re=77) to 0.5 m3/h (Re=256) shortenscompletion time of charge by51%. Furthermore, a one-dimensional packed bed using source based enthalpy method was constructed and validatedwithin6.6% errorfor aReynolds numberof 90 to 922. Compared with a conventional cylindrical PCM capsule, the ellipsoidal encapsulation shows60% increase in discharge speed but 23%lower storage capacity. This work demonstrates a combined experimental and numerical characterization approach for a novel ellipsoidal PCM encapsulationgeometry., The manuscript has been submitted to the journal of Energy. On the date when this manuscript is uploaded in Diva (2021-04-30), the manuscript is still under reviewing process.QC 20210506