Using ice slurry as secondary refrigerant for charge reduction in industrial facilities

This work analyses warming impact and electricity cost in farm milk cooling facilities when direct expansion systems are replaced by ice slurry based secondary refrigeration systems. The environmental improvement obtained has been assessed by comparing the TEWI values obtained using ice slurry with those obtained using a direct refrigeration facility. Economical effects have also been assessed by evaluating power consumption and taking into account the feasibility of benefiting from reduced electricity rate by producing and accumulating ice slurry during off-peak hours

Heat exchanger performance modeling using ice slurry as secondary refrigerant

Ice slurry is well known as a biphasic secondary refrigerant that presents several potential advantages compared to single phase secondary refrigerants. These potential advantages can be summarized in the ability to use the thermal storage and the high cooling capacity given by the latent heat. Theoretically, these features should allow important energy savings in secondary refrigerant distribution loop. However, an accurate evaluation of these energy savings requires the knowledge of the thermal and rheological performance of the refrigerant studied. Based on the experimental model developed by the authors for brine based ice slurry, a theoretical analysis of heat exchangers performance is presented in this work in order to calculate the potential energy savings associated to its use. The influence of ice concentration, mass flow rate, heat exchanger length and cooled fluid temperature over pumping power and heat transfer rate is studied. The ratio between heat transfer rate and pumping power is used as the evaluation parameter, which allows us to find the most favourable operation conditions for ice slurry flow. In order to assess the improvement obtained using ice slurry, results for ice slurry are compared to those obtained for carrier fluid at same inlet temperature.This research has been partially financed by the project DPI2007-66551-C02-01 grant from the “Dirección General de Industria, Mº de Ciencia y Tecnología”, the project 2I05SU0029 grant of the “Secretaría General de la Consejería de Educación y Cultura de la C.A. de la Región de Murcia” and the HRS Spiratube Company, Murcia (Spain)

Assessment of improvement in heat exchangers behaviour using ice slurry as secondary refrigerant

Ice slurIce slurry is well known as a biphasic secondary refrigerant that presents several potential advantages compared to single phase secondary refrigerants. These potential advantages can be summarized in the ability to use the thermal storage, and the high cooling capacity given by the latent heat. Theoretically, these features must allow important energy savings in secondary refrigerant distribution loop. An accurate evaluation of these energy savings requires knowledge of the thermal and rheological behaviour of the refrigerant studied. Based on the experimental model developed by the authors for brine-based ice slurry, a theoretical analysis of heat exchanger behaviour is presented in this work in order to find out the potential energy savings associated with its use. The influence of ice concentration, mass flow rate, heat exchanger length and pipe outer wall temperature over pumping power and heat transfer rate is studied. The ratio between heat transfer rate and pumping power is used as the evaluation parameter, which allows determination of the most favourable operation conditions for ice slurry flow. In order to asses the improvement obtained using ice slurry, results for ice slurry are compared to those obtained for a carrier fluid at the same inlet temperature. Finally, a practical example is proposed where the behaviour of a facility with several heat exchangers working in series is analysed for ice slurry and single phase flow.This research has been partially financed by the project DPI2007-66551-C02-01 grant from the “D.G.I., Mº de Ciencia y Tecnología”, the project 2I05SU0029 grant of the “S. G. de la Consejería de Educación y Cultura de la C.A. de la Región de Murcia” and the HRS Spiratube Company, Murcia (Spain)

Screening Ba0.9A0.1MnO3 and Ba0.9A0.1Mn0.7Cu0.3O3 (A = Mg, Ca, Sr, Ce, La) Sol-Gel Synthesised Perovskites as GPF Catalysts

Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) engine exhaust conditions. The samples have been obtained by the sol-gel method in an aqueous medium and deeply characterised. The characterization results indicate that the partial substitution of Ba by A metal in BaMnO3 (BM) and BaMn0.7Cu0.3O3 (BMC) perovskites: (i) favours the hexagonal structure of perovskite; (ii) improves the reducibility and the oxygen desorption during Temperature-Programmed Desorption (O2-TPD) tests and, consequently, the oxygen mobility; (iii) mantains the amount of oxygen vacancies and of Mn(IV) and Mn(III) oxidation states, being Mn(IV) the main one; and (iv) for Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) series, copper is partially incorporated into the structure. The soot conversion data reveal that Ba0.9La0.1Mn0.7Cu0.3O3 (BMC-La) is the most active catalyst in an inert (100% He) reaction atmosphere, as it presents the highest amount of copper on the surface, and that Ba0.9Ce0.1Mn0.7Cu0.3O3 (BM-Ce) is the best one if a low amount of O2 (1% O2 in He) is present, as it combines the highest emission of oxygen with the good redox properties of Ce(IV)/Ce(III) and Mn(IV)/Mn(III) pairs.This research was funded by the Spanish Government (MINCINN: PID2019-105542RB-I00/AEI/10.13039/501100011033 Project), the European Union (FEDER Funds), and Generalitat Valenciana (CIPROM/2021-070 Project). N. Ghezali thanks Argelian Government for her thesis grant and Á. Díaz-Verde of the University of Alicante for his predoctoral contract

Dimensional analysis and experimental study of pressure drop and heat transfer for Na-Cl ice slurry in pipes

Over the last few years, many works have been developed to study the influence of some factors like the mass flow, pipe diameter or ice contents on the pressure drop characteristics and heat transfer process when using ice slurry as liquid secondary refrigerant. Nevertheless, most of these works present results of great scientific interest, but hardly applicable to different situations to those of test conditions and therefore they have a limited interest when approaching the design of practical ice slurry installations. Based on the dimensional analysis, the work reported in this paper try to determine which are the variables that explain the thermal and hydraulic behaviour of ice slurry, to fix the influence of these variables and to present the results so that they can be used as a tool of design for ice slurry applications. Experimental studies were performed to clarify the thermal and hydraulic characteristics of ice slurry with a 3% sodium chloride-water solution flowing in circular pipes. A number of experiments have been carried out to investigate the characteristics of flowing ice slurry for various pipes diameter, ice mass fraction, flow velocity and ice crystal size, and the non-dimensional values have been obtained from the pressure drop (via Fanning factor) and the heat transfer (via Nusselt number). Experimental data on friction factor are plotted on a Moody diagram. Experimental values of Nusselt number are plotted also versus Reynolds number and others parameters. Both data collection has been compared with other researcher’s results, showing the most cases a good level of agreement

Improving the Catalytic Performance of BaMn0.7Cu0.3O3 Perovskite for CO Oxidation in Simulated Cars Exhaust Conditions by Partial Substitution of Ba

The sol–gel method, adapted to aqueous media, was used for the synthesis of BaMn0.7Cu0.3O3 (BMC) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A, A = Ce, La or Mg) perovskite-type mixed oxides. These samples were fully characterized by ICP-OES, XRD, XPS, H2-TPR, BET, and O2–TPD and, subsequently, they were evaluated as catalysts for CO oxidation under different conditions simulating that found in cars exhaust. The characterization results show that after the partial replacement of Ba by A metal in BMC perovskite: (i) a fraction of the polytype structure was converted to the hexagonal BaMnO3 perovskite structure, (ii) A metal used as dopant was incorporated into the lattice of the perovskite, (iii) oxygen vacancies existed on the surface of samples, and iv) Mn(IV) and Mn(III) coexisted on the surface and in the bulk, with Mn(IV) being the main oxidation state on the surface. In the three reactant atmospheres used, all samples catalysed the CO to CO2 oxidation reaction, showing better performances after the addition of A metal and for reactant mixtures with low CO/O2 ratios. BMC-Ce was the most active catalyst because it combined the highest reducibility and oxygen mobility, the presence of copper and of oxygen vacancies on the surface, the contribution of the Ce(IV)/Ce(III) redox pair, and a high proportion of surface and bulk Mn(IV). At 200 °C and in the 0.1% CO + 10% O2 reactant gas mixture, the CO conversion using BMC-Ce was very similar to the achieved with a 1% Pt/Al2O3 (Pt-Al) reference catalyst.This research was funded by the Spanish Government (MINCINN: PID2019-105542RB-I00/AEI/10.13039/501100011033 Project), the European Union (FEDER Funds), and Generalitat Valenciana (CIPROM/2021-070 Project). N. Ghezali thanks Argelian Government for her thesis grant and Á. Díaz-Verde thanks the University of Alicante for his predoctoral contract

Copper Catalysts Supported on Barium Deficient Perovskites for CO Oxidation Reaction

Mixed oxides with perovskite-type structure (ABO3) present interesting physico-chemical properties to be used as catalyst for atmospheric pollution control. In this work, a series of CuX/Ba0.7MnO3 catalysts (being x: 0, 4, 8 and 12 wt%) has been synthesized, characterized and tested for CO oxidation reaction. All the catalysts were active for CO oxidation in the two reactant mixtures tested: low CO mixture (0.1% CO and 1% O2 in He) and near stoichiometric mixture (1% CO and 1% O2 in He). Copper-free perovskite is the most active catalyst in the less demanding conditions (0.1% CO and 1% O2), as it presents the highest amount of oxygen vacancies working as active sites. However, at higher CO concentrations (1% CO in near stoichiometric mixture), copper-containing catalysts were more active than the perovskite support because, due to the saturation of the oxygen vacancies of perovskites, CuO seems to participate as active site for CO and O2 activation. Cu4/Ba0.7MnO3 and Cu12/Ba0.7MnO3 are more active than Cu8/Ba0.7MnO3 catalyst, since they present a larger amount of active sites on surface. These two copper-containing catalysts present a high stability and recyclability during the reaction at 300 °C in an ideal near stoichiometric mixture (1% CO and 1% O2).Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work was supported by Ministerio de Ciencia,Innovación y Universidades, (Grant No. PID2019-105542RB-I00), María José Illán Gómez, European Regional Development Fund, Generalitat Valenciana, (Grant No. CIPROM/2021-070 project), María José Illán Gómez, Universidad de Alicante

Exploring the effect of using carbon black in the sol-gel synthesis of BaMnO3 and BaMn0.7Cu0.3O3 perovskite catalysts for CO oxidation

BaMnO3 and copper-doped BaMnO3 perovskites seem to be a feasible alternative to current catalysts for the exhaust treatment. In this work, these formulations have been synthesized by a modified sol-gel method in which carbon black has been added to the conventional sol-gel process in order to improve the physical and chemical properties that modulate the catalytic performance. The samples have been deeply characterized by ICP-OES, XRD, XPS, H2-TPR and O2-TPD. The characterization results point out that the use of carbon black allows decreasing the calcination temperature which minimizes the sintering effects and improves the textural properties, the reducibility, and the oxygen mobility. The study of CO oxidation, using different simulated atmospheres, reveals that all the catalysts were active for CO to CO2 oxidation, but only when oxygen is supplied in excess, an effect of the synthesis method is observed. Additionally, as expected, the presence of copper (inserted or not into the perovskite lattice) benefits the catalytic performance. Otherwise, it seems that the catalytic performance for CO oxidation of BaMnO3-based samples is less affected by the fluctuations of CO and O2 concentrations than the platinum-based catalyst used as reference

Analyzing the role of copper in the soot oxidation performance of BaMnO3-perovskite-based catalyst obtained by modified sol-gel synthesis

A series of BaMn0.7Cu0.3O3 solids were prepared by a modified sol-gel method in which carbon black (VULCAN XC-72R), and different calcination temperatures (BMC3-CX, where X indicates the calcination temperature) have been used. The fresh and used catalysts were characterized by ICP-OES, XRD, XPS, FESEM, TEM, O2-TPD and H2-TPR. The presence of a carbon black during sol-gel synthesis of BMC3 mixed oxide allows diminishing the calcination temperature needed to achieve the perovskite structure, but it hinders the formation of the BaMnO3 polytype. The use of low calcination temperatures during synthesis reduces the sintering effects, and the mixed oxides present lower particle size, slightly higher BET surface areas and macropores with lower diameter than BMC3. The distribution of copper in BMC3-CX catalysts depends on the calcination temperature and copper insertion into the perovskite structure is promoted as the calcination temperature increases. All BMC3-CX catalysts are active for NO to NO2 and NOx-assisted soot oxidation processes, but only BMC3-C600 and BMC3-C700 show higher catalytic activity than BMC3 reference catalyst. BMC3-C600 presents the best performance as it features a high amount of surface copper and oxygen vacancies that increase during reaction. The comparison between the performance of the two best catalysts of the BM-CX series (BM-C700) and the BMC3-CX series (BMC3-C600) suggests that the unique advantage of using copper in the modified sol-gel synthesis is an additional decrease of 100 °C in the calcination temperature used for the synthesis of the best catalyst, which is 700 °C for BM-CX and 600 °C for BMC3-CX.This research was funded by Spanish Government (PID2019-105542RB-I00) and EU (FEDER Founding)

Modified BaMnO3-Based Catalysts for Gasoline Particle Filters (GPF): A Preliminary Study

Gasoline engines, mainly gasoline direct injection engines (GDI) require, in addition to three-way catalysts (TWC), a new catalytic system to remove the formed soot. Gasoline Particle Filters (GPF) are, among others, a possible solution. BaMnO3 and copper-doped BaMnO3 perovskites seem to be a feasible alternative to current catalysts for GPF. The physical and chemical properties of these two perovskites determining the catalytic performance have been modified using different synthesis routes: (i) sol-gel, (ii) modified sol-gel and iii) hydrothermal. The deep characterization allows concluding that: (i) all samples present a perovskite-like structure (hexagonal), except BMC3 which shows a polytype one (due to the distortion caused by copper insertion in the lattice), and ii) when a low calcination temperature is used during synthesis, the sintering effect decreases and the textural properties, the reducibility and the oxygen mobility are improved. The study of soot oxidation simulating the hardest GDI scenarios reveals that, as for diesel soot removal, the best catalytic performance involves the presence of oxygen vacancies to adsorb and activate oxygen and a labile Mn (IV)/Mn (III) redox pair to dissociate the adsorbed oxygen. The combination of both properties allows the transport of the dissociated oxygen towards the soot.This research was funded by Generalitat Valenciana (CIPROM/2021/70), Spanish Government (PID2019-105542RB-I00) and EU (FEDER Founding)