Numerical and experimental study of atrium enclosure fires in a full scale fire test facility. Póster

For the present work, a 3-D numerical model has been implemented to simulate the thermal and fluid fields induced by an enclosure fire in an atrium and for smoke exhaust system assessment. This study is focused on the ‘Fire Atrium’, a new full-scale fire test facility of the Technological Metal Centre in Murcia, Spain. It is an aluminium prismatic squared base building of 19.5 m x 19.5 m x 20 m with several vents arranged in its walls and four exhaust fans at the roof

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)

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

Gestación y nacimiento de la Universidad Politécnica de Cartagena. Una perspectiva personal

La transformación de los estudios universitarios en Cartagena ha sido obra de “cientos de personas del personal docente, investigador, de administración y servicios que han sabido aprovechar los medios a su disposición y superar las dificultades para impulsar la docencia de calidad, la investigación de nivel y la transferencia útil a las empresas”, Antonio Viedma Robles durante la lección magistral con la que la UPCT ha rememorado el veinte aniversario de su fundación durante el acto académico de Santo Tomás de Aquino. El catedrático de Mecánica de fluidos e ingeniería térmica, que fue vicepresidente y vicerrector de la UPCT durante sus primeros años, ha querido rendir homenaje a sus compañeros “por la universidad que hemos construido entre todos en estos veinte años y que seguro seguiremos mejorando”

In-pipe axial pico-hydraulic tailored turbine design: a novel approach using a dimensionless design chart

Energy consumed by the water industry is not negligible and improvements on energy efficiency in water distribution networks are still needed. This work aims to provide a new approach to design tailored torpedo shaped in-pipe axial pico-hydraulic turbines for the recovery of energy in water distribution networks. Simple straight untwisted blades with arc of circles profiles are imposed to simplify manufacturing. Ideal flow bi-dimensional cascade theory with Weinel isolated airfoil to cascade correlations are used as compromise between accuracy and simplicity. From it, a dimensionless design chart is build. A novel flow-to-head factor is chosen as main dimensionless factor to simplify stator analysis and obtain a more compact chart. From five usual input design parameters, choosing the value of three, and letting two of them to vary allows the trace of a space of all optimal designs. From this space, a turbine or family of turbines can be obtained. A design example on the same conditions as a experimentally tested turbine found in the literature was carried over and simulated with OpenFOAM open source library. A mesh parametric study for numerical validation purposes is realized. Discretization uncertainty found for the selected mesh was about one point for the hydraulic efficiency. The designed and simulated turbine showed a maximum hydraulic efficiency of . The presented non-dimensional approach proved to be useful to design efficient tailored simple pico-hydraulic turbines for energy recovery in distribution water networks, relaying on one design chart.This work have been supported by Fundación Séneca (Murcia, Spain)[Grant No. 20352/FPI/17]

Generalized Reynolds number and viscosity definitions for non-Newtonian fluid flow in ducts of non-uniform cross-section.

This work presents and experimental study of the generalization method of the Reynolds number and the viscosity of pseudoplastic fluid flow in ducts of non-uniform cross-section. This method will permit to reduce 1 degree of freedom of hydrodynamical and thermal problems in those ducts. A review of the state of the art has been undertaken and the generalization equation proposed for ducts of uniform cross section has been used as a starting point. The results obtained with this equation have not been found satisfactory and a new one has been proposed. Specifically, the procedure has been developed for two models of scraped surface heat exchanger with reciprocating scrapers. For both models, the scraper consists of a concentric rod inserted in each tube of the heat ex- changer, mounting an array of plugs that fit the inner tube wall. The two models studied differ in the design of the plug. The procedure to perform the generalization method out of experimental data is accurately detailed in the present document.The first author thanks Mr. Martínez and Dr. Solano for their invaluable contribution to the project and their advise. He also thanks the Spanish Government, Ministry of Education for the FPU scholarship referenced as AP2007-03429 which covered the expenses of a 4-year research at Universidad Politécnica de Cartagena

Effects of the aeration on the fluid dynamic behaviour of a multi-zone activated sludge system

Conventional wastewater treatment plants (WWTP) are necessary to modify the wastewater properties in order to make it acceptable for a safe discharge into the environment or a certain reuse purpose. Biological oxidation is the most important of the processes involved in conventional WWTP. Organic substances dissolved in the water are removed by means of bacteria presented in the biological reactor. Air is necessary to enable the reduction of the organic content of the water by the bacteria. Bubbles of air are introduced into the reactor through air diffusers. Air diffusers can account up to 70% of WWTP total energy consumption. So a deep understanding of the dynamic behaviour of the flow is necessary for optimizing the process and saving energy. A numerical analysis of the effects of the aeration in the fluid dynamics behaviour of a real multi-zone activated sludge reactor is carried out. The purpose is to identify and analyse the changes originated in the velocity field by the aeration. A numerical modelling of the activated sludge system located in San Pedro del Pinatar (Murcia, Spain) is developed throughout a general-purpose computational fluid dynamics (CFD) code. The multiphase flow is simulated with a Euler–Lagrange approach; modelling the bubbles as discrete phase. Two simulations, one with aeration and the other without it, are carried out. The numerical results show that the aeration has a notable effect in the performance of the reactor. Changes in velocity field, stagnant zones, residence time distribution or even free surface level originated by the aeration in the reactor are studied. In general, the aeration reduced the amount of stagnant volume in the reactor. However, when the aeration is activated, some re-circulating zones are formed, reducing the residence time in the reactor.The researcher team of the present work acknowledges the contribution of the company ESAMUR, owner of the biological reactor studied, which provided the experimental data necessary for the development of the numerical model presented

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

Influence of different make-up air configurations on the fire-induced conditions in an atrium

This paper provides with a set of full-scale experimental data of atrium fires. These data could be used as benchmarks for future numerical validation studies. In particular, the influence of the make-up air velocity as well as the position and area of the vents in an atrium is assessed both experimentally and numerically. Experimentally, the effect of different make-up air supply positions and inlet area on the fire-induced inner conditions and smoke layer descent was studied by means of three full-scale fire tests conducted in a 20 m cubic atrium. Detailed transient measurements of gas and wall temperatures, as well as pressure drop through the exhaust fans and airflow at the inlets were recorded. Later computational fluid dynamics (CFD) simulations of these tests were performed with the code Fire Dynamics Simulator (FDS). Experimentally, the lack of symmetry in make-up air vents and the large inlet area turn the flame and plume into more sensitive to outer effects. However, no significant difference has been observed between the make-up air topologies assessed. Even make-up velocities higher than 1 m/s, with symmetric venting topology, have not induced important flame or plume perturbations. Numerically, the simulations agree well with the experiments for the cases with make-up air velocities lower than 1 m/s. Poor agreement has been found for the case with inlet velocities higher than 1 m/s