Transient thermal model of a vehicle's cabin validated under variable ambient conditions

[EN] This paper presents a lumped-parameter thermal model of the passengers' compartment of a vehicle. The model is completely dynamic and has been thoroughly validated under variable ambient conditions including solar radiation. The proposed model reproduces accurately the warm-up and cool-down of the cabin and can help analyse capacity reduction actions for air-conditioning systems. In this study, the thermal loads have been calculated by means of the model. For the tested minibus in real outdoor conditions, air renewal represents from 7% up to 53% of the thermal load, while the solar radiation accounts for 18% 31%. According to the results, a decrease of 0.2 in the glazing transmissivity can lead to a 3.3% reduction of the installed cooling capacity.This work has been supported by the European Commission under the 7th European Community framework program as part of the ICE project "MagnetoCaloric Refrigeration for Efficient Electric Air-Conditioning", Grant Agreement no. 265434. B. Torregrosa-Jaime acknowledges the Spanish Education, Culture and Sport Ministry (Ministerio de Educacion, Cultura y Deporte) for receiving the Research Fellowship FPU ref. AP2010-2160.Torregrosa Jaime, B.; Bjurling, F.; Corberán Salvador, JM.; Di Sciullo, F.; Payá Herrero, J. (2015). Transient thermal model of a vehicle's cabin validated under variable ambient conditions. Applied Thermal Engineering. 75:45-53. https://doi.org/10.1016/j.applthermaleng.2014.05.074S45537

Experimental investigations on the influence of ice floating in an internal melt ice-on-coil tank

In this paper, the discharge of an experimental ice-storage tank is analyzed. The storage tank is an internal melt-ice-on-coil system. The discharge process has been studied for different mass flow rates and supply temperatures in the range from 10 ºC to 15 ºC. The results indicate that once the ice breaks and floats toward the top of the tank, convection in the ice/water mixture is enhanced and the heat transfer fluid in the top coils becomes colder than in the bottom coils. Thus, an increase of the cooling power is generally observed around the ice-breaking point. Two correlations have been developed to reproduce the effect of the mass flow rate and supply temperature on the discharge duration and the mean cooling power.The authors gratefully acknowledge ACCIONA Infraestructuras for the financing support and collaboration.López Navarro, A.; Biosca Taronger, J.; Torregrosa Jaime, B.; Corberán Salvador, JM.; Bote García, J.; Payá Herrero, J. (2013). Experimental investigations on the influence of ice floating in an internal melt ice-on-coil tank. Energy and Buildings. 57:20-25. doi:10.1016/j.enbuild.2012.10.040S20255

An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators

A one-dimensional model of a parallel-plate active magnetic regenerator (AMR) is presented in this work. The model is based on an efficient numerical scheme which has been developed after analysing the heat transfer mechanisms in the regenerator bed. The new finite difference scheme optimally combines explicit and implicit techniques in order to solve the one-dimensional conjugate heat transfer problem in an accurate and fast manner while ensuring energy conservation. The present model has been thoroughly validated against passive regenerator cases with an analytical solution. Compared to the fully implicit scheme, the proposed scheme achieves more accurate results, prevents numerical errors and requires less computational effort. In AMR simulations the new scheme can reduce the computational time by 89%.B. Torregrosa-Jaime acknowledges the Spanish Ministry of Education, Culture and Sport (Ministerio de Educacion, Cultura y Deporte) for receiving the Research Fellowship FPU ref. AP2010-2160.Torregrosa Jaime, B.; Corberán Salvador, JM.; Payá Herrero, J.; Engelbrecht, K. (2015). An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators. International Journal of Refrigeration. 58:121-130. https://doi.org/10.1016/j.ijrefrig.2015.06.007S1211305

Modelado y análisis de una instalación con almacenamiento latente de energía térmica de 345 KWH

Proyecto ConfidencialTorregrosa Jaime, B. (2010). Modelado y análisis de una instalación con almacenamiento latente de energía térmica de 345 KWH. http://hdl.handle.net/10251/31451.Archivo delegad

Modelling and analysis of an air-conditioning system for vehicles based on magnetocaloric refrigeration

[EN] This PhD thesis studies the application of the magnetic refrigeration technology in the air-conditioning system of automobiles. Thermal models of each of the components of such a system have been developed with the purpose of determining accurately its global performance. A dynamic one-dimensional model of a parallel-plate active magnetic regenerator (AMR) has been developed. The model is based in a new numerical scheme that reduces the computation time by 88% compared to the most commonly employed method. The model reproduces very accurately the passive regenerator cases with analytic solution and has been thoroughly validated against experimental results of both passive regenerator and AMR tests. The inclusion in the model of the magnetocaloric properties experimentally measured with a sample of the employed material, the demagnetizing effect, the fluid flow maldistribution and the losses to the ambient in the experimental setup have all been keys to obtain a good agreement with the experiments. The influence of the uncertainties and simplifications assumed when modelling these physical phenomena has been analyzed in detail, which has allowed the validation of different approaches. Besides, a dynamic model of the air-conditioning (AC) system of an electric vehicle has been developed. Thermal models of each of the system components have been included, namely the cabin, the hydraulic loops with the air-to-coolant heat exchangers and the electric auxiliaries. The modelling methodology employed is based on the combination of the conservation equations with the semi-empirical fitting of the global heat transfer coefficient. Excellent validation results have been obtained with experimental results in a wide range of operating conditions. The vehicle model has been employed to obtain the cooling and heating demand of a commercial full electric minibus, as well as the working temperatures. A broad optimization study has been carried out with the AMR model with the purpose of determining the design and working parameters of such a refrigerator that fulfil the cooling requirements of the vehicle with a minimum combined total system mass (affecting the weight of the vehicle and the economic cost) and electric consumption. The electric demand of the electrical AC auxiliaries has also been considered. Additionally, the heating performance of the optimal designs has been calculated. The application of AMR refrigerators in mobile air-conditioning systems is analyzed in comparison to the features of current vapor-compression systems.[ES] En la presente tesis doctoral se ha estudiado la aplicación de un refrigerador magnético en un sistema de aire acondicionado para automóviles. Con el fin de determinar las prestaciones de dicho sistema de manera global y precisa, se ha desarrollado un modelo térmico de cada uno de sus componentes. Por un lado, se ha desarrollado un modelo dinámico unidimensional de regenerador magnético activo (AMR) de placas planas paralelas, basado en un nuevo esquema numérico que reduce el tiempo de cálculo hasta en un 88% respecto al esquema más empleado. El modelo reproduce con gran exactitud los casos de regenerador con solución analítica y ha sido validado exhaustivamente con resultados experimentales funcionando como regenerador pasivo y como AMR. Para obtener buenos ajustes ha sido clave la inclusión en el modelo de las propiedades magnetocalóricas medidas experimentalmente con una muestra del material empleado, el efecto desmagnetizante, la mala distribución del fluido y las pérdidas hacia el ambiente del montaje experimental. La influencia de las incertidumbres y las simplificaciones en el modelado de estos fenómenos se ha analizado detalladamente, lo cual ha permitido validar diferentes aproximaciones. Por otro lado, se ha desarrollado un modelo dinámico del sistema de aire acondicionado de un vehículo eléctrico. Se incluye el modelo térmico de la cabina, los bucles hidráulicos para la distribución de la potencia térmica con los intercambiadores de calor agua-aire y los auxiliares eléctricos. La metodología empleada para el desarrollo de estos modelos, basada en la combinación de ecuaciones de conservación con el ajuste semi-empírico de los coeficientes globales de transmisión de calor, ha producido excelentes resultados de validación con resultados experimentales en un amplio rango de condiciones de funcionamiento. El modelo del vehículo se ha empleado para obtener la demanda de refrigeración y calefacción de un minibús eléctrico comercial, así como las temperaturas de funcionamiento del sistema. Con el modelo de AMR se ha llevado a cabo un amplio estudio de optimización para determinar los parámetros de diseño y de funcionamiento de dicho refrigerador que cubren las necesidades de refrigeración del vehículo una masa del conjunto del sistema y un consumo eléctrico mínimos, incluyendo el consumo de los auxiliares. Adicionalmente se han calculado las prestaciones de calefacción de las combinaciones óptimas. La aplicabilidad de este sistema en automóviles se analiza en comparación con un sistema equivalente de compresión de vapor.[CA] En aquesta tesi doctoral s'ha estudiat l'aplicació d'un refrigerador magnètic en un sistema d'aire condicionat per a automòbils. A fi de determinar les prestacions d'aquest sistema de manera global i precisa, s'ha desenvolupat un model tèrmic de cadascun dels components. D'una banda, s'ha desenvolupat un model dinàmic unidimensional de regenerador magnètic actiu (AMR) de plaques planes paral·leles, basat en un nou esquema numèric que redueix el temps de càlcul fins d'un 88% respecte a l'esquema més emprat. El model reprodueix amb gran exactitud els casos de regenerador amb solució analítica, i ha sigut validat exhaustivament amb resultats experimentals funcionant com a regenerador passiu i com a AMR. Per a obtenir bons ajustos ha sigut clau la inclusió en el model de les propietats magnetocalòriques mesurades experimentalment amb una mostra del material emprat, l'efecte desmagnetitzador, la mala distribució del fluid i les pèrdues cap a l'ambient del muntatge experimental. La influència de les incerteses i les simplificacions en la modelització d'aquests fenòmens s'ha analitzat detalladament, la qual cosa ha permès validar diferents aproximacions. D'altra banda, s'ha desenvolupat un model dinàmic del sistema d'aire condicionat d'un vehicle elèctric. S'hi inclouen el model tèrmic de la cabina, els bucles hidràulics per a la distribució de la potència tèrmica amb els bescanviadors de calor aigua-aire i els auxiliars elèctrics. La metodologia emprada per al desenvolupament d'aquests models, basada en la combinació d'equacions de conservació amb l'ajust semiempíric dels coeficients globals de transmissió de calor, ha produït excel·lents resultats de validació amb resultats experimentals en un ampli rang de condicions de funcionament. El model del vehicle s'ha emprat per a obtenir la demanda de refrigeració i calefacció d'un minibús elèctric comercial, així com les temperatures de funcionament del sistema. Amb el model d'AMR s'ha dut a terme un ampli estudi d'optimització per determinar els paràmetres de disseny i de funcionament de la refrigeradora esmentada que cobreixen les necessitats de refrigeració del vehicle, una massa del conjunt del sistema i un consum elèctric mínims, incloent el consum dels auxiliars. Addicionalment s'han calculat les prestacions de calefacció de les combinacions òptimes. L'aplicabilitat d'aquest sistema en automòbils s'analitza comparant-la amb la d'un sistema equivalent de compressió de vapor.Torregrosa Jaime, B. (2016). Modelling and analysis of an air-conditioning system for vehicles based on magnetocaloric refrigeration [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68503TESISPremios Extraordinarios de tesis doctorale

Analysis of the Operation of an Aerothermal Heat Pump in a Residential Building Using Building Information Modelling

Heating, cooling and domestic hot water (DHW) are responsible for the largest share of energy use in residential buildings in Spain and play an important role in the implementation of nearly zero-energy buildings (NZEB). Building Information Modelling (BIM) is expected to promote more efficient buildings through evaluation of different design options. BIM can be used as a platform from which to gather information that can be conveyed to energy efficiency simulation tools. The objective of this paper was to implement the model of a reversible air-to-water heat pump in EnergyPlus 8.9. This model was employed to analyze the performance of an aerothermal heat pump system (B) in a residential building under different Spanish climates compared to a conventional Heating, Ventilating and Air Conditioning (HVAC) system (A). Significant primary energy savings were achieved with system B compared to system A. These energy savings were higher in climates with a significant heating demand such as Madrid (27.4%) and Burgos (33.6%), and in cities with a mild climate such as Barcelona (37%). The residential building studied in this work was classified as Class A according to the CO2 emissions scale when using the aerothermal heat pump system, and as Class B when using the conventional HVAC system

Modelling of a Variable Refrigerant Flow System in EnergyPlus for Building Energy Simulation in an Open Building Information Modelling Environment

Variable refrigerant flow (VRF) systems are one possible tool to meet the objective that all new buildings must be nearly zero-energy buildings by 31 December 2020. Building Information Modelling (BIM) is a methodology that centralizes building construction project information in a digital model promoting collaboration between all its agents. The objectives of this work were to develop a more precise model of the VRF system than the one available in EnergyPlus version 8.9 (US Department of Energy) and to study the operation of this system in an office building under different climates by implementing the building energy simulation in an Open BIM workflow. The percentage deviation between the estimation of the VRF energy consumption with the standard and the new model was 6.91% and 1.59% for cooling and heating respectively in the case of Barcelona and 3.27% and 0.97% respectively in the case of Madrid. The energy performance class of the analysed building was A for each climatic zone. The primary energy consumption of the office building equipped with the VRF system was of 65.8 kWh/(m2·y) for the Mediterranean climate of Barcelona and 72.4 kWh/(m2·y) for the Continental climate of Madrid