The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform

José Luis Míguez - One of the best experts on this subject based on the ideXlab platform.

  • Numerical study of an external device for the improvement of the thermal stratification in hot water storage Tanks
    Applied Thermal Engineering, 2018
    Co-Authors: M.a. Gómez, J. Collazo, Jacobo Porteiro, José Luis Míguez
    Abstract:

    Abstract In this work, we study the operation of a water heater storage Tank using CFD modelling and analyse its limitations in order to propose a redesign that improves its characteristics. The study method is based on calculating the main variables that affect the thermal performance using the finite volume method. With this method, the Navier-Stokes equations are applied to calculate the internal movements of the fluid and its heat exchange with the coil. A determining factor for the operation of a water heater Tank is natural convection, which is solved by means of the Boussinesq approximation. Different reservoir simulations are carried out in continuous operation mode (stationary) and in heating mode (transient). In both cases, the results show very homogeneous heating, which means poor temperature stratification. As an alternative for improvement, a redesign of the system is proposed by means of an Auxiliary Tank where the heating coil is located, which injects the hot water, at different heights, into the main Tank. Several simulations of this redesign are carried out with different configurations in order to achieve better temperature stratification, reduce the heating time and maintain the outlet temperature of the domestic hot water (DHW) between 45 and 60 °C. As a result, the redesign significantly improves the stratification of temperatures and reduces the heating time necessary to obtain a DHW temperature of 45 °C from 45 to 8 min.

Publio Pintado - One of the best experts on this subject based on the ideXlab platform.

  • An adaptive pneumatic suspension system for improving ride comfort and handling
    Journal of Vibration and Control, 2014
    Co-Authors: A.j. Nieto, A.l. Morales, J.m. Chicharro, Publio Pintado
    Abstract:

    The paper describes an adaptive pneumatic suspension system that can improve both comfort and handling. Each air spring in the vehicle is connected to an Auxiliary Tank via two connecting pipes of different sizes. Choosing the connecting pipe with larger diameter and shorter length renders a compliant suspension which improves comfort. Conversely, choosing the connecting pipe with smaller diameter and longer length makes the suspension stiffer which favors handling. Toggling between configurations is fast, efficient, and easily done by simply opening or closing the corresponding electrovalves. The proposed adaptive system requires a GPS receiver and access to two pieces of information regarding the road at every location: the International Roughness Index and the curve radius (if not infinite). This information is used to predict road-induced vibrations and evaluate comfort with the ISO 2631 standard, as well as forecast roll angles and settling times for handling assessment. These predictions are used to...

  • An analytical model of pneumatic suspensions based on an experimental characterization
    Journal of Sound and Vibration, 2007
    Co-Authors: A.j. Nieto, A.l. Morales, A. González, J.m. Chicharro, Publio Pintado
    Abstract:

    We present an analytical model of air spring suspensions that is based on an experimental characterization. The suspension consists of three principal parts: the air spring, an Auxiliary Tank, and a pipe connecting the two. An analytical nonlinear fluid dynamics model is first analyzed, modeling the suspension stiffness, damping factor, and transmissibility. The model is then linearized and this linear version is studied in depth, finding that the behavior of the suspension as reflected in the aforementioned three characteristics is strongly dependent on the size of the three suspension parts. The analysis allows us to propose a practical strategy for the operation of the suspension.

David Chèze - One of the best experts on this subject based on the ideXlab platform.

  • Influence of mixing valve dynamics and recirculation loop connection to solar Tank on large hot water system performances
    Solar Energy, 2021
    Co-Authors: Arnaud Becq, David Chèze
    Abstract:

    A centralized solar domestic hot water system for a multi-family building is analyzed numerically. The solar preheated water in the solar Tank is flowing into an Auxiliary Tank, connected to a gas boiler. At its output, a mixing device is used to ensure hot water at steady temperature before going through the recirculation loop. This reference system is sized as a typical installation under mild climate in France. The load profile is generated statistically with a one-minute time step. Small time scale phenomena have consequences on the global system behavior: recirculation flow rate variations due to pressure drop change is modeled and validated experimentally. This work's goal is to analyze these effects on two sub-parts of the plant: mixing valve and recirculation loop connection to solar storage. In each case, yearly simulations with 6 s time step provide quantitative performance indicators for different sizing and control options. Results show that mixing valve slow response, due to ageing or bad design, leads to a loss of 3.5% energy savings compared to using a fast component. Furthermore, health risks increase as the minimal temperature in the recirculation loop is often under 50 • C, which promotes legionella development due to cold water plug flows generated in the loop by the mixing valve dynamic response. The recirculation loop, linked to a solar Tank, leads to performance improvement with 6-15% increase in energy savings following solar oversizing and reduced overheating risks.

Arkan Radi Ali - One of the best experts on this subject based on the ideXlab platform.

  • Electro-Hydrodynamic Design of an Intelligent Balloon Water Gate Controlled by an Efficient Maximum-Power-Seeking Controller for a Solar Generation System
    IEEE Access, 2019
    Co-Authors: Najah M. L. Al Maimuri, A.a.r Al Tahir, Farhan Lafta Rashid, Arkan Radi Ali
    Abstract:

    The intelligent balloon water gate (IBWG) invention is a hydraulic gate model made of reinforced plastic that controls the water level (WL) downstream or upstream of a barrage. The IBWG automatically inflates and deflates by compressed air to close and open the water passage, respectively. The whole design consists of a balloon, a waterway, sensors, an air compressor, a control panel, an electrical circuit and a photovoltaic generation (PVG) system. The Tyass barrage in Iraq was considered as a case study. The Tyass barrage was built with concrete and four sliding steel water gates and redesigned using the IBWG. The originality of the current research resides in the combination of the IBWG mechanism with an efficient maximum power point (MPP) seeking controller for a photovoltaic generation system, which is one of the most promising sources of renewable energy in the world. To the best of our knowledge, in this field, this scenario has not yet been discussed in detail. Upper and lower water sensors are used to control the IBWG. The upper sensor sends a signal to the control panel when the downstream water level reaches its maximum value to open the air inlet valve and close the outlet valve, inflating 14 IBWGs with a volume of 3.5 m3 under 122 psi of pressure and closing the water passage. When the WL decreases below the minimum level, the lower sensor initiates the opposite procedure. The air compressor automatically fills the air Tank to 181 psi and is supplied by a 24 VDC AGM rechargeable battery with a capacity of 40–60 Ah, which is charged by four solar panels connected in parallel and exposed to an average of 8.8 hrs/day of sunshine. The proposed MPP-seeking controller was implemented by a backstepping design coupled with the grey wolf mechanism. The solar irradiance data were observed 39 years ago. The proposed controller is capable of following the MPP with minimum oscillations under an external irradiance variation. The IBWG system is verified at night or during the early morning when the sun is not active. Nevertheless, it is possible to store compressed air in an Auxiliary Tank to avoid emergencies such as partial shading conditions.

Elamin A. Osman - One of the best experts on this subject based on the ideXlab platform.

  • Computer simulation of solar cooled buildings in Khartoum
    Renewable Energy, 1998
    Co-Authors: Elsheikh E. Magzoub, Elamin A. Osman
    Abstract:

    Abstract The transient state heat transfer formulation has been used to determine the air conditioning cooling load for two selected one room buildings in Khartoum: one made from brickwork and the other from wood. This formulation has been achieved by applying an explicit finite difference numerical techniques and adopting thermal network of electrical analogy to solve the transient conduction heat transfer equations. A computer program was developed to analyse the thermal network and to determine the cooling load for the wall, roof, window, ventilation and the total cooling load for each building for a typical hot summer day in Khartoum. A solar cooling system comprising mainly of a flat plate solar collector, a Lithium Bromide-Water absorption air conditioner, a storage and Auxiliary Tanks was integrated in the building and the energy equation for each component was obtained. A general simulation program for the solar cooled buildings has been developed and it was found that about 65% of the total cooling load demanded by the brick building could be supplied by energy from the solar collector, the other 35% portion had to be met by the Auxiliary Tank compared with 70% of the total cooling load demanded by the wood building which could be supplied by energy from the solar collector.