This paper presents a study on the use of ice to improve the energy efficiency of a domestic refrigerator by applying a pseudo bond graph model that describes the thermal transfers sustained by a quantity of ice introduced inside the cavity of refrigeration. The use of ice resulted in a global energy saving of 4.68%. The effect of ice was found to be more significant during the transitional regime. It reduced the response time to reach the stable average temperature from 15 h to only 3.5 h compared to when not using ice. This achievement did not cost additional electrical power, but rather allowed a saving of electrical energy of 76.73%. However, during the steady state, a reduction in the energy efficiency was noted. An improvement in the cooling by keeping the temperature inside the refrigerator more homogeneous is also proved. The model has two inputs: the outside temperature, and the modulated temperature of the evaporator. This latter determines the functioning of the compressor cycle. The model describes the thermal transfers by natural convection inside the refrigerator. Two experiments were carried out to make a performance comparison and to prove the influence of ice in cooling and energy saving. We used real measurements to modulate the evaporator temperature source in the pseudo bond graph model. The simulation results show the effectiveness of the proposed approach.
The paper presents a pseudo bond graph model of a thermo-hydraulic system which is composed by two warm and cold water pipes, a plastic tank and an evacuation pipe. This model is designed on 20sim software and it allows varying the temperature, inside the tank, by acting on the mass flows of the warm and cold water, as well as on the evacuation pipe. A simulation is done for constant and variable water mass flows to show the efficiency of this bond graph model.
The number of installations of Micro-Grid or intelligent micro power networks will increase to quadruple by 2020.The purpose is to reduce the cost and the consumption of electricity in transmission and distribution networks, using a hybrid system powered by solar and wind sources, as well as integrating storage devices. This paper reviews and discusses the MicroGrid Model. It describes various Micro-Grid components and different configurations. It also presents the model of two generation units (Photovoltaic and Wind Turbine). Then, a comparative study of different battery types used for large-scale electricity storage is carried out, followed by a review of control strategies.
In this paper, a robust fault diagnosis for a refrigerator compartment containing a quantity of ice using the bond graph (BG) approach is performed by linear fractional transformations (LFTs). The BG model describes heat transfers supported by the amount of ice placed in the refrigerator compartment, as well as a water container. The LFT modeling of BG elements offers advantages from the point of view of structural analysis and data processing implementation. We have introduced four faults, which consist of ice temperature rise, water leakage, insulation failure at the hot walls of the refrigerator and an increase of the internal temperature due to poor door sealing. The faults are in the form of additional heat fluxes. The simulation results show the effectiveness of the proposed method for detecting and localizing faults. In addition, the lack of door sealing has the most influence on the temperatures in the internal cooling space, water, and ice compared to the other faults.
In this paper, we propose an implementation of a synthesizable VHDL program of generalized predictive control (GPC) without constraints on a map XC3S700A Xilinx Starter Kit using the Xilinx ISE 10.1 software. The control strategy was applied to a second order state system. The VHDL language was used as a programming tool. Real variables were described with the fixed-point representation to overcome the overflow problems during the computations in the VHDL program. The use of FPGA circuits presents a good choice regarding to the problem of computation time encountered in predictive algorithms. A GPC Matlab program was also implemented in order to make a performance comparison. The simulation results show a good set-point tracking.Hp Hc c J J
This paper aims to prove the efficiency of using the free, abundant cold air flow stemming from the outside in high altitude to enhance the cooling inside a refrigeration cavity and to reduce the energy consumption. The cold air flow is spread out inside a cavity covering the side wall of the appliance and, which is connected to the inlet and outlet conducts. For that purpose, a Simulink model is proposed to model this installation. The internal temperature is computed according to the evaporator temperature and the outside cold air flow, which is also computed according to the outside temperature. The simulation results show that when the internal temperature is higher than the desired one and the outside temperature is low enough, the use of the controlled cold air flow as a second cooling source allowed to speed-up the cooling inside the refrigeration cavity of about 36.21% and to reach an energy saving of about 36.23% compared with the classical thermostatic control. When the internal temperature drops below the desired one, the appliance did not consume any energy.
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