This paper presents the simulation results of the thermal behavior for an externally cooled asynchronous electric motor in both steady and transient states cases. For this purpose, a mathematical model based on the heat equation is first developed to determine internal thermal sources such as copper, mechanical and iron losses. Then, a computer program is developed to numerically simulate the proposed mathematical model. This program determines the radial distribution of steady and transient states temperatures, and predicts the effect of the ambient temperature on the transient and permanent temperature distributions. This makes it possible to calculate the specific speed of the motor as a function of its rotation speed, the airflow rate and the pressure dropping at the fan level. The obtained results show that the engine heating is mainly due to the elements that show thermal losses by Joule effect. The mitigation of these losses is strictly related with the specific speed, which makes it possible to select the right choice of the engine cooling system. Using the nodal numerical method to determine the distribution of the radial temperature in both steady and transient states cases under the effect of the ambient temperature. The obtained results are analyzed and discussed.
Window solar air collector is an imperative instrument for heating residential buildings in cold regions. This paper presents a numerical investigation of the thermal performance of a window solar air collector with seven moveable absorber plates. With glass on the front and back sides of the collector. By the use of FORTRAN 90; The three-dimensional steady-state turbulent forced convection method was used to solve the Navier-Stokes equations. The seven plates opened and closed at different angles in unison manually by a specific mechanical mechanism. The effect of changing the plate angles has been tested, alongside the effect of airflow rates and the intensity of solar radiation. Numerical results illustrate that air temperature difference is higher at vertical plates position (angle 0) compared to that at angle 90. In contrast, flexibility between sunlight penetrating the room and hot air from the collector will be gained when the plates are set on angle 90. Results indicate that the thermal performance was improved by 67% when the plates were set at angle 0. Maximum thermal efficiency for angle 0 was 72% at a mass flow rate of 0.0298 kg/s. However, maximum thermal efficiency was 51% at mass flow rate 0.0298 for angle 90°.
This paper develops a unit commitment multi-period energy management system to minimize a low voltage microgrid's total operation and emission cost. The optimization problem is formulated in the mixed-integer quadratic program. The environment cost and battery degradation cost are taken into consideration in the proposed optimization approach. The unit commitment strategy is employed to minimize the total cost. A set of constraints are considered in the proposed optimization approach. The proposed energy management system is applied to the low voltage distribution grid, including different distributed generators, such as diesel engines, fuel cells, and microturbines. The microgrid also contains storage batteries, renewable energy resources, wind turbines, and photovoltaic panels. The results reveal that the storage battery charging and discharging operations are controlled to reduce the operation and emission cost even considering the battery degradation cost.
The present work aims to study the effects of working fluids on the thermal performance of the heat pipe with a wick and in a horizontal position. The experiments were conducted using a copper heat pipe with a 20.8 mm inner diameter, and the length of the evaporator, condenser, and the adiabatic regions were 300 mm, 350 mm, and 300 mm, respectively. The working fluids selected were water, Methanol, ethanol, and different binary mixtures (50: 50) %, (30: 70) %, (70: 30) % mixing ratios. The filling ratio was 50% of the evaporator volume for all working fluids, and the heat input values were 20, 30, 40, and 50 W. The results show that the heat pipe charged with Methanol has a thermal resistance of (0.85166o
C/W), the lowest thermal resistance value. The lowest thermal resistance of using mixtures is (0.785 o
C/W) for (50 % methanol: 50% ethanol). Both are achieved at 50 W heat input. Also, at 50 W heat input, the highest value of heat transfer coefficient when using water as a working fluid is (510.386 W/m2
C), and for using a mixture (70 % water: 30% methanol) is (556.78 W/m2